add letsencrypt to Gitea (#4189)

29 files changed, 4444 insertions, 278 deletions

diff --git a/vendor/golang.org/x/crypto/acme/acme.go b/vendor/golang.org/x/crypto/acme/acme.go
new file mode 100644
index 0000000000..1f4fb69edd
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/acme.go
@@ -0,0 +1,1065 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package acme provides an implementation of the
+// Automatic Certificate Management Environment (ACME) spec.
+// See https://tools.ietf.org/html/draft-ietf-acme-acme-02 for details.
+//
+// Most common scenarios will want to use autocert subdirectory instead,
+// which provides automatic access to certificates from Let's Encrypt
+// and any other ACME-based CA.
+//
+// This package is a work in progress and makes no API stability promises.
+package acme
+
+import (
+	"bytes"
+	"context"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math/big"
+	"net/http"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+// LetsEncryptURL is the Directory endpoint of Let's Encrypt CA.
+const LetsEncryptURL = "https://acme-v01.api.letsencrypt.org/directory"
+
+const (
+	maxChainLen = 5       // max depth and breadth of a certificate chain
+	maxCertSize = 1 << 20 // max size of a certificate, in bytes
+
+	// Max number of collected nonces kept in memory.
+	// Expect usual peak of 1 or 2.
+	maxNonces = 100
+)
+
+// Client is an ACME client.
+// The only required field is Key. An example of creating a client with a new key
+// is as follows:
+//
+// 	key, err := rsa.GenerateKey(rand.Reader, 2048)
+// 	if err != nil {
+// 		log.Fatal(err)
+// 	}
+// 	client := &Client{Key: key}
+//
+type Client struct {
+	// Key is the account key used to register with a CA and sign requests.
+	// Key.Public() must return a *rsa.PublicKey or *ecdsa.PublicKey.
+	Key crypto.Signer
+
+	// HTTPClient optionally specifies an HTTP client to use
+	// instead of http.DefaultClient.
+	HTTPClient *http.Client
+
+	// DirectoryURL points to the CA directory endpoint.
+	// If empty, LetsEncryptURL is used.
+	// Mutating this value after a successful call of Client's Discover method
+	// will have no effect.
+	DirectoryURL string
+
+	dirMu sync.Mutex // guards writes to dir
+	dir   *Directory // cached result of Client's Discover method
+
+	noncesMu sync.Mutex
+	nonces   map[string]struct{} // nonces collected from previous responses
+}
+
+// Discover performs ACME server discovery using c.DirectoryURL.
+//
+// It caches successful result. So, subsequent calls will not result in
+// a network round-trip. This also means mutating c.DirectoryURL after successful call
+// of this method will have no effect.
+func (c *Client) Discover(ctx context.Context) (Directory, error) {
+	c.dirMu.Lock()
+	defer c.dirMu.Unlock()
+	if c.dir != nil {
+		return *c.dir, nil
+	}
+
+	dirURL := c.DirectoryURL
+	if dirURL == "" {
+		dirURL = LetsEncryptURL
+	}
+	res, err := c.get(ctx, dirURL)
+	if err != nil {
+		return Directory{}, err
+	}
+	defer res.Body.Close()
+	c.addNonce(res.Header)
+	if res.StatusCode != http.StatusOK {
+		return Directory{}, responseError(res)
+	}
+
+	var v struct {
+		Reg    string `json:"new-reg"`
+		Authz  string `json:"new-authz"`
+		Cert   string `json:"new-cert"`
+		Revoke string `json:"revoke-cert"`
+		Meta   struct {
+			Terms   string   `json:"terms-of-service"`
+			Website string   `json:"website"`
+			CAA     []string `json:"caa-identities"`
+		}
+	}
+	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
+		return Directory{}, err
+	}
+	c.dir = &Directory{
+		RegURL:    v.Reg,
+		AuthzURL:  v.Authz,
+		CertURL:   v.Cert,
+		RevokeURL: v.Revoke,
+		Terms:     v.Meta.Terms,
+		Website:   v.Meta.Website,
+		CAA:       v.Meta.CAA,
+	}
+	return *c.dir, nil
+}
+
+// CreateCert requests a new certificate using the Certificate Signing Request csr encoded in DER format.
+// The exp argument indicates the desired certificate validity duration. CA may issue a certificate
+// with a different duration.
+// If the bundle argument is true, the returned value will also contain the CA (issuer) certificate chain.
+//
+// In the case where CA server does not provide the issued certificate in the response,
+// CreateCert will poll certURL using c.FetchCert, which will result in additional round-trips.
+// In such a scenario, the caller can cancel the polling with ctx.
+//
+// CreateCert returns an error if the CA's response or chain was unreasonably large.
+// Callers are encouraged to parse the returned value to ensure the certificate is valid and has the expected features.
+func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration, bundle bool) (der [][]byte, certURL string, err error) {
+	if _, err := c.Discover(ctx); err != nil {
+		return nil, "", err
+	}
+
+	req := struct {
+		Resource  string `json:"resource"`
+		CSR       string `json:"csr"`
+		NotBefore string `json:"notBefore,omitempty"`
+		NotAfter  string `json:"notAfter,omitempty"`
+	}{
+		Resource: "new-cert",
+		CSR:      base64.RawURLEncoding.EncodeToString(csr),
+	}
+	now := timeNow()
+	req.NotBefore = now.Format(time.RFC3339)
+	if exp > 0 {
+		req.NotAfter = now.Add(exp).Format(time.RFC3339)
+	}
+
+	res, err := c.retryPostJWS(ctx, c.Key, c.dir.CertURL, req)
+	if err != nil {
+		return nil, "", err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusCreated {
+		return nil, "", responseError(res)
+	}
+
+	curl := res.Header.Get("Location") // cert permanent URL
+	if res.ContentLength == 0 {
+		// no cert in the body; poll until we get it
+		cert, err := c.FetchCert(ctx, curl, bundle)
+		return cert, curl, err
+	}
+	// slurp issued cert and CA chain, if requested
+	cert, err := c.responseCert(ctx, res, bundle)
+	return cert, curl, err
+}
+
+// FetchCert retrieves already issued certificate from the given url, in DER format.
+// It retries the request until the certificate is successfully retrieved,
+// context is cancelled by the caller or an error response is received.
+//
+// The returned value will also contain the CA (issuer) certificate if the bundle argument is true.
+//
+// FetchCert returns an error if the CA's response or chain was unreasonably large.
+// Callers are encouraged to parse the returned value to ensure the certificate is valid
+// and has expected features.
+func (c *Client) FetchCert(ctx context.Context, url string, bundle bool) ([][]byte, error) {
+	for {
+		res, err := c.get(ctx, url)
+		if err != nil {
+			return nil, err
+		}
+		defer res.Body.Close()
+		if res.StatusCode == http.StatusOK {
+			return c.responseCert(ctx, res, bundle)
+		}
+		if res.StatusCode > 299 {
+			return nil, responseError(res)
+		}
+		d := retryAfter(res.Header.Get("Retry-After"), 3*time.Second)
+		select {
+		case <-time.After(d):
+			// retry
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+	}
+}
+
+// RevokeCert revokes a previously issued certificate cert, provided in DER format.
+//
+// The key argument, used to sign the request, must be authorized
+// to revoke the certificate. It's up to the CA to decide which keys are authorized.
+// For instance, the key pair of the certificate may be authorized.
+// If the key is nil, c.Key is used instead.
+func (c *Client) RevokeCert(ctx context.Context, key crypto.Signer, cert []byte, reason CRLReasonCode) error {
+	if _, err := c.Discover(ctx); err != nil {
+		return err
+	}
+
+	body := &struct {
+		Resource string `json:"resource"`
+		Cert     string `json:"certificate"`
+		Reason   int    `json:"reason"`
+	}{
+		Resource: "revoke-cert",
+		Cert:     base64.RawURLEncoding.EncodeToString(cert),
+		Reason:   int(reason),
+	}
+	if key == nil {
+		key = c.Key
+	}
+	res, err := c.retryPostJWS(ctx, key, c.dir.RevokeURL, body)
+	if err != nil {
+		return err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return responseError(res)
+	}
+	return nil
+}
+
+// AcceptTOS always returns true to indicate the acceptance of a CA's Terms of Service
+// during account registration. See Register method of Client for more details.
+func AcceptTOS(tosURL string) bool { return true }
+
+// Register creates a new account registration by following the "new-reg" flow.
+// It returns the registered account. The account is not modified.
+//
+// The registration may require the caller to agree to the CA's Terms of Service (TOS).
+// If so, and the account has not indicated the acceptance of the terms (see Account for details),
+// Register calls prompt with a TOS URL provided by the CA. Prompt should report
+// whether the caller agrees to the terms. To always accept the terms, the caller can use AcceptTOS.
+func (c *Client) Register(ctx context.Context, a *Account, prompt func(tosURL string) bool) (*Account, error) {
+	if _, err := c.Discover(ctx); err != nil {
+		return nil, err
+	}
+
+	var err error
+	if a, err = c.doReg(ctx, c.dir.RegURL, "new-reg", a); err != nil {
+		return nil, err
+	}
+	var accept bool
+	if a.CurrentTerms != "" && a.CurrentTerms != a.AgreedTerms {
+		accept = prompt(a.CurrentTerms)
+	}
+	if accept {
+		a.AgreedTerms = a.CurrentTerms
+		a, err = c.UpdateReg(ctx, a)
+	}
+	return a, err
+}
+
+// GetReg retrieves an existing registration.
+// The url argument is an Account URI.
+func (c *Client) GetReg(ctx context.Context, url string) (*Account, error) {
+	a, err := c.doReg(ctx, url, "reg", nil)
+	if err != nil {
+		return nil, err
+	}
+	a.URI = url
+	return a, nil
+}
+
+// UpdateReg updates an existing registration.
+// It returns an updated account copy. The provided account is not modified.
+func (c *Client) UpdateReg(ctx context.Context, a *Account) (*Account, error) {
+	uri := a.URI
+	a, err := c.doReg(ctx, uri, "reg", a)
+	if err != nil {
+		return nil, err
+	}
+	a.URI = uri
+	return a, nil
+}
+
+// Authorize performs the initial step in an authorization flow.
+// The caller will then need to choose from and perform a set of returned
+// challenges using c.Accept in order to successfully complete authorization.
+//
+// If an authorization has been previously granted, the CA may return
+// a valid authorization (Authorization.Status is StatusValid). If so, the caller
+// need not fulfill any challenge and can proceed to requesting a certificate.
+func (c *Client) Authorize(ctx context.Context, domain string) (*Authorization, error) {
+	if _, err := c.Discover(ctx); err != nil {
+		return nil, err
+	}
+
+	type authzID struct {
+		Type  string `json:"type"`
+		Value string `json:"value"`
+	}
+	req := struct {
+		Resource   string  `json:"resource"`
+		Identifier authzID `json:"identifier"`
+	}{
+		Resource:   "new-authz",
+		Identifier: authzID{Type: "dns", Value: domain},
+	}
+	res, err := c.retryPostJWS(ctx, c.Key, c.dir.AuthzURL, req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusCreated {
+		return nil, responseError(res)
+	}
+
+	var v wireAuthz
+	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
+		return nil, fmt.Errorf("acme: invalid response: %v", err)
+	}
+	if v.Status != StatusPending && v.Status != StatusValid {
+		return nil, fmt.Errorf("acme: unexpected status: %s", v.Status)
+	}
+	return v.authorization(res.Header.Get("Location")), nil
+}
+
+// GetAuthorization retrieves an authorization identified by the given URL.
+//
+// If a caller needs to poll an authorization until its status is final,
+// see the WaitAuthorization method.
+func (c *Client) GetAuthorization(ctx context.Context, url string) (*Authorization, error) {
+	res, err := c.get(ctx, url)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
+		return nil, responseError(res)
+	}
+	var v wireAuthz
+	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
+		return nil, fmt.Errorf("acme: invalid response: %v", err)
+	}
+	return v.authorization(url), nil
+}
+
+// RevokeAuthorization relinquishes an existing authorization identified
+// by the given URL.
+// The url argument is an Authorization.URI value.
+//
+// If successful, the caller will be required to obtain a new authorization
+// using the Authorize method before being able to request a new certificate
+// for the domain associated with the authorization.
+//
+// It does not revoke existing certificates.
+func (c *Client) RevokeAuthorization(ctx context.Context, url string) error {
+	req := struct {
+		Resource string `json:"resource"`
+		Status   string `json:"status"`
+		Delete   bool   `json:"delete"`
+	}{
+		Resource: "authz",
+		Status:   "deactivated",
+		Delete:   true,
+	}
+	res, err := c.retryPostJWS(ctx, c.Key, url, req)
+	if err != nil {
+		return err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return responseError(res)
+	}
+	return nil
+}
+
+// WaitAuthorization polls an authorization at the given URL
+// until it is in one of the final states, StatusValid or StatusInvalid,
+// the ACME CA responded with a 4xx error code, or the context is done.
+//
+// It returns a non-nil Authorization only if its Status is StatusValid.
+// In all other cases WaitAuthorization returns an error.
+// If the Status is StatusInvalid, the returned error is of type *AuthorizationError.
+func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorization, error) {
+	sleep := sleeper(ctx)
+	for {
+		res, err := c.get(ctx, url)
+		if err != nil {
+			return nil, err
+		}
+		if res.StatusCode >= 400 && res.StatusCode <= 499 {
+			// Non-retriable error. For instance, Let's Encrypt may return 404 Not Found
+			// when requesting an expired authorization.
+			defer res.Body.Close()
+			return nil, responseError(res)
+		}
+
+		retry := res.Header.Get("Retry-After")
+		if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
+			res.Body.Close()
+			if err := sleep(retry, 1); err != nil {
+				return nil, err
+			}
+			continue
+		}
+		var raw wireAuthz
+		err = json.NewDecoder(res.Body).Decode(&raw)
+		res.Body.Close()
+		if err != nil {
+			if err := sleep(retry, 0); err != nil {
+				return nil, err
+			}
+			continue
+		}
+		if raw.Status == StatusValid {
+			return raw.authorization(url), nil
+		}
+		if raw.Status == StatusInvalid {
+			return nil, raw.error(url)
+		}
+		if err := sleep(retry, 0); err != nil {
+			return nil, err
+		}
+	}
+}
+
+// GetChallenge retrieves the current status of an challenge.
+//
+// A client typically polls a challenge status using this method.
+func (c *Client) GetChallenge(ctx context.Context, url string) (*Challenge, error) {
+	res, err := c.get(ctx, url)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
+		return nil, responseError(res)
+	}
+	v := wireChallenge{URI: url}
+	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
+		return nil, fmt.Errorf("acme: invalid response: %v", err)
+	}
+	return v.challenge(), nil
+}
+
+// Accept informs the server that the client accepts one of its challenges
+// previously obtained with c.Authorize.
+//
+// The server will then perform the validation asynchronously.
+func (c *Client) Accept(ctx context.Context, chal *Challenge) (*Challenge, error) {
+	auth, err := keyAuth(c.Key.Public(), chal.Token)
+	if err != nil {
+		return nil, err
+	}
+
+	req := struct {
+		Resource string `json:"resource"`
+		Type     string `json:"type"`
+		Auth     string `json:"keyAuthorization"`
+	}{
+		Resource: "challenge",
+		Type:     chal.Type,
+		Auth:     auth,
+	}
+	res, err := c.retryPostJWS(ctx, c.Key, chal.URI, req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	// Note: the protocol specifies 200 as the expected response code, but
+	// letsencrypt seems to be returning 202.
+	if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
+		return nil, responseError(res)
+	}
+
+	var v wireChallenge
+	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
+		return nil, fmt.Errorf("acme: invalid response: %v", err)
+	}
+	return v.challenge(), nil
+}
+
+// DNS01ChallengeRecord returns a DNS record value for a dns-01 challenge response.
+// A TXT record containing the returned value must be provisioned under
+// "_acme-challenge" name of the domain being validated.
+//
+// The token argument is a Challenge.Token value.
+func (c *Client) DNS01ChallengeRecord(token string) (string, error) {
+	ka, err := keyAuth(c.Key.Public(), token)
+	if err != nil {
+		return "", err
+	}
+	b := sha256.Sum256([]byte(ka))
+	return base64.RawURLEncoding.EncodeToString(b[:]), nil
+}
+
+// HTTP01ChallengeResponse returns the response for an http-01 challenge.
+// Servers should respond with the value to HTTP requests at the URL path
+// provided by HTTP01ChallengePath to validate the challenge and prove control
+// over a domain name.
+//
+// The token argument is a Challenge.Token value.
+func (c *Client) HTTP01ChallengeResponse(token string) (string, error) {
+	return keyAuth(c.Key.Public(), token)
+}
+
+// HTTP01ChallengePath returns the URL path at which the response for an http-01 challenge
+// should be provided by the servers.
+// The response value can be obtained with HTTP01ChallengeResponse.
+//
+// The token argument is a Challenge.Token value.
+func (c *Client) HTTP01ChallengePath(token string) string {
+	return "/.well-known/acme-challenge/" + token
+}
+
+// TLSSNI01ChallengeCert creates a certificate for TLS-SNI-01 challenge response.
+// Servers can present the certificate to validate the challenge and prove control
+// over a domain name.
+//
+// The implementation is incomplete in that the returned value is a single certificate,
+// computed only for Z0 of the key authorization. ACME CAs are expected to update
+// their implementations to use the newer version, TLS-SNI-02.
+// For more details on TLS-SNI-01 see https://tools.ietf.org/html/draft-ietf-acme-acme-01#section-7.3.
+//
+// The token argument is a Challenge.Token value.
+// If a WithKey option is provided, its private part signs the returned cert,
+// and the public part is used to specify the signee.
+// If no WithKey option is provided, a new ECDSA key is generated using P-256 curve.
+//
+// The returned certificate is valid for the next 24 hours and must be presented only when
+// the server name of the client hello matches exactly the returned name value.
+func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
+	ka, err := keyAuth(c.Key.Public(), token)
+	if err != nil {
+		return tls.Certificate{}, "", err
+	}
+	b := sha256.Sum256([]byte(ka))
+	h := hex.EncodeToString(b[:])
+	name = fmt.Sprintf("%s.%s.acme.invalid", h[:32], h[32:])
+	cert, err = tlsChallengeCert([]string{name}, opt)
+	if err != nil {
+		return tls.Certificate{}, "", err
+	}
+	return cert, name, nil
+}
+
+// TLSSNI02ChallengeCert creates a certificate for TLS-SNI-02 challenge response.
+// Servers can present the certificate to validate the challenge and prove control
+// over a domain name. For more details on TLS-SNI-02 see
+// https://tools.ietf.org/html/draft-ietf-acme-acme-03#section-7.3.
+//
+// The token argument is a Challenge.Token value.
+// If a WithKey option is provided, its private part signs the returned cert,
+// and the public part is used to specify the signee.
+// If no WithKey option is provided, a new ECDSA key is generated using P-256 curve.
+//
+// The returned certificate is valid for the next 24 hours and must be presented only when
+// the server name in the client hello matches exactly the returned name value.
+func (c *Client) TLSSNI02ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
+	b := sha256.Sum256([]byte(token))
+	h := hex.EncodeToString(b[:])
+	sanA := fmt.Sprintf("%s.%s.token.acme.invalid", h[:32], h[32:])
+
+	ka, err := keyAuth(c.Key.Public(), token)
+	if err != nil {
+		return tls.Certificate{}, "", err
+	}
+	b = sha256.Sum256([]byte(ka))
+	h = hex.EncodeToString(b[:])
+	sanB := fmt.Sprintf("%s.%s.ka.acme.invalid", h[:32], h[32:])
+
+	cert, err = tlsChallengeCert([]string{sanA, sanB}, opt)
+	if err != nil {
+		return tls.Certificate{}, "", err
+	}
+	return cert, sanA, nil
+}
+
+// doReg sends all types of registration requests.
+// The type of request is identified by typ argument, which is a "resource"
+// in the ACME spec terms.
+//
+// A non-nil acct argument indicates whether the intention is to mutate data
+// of the Account. Only Contact and Agreement of its fields are used
+// in such cases.
+func (c *Client) doReg(ctx context.Context, url string, typ string, acct *Account) (*Account, error) {
+	req := struct {
+		Resource  string   `json:"resource"`
+		Contact   []string `json:"contact,omitempty"`
+		Agreement string   `json:"agreement,omitempty"`
+	}{
+		Resource: typ,
+	}
+	if acct != nil {
+		req.Contact = acct.Contact
+		req.Agreement = acct.AgreedTerms
+	}
+	res, err := c.retryPostJWS(ctx, c.Key, url, req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode < 200 || res.StatusCode > 299 {
+		return nil, responseError(res)
+	}
+
+	var v struct {
+		Contact        []string
+		Agreement      string
+		Authorizations string
+		Certificates   string
+	}
+	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
+		return nil, fmt.Errorf("acme: invalid response: %v", err)
+	}
+	var tos string
+	if v := linkHeader(res.Header, "terms-of-service"); len(v) > 0 {
+		tos = v[0]
+	}
+	var authz string
+	if v := linkHeader(res.Header, "next"); len(v) > 0 {
+		authz = v[0]
+	}
+	return &Account{
+		URI:            res.Header.Get("Location"),
+		Contact:        v.Contact,
+		AgreedTerms:    v.Agreement,
+		CurrentTerms:   tos,
+		Authz:          authz,
+		Authorizations: v.Authorizations,
+		Certificates:   v.Certificates,
+	}, nil
+}
+
+// retryPostJWS will retry calls to postJWS if there is a badNonce error,
+// clearing the stored nonces after each error.
+// If the response was 4XX-5XX, then responseError is called on the body,
+// the body is closed, and the error returned.
+func (c *Client) retryPostJWS(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, error) {
+	sleep := sleeper(ctx)
+	for {
+		res, err := c.postJWS(ctx, key, url, body)
+		if err != nil {
+			return nil, err
+		}
+		// handle errors 4XX-5XX with responseError
+		if res.StatusCode >= 400 && res.StatusCode <= 599 {
+			err := responseError(res)
+			res.Body.Close()
+			// according to spec badNonce is urn:ietf:params:acme:error:badNonce
+			// however, acme servers in the wild return their version of the error
+			// https://tools.ietf.org/html/draft-ietf-acme-acme-02#section-5.4
+			if ae, ok := err.(*Error); ok && strings.HasSuffix(strings.ToLower(ae.ProblemType), ":badnonce") {
+				// clear any nonces that we might've stored that might now be
+				// considered bad
+				c.clearNonces()
+				retry := res.Header.Get("Retry-After")
+				if err := sleep(retry, 1); err != nil {
+					return nil, err
+				}
+				continue
+			}
+			return nil, err
+		}
+		return res, nil
+	}
+}
+
+// postJWS signs the body with the given key and POSTs it to the provided url.
+// The body argument must be JSON-serializable.
+func (c *Client) postJWS(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, error) {
+	nonce, err := c.popNonce(ctx, url)
+	if err != nil {
+		return nil, err
+	}
+	b, err := jwsEncodeJSON(body, key, nonce)
+	if err != nil {
+		return nil, err
+	}
+	res, err := c.post(ctx, url, "application/jose+json", bytes.NewReader(b))
+	if err != nil {
+		return nil, err
+	}
+	c.addNonce(res.Header)
+	return res, nil
+}
+
+// popNonce returns a nonce value previously stored with c.addNonce
+// or fetches a fresh one from the given URL.
+func (c *Client) popNonce(ctx context.Context, url string) (string, error) {
+	c.noncesMu.Lock()
+	defer c.noncesMu.Unlock()
+	if len(c.nonces) == 0 {
+		return c.fetchNonce(ctx, url)
+	}
+	var nonce string
+	for nonce = range c.nonces {
+		delete(c.nonces, nonce)
+		break
+	}
+	return nonce, nil
+}
+
+// clearNonces clears any stored nonces
+func (c *Client) clearNonces() {
+	c.noncesMu.Lock()
+	defer c.noncesMu.Unlock()
+	c.nonces = make(map[string]struct{})
+}
+
+// addNonce stores a nonce value found in h (if any) for future use.
+func (c *Client) addNonce(h http.Header) {
+	v := nonceFromHeader(h)
+	if v == "" {
+		return
+	}
+	c.noncesMu.Lock()
+	defer c.noncesMu.Unlock()
+	if len(c.nonces) >= maxNonces {
+		return
+	}
+	if c.nonces == nil {
+		c.nonces = make(map[string]struct{})
+	}
+	c.nonces[v] = struct{}{}
+}
+
+func (c *Client) httpClient() *http.Client {
+	if c.HTTPClient != nil {
+		return c.HTTPClient
+	}
+	return http.DefaultClient
+}
+
+func (c *Client) get(ctx context.Context, urlStr string) (*http.Response, error) {
+	req, err := http.NewRequest("GET", urlStr, nil)
+	if err != nil {
+		return nil, err
+	}
+	return c.do(ctx, req)
+}
+
+func (c *Client) head(ctx context.Context, urlStr string) (*http.Response, error) {
+	req, err := http.NewRequest("HEAD", urlStr, nil)
+	if err != nil {
+		return nil, err
+	}
+	return c.do(ctx, req)
+}
+
+func (c *Client) post(ctx context.Context, urlStr, contentType string, body io.Reader) (*http.Response, error) {
+	req, err := http.NewRequest("POST", urlStr, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", contentType)
+	return c.do(ctx, req)
+}
+
+func (c *Client) do(ctx context.Context, req *http.Request) (*http.Response, error) {
+	res, err := c.httpClient().Do(req.WithContext(ctx))
+	if err != nil {
+		select {
+		case <-ctx.Done():
+			// Prefer the unadorned context error.
+			// (The acme package had tests assuming this, previously from ctxhttp's
+			// behavior, predating net/http supporting contexts natively)
+			// TODO(bradfitz): reconsider this in the future. But for now this
+			// requires no test updates.
+			return nil, ctx.Err()
+		default:
+			return nil, err
+		}
+	}
+	return res, nil
+}
+
+func (c *Client) fetchNonce(ctx context.Context, url string) (string, error) {
+	resp, err := c.head(ctx, url)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	nonce := nonceFromHeader(resp.Header)
+	if nonce == "" {
+		if resp.StatusCode > 299 {
+			return "", responseError(resp)
+		}
+		return "", errors.New("acme: nonce not found")
+	}
+	return nonce, nil
+}
+
+func nonceFromHeader(h http.Header) string {
+	return h.Get("Replay-Nonce")
+}
+
+func (c *Client) responseCert(ctx context.Context, res *http.Response, bundle bool) ([][]byte, error) {
+	b, err := ioutil.ReadAll(io.LimitReader(res.Body, maxCertSize+1))
+	if err != nil {
+		return nil, fmt.Errorf("acme: response stream: %v", err)
+	}
+	if len(b) > maxCertSize {
+		return nil, errors.New("acme: certificate is too big")
+	}
+	cert := [][]byte{b}
+	if !bundle {
+		return cert, nil
+	}
+
+	// Append CA chain cert(s).
+	// At least one is required according to the spec:
+	// https://tools.ietf.org/html/draft-ietf-acme-acme-03#section-6.3.1
+	up := linkHeader(res.Header, "up")
+	if len(up) == 0 {
+		return nil, errors.New("acme: rel=up link not found")
+	}
+	if len(up) > maxChainLen {
+		return nil, errors.New("acme: rel=up link is too large")
+	}
+	for _, url := range up {
+		cc, err := c.chainCert(ctx, url, 0)
+		if err != nil {
+			return nil, err
+		}
+		cert = append(cert, cc...)
+	}
+	return cert, nil
+}
+
+// responseError creates an error of Error type from resp.
+func responseError(resp *http.Response) error {
+	// don't care if ReadAll returns an error:
+	// json.Unmarshal will fail in that case anyway
+	b, _ := ioutil.ReadAll(resp.Body)
+	e := &wireError{Status: resp.StatusCode}
+	if err := json.Unmarshal(b, e); err != nil {
+		// this is not a regular error response:
+		// populate detail with anything we received,
+		// e.Status will already contain HTTP response code value
+		e.Detail = string(b)
+		if e.Detail == "" {
+			e.Detail = resp.Status
+		}
+	}
+	return e.error(resp.Header)
+}
+
+// chainCert fetches CA certificate chain recursively by following "up" links.
+// Each recursive call increments the depth by 1, resulting in an error
+// if the recursion level reaches maxChainLen.
+//
+// First chainCert call starts with depth of 0.
+func (c *Client) chainCert(ctx context.Context, url string, depth int) ([][]byte, error) {
+	if depth >= maxChainLen {
+		return nil, errors.New("acme: certificate chain is too deep")
+	}
+
+	res, err := c.get(ctx, url)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return nil, responseError(res)
+	}
+	b, err := ioutil.ReadAll(io.LimitReader(res.Body, maxCertSize+1))
+	if err != nil {
+		return nil, err
+	}
+	if len(b) > maxCertSize {
+		return nil, errors.New("acme: certificate is too big")
+	}
+	chain := [][]byte{b}
+
+	uplink := linkHeader(res.Header, "up")
+	if len(uplink) > maxChainLen {
+		return nil, errors.New("acme: certificate chain is too large")
+	}
+	for _, up := range uplink {
+		cc, err := c.chainCert(ctx, up, depth+1)
+		if err != nil {
+			return nil, err
+		}
+		chain = append(chain, cc...)
+	}
+
+	return chain, nil
+}
+
+// linkHeader returns URI-Reference values of all Link headers
+// with relation-type rel.
+// See https://tools.ietf.org/html/rfc5988#section-5 for details.
+func linkHeader(h http.Header, rel string) []string {
+	var links []string
+	for _, v := range h["Link"] {
+		parts := strings.Split(v, ";")
+		for _, p := range parts {
+			p = strings.TrimSpace(p)
+			if !strings.HasPrefix(p, "rel=") {
+				continue
+			}
+			if v := strings.Trim(p[4:], `"`); v == rel {
+				links = append(links, strings.Trim(parts[0], "<>"))
+			}
+		}
+	}
+	return links
+}
+
+// sleeper returns a function that accepts the Retry-After HTTP header value
+// and an increment that's used with backoff to increasingly sleep on
+// consecutive calls until the context is done. If the Retry-After header
+// cannot be parsed, then backoff is used with a maximum sleep time of 10
+// seconds.
+func sleeper(ctx context.Context) func(ra string, inc int) error {
+	var count int
+	return func(ra string, inc int) error {
+		count += inc
+		d := backoff(count, 10*time.Second)
+		d = retryAfter(ra, d)
+		wakeup := time.NewTimer(d)
+		defer wakeup.Stop()
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-wakeup.C:
+			return nil
+		}
+	}
+}
+
+// retryAfter parses a Retry-After HTTP header value,
+// trying to convert v into an int (seconds) or use http.ParseTime otherwise.
+// It returns d if v cannot be parsed.
+func retryAfter(v string, d time.Duration) time.Duration {
+	if i, err := strconv.Atoi(v); err == nil {
+		return time.Duration(i) * time.Second
+	}
+	t, err := http.ParseTime(v)
+	if err != nil {
+		return d
+	}
+	return t.Sub(timeNow())
+}
+
+// backoff computes a duration after which an n+1 retry iteration should occur
+// using truncated exponential backoff algorithm.
+//
+// The n argument is always bounded between 0 and 30.
+// The max argument defines upper bound for the returned value.
+func backoff(n int, max time.Duration) time.Duration {
+	if n < 0 {
+		n = 0
+	}
+	if n > 30 {
+		n = 30
+	}
+	var d time.Duration
+	if x, err := rand.Int(rand.Reader, big.NewInt(1000)); err == nil {
+		d = time.Duration(x.Int64()) * time.Millisecond
+	}
+	d += time.Duration(1<<uint(n)) * time.Second
+	if d > max {
+		return max
+	}
+	return d
+}
+
+// keyAuth generates a key authorization string for a given token.
+func keyAuth(pub crypto.PublicKey, token string) (string, error) {
+	th, err := JWKThumbprint(pub)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s.%s", token, th), nil
+}
+
+// tlsChallengeCert creates a temporary certificate for TLS-SNI challenges
+// with the given SANs and auto-generated public/private key pair.
+// The Subject Common Name is set to the first SAN to aid debugging.
+// To create a cert with a custom key pair, specify WithKey option.
+func tlsChallengeCert(san []string, opt []CertOption) (tls.Certificate, error) {
+	var (
+		key  crypto.Signer
+		tmpl *x509.Certificate
+	)
+	for _, o := range opt {
+		switch o := o.(type) {
+		case *certOptKey:
+			if key != nil {
+				return tls.Certificate{}, errors.New("acme: duplicate key option")
+			}
+			key = o.key
+		case *certOptTemplate:
+			var t = *(*x509.Certificate)(o) // shallow copy is ok
+			tmpl = &t
+		default:
+			// package's fault, if we let this happen:
+			panic(fmt.Sprintf("unsupported option type %T", o))
+		}
+	}
+	if key == nil {
+		var err error
+		if key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader); err != nil {
+			return tls.Certificate{}, err
+		}
+	}
+	if tmpl == nil {
+		tmpl = &x509.Certificate{
+			SerialNumber:          big.NewInt(1),
+			NotBefore:             time.Now(),
+			NotAfter:              time.Now().Add(24 * time.Hour),
+			BasicConstraintsValid: true,
+			KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+			ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		}
+	}
+	tmpl.DNSNames = san
+	if len(san) > 0 {
+		tmpl.Subject.CommonName = san[0]
+	}
+
+	der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, key.Public(), key)
+	if err != nil {
+		return tls.Certificate{}, err
+	}
+	return tls.Certificate{
+		Certificate: [][]byte{der},
+		PrivateKey:  key,
+	}, nil
+}
+
+// encodePEM returns b encoded as PEM with block of type typ.
+func encodePEM(typ string, b []byte) []byte {
+	pb := &pem.Block{Type: typ, Bytes: b}
+	return pem.EncodeToMemory(pb)
+}
+
+// timeNow is useful for testing for fixed current time.
+var timeNow = time.Now
diff --git a/vendor/golang.org/x/crypto/acme/autocert/autocert.go b/vendor/golang.org/x/crypto/acme/autocert/autocert.go
new file mode 100644
index 0000000000..263b291331
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/autocert/autocert.go
@@ -0,0 +1,962 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package autocert provides automatic access to certificates from Let's Encrypt
+// and any other ACME-based CA.
+//
+// This package is a work in progress and makes no API stability promises.
+package autocert
+
+import (
+	"bytes"
+	"context"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io"
+	mathrand "math/rand"
+	"net"
+	"net/http"
+	"path"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/crypto/acme"
+)
+
+// createCertRetryAfter is how much time to wait before removing a failed state
+// entry due to an unsuccessful createCert call.
+// This is a variable instead of a const for testing.
+// TODO: Consider making it configurable or an exp backoff?
+var createCertRetryAfter = time.Minute
+
+// pseudoRand is safe for concurrent use.
+var pseudoRand *lockedMathRand
+
+func init() {
+	src := mathrand.NewSource(timeNow().UnixNano())
+	pseudoRand = &lockedMathRand{rnd: mathrand.New(src)}
+}
+
+// AcceptTOS is a Manager.Prompt function that always returns true to
+// indicate acceptance of the CA's Terms of Service during account
+// registration.
+func AcceptTOS(tosURL string) bool { return true }
+
+// HostPolicy specifies which host names the Manager is allowed to respond to.
+// It returns a non-nil error if the host should be rejected.
+// The returned error is accessible via tls.Conn.Handshake and its callers.
+// See Manager's HostPolicy field and GetCertificate method docs for more details.
+type HostPolicy func(ctx context.Context, host string) error
+
+// HostWhitelist returns a policy where only the specified host names are allowed.
+// Only exact matches are currently supported. Subdomains, regexp or wildcard
+// will not match.
+func HostWhitelist(hosts ...string) HostPolicy {
+	whitelist := make(map[string]bool, len(hosts))
+	for _, h := range hosts {
+		whitelist[h] = true
+	}
+	return func(_ context.Context, host string) error {
+		if !whitelist[host] {
+			return errors.New("acme/autocert: host not configured")
+		}
+		return nil
+	}
+}
+
+// defaultHostPolicy is used when Manager.HostPolicy is not set.
+func defaultHostPolicy(context.Context, string) error {
+	return nil
+}
+
+// Manager is a stateful certificate manager built on top of acme.Client.
+// It obtains and refreshes certificates automatically using "tls-sni-01",
+// "tls-sni-02" and "http-01" challenge types, as well as providing them
+// to a TLS server via tls.Config.
+//
+// You must specify a cache implementation, such as DirCache,
+// to reuse obtained certificates across program restarts.
+// Otherwise your server is very likely to exceed the certificate
+// issuer's request rate limits.
+type Manager struct {
+	// Prompt specifies a callback function to conditionally accept a CA's Terms of Service (TOS).
+	// The registration may require the caller to agree to the CA's TOS.
+	// If so, Manager calls Prompt with a TOS URL provided by the CA. Prompt should report
+	// whether the caller agrees to the terms.
+	//
+	// To always accept the terms, the callers can use AcceptTOS.
+	Prompt func(tosURL string) bool
+
+	// Cache optionally stores and retrieves previously-obtained certificates.
+	// If nil, certs will only be cached for the lifetime of the Manager.
+	//
+	// Manager passes the Cache certificates data encoded in PEM, with private/public
+	// parts combined in a single Cache.Put call, private key first.
+	Cache Cache
+
+	// HostPolicy controls which domains the Manager will attempt
+	// to retrieve new certificates for. It does not affect cached certs.
+	//
+	// If non-nil, HostPolicy is called before requesting a new cert.
+	// If nil, all hosts are currently allowed. This is not recommended,
+	// as it opens a potential attack where clients connect to a server
+	// by IP address and pretend to be asking for an incorrect host name.
+	// Manager will attempt to obtain a certificate for that host, incorrectly,
+	// eventually reaching the CA's rate limit for certificate requests
+	// and making it impossible to obtain actual certificates.
+	//
+	// See GetCertificate for more details.
+	HostPolicy HostPolicy
+
+	// RenewBefore optionally specifies how early certificates should
+	// be renewed before they expire.
+	//
+	// If zero, they're renewed 30 days before expiration.
+	RenewBefore time.Duration
+
+	// Client is used to perform low-level operations, such as account registration
+	// and requesting new certificates.
+	// If Client is nil, a zero-value acme.Client is used with acme.LetsEncryptURL
+	// directory endpoint and a newly-generated ECDSA P-256 key.
+	//
+	// Mutating the field after the first call of GetCertificate method will have no effect.
+	Client *acme.Client
+
+	// Email optionally specifies a contact email address.
+	// This is used by CAs, such as Let's Encrypt, to notify about problems
+	// with issued certificates.
+	//
+	// If the Client's account key is already registered, Email is not used.
+	Email string
+
+	// ForceRSA makes the Manager generate certificates with 2048-bit RSA keys.
+	//
+	// If false, a default is used. Currently the default
+	// is EC-based keys using the P-256 curve.
+	ForceRSA bool
+
+	clientMu sync.Mutex
+	client   *acme.Client // initialized by acmeClient method
+
+	stateMu sync.Mutex
+	state   map[string]*certState // keyed by domain name
+
+	// renewal tracks the set of domains currently running renewal timers.
+	// It is keyed by domain name.
+	renewalMu sync.Mutex
+	renewal   map[string]*domainRenewal
+
+	// tokensMu guards the rest of the fields: tryHTTP01, certTokens and httpTokens.
+	tokensMu sync.RWMutex
+	// tryHTTP01 indicates whether the Manager should try "http-01" challenge type
+	// during the authorization flow.
+	tryHTTP01 bool
+	// httpTokens contains response body values for http-01 challenges
+	// and is keyed by the URL path at which a challenge response is expected
+	// to be provisioned.
+	// The entries are stored for the duration of the authorization flow.
+	httpTokens map[string][]byte
+	// certTokens contains temporary certificates for tls-sni challenges
+	// and is keyed by token domain name, which matches server name of ClientHello.
+	// Keys always have ".acme.invalid" suffix.
+	// The entries are stored for the duration of the authorization flow.
+	certTokens map[string]*tls.Certificate
+}
+
+// GetCertificate implements the tls.Config.GetCertificate hook.
+// It provides a TLS certificate for hello.ServerName host, including answering
+// *.acme.invalid (TLS-SNI) challenges. All other fields of hello are ignored.
+//
+// If m.HostPolicy is non-nil, GetCertificate calls the policy before requesting
+// a new cert. A non-nil error returned from m.HostPolicy halts TLS negotiation.
+// The error is propagated back to the caller of GetCertificate and is user-visible.
+// This does not affect cached certs. See HostPolicy field description for more details.
+func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
+	if m.Prompt == nil {
+		return nil, errors.New("acme/autocert: Manager.Prompt not set")
+	}
+
+	name := hello.ServerName
+	if name == "" {
+		return nil, errors.New("acme/autocert: missing server name")
+	}
+	if !strings.Contains(strings.Trim(name, "."), ".") {
+		return nil, errors.New("acme/autocert: server name component count invalid")
+	}
+	if strings.ContainsAny(name, `/\`) {
+		return nil, errors.New("acme/autocert: server name contains invalid character")
+	}
+
+	// In the worst-case scenario, the timeout needs to account for caching, host policy,
+	// domain ownership verification and certificate issuance.
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
+	defer cancel()
+
+	// check whether this is a token cert requested for TLS-SNI challenge
+	if strings.HasSuffix(name, ".acme.invalid") {
+		m.tokensMu.RLock()
+		defer m.tokensMu.RUnlock()
+		if cert := m.certTokens[name]; cert != nil {
+			return cert, nil
+		}
+		if cert, err := m.cacheGet(ctx, name); err == nil {
+			return cert, nil
+		}
+		// TODO: cache error results?
+		return nil, fmt.Errorf("acme/autocert: no token cert for %q", name)
+	}
+
+	// regular domain
+	name = strings.TrimSuffix(name, ".") // golang.org/issue/18114
+	cert, err := m.cert(ctx, name)
+	if err == nil {
+		return cert, nil
+	}
+	if err != ErrCacheMiss {
+		return nil, err
+	}
+
+	// first-time
+	if err := m.hostPolicy()(ctx, name); err != nil {
+		return nil, err
+	}
+	cert, err = m.createCert(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	m.cachePut(ctx, name, cert)
+	return cert, nil
+}
+
+// HTTPHandler configures the Manager to provision ACME "http-01" challenge responses.
+// It returns an http.Handler that responds to the challenges and must be
+// running on port 80. If it receives a request that is not an ACME challenge,
+// it delegates the request to the optional fallback handler.
+//
+// If fallback is nil, the returned handler redirects all GET and HEAD requests
+// to the default TLS port 443 with 302 Found status code, preserving the original
+// request path and query. It responds with 400 Bad Request to all other HTTP methods.
+// The fallback is not protected by the optional HostPolicy.
+//
+// Because the fallback handler is run with unencrypted port 80 requests,
+// the fallback should not serve TLS-only requests.
+//
+// If HTTPHandler is never called, the Manager will only use TLS SNI
+// challenges for domain verification.
+func (m *Manager) HTTPHandler(fallback http.Handler) http.Handler {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	m.tryHTTP01 = true
+
+	if fallback == nil {
+		fallback = http.HandlerFunc(handleHTTPRedirect)
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.HasPrefix(r.URL.Path, "/.well-known/acme-challenge/") {
+			fallback.ServeHTTP(w, r)
+			return
+		}
+		// A reasonable context timeout for cache and host policy only,
+		// because we don't wait for a new certificate issuance here.
+		ctx, cancel := context.WithTimeout(r.Context(), time.Minute)
+		defer cancel()
+		if err := m.hostPolicy()(ctx, r.Host); err != nil {
+			http.Error(w, err.Error(), http.StatusForbidden)
+			return
+		}
+		data, err := m.httpToken(ctx, r.URL.Path)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusNotFound)
+			return
+		}
+		w.Write(data)
+	})
+}
+
+func handleHTTPRedirect(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "GET" && r.Method != "HEAD" {
+		http.Error(w, "Use HTTPS", http.StatusBadRequest)
+		return
+	}
+	target := "https://" + stripPort(r.Host) + r.URL.RequestURI()
+	http.Redirect(w, r, target, http.StatusFound)
+}
+
+func stripPort(hostport string) string {
+	host, _, err := net.SplitHostPort(hostport)
+	if err != nil {
+		return hostport
+	}
+	return net.JoinHostPort(host, "443")
+}
+
+// cert returns an existing certificate either from m.state or cache.
+// If a certificate is found in cache but not in m.state, the latter will be filled
+// with the cached value.
+func (m *Manager) cert(ctx context.Context, name string) (*tls.Certificate, error) {
+	m.stateMu.Lock()
+	if s, ok := m.state[name]; ok {
+		m.stateMu.Unlock()
+		s.RLock()
+		defer s.RUnlock()
+		return s.tlscert()
+	}
+	defer m.stateMu.Unlock()
+	cert, err := m.cacheGet(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	signer, ok := cert.PrivateKey.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("acme/autocert: private key cannot sign")
+	}
+	if m.state == nil {
+		m.state = make(map[string]*certState)
+	}
+	s := &certState{
+		key:  signer,
+		cert: cert.Certificate,
+		leaf: cert.Leaf,
+	}
+	m.state[name] = s
+	go m.renew(name, s.key, s.leaf.NotAfter)
+	return cert, nil
+}
+
+// cacheGet always returns a valid certificate, or an error otherwise.
+// If a cached certficate exists but is not valid, ErrCacheMiss is returned.
+func (m *Manager) cacheGet(ctx context.Context, domain string) (*tls.Certificate, error) {
+	if m.Cache == nil {
+		return nil, ErrCacheMiss
+	}
+	data, err := m.Cache.Get(ctx, domain)
+	if err != nil {
+		return nil, err
+	}
+
+	// private
+	priv, pub := pem.Decode(data)
+	if priv == nil || !strings.Contains(priv.Type, "PRIVATE") {
+		return nil, ErrCacheMiss
+	}
+	privKey, err := parsePrivateKey(priv.Bytes)
+	if err != nil {
+		return nil, err
+	}
+
+	// public
+	var pubDER [][]byte
+	for len(pub) > 0 {
+		var b *pem.Block
+		b, pub = pem.Decode(pub)
+		if b == nil {
+			break
+		}
+		pubDER = append(pubDER, b.Bytes)
+	}
+	if len(pub) > 0 {
+		// Leftover content not consumed by pem.Decode. Corrupt. Ignore.
+		return nil, ErrCacheMiss
+	}
+
+	// verify and create TLS cert
+	leaf, err := validCert(domain, pubDER, privKey)
+	if err != nil {
+		return nil, ErrCacheMiss
+	}
+	tlscert := &tls.Certificate{
+		Certificate: pubDER,
+		PrivateKey:  privKey,
+		Leaf:        leaf,
+	}
+	return tlscert, nil
+}
+
+func (m *Manager) cachePut(ctx context.Context, domain string, tlscert *tls.Certificate) error {
+	if m.Cache == nil {
+		return nil
+	}
+
+	// contains PEM-encoded data
+	var buf bytes.Buffer
+
+	// private
+	switch key := tlscert.PrivateKey.(type) {
+	case *ecdsa.PrivateKey:
+		if err := encodeECDSAKey(&buf, key); err != nil {
+			return err
+		}
+	case *rsa.PrivateKey:
+		b := x509.MarshalPKCS1PrivateKey(key)
+		pb := &pem.Block{Type: "RSA PRIVATE KEY", Bytes: b}
+		if err := pem.Encode(&buf, pb); err != nil {
+			return err
+		}
+	default:
+		return errors.New("acme/autocert: unknown private key type")
+	}
+
+	// public
+	for _, b := range tlscert.Certificate {
+		pb := &pem.Block{Type: "CERTIFICATE", Bytes: b}
+		if err := pem.Encode(&buf, pb); err != nil {
+			return err
+		}
+	}
+
+	return m.Cache.Put(ctx, domain, buf.Bytes())
+}
+
+func encodeECDSAKey(w io.Writer, key *ecdsa.PrivateKey) error {
+	b, err := x509.MarshalECPrivateKey(key)
+	if err != nil {
+		return err
+	}
+	pb := &pem.Block{Type: "EC PRIVATE KEY", Bytes: b}
+	return pem.Encode(w, pb)
+}
+
+// createCert starts the domain ownership verification and returns a certificate
+// for that domain upon success.
+//
+// If the domain is already being verified, it waits for the existing verification to complete.
+// Either way, createCert blocks for the duration of the whole process.
+func (m *Manager) createCert(ctx context.Context, domain string) (*tls.Certificate, error) {
+	// TODO: maybe rewrite this whole piece using sync.Once
+	state, err := m.certState(domain)
+	if err != nil {
+		return nil, err
+	}
+	// state may exist if another goroutine is already working on it
+	// in which case just wait for it to finish
+	if !state.locked {
+		state.RLock()
+		defer state.RUnlock()
+		return state.tlscert()
+	}
+
+	// We are the first; state is locked.
+	// Unblock the readers when domain ownership is verified
+	// and we got the cert or the process failed.
+	defer state.Unlock()
+	state.locked = false
+
+	der, leaf, err := m.authorizedCert(ctx, state.key, domain)
+	if err != nil {
+		// Remove the failed state after some time,
+		// making the manager call createCert again on the following TLS hello.
+		time.AfterFunc(createCertRetryAfter, func() {
+			defer testDidRemoveState(domain)
+			m.stateMu.Lock()
+			defer m.stateMu.Unlock()
+			// Verify the state hasn't changed and it's still invalid
+			// before deleting.
+			s, ok := m.state[domain]
+			if !ok {
+				return
+			}
+			if _, err := validCert(domain, s.cert, s.key); err == nil {
+				return
+			}
+			delete(m.state, domain)
+		})
+		return nil, err
+	}
+	state.cert = der
+	state.leaf = leaf
+	go m.renew(domain, state.key, state.leaf.NotAfter)
+	return state.tlscert()
+}
+
+// certState returns a new or existing certState.
+// If a new certState is returned, state.exist is false and the state is locked.
+// The returned error is non-nil only in the case where a new state could not be created.
+func (m *Manager) certState(domain string) (*certState, error) {
+	m.stateMu.Lock()
+	defer m.stateMu.Unlock()
+	if m.state == nil {
+		m.state = make(map[string]*certState)
+	}
+	// existing state
+	if state, ok := m.state[domain]; ok {
+		return state, nil
+	}
+
+	// new locked state
+	var (
+		err error
+		key crypto.Signer
+	)
+	if m.ForceRSA {
+		key, err = rsa.GenerateKey(rand.Reader, 2048)
+	} else {
+		key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	state := &certState{
+		key:    key,
+		locked: true,
+	}
+	state.Lock() // will be unlocked by m.certState caller
+	m.state[domain] = state
+	return state, nil
+}
+
+// authorizedCert starts the domain ownership verification process and requests a new cert upon success.
+// The key argument is the certificate private key.
+func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, domain string) (der [][]byte, leaf *x509.Certificate, err error) {
+	client, err := m.acmeClient(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if err := m.verify(ctx, client, domain); err != nil {
+		return nil, nil, err
+	}
+	csr, err := certRequest(key, domain)
+	if err != nil {
+		return nil, nil, err
+	}
+	der, _, err = client.CreateCert(ctx, csr, 0, true)
+	if err != nil {
+		return nil, nil, err
+	}
+	leaf, err = validCert(domain, der, key)
+	if err != nil {
+		return nil, nil, err
+	}
+	return der, leaf, nil
+}
+
+// verify runs the identifier (domain) authorization flow
+// using each applicable ACME challenge type.
+func (m *Manager) verify(ctx context.Context, client *acme.Client, domain string) error {
+	// The list of challenge types we'll try to fulfill
+	// in this specific order.
+	challengeTypes := []string{"tls-sni-02", "tls-sni-01"}
+	m.tokensMu.RLock()
+	if m.tryHTTP01 {
+		challengeTypes = append(challengeTypes, "http-01")
+	}
+	m.tokensMu.RUnlock()
+
+	var nextTyp int // challengeType index of the next challenge type to try
+	for {
+		// Start domain authorization and get the challenge.
+		authz, err := client.Authorize(ctx, domain)
+		if err != nil {
+			return err
+		}
+		// No point in accepting challenges if the authorization status
+		// is in a final state.
+		switch authz.Status {
+		case acme.StatusValid:
+			return nil // already authorized
+		case acme.StatusInvalid:
+			return fmt.Errorf("acme/autocert: invalid authorization %q", authz.URI)
+		}
+
+		// Pick the next preferred challenge.
+		var chal *acme.Challenge
+		for chal == nil && nextTyp < len(challengeTypes) {
+			chal = pickChallenge(challengeTypes[nextTyp], authz.Challenges)
+			nextTyp++
+		}
+		if chal == nil {
+			return fmt.Errorf("acme/autocert: unable to authorize %q; tried %q", domain, challengeTypes)
+		}
+		cleanup, err := m.fulfill(ctx, client, chal)
+		if err != nil {
+			continue
+		}
+		defer cleanup()
+		if _, err := client.Accept(ctx, chal); err != nil {
+			continue
+		}
+
+		// A challenge is fulfilled and accepted: wait for the CA to validate.
+		if _, err := client.WaitAuthorization(ctx, authz.URI); err == nil {
+			return nil
+		}
+	}
+}
+
+// fulfill provisions a response to the challenge chal.
+// The cleanup is non-nil only if provisioning succeeded.
+func (m *Manager) fulfill(ctx context.Context, client *acme.Client, chal *acme.Challenge) (cleanup func(), err error) {
+	switch chal.Type {
+	case "tls-sni-01":
+		cert, name, err := client.TLSSNI01ChallengeCert(chal.Token)
+		if err != nil {
+			return nil, err
+		}
+		m.putCertToken(ctx, name, &cert)
+		return func() { go m.deleteCertToken(name) }, nil
+	case "tls-sni-02":
+		cert, name, err := client.TLSSNI02ChallengeCert(chal.Token)
+		if err != nil {
+			return nil, err
+		}
+		m.putCertToken(ctx, name, &cert)
+		return func() { go m.deleteCertToken(name) }, nil
+	case "http-01":
+		resp, err := client.HTTP01ChallengeResponse(chal.Token)
+		if err != nil {
+			return nil, err
+		}
+		p := client.HTTP01ChallengePath(chal.Token)
+		m.putHTTPToken(ctx, p, resp)
+		return func() { go m.deleteHTTPToken(p) }, nil
+	}
+	return nil, fmt.Errorf("acme/autocert: unknown challenge type %q", chal.Type)
+}
+
+func pickChallenge(typ string, chal []*acme.Challenge) *acme.Challenge {
+	for _, c := range chal {
+		if c.Type == typ {
+			return c
+		}
+	}
+	return nil
+}
+
+// putCertToken stores the cert under the named key in both m.certTokens map
+// and m.Cache.
+func (m *Manager) putCertToken(ctx context.Context, name string, cert *tls.Certificate) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	if m.certTokens == nil {
+		m.certTokens = make(map[string]*tls.Certificate)
+	}
+	m.certTokens[name] = cert
+	m.cachePut(ctx, name, cert)
+}
+
+// deleteCertToken removes the token certificate for the specified domain name
+// from both m.certTokens map and m.Cache.
+func (m *Manager) deleteCertToken(name string) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	delete(m.certTokens, name)
+	if m.Cache != nil {
+		m.Cache.Delete(context.Background(), name)
+	}
+}
+
+// httpToken retrieves an existing http-01 token value from an in-memory map
+// or the optional cache.
+func (m *Manager) httpToken(ctx context.Context, tokenPath string) ([]byte, error) {
+	m.tokensMu.RLock()
+	defer m.tokensMu.RUnlock()
+	if v, ok := m.httpTokens[tokenPath]; ok {
+		return v, nil
+	}
+	if m.Cache == nil {
+		return nil, fmt.Errorf("acme/autocert: no token at %q", tokenPath)
+	}
+	return m.Cache.Get(ctx, httpTokenCacheKey(tokenPath))
+}
+
+// putHTTPToken stores an http-01 token value using tokenPath as key
+// in both in-memory map and the optional Cache.
+//
+// It ignores any error returned from Cache.Put.
+func (m *Manager) putHTTPToken(ctx context.Context, tokenPath, val string) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	if m.httpTokens == nil {
+		m.httpTokens = make(map[string][]byte)
+	}
+	b := []byte(val)
+	m.httpTokens[tokenPath] = b
+	if m.Cache != nil {
+		m.Cache.Put(ctx, httpTokenCacheKey(tokenPath), b)
+	}
+}
+
+// deleteHTTPToken removes an http-01 token value from both in-memory map
+// and the optional Cache, ignoring any error returned from the latter.
+//
+// If m.Cache is non-nil, it blocks until Cache.Delete returns without a timeout.
+func (m *Manager) deleteHTTPToken(tokenPath string) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	delete(m.httpTokens, tokenPath)
+	if m.Cache != nil {
+		m.Cache.Delete(context.Background(), httpTokenCacheKey(tokenPath))
+	}
+}
+
+// httpTokenCacheKey returns a key at which an http-01 token value may be stored
+// in the Manager's optional Cache.
+func httpTokenCacheKey(tokenPath string) string {
+	return "http-01-" + path.Base(tokenPath)
+}
+
+// renew starts a cert renewal timer loop, one per domain.
+//
+// The loop is scheduled in two cases:
+// - a cert was fetched from cache for the first time (wasn't in m.state)
+// - a new cert was created by m.createCert
+//
+// The key argument is a certificate private key.
+// The exp argument is the cert expiration time (NotAfter).
+func (m *Manager) renew(domain string, key crypto.Signer, exp time.Time) {
+	m.renewalMu.Lock()
+	defer m.renewalMu.Unlock()
+	if m.renewal[domain] != nil {
+		// another goroutine is already on it
+		return
+	}
+	if m.renewal == nil {
+		m.renewal = make(map[string]*domainRenewal)
+	}
+	dr := &domainRenewal{m: m, domain: domain, key: key}
+	m.renewal[domain] = dr
+	dr.start(exp)
+}
+
+// stopRenew stops all currently running cert renewal timers.
+// The timers are not restarted during the lifetime of the Manager.
+func (m *Manager) stopRenew() {
+	m.renewalMu.Lock()
+	defer m.renewalMu.Unlock()
+	for name, dr := range m.renewal {
+		delete(m.renewal, name)
+		dr.stop()
+	}
+}
+
+func (m *Manager) accountKey(ctx context.Context) (crypto.Signer, error) {
+	const keyName = "acme_account.key"
+
+	genKey := func() (*ecdsa.PrivateKey, error) {
+		return ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	}
+
+	if m.Cache == nil {
+		return genKey()
+	}
+
+	data, err := m.Cache.Get(ctx, keyName)
+	if err == ErrCacheMiss {
+		key, err := genKey()
+		if err != nil {
+			return nil, err
+		}
+		var buf bytes.Buffer
+		if err := encodeECDSAKey(&buf, key); err != nil {
+			return nil, err
+		}
+		if err := m.Cache.Put(ctx, keyName, buf.Bytes()); err != nil {
+			return nil, err
+		}
+		return key, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	priv, _ := pem.Decode(data)
+	if priv == nil || !strings.Contains(priv.Type, "PRIVATE") {
+		return nil, errors.New("acme/autocert: invalid account key found in cache")
+	}
+	return parsePrivateKey(priv.Bytes)
+}
+
+func (m *Manager) acmeClient(ctx context.Context) (*acme.Client, error) {
+	m.clientMu.Lock()
+	defer m.clientMu.Unlock()
+	if m.client != nil {
+		return m.client, nil
+	}
+
+	client := m.Client
+	if client == nil {
+		client = &acme.Client{DirectoryURL: acme.LetsEncryptURL}
+	}
+	if client.Key == nil {
+		var err error
+		client.Key, err = m.accountKey(ctx)
+		if err != nil {
+			return nil, err
+		}
+	}
+	var contact []string
+	if m.Email != "" {
+		contact = []string{"mailto:" + m.Email}
+	}
+	a := &acme.Account{Contact: contact}
+	_, err := client.Register(ctx, a, m.Prompt)
+	if ae, ok := err.(*acme.Error); err == nil || ok && ae.StatusCode == http.StatusConflict {
+		// conflict indicates the key is already registered
+		m.client = client
+		err = nil
+	}
+	return m.client, err
+}
+
+func (m *Manager) hostPolicy() HostPolicy {
+	if m.HostPolicy != nil {
+		return m.HostPolicy
+	}
+	return defaultHostPolicy
+}
+
+func (m *Manager) renewBefore() time.Duration {
+	if m.RenewBefore > renewJitter {
+		return m.RenewBefore
+	}
+	return 720 * time.Hour // 30 days
+}
+
+// certState is ready when its mutex is unlocked for reading.
+type certState struct {
+	sync.RWMutex
+	locked bool              // locked for read/write
+	key    crypto.Signer     // private key for cert
+	cert   [][]byte          // DER encoding
+	leaf   *x509.Certificate // parsed cert[0]; always non-nil if cert != nil
+}
+
+// tlscert creates a tls.Certificate from s.key and s.cert.
+// Callers should wrap it in s.RLock() and s.RUnlock().
+func (s *certState) tlscert() (*tls.Certificate, error) {
+	if s.key == nil {
+		return nil, errors.New("acme/autocert: missing signer")
+	}
+	if len(s.cert) == 0 {
+		return nil, errors.New("acme/autocert: missing certificate")
+	}
+	return &tls.Certificate{
+		PrivateKey:  s.key,
+		Certificate: s.cert,
+		Leaf:        s.leaf,
+	}, nil
+}
+
+// certRequest creates a certificate request for the given common name cn
+// and optional SANs.
+func certRequest(key crypto.Signer, cn string, san ...string) ([]byte, error) {
+	req := &x509.CertificateRequest{
+		Subject:  pkix.Name{CommonName: cn},
+		DNSNames: san,
+	}
+	return x509.CreateCertificateRequest(rand.Reader, req, key)
+}
+
+// Attempt to parse the given private key DER block. OpenSSL 0.9.8 generates
+// PKCS#1 private keys by default, while OpenSSL 1.0.0 generates PKCS#8 keys.
+// OpenSSL ecparam generates SEC1 EC private keys for ECDSA. We try all three.
+//
+// Inspired by parsePrivateKey in crypto/tls/tls.go.
+func parsePrivateKey(der []byte) (crypto.Signer, error) {
+	if key, err := x509.ParsePKCS1PrivateKey(der); err == nil {
+		return key, nil
+	}
+	if key, err := x509.ParsePKCS8PrivateKey(der); err == nil {
+		switch key := key.(type) {
+		case *rsa.PrivateKey:
+			return key, nil
+		case *ecdsa.PrivateKey:
+			return key, nil
+		default:
+			return nil, errors.New("acme/autocert: unknown private key type in PKCS#8 wrapping")
+		}
+	}
+	if key, err := x509.ParseECPrivateKey(der); err == nil {
+		return key, nil
+	}
+
+	return nil, errors.New("acme/autocert: failed to parse private key")
+}
+
+// validCert parses a cert chain provided as der argument and verifies the leaf, der[0],
+// corresponds to the private key, as well as the domain match and expiration dates.
+// It doesn't do any revocation checking.
+//
+// The returned value is the verified leaf cert.
+func validCert(domain string, der [][]byte, key crypto.Signer) (leaf *x509.Certificate, err error) {
+	// parse public part(s)
+	var n int
+	for _, b := range der {
+		n += len(b)
+	}
+	pub := make([]byte, n)
+	n = 0
+	for _, b := range der {
+		n += copy(pub[n:], b)
+	}
+	x509Cert, err := x509.ParseCertificates(pub)
+	if len(x509Cert) == 0 {
+		return nil, errors.New("acme/autocert: no public key found")
+	}
+	// verify the leaf is not expired and matches the domain name
+	leaf = x509Cert[0]
+	now := timeNow()
+	if now.Before(leaf.NotBefore) {
+		return nil, errors.New("acme/autocert: certificate is not valid yet")
+	}
+	if now.After(leaf.NotAfter) {
+		return nil, errors.New("acme/autocert: expired certificate")
+	}
+	if err := leaf.VerifyHostname(domain); err != nil {
+		return nil, err
+	}
+	// ensure the leaf corresponds to the private key
+	switch pub := leaf.PublicKey.(type) {
+	case *rsa.PublicKey:
+		prv, ok := key.(*rsa.PrivateKey)
+		if !ok {
+			return nil, errors.New("acme/autocert: private key type does not match public key type")
+		}
+		if pub.N.Cmp(prv.N) != 0 {
+			return nil, errors.New("acme/autocert: private key does not match public key")
+		}
+	case *ecdsa.PublicKey:
+		prv, ok := key.(*ecdsa.PrivateKey)
+		if !ok {
+			return nil, errors.New("acme/autocert: private key type does not match public key type")
+		}
+		if pub.X.Cmp(prv.X) != 0 || pub.Y.Cmp(prv.Y) != 0 {
+			return nil, errors.New("acme/autocert: private key does not match public key")
+		}
+	default:
+		return nil, errors.New("acme/autocert: unknown public key algorithm")
+	}
+	return leaf, nil
+}
+
+type lockedMathRand struct {
+	sync.Mutex
+	rnd *mathrand.Rand
+}
+
+func (r *lockedMathRand) int63n(max int64) int64 {
+	r.Lock()
+	n := r.rnd.Int63n(max)
+	r.Unlock()
+	return n
+}
+
+// For easier testing.
+var (
+	timeNow = time.Now
+
+	// Called when a state is removed.
+	testDidRemoveState = func(domain string) {}
+)
diff --git a/vendor/golang.org/x/crypto/acme/autocert/cache.go b/vendor/golang.org/x/crypto/acme/autocert/cache.go
new file mode 100644
index 0000000000..61a5fd239a
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/autocert/cache.go
@@ -0,0 +1,130 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package autocert
+
+import (
+	"context"
+	"errors"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// ErrCacheMiss is returned when a certificate is not found in cache.
+var ErrCacheMiss = errors.New("acme/autocert: certificate cache miss")
+
+// Cache is used by Manager to store and retrieve previously obtained certificates
+// as opaque data.
+//
+// The key argument of the methods refers to a domain name but need not be an FQDN.
+// Cache implementations should not rely on the key naming pattern.
+type Cache interface {
+	// Get returns a certificate data for the specified key.
+	// If there's no such key, Get returns ErrCacheMiss.
+	Get(ctx context.Context, key string) ([]byte, error)
+
+	// Put stores the data in the cache under the specified key.
+	// Underlying implementations may use any data storage format,
+	// as long as the reverse operation, Get, results in the original data.
+	Put(ctx context.Context, key string, data []byte) error
+
+	// Delete removes a certificate data from the cache under the specified key.
+	// If there's no such key in the cache, Delete returns nil.
+	Delete(ctx context.Context, key string) error
+}
+
+// DirCache implements Cache using a directory on the local filesystem.
+// If the directory does not exist, it will be created with 0700 permissions.
+type DirCache string
+
+// Get reads a certificate data from the specified file name.
+func (d DirCache) Get(ctx context.Context, name string) ([]byte, error) {
+	name = filepath.Join(string(d), name)
+	var (
+		data []byte
+		err  error
+		done = make(chan struct{})
+	)
+	go func() {
+		data, err = ioutil.ReadFile(name)
+		close(done)
+	}()
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case <-done:
+	}
+	if os.IsNotExist(err) {
+		return nil, ErrCacheMiss
+	}
+	return data, err
+}
+
+// Put writes the certificate data to the specified file name.
+// The file will be created with 0600 permissions.
+func (d DirCache) Put(ctx context.Context, name string, data []byte) error {
+	if err := os.MkdirAll(string(d), 0700); err != nil {
+		return err
+	}
+
+	done := make(chan struct{})
+	var err error
+	go func() {
+		defer close(done)
+		var tmp string
+		if tmp, err = d.writeTempFile(name, data); err != nil {
+			return
+		}
+		select {
+		case <-ctx.Done():
+			// Don't overwrite the file if the context was canceled.
+		default:
+			newName := filepath.Join(string(d), name)
+			err = os.Rename(tmp, newName)
+		}
+	}()
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-done:
+	}
+	return err
+}
+
+// Delete removes the specified file name.
+func (d DirCache) Delete(ctx context.Context, name string) error {
+	name = filepath.Join(string(d), name)
+	var (
+		err  error
+		done = make(chan struct{})
+	)
+	go func() {
+		err = os.Remove(name)
+		close(done)
+	}()
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-done:
+	}
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
+
+// writeTempFile writes b to a temporary file, closes the file and returns its path.
+func (d DirCache) writeTempFile(prefix string, b []byte) (string, error) {
+	// TempFile uses 0600 permissions
+	f, err := ioutil.TempFile(string(d), prefix)
+	if err != nil {
+		return "", err
+	}
+	if _, err := f.Write(b); err != nil {
+		f.Close()
+		return "", err
+	}
+	return f.Name(), f.Close()
+}
diff --git a/vendor/golang.org/x/crypto/acme/autocert/listener.go b/vendor/golang.org/x/crypto/acme/autocert/listener.go
new file mode 100644
index 0000000000..d744df0ed0
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/autocert/listener.go
@@ -0,0 +1,160 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package autocert
+
+import (
+	"crypto/tls"
+	"log"
+	"net"
+	"os"
+	"path/filepath"
+	"runtime"
+	"time"
+)
+
+// NewListener returns a net.Listener that listens on the standard TLS
+// port (443) on all interfaces and returns *tls.Conn connections with
+// LetsEncrypt certificates for the provided domain or domains.
+//
+// It enables one-line HTTPS servers:
+//
+//     log.Fatal(http.Serve(autocert.NewListener("example.com"), handler))
+//
+// NewListener is a convenience function for a common configuration.
+// More complex or custom configurations can use the autocert.Manager
+// type instead.
+//
+// Use of this function implies acceptance of the LetsEncrypt Terms of
+// Service. If domains is not empty, the provided domains are passed
+// to HostWhitelist. If domains is empty, the listener will do
+// LetsEncrypt challenges for any requested domain, which is not
+// recommended.
+//
+// Certificates are cached in a "golang-autocert" directory under an
+// operating system-specific cache or temp directory. This may not
+// be suitable for servers spanning multiple machines.
+//
+// The returned listener uses a *tls.Config that enables HTTP/2, and
+// should only be used with servers that support HTTP/2.
+//
+// The returned Listener also enables TCP keep-alives on the accepted
+// connections. The returned *tls.Conn are returned before their TLS
+// handshake has completed.
+func NewListener(domains ...string) net.Listener {
+	m := &Manager{
+		Prompt: AcceptTOS,
+	}
+	if len(domains) > 0 {
+		m.HostPolicy = HostWhitelist(domains...)
+	}
+	dir := cacheDir()
+	if err := os.MkdirAll(dir, 0700); err != nil {
+		log.Printf("warning: autocert.NewListener not using a cache: %v", err)
+	} else {
+		m.Cache = DirCache(dir)
+	}
+	return m.Listener()
+}
+
+// Listener listens on the standard TLS port (443) on all interfaces
+// and returns a net.Listener returning *tls.Conn connections.
+//
+// The returned listener uses a *tls.Config that enables HTTP/2, and
+// should only be used with servers that support HTTP/2.
+//
+// The returned Listener also enables TCP keep-alives on the accepted
+// connections. The returned *tls.Conn are returned before their TLS
+// handshake has completed.
+//
+// Unlike NewListener, it is the caller's responsibility to initialize
+// the Manager m's Prompt, Cache, HostPolicy, and other desired options.
+func (m *Manager) Listener() net.Listener {
+	ln := &listener{
+		m: m,
+		conf: &tls.Config{
+			GetCertificate: m.GetCertificate,           // bonus: panic on nil m
+			NextProtos:     []string{"h2", "http/1.1"}, // Enable HTTP/2
+		},
+	}
+	ln.tcpListener, ln.tcpListenErr = net.Listen("tcp", ":443")
+	return ln
+}
+
+type listener struct {
+	m    *Manager
+	conf *tls.Config
+
+	tcpListener  net.Listener
+	tcpListenErr error
+}
+
+func (ln *listener) Accept() (net.Conn, error) {
+	if ln.tcpListenErr != nil {
+		return nil, ln.tcpListenErr
+	}
+	conn, err := ln.tcpListener.Accept()
+	if err != nil {
+		return nil, err
+	}
+	tcpConn := conn.(*net.TCPConn)
+
+	// Because Listener is a convenience function, help out with
+	// this too.  This is not possible for the caller to set once
+	// we return a *tcp.Conn wrapping an inaccessible net.Conn.
+	// If callers don't want this, they can do things the manual
+	// way and tweak as needed. But this is what net/http does
+	// itself, so copy that. If net/http changes, we can change
+	// here too.
+	tcpConn.SetKeepAlive(true)
+	tcpConn.SetKeepAlivePeriod(3 * time.Minute)
+
+	return tls.Server(tcpConn, ln.conf), nil
+}
+
+func (ln *listener) Addr() net.Addr {
+	if ln.tcpListener != nil {
+		return ln.tcpListener.Addr()
+	}
+	// net.Listen failed. Return something non-nil in case callers
+	// call Addr before Accept:
+	return &net.TCPAddr{IP: net.IP{0, 0, 0, 0}, Port: 443}
+}
+
+func (ln *listener) Close() error {
+	if ln.tcpListenErr != nil {
+		return ln.tcpListenErr
+	}
+	return ln.tcpListener.Close()
+}
+
+func homeDir() string {
+	if runtime.GOOS == "windows" {
+		return os.Getenv("HOMEDRIVE") + os.Getenv("HOMEPATH")
+	}
+	if h := os.Getenv("HOME"); h != "" {
+		return h
+	}
+	return "/"
+}
+
+func cacheDir() string {
+	const base = "golang-autocert"
+	switch runtime.GOOS {
+	case "darwin":
+		return filepath.Join(homeDir(), "Library", "Caches", base)
+	case "windows":
+		for _, ev := range []string{"APPDATA", "CSIDL_APPDATA", "TEMP", "TMP"} {
+			if v := os.Getenv(ev); v != "" {
+				return filepath.Join(v, base)
+			}
+		}
+		// Worst case:
+		return filepath.Join(homeDir(), base)
+	}
+	if xdg := os.Getenv("XDG_CACHE_HOME"); xdg != "" {
+		return filepath.Join(xdg, base)
+	}
+	return filepath.Join(homeDir(), ".cache", base)
+}
diff --git a/vendor/golang.org/x/crypto/acme/autocert/renewal.go b/vendor/golang.org/x/crypto/acme/autocert/renewal.go
new file mode 100644
index 0000000000..3fa4d61a22
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/autocert/renewal.go
@@ -0,0 +1,141 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package autocert
+
+import (
+	"context"
+	"crypto"
+	"sync"
+	"time"
+)
+
+// renewJitter is the maximum deviation from Manager.RenewBefore.
+const renewJitter = time.Hour
+
+// domainRenewal tracks the state used by the periodic timers
+// renewing a single domain's cert.
+type domainRenewal struct {
+	m      *Manager
+	domain string
+	key    crypto.Signer
+
+	timerMu sync.Mutex
+	timer   *time.Timer
+}
+
+// start starts a cert renewal timer at the time
+// defined by the certificate expiration time exp.
+//
+// If the timer is already started, calling start is a noop.
+func (dr *domainRenewal) start(exp time.Time) {
+	dr.timerMu.Lock()
+	defer dr.timerMu.Unlock()
+	if dr.timer != nil {
+		return
+	}
+	dr.timer = time.AfterFunc(dr.next(exp), dr.renew)
+}
+
+// stop stops the cert renewal timer.
+// If the timer is already stopped, calling stop is a noop.
+func (dr *domainRenewal) stop() {
+	dr.timerMu.Lock()
+	defer dr.timerMu.Unlock()
+	if dr.timer == nil {
+		return
+	}
+	dr.timer.Stop()
+	dr.timer = nil
+}
+
+// renew is called periodically by a timer.
+// The first renew call is kicked off by dr.start.
+func (dr *domainRenewal) renew() {
+	dr.timerMu.Lock()
+	defer dr.timerMu.Unlock()
+	if dr.timer == nil {
+		return
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Minute)
+	defer cancel()
+	// TODO: rotate dr.key at some point?
+	next, err := dr.do(ctx)
+	if err != nil {
+		next = renewJitter / 2
+		next += time.Duration(pseudoRand.int63n(int64(next)))
+	}
+	dr.timer = time.AfterFunc(next, dr.renew)
+	testDidRenewLoop(next, err)
+}
+
+// updateState locks and replaces the relevant Manager.state item with the given
+// state. It additionally updates dr.key with the given state's key.
+func (dr *domainRenewal) updateState(state *certState) {
+	dr.m.stateMu.Lock()
+	defer dr.m.stateMu.Unlock()
+	dr.key = state.key
+	dr.m.state[dr.domain] = state
+}
+
+// do is similar to Manager.createCert but it doesn't lock a Manager.state item.
+// Instead, it requests a new certificate independently and, upon success,
+// replaces dr.m.state item with a new one and updates cache for the given domain.
+//
+// It may lock and update the Manager.state if the expiration date of the currently
+// cached cert is far enough in the future.
+//
+// The returned value is a time interval after which the renewal should occur again.
+func (dr *domainRenewal) do(ctx context.Context) (time.Duration, error) {
+	// a race is likely unavoidable in a distributed environment
+	// but we try nonetheless
+	if tlscert, err := dr.m.cacheGet(ctx, dr.domain); err == nil {
+		next := dr.next(tlscert.Leaf.NotAfter)
+		if next > dr.m.renewBefore()+renewJitter {
+			signer, ok := tlscert.PrivateKey.(crypto.Signer)
+			if ok {
+				state := &certState{
+					key:  signer,
+					cert: tlscert.Certificate,
+					leaf: tlscert.Leaf,
+				}
+				dr.updateState(state)
+				return next, nil
+			}
+		}
+	}
+
+	der, leaf, err := dr.m.authorizedCert(ctx, dr.key, dr.domain)
+	if err != nil {
+		return 0, err
+	}
+	state := &certState{
+		key:  dr.key,
+		cert: der,
+		leaf: leaf,
+	}
+	tlscert, err := state.tlscert()
+	if err != nil {
+		return 0, err
+	}
+	if err := dr.m.cachePut(ctx, dr.domain, tlscert); err != nil {
+		return 0, err
+	}
+	dr.updateState(state)
+	return dr.next(leaf.NotAfter), nil
+}
+
+func (dr *domainRenewal) next(expiry time.Time) time.Duration {
+	d := expiry.Sub(timeNow()) - dr.m.renewBefore()
+	// add a bit of randomness to renew deadline
+	n := pseudoRand.int63n(int64(renewJitter))
+	d -= time.Duration(n)
+	if d < 0 {
+		return 0
+	}
+	return d
+}
+
+var testDidRenewLoop = func(next time.Duration, err error) {}
diff --git a/vendor/golang.org/x/crypto/acme/jws.go b/vendor/golang.org/x/crypto/acme/jws.go
new file mode 100644
index 0000000000..6cbca25de9
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/jws.go
@@ -0,0 +1,153 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package acme
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	_ "crypto/sha512" // need for EC keys
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"math/big"
+)
+
+// jwsEncodeJSON signs claimset using provided key and a nonce.
+// The result is serialized in JSON format.
+// See https://tools.ietf.org/html/rfc7515#section-7.
+func jwsEncodeJSON(claimset interface{}, key crypto.Signer, nonce string) ([]byte, error) {
+	jwk, err := jwkEncode(key.Public())
+	if err != nil {
+		return nil, err
+	}
+	alg, sha := jwsHasher(key)
+	if alg == "" || !sha.Available() {
+		return nil, ErrUnsupportedKey
+	}
+	phead := fmt.Sprintf(`{"alg":%q,"jwk":%s,"nonce":%q}`, alg, jwk, nonce)
+	phead = base64.RawURLEncoding.EncodeToString([]byte(phead))
+	cs, err := json.Marshal(claimset)
+	if err != nil {
+		return nil, err
+	}
+	payload := base64.RawURLEncoding.EncodeToString(cs)
+	hash := sha.New()
+	hash.Write([]byte(phead + "." + payload))
+	sig, err := jwsSign(key, sha, hash.Sum(nil))
+	if err != nil {
+		return nil, err
+	}
+
+	enc := struct {
+		Protected string `json:"protected"`
+		Payload   string `json:"payload"`
+		Sig       string `json:"signature"`
+	}{
+		Protected: phead,
+		Payload:   payload,
+		Sig:       base64.RawURLEncoding.EncodeToString(sig),
+	}
+	return json.Marshal(&enc)
+}
+
+// jwkEncode encodes public part of an RSA or ECDSA key into a JWK.
+// The result is also suitable for creating a JWK thumbprint.
+// https://tools.ietf.org/html/rfc7517
+func jwkEncode(pub crypto.PublicKey) (string, error) {
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		// https://tools.ietf.org/html/rfc7518#section-6.3.1
+		n := pub.N
+		e := big.NewInt(int64(pub.E))
+		// Field order is important.
+		// See https://tools.ietf.org/html/rfc7638#section-3.3 for details.
+		return fmt.Sprintf(`{"e":"%s","kty":"RSA","n":"%s"}`,
+			base64.RawURLEncoding.EncodeToString(e.Bytes()),
+			base64.RawURLEncoding.EncodeToString(n.Bytes()),
+		), nil
+	case *ecdsa.PublicKey:
+		// https://tools.ietf.org/html/rfc7518#section-6.2.1
+		p := pub.Curve.Params()
+		n := p.BitSize / 8
+		if p.BitSize%8 != 0 {
+			n++
+		}
+		x := pub.X.Bytes()
+		if n > len(x) {
+			x = append(make([]byte, n-len(x)), x...)
+		}
+		y := pub.Y.Bytes()
+		if n > len(y) {
+			y = append(make([]byte, n-len(y)), y...)
+		}
+		// Field order is important.
+		// See https://tools.ietf.org/html/rfc7638#section-3.3 for details.
+		return fmt.Sprintf(`{"crv":"%s","kty":"EC","x":"%s","y":"%s"}`,
+			p.Name,
+			base64.RawURLEncoding.EncodeToString(x),
+			base64.RawURLEncoding.EncodeToString(y),
+		), nil
+	}
+	return "", ErrUnsupportedKey
+}
+
+// jwsSign signs the digest using the given key.
+// It returns ErrUnsupportedKey if the key type is unknown.
+// The hash is used only for RSA keys.
+func jwsSign(key crypto.Signer, hash crypto.Hash, digest []byte) ([]byte, error) {
+	switch key := key.(type) {
+	case *rsa.PrivateKey:
+		return key.Sign(rand.Reader, digest, hash)
+	case *ecdsa.PrivateKey:
+		r, s, err := ecdsa.Sign(rand.Reader, key, digest)
+		if err != nil {
+			return nil, err
+		}
+		rb, sb := r.Bytes(), s.Bytes()
+		size := key.Params().BitSize / 8
+		if size%8 > 0 {
+			size++
+		}
+		sig := make([]byte, size*2)
+		copy(sig[size-len(rb):], rb)
+		copy(sig[size*2-len(sb):], sb)
+		return sig, nil
+	}
+	return nil, ErrUnsupportedKey
+}
+
+// jwsHasher indicates suitable JWS algorithm name and a hash function
+// to use for signing a digest with the provided key.
+// It returns ("", 0) if the key is not supported.
+func jwsHasher(key crypto.Signer) (string, crypto.Hash) {
+	switch key := key.(type) {
+	case *rsa.PrivateKey:
+		return "RS256", crypto.SHA256
+	case *ecdsa.PrivateKey:
+		switch key.Params().Name {
+		case "P-256":
+			return "ES256", crypto.SHA256
+		case "P-384":
+			return "ES384", crypto.SHA384
+		case "P-521":
+			return "ES512", crypto.SHA512
+		}
+	}
+	return "", 0
+}
+
+// JWKThumbprint creates a JWK thumbprint out of pub
+// as specified in https://tools.ietf.org/html/rfc7638.
+func JWKThumbprint(pub crypto.PublicKey) (string, error) {
+	jwk, err := jwkEncode(pub)
+	if err != nil {
+		return "", err
+	}
+	b := sha256.Sum256([]byte(jwk))
+	return base64.RawURLEncoding.EncodeToString(b[:]), nil
+}
diff --git a/vendor/golang.org/x/crypto/acme/types.go b/vendor/golang.org/x/crypto/acme/types.go
new file mode 100644
index 0000000000..3e199749ec
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/types.go
@@ -0,0 +1,329 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package acme
+
+import (
+	"crypto"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+)
+
+// ACME server response statuses used to describe Authorization and Challenge states.
+const (
+	StatusUnknown    = "unknown"
+	StatusPending    = "pending"
+	StatusProcessing = "processing"
+	StatusValid      = "valid"
+	StatusInvalid    = "invalid"
+	StatusRevoked    = "revoked"
+)
+
+// CRLReasonCode identifies the reason for a certificate revocation.
+type CRLReasonCode int
+
+// CRL reason codes as defined in RFC 5280.
+const (
+	CRLReasonUnspecified          CRLReasonCode = 0
+	CRLReasonKeyCompromise        CRLReasonCode = 1
+	CRLReasonCACompromise         CRLReasonCode = 2
+	CRLReasonAffiliationChanged   CRLReasonCode = 3
+	CRLReasonSuperseded           CRLReasonCode = 4
+	CRLReasonCessationOfOperation CRLReasonCode = 5
+	CRLReasonCertificateHold      CRLReasonCode = 6
+	CRLReasonRemoveFromCRL        CRLReasonCode = 8
+	CRLReasonPrivilegeWithdrawn   CRLReasonCode = 9
+	CRLReasonAACompromise         CRLReasonCode = 10
+)
+
+// ErrUnsupportedKey is returned when an unsupported key type is encountered.
+var ErrUnsupportedKey = errors.New("acme: unknown key type; only RSA and ECDSA are supported")
+
+// Error is an ACME error, defined in Problem Details for HTTP APIs doc
+// http://tools.ietf.org/html/draft-ietf-appsawg-http-problem.
+type Error struct {
+	// StatusCode is The HTTP status code generated by the origin server.
+	StatusCode int
+	// ProblemType is a URI reference that identifies the problem type,
+	// typically in a "urn:acme:error:xxx" form.
+	ProblemType string
+	// Detail is a human-readable explanation specific to this occurrence of the problem.
+	Detail string
+	// Header is the original server error response headers.
+	// It may be nil.
+	Header http.Header
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
+}
+
+// AuthorizationError indicates that an authorization for an identifier
+// did not succeed.
+// It contains all errors from Challenge items of the failed Authorization.
+type AuthorizationError struct {
+	// URI uniquely identifies the failed Authorization.
+	URI string
+
+	// Identifier is an AuthzID.Value of the failed Authorization.
+	Identifier string
+
+	// Errors is a collection of non-nil error values of Challenge items
+	// of the failed Authorization.
+	Errors []error
+}
+
+func (a *AuthorizationError) Error() string {
+	e := make([]string, len(a.Errors))
+	for i, err := range a.Errors {
+		e[i] = err.Error()
+	}
+	return fmt.Sprintf("acme: authorization error for %s: %s", a.Identifier, strings.Join(e, "; "))
+}
+
+// RateLimit reports whether err represents a rate limit error and
+// any Retry-After duration returned by the server.
+//
+// See the following for more details on rate limiting:
+// https://tools.ietf.org/html/draft-ietf-acme-acme-05#section-5.6
+func RateLimit(err error) (time.Duration, bool) {
+	e, ok := err.(*Error)
+	if !ok {
+		return 0, false
+	}
+	// Some CA implementations may return incorrect values.
+	// Use case-insensitive comparison.
+	if !strings.HasSuffix(strings.ToLower(e.ProblemType), ":ratelimited") {
+		return 0, false
+	}
+	if e.Header == nil {
+		return 0, true
+	}
+	return retryAfter(e.Header.Get("Retry-After"), 0), true
+}
+
+// Account is a user account. It is associated with a private key.
+type Account struct {
+	// URI is the account unique ID, which is also a URL used to retrieve
+	// account data from the CA.
+	URI string
+
+	// Contact is a slice of contact info used during registration.
+	Contact []string
+
+	// The terms user has agreed to.
+	// A value not matching CurrentTerms indicates that the user hasn't agreed
+	// to the actual Terms of Service of the CA.
+	AgreedTerms string
+
+	// Actual terms of a CA.
+	CurrentTerms string
+
+	// Authz is the authorization URL used to initiate a new authz flow.
+	Authz string
+
+	// Authorizations is a URI from which a list of authorizations
+	// granted to this account can be fetched via a GET request.
+	Authorizations string
+
+	// Certificates is a URI from which a list of certificates
+	// issued for this account can be fetched via a GET request.
+	Certificates string
+}
+
+// Directory is ACME server discovery data.
+type Directory struct {
+	// RegURL is an account endpoint URL, allowing for creating new
+	// and modifying existing accounts.
+	RegURL string
+
+	// AuthzURL is used to initiate Identifier Authorization flow.
+	AuthzURL string
+
+	// CertURL is a new certificate issuance endpoint URL.
+	CertURL string
+
+	// RevokeURL is used to initiate a certificate revocation flow.
+	RevokeURL string
+
+	// Term is a URI identifying the current terms of service.
+	Terms string
+
+	// Website is an HTTP or HTTPS URL locating a website
+	// providing more information about the ACME server.
+	Website string
+
+	// CAA consists of lowercase hostname elements, which the ACME server
+	// recognises as referring to itself for the purposes of CAA record validation
+	// as defined in RFC6844.
+	CAA []string
+}
+
+// Challenge encodes a returned CA challenge.
+// Its Error field may be non-nil if the challenge is part of an Authorization
+// with StatusInvalid.
+type Challenge struct {
+	// Type is the challenge type, e.g. "http-01", "tls-sni-02", "dns-01".
+	Type string
+
+	// URI is where a challenge response can be posted to.
+	URI string
+
+	// Token is a random value that uniquely identifies the challenge.
+	Token string
+
+	// Status identifies the status of this challenge.
+	Status string
+
+	// Error indicates the reason for an authorization failure
+	// when this challenge was used.
+	// The type of a non-nil value is *Error.
+	Error error
+}
+
+// Authorization encodes an authorization response.
+type Authorization struct {
+	// URI uniquely identifies a authorization.
+	URI string
+
+	// Status identifies the status of an authorization.
+	Status string
+
+	// Identifier is what the account is authorized to represent.
+	Identifier AuthzID
+
+	// Challenges that the client needs to fulfill in order to prove possession
+	// of the identifier (for pending authorizations).
+	// For final authorizations, the challenges that were used.
+	Challenges []*Challenge
+
+	// A collection of sets of challenges, each of which would be sufficient
+	// to prove possession of the identifier.
+	// Clients must complete a set of challenges that covers at least one set.
+	// Challenges are identified by their indices in the challenges array.
+	// If this field is empty, the client needs to complete all challenges.
+	Combinations [][]int
+}
+
+// AuthzID is an identifier that an account is authorized to represent.
+type AuthzID struct {
+	Type  string // The type of identifier, e.g. "dns".
+	Value string // The identifier itself, e.g. "example.org".
+}
+
+// wireAuthz is ACME JSON representation of Authorization objects.
+type wireAuthz struct {
+	Status       string
+	Challenges   []wireChallenge
+	Combinations [][]int
+	Identifier   struct {
+		Type  string
+		Value string
+	}
+}
+
+func (z *wireAuthz) authorization(uri string) *Authorization {
+	a := &Authorization{
+		URI:          uri,
+		Status:       z.Status,
+		Identifier:   AuthzID{Type: z.Identifier.Type, Value: z.Identifier.Value},
+		Combinations: z.Combinations, // shallow copy
+		Challenges:   make([]*Challenge, len(z.Challenges)),
+	}
+	for i, v := range z.Challenges {
+		a.Challenges[i] = v.challenge()
+	}
+	return a
+}
+
+func (z *wireAuthz) error(uri string) *AuthorizationError {
+	err := &AuthorizationError{
+		URI:        uri,
+		Identifier: z.Identifier.Value,
+	}
+	for _, raw := range z.Challenges {
+		if raw.Error != nil {
+			err.Errors = append(err.Errors, raw.Error.error(nil))
+		}
+	}
+	return err
+}
+
+// wireChallenge is ACME JSON challenge representation.
+type wireChallenge struct {
+	URI    string `json:"uri"`
+	Type   string
+	Token  string
+	Status string
+	Error  *wireError
+}
+
+func (c *wireChallenge) challenge() *Challenge {
+	v := &Challenge{
+		URI:    c.URI,
+		Type:   c.Type,
+		Token:  c.Token,
+		Status: c.Status,
+	}
+	if v.Status == "" {
+		v.Status = StatusPending
+	}
+	if c.Error != nil {
+		v.Error = c.Error.error(nil)
+	}
+	return v
+}
+
+// wireError is a subset of fields of the Problem Details object
+// as described in https://tools.ietf.org/html/rfc7807#section-3.1.
+type wireError struct {
+	Status int
+	Type   string
+	Detail string
+}
+
+func (e *wireError) error(h http.Header) *Error {
+	return &Error{
+		StatusCode:  e.Status,
+		ProblemType: e.Type,
+		Detail:      e.Detail,
+		Header:      h,
+	}
+}
+
+// CertOption is an optional argument type for the TLSSNIxChallengeCert methods for
+// customizing a temporary certificate for TLS-SNI challenges.
+type CertOption interface {
+	privateCertOpt()
+}
+
+// WithKey creates an option holding a private/public key pair.
+// The private part signs a certificate, and the public part represents the signee.
+func WithKey(key crypto.Signer) CertOption {
+	return &certOptKey{key}
+}
+
+type certOptKey struct {
+	key crypto.Signer
+}
+
+func (*certOptKey) privateCertOpt() {}
+
+// WithTemplate creates an option for specifying a certificate template.
+// See x509.CreateCertificate for template usage details.
+//
+// In TLSSNIxChallengeCert methods, the template is also used as parent,
+// resulting in a self-signed certificate.
+// The DNSNames field of t is always overwritten for tls-sni challenge certs.
+func WithTemplate(t *x509.Certificate) CertOption {
+	return (*certOptTemplate)(t)
+}
+
+type certOptTemplate x509.Certificate
+
+func (*certOptTemplate) privateCertOpt() {}
diff --git a/vendor/golang.org/x/crypto/ed25519/ed25519.go b/vendor/golang.org/x/crypto/ed25519/ed25519.go
index 4f26b49b6a..a57771a1ed 100644
--- a/vendor/golang.org/x/crypto/ed25519/ed25519.go
+++ b/vendor/golang.org/x/crypto/ed25519/ed25519.go
@@ -171,9 +171,16 @@ func Verify(publicKey PublicKey, message, sig []byte) bool {
 	edwards25519.ScReduce(&hReduced, &digest)
 
 	var R edwards25519.ProjectiveGroupElement
-	var b [32]byte
-	copy(b[:], sig[32:])
-	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &b)
+	var s [32]byte
+	copy(s[:], sig[32:])
+
+	// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
+	// the range [0, order) in order to prevent signature malleability.
+	if !edwards25519.ScMinimal(&s) {
+		return false
+	}
+
+	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &s)
 
 	var checkR [32]byte
 	R.ToBytes(&checkR)
diff --git a/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go b/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go
index 5f8b994787..fd03c252af 100644
--- a/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go
+++ b/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go
@@ -4,6 +4,8 @@
 
 package edwards25519
 
+import "encoding/binary"
+
 // This code is a port of the public domain, “ref10” implementation of ed25519
 // from SUPERCOP.
 
@@ -1769,3 +1771,23 @@ func ScReduce(out *[32]byte, s *[64]byte) {
 	out[30] = byte(s11 >> 9)
 	out[31] = byte(s11 >> 17)
 }
+
+// order is the order of Curve25519 in little-endian form.
+var order = [4]uint64{0x5812631a5cf5d3ed, 0x14def9dea2f79cd6, 0, 0x1000000000000000}
+
+// ScMinimal returns true if the given scalar is less than the order of the
+// curve.
+func ScMinimal(scalar *[32]byte) bool {
+	for i := 3; ; i-- {
+		v := binary.LittleEndian.Uint64(scalar[i*8:])
+		if v > order[i] {
+			return false
+		} else if v < order[i] {
+			break
+		} else if i == 0 {
+			return false
+		}
+	}
+
+	return true
+}
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go b/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go
new file mode 100644
index 0000000000..7c7269676a
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go
@@ -0,0 +1,223 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package ChaCha20 implements the core ChaCha20 function as specified
+// in https://tools.ietf.org/html/rfc7539#section-2.3.
+package chacha20
+
+import (
+	"crypto/cipher"
+	"encoding/binary"
+)
+
+// assert that *Cipher implements cipher.Stream
+var _ cipher.Stream = (*Cipher)(nil)
+
+// Cipher is a stateful instance of ChaCha20 using a particular key
+// and nonce. A *Cipher implements the cipher.Stream interface.
+type Cipher struct {
+	key     [8]uint32
+	nonce   [3]uint32
+	counter uint32   // incremented after each block
+	buf     [64]byte // buffer for unused keystream bytes
+	len     int      // number of unused keystream bytes at end of buf
+}
+
+// New creates a new ChaCha20 stream cipher with the given key and nonce.
+// The initial counter value is set to 0.
+func New(key [8]uint32, nonce [3]uint32) *Cipher {
+	return &Cipher{key: key, nonce: nonce}
+}
+
+// XORKeyStream XORs each byte in the given slice with a byte from the
+// cipher's key stream. Dst and src must overlap entirely or not at all.
+//
+// If len(dst) < len(src), XORKeyStream will panic. It is acceptable
+// to pass a dst bigger than src, and in that case, XORKeyStream will
+// only update dst[:len(src)] and will not touch the rest of dst.
+//
+// Multiple calls to XORKeyStream behave as if the concatenation of
+// the src buffers was passed in a single run. That is, Cipher
+// maintains state and does not reset at each XORKeyStream call.
+func (s *Cipher) XORKeyStream(dst, src []byte) {
+	// xor src with buffered keystream first
+	if s.len != 0 {
+		buf := s.buf[len(s.buf)-s.len:]
+		if len(src) < len(buf) {
+			buf = buf[:len(src)]
+		}
+		td, ts := dst[:len(buf)], src[:len(buf)] // BCE hint
+		for i, b := range buf {
+			td[i] = ts[i] ^ b
+		}
+		s.len -= len(buf)
+		if s.len != 0 {
+			return
+		}
+		s.buf = [len(s.buf)]byte{} // zero the empty buffer
+		src = src[len(buf):]
+		dst = dst[len(buf):]
+	}
+
+	if len(src) == 0 {
+		return
+	}
+
+	// set up a 64-byte buffer to pad out the final block if needed
+	// (hoisted out of the main loop to avoid spills)
+	rem := len(src) % 64  // length of final block
+	fin := len(src) - rem // index of final block
+	if rem > 0 {
+		copy(s.buf[len(s.buf)-64:], src[fin:])
+	}
+
+	// qr calculates a quarter round
+	qr := func(a, b, c, d uint32) (uint32, uint32, uint32, uint32) {
+		a += b
+		d ^= a
+		d = (d << 16) | (d >> 16)
+		c += d
+		b ^= c
+		b = (b << 12) | (b >> 20)
+		a += b
+		d ^= a
+		d = (d << 8) | (d >> 24)
+		c += d
+		b ^= c
+		b = (b << 7) | (b >> 25)
+		return a, b, c, d
+	}
+
+	// ChaCha20 constants
+	const (
+		j0 = 0x61707865
+		j1 = 0x3320646e
+		j2 = 0x79622d32
+		j3 = 0x6b206574
+	)
+
+	// pre-calculate most of the first round
+	s1, s5, s9, s13 := qr(j1, s.key[1], s.key[5], s.nonce[0])
+	s2, s6, s10, s14 := qr(j2, s.key[2], s.key[6], s.nonce[1])
+	s3, s7, s11, s15 := qr(j3, s.key[3], s.key[7], s.nonce[2])
+
+	n := len(src)
+	src, dst = src[:n:n], dst[:n:n] // BCE hint
+	for i := 0; i < n; i += 64 {
+		// calculate the remainder of the first round
+		s0, s4, s8, s12 := qr(j0, s.key[0], s.key[4], s.counter)
+
+		// execute the second round
+		x0, x5, x10, x15 := qr(s0, s5, s10, s15)
+		x1, x6, x11, x12 := qr(s1, s6, s11, s12)
+		x2, x7, x8, x13 := qr(s2, s7, s8, s13)
+		x3, x4, x9, x14 := qr(s3, s4, s9, s14)
+
+		// execute the remaining 18 rounds
+		for i := 0; i < 9; i++ {
+			x0, x4, x8, x12 = qr(x0, x4, x8, x12)
+			x1, x5, x9, x13 = qr(x1, x5, x9, x13)
+			x2, x6, x10, x14 = qr(x2, x6, x10, x14)
+			x3, x7, x11, x15 = qr(x3, x7, x11, x15)
+
+			x0, x5, x10, x15 = qr(x0, x5, x10, x15)
+			x1, x6, x11, x12 = qr(x1, x6, x11, x12)
+			x2, x7, x8, x13 = qr(x2, x7, x8, x13)
+			x3, x4, x9, x14 = qr(x3, x4, x9, x14)
+		}
+
+		x0 += j0
+		x1 += j1
+		x2 += j2
+		x3 += j3
+
+		x4 += s.key[0]
+		x5 += s.key[1]
+		x6 += s.key[2]
+		x7 += s.key[3]
+		x8 += s.key[4]
+		x9 += s.key[5]
+		x10 += s.key[6]
+		x11 += s.key[7]
+
+		x12 += s.counter
+		x13 += s.nonce[0]
+		x14 += s.nonce[1]
+		x15 += s.nonce[2]
+
+		// increment the counter
+		s.counter += 1
+		if s.counter == 0 {
+			panic("chacha20: counter overflow")
+		}
+
+		// pad to 64 bytes if needed
+		in, out := src[i:], dst[i:]
+		if i == fin {
+			// src[fin:] has already been copied into s.buf before
+			// the main loop
+			in, out = s.buf[len(s.buf)-64:], s.buf[len(s.buf)-64:]
+		}
+		in, out = in[:64], out[:64] // BCE hint
+
+		// XOR the key stream with the source and write out the result
+		xor(out[0:], in[0:], x0)
+		xor(out[4:], in[4:], x1)
+		xor(out[8:], in[8:], x2)
+		xor(out[12:], in[12:], x3)
+		xor(out[16:], in[16:], x4)
+		xor(out[20:], in[20:], x5)
+		xor(out[24:], in[24:], x6)
+		xor(out[28:], in[28:], x7)
+		xor(out[32:], in[32:], x8)
+		xor(out[36:], in[36:], x9)
+		xor(out[40:], in[40:], x10)
+		xor(out[44:], in[44:], x11)
+		xor(out[48:], in[48:], x12)
+		xor(out[52:], in[52:], x13)
+		xor(out[56:], in[56:], x14)
+		xor(out[60:], in[60:], x15)
+	}
+	// copy any trailing bytes out of the buffer and into dst
+	if rem != 0 {
+		s.len = 64 - rem
+		copy(dst[fin:], s.buf[len(s.buf)-64:])
+	}
+}
+
+// Advance discards bytes in the key stream until the next 64 byte block
+// boundary is reached and updates the counter accordingly. If the key
+// stream is already at a block boundary no bytes will be discarded and
+// the counter will be unchanged.
+func (s *Cipher) Advance() {
+	s.len -= s.len % 64
+	if s.len == 0 {
+		s.buf = [len(s.buf)]byte{}
+	}
+}
+
+// XORKeyStream crypts bytes from in to out using the given key and counters.
+// In and out must overlap entirely or not at all. Counter contains the raw
+// ChaCha20 counter bytes (i.e. block counter followed by nonce).
+func XORKeyStream(out, in []byte, counter *[16]byte, key *[32]byte) {
+	s := Cipher{
+		key: [8]uint32{
+			binary.LittleEndian.Uint32(key[0:4]),
+			binary.LittleEndian.Uint32(key[4:8]),
+			binary.LittleEndian.Uint32(key[8:12]),
+			binary.LittleEndian.Uint32(key[12:16]),
+			binary.LittleEndian.Uint32(key[16:20]),
+			binary.LittleEndian.Uint32(key[20:24]),
+			binary.LittleEndian.Uint32(key[24:28]),
+			binary.LittleEndian.Uint32(key[28:32]),
+		},
+		nonce: [3]uint32{
+			binary.LittleEndian.Uint32(counter[4:8]),
+			binary.LittleEndian.Uint32(counter[8:12]),
+			binary.LittleEndian.Uint32(counter[12:16]),
+		},
+		counter: binary.LittleEndian.Uint32(counter[0:4]),
+	}
+	s.XORKeyStream(out, in)
+}
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/xor.go b/vendor/golang.org/x/crypto/internal/chacha20/xor.go
new file mode 100644
index 0000000000..9c5ba0b33a
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/xor.go
@@ -0,0 +1,43 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found src the LICENSE file.
+
+package chacha20
+
+import (
+	"runtime"
+)
+
+// Platforms that have fast unaligned 32-bit little endian accesses.
+const unaligned = runtime.GOARCH == "386" ||
+	runtime.GOARCH == "amd64" ||
+	runtime.GOARCH == "arm64" ||
+	runtime.GOARCH == "ppc64le" ||
+	runtime.GOARCH == "s390x"
+
+// xor reads a little endian uint32 from src, XORs it with u and
+// places the result in little endian byte order in dst.
+func xor(dst, src []byte, u uint32) {
+	_, _ = src[3], dst[3] // eliminate bounds checks
+	if unaligned {
+		// The compiler should optimize this code into
+		// 32-bit unaligned little endian loads and stores.
+		// TODO: delete once the compiler does a reliably
+		// good job with the generic code below.
+		// See issue #25111 for more details.
+		v := uint32(src[0])
+		v |= uint32(src[1]) << 8
+		v |= uint32(src[2]) << 16
+		v |= uint32(src[3]) << 24
+		v ^= u
+		dst[0] = byte(v)
+		dst[1] = byte(v >> 8)
+		dst[2] = byte(v >> 16)
+		dst[3] = byte(v >> 24)
+	} else {
+		dst[0] = src[0] ^ byte(u)
+		dst[1] = src[1] ^ byte(u>>8)
+		dst[2] = src[2] ^ byte(u>>16)
+		dst[3] = src[3] ^ byte(u>>24)
+	}
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/poly1305.go b/vendor/golang.org/x/crypto/poly1305/poly1305.go
new file mode 100644
index 0000000000..f562fa5712
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/poly1305.go
@@ -0,0 +1,33 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package poly1305 implements Poly1305 one-time message authentication code as
+specified in https://cr.yp.to/mac/poly1305-20050329.pdf.
+
+Poly1305 is a fast, one-time authentication function. It is infeasible for an
+attacker to generate an authenticator for a message without the key. However, a
+key must only be used for a single message. Authenticating two different
+messages with the same key allows an attacker to forge authenticators for other
+messages with the same key.
+
+Poly1305 was originally coupled with AES in order to make Poly1305-AES. AES was
+used with a fixed key in order to generate one-time keys from an nonce.
+However, in this package AES isn't used and the one-time key is specified
+directly.
+*/
+package poly1305 // import "golang.org/x/crypto/poly1305"
+
+import "crypto/subtle"
+
+// TagSize is the size, in bytes, of a poly1305 authenticator.
+const TagSize = 16
+
+// Verify returns true if mac is a valid authenticator for m with the given
+// key.
+func Verify(mac *[16]byte, m []byte, key *[32]byte) bool {
+	var tmp [16]byte
+	Sum(&tmp, m, key)
+	return subtle.ConstantTimeCompare(tmp[:], mac[:]) == 1
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_amd64.go b/vendor/golang.org/x/crypto/poly1305/sum_amd64.go
new file mode 100644
index 0000000000..4dd72fe799
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_amd64.go
@@ -0,0 +1,22 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build amd64,!gccgo,!appengine
+
+package poly1305
+
+// This function is implemented in sum_amd64.s
+//go:noescape
+func poly1305(out *[16]byte, m *byte, mlen uint64, key *[32]byte)
+
+// Sum generates an authenticator for m using a one-time key and puts the
+// 16-byte result into out. Authenticating two different messages with the same
+// key allows an attacker to forge messages at will.
+func Sum(out *[16]byte, m []byte, key *[32]byte) {
+	var mPtr *byte
+	if len(m) > 0 {
+		mPtr = &m[0]
+	}
+	poly1305(out, mPtr, uint64(len(m)), key)
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_amd64.s b/vendor/golang.org/x/crypto/poly1305/sum_amd64.s
new file mode 100644
index 0000000000..2edae63828
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_amd64.s
@@ -0,0 +1,125 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build amd64,!gccgo,!appengine
+
+#include "textflag.h"
+
+#define POLY1305_ADD(msg, h0, h1, h2) \
+	ADDQ 0(msg), h0;  \
+	ADCQ 8(msg), h1;  \
+	ADCQ $1, h2;      \
+	LEAQ 16(msg), msg
+
+#define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3) \
+	MOVQ  r0, AX;                  \
+	MULQ  h0;                      \
+	MOVQ  AX, t0;                  \
+	MOVQ  DX, t1;                  \
+	MOVQ  r0, AX;                  \
+	MULQ  h1;                      \
+	ADDQ  AX, t1;                  \
+	ADCQ  $0, DX;                  \
+	MOVQ  r0, t2;                  \
+	IMULQ h2, t2;                  \
+	ADDQ  DX, t2;                  \
+	                               \
+	MOVQ  r1, AX;                  \
+	MULQ  h0;                      \
+	ADDQ  AX, t1;                  \
+	ADCQ  $0, DX;                  \
+	MOVQ  DX, h0;                  \
+	MOVQ  r1, t3;                  \
+	IMULQ h2, t3;                  \
+	MOVQ  r1, AX;                  \
+	MULQ  h1;                      \
+	ADDQ  AX, t2;                  \
+	ADCQ  DX, t3;                  \
+	ADDQ  h0, t2;                  \
+	ADCQ  $0, t3;                  \
+	                               \
+	MOVQ  t0, h0;                  \
+	MOVQ  t1, h1;                  \
+	MOVQ  t2, h2;                  \
+	ANDQ  $3, h2;                  \
+	MOVQ  t2, t0;                  \
+	ANDQ  $0xFFFFFFFFFFFFFFFC, t0; \
+	ADDQ  t0, h0;                  \
+	ADCQ  t3, h1;                  \
+	ADCQ  $0, h2;                  \
+	SHRQ  $2, t3, t2;              \
+	SHRQ  $2, t3;                  \
+	ADDQ  t2, h0;                  \
+	ADCQ  t3, h1;                  \
+	ADCQ  $0, h2
+
+DATA ·poly1305Mask<>+0x00(SB)/8, $0x0FFFFFFC0FFFFFFF
+DATA ·poly1305Mask<>+0x08(SB)/8, $0x0FFFFFFC0FFFFFFC
+GLOBL ·poly1305Mask<>(SB), RODATA, $16
+
+// func poly1305(out *[16]byte, m *byte, mlen uint64, key *[32]key)
+TEXT ·poly1305(SB), $0-32
+	MOVQ out+0(FP), DI
+	MOVQ m+8(FP), SI
+	MOVQ mlen+16(FP), R15
+	MOVQ key+24(FP), AX
+
+	MOVQ 0(AX), R11
+	MOVQ 8(AX), R12
+	ANDQ ·poly1305Mask<>(SB), R11   // r0
+	ANDQ ·poly1305Mask<>+8(SB), R12 // r1
+	XORQ R8, R8                    // h0
+	XORQ R9, R9                    // h1
+	XORQ R10, R10                  // h2
+
+	CMPQ R15, $16
+	JB   bytes_between_0_and_15
+
+loop:
+	POLY1305_ADD(SI, R8, R9, R10)
+
+multiply:
+	POLY1305_MUL(R8, R9, R10, R11, R12, BX, CX, R13, R14)
+	SUBQ $16, R15
+	CMPQ R15, $16
+	JAE  loop
+
+bytes_between_0_and_15:
+	TESTQ R15, R15
+	JZ    done
+	MOVQ  $1, BX
+	XORQ  CX, CX
+	XORQ  R13, R13
+	ADDQ  R15, SI
+
+flush_buffer:
+	SHLQ $8, BX, CX
+	SHLQ $8, BX
+	MOVB -1(SI), R13
+	XORQ R13, BX
+	DECQ SI
+	DECQ R15
+	JNZ  flush_buffer
+
+	ADDQ BX, R8
+	ADCQ CX, R9
+	ADCQ $0, R10
+	MOVQ $16, R15
+	JMP  multiply
+
+done:
+	MOVQ    R8, AX
+	MOVQ    R9, BX
+	SUBQ    $0xFFFFFFFFFFFFFFFB, AX
+	SBBQ    $0xFFFFFFFFFFFFFFFF, BX
+	SBBQ    $3, R10
+	CMOVQCS R8, AX
+	CMOVQCS R9, BX
+	MOVQ    key+24(FP), R8
+	ADDQ    16(R8), AX
+	ADCQ    24(R8), BX
+
+	MOVQ AX, 0(DI)
+	MOVQ BX, 8(DI)
+	RET
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_arm.go b/vendor/golang.org/x/crypto/poly1305/sum_arm.go
new file mode 100644
index 0000000000..5dc321c2f3
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_arm.go
@@ -0,0 +1,22 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build arm,!gccgo,!appengine,!nacl
+
+package poly1305
+
+// This function is implemented in sum_arm.s
+//go:noescape
+func poly1305_auth_armv6(out *[16]byte, m *byte, mlen uint32, key *[32]byte)
+
+// Sum generates an authenticator for m using a one-time key and puts the
+// 16-byte result into out. Authenticating two different messages with the same
+// key allows an attacker to forge messages at will.
+func Sum(out *[16]byte, m []byte, key *[32]byte) {
+	var mPtr *byte
+	if len(m) > 0 {
+		mPtr = &m[0]
+	}
+	poly1305_auth_armv6(out, mPtr, uint32(len(m)), key)
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_arm.s b/vendor/golang.org/x/crypto/poly1305/sum_arm.s
new file mode 100644
index 0000000000..f70b4ac484
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_arm.s
@@ -0,0 +1,427 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build arm,!gccgo,!appengine,!nacl
+
+#include "textflag.h"
+
+// This code was translated into a form compatible with 5a from the public
+// domain source by Andrew Moon: github.com/floodyberry/poly1305-opt/blob/master/app/extensions/poly1305.
+
+DATA ·poly1305_init_constants_armv6<>+0x00(SB)/4, $0x3ffffff
+DATA ·poly1305_init_constants_armv6<>+0x04(SB)/4, $0x3ffff03
+DATA ·poly1305_init_constants_armv6<>+0x08(SB)/4, $0x3ffc0ff
+DATA ·poly1305_init_constants_armv6<>+0x0c(SB)/4, $0x3f03fff
+DATA ·poly1305_init_constants_armv6<>+0x10(SB)/4, $0x00fffff
+GLOBL ·poly1305_init_constants_armv6<>(SB), 8, $20
+
+// Warning: the linker may use R11 to synthesize certain instructions. Please
+// take care and verify that no synthetic instructions use it.
+
+TEXT poly1305_init_ext_armv6<>(SB), NOSPLIT, $0
+	// Needs 16 bytes of stack and 64 bytes of space pointed to by R0.  (It
+	// might look like it's only 60 bytes of space but the final four bytes
+	// will be written by another function.) We need to skip over four
+	// bytes of stack because that's saving the value of 'g'.
+	ADD       $4, R13, R8
+	MOVM.IB   [R4-R7], (R8)
+	MOVM.IA.W (R1), [R2-R5]
+	MOVW      $·poly1305_init_constants_armv6<>(SB), R7
+	MOVW      R2, R8
+	MOVW      R2>>26, R9
+	MOVW      R3>>20, g
+	MOVW      R4>>14, R11
+	MOVW      R5>>8, R12
+	ORR       R3<<6, R9, R9
+	ORR       R4<<12, g, g
+	ORR       R5<<18, R11, R11
+	MOVM.IA   (R7), [R2-R6]
+	AND       R8, R2, R2
+	AND       R9, R3, R3
+	AND       g, R4, R4
+	AND       R11, R5, R5
+	AND       R12, R6, R6
+	MOVM.IA.W [R2-R6], (R0)
+	EOR       R2, R2, R2
+	EOR       R3, R3, R3
+	EOR       R4, R4, R4
+	EOR       R5, R5, R5
+	EOR       R6, R6, R6
+	MOVM.IA.W [R2-R6], (R0)
+	MOVM.IA.W (R1), [R2-R5]
+	MOVM.IA   [R2-R6], (R0)
+	ADD       $20, R13, R0
+	MOVM.DA   (R0), [R4-R7]
+	RET
+
+#define MOVW_UNALIGNED(Rsrc, Rdst, Rtmp, offset) \
+	MOVBU (offset+0)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+0)(Rdst); \
+	MOVBU (offset+1)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+1)(Rdst); \
+	MOVBU (offset+2)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+2)(Rdst); \
+	MOVBU (offset+3)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+3)(Rdst)
+
+TEXT poly1305_blocks_armv6<>(SB), NOSPLIT, $0
+	// Needs 24 bytes of stack for saved registers and then 88 bytes of
+	// scratch space after that. We assume that 24 bytes at (R13) have
+	// already been used: four bytes for the link register saved in the
+	// prelude of poly1305_auth_armv6, four bytes for saving the value of g
+	// in that function and 16 bytes of scratch space used around
+	// poly1305_finish_ext_armv6_skip1.
+	ADD     $24, R13, R12
+	MOVM.IB [R4-R8, R14], (R12)
+	MOVW    R0, 88(R13)
+	MOVW    R1, 92(R13)
+	MOVW    R2, 96(R13)
+	MOVW    R1, R14
+	MOVW    R2, R12
+	MOVW    56(R0), R8
+	WORD    $0xe1180008                // TST R8, R8 not working see issue 5921
+	EOR     R6, R6, R6
+	MOVW.EQ $(1<<24), R6
+	MOVW    R6, 84(R13)
+	ADD     $116, R13, g
+	MOVM.IA (R0), [R0-R9]
+	MOVM.IA [R0-R4], (g)
+	CMP     $16, R12
+	BLO     poly1305_blocks_armv6_done
+
+poly1305_blocks_armv6_mainloop:
+	WORD    $0xe31e0003                            // TST R14, #3 not working see issue 5921
+	BEQ     poly1305_blocks_armv6_mainloop_aligned
+	ADD     $100, R13, g
+	MOVW_UNALIGNED(R14, g, R0, 0)
+	MOVW_UNALIGNED(R14, g, R0, 4)
+	MOVW_UNALIGNED(R14, g, R0, 8)
+	MOVW_UNALIGNED(R14, g, R0, 12)
+	MOVM.IA (g), [R0-R3]
+	ADD     $16, R14
+	B       poly1305_blocks_armv6_mainloop_loaded
+
+poly1305_blocks_armv6_mainloop_aligned:
+	MOVM.IA.W (R14), [R0-R3]
+
+poly1305_blocks_armv6_mainloop_loaded:
+	MOVW    R0>>26, g
+	MOVW    R1>>20, R11
+	MOVW    R2>>14, R12
+	MOVW    R14, 92(R13)
+	MOVW    R3>>8, R4
+	ORR     R1<<6, g, g
+	ORR     R2<<12, R11, R11
+	ORR     R3<<18, R12, R12
+	BIC     $0xfc000000, R0, R0
+	BIC     $0xfc000000, g, g
+	MOVW    84(R13), R3
+	BIC     $0xfc000000, R11, R11
+	BIC     $0xfc000000, R12, R12
+	ADD     R0, R5, R5
+	ADD     g, R6, R6
+	ORR     R3, R4, R4
+	ADD     R11, R7, R7
+	ADD     $116, R13, R14
+	ADD     R12, R8, R8
+	ADD     R4, R9, R9
+	MOVM.IA (R14), [R0-R4]
+	MULLU   R4, R5, (R11, g)
+	MULLU   R3, R5, (R14, R12)
+	MULALU  R3, R6, (R11, g)
+	MULALU  R2, R6, (R14, R12)
+	MULALU  R2, R7, (R11, g)
+	MULALU  R1, R7, (R14, R12)
+	ADD     R4<<2, R4, R4
+	ADD     R3<<2, R3, R3
+	MULALU  R1, R8, (R11, g)
+	MULALU  R0, R8, (R14, R12)
+	MULALU  R0, R9, (R11, g)
+	MULALU  R4, R9, (R14, R12)
+	MOVW    g, 76(R13)
+	MOVW    R11, 80(R13)
+	MOVW    R12, 68(R13)
+	MOVW    R14, 72(R13)
+	MULLU   R2, R5, (R11, g)
+	MULLU   R1, R5, (R14, R12)
+	MULALU  R1, R6, (R11, g)
+	MULALU  R0, R6, (R14, R12)
+	MULALU  R0, R7, (R11, g)
+	MULALU  R4, R7, (R14, R12)
+	ADD     R2<<2, R2, R2
+	ADD     R1<<2, R1, R1
+	MULALU  R4, R8, (R11, g)
+	MULALU  R3, R8, (R14, R12)
+	MULALU  R3, R9, (R11, g)
+	MULALU  R2, R9, (R14, R12)
+	MOVW    g, 60(R13)
+	MOVW    R11, 64(R13)
+	MOVW    R12, 52(R13)
+	MOVW    R14, 56(R13)
+	MULLU   R0, R5, (R11, g)
+	MULALU  R4, R6, (R11, g)
+	MULALU  R3, R7, (R11, g)
+	MULALU  R2, R8, (R11, g)
+	MULALU  R1, R9, (R11, g)
+	ADD     $52, R13, R0
+	MOVM.IA (R0), [R0-R7]
+	MOVW    g>>26, R12
+	MOVW    R4>>26, R14
+	ORR     R11<<6, R12, R12
+	ORR     R5<<6, R14, R14
+	BIC     $0xfc000000, g, g
+	BIC     $0xfc000000, R4, R4
+	ADD.S   R12, R0, R0
+	ADC     $0, R1, R1
+	ADD.S   R14, R6, R6
+	ADC     $0, R7, R7
+	MOVW    R0>>26, R12
+	MOVW    R6>>26, R14
+	ORR     R1<<6, R12, R12
+	ORR     R7<<6, R14, R14
+	BIC     $0xfc000000, R0, R0
+	BIC     $0xfc000000, R6, R6
+	ADD     R14<<2, R14, R14
+	ADD.S   R12, R2, R2
+	ADC     $0, R3, R3
+	ADD     R14, g, g
+	MOVW    R2>>26, R12
+	MOVW    g>>26, R14
+	ORR     R3<<6, R12, R12
+	BIC     $0xfc000000, g, R5
+	BIC     $0xfc000000, R2, R7
+	ADD     R12, R4, R4
+	ADD     R14, R0, R0
+	MOVW    R4>>26, R12
+	BIC     $0xfc000000, R4, R8
+	ADD     R12, R6, R9
+	MOVW    96(R13), R12
+	MOVW    92(R13), R14
+	MOVW    R0, R6
+	CMP     $32, R12
+	SUB     $16, R12, R12
+	MOVW    R12, 96(R13)
+	BHS     poly1305_blocks_armv6_mainloop
+
+poly1305_blocks_armv6_done:
+	MOVW    88(R13), R12
+	MOVW    R5, 20(R12)
+	MOVW    R6, 24(R12)
+	MOVW    R7, 28(R12)
+	MOVW    R8, 32(R12)
+	MOVW    R9, 36(R12)
+	ADD     $48, R13, R0
+	MOVM.DA (R0), [R4-R8, R14]
+	RET
+
+#define MOVHUP_UNALIGNED(Rsrc, Rdst, Rtmp) \
+	MOVBU.P 1(Rsrc), Rtmp; \
+	MOVBU.P Rtmp, 1(Rdst); \
+	MOVBU.P 1(Rsrc), Rtmp; \
+	MOVBU.P Rtmp, 1(Rdst)
+
+#define MOVWP_UNALIGNED(Rsrc, Rdst, Rtmp) \
+	MOVHUP_UNALIGNED(Rsrc, Rdst, Rtmp); \
+	MOVHUP_UNALIGNED(Rsrc, Rdst, Rtmp)
+
+// func poly1305_auth_armv6(out *[16]byte, m *byte, mlen uint32, key *[32]key)
+TEXT ·poly1305_auth_armv6(SB), $196-16
+	// The value 196, just above, is the sum of 64 (the size of the context
+	// structure) and 132 (the amount of stack needed).
+	//
+	// At this point, the stack pointer (R13) has been moved down. It
+	// points to the saved link register and there's 196 bytes of free
+	// space above it.
+	//
+	// The stack for this function looks like:
+	//
+	// +---------------------
+	// |
+	// | 64 bytes of context structure
+	// |
+	// +---------------------
+	// |
+	// | 112 bytes for poly1305_blocks_armv6
+	// |
+	// +---------------------
+	// | 16 bytes of final block, constructed at
+	// | poly1305_finish_ext_armv6_skip8
+	// +---------------------
+	// | four bytes of saved 'g'
+	// +---------------------
+	// | lr, saved by prelude    <- R13 points here
+	// +---------------------
+	MOVW g, 4(R13)
+
+	MOVW out+0(FP), R4
+	MOVW m+4(FP), R5
+	MOVW mlen+8(FP), R6
+	MOVW key+12(FP), R7
+
+	ADD  $136, R13, R0 // 136 = 4 + 4 + 16 + 112
+	MOVW R7, R1
+
+	// poly1305_init_ext_armv6 will write to the stack from R13+4, but
+	// that's ok because none of the other values have been written yet.
+	BL    poly1305_init_ext_armv6<>(SB)
+	BIC.S $15, R6, R2
+	BEQ   poly1305_auth_armv6_noblocks
+	ADD   $136, R13, R0
+	MOVW  R5, R1
+	ADD   R2, R5, R5
+	SUB   R2, R6, R6
+	BL    poly1305_blocks_armv6<>(SB)
+
+poly1305_auth_armv6_noblocks:
+	ADD  $136, R13, R0
+	MOVW R5, R1
+	MOVW R6, R2
+	MOVW R4, R3
+
+	MOVW  R0, R5
+	MOVW  R1, R6
+	MOVW  R2, R7
+	MOVW  R3, R8
+	AND.S R2, R2, R2
+	BEQ   poly1305_finish_ext_armv6_noremaining
+	EOR   R0, R0
+	ADD   $8, R13, R9                           // 8 = offset to 16 byte scratch space
+	MOVW  R0, (R9)
+	MOVW  R0, 4(R9)
+	MOVW  R0, 8(R9)
+	MOVW  R0, 12(R9)
+	WORD  $0xe3110003                           // TST R1, #3 not working see issue 5921
+	BEQ   poly1305_finish_ext_armv6_aligned
+	WORD  $0xe3120008                           // TST R2, #8 not working see issue 5921
+	BEQ   poly1305_finish_ext_armv6_skip8
+	MOVWP_UNALIGNED(R1, R9, g)
+	MOVWP_UNALIGNED(R1, R9, g)
+
+poly1305_finish_ext_armv6_skip8:
+	WORD $0xe3120004                     // TST $4, R2 not working see issue 5921
+	BEQ  poly1305_finish_ext_armv6_skip4
+	MOVWP_UNALIGNED(R1, R9, g)
+
+poly1305_finish_ext_armv6_skip4:
+	WORD $0xe3120002                     // TST $2, R2 not working see issue 5921
+	BEQ  poly1305_finish_ext_armv6_skip2
+	MOVHUP_UNALIGNED(R1, R9, g)
+	B    poly1305_finish_ext_armv6_skip2
+
+poly1305_finish_ext_armv6_aligned:
+	WORD      $0xe3120008                             // TST R2, #8 not working see issue 5921
+	BEQ       poly1305_finish_ext_armv6_skip8_aligned
+	MOVM.IA.W (R1), [g-R11]
+	MOVM.IA.W [g-R11], (R9)
+
+poly1305_finish_ext_armv6_skip8_aligned:
+	WORD   $0xe3120004                             // TST $4, R2 not working see issue 5921
+	BEQ    poly1305_finish_ext_armv6_skip4_aligned
+	MOVW.P 4(R1), g
+	MOVW.P g, 4(R9)
+
+poly1305_finish_ext_armv6_skip4_aligned:
+	WORD    $0xe3120002                     // TST $2, R2 not working see issue 5921
+	BEQ     poly1305_finish_ext_armv6_skip2
+	MOVHU.P 2(R1), g
+	MOVH.P  g, 2(R9)
+
+poly1305_finish_ext_armv6_skip2:
+	WORD    $0xe3120001                     // TST $1, R2 not working see issue 5921
+	BEQ     poly1305_finish_ext_armv6_skip1
+	MOVBU.P 1(R1), g
+	MOVBU.P g, 1(R9)
+
+poly1305_finish_ext_armv6_skip1:
+	MOVW  $1, R11
+	MOVBU R11, 0(R9)
+	MOVW  R11, 56(R5)
+	MOVW  R5, R0
+	ADD   $8, R13, R1
+	MOVW  $16, R2
+	BL    poly1305_blocks_armv6<>(SB)
+
+poly1305_finish_ext_armv6_noremaining:
+	MOVW      20(R5), R0
+	MOVW      24(R5), R1
+	MOVW      28(R5), R2
+	MOVW      32(R5), R3
+	MOVW      36(R5), R4
+	MOVW      R4>>26, R12
+	BIC       $0xfc000000, R4, R4
+	ADD       R12<<2, R12, R12
+	ADD       R12, R0, R0
+	MOVW      R0>>26, R12
+	BIC       $0xfc000000, R0, R0
+	ADD       R12, R1, R1
+	MOVW      R1>>26, R12
+	BIC       $0xfc000000, R1, R1
+	ADD       R12, R2, R2
+	MOVW      R2>>26, R12
+	BIC       $0xfc000000, R2, R2
+	ADD       R12, R3, R3
+	MOVW      R3>>26, R12
+	BIC       $0xfc000000, R3, R3
+	ADD       R12, R4, R4
+	ADD       $5, R0, R6
+	MOVW      R6>>26, R12
+	BIC       $0xfc000000, R6, R6
+	ADD       R12, R1, R7
+	MOVW      R7>>26, R12
+	BIC       $0xfc000000, R7, R7
+	ADD       R12, R2, g
+	MOVW      g>>26, R12
+	BIC       $0xfc000000, g, g
+	ADD       R12, R3, R11
+	MOVW      $-(1<<26), R12
+	ADD       R11>>26, R12, R12
+	BIC       $0xfc000000, R11, R11
+	ADD       R12, R4, R9
+	MOVW      R9>>31, R12
+	SUB       $1, R12
+	AND       R12, R6, R6
+	AND       R12, R7, R7
+	AND       R12, g, g
+	AND       R12, R11, R11
+	AND       R12, R9, R9
+	MVN       R12, R12
+	AND       R12, R0, R0
+	AND       R12, R1, R1
+	AND       R12, R2, R2
+	AND       R12, R3, R3
+	AND       R12, R4, R4
+	ORR       R6, R0, R0
+	ORR       R7, R1, R1
+	ORR       g, R2, R2
+	ORR       R11, R3, R3
+	ORR       R9, R4, R4
+	ORR       R1<<26, R0, R0
+	MOVW      R1>>6, R1
+	ORR       R2<<20, R1, R1
+	MOVW      R2>>12, R2
+	ORR       R3<<14, R2, R2
+	MOVW      R3>>18, R3
+	ORR       R4<<8, R3, R3
+	MOVW      40(R5), R6
+	MOVW      44(R5), R7
+	MOVW      48(R5), g
+	MOVW      52(R5), R11
+	ADD.S     R6, R0, R0
+	ADC.S     R7, R1, R1
+	ADC.S     g, R2, R2
+	ADC.S     R11, R3, R3
+	MOVM.IA   [R0-R3], (R8)
+	MOVW      R5, R12
+	EOR       R0, R0, R0
+	EOR       R1, R1, R1
+	EOR       R2, R2, R2
+	EOR       R3, R3, R3
+	EOR       R4, R4, R4
+	EOR       R5, R5, R5
+	EOR       R6, R6, R6
+	EOR       R7, R7, R7
+	MOVM.IA.W [R0-R7], (R12)
+	MOVM.IA   [R0-R7], (R12)
+	MOVW      4(R13), g
+	RET
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_ref.go b/vendor/golang.org/x/crypto/poly1305/sum_ref.go
new file mode 100644
index 0000000000..b2805a5ca1
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_ref.go
@@ -0,0 +1,141 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !amd64,!arm gccgo appengine nacl
+
+package poly1305
+
+import "encoding/binary"
+
+// Sum generates an authenticator for msg using a one-time key and puts the
+// 16-byte result into out. Authenticating two different messages with the same
+// key allows an attacker to forge messages at will.
+func Sum(out *[TagSize]byte, msg []byte, key *[32]byte) {
+	var (
+		h0, h1, h2, h3, h4 uint32 // the hash accumulators
+		r0, r1, r2, r3, r4 uint64 // the r part of the key
+	)
+
+	r0 = uint64(binary.LittleEndian.Uint32(key[0:]) & 0x3ffffff)
+	r1 = uint64((binary.LittleEndian.Uint32(key[3:]) >> 2) & 0x3ffff03)
+	r2 = uint64((binary.LittleEndian.Uint32(key[6:]) >> 4) & 0x3ffc0ff)
+	r3 = uint64((binary.LittleEndian.Uint32(key[9:]) >> 6) & 0x3f03fff)
+	r4 = uint64((binary.LittleEndian.Uint32(key[12:]) >> 8) & 0x00fffff)
+
+	R1, R2, R3, R4 := r1*5, r2*5, r3*5, r4*5
+
+	for len(msg) >= TagSize {
+		// h += msg
+		h0 += binary.LittleEndian.Uint32(msg[0:]) & 0x3ffffff
+		h1 += (binary.LittleEndian.Uint32(msg[3:]) >> 2) & 0x3ffffff
+		h2 += (binary.LittleEndian.Uint32(msg[6:]) >> 4) & 0x3ffffff
+		h3 += (binary.LittleEndian.Uint32(msg[9:]) >> 6) & 0x3ffffff
+		h4 += (binary.LittleEndian.Uint32(msg[12:]) >> 8) | (1 << 24)
+
+		// h *= r
+		d0 := (uint64(h0) * r0) + (uint64(h1) * R4) + (uint64(h2) * R3) + (uint64(h3) * R2) + (uint64(h4) * R1)
+		d1 := (d0 >> 26) + (uint64(h0) * r1) + (uint64(h1) * r0) + (uint64(h2) * R4) + (uint64(h3) * R3) + (uint64(h4) * R2)
+		d2 := (d1 >> 26) + (uint64(h0) * r2) + (uint64(h1) * r1) + (uint64(h2) * r0) + (uint64(h3) * R4) + (uint64(h4) * R3)
+		d3 := (d2 >> 26) + (uint64(h0) * r3) + (uint64(h1) * r2) + (uint64(h2) * r1) + (uint64(h3) * r0) + (uint64(h4) * R4)
+		d4 := (d3 >> 26) + (uint64(h0) * r4) + (uint64(h1) * r3) + (uint64(h2) * r2) + (uint64(h3) * r1) + (uint64(h4) * r0)
+
+		// h %= p
+		h0 = uint32(d0) & 0x3ffffff
+		h1 = uint32(d1) & 0x3ffffff
+		h2 = uint32(d2) & 0x3ffffff
+		h3 = uint32(d3) & 0x3ffffff
+		h4 = uint32(d4) & 0x3ffffff
+
+		h0 += uint32(d4>>26) * 5
+		h1 += h0 >> 26
+		h0 = h0 & 0x3ffffff
+
+		msg = msg[TagSize:]
+	}
+
+	if len(msg) > 0 {
+		var block [TagSize]byte
+		off := copy(block[:], msg)
+		block[off] = 0x01
+
+		// h += msg
+		h0 += binary.LittleEndian.Uint32(block[0:]) & 0x3ffffff
+		h1 += (binary.LittleEndian.Uint32(block[3:]) >> 2) & 0x3ffffff
+		h2 += (binary.LittleEndian.Uint32(block[6:]) >> 4) & 0x3ffffff
+		h3 += (binary.LittleEndian.Uint32(block[9:]) >> 6) & 0x3ffffff
+		h4 += (binary.LittleEndian.Uint32(block[12:]) >> 8)
+
+		// h *= r
+		d0 := (uint64(h0) * r0) + (uint64(h1) * R4) + (uint64(h2) * R3) + (uint64(h3) * R2) + (uint64(h4) * R1)
+		d1 := (d0 >> 26) + (uint64(h0) * r1) + (uint64(h1) * r0) + (uint64(h2) * R4) + (uint64(h3) * R3) + (uint64(h4) * R2)
+		d2 := (d1 >> 26) + (uint64(h0) * r2) + (uint64(h1) * r1) + (uint64(h2) * r0) + (uint64(h3) * R4) + (uint64(h4) * R3)
+		d3 := (d2 >> 26) + (uint64(h0) * r3) + (uint64(h1) * r2) + (uint64(h2) * r1) + (uint64(h3) * r0) + (uint64(h4) * R4)
+		d4 := (d3 >> 26) + (uint64(h0) * r4) + (uint64(h1) * r3) + (uint64(h2) * r2) + (uint64(h3) * r1) + (uint64(h4) * r0)
+
+		// h %= p
+		h0 = uint32(d0) & 0x3ffffff
+		h1 = uint32(d1) & 0x3ffffff
+		h2 = uint32(d2) & 0x3ffffff
+		h3 = uint32(d3) & 0x3ffffff
+		h4 = uint32(d4) & 0x3ffffff
+
+		h0 += uint32(d4>>26) * 5
+		h1 += h0 >> 26
+		h0 = h0 & 0x3ffffff
+	}
+
+	// h %= p reduction
+	h2 += h1 >> 26
+	h1 &= 0x3ffffff
+	h3 += h2 >> 26
+	h2 &= 0x3ffffff
+	h4 += h3 >> 26
+	h3 &= 0x3ffffff
+	h0 += 5 * (h4 >> 26)
+	h4 &= 0x3ffffff
+	h1 += h0 >> 26
+	h0 &= 0x3ffffff
+
+	// h - p
+	t0 := h0 + 5
+	t1 := h1 + (t0 >> 26)
+	t2 := h2 + (t1 >> 26)
+	t3 := h3 + (t2 >> 26)
+	t4 := h4 + (t3 >> 26) - (1 << 26)
+	t0 &= 0x3ffffff
+	t1 &= 0x3ffffff
+	t2 &= 0x3ffffff
+	t3 &= 0x3ffffff
+
+	// select h if h < p else h - p
+	t_mask := (t4 >> 31) - 1
+	h_mask := ^t_mask
+	h0 = (h0 & h_mask) | (t0 & t_mask)
+	h1 = (h1 & h_mask) | (t1 & t_mask)
+	h2 = (h2 & h_mask) | (t2 & t_mask)
+	h3 = (h3 & h_mask) | (t3 & t_mask)
+	h4 = (h4 & h_mask) | (t4 & t_mask)
+
+	// h %= 2^128
+	h0 |= h1 << 26
+	h1 = ((h1 >> 6) | (h2 << 20))
+	h2 = ((h2 >> 12) | (h3 << 14))
+	h3 = ((h3 >> 18) | (h4 << 8))
+
+	// s: the s part of the key
+	// tag = (h + s) % (2^128)
+	t := uint64(h0) + uint64(binary.LittleEndian.Uint32(key[16:]))
+	h0 = uint32(t)
+	t = uint64(h1) + uint64(binary.LittleEndian.Uint32(key[20:])) + (t >> 32)
+	h1 = uint32(t)
+	t = uint64(h2) + uint64(binary.LittleEndian.Uint32(key[24:])) + (t >> 32)
+	h2 = uint32(t)
+	t = uint64(h3) + uint64(binary.LittleEndian.Uint32(key[28:])) + (t >> 32)
+	h3 = uint32(t)
+
+	binary.LittleEndian.PutUint32(out[0:], h0)
+	binary.LittleEndian.PutUint32(out[4:], h1)
+	binary.LittleEndian.PutUint32(out[8:], h2)
+	binary.LittleEndian.PutUint32(out[12:], h3)
+}
diff --git a/vendor/golang.org/x/crypto/ssh/certs.go b/vendor/golang.org/x/crypto/ssh/certs.go
index b1f0220781..42106f3f2c 100644
--- a/vendor/golang.org/x/crypto/ssh/certs.go
+++ b/vendor/golang.org/x/crypto/ssh/certs.go
@@ -44,7 +44,9 @@ type Signature struct {
 const CertTimeInfinity = 1<<64 - 1
 
 // An Certificate represents an OpenSSH certificate as defined in
-// [PROTOCOL.certkeys]?rev=1.8.
+// [PROTOCOL.certkeys]?rev=1.8. The Certificate type implements the
+// PublicKey interface, so it can be unmarshaled using
+// ParsePublicKey.
 type Certificate struct {
 	Nonce           []byte
 	Key             PublicKey
@@ -340,10 +342,10 @@ func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permis
 // the signature of the certificate.
 func (c *CertChecker) CheckCert(principal string, cert *Certificate) error {
 	if c.IsRevoked != nil && c.IsRevoked(cert) {
-		return fmt.Errorf("ssh: certicate serial %d revoked", cert.Serial)
+		return fmt.Errorf("ssh: certificate serial %d revoked", cert.Serial)
 	}
 
-	for opt, _ := range cert.CriticalOptions {
+	for opt := range cert.CriticalOptions {
 		// sourceAddressCriticalOption will be enforced by
 		// serverAuthenticate
 		if opt == sourceAddressCriticalOption {
diff --git a/vendor/golang.org/x/crypto/ssh/channel.go b/vendor/golang.org/x/crypto/ssh/channel.go
index 195530ea0d..c0834c00df 100644
--- a/vendor/golang.org/x/crypto/ssh/channel.go
+++ b/vendor/golang.org/x/crypto/ssh/channel.go
@@ -205,32 +205,32 @@ type channel struct {
 
 // writePacket sends a packet. If the packet is a channel close, it updates
 // sentClose. This method takes the lock c.writeMu.
-func (c *channel) writePacket(packet []byte) error {
-	c.writeMu.Lock()
-	if c.sentClose {
-		c.writeMu.Unlock()
+func (ch *channel) writePacket(packet []byte) error {
+	ch.writeMu.Lock()
+	if ch.sentClose {
+		ch.writeMu.Unlock()
 		return io.EOF
 	}
-	c.sentClose = (packet[0] == msgChannelClose)
-	err := c.mux.conn.writePacket(packet)
-	c.writeMu.Unlock()
+	ch.sentClose = (packet[0] == msgChannelClose)
+	err := ch.mux.conn.writePacket(packet)
+	ch.writeMu.Unlock()
 	return err
 }
 
-func (c *channel) sendMessage(msg interface{}) error {
+func (ch *channel) sendMessage(msg interface{}) error {
 	if debugMux {
-		log.Printf("send(%d): %#v", c.mux.chanList.offset, msg)
+		log.Printf("send(%d): %#v", ch.mux.chanList.offset, msg)
 	}
 
 	p := Marshal(msg)
-	binary.BigEndian.PutUint32(p[1:], c.remoteId)
-	return c.writePacket(p)
+	binary.BigEndian.PutUint32(p[1:], ch.remoteId)
+	return ch.writePacket(p)
 }
 
 // WriteExtended writes data to a specific extended stream. These streams are
 // used, for example, for stderr.
-func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err error) {
-	if c.sentEOF {
+func (ch *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err error) {
+	if ch.sentEOF {
 		return 0, io.EOF
 	}
 	// 1 byte message type, 4 bytes remoteId, 4 bytes data length
@@ -241,16 +241,16 @@ func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err er
 		opCode = msgChannelExtendedData
 	}
 
-	c.writeMu.Lock()
-	packet := c.packetPool[extendedCode]
+	ch.writeMu.Lock()
+	packet := ch.packetPool[extendedCode]
 	// We don't remove the buffer from packetPool, so
 	// WriteExtended calls from different goroutines will be
 	// flagged as errors by the race detector.
-	c.writeMu.Unlock()
+	ch.writeMu.Unlock()
 
 	for len(data) > 0 {
-		space := min(c.maxRemotePayload, len(data))
-		if space, err = c.remoteWin.reserve(space); err != nil {
+		space := min(ch.maxRemotePayload, len(data))
+		if space, err = ch.remoteWin.reserve(space); err != nil {
 			return n, err
 		}
 		if want := headerLength + space; uint32(cap(packet)) < want {
@@ -262,13 +262,13 @@ func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err er
 		todo := data[:space]
 
 		packet[0] = opCode
-		binary.BigEndian.PutUint32(packet[1:], c.remoteId)
+		binary.BigEndian.PutUint32(packet[1:], ch.remoteId)
 		if extendedCode > 0 {
 			binary.BigEndian.PutUint32(packet[5:], uint32(extendedCode))
 		}
 		binary.BigEndian.PutUint32(packet[headerLength-4:], uint32(len(todo)))
 		copy(packet[headerLength:], todo)
-		if err = c.writePacket(packet); err != nil {
+		if err = ch.writePacket(packet); err != nil {
 			return n, err
 		}
 
@@ -276,14 +276,14 @@ func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err er
 		data = data[len(todo):]
 	}
 
-	c.writeMu.Lock()
-	c.packetPool[extendedCode] = packet
-	c.writeMu.Unlock()
+	ch.writeMu.Lock()
+	ch.packetPool[extendedCode] = packet
+	ch.writeMu.Unlock()
 
 	return n, err
 }
 
-func (c *channel) handleData(packet []byte) error {
+func (ch *channel) handleData(packet []byte) error {
 	headerLen := 9
 	isExtendedData := packet[0] == msgChannelExtendedData
 	if isExtendedData {
@@ -303,7 +303,7 @@ func (c *channel) handleData(packet []byte) error {
 	if length == 0 {
 		return nil
 	}
-	if length > c.maxIncomingPayload {
+	if length > ch.maxIncomingPayload {
 		// TODO(hanwen): should send Disconnect?
 		return errors.New("ssh: incoming packet exceeds maximum payload size")
 	}
@@ -313,21 +313,21 @@ func (c *channel) handleData(packet []byte) error {
 		return errors.New("ssh: wrong packet length")
 	}
 
-	c.windowMu.Lock()
-	if c.myWindow < length {
-		c.windowMu.Unlock()
+	ch.windowMu.Lock()
+	if ch.myWindow < length {
+		ch.windowMu.Unlock()
 		// TODO(hanwen): should send Disconnect with reason?
 		return errors.New("ssh: remote side wrote too much")
 	}
-	c.myWindow -= length
-	c.windowMu.Unlock()
+	ch.myWindow -= length
+	ch.windowMu.Unlock()
 
 	if extended == 1 {
-		c.extPending.write(data)
+		ch.extPending.write(data)
 	} else if extended > 0 {
 		// discard other extended data.
 	} else {
-		c.pending.write(data)
+		ch.pending.write(data)
 	}
 	return nil
 }
@@ -384,31 +384,31 @@ func (c *channel) close() {
 // responseMessageReceived is called when a success or failure message is
 // received on a channel to check that such a message is reasonable for the
 // given channel.
-func (c *channel) responseMessageReceived() error {
-	if c.direction == channelInbound {
+func (ch *channel) responseMessageReceived() error {
+	if ch.direction == channelInbound {
 		return errors.New("ssh: channel response message received on inbound channel")
 	}
-	if c.decided {
+	if ch.decided {
 		return errors.New("ssh: duplicate response received for channel")
 	}
-	c.decided = true
+	ch.decided = true
 	return nil
 }
 
-func (c *channel) handlePacket(packet []byte) error {
+func (ch *channel) handlePacket(packet []byte) error {
 	switch packet[0] {
 	case msgChannelData, msgChannelExtendedData:
-		return c.handleData(packet)
+		return ch.handleData(packet)
 	case msgChannelClose:
-		c.sendMessage(channelCloseMsg{PeersId: c.remoteId})
-		c.mux.chanList.remove(c.localId)
-		c.close()
+		ch.sendMessage(channelCloseMsg{PeersID: ch.remoteId})
+		ch.mux.chanList.remove(ch.localId)
+		ch.close()
 		return nil
 	case msgChannelEOF:
 		// RFC 4254 is mute on how EOF affects dataExt messages but
 		// it is logical to signal EOF at the same time.
-		c.extPending.eof()
-		c.pending.eof()
+		ch.extPending.eof()
+		ch.pending.eof()
 		return nil
 	}
 
@@ -419,24 +419,24 @@ func (c *channel) handlePacket(packet []byte) error {
 
 	switch msg := decoded.(type) {
 	case *channelOpenFailureMsg:
-		if err := c.responseMessageReceived(); err != nil {
+		if err := ch.responseMessageReceived(); err != nil {
 			return err
 		}
-		c.mux.chanList.remove(msg.PeersId)
-		c.msg <- msg
+		ch.mux.chanList.remove(msg.PeersID)
+		ch.msg <- msg
 	case *channelOpenConfirmMsg:
-		if err := c.responseMessageReceived(); err != nil {
+		if err := ch.responseMessageReceived(); err != nil {
 			return err
 		}
 		if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 {
 			return fmt.Errorf("ssh: invalid MaxPacketSize %d from peer", msg.MaxPacketSize)
 		}
-		c.remoteId = msg.MyId
-		c.maxRemotePayload = msg.MaxPacketSize
-		c.remoteWin.add(msg.MyWindow)
-		c.msg <- msg
+		ch.remoteId = msg.MyID
+		ch.maxRemotePayload = msg.MaxPacketSize
+		ch.remoteWin.add(msg.MyWindow)
+		ch.msg <- msg
 	case *windowAdjustMsg:
-		if !c.remoteWin.add(msg.AdditionalBytes) {
+		if !ch.remoteWin.add(msg.AdditionalBytes) {
 			return fmt.Errorf("ssh: invalid window update for %d bytes", msg.AdditionalBytes)
 		}
 	case *channelRequestMsg:
@@ -444,12 +444,12 @@ func (c *channel) handlePacket(packet []byte) error {
 			Type:      msg.Request,
 			WantReply: msg.WantReply,
 			Payload:   msg.RequestSpecificData,
-			ch:        c,
+			ch:        ch,
 		}
 
-		c.incomingRequests <- &req
+		ch.incomingRequests <- &req
 	default:
-		c.msg <- msg
+		ch.msg <- msg
 	}
 	return nil
 }
@@ -488,23 +488,23 @@ func (e *extChannel) Read(data []byte) (n int, err error) {
 	return e.ch.ReadExtended(data, e.code)
 }
 
-func (c *channel) Accept() (Channel, <-chan *Request, error) {
-	if c.decided {
+func (ch *channel) Accept() (Channel, <-chan *Request, error) {
+	if ch.decided {
 		return nil, nil, errDecidedAlready
 	}
-	c.maxIncomingPayload = channelMaxPacket
+	ch.maxIncomingPayload = channelMaxPacket
 	confirm := channelOpenConfirmMsg{
-		PeersId:       c.remoteId,
-		MyId:          c.localId,
-		MyWindow:      c.myWindow,
-		MaxPacketSize: c.maxIncomingPayload,
+		PeersID:       ch.remoteId,
+		MyID:          ch.localId,
+		MyWindow:      ch.myWindow,
+		MaxPacketSize: ch.maxIncomingPayload,
 	}
-	c.decided = true
-	if err := c.sendMessage(confirm); err != nil {
+	ch.decided = true
+	if err := ch.sendMessage(confirm); err != nil {
 		return nil, nil, err
 	}
 
-	return c, c.incomingRequests, nil
+	return ch, ch.incomingRequests, nil
 }
 
 func (ch *channel) Reject(reason RejectionReason, message string) error {
@@ -512,7 +512,7 @@ func (ch *channel) Reject(reason RejectionReason, message string) error {
 		return errDecidedAlready
 	}
 	reject := channelOpenFailureMsg{
-		PeersId:  ch.remoteId,
+		PeersID:  ch.remoteId,
 		Reason:   reason,
 		Message:  message,
 		Language: "en",
@@ -541,7 +541,7 @@ func (ch *channel) CloseWrite() error {
 	}
 	ch.sentEOF = true
 	return ch.sendMessage(channelEOFMsg{
-		PeersId: ch.remoteId})
+		PeersID: ch.remoteId})
 }
 
 func (ch *channel) Close() error {
@@ -550,7 +550,7 @@ func (ch *channel) Close() error {
 	}
 
 	return ch.sendMessage(channelCloseMsg{
-		PeersId: ch.remoteId})
+		PeersID: ch.remoteId})
 }
 
 // Extended returns an io.ReadWriter that sends and receives data on the given,
@@ -577,7 +577,7 @@ func (ch *channel) SendRequest(name string, wantReply bool, payload []byte) (boo
 	}
 
 	msg := channelRequestMsg{
-		PeersId:             ch.remoteId,
+		PeersID:             ch.remoteId,
 		Request:             name,
 		WantReply:           wantReply,
 		RequestSpecificData: payload,
@@ -614,11 +614,11 @@ func (ch *channel) ackRequest(ok bool) error {
 	var msg interface{}
 	if !ok {
 		msg = channelRequestFailureMsg{
-			PeersId: ch.remoteId,
+			PeersID: ch.remoteId,
 		}
 	} else {
 		msg = channelRequestSuccessMsg{
-			PeersId: ch.remoteId,
+			PeersID: ch.remoteId,
 		}
 	}
 	return ch.sendMessage(msg)
diff --git a/vendor/golang.org/x/crypto/ssh/cipher.go b/vendor/golang.org/x/crypto/ssh/cipher.go
index aed2b1f017..30a49fdf27 100644
--- a/vendor/golang.org/x/crypto/ssh/cipher.go
+++ b/vendor/golang.org/x/crypto/ssh/cipher.go
@@ -16,6 +16,9 @@ import (
 	"hash"
 	"io"
 	"io/ioutil"
+
+	"golang.org/x/crypto/internal/chacha20"
+	"golang.org/x/crypto/poly1305"
 )
 
 const (
@@ -53,78 +56,78 @@ func newRC4(key, iv []byte) (cipher.Stream, error) {
 	return rc4.NewCipher(key)
 }
 
-type streamCipherMode struct {
-	keySize    int
-	ivSize     int
-	skip       int
-	createFunc func(key, iv []byte) (cipher.Stream, error)
+type cipherMode struct {
+	keySize int
+	ivSize  int
+	create  func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error)
 }
 
-func (c *streamCipherMode) createStream(key, iv []byte) (cipher.Stream, error) {
-	if len(key) < c.keySize {
-		panic("ssh: key length too small for cipher")
-	}
-	if len(iv) < c.ivSize {
-		panic("ssh: iv too small for cipher")
-	}
-
-	stream, err := c.createFunc(key[:c.keySize], iv[:c.ivSize])
-	if err != nil {
-		return nil, err
-	}
+func streamCipherMode(skip int, createFunc func(key, iv []byte) (cipher.Stream, error)) func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+	return func(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+		stream, err := createFunc(key, iv)
+		if err != nil {
+			return nil, err
+		}
 
-	var streamDump []byte
-	if c.skip > 0 {
-		streamDump = make([]byte, 512)
-	}
+		var streamDump []byte
+		if skip > 0 {
+			streamDump = make([]byte, 512)
+		}
 
-	for remainingToDump := c.skip; remainingToDump > 0; {
-		dumpThisTime := remainingToDump
-		if dumpThisTime > len(streamDump) {
-			dumpThisTime = len(streamDump)
+		for remainingToDump := skip; remainingToDump > 0; {
+			dumpThisTime := remainingToDump
+			if dumpThisTime > len(streamDump) {
+				dumpThisTime = len(streamDump)
+			}
+			stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime])
+			remainingToDump -= dumpThisTime
 		}
-		stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime])
-		remainingToDump -= dumpThisTime
-	}
 
-	return stream, nil
+		mac := macModes[algs.MAC].new(macKey)
+		return &streamPacketCipher{
+			mac:       mac,
+			etm:       macModes[algs.MAC].etm,
+			macResult: make([]byte, mac.Size()),
+			cipher:    stream,
+		}, nil
+	}
 }
 
 // cipherModes documents properties of supported ciphers. Ciphers not included
 // are not supported and will not be negotiated, even if explicitly requested in
 // ClientConfig.Crypto.Ciphers.
-var cipherModes = map[string]*streamCipherMode{
+var cipherModes = map[string]*cipherMode{
 	// Ciphers from RFC4344, which introduced many CTR-based ciphers. Algorithms
 	// are defined in the order specified in the RFC.
-	"aes128-ctr": {16, aes.BlockSize, 0, newAESCTR},
-	"aes192-ctr": {24, aes.BlockSize, 0, newAESCTR},
-	"aes256-ctr": {32, aes.BlockSize, 0, newAESCTR},
+	"aes128-ctr": {16, aes.BlockSize, streamCipherMode(0, newAESCTR)},
+	"aes192-ctr": {24, aes.BlockSize, streamCipherMode(0, newAESCTR)},
+	"aes256-ctr": {32, aes.BlockSize, streamCipherMode(0, newAESCTR)},
 
 	// Ciphers from RFC4345, which introduces security-improved arcfour ciphers.
 	// They are defined in the order specified in the RFC.
-	"arcfour128": {16, 0, 1536, newRC4},
-	"arcfour256": {32, 0, 1536, newRC4},
+	"arcfour128": {16, 0, streamCipherMode(1536, newRC4)},
+	"arcfour256": {32, 0, streamCipherMode(1536, newRC4)},
 
 	// Cipher defined in RFC 4253, which describes SSH Transport Layer Protocol.
 	// Note that this cipher is not safe, as stated in RFC 4253: "Arcfour (and
 	// RC4) has problems with weak keys, and should be used with caution."
 	// RFC4345 introduces improved versions of Arcfour.
-	"arcfour": {16, 0, 0, newRC4},
+	"arcfour": {16, 0, streamCipherMode(0, newRC4)},
 
-	// AES-GCM is not a stream cipher, so it is constructed with a
-	// special case. If we add any more non-stream ciphers, we
-	// should invest a cleaner way to do this.
-	gcmCipherID: {16, 12, 0, nil},
+	// AEAD ciphers
+	gcmCipherID:        {16, 12, newGCMCipher},
+	chacha20Poly1305ID: {64, 0, newChaCha20Cipher},
 
 	// CBC mode is insecure and so is not included in the default config.
 	// (See http://www.isg.rhul.ac.uk/~kp/SandPfinal.pdf). If absolutely
 	// needed, it's possible to specify a custom Config to enable it.
 	// You should expect that an active attacker can recover plaintext if
 	// you do.
-	aes128cbcID: {16, aes.BlockSize, 0, nil},
+	aes128cbcID: {16, aes.BlockSize, newAESCBCCipher},
 
-	// 3des-cbc is insecure and is disabled by default.
-	tripledescbcID: {24, des.BlockSize, 0, nil},
+	// 3des-cbc is insecure and is not included in the default
+	// config.
+	tripledescbcID: {24, des.BlockSize, newTripleDESCBCCipher},
 }
 
 // prefixLen is the length of the packet prefix that contains the packet length
@@ -304,7 +307,7 @@ type gcmCipher struct {
 	buf    []byte
 }
 
-func newGCMCipher(iv, key []byte) (packetCipher, error) {
+func newGCMCipher(key, iv, unusedMacKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) {
 	c, err := aes.NewCipher(key)
 	if err != nil {
 		return nil, err
@@ -372,7 +375,7 @@ func (c *gcmCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
 	}
 	length := binary.BigEndian.Uint32(c.prefix[:])
 	if length > maxPacket {
-		return nil, errors.New("ssh: max packet length exceeded.")
+		return nil, errors.New("ssh: max packet length exceeded")
 	}
 
 	if cap(c.buf) < int(length+gcmTagSize) {
@@ -422,7 +425,7 @@ type cbcCipher struct {
 	oracleCamouflage uint32
 }
 
-func newCBCCipher(c cipher.Block, iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+func newCBCCipher(c cipher.Block, key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
 	cbc := &cbcCipher{
 		mac:        macModes[algs.MAC].new(macKey),
 		decrypter:  cipher.NewCBCDecrypter(c, iv),
@@ -436,13 +439,13 @@ func newCBCCipher(c cipher.Block, iv, key, macKey []byte, algs directionAlgorith
 	return cbc, nil
 }
 
-func newAESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+func newAESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
 	c, err := aes.NewCipher(key)
 	if err != nil {
 		return nil, err
 	}
 
-	cbc, err := newCBCCipher(c, iv, key, macKey, algs)
+	cbc, err := newCBCCipher(c, key, iv, macKey, algs)
 	if err != nil {
 		return nil, err
 	}
@@ -450,13 +453,13 @@ func newAESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCi
 	return cbc, nil
 }
 
-func newTripleDESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+func newTripleDESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
 	c, err := des.NewTripleDESCipher(key)
 	if err != nil {
 		return nil, err
 	}
 
-	cbc, err := newCBCCipher(c, iv, key, macKey, algs)
+	cbc, err := newCBCCipher(c, key, iv, macKey, algs)
 	if err != nil {
 		return nil, err
 	}
@@ -548,11 +551,11 @@ func (c *cbcCipher) readPacketLeaky(seqNum uint32, r io.Reader) ([]byte, error)
 		c.packetData = c.packetData[:entirePacketSize]
 	}
 
-	if n, err := io.ReadFull(r, c.packetData[firstBlockLength:]); err != nil {
+	n, err := io.ReadFull(r, c.packetData[firstBlockLength:])
+	if err != nil {
 		return nil, err
-	} else {
-		c.oracleCamouflage -= uint32(n)
 	}
+	c.oracleCamouflage -= uint32(n)
 
 	remainingCrypted := c.packetData[firstBlockLength:macStart]
 	c.decrypter.CryptBlocks(remainingCrypted, remainingCrypted)
@@ -627,3 +630,142 @@ func (c *cbcCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, pack
 
 	return nil
 }
+
+const chacha20Poly1305ID = "chacha20-poly1305@openssh.com"
+
+// chacha20Poly1305Cipher implements the chacha20-poly1305@openssh.com
+// AEAD, which is described here:
+//
+//   https://tools.ietf.org/html/draft-josefsson-ssh-chacha20-poly1305-openssh-00
+//
+// the methods here also implement padding, which RFC4253 Section 6
+// also requires of stream ciphers.
+type chacha20Poly1305Cipher struct {
+	lengthKey  [32]byte
+	contentKey [32]byte
+	buf        []byte
+}
+
+func newChaCha20Cipher(key, unusedIV, unusedMACKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) {
+	if len(key) != 64 {
+		panic(len(key))
+	}
+
+	c := &chacha20Poly1305Cipher{
+		buf: make([]byte, 256),
+	}
+
+	copy(c.contentKey[:], key[:32])
+	copy(c.lengthKey[:], key[32:])
+	return c, nil
+}
+
+// The Poly1305 key is obtained by encrypting 32 0-bytes.
+var chacha20PolyKeyInput [32]byte
+
+func (c *chacha20Poly1305Cipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
+	var counter [16]byte
+	binary.BigEndian.PutUint64(counter[8:], uint64(seqNum))
+
+	var polyKey [32]byte
+	chacha20.XORKeyStream(polyKey[:], chacha20PolyKeyInput[:], &counter, &c.contentKey)
+
+	encryptedLength := c.buf[:4]
+	if _, err := io.ReadFull(r, encryptedLength); err != nil {
+		return nil, err
+	}
+
+	var lenBytes [4]byte
+	chacha20.XORKeyStream(lenBytes[:], encryptedLength, &counter, &c.lengthKey)
+
+	length := binary.BigEndian.Uint32(lenBytes[:])
+	if length > maxPacket {
+		return nil, errors.New("ssh: invalid packet length, packet too large")
+	}
+
+	contentEnd := 4 + length
+	packetEnd := contentEnd + poly1305.TagSize
+	if uint32(cap(c.buf)) < packetEnd {
+		c.buf = make([]byte, packetEnd)
+		copy(c.buf[:], encryptedLength)
+	} else {
+		c.buf = c.buf[:packetEnd]
+	}
+
+	if _, err := io.ReadFull(r, c.buf[4:packetEnd]); err != nil {
+		return nil, err
+	}
+
+	var mac [poly1305.TagSize]byte
+	copy(mac[:], c.buf[contentEnd:packetEnd])
+	if !poly1305.Verify(&mac, c.buf[:contentEnd], &polyKey) {
+		return nil, errors.New("ssh: MAC failure")
+	}
+
+	counter[0] = 1
+
+	plain := c.buf[4:contentEnd]
+	chacha20.XORKeyStream(plain, plain, &counter, &c.contentKey)
+
+	padding := plain[0]
+	if padding < 4 {
+		// padding is a byte, so it automatically satisfies
+		// the maximum size, which is 255.
+		return nil, fmt.Errorf("ssh: illegal padding %d", padding)
+	}
+
+	if int(padding)+1 >= len(plain) {
+		return nil, fmt.Errorf("ssh: padding %d too large", padding)
+	}
+
+	plain = plain[1 : len(plain)-int(padding)]
+
+	return plain, nil
+}
+
+func (c *chacha20Poly1305Cipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, payload []byte) error {
+	var counter [16]byte
+	binary.BigEndian.PutUint64(counter[8:], uint64(seqNum))
+
+	var polyKey [32]byte
+	chacha20.XORKeyStream(polyKey[:], chacha20PolyKeyInput[:], &counter, &c.contentKey)
+
+	// There is no blocksize, so fall back to multiple of 8 byte
+	// padding, as described in RFC 4253, Sec 6.
+	const packetSizeMultiple = 8
+
+	padding := packetSizeMultiple - (1+len(payload))%packetSizeMultiple
+	if padding < 4 {
+		padding += packetSizeMultiple
+	}
+
+	// size (4 bytes), padding (1), payload, padding, tag.
+	totalLength := 4 + 1 + len(payload) + padding + poly1305.TagSize
+	if cap(c.buf) < totalLength {
+		c.buf = make([]byte, totalLength)
+	} else {
+		c.buf = c.buf[:totalLength]
+	}
+
+	binary.BigEndian.PutUint32(c.buf, uint32(1+len(payload)+padding))
+	chacha20.XORKeyStream(c.buf, c.buf[:4], &counter, &c.lengthKey)
+	c.buf[4] = byte(padding)
+	copy(c.buf[5:], payload)
+	packetEnd := 5 + len(payload) + padding
+	if _, err := io.ReadFull(rand, c.buf[5+len(payload):packetEnd]); err != nil {
+		return err
+	}
+
+	counter[0] = 1
+	chacha20.XORKeyStream(c.buf[4:], c.buf[4:packetEnd], &counter, &c.contentKey)
+
+	var mac [poly1305.TagSize]byte
+	poly1305.Sum(&mac, c.buf[:packetEnd], &polyKey)
+
+	copy(c.buf[packetEnd:], mac[:])
+
+	if _, err := w.Write(c.buf); err != nil {
+		return err
+	}
+	return nil
+}
diff --git a/vendor/golang.org/x/crypto/ssh/client_auth.go b/vendor/golang.org/x/crypto/ssh/client_auth.go
index a1252cb9be..5f44b77403 100644
--- a/vendor/golang.org/x/crypto/ssh/client_auth.go
+++ b/vendor/golang.org/x/crypto/ssh/client_auth.go
@@ -11,6 +11,14 @@ import (
 	"io"
 )
 
+type authResult int
+
+const (
+	authFailure authResult = iota
+	authPartialSuccess
+	authSuccess
+)
+
 // clientAuthenticate authenticates with the remote server. See RFC 4252.
 func (c *connection) clientAuthenticate(config *ClientConfig) error {
 	// initiate user auth session
@@ -37,11 +45,12 @@ func (c *connection) clientAuthenticate(config *ClientConfig) error {
 		if err != nil {
 			return err
 		}
-		if ok {
+		if ok == authSuccess {
 			// success
 			return nil
+		} else if ok == authFailure {
+			tried[auth.method()] = true
 		}
-		tried[auth.method()] = true
 		if methods == nil {
 			methods = lastMethods
 		}
@@ -82,7 +91,7 @@ type AuthMethod interface {
 	// If authentication is not successful, a []string of alternative
 	// method names is returned. If the slice is nil, it will be ignored
 	// and the previous set of possible methods will be reused.
-	auth(session []byte, user string, p packetConn, rand io.Reader) (bool, []string, error)
+	auth(session []byte, user string, p packetConn, rand io.Reader) (authResult, []string, error)
 
 	// method returns the RFC 4252 method name.
 	method() string
@@ -91,13 +100,13 @@ type AuthMethod interface {
 // "none" authentication, RFC 4252 section 5.2.
 type noneAuth int
 
-func (n *noneAuth) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (n *noneAuth) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	if err := c.writePacket(Marshal(&userAuthRequestMsg{
 		User:    user,
 		Service: serviceSSH,
 		Method:  "none",
 	})); err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	return handleAuthResponse(c)
@@ -111,7 +120,7 @@ func (n *noneAuth) method() string {
 // a function call, e.g. by prompting the user.
 type passwordCallback func() (password string, err error)
 
-func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	type passwordAuthMsg struct {
 		User     string `sshtype:"50"`
 		Service  string
@@ -125,7 +134,7 @@ func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand
 	// The program may only find out that the user doesn't have a password
 	// when prompting.
 	if err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	if err := c.writePacket(Marshal(&passwordAuthMsg{
@@ -135,7 +144,7 @@ func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand
 		Reply:    false,
 		Password: pw,
 	})); err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	return handleAuthResponse(c)
@@ -178,7 +187,7 @@ func (cb publicKeyCallback) method() string {
 	return "publickey"
 }
 
-func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	// Authentication is performed by sending an enquiry to test if a key is
 	// acceptable to the remote. If the key is acceptable, the client will
 	// attempt to authenticate with the valid key.  If not the client will repeat
@@ -186,13 +195,13 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 
 	signers, err := cb()
 	if err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 	var methods []string
 	for _, signer := range signers {
 		ok, err := validateKey(signer.PublicKey(), user, c)
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 		if !ok {
 			continue
@@ -206,7 +215,7 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 			Method:  cb.method(),
 		}, []byte(pub.Type()), pubKey))
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// manually wrap the serialized signature in a string
@@ -224,24 +233,24 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 		}
 		p := Marshal(&msg)
 		if err := c.writePacket(p); err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
-		var success bool
+		var success authResult
 		success, methods, err = handleAuthResponse(c)
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// If authentication succeeds or the list of available methods does not
 		// contain the "publickey" method, do not attempt to authenticate with any
 		// other keys.  According to RFC 4252 Section 7, the latter can occur when
 		// additional authentication methods are required.
-		if success || !containsMethod(methods, cb.method()) {
+		if success == authSuccess || !containsMethod(methods, cb.method()) {
 			return success, methods, err
 		}
 	}
 
-	return false, methods, nil
+	return authFailure, methods, nil
 }
 
 func containsMethod(methods []string, method string) bool {
@@ -318,28 +327,31 @@ func PublicKeysCallback(getSigners func() (signers []Signer, err error)) AuthMet
 // handleAuthResponse returns whether the preceding authentication request succeeded
 // along with a list of remaining authentication methods to try next and
 // an error if an unexpected response was received.
-func handleAuthResponse(c packetConn) (bool, []string, error) {
+func handleAuthResponse(c packetConn) (authResult, []string, error) {
 	for {
 		packet, err := c.readPacket()
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		switch packet[0] {
 		case msgUserAuthBanner:
 			if err := handleBannerResponse(c, packet); err != nil {
-				return false, nil, err
+				return authFailure, nil, err
 			}
 		case msgUserAuthFailure:
 			var msg userAuthFailureMsg
 			if err := Unmarshal(packet, &msg); err != nil {
-				return false, nil, err
+				return authFailure, nil, err
 			}
-			return false, msg.Methods, nil
+			if msg.PartialSuccess {
+				return authPartialSuccess, msg.Methods, nil
+			}
+			return authFailure, msg.Methods, nil
 		case msgUserAuthSuccess:
-			return true, nil, nil
+			return authSuccess, nil, nil
 		default:
-			return false, nil, unexpectedMessageError(msgUserAuthSuccess, packet[0])
+			return authFailure, nil, unexpectedMessageError(msgUserAuthSuccess, packet[0])
 		}
 	}
 }
@@ -381,7 +393,7 @@ func (cb KeyboardInteractiveChallenge) method() string {
 	return "keyboard-interactive"
 }
 
-func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	type initiateMsg struct {
 		User       string `sshtype:"50"`
 		Service    string
@@ -395,20 +407,20 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		Service: serviceSSH,
 		Method:  "keyboard-interactive",
 	})); err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	for {
 		packet, err := c.readPacket()
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// like handleAuthResponse, but with less options.
 		switch packet[0] {
 		case msgUserAuthBanner:
 			if err := handleBannerResponse(c, packet); err != nil {
-				return false, nil, err
+				return authFailure, nil, err
 			}
 			continue
 		case msgUserAuthInfoRequest:
@@ -416,18 +428,21 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		case msgUserAuthFailure:
 			var msg userAuthFailureMsg
 			if err := Unmarshal(packet, &msg); err != nil {
-				return false, nil, err
+				return authFailure, nil, err
+			}
+			if msg.PartialSuccess {
+				return authPartialSuccess, msg.Methods, nil
 			}
-			return false, msg.Methods, nil
+			return authFailure, msg.Methods, nil
 		case msgUserAuthSuccess:
-			return true, nil, nil
+			return authSuccess, nil, nil
 		default:
-			return false, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
+			return authFailure, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
 		}
 
 		var msg userAuthInfoRequestMsg
 		if err := Unmarshal(packet, &msg); err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// Manually unpack the prompt/echo pairs.
@@ -437,7 +452,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		for i := 0; i < int(msg.NumPrompts); i++ {
 			prompt, r, ok := parseString(rest)
 			if !ok || len(r) == 0 {
-				return false, nil, errors.New("ssh: prompt format error")
+				return authFailure, nil, errors.New("ssh: prompt format error")
 			}
 			prompts = append(prompts, string(prompt))
 			echos = append(echos, r[0] != 0)
@@ -445,16 +460,16 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		}
 
 		if len(rest) != 0 {
-			return false, nil, errors.New("ssh: extra data following keyboard-interactive pairs")
+			return authFailure, nil, errors.New("ssh: extra data following keyboard-interactive pairs")
 		}
 
 		answers, err := cb(msg.User, msg.Instruction, prompts, echos)
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		if len(answers) != len(prompts) {
-			return false, nil, errors.New("ssh: not enough answers from keyboard-interactive callback")
+			return authFailure, nil, errors.New("ssh: not enough answers from keyboard-interactive callback")
 		}
 		responseLength := 1 + 4
 		for _, a := range answers {
@@ -470,7 +485,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		}
 
 		if err := c.writePacket(serialized); err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 	}
 }
@@ -480,10 +495,10 @@ type retryableAuthMethod struct {
 	maxTries   int
 }
 
-func (r *retryableAuthMethod) auth(session []byte, user string, c packetConn, rand io.Reader) (ok bool, methods []string, err error) {
+func (r *retryableAuthMethod) auth(session []byte, user string, c packetConn, rand io.Reader) (ok authResult, methods []string, err error) {
 	for i := 0; r.maxTries <= 0 || i < r.maxTries; i++ {
 		ok, methods, err = r.authMethod.auth(session, user, c, rand)
-		if ok || err != nil { // either success or error terminate
+		if ok != authFailure || err != nil { // either success, partial success or error terminate
 			return ok, methods, err
 		}
 	}
diff --git a/vendor/golang.org/x/crypto/ssh/common.go b/vendor/golang.org/x/crypto/ssh/common.go
index dc39e4d231..04f3620b3d 100644
--- a/vendor/golang.org/x/crypto/ssh/common.go
+++ b/vendor/golang.org/x/crypto/ssh/common.go
@@ -24,11 +24,21 @@ const (
 	serviceSSH      = "ssh-connection"
 )
 
-// supportedCiphers specifies the supported ciphers in preference order.
+// supportedCiphers lists ciphers we support but might not recommend.
 var supportedCiphers = []string{
 	"aes128-ctr", "aes192-ctr", "aes256-ctr",
 	"aes128-gcm@openssh.com",
-	"arcfour256", "arcfour128",
+	chacha20Poly1305ID,
+	"arcfour256", "arcfour128", "arcfour",
+	aes128cbcID,
+	tripledescbcID,
+}
+
+// preferredCiphers specifies the default preference for ciphers.
+var preferredCiphers = []string{
+	"aes128-gcm@openssh.com",
+	chacha20Poly1305ID,
+	"aes128-ctr", "aes192-ctr", "aes256-ctr",
 }
 
 // supportedKexAlgos specifies the supported key-exchange algorithms in
@@ -211,7 +221,7 @@ func (c *Config) SetDefaults() {
 		c.Rand = rand.Reader
 	}
 	if c.Ciphers == nil {
-		c.Ciphers = supportedCiphers
+		c.Ciphers = preferredCiphers
 	}
 	var ciphers []string
 	for _, c := range c.Ciphers {
@@ -242,7 +252,7 @@ func (c *Config) SetDefaults() {
 
 // buildDataSignedForAuth returns the data that is signed in order to prove
 // possession of a private key. See RFC 4252, section 7.
-func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
+func buildDataSignedForAuth(sessionID []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
 	data := struct {
 		Session []byte
 		Type    byte
@@ -253,7 +263,7 @@ func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubK
 		Algo    []byte
 		PubKey  []byte
 	}{
-		sessionId,
+		sessionID,
 		msgUserAuthRequest,
 		req.User,
 		req.Service,
diff --git a/vendor/golang.org/x/crypto/ssh/kex.go b/vendor/golang.org/x/crypto/ssh/kex.go
index f91c2770ed..f34bcc0133 100644
--- a/vendor/golang.org/x/crypto/ssh/kex.go
+++ b/vendor/golang.org/x/crypto/ssh/kex.go
@@ -119,7 +119,7 @@ func (group *dhGroup) Client(c packetConn, randSource io.Reader, magics *handsha
 		return nil, err
 	}
 
-	kInt, err := group.diffieHellman(kexDHReply.Y, x)
+	ki, err := group.diffieHellman(kexDHReply.Y, x)
 	if err != nil {
 		return nil, err
 	}
@@ -129,8 +129,8 @@ func (group *dhGroup) Client(c packetConn, randSource io.Reader, magics *handsha
 	writeString(h, kexDHReply.HostKey)
 	writeInt(h, X)
 	writeInt(h, kexDHReply.Y)
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	return &kexResult{
@@ -164,7 +164,7 @@ func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handsha
 	}
 
 	Y := new(big.Int).Exp(group.g, y, group.p)
-	kInt, err := group.diffieHellman(kexDHInit.X, y)
+	ki, err := group.diffieHellman(kexDHInit.X, y)
 	if err != nil {
 		return nil, err
 	}
@@ -177,8 +177,8 @@ func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handsha
 	writeInt(h, kexDHInit.X)
 	writeInt(h, Y)
 
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	H := h.Sum(nil)
@@ -462,9 +462,9 @@ func (kex *curve25519sha256) Client(c packetConn, rand io.Reader, magics *handsh
 	writeString(h, kp.pub[:])
 	writeString(h, reply.EphemeralPubKey)
 
-	kInt := new(big.Int).SetBytes(secret[:])
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	ki := new(big.Int).SetBytes(secret[:])
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	return &kexResult{
@@ -510,9 +510,9 @@ func (kex *curve25519sha256) Server(c packetConn, rand io.Reader, magics *handsh
 	writeString(h, kexInit.ClientPubKey)
 	writeString(h, kp.pub[:])
 
-	kInt := new(big.Int).SetBytes(secret[:])
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	ki := new(big.Int).SetBytes(secret[:])
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	H := h.Sum(nil)
diff --git a/vendor/golang.org/x/crypto/ssh/keys.go b/vendor/golang.org/x/crypto/ssh/keys.go
index b682c1741b..73697deda6 100644
--- a/vendor/golang.org/x/crypto/ssh/keys.go
+++ b/vendor/golang.org/x/crypto/ssh/keys.go
@@ -276,7 +276,8 @@ type PublicKey interface {
 	Type() string
 
 	// Marshal returns the serialized key data in SSH wire format,
-	// with the name prefix.
+	// with the name prefix. To unmarshal the returned data, use
+	// the ParsePublicKey function.
 	Marshal() []byte
 
 	// Verify that sig is a signature on the given data using this
@@ -363,7 +364,7 @@ func (r *rsaPublicKey) CryptoPublicKey() crypto.PublicKey {
 
 type dsaPublicKey dsa.PublicKey
 
-func (r *dsaPublicKey) Type() string {
+func (k *dsaPublicKey) Type() string {
 	return "ssh-dss"
 }
 
@@ -481,12 +482,12 @@ func (k *dsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) {
 
 type ecdsaPublicKey ecdsa.PublicKey
 
-func (key *ecdsaPublicKey) Type() string {
-	return "ecdsa-sha2-" + key.nistID()
+func (k *ecdsaPublicKey) Type() string {
+	return "ecdsa-sha2-" + k.nistID()
 }
 
-func (key *ecdsaPublicKey) nistID() string {
-	switch key.Params().BitSize {
+func (k *ecdsaPublicKey) nistID() string {
+	switch k.Params().BitSize {
 	case 256:
 		return "nistp256"
 	case 384:
@@ -499,7 +500,7 @@ func (key *ecdsaPublicKey) nistID() string {
 
 type ed25519PublicKey ed25519.PublicKey
 
-func (key ed25519PublicKey) Type() string {
+func (k ed25519PublicKey) Type() string {
 	return KeyAlgoED25519
 }
 
@@ -518,23 +519,23 @@ func parseED25519(in []byte) (out PublicKey, rest []byte, err error) {
 	return (ed25519PublicKey)(key), w.Rest, nil
 }
 
-func (key ed25519PublicKey) Marshal() []byte {
+func (k ed25519PublicKey) Marshal() []byte {
 	w := struct {
 		Name     string
 		KeyBytes []byte
 	}{
 		KeyAlgoED25519,
-		[]byte(key),
+		[]byte(k),
 	}
 	return Marshal(&w)
 }
 
-func (key ed25519PublicKey) Verify(b []byte, sig *Signature) error {
-	if sig.Format != key.Type() {
-		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, key.Type())
+func (k ed25519PublicKey) Verify(b []byte, sig *Signature) error {
+	if sig.Format != k.Type() {
+		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
 
-	edKey := (ed25519.PublicKey)(key)
+	edKey := (ed25519.PublicKey)(k)
 	if ok := ed25519.Verify(edKey, b, sig.Blob); !ok {
 		return errors.New("ssh: signature did not verify")
 	}
@@ -595,9 +596,9 @@ func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) {
 	return (*ecdsaPublicKey)(key), w.Rest, nil
 }
 
-func (key *ecdsaPublicKey) Marshal() []byte {
+func (k *ecdsaPublicKey) Marshal() []byte {
 	// See RFC 5656, section 3.1.
-	keyBytes := elliptic.Marshal(key.Curve, key.X, key.Y)
+	keyBytes := elliptic.Marshal(k.Curve, k.X, k.Y)
 	// ECDSA publickey struct layout should match the struct used by
 	// parseECDSACert in the x/crypto/ssh/agent package.
 	w := struct {
@@ -605,20 +606,20 @@ func (key *ecdsaPublicKey) Marshal() []byte {
 		ID   string
 		Key  []byte
 	}{
-		key.Type(),
-		key.nistID(),
+		k.Type(),
+		k.nistID(),
 		keyBytes,
 	}
 
 	return Marshal(&w)
 }
 
-func (key *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
-	if sig.Format != key.Type() {
-		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, key.Type())
+func (k *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
+	if sig.Format != k.Type() {
+		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
 
-	h := ecHash(key.Curve).New()
+	h := ecHash(k.Curve).New()
 	h.Write(data)
 	digest := h.Sum(nil)
 
@@ -635,7 +636,7 @@ func (key *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
 		return err
 	}
 
-	if ecdsa.Verify((*ecdsa.PublicKey)(key), digest, ecSig.R, ecSig.S) {
+	if ecdsa.Verify((*ecdsa.PublicKey)(k), digest, ecSig.R, ecSig.S) {
 		return nil
 	}
 	return errors.New("ssh: signature did not verify")
@@ -758,7 +759,7 @@ func NewPublicKey(key interface{}) (PublicKey, error) {
 		return (*rsaPublicKey)(key), nil
 	case *ecdsa.PublicKey:
 		if !supportedEllipticCurve(key.Curve) {
-			return nil, errors.New("ssh: only P-256, P-384 and P-521 EC keys are supported.")
+			return nil, errors.New("ssh: only P-256, P-384 and P-521 EC keys are supported")
 		}
 		return (*ecdsaPublicKey)(key), nil
 	case *dsa.PublicKey:
diff --git a/vendor/golang.org/x/crypto/ssh/messages.go b/vendor/golang.org/x/crypto/ssh/messages.go
index c96e1bec59..08d2811730 100644
--- a/vendor/golang.org/x/crypto/ssh/messages.go
+++ b/vendor/golang.org/x/crypto/ssh/messages.go
@@ -162,7 +162,7 @@ const msgChannelOpen = 90
 
 type channelOpenMsg struct {
 	ChanType         string `sshtype:"90"`
-	PeersId          uint32
+	PeersID          uint32
 	PeersWindow      uint32
 	MaxPacketSize    uint32
 	TypeSpecificData []byte `ssh:"rest"`
@@ -173,7 +173,7 @@ const msgChannelData = 94
 
 // Used for debug print outs of packets.
 type channelDataMsg struct {
-	PeersId uint32 `sshtype:"94"`
+	PeersID uint32 `sshtype:"94"`
 	Length  uint32
 	Rest    []byte `ssh:"rest"`
 }
@@ -182,8 +182,8 @@ type channelDataMsg struct {
 const msgChannelOpenConfirm = 91
 
 type channelOpenConfirmMsg struct {
-	PeersId          uint32 `sshtype:"91"`
-	MyId             uint32
+	PeersID          uint32 `sshtype:"91"`
+	MyID             uint32
 	MyWindow         uint32
 	MaxPacketSize    uint32
 	TypeSpecificData []byte `ssh:"rest"`
@@ -193,7 +193,7 @@ type channelOpenConfirmMsg struct {
 const msgChannelOpenFailure = 92
 
 type channelOpenFailureMsg struct {
-	PeersId  uint32 `sshtype:"92"`
+	PeersID  uint32 `sshtype:"92"`
 	Reason   RejectionReason
 	Message  string
 	Language string
@@ -202,7 +202,7 @@ type channelOpenFailureMsg struct {
 const msgChannelRequest = 98
 
 type channelRequestMsg struct {
-	PeersId             uint32 `sshtype:"98"`
+	PeersID             uint32 `sshtype:"98"`
 	Request             string
 	WantReply           bool
 	RequestSpecificData []byte `ssh:"rest"`
@@ -212,28 +212,28 @@ type channelRequestMsg struct {
 const msgChannelSuccess = 99
 
 type channelRequestSuccessMsg struct {
-	PeersId uint32 `sshtype:"99"`
+	PeersID uint32 `sshtype:"99"`
 }
 
 // See RFC 4254, section 5.4.
 const msgChannelFailure = 100
 
 type channelRequestFailureMsg struct {
-	PeersId uint32 `sshtype:"100"`
+	PeersID uint32 `sshtype:"100"`
 }
 
 // See RFC 4254, section 5.3
 const msgChannelClose = 97
 
 type channelCloseMsg struct {
-	PeersId uint32 `sshtype:"97"`
+	PeersID uint32 `sshtype:"97"`
 }
 
 // See RFC 4254, section 5.3
 const msgChannelEOF = 96
 
 type channelEOFMsg struct {
-	PeersId uint32 `sshtype:"96"`
+	PeersID uint32 `sshtype:"96"`
 }
 
 // See RFC 4254, section 4
@@ -263,7 +263,7 @@ type globalRequestFailureMsg struct {
 const msgChannelWindowAdjust = 93
 
 type windowAdjustMsg struct {
-	PeersId         uint32 `sshtype:"93"`
+	PeersID         uint32 `sshtype:"93"`
 	AdditionalBytes uint32
 }
 
diff --git a/vendor/golang.org/x/crypto/ssh/mux.go b/vendor/golang.org/x/crypto/ssh/mux.go
index 27a527c106..f19016270e 100644
--- a/vendor/golang.org/x/crypto/ssh/mux.go
+++ b/vendor/golang.org/x/crypto/ssh/mux.go
@@ -278,7 +278,7 @@ func (m *mux) handleChannelOpen(packet []byte) error {
 
 	if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 {
 		failMsg := channelOpenFailureMsg{
-			PeersId:  msg.PeersId,
+			PeersID:  msg.PeersID,
 			Reason:   ConnectionFailed,
 			Message:  "invalid request",
 			Language: "en_US.UTF-8",
@@ -287,7 +287,7 @@ func (m *mux) handleChannelOpen(packet []byte) error {
 	}
 
 	c := m.newChannel(msg.ChanType, channelInbound, msg.TypeSpecificData)
-	c.remoteId = msg.PeersId
+	c.remoteId = msg.PeersID
 	c.maxRemotePayload = msg.MaxPacketSize
 	c.remoteWin.add(msg.PeersWindow)
 	m.incomingChannels <- c
@@ -313,7 +313,7 @@ func (m *mux) openChannel(chanType string, extra []byte) (*channel, error) {
 		PeersWindow:      ch.myWindow,
 		MaxPacketSize:    ch.maxIncomingPayload,
 		TypeSpecificData: extra,
-		PeersId:          ch.localId,
+		PeersID:          ch.localId,
 	}
 	if err := m.sendMessage(open); err != nil {
 		return nil, err
diff --git a/vendor/golang.org/x/crypto/ssh/server.go b/vendor/golang.org/x/crypto/ssh/server.go
index 148d2cb245..d0f4825319 100644
--- a/vendor/golang.org/x/crypto/ssh/server.go
+++ b/vendor/golang.org/x/crypto/ssh/server.go
@@ -166,6 +166,9 @@ type ServerConn struct {
 // unsuccessful, it closes the connection and returns an error.  The
 // Request and NewChannel channels must be serviced, or the connection
 // will hang.
+//
+// The returned error may be of type *ServerAuthError for
+// authentication errors.
 func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewChannel, <-chan *Request, error) {
 	fullConf := *config
 	fullConf.SetDefaults()
@@ -256,7 +259,7 @@ func (s *connection) serverHandshake(config *ServerConfig) (*Permissions, error)
 func isAcceptableAlgo(algo string) bool {
 	switch algo {
 	case KeyAlgoRSA, KeyAlgoDSA, KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521, KeyAlgoED25519,
-		CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01:
+		CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoED25519v01:
 		return true
 	}
 	return false
@@ -292,12 +295,13 @@ func checkSourceAddress(addr net.Addr, sourceAddrs string) error {
 	return fmt.Errorf("ssh: remote address %v is not allowed because of source-address restriction", addr)
 }
 
-// ServerAuthError implements the error interface. It appends any authentication
-// errors that may occur, and is returned if all of the authentication methods
-// provided by the user failed to authenticate.
+// ServerAuthError represents server authentication errors and is
+// sometimes returned by NewServerConn. It appends any authentication
+// errors that may occur, and is returned if all of the authentication
+// methods provided by the user failed to authenticate.
 type ServerAuthError struct {
 	// Errors contains authentication errors returned by the authentication
-	// callback methods.
+	// callback methods. The first entry is typically ErrNoAuth.
 	Errors []error
 }
 
@@ -309,6 +313,13 @@ func (l ServerAuthError) Error() string {
 	return "[" + strings.Join(errs, ", ") + "]"
 }
 
+// ErrNoAuth is the error value returned if no
+// authentication method has been passed yet. This happens as a normal
+// part of the authentication loop, since the client first tries
+// 'none' authentication to discover available methods.
+// It is returned in ServerAuthError.Errors from NewServerConn.
+var ErrNoAuth = errors.New("ssh: no auth passed yet")
+
 func (s *connection) serverAuthenticate(config *ServerConfig) (*Permissions, error) {
 	sessionID := s.transport.getSessionID()
 	var cache pubKeyCache
@@ -316,6 +327,7 @@ func (s *connection) serverAuthenticate(config *ServerConfig) (*Permissions, err
 
 	authFailures := 0
 	var authErrs []error
+	var displayedBanner bool
 
 userAuthLoop:
 	for {
@@ -348,7 +360,8 @@ userAuthLoop:
 
 		s.user = userAuthReq.User
 
-		if authFailures == 0 && config.BannerCallback != nil {
+		if !displayedBanner && config.BannerCallback != nil {
+			displayedBanner = true
 			msg := config.BannerCallback(s)
 			if msg != "" {
 				bannerMsg := &userAuthBannerMsg{
@@ -361,7 +374,7 @@ userAuthLoop:
 		}
 
 		perms = nil
-		authErr := errors.New("no auth passed yet")
+		authErr := ErrNoAuth
 
 		switch userAuthReq.Method {
 		case "none":
diff --git a/vendor/golang.org/x/crypto/ssh/session.go b/vendor/golang.org/x/crypto/ssh/session.go
index cc06e03f5c..d3321f6b78 100644
--- a/vendor/golang.org/x/crypto/ssh/session.go
+++ b/vendor/golang.org/x/crypto/ssh/session.go
@@ -406,7 +406,7 @@ func (s *Session) Wait() error {
 		s.stdinPipeWriter.Close()
 	}
 	var copyError error
-	for _ = range s.copyFuncs {
+	for range s.copyFuncs {
 		if err := <-s.errors; err != nil && copyError == nil {
 			copyError = err
 		}
diff --git a/vendor/golang.org/x/crypto/ssh/transport.go b/vendor/golang.org/x/crypto/ssh/transport.go
index ab2b88765a..f6fae1db46 100644
--- a/vendor/golang.org/x/crypto/ssh/transport.go
+++ b/vendor/golang.org/x/crypto/ssh/transport.go
@@ -6,6 +6,7 @@ package ssh
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"io"
 	"log"
@@ -76,17 +77,17 @@ type connectionState struct {
 // both directions are triggered by reading and writing a msgNewKey packet
 // respectively.
 func (t *transport) prepareKeyChange(algs *algorithms, kexResult *kexResult) error {
-	if ciph, err := newPacketCipher(t.reader.dir, algs.r, kexResult); err != nil {
+	ciph, err := newPacketCipher(t.reader.dir, algs.r, kexResult)
+	if err != nil {
 		return err
-	} else {
-		t.reader.pendingKeyChange <- ciph
 	}
+	t.reader.pendingKeyChange <- ciph
 
-	if ciph, err := newPacketCipher(t.writer.dir, algs.w, kexResult); err != nil {
+	ciph, err = newPacketCipher(t.writer.dir, algs.w, kexResult)
+	if err != nil {
 		return err
-	} else {
-		t.writer.pendingKeyChange <- ciph
 	}
+	t.writer.pendingKeyChange <- ciph
 
 	return nil
 }
@@ -139,7 +140,7 @@ func (s *connectionState) readPacket(r *bufio.Reader) ([]byte, error) {
 			case cipher := <-s.pendingKeyChange:
 				s.packetCipher = cipher
 			default:
-				return nil, errors.New("ssh: got bogus newkeys message.")
+				return nil, errors.New("ssh: got bogus newkeys message")
 			}
 
 		case msgDisconnect:
@@ -232,52 +233,22 @@ var (
 	clientKeys = direction{[]byte{'A'}, []byte{'C'}, []byte{'E'}}
 )
 
-// generateKeys generates key material for IV, MAC and encryption.
-func generateKeys(d direction, algs directionAlgorithms, kex *kexResult) (iv, key, macKey []byte) {
+// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as
+// described in RFC 4253, section 6.4. direction should either be serverKeys
+// (to setup server->client keys) or clientKeys (for client->server keys).
+func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) {
 	cipherMode := cipherModes[algs.Cipher]
 	macMode := macModes[algs.MAC]
 
-	iv = make([]byte, cipherMode.ivSize)
-	key = make([]byte, cipherMode.keySize)
-	macKey = make([]byte, macMode.keySize)
+	iv := make([]byte, cipherMode.ivSize)
+	key := make([]byte, cipherMode.keySize)
+	macKey := make([]byte, macMode.keySize)
 
 	generateKeyMaterial(iv, d.ivTag, kex)
 	generateKeyMaterial(key, d.keyTag, kex)
 	generateKeyMaterial(macKey, d.macKeyTag, kex)
-	return
-}
-
-// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as
-// described in RFC 4253, section 6.4. direction should either be serverKeys
-// (to setup server->client keys) or clientKeys (for client->server keys).
-func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) {
-	iv, key, macKey := generateKeys(d, algs, kex)
-
-	if algs.Cipher == gcmCipherID {
-		return newGCMCipher(iv, key)
-	}
-
-	if algs.Cipher == aes128cbcID {
-		return newAESCBCCipher(iv, key, macKey, algs)
-	}
-
-	if algs.Cipher == tripledescbcID {
-		return newTripleDESCBCCipher(iv, key, macKey, algs)
-	}
 
-	c := &streamPacketCipher{
-		mac: macModes[algs.MAC].new(macKey),
-		etm: macModes[algs.MAC].etm,
-	}
-	c.macResult = make([]byte, c.mac.Size())
-
-	var err error
-	c.cipher, err = cipherModes[algs.Cipher].createStream(key, iv)
-	if err != nil {
-		return nil, err
-	}
-
-	return c, nil
+	return cipherModes[algs.Cipher].create(key, iv, macKey, algs)
 }
 
 // generateKeyMaterial fills out with key material generated from tag, K, H
@@ -342,7 +313,7 @@ func readVersion(r io.Reader) ([]byte, error) {
 	var ok bool
 	var buf [1]byte
 
-	for len(versionString) < maxVersionStringBytes {
+	for length := 0; length < maxVersionStringBytes; length++ {
 		_, err := io.ReadFull(r, buf[:])
 		if err != nil {
 			return nil, err
@@ -350,6 +321,13 @@ func readVersion(r io.Reader) ([]byte, error) {
 		// The RFC says that the version should be terminated with \r\n
 		// but several SSH servers actually only send a \n.
 		if buf[0] == '\n' {
+			if !bytes.HasPrefix(versionString, []byte("SSH-")) {
+				// RFC 4253 says we need to ignore all version string lines
+				// except the one containing the SSH version (provided that
+				// all the lines do not exceed 255 bytes in total).
+				versionString = versionString[:0]
+				continue
+			}
 			ok = true
 			break
 		}