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- // Copyright 2015 Matthew Holt
- //
- // Licensed under the Apache License, Version 2.0 (the "License");
- // you may not use this file except in compliance with the License.
- // You may obtain a copy of the License at
- //
- // http://www.apache.org/licenses/LICENSE-2.0
- //
- // Unless required by applicable law or agreed to in writing, software
- // distributed under the License is distributed on an "AS IS" BASIS,
- // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- // See the License for the specific language governing permissions and
- // limitations under the License.
-
- package certmagic
-
- import (
- "net/http"
- "strings"
-
- "github.com/mholt/acmez/acme"
- "go.uber.org/zap"
- )
-
- // HTTPChallengeHandler wraps h in a handler that can solve the ACME
- // HTTP challenge. cfg is required, and it must have a certificate
- // cache backed by a functional storage facility, since that is where
- // the challenge state is stored between initiation and solution.
- //
- // If a request is not an ACME HTTP challenge, h will be invoked.
- func (am *ACMEManager) HTTPChallengeHandler(h http.Handler) http.Handler {
- return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
- if am.HandleHTTPChallenge(w, r) {
- return
- }
- h.ServeHTTP(w, r)
- })
- }
-
- // HandleHTTPChallenge uses am to solve challenge requests from an ACME
- // server that were initiated by this instance or any other instance in
- // this cluster (being, any instances using the same storage am does).
- //
- // If the HTTP challenge is disabled, this function is a no-op.
- //
- // If am is nil or if am does not have a certificate cache backed by
- // usable storage, solving the HTTP challenge will fail.
- //
- // It returns true if it handled the request; if so, the response has
- // already been written. If false is returned, this call was a no-op and
- // the request has not been handled.
- func (am *ACMEManager) HandleHTTPChallenge(w http.ResponseWriter, r *http.Request) bool {
- if am == nil {
- return false
- }
- if am.DisableHTTPChallenge {
- return false
- }
- if !LooksLikeHTTPChallenge(r) {
- return false
- }
- return am.distributedHTTPChallengeSolver(w, r)
- }
-
- // distributedHTTPChallengeSolver checks to see if this challenge
- // request was initiated by this or another instance which uses the
- // same storage as am does, and attempts to complete the challenge for
- // it. It returns true if the request was handled; false otherwise.
- func (am *ACMEManager) distributedHTTPChallengeSolver(w http.ResponseWriter, r *http.Request) bool {
- if am == nil {
- return false
- }
- host := hostOnly(r.Host)
- chalInfo, distributed, err := am.config.getChallengeInfo(host)
- if err != nil {
- if am.Logger != nil {
- am.Logger.Error("looking up info for HTTP challenge",
- zap.String("host", host),
- zap.Error(err))
- }
- return false
- }
- return solveHTTPChallenge(am.Logger, w, r, chalInfo.Challenge, distributed)
- }
-
- // solveHTTPChallenge solves the HTTP challenge using the given challenge information.
- // If the challenge is being solved in a distributed fahsion, set distributed to true for logging purposes.
- // It returns true the properties of the request check out in relation to the HTTP challenge.
- // Most of this code borrowed from xenolf's built-in HTTP-01 challenge solver in March 2018.
- func solveHTTPChallenge(logger *zap.Logger, w http.ResponseWriter, r *http.Request, challenge acme.Challenge, distributed bool) bool {
- challengeReqPath := challenge.HTTP01ResourcePath()
- if r.URL.Path == challengeReqPath &&
- strings.EqualFold(hostOnly(r.Host), challenge.Identifier.Value) && // mitigate DNS rebinding attacks
- r.Method == "GET" {
- w.Header().Add("Content-Type", "text/plain")
- w.Write([]byte(challenge.KeyAuthorization))
- r.Close = true
- if logger != nil {
- logger.Info("served key authentication",
- zap.String("identifier", challenge.Identifier.Value),
- zap.String("challenge", "http-01"),
- zap.String("remote", r.RemoteAddr),
- zap.Bool("distributed", distributed))
- }
- return true
- }
- return false
- }
-
- // SolveHTTPChallenge solves the HTTP challenge. It should be used only on HTTP requests that are
- // from ACME servers trying to validate an identifier (i.e. LooksLikeHTTPChallenge() == true). It
- // returns true if the request criteria check out and it answered with key authentication, in which
- // case no further handling of the request is necessary.
- func SolveHTTPChallenge(logger *zap.Logger, w http.ResponseWriter, r *http.Request, challenge acme.Challenge) bool {
- return solveHTTPChallenge(logger, w, r, challenge, false)
- }
-
- // LooksLikeHTTPChallenge returns true if r looks like an ACME
- // HTTP challenge request from an ACME server.
- func LooksLikeHTTPChallenge(r *http.Request) bool {
- return r.Method == "GET" && strings.HasPrefix(r.URL.Path, challengeBasePath)
- }
-
- const challengeBasePath = "/.well-known/acme-challenge"
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