1 files changed, 155 insertions, 0 deletions
diff --git a/vendor/github.com/duo-labs/webauthn/protocol/assertion.go b/vendor/github.com/duo-labs/webauthn/protocol/assertion.go
new file mode 100644
index 0000000000..1dd8e3952b
--- /dev/null
+++ b/vendor/github.com/duo-labs/webauthn/protocol/assertion.go
@@ -0,0 +1,155 @@
+package protocol
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/duo-labs/webauthn/protocol/webauthncose"
+)
+
+// The raw response returned to us from an authenticator when we request a
+// credential for login/assertion.
+type CredentialAssertionResponse struct {
+	PublicKeyCredential
+	AssertionResponse AuthenticatorAssertionResponse `json:"response"`
+}
+
+// The parsed CredentialAssertionResponse that has been marshalled into a format
+// that allows us to verify the client and authenticator data inside the response
+type ParsedCredentialAssertionData struct {
+	ParsedPublicKeyCredential
+	Response ParsedAssertionResponse
+	Raw      CredentialAssertionResponse
+}
+
+// The AuthenticatorAssertionResponse contains the raw authenticator assertion data and is parsed into
+// ParsedAssertionResponse
+type AuthenticatorAssertionResponse struct {
+	AuthenticatorResponse
+	AuthenticatorData URLEncodedBase64 `json:"authenticatorData"`
+	Signature         URLEncodedBase64 `json:"signature"`
+	UserHandle        URLEncodedBase64 `json:"userHandle,omitempty"`
+}
+
+// Parsed form of AuthenticatorAssertionResponse
+type ParsedAssertionResponse struct {
+	CollectedClientData CollectedClientData
+	AuthenticatorData   AuthenticatorData
+	Signature           []byte
+	UserHandle          []byte
+}
+
+// Parse the credential request response into a format that is either required by the specification
+// or makes the assertion verification steps easier to complete. This takes an http.Request that contains
+// the assertion response data in a raw, mostly base64 encoded format, and parses the data into
+// manageable structures
+func ParseCredentialRequestResponse(response *http.Request) (*ParsedCredentialAssertionData, error) {
+	if response == nil || response.Body == nil {
+		return nil, ErrBadRequest.WithDetails("No response given")
+	}
+	return ParseCredentialRequestResponseBody(response.Body)
+}
+
+// Parse the credential request response into a format that is either required by the specification
+// or makes the assertion verification steps easier to complete. This takes an io.Reader that contains
+// the assertion response data in a raw, mostly base64 encoded format, and parses the data into
+// manageable structures
+func ParseCredentialRequestResponseBody(body io.Reader) (*ParsedCredentialAssertionData, error) {
+	var car CredentialAssertionResponse
+	err := json.NewDecoder(body).Decode(&car)
+	if err != nil {
+		return nil, ErrBadRequest.WithDetails("Parse error for Assertion")
+	}
+
+	if car.ID == "" {
+		return nil, ErrBadRequest.WithDetails("CredentialAssertionResponse with ID missing")
+	}
+
+	_, err = base64.RawURLEncoding.DecodeString(car.ID)
+	if err != nil {
+		return nil, ErrBadRequest.WithDetails("CredentialAssertionResponse with ID not base64url encoded")
+	}
+	if car.Type != "public-key" {
+		return nil, ErrBadRequest.WithDetails("CredentialAssertionResponse with bad type")
+	}
+	var par ParsedCredentialAssertionData
+	par.ID, par.RawID, par.Type, par.ClientExtensionResults = car.ID, car.RawID, car.Type, car.ClientExtensionResults
+	par.Raw = car
+
+	par.Response.Signature = car.AssertionResponse.Signature
+	par.Response.UserHandle = car.AssertionResponse.UserHandle
+
+	// Step 5. Let JSONtext be the result of running UTF-8 decode on the value of cData.
+	// We don't call it cData but this is Step 5 in the spec.
+	err = json.Unmarshal(car.AssertionResponse.ClientDataJSON, &par.Response.CollectedClientData)
+	if err != nil {
+		return nil, err
+	}
+
+	err = par.Response.AuthenticatorData.Unmarshal(car.AssertionResponse.AuthenticatorData)
+	if err != nil {
+		return nil, ErrParsingData.WithDetails("Error unmarshalling auth data")
+	}
+	return &par, nil
+}
+
+// Follow the remaining steps outlined in §7.2 Verifying an authentication assertion
+// (https://www.w3.org/TR/webauthn/#verifying-assertion) and return an error if there
+// is a failure during each step.
+func (p *ParsedCredentialAssertionData) Verify(storedChallenge string, relyingPartyID, relyingPartyOrigin, appID string, verifyUser bool, credentialBytes []byte) error {
+	// Steps 4 through 6 in verifying the assertion data (https://www.w3.org/TR/webauthn/#verifying-assertion) are
+	// "assertive" steps, i.e "Let JSONtext be the result of running UTF-8 decode on the value of cData."
+	// We handle these steps in part as we verify but also beforehand
+
+	// Handle steps 7 through 10 of assertion by verifying stored data against the Collected Client Data
+	// returned by the authenticator
+	validError := p.Response.CollectedClientData.Verify(storedChallenge, AssertCeremony, relyingPartyOrigin)
+	if validError != nil {
+		return validError
+	}
+
+	// Begin Step 11. Verify that the rpIdHash in authData is the SHA-256 hash of the RP ID expected by the RP.
+	rpIDHash := sha256.Sum256([]byte(relyingPartyID))
+
+	var appIDHash [32]byte
+	if appID != "" {
+		appIDHash = sha256.Sum256([]byte(appID))
+	}
+
+	// Handle steps 11 through 14, verifying the authenticator data.
+	validError = p.Response.AuthenticatorData.Verify(rpIDHash[:], appIDHash[:], verifyUser)
+	if validError != nil {
+		return ErrAuthData.WithInfo(validError.Error())
+	}
+
+	// allowedUserCredentialIDs := session.AllowedCredentialIDs
+
+	// Step 15. Let hash be the result of computing a hash over the cData using SHA-256.
+	clientDataHash := sha256.Sum256(p.Raw.AssertionResponse.ClientDataJSON)
+
+	// Step 16. Using the credential public key looked up in step 3, verify that sig is
+	// a valid signature over the binary concatenation of authData and hash.
+
+	sigData := append(p.Raw.AssertionResponse.AuthenticatorData, clientDataHash[:]...)
+
+	var (
+		key interface{}
+		err error
+	)
+
+	if appID == "" {
+		key, err = webauthncose.ParsePublicKey(credentialBytes)
+	} else {
+		key, err = webauthncose.ParseFIDOPublicKey(credentialBytes)
+	}
+
+	valid, err := webauthncose.VerifySignature(key, sigData, p.Response.Signature)
+	if !valid {
+		return ErrAssertionSignature.WithDetails(fmt.Sprintf("Error validating the assertion signature: %+v\n", err))
+	}
+	return nil
+}