Merge pull request #1773 from faro-oss/faro-upstream/add-c_hash-to-id_token

Add c_hash to id_token, issued on /auth endpoint, when in hybrid flow

server/handlers.go

@@ -681,7 +681,7 @@ func (s *Server) sendCodeResponse(w http.ResponseWriter, r *http.Request, authRe
 				return
 			}
 
-			idToken, idTokenExpiry, err = s.newIDToken(authReq.ClientID, authReq.Claims, authReq.Scopes, authReq.Nonce, accessToken, authReq.ConnectorID)
+			idToken, idTokenExpiry, err = s.newIDToken(authReq.ClientID, authReq.Claims, authReq.Scopes, authReq.Nonce, accessToken, code.ID, authReq.ConnectorID)
 			if err != nil {
 				s.logger.Errorf("failed to create ID token: %v", err)
 				s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
@@ -868,7 +868,7 @@ func (s *Server) exchangeAuthCode(w http.ResponseWriter, authCode storage.AuthCo
 		return nil, err
 	}
 
-	idToken, expiry, err := s.newIDToken(client.ID, authCode.Claims, authCode.Scopes, authCode.Nonce, accessToken, authCode.ConnectorID)
+	idToken, expiry, err := s.newIDToken(client.ID, authCode.Claims, authCode.Scopes, authCode.Nonce, accessToken, authCode.ID, authCode.ConnectorID)
 	if err != nil {
 		s.logger.Errorf("failed to create ID token: %v", err)
 		s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
@@ -1140,7 +1140,7 @@ func (s *Server) handleRefreshToken(w http.ResponseWriter, r *http.Request, clie
 		return
 	}
 
-	idToken, expiry, err := s.newIDToken(client.ID, claims, scopes, refresh.Nonce, accessToken, refresh.ConnectorID)
+	idToken, expiry, err := s.newIDToken(client.ID, claims, scopes, refresh.Nonce, accessToken, "", refresh.ConnectorID)
 	if err != nil {
 		s.logger.Errorf("failed to create ID token: %v", err)
 		s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
@@ -1325,7 +1325,7 @@ func (s *Server) handlePasswordGrant(w http.ResponseWriter, r *http.Request, cli
 	}
 
 	accessToken := storage.NewID()
-	idToken, expiry, err := s.newIDToken(client.ID, claims, scopes, nonce, accessToken, connID)
+	idToken, expiry, err := s.newIDToken(client.ID, claims, scopes, nonce, accessToken, "", connID)
 	if err != nil {
 		s.tokenErrHelper(w, errServerError, fmt.Sprintf("failed to create ID token: %v", err), http.StatusInternalServerError)
 		return

server/oauth2.go

@@ -230,11 +230,11 @@ func accessTokenHash(alg jose.SignatureAlgorithm, accessToken string) (string, e
 		return "", fmt.Errorf("unsupported signature algorithm: %s", alg)
 	}
 
-	hash := newHash()
-	if _, err := io.WriteString(hash, accessToken); err != nil {
+	hashFunc := newHash()
+	if _, err := io.WriteString(hashFunc, accessToken); err != nil {
 		return "", fmt.Errorf("computing hash: %v", err)
 	}
-	sum := hash.Sum(nil)
+	sum := hashFunc.Sum(nil)
 	return base64.RawURLEncoding.EncodeToString(sum[:len(sum)/2]), nil
 }
 
@@ -266,6 +266,7 @@ type idTokenClaims struct {
 	Nonce            string   `json:"nonce,omitempty"`
 
 	AccessTokenHash string `json:"at_hash,omitempty"`
+	CodeHash        string `json:"c_hash,omitempty"`
 
 	Email         string `json:"email,omitempty"`
 	EmailVerified *bool  `json:"email_verified,omitempty"`
@@ -284,11 +285,11 @@ type federatedIDClaims struct {
 }
 
 func (s *Server) newAccessToken(clientID string, claims storage.Claims, scopes []string, nonce, connID string) (accessToken string, err error) {
-	idToken, _, err := s.newIDToken(clientID, claims, scopes, nonce, storage.NewID(), connID)
+	idToken, _, err := s.newIDToken(clientID, claims, scopes, nonce, storage.NewID(), "", connID)
 	return idToken, err
 }
 
-func (s *Server) newIDToken(clientID string, claims storage.Claims, scopes []string, nonce, accessToken, connID string) (idToken string, expiry time.Time, err error) {
+func (s *Server) newIDToken(clientID string, claims storage.Claims, scopes []string, nonce, accessToken, code, connID string) (idToken string, expiry time.Time, err error) {
 	keys, err := s.storage.GetKeys()
 	if err != nil {
 		s.logger.Errorf("Failed to get keys: %v", err)
@@ -335,6 +336,15 @@ func (s *Server) newIDToken(clientID string, claims storage.Claims, scopes []str
 		tok.AccessTokenHash = atHash
 	}
 
+	if code != "" {
+		cHash, err := accessTokenHash(signingAlg, code)
+		if err != nil {
+			s.logger.Errorf("error computing c_hash: %v", err)
+			return "", expiry, fmt.Errorf("error computing c_hash: #{err}")
+		}
+		tok.CodeHash = cHash
+	}
+
 	for _, scope := range scopes {
 		switch {
 		case scope == scopeEmail: