Race condition fix proposal

src/Grant/AuthCodeGrant.php

@@ -141,23 +141,33 @@ public function respondToAccessTokenRequest(
             $this->validateCodeChallenge($authCodePayload, $codeVerifier);
         }
 
-        // Issue and persist new access token
-        $accessToken = $this->issueAccessToken($accessTokenTTL, $client, $authCodePayload->user_id, $scopes);
-        $this->getEmitter()->emit(new RequestAccessTokenEvent(RequestEvent::ACCESS_TOKEN_ISSUED, $request, $accessToken));
-        $responseType->setAccessToken($accessToken);
-
-        // Issue and persist new refresh token if given
-        $refreshToken = $this->issueRefreshToken($accessToken);
+        if ($this->authCodeRepository->lockAuthCode($authCodePayload->auth_code_id)) {
+            try {
+                // Issue and persist new access token
+                $accessToken = $this->issueAccessToken($accessTokenTTL, $client, $authCodePayload->user_id, $scopes);
+                $this->getEmitter()->emit(new RequestAccessTokenEvent(RequestEvent::ACCESS_TOKEN_ISSUED, $request, $accessToken));
+                $responseType->setAccessToken($accessToken);
+
+                // Issue and persist new refresh token if given
+                $refreshToken = $this->issueRefreshToken($accessToken);
+
+                if ($refreshToken !== null) {
+                    $this->getEmitter()->emit(new RequestRefreshTokenEvent(RequestEvent::REFRESH_TOKEN_ISSUED, $request, $refreshToken));
+                    $responseType->setRefreshToken($refreshToken);
+                }
 
-        if ($refreshToken !== null) {
-            $this->getEmitter()->emit(new RequestRefreshTokenEvent(RequestEvent::REFRESH_TOKEN_ISSUED, $request, $refreshToken));
-            $responseType->setRefreshToken($refreshToken);
+                return $responseType;
+            } catch (Exception $e) {
+                $this->authCodeRepository->unlockAuthCode($authCodePayload->auth_code_id);
+                throw OAuthServerException::serverError(
+                    'access_token',
+                    $e
+                );
+            } finally {
+                // Revoke used auth code
+                $this->authCodeRepository->revokeAuthCode($authCodePayload->auth_code_id);
+            }
         }
-
-        // Revoke used auth code
-        $this->authCodeRepository->revokeAuthCode($authCodePayload->auth_code_id);
-
-        return $responseType;
     }
 
     private function validateCodeChallenge(object $authCodePayload, ?string $codeVerifier): void
@@ -213,6 +223,10 @@ private function validateAuthorizationCode(
             throw OAuthServerException::invalidGrant('Authorization code has been revoked');
         }
 
+        if ($this->authCodeRepository->isAuthCodeLocked($authCodePayload->auth_code_id) === true) {
+            throw OAuthServerException::invalidGrant('Authorization code has been locked while an access code beeing issued');
+        }
+
         if ($authCodePayload->client_id !== $client->getIdentifier()) {
             throw OAuthServerException::invalidRequest('code', 'Authorization code was not issued to this client');
         }

src/Repositories/AuthCodeRepositoryInterface.php

@@ -30,4 +30,22 @@ public function persistNewAuthCode(AuthCodeEntityInterface $authCodeEntity): voi
     public function revokeAuthCode(string $codeId): void;
 
     public function isAuthCodeRevoked(string $codeId): bool;
+
+    /**
+     * Method locks an auth code in case an error occurs during the issuance of an access code.
+     *
+     * The storage engine should make this persistent immediately to prevent possible race conditions while issuing an access token.
+     *
+     * @param string $codeId
+     */
+    public function lockAuthCode(string $codeId): bool;
+
+    /**
+     * This method is used to make the auth code available again after an error occurred in the access code issuance process.
+     *
+     * @param string $codeId
+     */
+    public function unlockAuthCode(string $codeId): void;
+
+    public function isAuthCodeLocked(string $codeId): bool;
 }

tests/Grant/AuthCodeGrantTest.php

@@ -1387,6 +1387,73 @@ public function testRespondToAccessTokenRequestRevokedCode(): void
         }
     }
 
+    public function testRespondToAccessTokenRequestLockedCode(): void
+    {
+        $client = new ClientEntity();
+
+        $client->setIdentifier('foo');
+        $client->setRedirectUri(self::REDIRECT_URI);
+        $client->setConfidential();
+
+        $clientRepositoryMock = $this->getMockBuilder(ClientRepositoryInterface::class)->getMock();
+
+        $clientRepositoryMock->method('getClientEntity')->willReturn($client);
+        $clientRepositoryMock->method('validateClient')->willReturn(true);
+
+        $accessTokenRepositoryMock = $this->getMockBuilder(AccessTokenRepositoryInterface::class)->getMock();
+        $accessTokenRepositoryMock->method('persistNewAccessToken')->willReturnSelf();
+
+        $refreshTokenRepositoryMock = $this->getMockBuilder(RefreshTokenRepositoryInterface::class)->getMock();
+        $refreshTokenRepositoryMock->method('persistNewRefreshToken')->willReturnSelf();
+
+        $authCodeRepositoryMock = $this->getMockBuilder(AuthCodeRepositoryInterface::class)->getMock();
+        $authCodeRepositoryMock->method('isAuthCodeLocked')->willReturn(true);
+
+        $grant = new AuthCodeGrant(
+            $authCodeRepositoryMock,
+            $this->getMockBuilder(RefreshTokenRepositoryInterface::class)->getMock(),
+            new DateInterval('PT10M')
+        );
+        $grant->setClientRepository($clientRepositoryMock);
+        $grant->setAccessTokenRepository($accessTokenRepositoryMock);
+        $grant->setRefreshTokenRepository($refreshTokenRepositoryMock);
+        $grant->setEncryptionKey($this->cryptStub->getKey());
+
+        $request = new ServerRequest(
+            [],
+            [],
+            null,
+            'POST',
+            'php://input',
+            [],
+            [],
+            [],
+            [
+                'grant_type'   => 'authorization_code',
+                'client_id'    => 'foo',
+                'redirect_uri' => self::REDIRECT_URI,
+                'code'         => $this->cryptStub->doEncrypt(
+                    json_encode([
+                        'auth_code_id' => uniqid(),
+                        'expire_time'  => time() + 3600,
+                        'client_id'    => 'foo',
+                        'user_id'      => 123,
+                        'scopes'       => ['foo'],
+                        'redirect_uri' => 'http://foo/bar',
+                    ], JSON_THROW_ON_ERROR)
+                ),
+            ]
+        );
+
+        try {
+            /* @var StubResponseType $response */
+            $grant->respondToAccessTokenRequest($request, new StubResponseType(), new DateInterval('PT10M'));
+        } catch (OAuthServerException $e) {
+            self::assertEquals($e->getHint(), 'Authorization code has been revoked');
+            self::assertEquals($e->getErrorType(), 'invalid_grant');
+        }
+    }
+
     public function testRespondToAccessTokenRequestClientMismatch(): void
     {
         $client = new ClientEntity();