OAuth2LoginAuthenticationFilter should handle null ClientRegistration

Fixes gh-5251

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/web/OAuth2LoginAuthenticationFilter.java

@@ -96,6 +96,7 @@ public class OAuth2LoginAuthenticationFilter extends AbstractAuthenticationProce
 	 */
 	public static final String DEFAULT_FILTER_PROCESSES_URI = "/login/oauth2/code/*";
 	private static final String AUTHORIZATION_REQUEST_NOT_FOUND_ERROR_CODE = "authorization_request_not_found";
+	private static final String CLIENT_REGISTRATION_NOT_FOUND_ERROR_CODE = "client_registration_not_found";
 	private ClientRegistrationRepository clientRegistrationRepository;
 	private OAuth2AuthorizedClientService authorizedClientService;
 	private AuthorizationRequestRepository<OAuth2AuthorizationRequest> authorizationRequestRepository =
@@ -146,7 +147,11 @@ public class OAuth2LoginAuthenticationFilter extends AbstractAuthenticationProce
 
 		String registrationId = (String) authorizationRequest.getAdditionalParameters().get(OAuth2ParameterNames.REGISTRATION_ID);
 		ClientRegistration clientRegistration = this.clientRegistrationRepository.findByRegistrationId(registrationId);
-
+		if (clientRegistration == null) {
+			OAuth2Error oauth2Error = new OAuth2Error(CLIENT_REGISTRATION_NOT_FOUND_ERROR_CODE,
+					"Client Registration not found with Id: " + registrationId, null);
+			throw new OAuth2AuthenticationException(oauth2Error, oauth2Error.toString());
+		}
 		OAuth2AuthorizationResponse authorizationResponse = OAuth2AuthorizationResponseUtils.convert(request);
 
 		OAuth2LoginAuthenticationToken authenticationRequest = new OAuth2LoginAuthenticationToken(

oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/web/OAuth2LoginAuthenticationFilterTests.java

@@ -199,6 +199,45 @@ public class OAuth2LoginAuthenticationFilterTests {
 		assertThat(authenticationException.getError().getErrorCode()).isEqualTo("authorization_request_not_found");
 	}
 
+	// gh-5251
+	@Test
+	public void doFilterWhenAuthorizationResponseClientRegistrationNotFoundThenClientRegistrationNotFoundError() throws Exception {
+		String requestUri = "/login/oauth2/code/" + this.registration2.getRegistrationId();
+		String state = "state";
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", requestUri);
+		request.setServletPath(requestUri);
+		request.addParameter(OAuth2ParameterNames.CODE, "code");
+		request.addParameter(OAuth2ParameterNames.STATE, "state");
+
+		MockHttpServletResponse response = new MockHttpServletResponse();
+		FilterChain filterChain = mock(FilterChain.class);
+
+		ClientRegistration registrationNotFound = ClientRegistration.withRegistrationId("registration-not-found")
+				.clientId("client-1")
+				.clientSecret("secret")
+				.clientAuthenticationMethod(ClientAuthenticationMethod.BASIC)
+				.authorizationGrantType(AuthorizationGrantType.AUTHORIZATION_CODE)
+				.redirectUriTemplate("{baseUrl}/login/oauth2/code/{registrationId}")
+				.scope("user")
+				.authorizationUri("https://provider.com/oauth2/authorize")
+				.tokenUri("https://provider.com/oauth2/token")
+				.userInfoUri("https://provider.com/oauth2/user")
+				.userNameAttributeName("id")
+				.clientName("client-1")
+				.build();
+		this.setUpAuthorizationRequest(request, response, registrationNotFound, state);
+
+		this.filter.doFilter(request, response, filterChain);
+
+		ArgumentCaptor<AuthenticationException> authenticationExceptionArgCaptor = ArgumentCaptor.forClass(AuthenticationException.class);
+		verify(this.failureHandler).onAuthenticationFailure(any(HttpServletRequest.class), any(HttpServletResponse.class),
+				authenticationExceptionArgCaptor.capture());
+
+		assertThat(authenticationExceptionArgCaptor.getValue()).isInstanceOf(OAuth2AuthenticationException.class);
+		OAuth2AuthenticationException authenticationException = (OAuth2AuthenticationException) authenticationExceptionArgCaptor.getValue();
+		assertThat(authenticationException.getError().getErrorCode()).isEqualTo("client_registration_not_found");
+	}
+
 	@Test
 	public void doFilterWhenAuthorizationResponseValidThenAuthorizationRequestRemoved() throws Exception {
 		String requestUri = "/login/oauth2/code/" + this.registration2.getRegistrationId();