Allow form login when single OAuth2 Provider is configured

Closes gh-6802

config/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.security.config.annotation.web.configurers.oauth2.client;
 
+import java.lang.reflect.Field;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -73,12 +74,14 @@ import org.springframework.security.web.authentication.ui.DefaultLoginPageGenera
 import org.springframework.security.web.savedrequest.RequestCache;
 import org.springframework.security.web.util.matcher.AndRequestMatcher;
 import org.springframework.security.web.util.matcher.AntPathRequestMatcher;
+import org.springframework.security.web.util.matcher.AnyRequestMatcher;
 import org.springframework.security.web.util.matcher.NegatedRequestMatcher;
 import org.springframework.security.web.util.matcher.OrRequestMatcher;
 import org.springframework.security.web.util.matcher.RequestHeaderRequestMatcher;
 import org.springframework.security.web.util.matcher.RequestMatcher;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
 
 /**
  * An {@link AbstractHttpConfigurer} for OAuth 2.0 Login, which leverages the OAuth 2.0
@@ -503,14 +506,28 @@ public final class OAuth2LoginConfigurer<B extends HttpSecurityBuilder<B>>
 				new OrRequestMatcher(loginPageMatcher, faviconMatcher), defaultEntryPointMatcher);
 		RequestMatcher notXRequestedWith = new NegatedRequestMatcher(
 				new RequestHeaderRequestMatcher("X-Requested-With", "XMLHttpRequest"));
+		RequestMatcher formLoginNotEnabled = getFormLoginNotEnabledRequestMatcher(http);
 		LinkedHashMap<RequestMatcher, AuthenticationEntryPoint> entryPoints = new LinkedHashMap<>();
-		entryPoints.put(new AndRequestMatcher(notXRequestedWith, new NegatedRequestMatcher(defaultLoginPageMatcher)),
+		entryPoints.put(new AndRequestMatcher(notXRequestedWith, new NegatedRequestMatcher(defaultLoginPageMatcher),
-				new LoginUrlAuthenticationEntryPoint(providerLoginPage));
+				formLoginNotEnabled), new LoginUrlAuthenticationEntryPoint(providerLoginPage));
 		DelegatingAuthenticationEntryPoint loginEntryPoint = new DelegatingAuthenticationEntryPoint(entryPoints);
 		loginEntryPoint.setDefaultEntryPoint(this.getAuthenticationEntryPoint());
 		return loginEntryPoint;
 	}
 
+	private RequestMatcher getFormLoginNotEnabledRequestMatcher(B http) {
+		DefaultLoginPageGeneratingFilter defaultLoginPageGeneratingFilter = http
+				.getSharedObject(DefaultLoginPageGeneratingFilter.class);
+		Field formLoginEnabledField = (defaultLoginPageGeneratingFilter != null)
+				? ReflectionUtils.findField(DefaultLoginPageGeneratingFilter.class, "formLoginEnabled") : null;
+		if (formLoginEnabledField != null) {
+			ReflectionUtils.makeAccessible(formLoginEnabledField);
+			return (request) -> Boolean.FALSE
+					.equals(ReflectionUtils.getField(formLoginEnabledField, defaultLoginPageGeneratingFilter));
+		}
+		return AnyRequestMatcher.INSTANCE;
+	}
+
 	/**
 	 * Configuration options for the Authorization Server's Authorization Endpoint.
 	 */

config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -368,6 +368,17 @@ public class OAuth2LoginConfigurerTests {
 		assertThat(this.response.getRedirectedUrl()).matches("http://localhost/oauth2/authorization/google");
 	}
 
+	// gh-6802
+	@Test
+	public void oauth2LoginWithOneClientConfiguredAndFormLoginThenRedirectDefaultLoginPage() throws Exception {
+		loadConfig(OAuth2LoginConfigFormLogin.class);
+		String requestUri = "/";
+		this.request = new MockHttpServletRequest("GET", requestUri);
+		this.request.setServletPath(requestUri);
+		this.springSecurityFilterChain.doFilter(this.request, this.response, this.filterChain);
+		assertThat(this.response.getRedirectedUrl()).matches("http://localhost/login");
+	}
+
 	// gh-5347
 	@Test
 	public void oauth2LoginWithOneClientConfiguredAndRequestFaviconNotAuthenticatedThenRedirectDefaultLoginPage()
@@ -642,6 +653,26 @@ public class OAuth2LoginConfigurerTests {
 
 	}
 
+	@EnableWebSecurity
+	static class OAuth2LoginConfigFormLogin extends CommonWebSecurityConfigurerAdapter {
+
+		private final InMemoryClientRegistrationRepository clientRegistrationRepository = new InMemoryClientRegistrationRepository(
+				GOOGLE_CLIENT_REGISTRATION);
+
+		@Override
+		protected void configure(HttpSecurity http) throws Exception {
+			// @formatter:off
+			http
+				.oauth2Login()
+					.clientRegistrationRepository(this.clientRegistrationRepository)
+					.and()
+				.formLogin();
+			// @formatter:on
+			super.configure(http);
+		}
+
+	}
+
 	@EnableWebSecurity
 	static class OAuth2LoginInLambdaConfig extends CommonLambdaWebSecurityConfigurerAdapter
 			implements ApplicationListener<AuthenticationSuccessEvent> {