Limit oauth2Login() links to redirect-based flows

This prevents the generated login page from showing links for
authorization grant types like "client_credentials" which are
not redirect-based, and thus not meant for interactive use in
the browser.

Closes gh-9457

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -126,6 +126,11 @@ public class OAuth2LoginConfigurerTests {
 			.build();
 	// @formatter:on
 
+	// @formatter:off
+	private static final ClientRegistration CLIENT_CREDENTIALS_REGISTRATION = TestClientRegistrations.clientCredentials()
+			.build();
+	// @formatter:on
+
 	private ConfigurableApplicationContext context;
 
 	@Autowired
@@ -396,6 +401,18 @@ public class OAuth2LoginConfigurerTests {
 		assertThat(this.response.getRedirectedUrl()).doesNotMatch("http://localhost/oauth2/authorization/google");
 	}
 
+	// gh-9457
+	@Test
+	public void oauth2LoginWithOneAuthorizationCodeClientAndOtherClientsConfiguredThenRedirectForAuthorization()
+			throws Exception {
+		loadConfig(OAuth2LoginConfigAuthorizationCodeClientAndOtherClients.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/oauth2/authorization/google");
+	}
+
 	@Test
 	public void oauth2LoginWithCustomLoginPageThenRedirectCustomLoginPage() throws Exception {
 		loadConfig(OAuth2LoginConfigCustomLoginPage.class);
@@ -799,6 +816,23 @@ public class OAuth2LoginConfigurerTests {
 
 	}
 
+	@EnableWebSecurity
+	static class OAuth2LoginConfigAuthorizationCodeClientAndOtherClients extends CommonWebSecurityConfigurerAdapter {
+
+		@Override
+		protected void configure(HttpSecurity http) throws Exception {
+			// @formatter:off
+			http
+					.oauth2Login()
+					.clientRegistrationRepository(
+							new InMemoryClientRegistrationRepository(
+									GOOGLE_CLIENT_REGISTRATION, CLIENT_CREDENTIALS_REGISTRATION));
+			// @formatter:on
+			super.configure(http);
+		}
+
+	}
+
 	@EnableWebSecurity
 	static class OAuth2LoginConfigCustomLoginPage extends CommonWebSecurityConfigurerAdapter {
 

config/src/test/java/org/springframework/security/config/web/server/OAuth2LoginTests.java

@@ -134,6 +134,11 @@ public class OAuth2LoginTests {
 	private static ClientRegistration google = CommonOAuth2Provider.GOOGLE.getBuilder("google").clientId("client")
 			.clientSecret("secret").build();
 
+	// @formatter:off
+	private static ClientRegistration clientCredentials = TestClientRegistrations.clientCredentials()
+			.build();
+	// @formatter:on
+
 	@Autowired
 	public void setApplicationContext(ApplicationContext context) {
 		if (context.getBeanNamesForType(WebHandler.class).length > 0) {
@@ -179,6 +184,22 @@ public class OAuth2LoginTests {
 		assertThat(driver.getCurrentUrl()).startsWith("https://github.com/login/oauth/authorize");
 	}
 
+	// gh-9457
+	@Test
+	public void defaultLoginPageWithAuthorizationCodeAndClientCredentialsClientRegistrationThenRedirect() {
+		this.spring.register(OAuth2LoginWithAuthorizationCodeAndClientCredentialsClientRegistration.class).autowire();
+		// @formatter:off
+		WebTestClient webTestClient = WebTestClientBuilder
+				.bindToWebFilters(new GitHubWebFilter(), this.springSecurity)
+				.build();
+		WebDriver driver = WebTestClientHtmlUnitDriverBuilder
+				.webTestClientSetup(webTestClient)
+				.build();
+		// @formatter:on
+		driver.get("http://localhost/");
+		assertThat(driver.getCurrentUrl()).startsWith("https://github.com/login/oauth/authorize");
+	}
+
 	@Test
 	public void defaultLoginPageWithSingleClientRegistrationAndFormLoginThenLinks() {
 		this.spring.register(OAuth2LoginWithSingleClientRegistrations.class, OAuth2LoginWithFormLogin.class).autowire();
@@ -564,6 +585,16 @@ public class OAuth2LoginTests {
 
 	}
 
+	@EnableWebFluxSecurity
+	static class OAuth2LoginWithAuthorizationCodeAndClientCredentialsClientRegistration {
+
+		@Bean
+		InMemoryReactiveClientRegistrationRepository clientRegistrationRepository() {
+			return new InMemoryReactiveClientRegistrationRepository(github, clientCredentials);
+		}
+
+	}
+
 	@EnableWebFlux
 	static class OAuth2AuthorizeWithMockObjectsConfig {