Allow configuration of requires channel through nested builder

Issue: spring-projectsgh-5557

Author: eleftherias

config/src/main/java/org/springframework/security/config/annotation/web/builders/HttpSecurity.java

@@ -658,9 +658,10 @@ public PortMapperConfigurer<HttpSecurity> portMapper() throws Exception {
 	 * 	&#064;Override
 	 * 	protected void configure(HttpSecurity http) throws Exception {
 	 * 		http
-	 * 			.requiresChannel()
-	 * 				.anyRequest().requiresSecure()
-	 * 				.and()
+	 * 			.requiresChannel(requiresChannel ->
+	 * 				requiresChannel
+	 * 					.anyRequest().requiresSecure()
+	 * 			)
 	 * 			.portMapper(portMapper ->
 	 * 				portMapper
 	 * 					.http(9090).mapsTo(9443)
@@ -1894,6 +1895,52 @@ public ChannelSecurityConfigurer<HttpSecurity>.ChannelRequestMatcherRegistry req
 				.getRegistry();
 	}
 
+	/**
+	 * Configures channel security. In order for this configuration to be useful at least
+	 * one mapping to a required channel must be provided.
+	 *
+	 * <h2>Example Configuration</h2>
+	 *
+	 * The example below demonstrates how to require HTTPs for every request. Only
+	 * requiring HTTPS for some requests is supported, but not recommended since an
+	 * application that allows for HTTP introduces many security vulnerabilities. For one
+	 * such example, read about <a
+	 * href="https://en.wikipedia.org/wiki/Firesheep">Firesheep</a>.
+	 *
+	 * <pre>
+	 * &#064;Configuration
+	 * &#064;EnableWebSecurity
+	 * public class ChannelSecurityConfig extends WebSecurityConfigurerAdapter {
+	 *
+	 * 	&#064;Override
+	 * 	protected void configure(HttpSecurity http) throws Exception {
+	 * 		http
+	 * 			.authorizeRequests(authorizeRequests ->
+	 * 				authorizeRequests
+	 * 					.antMatchers(&quot;/**&quot;).hasRole(&quot;USER&quot;)
+	 * 			)
+	 * 			.formLogin(withDefaults())
+	 * 			.requiresChannel(requiresChannel ->
+	 * 				requiresChannel
+	 * 					.anyRequest().requiresSecure()
+	 * 			);
+	 * 	}
+	 * }
+	 * </pre>
+	 *
+	 * @param requiresChannelCustomizer the {@link Customizer} to provide more options for
+	 * the {@link ChannelSecurityConfigurer.ChannelRequestMatcherRegistry}
+	 * @return the {@link HttpSecurity} for further customizations
+	 * @throws Exception
+	 */
+	public HttpSecurity requiresChannel(Customizer<ChannelSecurityConfigurer<HttpSecurity>.ChannelRequestMatcherRegistry> requiresChannelCustomizer)
+			throws Exception {
+		ApplicationContext context = getContext();
+		requiresChannelCustomizer.customize(getOrApply(new ChannelSecurityConfigurer<>(context))
+				.getRegistry());
+		return HttpSecurity.this;
+	}
+
 	/**
 	 * Configures HTTP Basic authentication.
 	 *

config/src/test/java/org/springframework/security/config/annotation/web/configurers/ChannelSecurityConfigurerTests.java

@@ -135,4 +135,27 @@ protected void configure(HttpSecurity http) throws Exception {
 			// @formatter:on
 		}
 	}
+
+	@Test
+	public void requestWhenRequiresChannelConfiguredInLambdaThenRedirectsToHttps() throws Exception {
+		this.spring.register(RequiresChannelInLambdaConfig.class).autowire();
+
+		mvc.perform(get("/"))
+				.andExpect(redirectedUrl("https://localhost/"));
+	}
+
+	@EnableWebSecurity
+	static class RequiresChannelInLambdaConfig extends WebSecurityConfigurerAdapter {
+
+		@Override
+		protected void configure(HttpSecurity http) throws Exception {
+			// @formatter:off
+			http
+				.requiresChannel(requiresChannel ->
+					requiresChannel
+						.anyRequest().requiresSecure()
+			);
+			// @formatter:on
+		}
+	}
 }

config/src/test/java/org/springframework/security/config/annotation/web/configurers/PortMapperConfigurerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -79,9 +79,10 @@ static class HttpMapsToInLambdaConfig extends WebSecurityConfigurerAdapter {
 		protected void configure(HttpSecurity http) throws Exception {
 			// @formatter:off
 			http
-				.requiresChannel()
+				.requiresChannel(requiresChannel ->
+					requiresChannel
 					.anyRequest().requiresSecure()
-					.and()
+				)
 				.portMapper(portMapper ->
 					portMapper
 						.http(543).mapsTo(123)
@@ -106,9 +107,10 @@ protected void configure(HttpSecurity http) throws Exception {
 			customPortMapper.setPortMappings(Collections.singletonMap("543", "123"));
 			// @formatter:off
 			http
-				.requiresChannel()
-					.anyRequest().requiresSecure()
-					.and()
+				.requiresChannel(requiresChannel ->
+					requiresChannel
+						.anyRequest().requiresSecure()
+				)
 				.portMapper(portMapper ->
 					portMapper
 						.portMapper(customPortMapper)