redirect-uri property supports 'baseRedirectUrl' uri variable

Fixes gh-4589

config/src/main/resources/org/springframework/security/config/oauth2/client/spring-security-oauth2-client-templates.properties

@@ -13,7 +13,7 @@ spring.security.oauth2.client.templates.google.client-alias=google
 # GitHub
 spring.security.oauth2.client.templates.github.client-authentication-method=basic
 spring.security.oauth2.client.templates.github.authorization-grant-type=authorization_code
-spring.security.oauth2.client.templates.github.redirect-uri={scheme}://{serverName}:{serverPort}{contextPath}/oauth2/authorize/code/{registrationId}
+spring.security.oauth2.client.templates.github.redirect-uri={baseRedirectUrl}/oauth2/authorize/code/{registrationId}
 spring.security.oauth2.client.templates.github.scope=user
 spring.security.oauth2.client.templates.github.authorization-uri=https://github.com/login/oauth/authorize
 spring.security.oauth2.client.templates.github.token-uri=https://github.com/login/oauth/access_token

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

@@ -160,6 +160,15 @@ public class AuthorizationCodeRequestRedirectFilter extends OncePerRequestFilter
 		uriVariables.put("contextPath", request.getContextPath());
 		uriVariables.put("registrationId", clientRegistration.getRegistrationId());
 
+		String baseRedirectUrl = UriComponentsBuilder.newInstance()
+			.scheme(request.getScheme())
+			.host(request.getServerName())
+			.port(request.getServerPort())
+			.path(request.getContextPath())
+			.build()
+			.toUriString();
+		uriVariables.put("baseRedirectUrl", baseRedirectUrl);
+
 		return UriComponentsBuilder.fromUriString(clientRegistration.getRedirectUri())
 			.buildAndExpand(uriVariables)
 			.toUriString();

samples/boot/oauth2login/src/main/resources/META-INF/oauth2-clients-defaults.yml

@@ -15,7 +15,7 @@ security:
         github:
           client-authentication-method: basic
           authorization-grant-type: authorization_code
-          redirect-uri: "{scheme}://{serverName}:{serverPort}{contextPath}/oauth2/authorize/code/{registrationId}"
+          redirect-uri: "{baseRedirectUrl}/oauth2/authorize/code/{registrationId}"
           scope: user
           authorization-uri: "https://github.com/login/oauth/authorize"
           token-uri: "https://github.com/login/oauth/access_token"