Create CsrfCustomizer for SPA configuration (#14149)

Author: felhag

config/src/main/java/org/springframework/security/config/annotation/web/configurers/CsrfCustomizer.java

@@ -0,0 +1,53 @@
+package org.springframework.security.config.annotation.web.configurers;
+
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.springframework.security.config.Customizer;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.web.csrf.*;
+import org.springframework.util.StringUtils;
+
+import java.util.function.Supplier;
+
+public class CsrfCustomizer {
+	public static Customizer<CsrfConfigurer<HttpSecurity>> spaDefaults() {
+		return (csrf) -> csrf
+				.csrfTokenRepository(CookieCsrfTokenRepository.withHttpOnlyFalse())
+				.csrfTokenRequestHandler(new SpaCsrfTokenRequestHandler());
+	}
+
+	private static class SpaCsrfTokenRequestHandler implements CsrfTokenRequestHandler {
+		private final CsrfTokenRequestHandler plain = new CsrfTokenRequestAttributeHandler();
+		private final CsrfTokenRequestHandler xor = new XorCsrfTokenRequestAttributeHandler();
+
+		@Override
+		public void handle(HttpServletRequest request, HttpServletResponse response, Supplier<CsrfToken> csrfToken) {
+			/*
+			 * Always use XorCsrfTokenRequestAttributeHandler to provide BREACH protection of
+			 * the CsrfToken when it is rendered in the response body.
+			 */
+			this.xor.handle(request, response, csrfToken);
+			/*
+			 * Render the token value to a cookie by causing the deferred token to be loaded.
+			 */
+			csrfToken.get();
+		}
+
+		@Override
+		public String resolveCsrfTokenValue(HttpServletRequest request, CsrfToken csrfToken) {
+			String headerValue = request.getHeader(csrfToken.getHeaderName());
+			/*
+			 * If the request contains a request header, use CsrfTokenRequestAttributeHandler
+			 * to resolve the CsrfToken. This applies when a single-page application includes
+			 * the header value automatically, which was obtained via a cookie containing the
+			 * raw CsrfToken.
+			 *
+			 * In all other cases (e.g. if the request contains a request parameter), use
+			 * XorCsrfTokenRequestAttributeHandler to resolve the CsrfToken. This applies
+			 * when a server-side rendered form includes the _csrf request parameter as a
+			 * hidden input.
+			 */
+			return (StringUtils.hasText(headerValue) ? this.plain : this.xor).resolveCsrfTokenValue(request, csrfToken);
+		}
+	}
+}