Return Mono<Void> in ServerCsrfTokenRequestHandler#handle

Returning Mono<Void> from ServerCsrfTokenRequestHandler#handle would
allow non-blocking response writes.

Closes: gh-16869

Signed-off-by: Andrey Litvitski <andrey1010102008@gmail.com>

Author: therepanic

web/src/main/java/org/springframework/security/web/server/csrf/ServerCsrfTokenRequestAttributeHandler.java

@@ -35,6 +35,7 @@
  *
  * @author Steve Riesenberg
  * @author Yoobin Yoon
+ * @author Andrey Litvitski
  * @since 5.8
  */
 public class ServerCsrfTokenRequestAttributeHandler implements ServerCsrfTokenRequestHandler {
@@ -44,11 +45,12 @@ public class ServerCsrfTokenRequestAttributeHandler implements ServerCsrfTokenRe
 	private boolean isTokenFromMultipartDataEnabled;
 
 	@Override
-	public void handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken) {
+	public Mono<Void> handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken) {
 		Assert.notNull(exchange, "exchange cannot be null");
 		Assert.notNull(csrfToken, "csrfToken cannot be null");
 		exchange.getAttributes().put(CsrfToken.class.getName(), csrfToken);
 		logger.trace(LogMessage.format("Wrote a CSRF token to the [%s] exchange attribute", CsrfToken.class.getName()));
+		return Mono.empty();
 	}
 
 	@Override

web/src/main/java/org/springframework/security/web/server/csrf/ServerCsrfTokenRequestHandler.java

@@ -41,7 +41,7 @@ public interface ServerCsrfTokenRequestHandler extends ServerCsrfTokenRequestRes
 	 * @param csrfToken the {@code Mono<CsrfToken>} created by the
 	 * {@link ServerCsrfTokenRepository}
 	 */
-	void handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken);
+	Mono<Void> handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken);
 
 	@Override
 	default Mono<String> resolveCsrfTokenValue(ServerWebExchange exchange, CsrfToken csrfToken) {

web/src/main/java/org/springframework/security/web/server/csrf/XorServerCsrfTokenRequestAttributeHandler.java

@@ -37,6 +37,7 @@
  *
  * @author Steve Riesenberg
  * @author Yoobin Yoon
+ * @author Andrey Litvitski
  * @since 5.8
  */
 public final class XorServerCsrfTokenRequestAttributeHandler extends ServerCsrfTokenRequestAttributeHandler {
@@ -56,15 +57,15 @@ public void setSecureRandom(SecureRandom secureRandom) {
 	}
 
 	@Override
-	public void handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken) {
+	public Mono<Void> handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken) {
 		Assert.notNull(exchange, "exchange cannot be null");
 		Assert.notNull(csrfToken, "csrfToken cannot be null");
 		Mono<CsrfToken> updatedCsrfToken = csrfToken
 			.map((token) -> new DefaultCsrfToken(token.getHeaderName(), token.getParameterName(),
 					createXoredCsrfToken(this.secureRandom, token.getToken())))
 			.cast(CsrfToken.class)
 			.cache();
-		super.handle(exchange, updatedCsrfToken);
+		return super.handle(exchange, updatedCsrfToken);
 	}
 
 	@Override