Add support reactive OneTimeToken customization

Closes gh-16939

Signed-off-by: Max Batischev <[email protected]>

Author: franticticktick

Diff for: web/src/main/java/org/springframework/security/web/server/authentication/ott/DefaultServerGenerateOneTimeTokenRequestResolver.java

@@ -17,6 +17,8 @@
 package org.springframework.security.web.server.authentication.ott;
 
 import java.time.Duration;
+import java.util.UUID;
+import java.util.function.Supplier;
 
 import reactor.core.publisher.Mono;
 
@@ -40,13 +42,15 @@ public final class DefaultServerGenerateOneTimeTokenRequestResolver
 
 	private Duration expiresIn = DEFAULT_EXPIRES_IN;
 
+	private Supplier<String> tokenValueFactory = () -> UUID.randomUUID().toString();
+
 	@Override
 	public Mono<GenerateOneTimeTokenRequest> resolve(ServerWebExchange exchange) {
 		// @formatter:off
 		return exchange.getFormData()
 				.mapNotNull((data) -> data.getFirst(USERNAME))
 				.switchIfEmpty(Mono.empty())
-				.map((username) -> new GenerateOneTimeTokenRequest(username, this.expiresIn));
+				.map((username) -> new GenerateOneTimeTokenRequest(username, this.expiresIn, this.tokenValueFactory.get()));
 		// @formatter:on
 	}
 
@@ -59,4 +63,14 @@ public void setExpiresIn(Duration expiresIn) {
 		this.expiresIn = expiresIn;
 	}
 
+	/**
+	 * Sets factory for token value generation
+	 * @param tokenValueFactory factory for token value generation
+	 * @since 6.5
+	 */
+	public void setTokenValueFactory(Supplier<String> tokenValueFactory) {
+		Assert.notNull(tokenValueFactory, "tokenValueFactory cannot be null");
+		this.tokenValueFactory = tokenValueFactory;
+	}
+
 }

Diff for: web/src/test/java/org/springframework/security/web/server/authentication/ott/DefaultServerGenerateOneTimeTokenRequestResolverTests.java

@@ -71,4 +71,16 @@ void resolveWhenExpiresInSetThenResolvesGenerateRequest() {
 		assertThat(generateRequest.getExpiresIn()).isEqualTo(Duration.ofSeconds(600));
 	}
 
+	@Test
+	void resolveWhenTokenValueFactorySetThenResolvesGenerateRequest() {
+		MockServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.post("/ott/generate")
+			.contentType(MediaType.APPLICATION_FORM_URLENCODED)
+			.body("username=user"));
+		this.resolver.setTokenValueFactory(() -> "tokenValue");
+
+		GenerateOneTimeTokenRequest generateRequest = this.resolver.resolve(exchange).block();
+
+		assertThat(generateRequest.getTokenValue()).isEqualTo("tokenValue");
+	}
+
 }