Use jws-algorithm property in ReactiveOAuth2ResourceServerJwkConfiguration

See gh-20681

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/reactive/ReactiveOAuth2ResourceServerJwkConfiguration.java

@@ -31,6 +31,7 @@ import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.security.config.web.server.ServerHttpSecurity;
 import org.springframework.security.config.web.server.ServerHttpSecurity.OAuth2ResourceServerSpec;
+import org.springframework.security.oauth2.jose.jws.SignatureAlgorithm;
 import org.springframework.security.oauth2.jwt.JwtValidators;
 import org.springframework.security.oauth2.jwt.NimbusReactiveJwtDecoder;
 import org.springframework.security.oauth2.jwt.ReactiveJwtDecoder;
@@ -45,6 +46,7 @@ import org.springframework.security.web.server.SecurityWebFilterChain;
  * @author Madhura Bhave
  * @author Artsiom Yudovin
  * @author HaiTao Zhang
+ * @author Anastasiia Losieva
  */
 @Configuration(proxyBeanMethods = false)
 class ReactiveOAuth2ResourceServerJwkConfiguration {
@@ -62,8 +64,9 @@ class ReactiveOAuth2ResourceServerJwkConfiguration {
 		@Bean
 		@ConditionalOnProperty(name = "spring.security.oauth2.resourceserver.jwt.jwk-set-uri")
 		ReactiveJwtDecoder jwtDecoder() {
-			NimbusReactiveJwtDecoder nimbusReactiveJwtDecoder = new NimbusReactiveJwtDecoder(
-					this.properties.getJwkSetUri());
+			NimbusReactiveJwtDecoder nimbusReactiveJwtDecoder = NimbusReactiveJwtDecoder
+					.withJwkSetUri(this.properties.getJwkSetUri())
+					.jwsAlgorithm(SignatureAlgorithm.from(this.properties.getJwsAlgorithm())).build();
 			String issuerUri = this.properties.getIssuerUri();
 			if (issuerUri != null) {
 				nimbusReactiveJwtDecoder.setJwtValidator(JwtValidators.createDefaultWithIssuer(issuerUri));
@@ -76,7 +79,8 @@ class ReactiveOAuth2ResourceServerJwkConfiguration {
 		NimbusReactiveJwtDecoder jwtDecoderByPublicKeyValue() throws Exception {
 			RSAPublicKey publicKey = (RSAPublicKey) KeyFactory.getInstance("RSA")
 					.generatePublic(new X509EncodedKeySpec(getKeySpec(this.properties.readPublicKey())));
-			return NimbusReactiveJwtDecoder.withPublicKey(publicKey).build();
+			return NimbusReactiveJwtDecoder.withPublicKey(publicKey)
+					.signatureAlgorithm(SignatureAlgorithm.from(this.properties.getJwsAlgorithm())).build();
 		}
 
 		private byte[] getKeySpec(String keyValue) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/security/oauth2/resource/reactive/ReactiveOAuth2ResourceServerAutoConfigurationTests.java

@@ -20,10 +20,12 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Set;
 import java.util.stream.Stream;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.nimbusds.jose.JWSAlgorithm;
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
 import org.junit.jupiter.api.AfterEach;
@@ -68,6 +70,7 @@ import static org.mockito.Mockito.mock;
  * @author Madhura Bhave
  * @author Artsiom Yudovin
  * @author HaiTao Zhang
+ * @author Anastasiia Losieva
  */
 class ReactiveOAuth2ResourceServerAutoConfigurationTests {
 
@@ -94,6 +97,31 @@ class ReactiveOAuth2ResourceServerAutoConfigurationTests {
 				});
 	}
 
+	@SuppressWarnings("unchecked")
+	@Test
+	void autoConfigurationUsingJwkSetUriShouldConfigureResourceServerUsingJwsAlgorithm() {
+		this.contextRunner
+				.withPropertyValues("spring.security.oauth2.resourceserver.jwt.jwk-set-uri=https://jwk-set-uri.com",
+						"spring.security.oauth2.resourceserver.jwt.jws-algorithm=RS512")
+				.run((context) -> {
+					NimbusReactiveJwtDecoder nimbusReactiveJwtDecoder = context.getBean(NimbusReactiveJwtDecoder.class);
+					assertThat(nimbusReactiveJwtDecoder).extracting("jwtProcessor.arg$2")
+							.matches((algorithms) -> ((Set<JWSAlgorithm>) algorithms).contains(JWSAlgorithm.RS512));
+				});
+	}
+
+	@Test
+	void autoConfigurationUsingPublicKeyValueShouldConfigureResourceServerUsingJwsAlgorithm() {
+		this.contextRunner.withPropertyValues(
+				"spring.security.oauth2.resourceserver.jwt.public-key-location=classpath:public-key-location",
+				"spring.security.oauth2.resourceserver.jwt.jws-algorithm=RS384").run((context) -> {
+					NimbusReactiveJwtDecoder nimbusReactiveJwtDecoder = context.getBean(NimbusReactiveJwtDecoder.class);
+					assertThat(nimbusReactiveJwtDecoder)
+							.extracting("jwtProcessor.arg$1.jwsKeySelector.expectedJwsAlgorithm")
+							.isEqualTo(JWSAlgorithm.RS384);
+				});
+	}
+
 	@Test
 	void autoConfigurationShouldConfigureResourceServerUsingOidcIssuerUri() throws IOException {
 		this.server = new MockWebServer();