Add saml2.ValidIssuers parameter

Adds the saml2.ValidIssuers parameter into SAML 2.0 Assertion Validators

Closes gh-10335

saml2/saml2-service-provider/src/opensaml4Main/java/org/springframework/security/saml2/provider/service/authentication/OpenSaml4AuthenticationProvider.java

@@ -672,11 +672,14 @@ public final class OpenSaml4AuthenticationProvider implements AuthenticationProv
 
 	private static ValidationContext createValidationContext(AssertionToken assertionToken,
 			Consumer<Map<String, Object>> paramsConsumer) {
-		String audience = assertionToken.token.getRelyingPartyRegistration().getEntityId();
-		String recipient = assertionToken.token.getRelyingPartyRegistration().getAssertionConsumerServiceLocation();
+		RelyingPartyRegistration relyingPartyRegistration = assertionToken.token.getRelyingPartyRegistration();
+		String audience = relyingPartyRegistration.getEntityId();
+		String recipient = relyingPartyRegistration.getAssertionConsumerServiceLocation();
+		String assertingPartyEntityId = relyingPartyRegistration.getAssertingPartyDetails().getEntityId();
 		Map<String, Object> params = new HashMap<>();
 		params.put(SAML2AssertionValidationParameters.COND_VALID_AUDIENCES, Collections.singleton(audience));
 		params.put(SAML2AssertionValidationParameters.SC_VALID_RECIPIENTS, Collections.singleton(recipient));
+		params.put(SAML2AssertionValidationParameters.VALID_ISSUERS, Collections.singleton(assertingPartyEntityId));
 		paramsConsumer.accept(params);
 		return new ValidationContext(params);
 	}
@@ -754,6 +757,11 @@ public final class OpenSaml4AuthenticationProvider implements AuthenticationProv
 				protected ValidationResult validateStatements(Assertion assertion, ValidationContext context) {
 					return ValidationResult.VALID;
 				}
+
+				@Override
+				protected ValidationResult validateIssuer(Assertion assertion, ValidationContext context) {
+					return ValidationResult.VALID;
+				}
 			};
 
 		}

saml2/saml2-service-provider/src/opensaml4Test/java/org/springframework/security/saml2/provider/service/authentication/OpenSaml4AuthenticationProviderTests.java

@@ -628,6 +628,20 @@ public class OpenSaml4AuthenticationProviderTests {
 		verify(validator).convert(any(OpenSaml4AuthenticationProvider.ResponseToken.class));
 	}
 
+	@Test
+	public void authenticateWhenAssertionIssuerNotValidThenFailsWithInvalidIssuer() {
+		OpenSaml4AuthenticationProvider provider = new OpenSaml4AuthenticationProvider();
+		Response response = response();
+		Assertion assertion = assertion();
+		assertion.setIssuer(TestOpenSamlObjects.issuer("https://invalid.idp.test/saml2/idp"));
+		response.getAssertions().add(assertion);
+		TestOpenSamlObjects.signed(response, TestSaml2X509Credentials.assertingPartySigningCredential(),
+				ASSERTING_PARTY_ENTITY_ID);
+		Saml2AuthenticationToken token = token(response, verifying(registration()));
+		assertThatExceptionOfType(Saml2AuthenticationException.class).isThrownBy(() -> provider.authenticate(token))
+				.withMessageContaining("did not match any valid issuers");
+	}
+
 	private <T extends XMLObject> T build(QName qName) {
 		return (T) XMLObjectProviderRegistrySupport.getBuilderFactory().getBuilder(qName).buildObject(qName);
 	}