Add Internal OpenSAML API

This will be useful for exposing OpenSAML functionality at
a higher level. Each OpenSAML major version release should
provide a new implementation.

Issue gh-11658

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/internal/OpenSaml4Template.java

@@ -0,0 +1,617 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.saml2.internal;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.security.PrivateKey;
+import java.security.cert.X509Certificate;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import javax.xml.namespace.QName;
+
+import net.shibboleth.utilities.java.support.resolver.CriteriaSet;
+import net.shibboleth.utilities.java.support.xml.SerializeSupport;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.opensaml.core.criterion.EntityIdCriterion;
+import org.opensaml.core.xml.XMLObject;
+import org.opensaml.core.xml.XMLObjectBuilder;
+import org.opensaml.core.xml.config.XMLObjectProviderRegistrySupport;
+import org.opensaml.core.xml.io.Marshaller;
+import org.opensaml.core.xml.io.MarshallingException;
+import org.opensaml.core.xml.io.Unmarshaller;
+import org.opensaml.core.xml.io.UnmarshallerFactory;
+import org.opensaml.core.xml.util.XMLObjectSupport;
+import org.opensaml.saml.common.xml.SAMLConstants;
+import org.opensaml.saml.criterion.ProtocolCriterion;
+import org.opensaml.saml.ext.saml2delrestrict.Delegate;
+import org.opensaml.saml.ext.saml2delrestrict.DelegationRestrictionType;
+import org.opensaml.saml.metadata.criteria.role.impl.EvaluableProtocolRoleDescriptorCriterion;
+import org.opensaml.saml.saml2.core.Assertion;
+import org.opensaml.saml.saml2.core.Attribute;
+import org.opensaml.saml.saml2.core.AttributeStatement;
+import org.opensaml.saml.saml2.core.Condition;
+import org.opensaml.saml.saml2.core.EncryptedAssertion;
+import org.opensaml.saml.saml2.core.EncryptedAttribute;
+import org.opensaml.saml.saml2.core.Issuer;
+import org.opensaml.saml.saml2.core.LogoutRequest;
+import org.opensaml.saml.saml2.core.NameID;
+import org.opensaml.saml.saml2.core.RequestAbstractType;
+import org.opensaml.saml.saml2.core.Response;
+import org.opensaml.saml.saml2.core.StatusResponseType;
+import org.opensaml.saml.saml2.core.Subject;
+import org.opensaml.saml.saml2.core.SubjectConfirmation;
+import org.opensaml.saml.saml2.encryption.Decrypter;
+import org.opensaml.saml.saml2.encryption.EncryptedElementTypeEncryptedKeyResolver;
+import org.opensaml.saml.security.impl.SAMLMetadataSignatureSigningParametersResolver;
+import org.opensaml.saml.security.impl.SAMLSignatureProfileValidator;
+import org.opensaml.security.SecurityException;
+import org.opensaml.security.credential.BasicCredential;
+import org.opensaml.security.credential.Credential;
+import org.opensaml.security.credential.CredentialResolver;
+import org.opensaml.security.credential.CredentialSupport;
+import org.opensaml.security.credential.UsageType;
+import org.opensaml.security.credential.criteria.impl.EvaluableEntityIDCredentialCriterion;
+import org.opensaml.security.credential.criteria.impl.EvaluableUsageCredentialCriterion;
+import org.opensaml.security.credential.impl.CollectionCredentialResolver;
+import org.opensaml.security.criteria.UsageCriterion;
+import org.opensaml.security.x509.BasicX509Credential;
+import org.opensaml.xmlsec.SignatureSigningParameters;
+import org.opensaml.xmlsec.SignatureSigningParametersResolver;
+import org.opensaml.xmlsec.config.impl.DefaultSecurityConfigurationBootstrap;
+import org.opensaml.xmlsec.criterion.SignatureSigningConfigurationCriterion;
+import org.opensaml.xmlsec.crypto.XMLSigningUtil;
+import org.opensaml.xmlsec.encryption.support.ChainingEncryptedKeyResolver;
+import org.opensaml.xmlsec.encryption.support.DecryptionException;
+import org.opensaml.xmlsec.encryption.support.EncryptedKeyResolver;
+import org.opensaml.xmlsec.encryption.support.InlineEncryptedKeyResolver;
+import org.opensaml.xmlsec.encryption.support.SimpleRetrievalMethodEncryptedKeyResolver;
+import org.opensaml.xmlsec.impl.BasicSignatureSigningConfiguration;
+import org.opensaml.xmlsec.keyinfo.KeyInfoCredentialResolver;
+import org.opensaml.xmlsec.keyinfo.KeyInfoGeneratorManager;
+import org.opensaml.xmlsec.keyinfo.NamedKeyInfoGeneratorManager;
+import org.opensaml.xmlsec.keyinfo.impl.CollectionKeyInfoCredentialResolver;
+import org.opensaml.xmlsec.keyinfo.impl.X509KeyInfoGeneratorFactory;
+import org.opensaml.xmlsec.signature.SignableXMLObject;
+import org.opensaml.xmlsec.signature.Signature;
+import org.opensaml.xmlsec.signature.support.SignatureConstants;
+import org.opensaml.xmlsec.signature.support.SignatureSupport;
+import org.opensaml.xmlsec.signature.support.SignatureTrustEngine;
+import org.opensaml.xmlsec.signature.support.impl.ExplicitKeySignatureTrustEngine;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+
+import org.springframework.security.saml2.Saml2Exception;
+import org.springframework.security.saml2.core.Saml2Error;
+import org.springframework.security.saml2.core.Saml2ErrorCodes;
+import org.springframework.security.saml2.core.Saml2ParameterNames;
+import org.springframework.security.saml2.core.Saml2X509Credential;
+import org.springframework.util.Assert;
+import org.springframework.web.util.UriComponentsBuilder;
+import org.springframework.web.util.UriUtils;
+
+/**
+ * For internal use only. Subject to breaking changes at any time.
+ */
+final class OpenSaml4Template implements OpenSamlOperations {
+
+	private static final Log logger = LogFactory.getLog(OpenSaml4Template.class);
+
+	@Override
+	public <T extends XMLObject> T build(QName elementName) {
+		XMLObjectBuilder<?> builder = XMLObjectProviderRegistrySupport.getBuilderFactory().getBuilder(elementName);
+		if (builder == null) {
+			throw new Saml2Exception("Unable to resolve Builder for " + elementName);
+		}
+		return (T) builder.buildObject(elementName);
+	}
+
+	@Override
+	public <T extends XMLObject> T deserialize(String serialized) {
+		return deserialize(new ByteArrayInputStream(serialized.getBytes(StandardCharsets.UTF_8)));
+	}
+
+	@Override
+	public <T extends XMLObject> T deserialize(InputStream serialized) {
+		try {
+			Document document = XMLObjectProviderRegistrySupport.getParserPool().parse(serialized);
+			Element element = document.getDocumentElement();
+			UnmarshallerFactory factory = XMLObjectProviderRegistrySupport.getUnmarshallerFactory();
+			Unmarshaller unmarshaller = factory.getUnmarshaller(element);
+			if (unmarshaller == null) {
+				throw new Saml2Exception("Unsupported element of type " + element.getTagName());
+			}
+			return (T) unmarshaller.unmarshall(element);
+		}
+		catch (Saml2Exception ex) {
+			throw ex;
+		}
+		catch (Exception ex) {
+			throw new Saml2Exception("Failed to deserialize payload", ex);
+		}
+	}
+
+	@Override
+	public OpenSaml4SerializationConfigurer serialize(XMLObject object) {
+		Marshaller marshaller = XMLObjectProviderRegistrySupport.getMarshallerFactory().getMarshaller(object);
+		try {
+			return serialize(marshaller.marshall(object));
+		}
+		catch (MarshallingException ex) {
+			throw new Saml2Exception(ex);
+		}
+	}
+
+	@Override
+	public OpenSaml4SerializationConfigurer serialize(Element element) {
+		return new OpenSaml4SerializationConfigurer(element);
+	}
+
+	@Override
+	public OpenSaml4SignatureConfigurer withSigningKeys(Collection<Saml2X509Credential> credentials) {
+		return new OpenSaml4SignatureConfigurer(credentials);
+	}
+
+	@Override
+	public OpenSaml4VerificationConfigurer withVerificationKeys(Collection<Saml2X509Credential> credentials) {
+		return new OpenSaml4VerificationConfigurer(credentials);
+	}
+
+	@Override
+	public OpenSaml4DecryptionConfigurer withDecryptionKeys(Collection<Saml2X509Credential> credentials) {
+		return new OpenSaml4DecryptionConfigurer(credentials);
+	}
+
+	OpenSaml4Template() {
+
+	}
+
+	static final class OpenSaml4SerializationConfigurer
+			implements SerializationConfigurer<OpenSaml4SerializationConfigurer> {
+
+		private final Element element;
+
+		boolean pretty;
+
+		OpenSaml4SerializationConfigurer(Element element) {
+			this.element = element;
+		}
+
+		@Override
+		public OpenSaml4SerializationConfigurer prettyPrint(boolean pretty) {
+			this.pretty = pretty;
+			return this;
+		}
+
+		@Override
+		public String serialize() {
+			if (this.pretty) {
+				return SerializeSupport.prettyPrintXML(this.element);
+			}
+			return SerializeSupport.nodeToString(this.element);
+		}
+
+	}
+
+	static final class OpenSaml4SignatureConfigurer implements SignatureConfigurer<OpenSaml4SignatureConfigurer> {
+
+		private final Collection<Saml2X509Credential> credentials;
+
+		private final Map<String, String> components = new LinkedHashMap<>();
+
+		private List<String> algs = List.of(SignatureConstants.ALGO_ID_SIGNATURE_RSA_SHA256);
+
+		OpenSaml4SignatureConfigurer(Collection<Saml2X509Credential> credentials) {
+			this.credentials = credentials;
+		}
+
+		@Override
+		public OpenSaml4SignatureConfigurer algorithms(List<String> algs) {
+			this.algs = algs;
+			return this;
+		}
+
+		@Override
+		public <O extends SignableXMLObject> O sign(O object) {
+			SignatureSigningParameters parameters = resolveSigningParameters();
+			try {
+				SignatureSupport.signObject(object, parameters);
+			}
+			catch (Exception ex) {
+				throw new Saml2Exception(ex);
+			}
+			return object;
+		}
+
+		@Override
+		public Map<String, String> sign(Map<String, String> params) {
+			SignatureSigningParameters parameters = resolveSigningParameters();
+			this.components.putAll(params);
+			Credential credential = parameters.getSigningCredential();
+			String algorithmUri = parameters.getSignatureAlgorithm();
+			this.components.put(Saml2ParameterNames.SIG_ALG, algorithmUri);
+			UriComponentsBuilder builder = UriComponentsBuilder.newInstance();
+			for (Map.Entry<String, String> component : this.components.entrySet()) {
+				builder.queryParam(component.getKey(),
+						UriUtils.encode(component.getValue(), StandardCharsets.ISO_8859_1));
+			}
+			String queryString = builder.build(true).toString().substring(1);
+			try {
+				byte[] rawSignature = XMLSigningUtil.signWithURI(credential, algorithmUri,
+						queryString.getBytes(StandardCharsets.UTF_8));
+				String b64Signature = Saml2Utils.samlEncode(rawSignature);
+				this.components.put(Saml2ParameterNames.SIGNATURE, b64Signature);
+			}
+			catch (SecurityException ex) {
+				throw new Saml2Exception(ex);
+			}
+			return this.components;
+		}
+
+		private SignatureSigningParameters resolveSigningParameters() {
+			List<Credential> credentials = resolveSigningCredentials();
+			List<String> digests = Collections.singletonList(SignatureConstants.ALGO_ID_DIGEST_SHA256);
+			String canonicalization = SignatureConstants.ALGO_ID_C14N_EXCL_OMIT_COMMENTS;
+			SignatureSigningParametersResolver resolver = new SAMLMetadataSignatureSigningParametersResolver();
+			BasicSignatureSigningConfiguration signingConfiguration = new BasicSignatureSigningConfiguration();
+			signingConfiguration.setSigningCredentials(credentials);
+			signingConfiguration.setSignatureAlgorithms(this.algs);
+			signingConfiguration.setSignatureReferenceDigestMethods(digests);
+			signingConfiguration.setSignatureCanonicalizationAlgorithm(canonicalization);
+			signingConfiguration.setKeyInfoGeneratorManager(buildSignatureKeyInfoGeneratorManager());
+			CriteriaSet criteria = new CriteriaSet(new SignatureSigningConfigurationCriterion(signingConfiguration));
+			try {
+				SignatureSigningParameters parameters = resolver.resolveSingle(criteria);
+				Assert.notNull(parameters, "Failed to resolve any signing credential");
+				return parameters;
+			}
+			catch (Exception ex) {
+				throw new Saml2Exception(ex);
+			}
+		}
+
+		private NamedKeyInfoGeneratorManager buildSignatureKeyInfoGeneratorManager() {
+			final NamedKeyInfoGeneratorManager namedManager = new NamedKeyInfoGeneratorManager();
+
+			namedManager.setUseDefaultManager(true);
+			final KeyInfoGeneratorManager defaultManager = namedManager.getDefaultManager();
+
+			// Generator for X509Credentials
+			final X509KeyInfoGeneratorFactory x509Factory = new X509KeyInfoGeneratorFactory();
+			x509Factory.setEmitEntityCertificate(true);
+			x509Factory.setEmitEntityCertificateChain(true);
+
+			defaultManager.registerFactory(x509Factory);
+
+			return namedManager;
+		}
+
+		private List<Credential> resolveSigningCredentials() {
+			List<Credential> credentials = new ArrayList<>();
+			for (Saml2X509Credential x509Credential : this.credentials) {
+				X509Certificate certificate = x509Credential.getCertificate();
+				PrivateKey privateKey = x509Credential.getPrivateKey();
+				BasicCredential credential = CredentialSupport.getSimpleCredential(certificate, privateKey);
+				credential.setUsageType(UsageType.SIGNING);
+				credentials.add(credential);
+			}
+			return credentials;
+		}
+
+	}
+
+	static final class OpenSaml4VerificationConfigurer implements VerificationConfigurer {
+
+		private final Collection<Saml2X509Credential> credentials;
+
+		private String entityId;
+
+		OpenSaml4VerificationConfigurer(Collection<Saml2X509Credential> credentials) {
+			this.credentials = credentials;
+		}
+
+		@Override
+		public VerificationConfigurer entityId(String entityId) {
+			this.entityId = entityId;
+			return this;
+		}
+
+		private SignatureTrustEngine trustEngine(Collection<Saml2X509Credential> keys) {
+			Set<Credential> credentials = new HashSet<>();
+			for (Saml2X509Credential key : keys) {
+				BasicX509Credential cred = new BasicX509Credential(key.getCertificate());
+				cred.setUsageType(UsageType.SIGNING);
+				cred.setEntityId(this.entityId);
+				credentials.add(cred);
+			}
+			CredentialResolver credentialsResolver = new CollectionCredentialResolver(credentials);
+			return new ExplicitKeySignatureTrustEngine(credentialsResolver,
+					DefaultSecurityConfigurationBootstrap.buildBasicInlineKeyInfoCredentialResolver());
+		}
+
+		private CriteriaSet verificationCriteria(Issuer issuer) {
+			return new CriteriaSet(new EvaluableEntityIDCredentialCriterion(new EntityIdCriterion(issuer.getValue())),
+					new EvaluableProtocolRoleDescriptorCriterion(new ProtocolCriterion(SAMLConstants.SAML20P_NS)),
+					new EvaluableUsageCredentialCriterion(new UsageCriterion(UsageType.SIGNING)));
+		}
+
+		@Override
+		public Collection<Saml2Error> verify(SignableXMLObject signable) {
+			if (signable instanceof StatusResponseType response) {
+				return verifySignature(response.getID(), response.getIssuer(), response.getSignature());
+			}
+			if (signable instanceof RequestAbstractType request) {
+				return verifySignature(request.getID(), request.getIssuer(), request.getSignature());
+			}
+			if (signable instanceof Assertion assertion) {
+				return verifySignature(assertion.getID(), assertion.getIssuer(), assertion.getSignature());
+			}
+			throw new Saml2Exception("Unsupported object of type: " + signable.getClass().getName());
+		}
+
+		private Collection<Saml2Error> verifySignature(String id, Issuer issuer, Signature signature) {
+			SignatureTrustEngine trustEngine = trustEngine(this.credentials);
+			CriteriaSet criteria = verificationCriteria(issuer);
+			Collection<Saml2Error> errors = new ArrayList<>();
+			SAMLSignatureProfileValidator profileValidator = new SAMLSignatureProfileValidator();
+			try {
+				profileValidator.validate(signature);
+			}
+			catch (Exception ex) {
+				errors.add(new Saml2Error(Saml2ErrorCodes.INVALID_SIGNATURE,
+						"Invalid signature for object [" + id + "]: "));
+			}
+
+			try {
+				if (!trustEngine.validate(signature, criteria)) {
+					errors.add(new Saml2Error(Saml2ErrorCodes.INVALID_SIGNATURE,
+							"Invalid signature for object [" + id + "]"));
+				}
+			}
+			catch (Exception ex) {
+				errors.add(new Saml2Error(Saml2ErrorCodes.INVALID_SIGNATURE,
+						"Invalid signature for object [" + id + "]: "));
+			}
+
+			return errors;
+		}
+
+		@Override
+		public Collection<Saml2Error> verify(RedirectParameters parameters) {
+			SignatureTrustEngine trustEngine = trustEngine(this.credentials);
+			CriteriaSet criteria = verificationCriteria(parameters.getIssuer());
+			if (parameters.getAlgorithm() == null) {
+				return Collections.singletonList(new Saml2Error(Saml2ErrorCodes.INVALID_SIGNATURE,
+						"Missing signature algorithm for object [" + parameters.getId() + "]"));
+			}
+			if (!parameters.hasSignature()) {
+				return Collections.singletonList(new Saml2Error(Saml2ErrorCodes.INVALID_SIGNATURE,
+						"Missing signature for object [" + parameters.getId() + "]"));
+			}
+			Collection<Saml2Error> errors = new ArrayList<>();
+			String algorithmUri = parameters.getAlgorithm();
+			try {
+				if (!trustEngine.validate(parameters.getSignature(), parameters.getContent(), algorithmUri, criteria,
+						null)) {
+					errors.add(new Saml2Error(Saml2ErrorCodes.INVALID_SIGNATURE,
+							"Invalid signature for object [" + parameters.getId() + "]"));
+				}
+			}
+			catch (Exception ex) {
+				errors.add(new Saml2Error(Saml2ErrorCodes.INVALID_SIGNATURE,
+						"Invalid signature for object [" + parameters.getId() + "]: "));
+			}
+			return errors;
+		}
+
+	}
+
+	static final class OpenSaml4DecryptionConfigurer implements DecryptionConfigurer {
+
+		private static final EncryptedKeyResolver encryptedKeyResolver = new ChainingEncryptedKeyResolver(
+				Arrays.asList(new InlineEncryptedKeyResolver(), new EncryptedElementTypeEncryptedKeyResolver(),
+						new SimpleRetrievalMethodEncryptedKeyResolver()));
+
+		private final Decrypter decrypter;
+
+		OpenSaml4DecryptionConfigurer(Collection<Saml2X509Credential> decryptionCredentials) {
+			this.decrypter = decrypter(decryptionCredentials);
+		}
+
+		private static Decrypter decrypter(Collection<Saml2X509Credential> decryptionCredentials) {
+			Collection<Credential> credentials = new ArrayList<>();
+			for (Saml2X509Credential key : decryptionCredentials) {
+				Credential cred = CredentialSupport.getSimpleCredential(key.getCertificate(), key.getPrivateKey());
+				credentials.add(cred);
+			}
+			KeyInfoCredentialResolver resolver = new CollectionKeyInfoCredentialResolver(credentials);
+			Decrypter decrypter = new Decrypter(null, resolver, encryptedKeyResolver);
+			decrypter.setRootInNewDocument(true);
+			return decrypter;
+		}
+
+		@Override
+		public void decrypt(XMLObject object) {
+			if (object instanceof Response response) {
+				decryptResponse(response);
+				return;
+			}
+			if (object instanceof Assertion assertion) {
+				decryptAssertion(assertion);
+			}
+			if (object instanceof LogoutRequest request) {
+				decryptLogoutRequest(request);
+			}
+		}
+
+		/*
+		 * The methods that follow are adapted from OpenSAML's {@link DecryptAssertions},
+		 * {@link DecryptNameIDs}, and {@link DecryptAttributes}.
+		 *
+		 * <p>The reason that these OpenSAML classes are not used directly is because they
+		 * reference {@link javax.servlet.http.HttpServletRequest} which is a lower
+		 * Servlet API version than what Spring Security SAML uses.
+		 *
+		 * If OpenSAML 5 updates to {@link jakarta.servlet.http.HttpServletRequest}, then
+		 * this arrangement can be revisited.
+		 */
+
+		private void decryptResponse(Response response) {
+			Collection<Assertion> decrypteds = new ArrayList<>();
+			Collection<EncryptedAssertion> encrypteds = new ArrayList<>();
+
+			int count = 0;
+			int size = response.getEncryptedAssertions().size();
+			for (EncryptedAssertion encrypted : response.getEncryptedAssertions()) {
+				logger.trace(String.format("Decrypting EncryptedAssertion (%d/%d) in Response [%s]", count, size,
+						response.getID()));
+				try {
+					Assertion decrypted = this.decrypter.decrypt(encrypted);
+					if (decrypted != null) {
+						encrypteds.add(encrypted);
+						decrypteds.add(decrypted);
+					}
+					count++;
+				}
+				catch (DecryptionException ex) {
+					throw new Saml2Exception(ex);
+				}
+			}
+
+			response.getEncryptedAssertions().removeAll(encrypteds);
+			response.getAssertions().addAll(decrypteds);
+
+			// Re-marshall the response so that any ID attributes within the decrypted
+			// Assertions
+			// will have their ID-ness re-established at the DOM level.
+			if (!decrypteds.isEmpty()) {
+				try {
+					XMLObjectSupport.marshall(response);
+				}
+				catch (final MarshallingException ex) {
+					throw new Saml2Exception(ex);
+				}
+			}
+		}
+
+		private void decryptAssertion(Assertion assertion) {
+			for (AttributeStatement statement : assertion.getAttributeStatements()) {
+				decryptAttributes(statement);
+			}
+			decryptSubject(assertion.getSubject());
+			if (assertion.getConditions() != null) {
+				for (Condition c : assertion.getConditions().getConditions()) {
+					if (!(c instanceof DelegationRestrictionType delegation)) {
+						continue;
+					}
+					for (Delegate d : delegation.getDelegates()) {
+						if (d.getEncryptedID() != null) {
+							try {
+								NameID decrypted = (NameID) this.decrypter.decrypt(d.getEncryptedID());
+								if (decrypted != null) {
+									d.setNameID(decrypted);
+									d.setEncryptedID(null);
+								}
+							}
+							catch (DecryptionException ex) {
+								throw new Saml2Exception(ex);
+							}
+						}
+					}
+				}
+			}
+		}
+
+		private void decryptAttributes(AttributeStatement statement) {
+			Collection<Attribute> decrypteds = new ArrayList<>();
+			Collection<EncryptedAttribute> encrypteds = new ArrayList<>();
+			for (EncryptedAttribute encrypted : statement.getEncryptedAttributes()) {
+				try {
+					Attribute decrypted = this.decrypter.decrypt(encrypted);
+					if (decrypted != null) {
+						encrypteds.add(encrypted);
+						decrypteds.add(decrypted);
+					}
+				}
+				catch (Exception ex) {
+					throw new Saml2Exception(ex);
+				}
+			}
+			statement.getEncryptedAttributes().removeAll(encrypteds);
+			statement.getAttributes().addAll(decrypteds);
+		}
+
+		private void decryptSubject(Subject subject) {
+			if (subject != null) {
+				if (subject.getEncryptedID() != null) {
+					try {
+						NameID decrypted = (NameID) this.decrypter.decrypt(subject.getEncryptedID());
+						if (decrypted != null) {
+							subject.setNameID(decrypted);
+							subject.setEncryptedID(null);
+						}
+					}
+					catch (final DecryptionException ex) {
+						throw new Saml2Exception(ex);
+					}
+				}
+
+				for (final SubjectConfirmation sc : subject.getSubjectConfirmations()) {
+					if (sc.getEncryptedID() != null) {
+						try {
+							NameID decrypted = (NameID) this.decrypter.decrypt(sc.getEncryptedID());
+							if (decrypted != null) {
+								sc.setNameID(decrypted);
+								sc.setEncryptedID(null);
+							}
+						}
+						catch (final DecryptionException ex) {
+							throw new Saml2Exception(ex);
+						}
+					}
+				}
+			}
+		}
+
+		private void decryptLogoutRequest(LogoutRequest request) {
+			if (request.getEncryptedID() != null) {
+				try {
+					NameID decrypted = (NameID) this.decrypter.decrypt(request.getEncryptedID());
+					if (decrypted != null) {
+						request.setNameID(decrypted);
+						request.setEncryptedID(null);
+					}
+				}
+				catch (DecryptionException ex) {
+					throw new Saml2Exception(ex);
+				}
+			}
+		}
+
+	}
+
+}

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/internal/OpenSamlOperations.java

@@ -0,0 +1,184 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.saml2.internal;
+
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import javax.xml.namespace.QName;
+
+import org.opensaml.core.xml.XMLObject;
+import org.opensaml.saml.saml2.core.Issuer;
+import org.opensaml.saml.saml2.core.RequestAbstractType;
+import org.opensaml.saml.saml2.core.StatusResponseType;
+import org.opensaml.xmlsec.signature.SignableXMLObject;
+import org.w3c.dom.Element;
+
+import org.springframework.security.saml2.core.Saml2Error;
+import org.springframework.security.saml2.core.Saml2ParameterNames;
+import org.springframework.security.saml2.core.Saml2X509Credential;
+import org.springframework.web.util.UriComponentsBuilder;
+
+interface OpenSamlOperations {
+
+	<T extends XMLObject> T build(QName elementName);
+
+	<T extends XMLObject> T deserialize(String serialized);
+
+	<T extends XMLObject> T deserialize(InputStream serialized);
+
+	SerializationConfigurer<?> serialize(XMLObject object);
+
+	SerializationConfigurer<?> serialize(Element element);
+
+	SignatureConfigurer<?> withSigningKeys(Collection<Saml2X509Credential> credentials);
+
+	VerificationConfigurer withVerificationKeys(Collection<Saml2X509Credential> credentials);
+
+	DecryptionConfigurer withDecryptionKeys(Collection<Saml2X509Credential> credentials);
+
+	interface SerializationConfigurer<B extends SerializationConfigurer<B>> {
+
+		B prettyPrint(boolean pretty);
+
+		String serialize();
+
+	}
+
+	interface SignatureConfigurer<B extends SignatureConfigurer<B>> {
+
+		B algorithms(List<String> algs);
+
+		<O extends SignableXMLObject> O sign(O object);
+
+		Map<String, String> sign(Map<String, String> params);
+
+	}
+
+	interface VerificationConfigurer {
+
+		VerificationConfigurer entityId(String entityId);
+
+		Collection<Saml2Error> verify(SignableXMLObject signable);
+
+		Collection<Saml2Error> verify(VerificationConfigurer.RedirectParameters parameters);
+
+		final class RedirectParameters {
+
+			private final String id;
+
+			private final Issuer issuer;
+
+			private final String algorithm;
+
+			private final byte[] signature;
+
+			private final byte[] content;
+
+			RedirectParameters(Map<String, String> parameters, String parametersQuery, RequestAbstractType request) {
+				this.id = request.getID();
+				this.issuer = request.getIssuer();
+				this.algorithm = parameters.get(Saml2ParameterNames.SIG_ALG);
+				if (parameters.get(Saml2ParameterNames.SIGNATURE) != null) {
+					this.signature = Saml2Utils.samlDecode(parameters.get(Saml2ParameterNames.SIGNATURE));
+				}
+				else {
+					this.signature = null;
+				}
+				Map<String, String> queryParams = UriComponentsBuilder.newInstance()
+					.query(parametersQuery)
+					.build(true)
+					.getQueryParams()
+					.toSingleValueMap();
+				String relayState = parameters.get(Saml2ParameterNames.RELAY_STATE);
+				this.content = getContent(Saml2ParameterNames.SAML_REQUEST, relayState, queryParams);
+			}
+
+			RedirectParameters(Map<String, String> parameters, String parametersQuery, StatusResponseType response) {
+				this.id = response.getID();
+				this.issuer = response.getIssuer();
+				this.algorithm = parameters.get(Saml2ParameterNames.SIG_ALG);
+				if (parameters.get(Saml2ParameterNames.SIGNATURE) != null) {
+					this.signature = Saml2Utils.samlDecode(parameters.get(Saml2ParameterNames.SIGNATURE));
+				}
+				else {
+					this.signature = null;
+				}
+				Map<String, String> queryParams = UriComponentsBuilder.newInstance()
+					.query(parametersQuery)
+					.build(true)
+					.getQueryParams()
+					.toSingleValueMap();
+				String relayState = parameters.get(Saml2ParameterNames.RELAY_STATE);
+				this.content = getContent(Saml2ParameterNames.SAML_RESPONSE, relayState, queryParams);
+			}
+
+			static byte[] getContent(String samlObject, String relayState, final Map<String, String> queryParams) {
+				if (Objects.nonNull(relayState)) {
+					return String
+						.format("%s=%s&%s=%s&%s=%s", samlObject, queryParams.get(samlObject),
+								Saml2ParameterNames.RELAY_STATE, queryParams.get(Saml2ParameterNames.RELAY_STATE),
+								Saml2ParameterNames.SIG_ALG, queryParams.get(Saml2ParameterNames.SIG_ALG))
+						.getBytes(StandardCharsets.UTF_8);
+				}
+				else {
+					return String
+						.format("%s=%s&%s=%s", samlObject, queryParams.get(samlObject), Saml2ParameterNames.SIG_ALG,
+								queryParams.get(Saml2ParameterNames.SIG_ALG))
+						.getBytes(StandardCharsets.UTF_8);
+				}
+			}
+
+			String getId() {
+				return this.id;
+			}
+
+			Issuer getIssuer() {
+				return this.issuer;
+			}
+
+			byte[] getContent() {
+				return this.content;
+			}
+
+			String getAlgorithm() {
+				return this.algorithm;
+			}
+
+			byte[] getSignature() {
+				return this.signature;
+			}
+
+			boolean hasSignature() {
+				return this.signature != null;
+			}
+
+		}
+
+	}
+
+	interface DecryptionConfigurer {
+
+		void decrypt(XMLObject object);
+
+	}
+
+}

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/internal/Saml2Utils.java

@@ -0,0 +1,196 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.saml2.internal;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.Base64;
+import java.util.zip.Deflater;
+import java.util.zip.DeflaterOutputStream;
+import java.util.zip.Inflater;
+import java.util.zip.InflaterOutputStream;
+
+import org.springframework.security.saml2.Saml2Exception;
+
+/**
+ * Utility methods for working with serialized SAML messages.
+ *
+ * For internal use only.
+ *
+ * @author Josh Cummings
+ */
+final class Saml2Utils {
+
+	private Saml2Utils() {
+	}
+
+	static String samlEncode(byte[] b) {
+		return Base64.getEncoder().encodeToString(b);
+	}
+
+	static byte[] samlDecode(String s) {
+		return Base64.getMimeDecoder().decode(s);
+	}
+
+	static byte[] samlDeflate(String s) {
+		try {
+			ByteArrayOutputStream b = new ByteArrayOutputStream();
+			DeflaterOutputStream deflater = new DeflaterOutputStream(b, new Deflater(Deflater.DEFLATED, true));
+			deflater.write(s.getBytes(StandardCharsets.UTF_8));
+			deflater.finish();
+			return b.toByteArray();
+		}
+		catch (IOException ex) {
+			throw new Saml2Exception("Unable to deflate string", ex);
+		}
+	}
+
+	static String samlInflate(byte[] b) {
+		try {
+			ByteArrayOutputStream out = new ByteArrayOutputStream();
+			InflaterOutputStream iout = new InflaterOutputStream(out, new Inflater(true));
+			iout.write(b);
+			iout.finish();
+			return new String(out.toByteArray(), StandardCharsets.UTF_8);
+		}
+		catch (IOException ex) {
+			throw new Saml2Exception("Unable to inflate string", ex);
+		}
+	}
+
+	static EncodingConfigurer withDecoded(String decoded) {
+		return new EncodingConfigurer(decoded);
+	}
+
+	static DecodingConfigurer withEncoded(String encoded) {
+		return new DecodingConfigurer(encoded);
+	}
+
+	static final class EncodingConfigurer {
+
+		private final String decoded;
+
+		private boolean deflate;
+
+		private EncodingConfigurer(String decoded) {
+			this.decoded = decoded;
+		}
+
+		EncodingConfigurer deflate(boolean deflate) {
+			this.deflate = deflate;
+			return this;
+		}
+
+		String encode() {
+			byte[] bytes = (this.deflate) ? Saml2Utils.samlDeflate(this.decoded)
+					: this.decoded.getBytes(StandardCharsets.UTF_8);
+			return Saml2Utils.samlEncode(bytes);
+		}
+
+	}
+
+	static final class DecodingConfigurer {
+
+		private static final Base64Checker BASE_64_CHECKER = new Base64Checker();
+
+		private final String encoded;
+
+		private boolean inflate;
+
+		private boolean requireBase64;
+
+		private DecodingConfigurer(String encoded) {
+			this.encoded = encoded;
+		}
+
+		DecodingConfigurer inflate(boolean inflate) {
+			this.inflate = inflate;
+			return this;
+		}
+
+		DecodingConfigurer requireBase64(boolean requireBase64) {
+			this.requireBase64 = requireBase64;
+			return this;
+		}
+
+		String decode() {
+			if (this.requireBase64) {
+				BASE_64_CHECKER.checkAcceptable(this.encoded);
+			}
+			byte[] bytes = Saml2Utils.samlDecode(this.encoded);
+			return (this.inflate) ? Saml2Utils.samlInflate(bytes) : new String(bytes, StandardCharsets.UTF_8);
+		}
+
+		static class Base64Checker {
+
+			private static final int[] values = genValueMapping();
+
+			Base64Checker() {
+
+			}
+
+			private static int[] genValueMapping() {
+				byte[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+					.getBytes(StandardCharsets.ISO_8859_1);
+
+				int[] values = new int[256];
+				Arrays.fill(values, -1);
+				for (int i = 0; i < alphabet.length; i++) {
+					values[alphabet[i] & 0xff] = i;
+				}
+				return values;
+			}
+
+			boolean isAcceptable(String s) {
+				int goodChars = 0;
+				int lastGoodCharVal = -1;
+
+				// count number of characters from Base64 alphabet
+				for (int i = 0; i < s.length(); i++) {
+					int val = values[0xff & s.charAt(i)];
+					if (val != -1) {
+						lastGoodCharVal = val;
+						goodChars++;
+					}
+				}
+
+				// in cases of an incomplete final chunk, ensure the unused bits are zero
+				switch (goodChars % 4) {
+					case 0:
+						return true;
+					case 2:
+						return (lastGoodCharVal & 0b1111) == 0;
+					case 3:
+						return (lastGoodCharVal & 0b11) == 0;
+					default:
+						return false;
+				}
+			}
+
+			void checkAcceptable(String ins) {
+				if (!isAcceptable(ins)) {
+					throw new IllegalArgumentException("Failed to decode SAMLResponse");
+				}
+			}
+
+		}
+
+	}
+
+}

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/provider/service/authentication/logout/OpenSamlOperations.java

@@ -0,0 +1,184 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.saml2.provider.service.authentication.logout;
+
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import javax.xml.namespace.QName;
+
+import org.opensaml.core.xml.XMLObject;
+import org.opensaml.saml.saml2.core.Issuer;
+import org.opensaml.saml.saml2.core.RequestAbstractType;
+import org.opensaml.saml.saml2.core.StatusResponseType;
+import org.opensaml.xmlsec.signature.SignableXMLObject;
+import org.w3c.dom.Element;
+
+import org.springframework.security.saml2.core.Saml2Error;
+import org.springframework.security.saml2.core.Saml2ParameterNames;
+import org.springframework.security.saml2.core.Saml2X509Credential;
+import org.springframework.web.util.UriComponentsBuilder;
+
+interface OpenSamlOperations {
+
+	<T extends XMLObject> T build(QName elementName);
+
+	<T extends XMLObject> T deserialize(String serialized);
+
+	<T extends XMLObject> T deserialize(InputStream serialized);
+
+	SerializationConfigurer<?> serialize(XMLObject object);
+
+	SerializationConfigurer<?> serialize(Element element);
+
+	SignatureConfigurer<?> withSigningKeys(Collection<Saml2X509Credential> credentials);
+
+	VerificationConfigurer withVerificationKeys(Collection<Saml2X509Credential> credentials);
+
+	DecryptionConfigurer withDecryptionKeys(Collection<Saml2X509Credential> credentials);
+
+	interface SerializationConfigurer<B extends SerializationConfigurer<B>> {
+
+		B prettyPrint(boolean pretty);
+
+		String serialize();
+
+	}
+
+	interface SignatureConfigurer<B extends SignatureConfigurer<B>> {
+
+		B algorithms(List<String> algs);
+
+		<O extends SignableXMLObject> O sign(O object);
+
+		Map<String, String> sign(Map<String, String> params);
+
+	}
+
+	interface VerificationConfigurer {
+
+		VerificationConfigurer entityId(String entityId);
+
+		Collection<Saml2Error> verify(SignableXMLObject signable);
+
+		Collection<Saml2Error> verify(RedirectParameters parameters);
+
+		final class RedirectParameters {
+
+			private final String id;
+
+			private final Issuer issuer;
+
+			private final String algorithm;
+
+			private final byte[] signature;
+
+			private final byte[] content;
+
+			RedirectParameters(Map<String, String> parameters, String parametersQuery, RequestAbstractType request) {
+				this.id = request.getID();
+				this.issuer = request.getIssuer();
+				this.algorithm = parameters.get(Saml2ParameterNames.SIG_ALG);
+				if (parameters.get(Saml2ParameterNames.SIGNATURE) != null) {
+					this.signature = org.springframework.security.saml2.internal.Saml2Utils.samlDecode(parameters.get(Saml2ParameterNames.SIGNATURE));
+				}
+				else {
+					this.signature = null;
+				}
+				Map<String, String> queryParams = UriComponentsBuilder.newInstance()
+					.query(parametersQuery)
+					.build(true)
+					.getQueryParams()
+					.toSingleValueMap();
+				String relayState = parameters.get(Saml2ParameterNames.RELAY_STATE);
+				this.content = getContent(Saml2ParameterNames.SAML_REQUEST, relayState, queryParams);
+			}
+
+			RedirectParameters(Map<String, String> parameters, String parametersQuery, StatusResponseType response) {
+				this.id = response.getID();
+				this.issuer = response.getIssuer();
+				this.algorithm = parameters.get(Saml2ParameterNames.SIG_ALG);
+				if (parameters.get(Saml2ParameterNames.SIGNATURE) != null) {
+					this.signature = org.springframework.security.saml2.internal.Saml2Utils.samlDecode(parameters.get(Saml2ParameterNames.SIGNATURE));
+				}
+				else {
+					this.signature = null;
+				}
+				Map<String, String> queryParams = UriComponentsBuilder.newInstance()
+					.query(parametersQuery)
+					.build(true)
+					.getQueryParams()
+					.toSingleValueMap();
+				String relayState = parameters.get(Saml2ParameterNames.RELAY_STATE);
+				this.content = getContent(Saml2ParameterNames.SAML_RESPONSE, relayState, queryParams);
+			}
+
+			static byte[] getContent(String samlObject, String relayState, final Map<String, String> queryParams) {
+				if (Objects.nonNull(relayState)) {
+					return String
+						.format("%s=%s&%s=%s&%s=%s", samlObject, queryParams.get(samlObject),
+								Saml2ParameterNames.RELAY_STATE, queryParams.get(Saml2ParameterNames.RELAY_STATE),
+								Saml2ParameterNames.SIG_ALG, queryParams.get(Saml2ParameterNames.SIG_ALG))
+						.getBytes(StandardCharsets.UTF_8);
+				}
+				else {
+					return String
+						.format("%s=%s&%s=%s", samlObject, queryParams.get(samlObject), Saml2ParameterNames.SIG_ALG,
+								queryParams.get(Saml2ParameterNames.SIG_ALG))
+						.getBytes(StandardCharsets.UTF_8);
+				}
+			}
+
+			String getId() {
+				return this.id;
+			}
+
+			Issuer getIssuer() {
+				return this.issuer;
+			}
+
+			byte[] getContent() {
+				return this.content;
+			}
+
+			String getAlgorithm() {
+				return this.algorithm;
+			}
+
+			byte[] getSignature() {
+				return this.signature;
+			}
+
+			boolean hasSignature() {
+				return this.signature != null;
+			}
+
+		}
+
+	}
+
+	interface DecryptionConfigurer {
+
+		void decrypt(XMLObject object);
+
+	}
+
+}