SAML (v4.5)

pac4j allows you to login with any SAML identity provider using the SAML v2.0 protocol.

It has been tested with various SAML 2 providers: Okta, testshib.org, CAS SAML2 IdP, Shibboleth v3.4…

1) Dependency

You need to use the following modules:

This module requires the JDK 11 and is built on OpenSAML >= v4.

<dependency>
    <groupId>org.pac4j</groupId>
    <artifactId>pac4j-saml</artifactId>
    <version>${pac4j.version}</version>
</dependency>

This is the recommended option for most deployments and configurations.

This module requires the JDK 8 and is built on OpenSAML v3.

<dependency>
    <groupId>org.pac4j</groupId>
    <artifactId>pac4j-saml-opensamlv3</artifactId>
    <version>${pac4j.version}</version>
</dependency>

2) Basic configuration

The SAML2Client must be used to login with a SAML 2 identity provider.

First, if you don’t have one, you need to generate a keystore for all signature and encryption operations:

keytool -genkeypair -alias pac4j-demo -keypass pac4j-demo-passwd -keystore samlKeystore.jks -storepass pac4j-demo-passwd -keyalg RSA -keysize 2048 -validity 3650

Alternatively, you can also let pac4j create the keystore for you. If the keystore resource does not exist and is writable, pac4j will attempt to generate a keystore and produce the relevant key pairs inside it.

Then, you must define a SAML2Configuration:

SAML2Configuration cfg = new SAML2Configuration(new ClassPathResource("samlKeystore.jks"),
        "pac4j-demo-passwd",
        "pac4j-demo-passwd",
        new ClassPathResource("testshib-providers.xml"));

The first parameter (keystoreResource) is the keystore defined as a Spring resource using:

the org.springframework.core.io.FileSystemResource class for disk files
the org.springframework.core.io.ClassPathResource class for classpath files
the org.springframework.core.io.UrlResource class for URLs.

The second parameter (keystorePassword) is the value of the -storepass option for the keystore generation while the third parameter (privateKeyPassword) is the value of the -keypass option.

The fourth parameter (identityProviderMetadataResource) should point to your IdP metadata, assuming you can use the same kind of definition than for the keystore.

Or you can also use the “prefix mechanism” to define the Resource:

SAML2Configuration cfg = new SAML2Configuration("resource:samlKeystore.jks",
    "pac4j-demo-passwd",
    "pac4j-demo-passwd",
    "resource:testshib-providers.xml");

These are the available prefixes:

the resource: or the classpath: prefixes creates a ClassPathResource component
the http: or the https: prefixes creates a UrlResource component
the file: prefix or no prefix at all creates a FileSystemResource component.

Or you can even use the empty constructor and the appropriate setters:

the setKeystoreResource, setKeystoreResourceFilepath, setKeystoreResourceClasspath, setKeystoreResourceUrl or setKeystorePath methods to define the keystore
the setKeystorePassword method to define the keystore password
the setPrivateKeyPassword method to set the private password of the keystore
the setIdentityProviderMetadataResource, setIdentityProviderMetadataResourceFilepath, setIdentityProviderMetadataResourceClasspath, setIdentityProviderMetadataResourceUrl or setIdentityProviderMetadataPath methods to define the identity provider metadata.

Finally, you need to declare the SAML2Client based on the previous configuration:

SAML2Client client = new SAML2Client(cfg);

After a successful authentication, a SAML2Profile is returned.

The SAML2Client configures a ReplayCache, which protects against replay attacks. This ReplayCache must keep state between authentications. Therefore a single instance of the SAML2Client must be used. If this is not possible, you can override the initSAMLReplayCache method to create a custom ReplayCacheProvider.

3) Additional configuration:

You can control aspects of the authentication request such as forced and/or passive authentication:

cfg.setForceAuth(true);
cfg.setPassive(true);

You can define the binding type for the authentication request via the setAuthnRequestBindingType method and the binding type for the SP logout request via the setSpLogoutRequestBindingType method:

cfg.setAuthnRequestBindingType(SAMLConstants.SAML2_REDIRECT_BINDING_URI);
// or cfg.setAuthnRequestBindingType(SAMLConstants.SAML2_POST_BINDING_URI);
// or cfg.setAuthnRequestBindingType(SAMLConstants.SAML2_POST_SIMPLE_SIGN_BINDING_URI);

You can define the binding type for the authentication response via the setResponseBindingType method (defaults to POST):

cfg.setResponseBindingType(SAMLConstants.SAML2_POST_BINDING_URI);
// or cfg.setResponseBindingType(SAMLConstants.SAML2_ARTIFACT_BINDING_URI);

Notice that the SP metadata will define the POST binding for the IdP logout request.

Once you have an authenticated web session on the Identity Provider, usually it won’t prompt you again to enter your credentials and it will automatically generate a new assertion for you. By default, the SAML client will accept assertions based on a previous authentication for one hour. If you want to change this behavior, set the maximumAuthenticationLifetime parameter:

// lifetime in seconds
client.setMaximumAuthenticationLifetime(600);

By default, the entity ID of your application (the Service Provider) will be equals to the callback URL. But you can force your own entity ID with the serviceProviderEntityId parameter:

// custom SP entity ID
cfg.setServiceProviderEntityId("http://localhost:8080/callback?extraParameter");

By SAML specification, the authentication request must not contain a NameQualifier, if the SP entity is in the format nameid-format:entity. However, some IdP require that information to be present. You can force a NameQualifier in the request with the useNameQualifier parameter:

// force NameQualifier in the authn request
cfg.setUseNameQualifier(true);

To allow the authentication request sent to the identity provider to specify an attribute consuming index:

cfg.setAttributeConsumingServiceIndex(1);

To allow the authentication request sent to the identity provider to specify an assertion consumer service index:

cfg.setAssertionConsumerServiceIndex(1);

This will also guide pac4j to pick the ACS URL from the metadata indicated by this index.

To configure the supported algorithms and digest methods for the initial authentication request, specify what is supported via the configuration object:

cfg.setBlackListedSignatureSigningAlgorithms(...);
cfg.setSignatureAlgorithms(...);
cfg.setSignatureReferenceDigestMethods(...);
cfg.setSignatureCanonicalizationAlgorithm(...);

The SAML client always requires assertions to be signed either directly or via the response that contains them. When the assertions need to be processed separate of the response, you can request them to be signed directly using:

cfg.setWantsAssertionsSigned(true);

You may also want to enable signing of the authentication requests using:

cfg.setAuthnRequestSigned(true);

The final result will be determined based on the IdP metadata and the configuration above. The IdP metadata will always be chosen in favor of the pac4j configuration, so if you need to purely rely on pac4j, you need to modify the metadata.

You can generate the SP metadata in two ways:

either programmatically using the SAML2Client: String spMetadata = client.getServiceProviderMetadataResolver().getMetadata();
or by defining the appropriate configuration: cfg.setServiceProviderMetadata(new FileSystemResource("/tmp/sp-metadata.xml"));

3.1) Metadata and Keystore configuration:

For service provider metadata generation, pac4j offers the following components:

SAML2FileSystemMetadataGenerator: This is the default option for generating metadata on the file system.
SAML2HttpUrlMetadataGenerator: able to resolve/fetch and store metadata using a REST API that responds to GET/POST methods. This is primarily handled using HTTPMetadataResolver component of OpenSAML. The metadata content is always generated by pac4j and then passed along to the API for storage. The API simply has to retrieve that metadata, or store it. No other extra processing/work is necessary. A GET operation is expected to return the metadata, and a POST operation will provide the metadata in the request body.

For service provider keystore generation, pac4j offers the following components:

SAML2FileSystemKeystoreGenerator: This is the default option for generating keystore on the file system.
SAML2HttpUrlKeystoreGenerator: able to resolve/fetch and store keystore using a REST API that responds to GET/POST methods. The metadata content is always generated by pac4j and then passed along to the API for storage as a base64 encoded string. The API simply has to retrieve that keystore, or store it. While fectching pac4j will decode it keystore back, construct it again and will proceed. A GET operation is expected to return the keystore, and a POST operation will provide the keystore in the request body.

Please note that:

In practice, it’s likely that SAML2HttpUrlMetadataGenerator would be used with SAML2HttpUrlKeystoreGenerator. However, given the flexibility that exists with separation of components, this is not strictly necessary.
Contacting URL endpoints is done using SAML2HttpClientBuilder that builds on of OpenSAML v4 with minor adjustments. The builder can support basic-auth, and other forms of security for endpoint access.

SAML2HttpClientBuilder httpClient = new SAML2HttpClientBuilder();
httpClient.setConnectionTimeout(Duration.ofSeconds(1));
httpClient.setSocketTimeout(Duration.ofSeconds(1));

final SAML2Configuration config = new SAML2Configuration();
config.setHttpClient(httpClient.build());
config.setKeystoreResourceUrl("http://localhost:8081/keystore");
config.setServiceProviderMetadataResource(
    new FileUrlResource(new URL("http://localhost:8081/saml")));

// Other Stuff...

config.init();
return config;

3.2) Identity provider metadata resolution:

Resolution of identity provider metadata can also be controlled and overridden as shown below:

final SAML2MetadataResolver resolver = new CustomIdentityProviderSAML2MetadataResolver();
final SAML2Configuration config = new SAML2Configuration();
config.setIdentityProviderMetadataResolver(resolver);

4) Logout

The SAML support handles the HTTP-POST and the HTTP-Redirect bindings for logout requests/responses (and the SOAP binding for incoming logout requests).

The SAML2Client can participate in the central logout and send a logout request to the IdP. The binding of this request is controlled by the spLogoutRequestBindingType property and the request can be signed using the spLogoutRequestSigned property of the SAML2Configuration.

When calling the IdP, the SAML pac4j application locally removes the user profiles and optionally destroys the web session based on the DefaultLogoutHandler. You may use your own logout handler by implementing the LogoutHandler interface and define it in the SAML configuration. By default at the last step of SP initiated logout user will see a blank page. It is possible to customize default pac4j behavior using the postLogoutURL property of the SAML2Configuration.

When called by the IdP, the SAML pac4j application also removes the user profiles based on the logout handler and returns a logout response with a binding defined by the spLogoutResponseBindingType property (in the SAML2Configuration).

5) Authentication Attributes

The following authentication attributes are populated by this client:

The entityID of the IdP (getAuthenticationAttribute("issuerId") or SAML2Profile.getIssuerId())
The authentication method(s) asserted by the IdP (getAuthenticationAttribute("authnContext") or SAML2Profile.getAuthnContexts())
The NotBefore SAML Condition (getAuthenticationAttribute("notBefore") or SAML2Profile.getNotBefore())
The NotOnOrAfter SAML Condition (getAuthenticationAttribute("notOnOrAfter") or SAML2Profile.getNotOnOrAfter())
the session index.

6) ADFS subtleties

You must follow these rules to successfully authenticate using Microsoft ADFS 2.0/3.0.

a) Maximum authentication time

pac4j has the default maximum time set to 1 hour while ADFS has it set to 8 hours. Therefore it can happen that ADFS sends an assertion which is still valid on ADFS side but evaluated as invalid on the pac4j side.

You can see the following error message: org.pac4j.saml.exceptions.SAMLException: Authentication issue instant is too old or in the future

There are two possibilities how to make the values equal:

change the value in ADFS management console in the trust properties dialog
change the value on pac4j side using the setMaximumAuthenticationLifetime method.

b) Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files

You must install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files into your JRE/JDK running pac4j. If you don’t do it, you may encounter errors like this:

ERROR [org.opensaml.xml.encryption.Decrypter] - <Error decrypting the encrypted data element>
org.apache.xml.security.encryption.XMLEncryptionException: Illegal key size
ERROR [org.opensaml.xml.encryption.Decrypter] - <Failed to decrypt EncryptedData using either EncryptedData KeyInfoCredentialResolver or EncryptedKeyResolver + EncryptedKey KeyInfoCredentialResolver>
ERROR [org.opensaml.saml2.encryption.Decrypter] - <SAML Decrypter encountered an error decrypting element content>

Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files can be downloaded from Oracle’s Java Download site.

c) Disable Name Qualifier for format urn:oasis:names:tc:SAML:2.0:nameid-format:entity

ADFS 3.0 does not accept NameQualifier when using urn:oasis:names:tc:SAML:2.0:nameid-format:entity. For this reason, the parameter useNameQualifier in the SAML2Configuration must be set to false, which is the default value.

Integration with various IdPs

SimpleSAMPphp

SimpleSAMLphp is a commonly used IdP. To integrate PAC4J with SimpleSAMLphp use the following steps as a start. Let’s assume a standard simpleSAMLphp install.

DemoConfigFactory.java

final SAML2Configuration cfg = new SAML2Configuration("resource:samlKeystore.jks",
 "pac4j-demo-passwd",
 "pac4j-demo-passwd",
 "resource:idp-metadata.xml"); //the id-metadata.xml contains IdP metadata, you will have to create this
 cfg.setMaximumAuthenticationLifetime(3600);
 cfg.setServiceProviderEntityId("test.pac4j"); //the entityId of you client (the SP), you will usualy change this
 cfg.setServiceProviderMetadataPath(new File("sp-metadata.xml").getAbsolutePath()); //the metadata of the SP, no changes required usually
 final SAML2Client saml2Client = new SAML2Client(cfg);

SimpleSAMLphp config

Please note that pac4j requires the binding urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST for both SingleSignOn and SingleLogout services while simpleSAMLphp is by default installed using only urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect. It is required to add the bindings to the metadata/saml20-idp-hosted.php file:

'SingleSignOnServiceBinding' => array('urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect', 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST'),
'SingleLogoutServiceBinding' => array('urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect', 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST'),

It is also required to register the EntityID of your SP into the file metadata/saml20-sp-remote.php

$metadata['test.pac4j'] = array(
 'AssertionConsumerService' => 'http://localhost:8080/callback?client_name=SAML2Client',
...

Metadata

SimpleSAMLphp exposes his IdP metadata on http://idp-domain/simplesamlphp/saml2/idp/metadata.php?output=xhtml. You can wrap this file in an additional <md:EntitiesDescriptor ... tag to generate the idp-metadata.xml file.

 <?xml version="1.0"?>
<md:EntitiesDescriptor xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata" xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    <md:EntityDescriptor entityID="http://idp-domain/simplesamlphp/saml2/idp/metadata.php">
      <md:IDPSSODescriptor protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
        <md:KeyDescriptor use="signing">
          <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
            <ds:X509Data>
              <ds:X509Certificate>MII...</ds:X509Certificate>
            </ds:X509Data>
          </ds:KeyInfo>
        </md:KeyDescriptor>
        <md:KeyDescriptor use="encryption">
          <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
            <ds:X509Data>
              <ds:X509Certificate>MII...</ds:X509Certificate>
            </ds:X509Data>
          </ds:KeyInfo>
        </md:KeyDescriptor>
        <md:SingleLogoutService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" Location="http://idp-domain/simplesamlphp/saml2/idp/SingleLogoutService.php"/>
        <md:SingleLogoutService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" Location="http://idp-domain/simplesamlphp/saml2/idp/SingleLogoutService.php"/>
        <md:NameIDFormat>urn:oasis:names:tc:SAML:2.0:nameid-format:transient</md:NameIDFormat>
        <md:SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" Location="http://idp-domain/simplesamlphp/saml2/idp/SSOService.php"/>
        <md:SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" Location="http://idp-domain/simplesamlphp/saml2/idp/SSOService.php"/>
      </md:IDPSSODescriptor>
    </md:EntityDescriptor>
</md:EntitiesDescriptor>

7) Custom OpenSAML Bootstrap

Behind the scenes, OpenSAML uses a singleton registry to hold its configuration (builders, marshallers, parsers, etc). While pac4j ships with generally sane defaults for this configuration (see org.pac4j.saml.util.Configuration$DefaultConfigurationManager), it might be useful for a developer to override this configuration.

Pac4j uses a Java service provider to find a configuration class and bootstrap the OpenSAML libraries. It will load all implementations of org.pac4j.saml.util.Configuration it can find on the classpath and use the one with the javax.annotation.Priority value.

To use a custom configuration, one must add a jar with the following to the classpath:

Implementation of org.pac4j.saml.util.Configuration. This implementation should have a javax.annotation.Priority annotation denoting the priority. The lowest value is the one that will ultimately be used configuration. The default implementation has and effective priority of 100. Generic providers likely should use something like 50, while end user implementors should use 1. for example:

  @Priority(100)
  public static class DefaultConfigurationManager implements ConfigurationManager {
      @Override
      public void configure() {
          XMLObjectProviderRegistry registry;
          synchronized (ConfigurationService.class) {
              registry = ConfigurationService.get(XMLObjectProviderRegistry.class);
              if (registry == null) {
                  registry = new XMLObjectProviderRegistry();
                  ConfigurationService.register(XMLObjectProviderRegistry.class, registry);
              }
          }

          try {
              InitializationService.initialize();
          } catch (final InitializationException e) {
              throw new RuntimeException("Exception initializing OpenSAML", e);
          }

          ParserPool parserPool = initParserPool();
          registry.setParserPool(parserPool);
      }

      private static ParserPool initParserPool() {

          try {
              BasicParserPool parserPool = new BasicParserPool();
              parserPool.setMaxPoolSize(100);
              parserPool.setCoalescing(true);
              parserPool.setIgnoreComments(true);
              parserPool.setNamespaceAware(true);
              parserPool.setExpandEntityReferences(false);
              parserPool.setXincludeAware(false);
              parserPool.setIgnoreElementContentWhitespace(true);

              final Map<String, Object> builderAttributes = new HashMap<String, Object>();
              parserPool.setBuilderAttributes(builderAttributes);

              final Map<String, Boolean> features = new HashMap<>();
              features.put("http://apache.org/xml/features/disallow-doctype-decl", Boolean.TRUE);
              features.put("http://apache.org/xml/features/validation/schema/normalized-value", Boolean.FALSE);
              features.put("http://javax.xml.XMLConstants/feature/secure-processing", Boolean.TRUE);
              features.put("http://xml.org/sax/features/external-general-entities", Boolean.FALSE);
              features.put("http://xml.org/sax/features/external-parameter-entities", Boolean.FALSE);

              parserPool.setBuilderFeatures(features);
              parserPool.initialize();
              return parserPool;
          } catch (final ComponentInitializationException e) {
              throw new RuntimeException("Exception initializing parserPool", e);
          }
      }
  }

/META-INF/services/org.pac4j.saml.util.ConfigurationManager file. This file should have the fully qualified classname of the org.pac4j.saml.util.Configuration implementation

For more information, see [https://docs.oracle.com/javase/tutorial/ext/basics/spi.html]