SAML2 Authentication

CAS can act as a SAML2 identity provider accepting authentication requests and producing SAML assertions.

If you intend to allow CAS to delegate authentication to an external SAML2 identity provider, you need to review this guide.

:information_source: SAML Specification

This document solely focuses on what one might do to turn on SAML2 support inside CAS. It is not to describe/explain the numerous characteristics of the SAML2 protocol itself.

Federation Interop Evaluation

The CAS project strives to conform to the SAML V2.0 Implementation Profile for Federation Interoperability. An evaluation of the requirements against the current CAS release is available here. It is recommended that you view, evaluate and comment on functionality that is currently either absent or marked questionable where verification is needed.

SAML Endpoints

The following CAS endpoints respond to supported SAML2 profiles:

  • /idp/error
  • /idp/profile/SAML2/Redirect/SSO
  • /idp/profile/SAML2/POST/SSO
  • /idp/profile/SAML2/POST-SimpleSign/SSO
  • /idp/profile/SAML2/Unsolicited/SSO
  • /idp/profile/SAML2/SOAP/ECP
  • /idp/profile/SAML2/SOAP/AttributeQuery
  • /idp/profile/SAML1/SOAP/ArtifactResolution

Metadata Management

Handling and storing SAML2 identity provider or service provider metadata can be done in a few ways. To learn more, please review this guide.

Configuration

Support is enabled by including the following dependency in the WAR overlay:

1
2
3
4
5
<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-saml-idp</artifactId>
    <version>${cas.version}</version>
</dependency>
1
implementation "org.apereo.cas:cas-server-support-saml-idp:${project.'cas.version'}"
1
2
3
4
5
6
7
8
9
dependencyManagement {
    imports {
        mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
    }
}

dependencies {
    implementation "org.apereo.cas:cas-server-support-saml-idp"
}
1
2
3
4
5
6
7
8
9
10
dependencies {
    /*
        The following platform references are included automatically and are listed for reference only.

        implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
        implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
        
    */
    implementation "org.apereo.cas:cas-server-support-saml-idp"
}

You may also need to declare the following repository in your CAS overlay to be able to resolve dependencies:

1
2
3
4
5
6
repositories {
    maven { 
        mavenContent { releasesOnly() }
        url "https://build.shibboleth.net/maven/releases/" 
    }
}

The following settings and properties are available from the CAS configuration catalog:

cas.authn.saml-idp.core.entity-idThe SAML entity id for the deployment.
https://cas.example.org/idp
RequiredSpEL

The SAML entity id for the deployment.

Type
String
Default
https://cas.example.org/idp
Defined by
SamlIdPCoreProperties
Supports
Spring Expression Language
cas.authn.saml-idp.core.session-replication.cookie.crypto.encryption.keyThe encryption key is a string whose length is defined by the encryption key size setting.
no default
RequiredSpEL

The encryption key is a string whose length is defined by the encryption key size setting.

Type
String
Default
none
Defined by
EncryptionJwtCryptoProperties
Supports
Spring Expression Language
cas.authn.saml-idp.core.session-replication.cookie.crypto.signing.keyThe signing key is a string whose length is defined by the signing key size setting.
no default
RequiredSpEL

The signing key is a string whose length is defined by the signing key size setting.

Type
String
Default
none
Defined by
SigningJwtCryptoProperties
Supports
Spring Expression Language
cas.authn.saml-idp.core.attribute-friendly-namesA mapping of attribute names to their friendly names, defined globally.
no default

A mapping of attribute names to their friendly names, defined globally. Example might be urn:oid:1.3.6.1.4.1.5923.1.1.1.6->eduPersonPrincipalName.

Type
List<String>
Default
none
Defined by
SamlIdPCoreProperties
cas.authn.saml-idp.core.attribute-query-profile-enabledIndicates whether attribute query profile is enabled.
false

Indicates whether attribute query profile is enabled. Enabling this setting would allow CAS to record SAML responses and have them be made available later for attribute lookups.

Type
Boolean
Default
false
Defined by
SamlIdPCoreProperties
cas.authn.saml-idp.core.context.authentication-context-class-mappingsA mapping of authentication context class refs.
no default

A mapping of authentication context class refs. This is where specific authentication context classes are referenced and mapped to providers that CAS may support mainly for, i.e. MFA purposes.

Example might be urn:oasis:names:tc:SAML:2.0:ac:classes:SomeClassName->mfa-duo.

In delegated authentication scenarios, this can also be a mapping of authentication context class refs, when CAS is proxying/delegating authentication to an external SAML2 identity provider. The requested authentication context as submitted by the service provider is first received by CAS, and then gets mapped to a context class that is passed onto the external identity provider. For example, you might have a scenario where a SAML2 service provider would submit https://refeds.org/profile/mfa to CAS, and CAS would translate that to http://schemas.microsoft.com/claims/multipleauthn to ultimate route the authentication request to Azure. If no mapping is found, the original context is passed as is.

Example might be https://refeds.org/profile/mfa->http://schemas.microsoft.com/claims/multipleauthn.

Type
List<String>
Default
none
Defined by
SamlIdPAuthenticationContextProperties
cas.authn.saml-idp.core.context.default-authentication-context-classThe default authentication context class to include in the response if none is specified via the service.
urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport

The default authentication context class to include in the response if none is specified via the service.

Type
String
Default
urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport
Defined by
SamlIdPAuthenticationContextProperties
cas.authn.saml-idp.core.session-replication.cookie.allowed-ip-addresses-patternA regular expression pattern that indicates the set of allowed IP addresses, when #isPinToSession() is configured.
no default
Regex

A regular expression pattern that indicates the set of allowed IP addresses, when #isPinToSession() is configured. In the event that there is a mismatch between the cookie IP address and the current request-provided IP address (i.e. network switches, VPN, etc), the cookie can still be considered valid if the new IP address matches the pattern specified here.

Type
String
Default
none
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.auto-configure-cookie-pathDecide if cookie paths should be automatically configured based on the application context path, when the cookie path is not configured.
true

Decide if cookie paths should be automatically configured based on the application context path, when the cookie path is not configured. @deprecated since 7.3.0

Type
Boolean
Default
true
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.crypto.algThe signing/encryption algorithm to use.
no default

The signing/encryption algorithm to use.

Type
String
Default
none
Defined by
EncryptionJwtSigningJwtCryptographyProperties
cas.authn.saml-idp.core.session-replication.cookie.crypto.enabledWhether crypto operations are enabled.
true

Whether crypto operations are enabled.

Type
Boolean
Default
true
Defined by
EncryptionJwtSigningJwtCryptographyProperties
cas.authn.saml-idp.core.session-replication.cookie.crypto.encryption.key-sizeThe encryption key size.
512

The encryption key size.

Type
Integer
Default
512
Defined by
EncryptionJwtCryptoProperties
cas.authn.saml-idp.core.session-replication.cookie.crypto.signing.key-sizeThe signing key size.
512

The signing key size.

Type
Integer
Default
512
Defined by
SigningJwtCryptoProperties
cas.authn.saml-idp.core.session-replication.cookie.crypto.strategy-typeControl the cipher sequence of operations.
ENCRYPT_AND_SIGN
Control the cipher sequence of operations. The accepted values are:
  • ENCRYPT_AND_SIGN: Encrypt the value first, and then sign.
  • SIGN_AND_ENCRYPT: Sign the value first, and then encrypt.
Type
String
Default
ENCRYPT_AND_SIGN
Defined by
EncryptionJwtSigningJwtCryptographyProperties
cas.authn.saml-idp.core.session-replication.cookie.domainCookie domain.
no default

Cookie domain. Specifies the domain within which this cookie should be presented. The form of the domain name is specified by RFC 2965. A domain name begins with a dot (.foo.com) and means that the cookie is visible to servers in a specified Domain Name System (DNS) zone (for example, www.foo.com, but not a.b.foo.com). By default, cookies are only returned to the server that sent them.

Type
String
Default
none
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.geo-locate-client-sessionWhen set to true and assuming #isPinToSession() is also true , client sessions (using the client IP address) are geo-located using a geolocation service when/if configured.
false

When set to true and assuming #isPinToSession() is also true, client sessions (using the client IP address) are geo-located using a geolocation service when/if configured. The resulting session is either pinned to the client geolocation, or the default client address.

Type
Boolean
Default
false
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.http-onlytrue if this cookie contains the HttpOnly attribute.
true

true if this cookie contains the HttpOnly attribute. This means that the cookie should not be accessible to scripting engines, like javascript.

Type
Boolean
Default
true
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.max-ageThe maximum age of the cookie, specified in seconds.
-1
Duration

The maximum age of the cookie, specified in seconds. By default, -1 indicating the cookie will persist until browser shutdown. A positive value indicates that the cookie will expire after that many seconds have passed. Note that the value is the maximum age when the cookie will expire, not the cookie's current age. A negative value means that the cookie is not stored persistently and will be deleted when the Web browser exits. A zero value causes the cookie to be deleted.

Type
String
Default
-1
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.nameCookie name.
no default

Cookie name. Constructs a cookie with a specified name and value. The name must conform to RFC 2965. That means it can contain only ASCII alphanumeric characters and cannot contain commas, semicolons, or white space or begin with a $ character. The cookie's name cannot be changed after creation. By default, cookies are created according to the RFC 2965 cookie specification. Cookie names are automatically calculated assigned by CAS at runtime, and there is usually no need to customize the name or assign it a different value unless a special use case warrants the change.

Type
String
Default
none
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.pathCookie path.
no default

Cookie path. Specifies a path for the cookie to which the client should return the cookie. The cookie is visible to all the pages in the directory you specify, and all the pages in that directory's subdirectories. A cookie's path must include the servlet that set the cookie, for example, /catalog, which makes the cookie visible to all directories on the server under /catalog. Consult RFC 2965 (available on the Internet) for more information on setting path names for cookies.

Type
String
Default
none
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.pin-to-sessionWhen generating cookie values, determine whether the value should be compounded and signed with the properties of the current session, such as IP address, user-agent, etc.
true

When generating cookie values, determine whether the value should be compounded and signed with the properties of the current session, such as IP address, user-agent, etc.

Turning off session pinning is not exactly ideal. This is a barrier to prevent cookie replay attacks. A cookie that was created with an IP given a certain location cannot be replayed back in a different browser with a different IP from a different location.

There may however be legitimate reasons to turn it off and relax this after careful reviews, if you intend to support a type of user who intends to switch their IP quite frequently. A classic example is the type of user that is on VPN at the time of login, but decides to resume their work a few hours later off VPN or at a different location.

Type
Boolean
Default
true
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.same-site-policyIf a cookie is only intended to be accessed in a first party context, the developer has the option to apply one of settings SameSite=Lax or SameSite=Strict or SameSite=None to prevent external access.
no default

If a cookie is only intended to be accessed in a first party context, the developer has the option to apply one of settings SameSite=Lax or SameSite=Strict or SameSite=None to prevent external access.

To safeguard more websites and their users, the new secure-by-default model assumes all cookies should be protected from external access unless otherwise specified. Developers must use a new cookie setting, SameSite=None, to designate cookies for cross-site access. When the SameSite=None attribute is present, an additional Secure attribute is used so cross-site cookies can only be accessed over HTTPS connections.

Accepted values are:
  • Lax
  • Strict
  • None
  • Off: Disable the generation of the SameSite cookie attribute altogether.
  • Path to a Groovy script that is able to generate the SameSite cookie attribute dynamically.
  • Fully qualified name of a class that implements org.apereo.cas.web.cookie.CookieSameSitePolicy
Type
String
Default
none
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.cookie.secureTrue if sending this cookie should be restricted to a secure protocol, or false if the it can be sent using any protocol.
true

True if sending this cookie should be restricted to a secure protocol, or false if the it can be sent using any protocol.

Type
Boolean
Default
true
Defined by
CookieSessionReplicationProperties
cas.authn.saml-idp.core.session-replication.replicate-sessionsIndicates whether profiles and other session data, collected as part of authentication flows and protocol requests that are kept by the container session, should be replicated across the cluster using CAS and its own...
false

Indicates whether profiles and other session data, collected as part of authentication flows and protocol requests that are kept by the container session, should be replicated across the cluster using CAS and its own ticket registry. Without this option, profile data and other related pieces of information should be manually replicated via means and libraries outside of CAS. @deprecated since 7.3.0

Type
Boolean
Default
false
Defined by
SessionReplicationProperties
cas.authn.saml-idp.core.session-storage-typeIndicates whether saml requests, and other session data, collected as part of SAML flows and requests that are kept by the container http session, local storage, or should be replicated across the cluster.
http
Indicates whether saml requests, and other session data, collected as part of SAML flows and requests that are kept by the container http session, local storage, or should be replicated across the cluster. Available values are as follows:
  • HTTP: Authentication requests, and other session data collected as part of authentication protocol flows and requests are kept in the http servlet session that is local to the server.
  • BROWSER_STORAGE: Authentication requests, and other session data collected as part of authentication protocol flows and requests are kept in the client browser's session storage, signed and encrypted. All interactions require client-side read/write operations to restore the session from the browser. Browsers that cannot use local or session storage keep the same payload in cookies instead.
  • TICKET_REGISTRY: Authentication requests, and other session data collected as part of authentication protocol flows and requests are tracked as CAS tickets in the registry and replicated across the entire cluster as tickets. This state is tied to the user's agent/browser using a special cookie that would be used to locate and restore that state. The cookie content may be signed and encrypted.
Type
SessionStorageTypes
Default
http
Defined by
SamlIdPCoreProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Signing & encryption

This CAS feature is able to accept signing and encryption crypto keys. In most scenarios if keys are not provided, CAS will auto-generate them. The following instructions apply if you wish to manually and beforehand create the signing and encryption keys.

Note that if you are asked to create a JWK of a certain size for the key, you are to use the following set of commands to generate the token:

1
2
wget https://raw.githubusercontent.com/apereo/cas/master/etc/jwk-gen.jar
java -jar jwk-gen.jar -t oct -s [size]

The outcome would be similar to:

1
2
3
4
5
{
  "kty": "oct",
  "kid": "...",
  "k": "..."
}

The generated value for k needs to be assigned to the relevant CAS settings. Note that keys generated via the above algorithm are processed by CAS using the Advanced Encryption Standard (AES) algorithm which is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology.


Notes on configuration

Configuration Metadata

The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

Be Selective

This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

YAGNI

Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc.

:information_source: Note

When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value. The only possible exception to this rule is when naming actuator endpoints; The name of the actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.

Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

Validation

Configuration properties are automatically validated on CAS startup to report issues with configuration binding, especially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

Actuator Endpoints

The following endpoints are provided by CAS:

samlPostProfileResponse
CAS endpoint2 operationsNot exposed by default
1

Turn the endpoint on and expose it over the web. One entry covers every operation. By default only info, health and status are exposed.

1
2
management.endpoint.samlPostProfileResponse.access=UNRESTRICTED
management.endpoints.web.exposure.include=samlPostProfileResponse

Endpoints may be mapped to other paths. For example, to serve health at healthcheck:

1
management.endpoints.web.path-mapping.health=healthcheck

SAML Services

Please see this guide to learn more about how to configure SAML2 service providers.

Security Configuration

Please see this guide to learn more about how to configure SAML2 security configuration.

Logout & SLO

Please see this guide to learn more about how to configure SAML2 logout operations and settings.

Attribute Release

Attribute filtering and release policies are defined per SAML service. See this guide for more info.

Name ID Selection

Please see this guide to learn more about how to configure SAML2 security configuration.

Unsolicited SSO

Please see this guide for more details.

Attribute Queries

Please see this guide for more details.

Client Libraries

For Java-based applications, the following frameworks may be used to integrate your application with CAS acting as a SAML2 identity provider:

Troubleshooting

To enable additional logging, modify the logging configuration file to add the following:

1
2
3
4
5
6
7
8
<Logger name="org.opensaml" level="debug" additivity="false">
    <AppenderRef ref="casConsole"/>
    <AppenderRef ref="casFile"/>
</Logger>
<Logger name="PROTOCOL_MESSAGE" level="debug" additivity="false">
    <AppenderRef ref="casConsole"/>
    <AppenderRef ref="casFile"/>
</Logger>