X.509 Authentication

CAS X.509 authentication components provide a mechanism to authenticate users who present client certificates during the SSL/TLS handshake process. The X.509 components require configuration outside the CAS application since the SSL handshake happens outside the servlet layer where the CAS application resides. There is no particular requirement on deployment architecture (i.e. Apache reverse proxy, load balancer SSL termination) other than any client certificate presented in the SSL handshake be accessible to the servlet container as a request attribute named jakarta.servlet.request.X509Certificate. This happens naturally for configurations that terminate SSL connections directly at the servlet container and when using Apache/mod_jk; for other architectures it may be necessary to do additional work.

CAS can be configured to extract an X509 certificate from a header created by a proxy running in front of CAS.

Overview

Certificates are exchanged as part of the SSL (also called TLS) initialization that occurs when any browser connects to an https website. A certain number of public CA certificates are preinstalled in each browser. It is assumed that:

Your organization is already able to generate and distribute certificates that a user can install in their browser
Somewhere in that certificate there is a field that contains the Principal name or can be easily mapped to the Principal name that CAS can use.

The remaining problem is to make sure that the browsers, servers and Java are all prepared to support these institutional certificates and, ideally, that these institutional certificates will be the only ones exchanged when a browser connects to CAS.

Flow

When a browser connects to CAS over an https: URL, the server identifies itself by sending its own certificate. The browser must already have installed a certificate identifying and trusting the CA that issued the CAS Server certificate. If the browser is not already prepared to trust the CAS server, then an error message pops up saying the server is not trusted.

After the Server sends the certificate that identifies itself, it can then send a list of names of Certificate Authorities from which it is willing to accept certificates. Ideally, this list will include only one name; the name of the internal institutional CA that issues internal intranet-only certificates that internally contain a field with the CAS Principal name.

A user may install any number of certificates into the browser from any number of CA’s. If only one of these certificates comes from a CA named in the list of acceptable CA’s sent by the server, then most browsers will automatically send that one certificate without asking, and some can be configured in to not ask when there is only one possible choice. This presents a user experience where CAS becomes transparent to the user after some initial setup and the login happens automatically. However, if the server hosting CAS sends more than one CA name in the list and that matches more than one certificate on the browser, then the user will get prompted to choose a Certificate from the list. A user interaction defeats much of the purpose of certificates in CAS.

Note that CAS does not control this exchange. It is handled by the underlying server. You may not have the control to require the server to vend only one CA name when a browser visits CAS. So if you want to use X.509 certificates in CAS, you should consider this requirement when choosing the hosting environment. The ideal situation is to select a server that can identify itself with a public certificate issued by something like VeriSign or InCommon but then require the client certificate only be issued by the internal corporate/campus authority.

When CAS gets control, a user certificate may have been presented by the browser and be stored in the request. The CAS X.509 authentication machinery examines that certificate and verifies that it was issued by the trusted institutional authority. Then CAS searches through the fields of the certificate to identify one or more fields that can be turned into the principal identifier that the applications expect.

While an institution can have one certificate authority that issues certificates to employees, clients, machines, services, and devices, it is more common for the institution to have a single “root” certificate authority that in its entire existence only issues a handful of certificates. Each of these certificates identifies a secondary Certificate Authority that issues a particular category of certificates (to students, staff, servers, etc.). It is possible to configure CAS to trust the root Authority and, implicitly, all the secondary authorities that it creates. This, however, makes CAS only as secure as the least reliable secondary Certificate Authority created by the institution. At some point in the future, some manager will buy a product that requires a new class of certificates. He will ask to create a Certificate Authority that vends these certificates to the machines running this new product. He will then turn administration of this mess over to a junior programmer or consultant. If CAS trusts any certificate issued by any Authority created by the root, it will trust a fraudulent certificate forged by someone who has acquired control of what was intended to be a special purpose, isolated CA. Therefore, it is better to configure CAS to only accept certificates from the one secondary CA specifically expected to issue credentials to individuals, instead of trusting the institutional root CA.

Configuration

X.509 support is enabled by including the following dependency in the WAR overlay:

<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-x509-webflow</artifactId>
    <version>${cas.version}</version>
</dependency>

implementation "org.apereo.cas:cas-server-support-x509-webflow:${project.'cas.version'}"

dependencyManagement {
    imports {
        mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
    }
}

dependencies {
    implementation "org.apereo.cas:cas-server-support-x509-webflow"
}

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-x509-webflow"
}

The X.509 handler technically performs additional checks after the real SSL client authentication process performed by the Web server terminating the SSL connection. Since an SSL peer may be configured to accept a wide range of certificates, the CAS X.509 handler provides a number of properties that place additional restrictions on acceptable client certificates.

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

cas.authn.x509.principal-transformation.groovy.locationThe location of the resource.

no default

Required

The location of the resource. Resources can be URLs, or files found either on the classpath or outside somewhere in the file system.

In the event the configured resource is a Groovy script, especially if the script is set to reload on changes, you may need to adjust the total number of inotify instances. On Linux, you may need to add the following line to /etc/sysctl.conf: fs.inotify.max_user_instances = 256.

You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

In situations and scenarios where CAS is able to automatically watch the underlying resource for changes and detect updates and modifications dynamically, you may be able to specify the following setting as either an environment variable or system property with a value of false to disable the resource watcher: org.apereo.cas.util.io.PathWatcherService.

Type: Resource
Default: none
Defined by: GroovyPrincipalTransformationProperties

cas.authn.x509.principal-typeIndicates the type of principal resolution for X509.

SUBJECT_DN

Required

Indicates the type of principal resolution for X509. Available values are as follows:

CN_EDIPI: Create principal by common name and EDIPI.
RFC822_EMAIL: Create principal from the RFC822 type name (aka email address) in the subject alternative name field. The subject alternative name field contains a list of various types of names, one type is RFC822 e-mail address. This will return the first e-mail address that is found (if there are more than one).
SERIAL_NO: Create principal by serial no. Resolve the principal by the serial number with a configurable radix, ranging from 2 to 36. If radix is 16, then the serial number could be filled with leading zeros to even the number of digits.
SERIAL_NO_DN: Create principal by serial no and DN.
SUBJECT: Create principal by subject. Resolve the principal by extracting one or more attribute values from the certificate subject DN and combining them with intervening delimiters.
SUBJECT_ALT_NAME: Create principal by subject alternative name. Resolve the principal by the subject alternative name extension. (type: otherName).
SUBJECT_DN: Create principal by subject DN.

Type: X509Properties.PrincipalTypes
Default: SUBJECT_DN
Defined by: X509Properties

cas.authn.x509.principal.principal-transformation.groovy.locationThe location of the resource.

no default

Required

The location of the resource. Resources can be URLs, or files found either on the classpath or outside somewhere in the file system.

You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

Type: Resource
Default: none
Defined by: GroovyPrincipalTransformationProperties

cas.authn.x509.cache-max-elements-in-memoryWhen CRLs are cached, indicate maximum number of elements kept in memory.

1000

When CRLs are cached, indicate maximum number of elements kept in memory.

Type: Integer
Default: 1000
Defined by: X509Properties

cas.authn.x509.cache-time-to-live-secondsWhen CRLs are cached, indicate the time-to-live of cache items.

PT4H

Duration

When CRLs are cached, indicate the time-to-live of cache items.

Type: String
Default: PT4H
Defined by: X509Properties

cas.authn.x509.check-allWhether revocation checking should check all resources, or stop at first one.

false

Whether revocation checking should check all resources, or stop at first one.

Type: Boolean
Default: false
Defined by: X509Properties

cas.authn.x509.check-key-usageDeployer supplied setting to check the KeyUsage extension.

false

Deployer supplied setting to check the KeyUsage extension.

Type: Boolean
Default: false
Defined by: X509Properties

cas.authn.x509.cn-edipi.alternate-principal-attributeAttribute name that will be used by X509 principal resolvers if the main attribute in the certificate is not present.

no default

Attribute name that will be used by X509 principal resolvers if the main attribute in the certificate is not present. This only applies to principal resolvers that are looking for attributes in the certificate that are not common to all certificates. (e.g. SUBJECT_ALT_NAME, CN_EDIPI)

This assumes you would rather get something like the subjectDn rather than null where null would allow falling through to another authentication mechanism.

Currently supported values are: subjectDn, sigAlgOid, subjectX500Principal.

Type: String
Default: none
Defined by: CnEdipiPrincipalResolverProperties

cas.authn.x509.cn-edipi.extract-edipi-as-attributeWhether to extract EDIPI as an attribute, regardless of principal resolver type.

false

Whether to extract EDIPI as an attribute, regardless of principal resolver type.

Type: Boolean
Default: false
Defined by: CnEdipiPrincipalResolverProperties

cas.authn.x509.crl-expired-policyIf the CRL has expired, activate the this policy.

DENY

If the CRL has expired, activate the this policy. Activated if #revocationChecker is CRL. Accepted values are:

ALLOW: Allow authentication to proceed.
DENY: Deny authentication and block.
THRESHOLD: Applicable to CRL expiration, throttle the request whereby expired data is permitted up to a threshold period of time but not afterward.

Type: String
Default: DENY
Defined by: X509Properties

cas.authn.x509.crl-fetcherOptions to describe how to fetch CRL resources.

RESOURCE

Options to describe how to fetch CRL resources.

To fetch CRLs, the following options are available:

RESOURCE: By default, all revocation checks use fixed resources to fetch the CRL resource from the specified location.
LDAP: A CRL resource may be fetched from a pre-configured attribute, in the event that the CRL resource location is an LDAP URI.

Type: String
Default: RESOURCE
Defined by: X509Properties

cas.authn.x509.crl-resource-expired-policyIf the CRL resource has expired, activate the this policy.

DENY

If the CRL resource has expired, activate the this policy. Activated if #revocationChecker is RESOURCE. Accepted values are:

ALLOW: Allow authentication to proceed.
DENY: Deny authentication and block.
THRESHOLD: Applicable to CRL expiration, throttle the request whereby expired data is permitted up to a threshold period of time but not afterward.

Type: String
Default: DENY
Defined by: X509Properties

cas.authn.x509.crl-resource-unavailable-policyIf the CRL resource is unavailable, activate the this policy.

DENY

If the CRL resource is unavailable, activate the this policy. Activated if #revocationChecker is RESOURCE. Accepted values are:

ALLOW: Allow authentication to proceed.
DENY: Deny authentication and block.
THRESHOLD: Applicable to CRL expiration, throttle the request whereby expired data is permitted up to a threshold period of time but not afterward.

Type: String
Default: DENY
Defined by: X509Properties

cas.authn.x509.crl-resourcesList of CRL resources to use for fetching.

no default

List of CRL resources to use for fetching.

Type: List<String>
Default: none
Defined by: X509Properties

cas.authn.x509.crl-unavailable-policyIf the CRL is unavailable, activate the this policy.

DENY

If the CRL is unavailable, activate the this policy. Activated if #revocationChecker is CRL. Accepted values are:

ALLOW: Allow authentication to proceed.
DENY: Deny authentication and block.
THRESHOLD: Applicable to CRL expiration, throttle the request whereby expired data is permitted up to a threshold period of time but not afterward.

Type: String
Default: DENY
Defined by: X509Properties

cas.authn.x509.extract-certWhether to extract certificate from request.

false

Whether to extract certificate from request. The default implementation extracts certificate from header via Tomcat SSLValve parsing logic and using the #DEFAULT_CERT_HEADER_NAME header. Must be false by default because if someone enables it they need to make sure they are behind proxy that won't let the header arrive directly from the browser.

Type: Boolean
Default: false
Defined by: X509Properties

cas.authn.x509.max-path-lengthDeployer supplied setting for maximum pathLength in a SUPPLIED certificate.

1

Deployer supplied setting for maximum pathLength in a SUPPLIED certificate.

Type: Integer
Default: 1
Defined by: X509Properties

cas.authn.x509.max-path-length-allow-unspecifiedDeployer supplied setting to allow unlimited pathLength in a SUPPLIED certificate.

false

Deployer supplied setting to allow unlimited pathLength in a SUPPLIED certificate.

Type: Boolean
Default: false
Defined by: X509Properties

cas.authn.x509.mixed-modeDetermine whether X509 authentication should allow other forms of authentication such as username/password.

true

Determine whether X509 authentication should allow other forms of authentication such as username/password. If this setting is turned off, typically the ability to view the login form as the primary form of authentication is turned off.

Type: Boolean
Default: true
Defined by: X509Properties

cas.authn.x509.nameThe authentication handler name.

no default

The authentication handler name.

Type: String
Default: none
Defined by: X509Properties

cas.authn.x509.orderThe order of the authentication handler in the chain.

no default

The order of the authentication handler in the chain.

Type: Integer
Default: none
Defined by: X509Properties

cas.authn.x509.principal-descriptorThe principal descriptor used for principal resolution when type is set to PrincipalTypes#SUBJECT .

no default

The principal descriptor used for principal resolution when type is set to PrincipalTypes#SUBJECT.

Type: String
Default: none
Defined by: X509Properties

cas.authn.x509.principal-transformation.blocking-patternA regular expression that will be used against the username to match for blocking/forbidden values.

no default

SpEL

A regular expression that will be used against the username to match for blocking/forbidden values. If a match is found, an exception will be thrown and principal transformation will fail.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal-transformation.case-conversionIndicate whether the principal identifier should be transformed into upper-case, lower-case, etc.

NONE

Indicate whether the principal identifier should be transformed into upper-case, lower-case, etc. Available values are as follows:

NONE: No conversion.
LOWERCASE: Lowercase conversion.
UPPERCASE: Uppercase conversion.

Type: PrincipalTransformationProperties.CaseConversion
Default: NONE
Defined by: PrincipalTransformationProperties

cas.authn.x509.principal-transformation.patternA regular expression that will be used against the provided username for username extractions.

no default

SpEL

A regular expression that will be used against the provided username for username extractions. On a successful match, the first matched group in the pattern will be used as the extracted username.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal-transformation.prefixPrefix to add to the principal id prior to authentication.

no default

SpEL

Prefix to add to the principal id prior to authentication.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal-transformation.suffixSuffix to add to the principal id prior to authentication.

no default

SpEL

Suffix to add to the principal id prior to authentication.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal.active-attribute-repository-idsActivated attribute repository identifiers that should be used for fetching attributes if attribute resolution is enabled.

*

Activated attribute repository identifiers that should be used for fetching attributes if attribute resolution is enabled. The list here may include identifiers separated by comma.

Type: String
Default: *
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.principal.attribute-repository-selectionControl the behavior of the attribute repository selection by authentication method or handler.

no default

Control the behavior of the attribute repository selection by authentication method or handler. The map here is keyed by the authentication handler name, and the value is the attribute repository identifiers separated by comma. When the authentication handler is executed, the attribute repositories assigned to this handler will be selected to fetch attributes. Note that the resolution engine will always favor attribute repositories assigned to the service definition, if any and as part of its authentication policy, over this global setting.

Type: Map<String,String>
Default: none
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.principal.attribute-resolution-enabledWhether attribute repositories should be contacted to fetch person attributes.

undefined

Whether attribute repositories should be contacted to fetch person attributes. Defaults to true if not set. Available values are as follows:

TRUE: Constant to represent the true state.
FALSE: Constant to represent the false state.
UNDEFINED: Constant to represent the undefined state.

Type: TriStateBoolean
Default: undefined
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.principal.principal-attributeAttribute name to use to indicate the identifier of the principal constructed.

no default

Attribute name to use to indicate the identifier of the principal constructed. If the attribute is blank or has no values, the default principal id will be used determined by the underlying authentication engine. The principal id attribute usually is removed from the collection of attributes collected, though this behavior depends on the schematics of the underlying authentication strategy.

Type: String
Default: none
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.principal.principal-resolution-conflict-strategyIn the event that the principal resolution engine resolves more than one principal, (especially if such principals in the chain have different identifiers), this setting determines strategy by which the principal id w...

last

In the event that the principal resolution engine resolves more than one principal, (especially if such principals in the chain have different identifiers), this setting determines strategy by which the principal id would be chosen from the chain. Accepted values are: last, first.

Type: String
Default: last
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.principal.principal-resolution-failure-fatalWhen true, throws an error back indicating that principal resolution has failed and no principal can be found based on the authentication requirements.

undefined

When true, throws an error back indicating that principal resolution has failed and no principal can be found based on the authentication requirements. Otherwise, logs the condition as an error without raising a catastrophic error. Available values are as follows:

TRUE: Constant to represent the true state.
FALSE: Constant to represent the false state.
UNDEFINED: Constant to represent the undefined state.

Type: TriStateBoolean
Default: undefined
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.principal.principal-transformation.blocking-patternA regular expression that will be used against the username to match for blocking/forbidden values.

no default

SpEL

A regular expression that will be used against the username to match for blocking/forbidden values. If a match is found, an exception will be thrown and principal transformation will fail.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal.principal-transformation.case-conversionIndicate whether the principal identifier should be transformed into upper-case, lower-case, etc.

NONE

Indicate whether the principal identifier should be transformed into upper-case, lower-case, etc. Available values are as follows:

NONE: No conversion.
LOWERCASE: Lowercase conversion.
UPPERCASE: Uppercase conversion.

Type: PrincipalTransformationProperties.CaseConversion
Default: NONE
Defined by: PrincipalTransformationProperties

cas.authn.x509.principal.principal-transformation.patternA regular expression that will be used against the provided username for username extractions.

no default

SpEL

A regular expression that will be used against the provided username for username extractions. On a successful match, the first matched group in the pattern will be used as the extracted username.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal.principal-transformation.prefixPrefix to add to the principal id prior to authentication.

no default

SpEL

Prefix to add to the principal id prior to authentication.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal.principal-transformation.suffixSuffix to add to the principal id prior to authentication.

no default

SpEL

Suffix to add to the principal id prior to authentication.

Type: String
Default: none
Defined by: PrincipalTransformationProperties
Supports: Spring Expression Language

cas.authn.x509.principal.return-nullReturn a null principal object if no attributes can be found for the principal.

undefined

Return a null principal object if no attributes can be found for the principal. Available values are as follows:

TRUE: Constant to represent the true state.
FALSE: Constant to represent the false state.
UNDEFINED: Constant to represent the undefined state.

Type: TriStateBoolean
Default: undefined
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.principal.use-existing-principal-idUses an existing principal id that may have already been established in order to run person directory queries.

undefined

Uses an existing principal id that may have already been established in order to run person directory queries. This is generally useful in situations where authentication is delegated to an external identity provider and a principal is first established to then query an attribute source. Available values are as follows:

TRUE: Constant to represent the true state.
FALSE: Constant to represent the false state.
UNDEFINED: Constant to represent the undefined state.

Type: TriStateBoolean
Default: undefined
Defined by: PersonDirectoryPrincipalResolverProperties

cas.authn.x509.refresh-interval-secondsThe refresh interval of the internal scheduler in cases where CRL revocation checking is done via resources.

3600

The refresh interval of the internal scheduler in cases where CRL revocation checking is done via resources.

Type: Integer
Default: 3600
Defined by: X509Properties

cas.authn.x509.reg-ex-subject-dn-patternThe pattern that authorizes an acceptable certificate by its subject dn.

.+

Regex

The pattern that authorizes an acceptable certificate by its subject dn.

Type: String
Default: .+
Defined by: X509Properties

cas.authn.x509.reg-ex-trusted-issuer-dn-patternThe compiled pattern supplied by the deployer.

no default

Regex

The compiled pattern supplied by the deployer.

Type: String
Default: none
Defined by: X509Properties

cas.authn.x509.require-key-usageDeployer supplied setting to force require the correct KeyUsage extension.

false

Deployer supplied setting to force require the correct KeyUsage extension.

Type: Boolean
Default: false
Defined by: X509Properties

cas.authn.x509.revocation-checkerRevocation certificate checking can be carried out in one of the following ways.

NONE

Revocation certificate checking can be carried out in one of the following ways.

NONE: No revocation is performed.
CRL: The CRL URI(s) mentioned in the certificate cRLDistributionPoints extension field. Caches are available to prevent excessive IO against CRL endpoints. CRL data is fetched if does not exist in the cache or if it is expired.
RESOURCE: A CRL hosted at a fixed location. The CRL is fetched at periodic intervals and cached.

Type: String
Default: NONE
Defined by: X509Properties

cas.authn.x509.revocation-policy-thresholdThreshold value if expired CRL revocation policy is to be handled via threshold.

172800

Threshold value if expired CRL revocation policy is to be handled via threshold.

Type: Integer
Default: 172800
Defined by: X509Properties

cas.authn.x509.rfc822-email.alternate-principal-attributeAttribute name that will be used by X509 principal resolvers if the main attribute in the certificate is not present.

no default

This assumes you would rather get something like the subjectDn rather than null where null would allow falling through to another authentication mechanism.

Currently supported values are: subjectDn, sigAlgOid, subjectX500Principal.

Type: String
Default: none
Defined by: Rfc822EmailPrincipalResolverProperties

cas.authn.x509.serial-no-dn.serial-number-prefixThe serial number prefix used for principal resolution when type is set to X509Properties.PrincipalTypes#SERIAL_NO_DN .

SERIALNUMBER=

The serial number prefix used for principal resolution when type is set to X509Properties.PrincipalTypes#SERIAL_NO_DN.

Type: String
Default: SERIALNUMBER=
Defined by: SerialNoDnPrincipalResolverProperties

cas.authn.x509.serial-no-dn.value-delimiterValue delimiter used for principal resolution when type is set to X509Properties.PrincipalTypes#SERIAL_NO_DN .

,

Value delimiter used for principal resolution when type is set to X509Properties.PrincipalTypes#SERIAL_NO_DN.

Type: String
Default: ,
Defined by: SerialNoDnPrincipalResolverProperties

cas.authn.x509.serial-no.principal-hex-s-n-zero-paddingIf radix hex padding should be used when X509Properties#getPrincipalType() is X509Properties.PrincipalTypes#SERIAL_NO .

false

If radix hex padding should be used when X509Properties#getPrincipalType() is X509Properties.PrincipalTypes#SERIAL_NO.

Type: Boolean
Default: false
Defined by: SerialNoPrincipalResolverProperties

cas.authn.x509.serial-no.principal-s-n-radixRadix used when X509Properties#getPrincipalType() is X509Properties.PrincipalTypes#SERIAL_NO .

0

Radix used when X509Properties#getPrincipalType() is X509Properties.PrincipalTypes#SERIAL_NO.

Type: Integer
Default: 0
Defined by: SerialNoPrincipalResolverProperties

cas.authn.x509.ssl-header-nameThe name of the header to consult for an X509 cert (e.g. when behind proxy).

ssl_client_cert

The name of the header to consult for an X509 cert (e.g. when behind proxy).

Type: String
Default: ssl_client_cert
Defined by: X509Properties

cas.authn.x509.subject-alt-name.alternate-principal-attributeAttribute name that will be used by X509 principal resolvers if the main attribute in the certificate is not present.

no default

This assumes you would rather get something like the subjectDn rather than null where null would allow falling through to another authentication mechanism.

Currently supported values are: subjectDn, sigAlgOid, subjectX500Principal.

Type: String
Default: none
Defined by: SubjectAltNamePrincipalResolverProperties

cas.authn.x509.subject-dn.formatFormat of subject DN to use.

DEFAULT

Format of subject DN to use. Available values are as follows:

DEFAULT: Denigrated result of calling certificate.getSubjectDN() method. Javadocs designate this method as "denigrated" for not being portable and/or not being well defined. It is what has been used by CAS for a long time so it remains the default.
RFC1779: RFC 1779 String format of Distinguished Names. Calls X500Principal.getName("RFC1779") which emits a subject DN with the attribute keywords defined in RFC 1779 (CN, L, ST, O, OU, C, STREET). Any other attribute type is emitted as an OID.
RFC2253: RFC 2253 String format of Distinguished Names. Calls X500Principal.getName("RFC2253") which emits a subject DN with the attribute keywords defined in RFC 2253 (CN, L, ST, O, OU, C, STREET, DC, UID). Any other attribute type is emitted as an OID.
CANONICAL: Canonical String format of Distinguished Names. Calls X500Principal.getName("CANONICAL" which emits a subject DN that starts with RFC 2253 and applies additional canonicalization described in the javadoc.

Type: SubjectDnPrincipalResolverProperties.SubjectDnFormat
Default: DEFAULT
Defined by: SubjectDnPrincipalResolverProperties

cas.authn.x509.throw-on-fetch-failureWhen CRL revocation checking is done via distribution points, decide if fetch failures should throw errors.

false

When CRL revocation checking is done via distribution points, decide if fetch failures should throw errors.

Type: Boolean
Default: false
Defined by: X509Properties

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.

Groovy scripting

CAS takes advantage of Apache Groovy in forms of either embedded or external scripts that allow one to, by default, dynamically build constructs, attributes, access strategies and a lot more. To activate the functionality described here, you may need to prepare CAS to support and integrate with Apache Groovy.

Please review this guide to configure your build.

Principal transformation

Authentication handlers that generally deal with username-password credentials can be configured to transform the user id prior to executing the authentication sequence. Each authentication strategy in CAS provides settings to properly transform the principal. Refer to the relevant settings for the authentication strategy at hand to learn more.

Authentication handlers as part of principal transformation may also be provided a path to a Groovy script to transform the provided username. The outline of the script may take on the following form:

String run(final Object... args) {
    def (providedUsername,logger) = args
    return providedUsername.concat("SomethingElse")
}

To prepare CAS to support and integrate with Apache Groovy, please review this guide.

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.

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.