Authentication Interrupt
CAS has the ability to pause and interrupt the authentication flow to reach out to external services and resources, querying for status and settings that would then dictate how CAS should manage and control the SSO session. Interrupt services are able to present notification messages to the user, provide options for redirects to external services, etc. A common use case deals with presenting a bulletin board during the authentication flow to present messages and announcements to select users and then optionally require the audience to complete a certain task before CAS is able to honor the authentication request and establish a session.
In the interrupt flow, CAS is not at the moment reaching back to an external
resource acting as an interrupt service to store, track or remember a user’s
decision. In other words, we are only dealing with the R
(ie. Read) in CRUD
.
Today’s functionality only deals with inquiring status and reading results
solely in read-only mode. Interrupt services are themselves required and
encouraged to redirect the audience to external resources where execution
of an action resets the interrupt status thereby freeing CAS to proceed
forward later on without having to interrupt the authentication flow again.
Configuration
Support is enabled by including the following dependency in the WAR overlay:
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<dependency>
<groupId>org.apereo.cas</groupId>
<artifactId>cas-server-support-interrupt-webflow</artifactId>
<version>${cas.version}</version>
</dependency>
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implementation "org.apereo.cas:cas-server-support-interrupt-webflow:${project.'cas.version'}"
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dependencyManagement {
imports {
mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
}
}
dependencies {
implementation "org.apereo.cas:cas-server-support-interrupt-webflow"
}
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dependencies {
/*
The following platform references should be included automatically and are listed here for reference only.
implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
*/
implementation "org.apereo.cas:cas-server-support-interrupt-webflow"
}
The following settings and properties are available from the CAS configuration catalog:
cas.interrupt.core.force-execution=false
Whether execution of the interrupt inquiry query should be always forced, and the status of interrupt check should be ignored. This is a global setting that can optionally be overruled for each application policy.
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cas.interrupt.core.trigger-mode=AFTER_AUTHENTICATION
Define how interrupt notifications should be triggered in the authentication flow. Available values are as follows:
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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.
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, specially if defined CAS settings cannot be
recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system
property SKIP_CONFIG_VALIDATION
that should be set to true
. 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.
Tracking Interrupts
The execution of the interrupt inquiry is tracked and remembered as a dedicated CAS cookie and under a specific authentication attribute. The calculation of the inquiry trigger would take into account both options, depending on whether interrupt is set to trigger after authentication or single sign-on.
The following settings and properties are available from the CAS configuration catalog:
cas.interrupt.cookie.allowed-ip-addresses-pattern=
A regular expression pattern that indicates the set of allowed IP addresses, when
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cas.interrupt.cookie.auto-configure-cookie-path=true
Decide if cookie paths should be automatically configured based on the application context path, when the cookie path is not configured.
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cas.interrupt.cookie.comment=CAS Cookie
CAS Cookie comment, describes the cookie's usage and purpose.
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cas.interrupt.cookie.domain=
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.
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cas.interrupt.cookie.http-only=true
true if this cookie contains the HttpOnly attribute. This means that the cookie should not be accessible to scripting engines, like javascript.
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cas.interrupt.cookie.max-age=-1
The maximum age of the cookie, specified in seconds. By default,
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cas.interrupt.cookie.name=
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
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cas.interrupt.cookie.path=
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.
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cas.interrupt.cookie.pin-to-session=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.
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cas.interrupt.cookie.same-site-policy=
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=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:
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cas.interrupt.cookie.secure=true
True if sending this cookie should be restricted to a secure protocol, or false if the it can be sent using any protocol.
|
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.
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, specially if defined CAS settings cannot be
recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system
property SKIP_CONFIG_VALIDATION
that should be set to true
. 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.
Interrupt Payload
Each interrupt strategy is ultimately tasked to produce a response that contains the following settings:
Field | Description |
---|---|
message |
Announcement message to display on the screen. |
links |
A map of links to display on the screen where key is the link text and value is the destination. |
interrupt |
true/false to indicate whether CAS should interrupt the authentication flow. |
block |
true/false to indicate whether CAS should block the authentication flow altogether. |
ssoEnabled |
true/false to indicate whether CAS should permit the authentication but not establish SSO. |
autoRedirect |
true/false to indicate whether CAS should auto-redirect to the first provided link. |
autoRedirectAfterSeconds |
Indicate whether CAS should auto-redirect after the configured number of seconds. The default is -1 , meaning delayed redirect functionality should not be executed. |
Interrupt Trigger Modes
Authentication interrupts and notifications are executed in the overall flow using one of the following strategies. The trigger strategy is defined globally via CAS settings.
After Authentication
This is the default strategy that allows the interrupt query to execute after the primary authentication event and before the single sign-on event. This means an authenticated user has been identified by CAS and by extension is made available to the interrupt, and interrupt has the ability to decide whether a single sign-on session can be established for the user.
No. The collection of links
are just links and are not tied in any way to the
CAS authentication sequence, meaning they do not activate a state, transition or view in
that sequence to trigger CAS into generating tickets, executing certain
actions, etc. Any link in this collection is exactly that; just a link. If a
link points to applications that are integrated with CAS, accessing those
applications via the link will prompt the user for credentials again
specially if single sign-on isn't already established. Remember that
interrupt notifications typically execute after the authentication step
and before any single sign-on session is created.
After Single Sign-on
Alternatively, the interrupt query can execute once the single sign-on session has been established. In this mode, the authenticated user has been identified by CAS and linked to the single sign-on session. Note that interrupt here loses the ability to decide whether a single sign-on session can be established for the user, and interrupt responses indicating this option will have no impact, since the query and interrupt responses happen after the creation of the SSO session.
Yes. In this strategy, links to external applications presented by the interrupt response should be able to take advantage of the established single sign-on session.
Interrupt Strategies
Interrupt queries can be executed via the following ways:
Storage | Description |
---|---|
JSON | See this guide. |
Regex Attribute | See this guide. |
Groovy | See this guide. |
REST | See this guide. |
Custom | See this guide. |
Interrupt Policy Per Service
Application definitions may be assigned a dedicated webflow interrupt policy. A sample JSON file follows:
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{
"@class" : "org.apereo.cas.services.CasRegisteredService",
"serviceId" : "^https://.+",
"name" : "sample service",
"id" : 100,
"webflowInterruptPolicy" : {
"@class" : "org.apereo.cas.services.DefaultRegisteredServiceWebflowInterruptPolicy",
"enabled": true,
"forceExecution": "TRUE"
}
}
The following policy settings are supported:
Field | Description |
---|---|
enabled |
Whether interrupt notifications are enabled for this application. Default is true . |
forceExecution |
Whether execution should proceed anyway regardless whether the flow/user is already interrupted. Accepted values are TRUE , FALSE or UNDEFINED . |
Skipping Interrupts
This option is deprecated and is scheduled to be removed in the future. Consider assigning a dedicated interrupt policy to the application definition instead.
Interrupt notifications may be disabled on a per-service basis. A sample JSON file follows:
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{
"@class" : "org.apereo.cas.services.CasRegisteredService",
"serviceId" : "^https://.+",
"name" : "sample service",
"id" : 100,
"properties" : {
"@class" : "java.util.HashMap",
"skipInterrupt" : {
"@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
"values" : [ "java.util.HashSet", [ "true" ] ]
}
}
}
The following properties are available and recognized by CAS for various modules and features:
Name | Default Value | Type | Group |
---|---|---|---|
skipInterrupt
|
false
|
BOOLEAN
|
INTERRUPTS
|