WORKERS AHEAD!
You are viewing the development documentation for the Apereo CAS server. The functionality presented here is not officially released yet. This is a work in progress and will be continually updated as development moves forward. You are most encouraged to test the changes presented.
Surrogate Authentication
Surrogate authentication (impersonation), sometimes known as sudo for the web, is the ability to authenticate on behalf of another user.
The two actors in this case are:
- The primary admin user whose credentials are verified upon authentication.
- The surrogate user, selected by the admin, to which CAS will switch after credential verification and is one that is linked to the single sign-on session.
Example use cases for impersonation include:
- Logging into an application on behalf of a user to execute and make changes.
- Troubleshoot a bothersome authentication experience with an application on behalf of another user.
Surrogate authentication is enabled by including the following dependencies in the WAR overlay:
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<dependency>
<groupId>org.apereo.cas</groupId>
<artifactId>cas-server-support-surrogate-webflow</artifactId>
<version>${cas.version}</version>
</dependency>
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implementation "org.apereo.cas:cas-server-support-surrogate-webflow:${project.'cas.version'}"
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dependencyManagement {
imports {
mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
}
}
dependencies {
implementation "org.apereo.cas:cas-server-support-surrogate-webflow"
}
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dependencies {
/*
The following platform references should be included automatically and are listed here for reference only.
implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
*/
implementation "org.apereo.cas:cas-server-support-surrogate-webflow"
}
The following settings and properties are available from the CAS configuration catalog:
cas.authn.surrogate.separator=+
The separator character used to distinguish between the surrogate account and the admin account.
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cas.authn.surrogate.tgt.time-to-kill-in-seconds=1800
Timeout in seconds to kill the surrogate session and consider tickets expired.
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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.
Account Storage
The following account stores may be configured and used to locate surrogates authorized for a particular user.
Static
Surrogate accounts may be defined statically in the CAS configuration.
The following settings and properties are available from the CAS configuration catalog:
cas.authn.surrogate.simple.surrogates=
Define the list of accounts that are allowed to impersonate. This is done in a key-value structure where the key is the admin user and the value is a comma-separated list of identifiers that can be impersonated by the admin-user.
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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.
Others
Storage | Description |
---|---|
JSON | See this guide. |
LDAP | See this guide. |
JDBC | See this guide. |
REST | See this guide. |
Groovy | See this guide. |
Custom | See this guide. |
Account Selection
Please see this guide.
Session Expiration
An impersonation session can be assigned a specific expiration policy that would control how long a surrogate session may last. This means that the SSO session established as part of impersonation will rightly vanish, once the expiration policy dictates as such. It is recommended that you keep the expiration length short (i.e. 30 minutes) to avoid possible security issues.

The expiration policy assigned to impersonation sessions is expected to be shorter than the normal expiration policy assigned to non-surrogate sessions. In other words, if the usual expiration policy that controls the single sign-on session is set to last 2 hours, the surrogate session expiration is expected to be a time period less than or equal to 2 hours.
Surrogate Attributes
Upon a successful surrogate authentication event, the following attributes are communicated back to the application in order to detect an impersonation session:
Attribute | Instructions |
---|---|
surrogateEnabled |
Boolean to indicate whether session is impersonated. |
surrogatePrincipal |
The admin user whose credentials are validated and acts as the impersonator. |
surrogateUser |
The surrogate user that is impersonated. |
Surrogate Access Strategy
Please see this guide.
Surrogate Audits
Surrogate authentication events are by default tracked in the audit logs:
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=============================================================
WHO: (Primary User: [casuser], Surrogate User: [testuser])
WHAT: ST-1-u_R_SyXJJlENS0fBLwpecNE for https://example.app.edu
ACTION: SERVICE_TICKET_CREATED
APPLICATION: CAS
WHEN: Mon Sep 11 12:55:07 MST 2017
CLIENT IP ADDRESS: 127.0.0.1
SERVER IP ADDRESS: 127.0.0.1
=============================================================
Additionally, failure and success events may also communicated via SMS and/or email messages to relevant parties.
The following settings and properties are available from the CAS configuration catalog:
cas.authn.surrogate.mail.attribute-name=
Principal attribute names that indicates the destination email address for this message. The attributes must already be resolved and available to the CAS principal. When multiple attributes are specified, each attribute is then examined against the available CAS principal to locate the email address value, which may result in multiple emails being sent. This setting supports the Spring Expression Language.
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cas.authn.surrogate.mail.from=
Email from address.
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cas.authn.surrogate.mail.subject=
Email subject line. The subject can either be defined verbaitm, or it may point to a message key in the language bundle using the syntax#{subject-language-key} . This key should point to a valid message defined in the appropriate language bundle that is then picked up via the active locale. In case where the language code cannot resolve the real subject, a default subject value would be used.
This setting supports the Spring Expression Language.
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cas.authn.surrogate.sms.attribute-name=phone
Principal attribute name that indicates the destination phone number for this SMS message. The attribute must already be resolved and available to the CAS principal.
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cas.authn.surrogate.sms.from=
The from address for the message.
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cas.authn.surrogate.sms.text=
The body of the SMS message.
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cas.authn.surrogate.mail.bcc=
Email BCC address, if any.
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cas.authn.surrogate.mail.cc=
Email CC address, if any.
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cas.authn.surrogate.mail.html=false
Indicate whether the message body should be evaluated as HTML text.
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cas.authn.surrogate.mail.priority=1
Set the priority (
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cas.authn.surrogate.mail.reply-to=
Email Reply-To address, if any.
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cas.authn.surrogate.mail.text=
Email message body. Could be plain text or a reference to an external file that would serve as a template. If specified as a path to an external file with an extension.gtemplate , then the email message body would be processed using the Groovy template engine. The template engine uses JSP style <% %> script and <%= %> expression syntax or GString style expressions. The variable out is bound to the writer that the template is being written to. If using plain text, the contents are processed for string subtitution candidates using named variables. For example, you may refer to an expected url variable in the email text via ${url} , or use ${token} to locate the token variable. In certain cases, additional parameters are passed to the email body processor that might include authentication and/or principal attributes, the available locale, client http information, etc.
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cas.authn.surrogate.mail.validate-addresses=false
Set whether to validate all addresses which get passed to this helper.
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The following settings may also need to be defined to describe the mail server settings:
spring.mail.default-encoding=UTF-8
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spring.mail.host=
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spring.mail.jndi-name=
Session JNDI name. When set, takes precedence over other Session settings. How can I configure this property?
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spring.mail.password=
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spring.mail.port=
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spring.mail.properties=
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spring.mail.protocol=smtp
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spring.mail.test-connection=false
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spring.mail.username=
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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.
To learn more about available options, please see this guide or this guide.
Surrogate Principal Resolution
The following settings and properties are available from the CAS configuration catalog:
cas.authn.surrogate.principal.principal-transformation.groovy.location=
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, specially if the script set to reload on changes, you may need to adjust the total number ofinotify 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 .
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cas.authn.surrogate.principal.active-attribute-repository-ids=
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.
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cas.authn.surrogate.principal.attribute-resolution-enabled=
Whether attribute repositories should be contacted to fetch person attributes. Defaults to true if not set.
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cas.authn.surrogate.principal.principal-attribute=
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.
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cas.authn.surrogate.principal.principal-resolution-conflict-strategy=last
In the event that the principal resolution engine resolves more than one principal, (specially 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:
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cas.authn.surrogate.principal.principal-resolution-failure-fatal=
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.
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cas.authn.surrogate.principal.principal-transformation.blocking-pattern=
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. This setting supports the Spring Expression Language.
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cas.authn.surrogate.principal.principal-transformation.case-conversion=NONE
Indicate whether the principal identifier should be transformed into upper-case, lower-case, etc. Available values are as follows:
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cas.authn.surrogate.principal.principal-transformation.pattern=
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. This setting supports the Spring Expression Language.
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cas.authn.surrogate.principal.principal-transformation.prefix=
Prefix to add to the principal id prior to authentication. This setting supports the Spring Expression Language.
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cas.authn.surrogate.principal.principal-transformation.suffix=
Suffix to add to the principal id prior to authentication. This setting supports the Spring Expression Language.
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cas.authn.surrogate.principal.return-null=
Return a null principal object if no attributes can be found for the principal.
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cas.authn.surrogate.principal.use-existing-principal-id=
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.
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cas.authn.surrogate.principal.principal-transformation.groovy.location=
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, specially if the script set to reload on changes, you may need to adjust the total number ofinotify 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 .
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cas.authn.surrogate.principal.principal-transformation.blocking-pattern=
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. This setting supports the Spring Expression Language.
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cas.authn.surrogate.principal.principal-transformation.case-conversion=NONE
Indicate whether the principal identifier should be transformed into upper-case, lower-case, etc. Available values are as follows:
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