Multifactor Authentication Trusted Device/Browser
In addition to triggers that are provided by the MFA functionality of CAS, there may be cases where you wish to let the user decide if the current browser/device should be trusted so as to skip subsequent MFA requests. The objective is for CAS to remember that decision for a configurable period of time and not bother the user with MFA until the decision is either forcefully revoked or considered expired.
Trusting a device during an MFA workflow would mean that the ultimate decision is remembered for that user of that location of that device. These keys are combined together securely and assigned to the final decision.
Before deployment, you should consider the following:
- Should users be optionally allowed to authorize the “current” device?
- …or must that happen automatically once MFA is commenced?
- How should user decisions and choices be remembered? Where are they stored?
- How long should user decisions be trusted by CAS?
- How is a trusted authentication session communicated back to an application?
Note that enabling this feature by default means it’s globally applied to all in the case if you have multiple MFA providers turned on. This can be optionally disabled and applied only to a selected set of providers.
Configuration
Support is provided via the following module:
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<dependency>
<groupId>org.apereo.cas</groupId>
<artifactId>cas-server-support-trusted-mfa</artifactId>
<version>${cas.version}</version>
</dependency>
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implementation "org.apereo.cas:cas-server-support-trusted-mfa:${project.'cas.version'}"
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dependencyManagement {
imports {
mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
}
}
dependencies {
implementation "org.apereo.cas:cas-server-support-trusted-mfa"
}
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dependencies {
/*
The following platform references should be included automatically and are listed here for reference only.
implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
*/
implementation "org.apereo.cas:cas-server-support-trusted-mfa"
}
Actuator Endpoints
The following endpoints are provided by CAS:
Settings
The following settings and properties are available from the CAS configuration catalog:
cas.authn.mfa.trusted.crypto.encryption.key=
The encryption key is a JWT whose length is defined by the encryption key size setting.
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cas.authn.mfa.trusted.crypto.signing.key=
The signing key is a JWT whose length is defined by the signing key size setting.
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cas.authn.mfa.trusted.core.authentication-context-attribute=isFromTrustedMultifactorAuthentication
If an MFA request is bypassed due to a trusted authentication decision, applications will receive a special attribute as part of the validation payload that indicates this behavior. Applications must further account for the scenario where they ask for an MFA mode and yet don’t receive confirmation of it in the response given the authentication session was trusted and MFA bypassed.
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cas.authn.mfa.trusted.core.auto-assign-device-name=false
When device registration is enabled, indicate whether a device name should be automatically selected and assigned by CAS.
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cas.authn.mfa.trusted.core.device-registration-enabled=true
Indicates whether CAS should ask for device registration consent or execute it automatically.
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cas.authn.mfa.trusted.core.key-generator-type=DEFAULT
Indicates how record keys for trusted devices would be generated so they can be signed/verified on fetch operations. Available values are as follows:
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cas.authn.mfa.trusted.crypto.alg=
The signing/encryption algorithm to use.
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cas.authn.mfa.trusted.crypto.enabled=true
Whether crypto operations are enabled.
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cas.authn.mfa.trusted.crypto.encryption.key-size=512
The encryption key size.
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cas.authn.mfa.trusted.crypto.signing.key-size=512
The signing key size.
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cas.authn.mfa.trusted.crypto.strategy-type=ENCRYPT_AND_SIGN
Control the cipher sequence of operations. The accepted values are:
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cas.authn.mfa.trusted.crypto.encryption.key=
The encryption key is a JWT whose length is defined by the encryption key size setting.
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cas.authn.mfa.trusted.crypto.signing.key=
The signing key is a JWT whose length is defined by the signing key size setting.
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cas.authn.mfa.trusted.crypto.alg=
The signing/encryption algorithm to use.
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cas.authn.mfa.trusted.crypto.enabled=true
Whether crypto operations are enabled.
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cas.authn.mfa.trusted.crypto.encryption.key-size=512
The encryption key size.
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cas.authn.mfa.trusted.crypto.signing.key-size=512
The signing key size.
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cas.authn.mfa.trusted.crypto.strategy-type=ENCRYPT_AND_SIGN
Control the cipher sequence of operations. The accepted values are:
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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:
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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:
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{
"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.
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.
Authentication Context
If an MFA request is bypassed due to a trusted authentication decision, applications will receive a special attribute as part of the validation payload that indicates this behavior. Applications must further account for the scenario where they ask for an MFA mode and yet don’t receive confirmation of it in the response given the authentication session was trusted and MFA bypassed.
Device Fingerprint
Please see this guide.
Bypass
Please see this guide.
Storage
User decisions must be remembered and processed later on subsequent requests. A background cleaner process is also automatically scheduled to scan the chosen repository/database/registry periodically and remove expired records based on configured threshold parameters.
In a clustered CAS deployment, it is best to keep the cleaner running on one designated CAS node only and turn it off on all others via CAS settings. Keeping the cleaner running on all nodes may likely lead to severe performance and locking issues.
The following settings and properties are available from the CAS configuration catalog:
cas.authn.mfa.trusted.cleaner.schedule.enabled=true
Whether scheduler should be enabled to schedule the job to run.
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cas.authn.mfa.trusted.cleaner.schedule.enabled-on-host=.*
Overrides
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cas.authn.mfa.trusted.cleaner.schedule.repeat-interval=PT2M
String representation of a repeat interval of re-loading data for an data store implementation. This is the timeout between consecutive job’s executions. This settings supports the
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cas.authn.mfa.trusted.cleaner.schedule.start-delay=PT15S
String representation of a start delay of loading data for a data store implementation. This is the delay between scheduler startup and first job’s execution This settings supports the
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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.
Default
If you do nothing, by default records are kept inside the runtime memory and cached for a configurable amount of time. This is most useful if you have a very small deployment with a small user base or if you wish to demo the functionality.
Others
Device registrations can also be managed using any one of the following strategies.
Storage | Description |
---|---|
JSON | See this guide. |
JDBC | See this guide. |
CouchDb | See this guide. |
MongoDb | See this guide. |
DynamoDb | See this guide. |
Redis | See this guide. |
REST | See this guide. |