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.
Client-side Sessions
CAS provides a facility for storing flow execution state on the client in Spring Webflow. Flow state is stored as an encoded byte stream in the flow execution identifier provided to the client when rendering a view. By default, CAS automatically attempts to store and keep track of this state on the client in an encrypted form via encryption and signing keys to remove the need for session cleanup, termination and replication.
The following settings and properties are available from the CAS configuration catalog:
cas.webflow.crypto.encryption.key=
The encryption key. The encryption key by default and unless specified otherwise must be randomly-generated string whose length is defined by the encryption key size setting.
|
cas.webflow.crypto.signing.key=
The signing key is a string whose length is defined by the signing key size setting. This setting supports the Spring Expression Language.
|
cas.webflow.session.storage=false
Controls whether spring webflow sessions are to be stored server-side or client side. By default state is managed on the client side, that is also signed and encrypted.
|
cas.webflow.crypto.alg=AES
The signing/encryption algorithm to use.
|
cas.webflow.crypto.enabled=true
Whether crypto operations are enabled.
|
cas.webflow.crypto.encryption.key-size=16
Encryption key size.
|
cas.webflow.crypto.signing-enabled=true
Whether signing encryption operations are enabled.
|
cas.webflow.crypto.signing.key-size=512
The signing key size.
|
cas.webflow.session.pin-to-session=false
Controls whether the webflow session is pinned to the client's IP address and user-agent.
|
cas.webflow.crypto.encryption.key=
The encryption key. The encryption key by default and unless specified otherwise must be randomly-generated string whose length is defined by the encryption key size setting.
|
cas.webflow.crypto.signing.key=
The signing key is a string whose length is defined by the signing key size setting. This setting supports the Spring Expression Language.
|
cas.webflow.crypto.alg=AES
The signing/encryption algorithm to use.
|
cas.webflow.crypto.enabled=true
Whether crypto operations are enabled.
|
cas.webflow.crypto.encryption.key-size=16
Encryption key size.
|
cas.webflow.crypto.signing-enabled=true
Whether signing encryption operations are enabled.
|
cas.webflow.crypto.signing.key-size=512
The signing key size.
|
This CAS feature is able to accept signing and encryption crypto keys. In most scenarios if keys are not provided, CAS will auto-generate them. The following instructions apply if you wish to manually and beforehand create the signing and encryption keys.
Note that if you are asked to create a JWK of a certain size for the key, you are to use the following set of commands to generate the token:
1
2
wget https://raw.githubusercontent.com/apereo/cas/master/etc/jwk-gen.jar
java -jar jwk-gen.jar -t oct -s [size]
The outcome would be similar to:
1
2
3
4
5
{
"kty": "oct",
"kid": "...",
"k": "..."
}
The generated value for k
needs to be assigned to the relevant CAS settings. Note that keys generated via
the above algorithm are processed by CAS using the Advanced Encryption Standard (AES
) algorithm which is a
specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology.
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, 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.
In the event that keys are not generated by the deployer, CAS will attempt to auto-generate keys and will output the result for each respective key. The deployer MUST attempt to copy the generated keys to their CAS properties file, especially when running a multi-node CAS deployment. Failure to do so will prevent CAS to properly decrypt and encrypt the webflow state and will prevent successful single sign-on.

While the above settings are all optional, it is recommended that you provide your own configuration and settings for encrypting and transcoding of the web session state.