FIDO2 WebAuthn Multifactor Authentication
WebAuthn is an API that makes it very easy for a relying party, such as a web service, to integrate strong authentication into applications using support built in to all leading browsers and platforms. This means that web services can now easily offer their users strong authentication with a choice of authenticators such as security keys or built-in platform authenticators such as biometric readers.
Support is enabled by including the following module in the WAR overlay:
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<dependency>
<groupId>org.apereo.cas</groupId>
<artifactId>cas-server-support-webauthn</artifactId>
<version>${cas.version}</version>
</dependency>
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implementation "org.apereo.cas:cas-server-support-webauthn:${project.'cas.version'}"
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dependencyManagement {
imports {
mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
}
}
dependencies {
implementation "org.apereo.cas:cas-server-support-webauthn"
}
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dependencies {
/*
The following platform references should be included automatically and are listed here for reference only.
implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
*/
implementation "org.apereo.cas:cas-server-support-webauthn"
}
The following settings and properties are available from the CAS configuration catalog:
cas.authn.mfa.web-authn.crypto.encryption.key=
The encryption key is a JWT whose length is defined by the encryption key size setting. This setting supports the Spring Expression Language.
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cas.authn.mfa.web-authn.crypto.signing.key=
The signing key is a JWT whose length is defined by the signing key size setting. This setting supports the Spring Expression Language.
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cas.authn.mfa.web-authn.core.application-id=
The extension input to set for the
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cas.authn.mfa.web-authn.core.relying-party-id=
The id that will be set as the rp parameter when initiating registration operations, and which id hash will be compared against. This is a required parameter. A successful registration or authentication operation requires rp id hash to exactly equal the SHA-256 hash of this id member. Alternatively, it may instead equal the SHA-256 hash of application id if the latter is present.
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cas.authn.mfa.web-authn.core.relying-party-name=
The human-palatable name of the Relaying Party.
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cas.authn.mfa.web-authn.crypto.alg=
The signing/encryption algorithm to use.
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cas.authn.mfa.web-authn.crypto.enabled=true
Whether crypto operations are enabled.
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cas.authn.mfa.web-authn.crypto.encryption.key-size=512
The encryption key size.
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cas.authn.mfa.web-authn.crypto.signing.key-size=512
The signing key size.
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cas.authn.mfa.web-authn.crypto.strategy-type=ENCRYPT_AND_SIGN
Control the cipher sequence of operations. The accepted values are:
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cas.authn.mfa.web-authn.core.allow-primary-authentication=false
Configure the authentication flow to allow web-authn to be used as the first primary factor for authentication. Registered accounts with a valid webauthn registration record can choose to login using their device as the first step.
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cas.authn.mfa.web-authn.core.allow-untrusted-attestation=false
If false finish registration op will only allow registrations where the attestation signature can be linked to a trusted attestation root. This excludes self attestation and none attestation. Regardless of the value of this option, invalid attestation statements of supported formats will always be rejected. For example, a "packed" attestation statement with an invalid signature will be rejected even if this option is set to true.
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cas.authn.mfa.web-authn.core.allowed-origins=
The allowed origins that returned authenticator responses will be compared against. The default is set to the server name. A successful registration or authentication operation requires origins to exactly equal one of these values.
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cas.authn.mfa.web-authn.core.attestation-conveyance-preference=DIRECT
Accepted values are:
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cas.authn.mfa.web-authn.core.display-name-attribute=displayName
Name of the principal attribute that indicates the principal's display name, primarily used for device registration.
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cas.authn.mfa.web-authn.core.enabled=true
Whether WebAuthn functionality should be activated and enabled.
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cas.authn.mfa.web-authn.core.expire-devices=30
Expire and forget device registration records after this period.
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cas.authn.mfa.web-authn.core.expire-devices-time-unit=
Device registration record expiration time unit.
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cas.authn.mfa.web-authn.core.multiple-device-registration-enabled=false
When enabled, allows the user/system to accept multiple accounts and device registrations per user, allowing one to switch between or register new devices/accounts automatically.
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cas.authn.mfa.web-authn.core.trusted-device-enabled=false
Indicates whether this provider should support trusted devices.
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cas.authn.mfa.web-authn.core.validate-signature-counter=true
If true, finish assertion op will fail if the signature counter value in the response is not strictly greater than the stored signature counter value.
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cas.authn.mfa.web-authn.crypto.encryption.key=
The encryption key is a JWT whose length is defined by the encryption key size setting. This setting supports the Spring Expression Language.
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cas.authn.mfa.web-authn.crypto.signing.key=
The signing key is a JWT whose length is defined by the signing key size setting. This setting supports the Spring Expression Language.
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cas.authn.mfa.web-authn.crypto.alg=
The signing/encryption algorithm to use.
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cas.authn.mfa.web-authn.crypto.enabled=true
Whether crypto operations are enabled.
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cas.authn.mfa.web-authn.crypto.encryption.key-size=512
The encryption key size.
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cas.authn.mfa.web-authn.crypto.signing.key-size=512
The signing key size.
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cas.authn.mfa.web-authn.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. 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.
Bypass
The following settings and properties are available from the CAS configuration catalog:
cas.authn.mfa.web-authn.bypass.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 . 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 .
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cas.authn.mfa.web-authn.bypass.rest.url=
The endpoint URL to contact and retrieve attributes.
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cas.authn.mfa.web-authn.bypass.authentication-attribute-name=
Skip multifactor authentication based on designated authentication attribute names.
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cas.authn.mfa.web-authn.bypass.authentication-attribute-value=
Optionally, skip multifactor authentication based on designated authentication attribute values. Multiple values may be separated by a comma. This settings supports regular expression patterns. [?].
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cas.authn.mfa.web-authn.bypass.authentication-handler-name=
Skip multifactor authentication depending on form of primary authentication execution. Specifically, skip multifactor if the a particular authentication handler noted by its name successfully is able to authenticate credentials in the primary factor. Multiple values may be separated by a comma. This settings supports regular expression patterns. [?].
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cas.authn.mfa.web-authn.bypass.authentication-method-name=
Skip multifactor authentication depending on method/form of primary authentication execution. Specifically, skip multifactor if the authentication method attribute collected as part of authentication metadata matches a certain value. Multiple values may be separated by a comma. This settings supports regular expression patterns. [?].
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cas.authn.mfa.web-authn.bypass.credential-class-type=
Skip multifactor authentication depending on form of primary credentials. Value must equal the fully qualified class name of the credential type.
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cas.authn.mfa.web-authn.bypass.http-request-headers=
Skip multifactor authentication if the http request contains the defined header names. Header names may be comma-separated and can be regular expressions; values are ignored. This settings supports regular expression patterns. [?].
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cas.authn.mfa.web-authn.bypass.http-request-remote-address=
Skip multifactor authentication if the http request's remote address or host matches the value defined here. The value may be specified as a regular expression. This settings supports regular expression patterns. [?].
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cas.authn.mfa.web-authn.bypass.principal-attribute-name=
Skip multifactor authentication based on designated principal attribute names.
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cas.authn.mfa.web-authn.bypass.principal-attribute-value=
Optionally, skip multifactor authentication based on designated principal attribute values. This settings supports regular expression patterns. [?].
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cas.authn.mfa.web-authn.bypass.rest.basic-auth-password=
If REST endpoint is protected via basic authentication, specify the password for authentication.
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cas.authn.mfa.web-authn.bypass.rest.basic-auth-username=
If REST endpoint is protected via basic authentication, specify the username for authentication.
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cas.authn.mfa.web-authn.bypass.rest.headers=
Headers, defined as a Map, to include in the request when making the REST call. Will overwrite any header that CAS is pre-defined to send and include in the request. Key in the map should be the header name and the value in the map should be the header value.
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cas.authn.mfa.web-authn.bypass.rest.method=GET
HTTP method to use when contacting the rest endpoint. Examples include
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Please review this guide to configure your build.
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. 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.
Discoverable Credentials
It is possible to allow WebAuthN to act as a standalone authentication strategy for primary authentication. Using this approach, user accounts and FIDO2-enabled devices that have already registered with CAS are given the option to login using their FIDO2-enabled device for a passwordless authentication experience.
Discoverable Credential means that the private key and associated metadata is stored in persistent memory on the authenticator, instead of encrypted and stored on the relying party server.
Device registration can occur out of band using available CAS APIs, or by allowing users to pass through the registration flow as part of the typical multifactor authentication. See below for details on device registration.