FIDO2 WebAuthn Multifactor Authentication - Attestation Trust & Metadata

WebAuthn support in CAS can handle authenticator attestation, which provides a way for the web service to request cryptographic proof of what authenticator the user is using.

Attestation trust metadata can be taught to CAS using the following strategies.

JSON
FIDO

WebAuthn attestation trust metadata can be loaded from a JSON file and CAS by default ships with and has enabled metadata offered by Yubico, for a series of devices that are also primarily offered by Yubico.

The structure of this JSON file is as follows:

{
  "identifier": "...",
  "version": 1,
  "vendorInfo": {
    "url": "...",
    "imageUrl": "...",
    "name": "..."
  },
  "trustedCertificates": [ "..." ],
  "devices": [
    {
      "deviceId": "...",
      "displayName": "...",
      "transports": 4,
      "deviceUrl": "...",
      "imageUrl": ".",
      "selectors": [
        {
          "type": "x509Extension",
          "parameters": {
            "key": "...",
            "value": {
              "type": "hex",
              "value": "..."
            }
          }
        }
      ]
    }
  ]
}

The following settings and properties are available from the CAS configuration catalog:

cas.authn.mfa.web-authn.core.trust-source.trusted-device-metadata.locationThe location of the resource.

no default

Required

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, especially if the script is set to reload on changes, you may need to adjust the total number of inotify 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.

Type: Resource
Default: none
Defined by: SpringResourceProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Notes on configuration

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.

Note

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.

The FIDO Alliance Metadata Service (MDS) is a centralized repository of the Metadata Statement that is used by the relying parties to validate authenticator attestation and prove the genuineness of the device model. MDS also provides information about certification status of the authenticators, and found security issues. Organizations deploying FIDO Authentication are able to use this information to select specific certification levels as required for compliance, and work through the security notifications to ensure effective incident response.

Usage
To activate this functionality, you will need to accept the legal terms and conditions that are put together by FIDO Alliance via CAS configuration by specifying the appropriate legal header.

The following settings and properties are available from the CAS configuration catalog:

cas.authn.mfa.web-authn.core.trust-source.fido.legal-headerSet legal headers expected in the metadata BLOB.

no default

Required

Set legal headers expected in the metadata BLOB. By using the FIDO Metadata Service, you will be subject to its terms of service. This setting serves two purposes:

To remind you and any adopters/reviewers that you need to read those terms of service before using this feature. To help you detect if the legal header changes, so you can take appropriate action.

If the legal header in the downloaded BLOB does not equal any of the expected headers, an exception will be thrown in the finalizing configuration step.

Note that CAS makes no guarantee that a change to the FIDO Metadata Service terms of service will also cause a change to the legal header in the BLOB.

The current legal header is noted by: #DEFAULT_LEGAL_HEADER which is the following:

"Retrieval and use of this BLOB indicates acceptance of the appropriate agreement located at https://fidoalliance.org/metadata/metadata-legal-terms/".

Type

String

Default

none

Defined by

WebAuthnMultifactorAttestationTrustSourceFidoProperties

cas.authn.mfa.web-authn.core.trust-source.fido.metadata-blob-urlDownload the metadata BLOB from the FIDO website.

https://mds3.fidoalliance.org/

Required

Download the metadata BLOB from the FIDO website. This is the current FIDO Metadata Service BLOB download URL.

Type

String

Default

https://mds3.fidoalliance.org/

Defined by

WebAuthnMultifactorAttestationTrustSourceFidoProperties

cas.authn.mfa.web-authn.core.trust-source.fido.trust-root-hashCertificate SHA-256 hash required for PKI to verify the downloaded certificate.

cbb522d7b7f127ad6a0113865bdf1cd4102e7d0759af635a7cf4720dc963c53b

Required

Certificate SHA-256 hash required for PKI to verify the downloaded certificate. Separate hash values with a comma.

Type

String

Default

cbb522d7b7f127ad6a0113865bdf1cd4102e7d0759af635a7cf4720dc963c53b

Defined by

WebAuthnMultifactorAttestationTrustSourceFidoProperties

cas.authn.mfa.web-authn.core.trust-source.fido.trust-root-urlCertificate required for PKI to verify the downloaded blob.

https://secure.globalsign.com/cacert/root-r3.crt

Required

Certificate required for PKI to verify the downloaded blob. This is the current FIDO Metadata Service trust root certificate. If the cert is downloaded, it is also written to the cache File. The certificate will be downloaded if it does not exist in the cache, or if the cached certificate is not currently valid.

Type

String

Default

https://secure.globalsign.com/cacert/root-r3.crt

Defined by

WebAuthnMultifactorAttestationTrustSourceFidoProperties

cas.authn.mfa.web-authn.core.trust-source.fido.blob-cache-fileCache metadata BLOB in the file cache file.

no default

Cache metadata BLOB in the file cache file. If cache file exists, is a normal file, is readable, and is not out of date, then it will be used as the FIDO Metadata Service BLOB.

Otherwise, the metadata BLOB will be downloaded and written to this file.

Type

File

Default

none

Defined by

WebAuthnMultifactorAttestationTrustSourceFidoProperties

cas.authn.mfa.web-authn.core.trust-source.fido.trust-root-cache-fileCache the trust root certificate in the file cache file.

no default

Cache the trust root certificate in the file cache file. If cache file exists, is a normal file, is readable, matches one of the SHA-256 hashes configured in and contains a currently valid X.509 certificate, then it will be used as the trust root for the FIDO Metadata Service blob.

Otherwise, the trust root certificate will be downloaded and written to this file.

Type

File

Default

none

Defined by

WebAuthnMultifactorAttestationTrustSourceFidoProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Notes on configuration

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.

Note
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.