Multifactor Authentication (MFA)
CAS provides support for a variety of multifactor authentication providers and options, while allowing one to design their own. The secondary authentication factor always kicks in after the primary step and existing authentication sessions will be asked to step-up to the needed multifactor authentication factor, should the request or trigger require it. The satisfied authentication context is communicated back to the application as well to denote a successful multifactor authentication event.
At a minimum, you need answer the following questions:
- Which provider(s) are we using for multifactor authentication?
- How and for whom are we triggering multifactor authentication?
Supported Providers
The following multifactor providers are supported by CAS.
Provider | Id | Instructions |
---|---|---|
Duo Security | mfa-duo |
See this guide. |
Authy Authenticator | mfa-authy |
See this guide. |
Acceptto | mfa-acceptto |
See this guide. |
YubiKey | mfa-yubikey |
See this guide. |
RSA/RADIUS | mfa-radius |
See this guide. |
WiKID | mfa-radius |
See this guide. |
Google Authenticator | mfa-gauth |
See this guide. |
FIDO U2F | mfa-u2f |
See this guide. |
FIDO2 WebAuthN | mfa-webauthn |
See this guide. |
CAS Simple | mfa-simple |
See this guide. |
Swivel Secure | mfa-swivel |
See this guide. |
Inwebo | mfa-inwebo |
See this guide. |
Custom | Custom | See this guide. |
Microsoft has removed the ability for external SSO servers to use Azure MFA. To use Azure MFA, you must also have all your users authenticate using Azure AD SSO. You may want to route authentication requests to Azure AD SSO using the delegated authentication features of CAS.
Core Configuration
The following settings and properties are available from the CAS configuration catalog:
cas.authn.mfa.core.provider-selector-groovy-script.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.mfa.core.authentication-context-attribute=authnContextClass
Attribute returned in the final CAS validation payload that indicates the authentication context class satisfied in the event of a multifactor authentication attempt.
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cas.authn.mfa.core.content-type=application/cas
Content-type that is expected to be specified by non-web clients such as curl, etc in the event that the provider supports variations of non-browser based MFA. The value is treated as a regular expression.
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cas.authn.mfa.core.global-failure-mode=
Defines the global failure mode for the entire deployment. This is meant to be used a shortcut to define the policy globally rather than per application. Applications registered with CAS can still define a failure mode and override the global. Available values are as follows:
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cas.authn.mfa.core.provider-selection-enabled=false
In the event that multiple multifactor authentication providers are determined for a multifactor authentication transaction, this setting will allow one to interactively choose a provider out of the list of available providers. A trigger may be designed to support more than one provider, and rather than letting CAS auto-determine the selected provider via scripts or ranking strategies, this method puts the choice back onto the user to decide which provider makes the most sense at any given time.
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