Simple MFA to Surrogate bypasses surrogate selection

[Anthony Oslund]

Start by stating current deployment uses 6.6.6 with DBMS authentication, not LDAP.

Deployment uses the groovy approach for triggering simple MFA.  

Based on much testing and researching of this archive determined that if simple MFA is activated through groovy script that CAS will bypass surrogate selection.  From researching this archive others have run into the same limitation (at least for 6.6.6 and earlier, not sure about later versions).

For surrogate logging in using the +username / pass approach and then selecting surrogate from drop down.

Surrogate process functions correctly, but only if MFA not selected by the groovy script.  This is true even if MFA not required in that exact login instance, having been satisfied by recent/previous login/MFA.  For example, groovy script determines that MFA is required for +username... system examines recent MFA cache... regardless if MFA required/not required at this moment.... surrogate process bypassed and authenticated/released parameters are for original +username.

Current deployment's security requirements restrict surrogate to internal use only, while only requiring MFA externally so at this time not an issue as both MFA and surrogate are working within their separate external/internal scopes.  Future requirements may likely require MFA internally as well, which with current deployment would conflict with internal scope surrogate process.


Looking at attached groovy scripts from other posts it appears they are potentially using other MFA ("mfa-gauth", "mfa-webauthn").  Perhaps issue with our deployment is a default web flow issue specific to simple MFA.


Simple MFA currently works in all instances, but does not flow to surrogate.  If groovy script below returns null for MFA then flow to surrogate selection works as intended.


import java.util.*
 
class SampleGroovyProviderSelection {

    def String run(final Object... args) {
        def service = args[0]
        def authentication = args[2]
        def request = args[3]
        def logger = args[4]

        def mfa = null

        def email = authentication.principal.attributes['email']
        def phone = authentication.principal.attributes['phone']
        def mfaMode = authentication.principal.attributes['mfa_mode']

        logger.info('Groovy script for mfa')
        logger.info(mfaMode)
        logger.info(email)
        logger.info(phone)

        /*
           If user lacks both email and phone then bypass MFA
           
           If plan is to prevent the user from authenticating if
           they cannot use MFA, that should be handled further upstream
           through the DBMS view.  It can simply prevent them from
           ever authenticating (if that is the desired outcome), in
           which case they will never even get to this point
        */
        if (mfaMode && (email || phone)) {
          if (mfaMode.contains("Y")) {
             mfa = ["mfa-simple"]
          }
        }
        return mfa
    }
}

[Ray Bon]

Anthony,

Does surrogate+username / password approach work, or is it only the surrogate selection that does not work?

If I use surrogate+ with a service that requires MFA, it goes through the mfa flow for username and then to service as surrogate. But I do not have any groovy scripts running.

Ray

On Tue, 2023-07-25 at 10:31 -0700, Anthony Oslund wrote:

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[John]

We use mfa-simple for database auths as well, which groovy mfa are you using? cas.authn.mfa.core.provider-selector-groovy-script OR cas.authn.mfa.groovy-script which is what we use,

[Anthony Oslund]

Really appreciate the quick responses.

Currently using cas.authn.mfa.groovy-script.location=file:/somepath/mfa_trigger.groovy (script contents same as previous message)

Oddly the adminuser+surrogate approach does not work at all.  It won't authenticate.  That has not presented much of an issue as we have so many potential surrogates that we use the +adminuser/password approach followed by the drop down selection of the surrogate.

MFA within our context is in regards to the original +adminuser, not in regards to MFA for the surrogate themselves (.... so intent is for MFA to occur and then surrogate selection).

Correct in assuming that the what appears to be the failure is the bypass of the surrogate drop down selection when using the +adminuser approach if the groovy script returns "mfa-simple".  If the groovy script returns null then surrogate drop down selection works correctly with +adminuser/password.

[John]

We don't use the surrogate selector at all, the person has to know the account name, and for your login you should be using ` surrogate+adminuser ` and not  ` adminuser+surrogate `. Have you turned on debug? Do you have sufficient debug logging messages in your groovy script to track through the whole process? The debug logs can give you a good clue into where or why it would be not working.

[Anthony Oslund]

Thanks for your reply John.

Read the docs repeatedly and somehow kept reading that as admin+surrogate rather than surrogate+admin. 

However, there is still a default "web flow" issue between MFA and surrogate.

When tested as +admin with the drop down it triggers simple MFA but bypasses surrogate drop down selection.

When tested as you suggested as surrogate+admin (which does correctly authenticate), it bypasses MFA and does correctly bring up the surrogate.

Should point out that if MFA groovy script returns null it will correctly display the surrogate drop down.  So If I disable MFA, which is what we currently have for our internal logins, then surrogate selection works.

[John]

Took me a few to get a few different container versions ready, and it looks like it was a bug. We have been using surrogate for only a few months and have been using a 'master' branch container as primary on our app controller for a while and it doesn't occur and fixed in master many moons ago. See here, https://github.com/apereo/cas/commit/3a8cb528850d3822dbeba7a73f7e3bf85d3d9abc , you could switch to latest tag in gradle if you dont want to build off master, tag is 7.0.0-RC6 ,