CBA, MFA, and AADSTS54008 Certificate is not supported as first factor

[KingBear]

Greetings All,

I'm trying to get CBA MFA working for Azure AD, exchange online specifically, but I can't get past the following error:  AADSTS54008:  Multi-Factor authentication is required and the credential used (Certificate) is not supported as a First Factor.  Obviously, I have something configured incorrectly.  Does anyone have a suggestion?

What I'm trying to achieve is have our users login to Outlook online with their username and password and then have the option to select a user certificate as their second form of authentication.

Regards,

KB

[#2]

When you configure CBA, you can define whether it's to be used as single- or multi-factor, so check for that. The Protection level toggle under auth methods > CBA > Configure.

[#3]

Understood. I've set up two rules, which as I understand it, renders the toggle useless. I also have a conditional policy requiring MFA for the same users configured for Certificate-based authentication. If I remove the conditional access policy from the users, the authentication works and there is no error, but users can also sign in using their password only, which is unacceptable. I have to be missing something somewhere. As soon as I reinstate the conditional access policy, the error returns.

[#4]

@KingBear @VasilMichev 

Did you sort this out?

I encounter the same error in my test tenant, the user certificate is successfully mapped to my user.

If I switch the protection level over to "multifactor authentication" I get signed in without MFA prompt.

When I attempt to sign in with the protection level set to "single-factor authentication", sign-in fails with the error AADSTS54008: Multi-Factor authentication is required and the credential used (Certificate) is not supported as a First Factor. Contact your administrator for more information.

[#5]

@manshellstrom   Yes sir.  The settings below work as desired for my tenant. 

Be sure to check that you don't have any of policies in your tenant that may be conflicting. 

[#6]

@manshellstrom 

You ever figure this out?  I am having the same issue.  I only want the cert to be used as a single factor, and have the toggle and issuer rule set as such.  I have no policy oid rule for MFA. When entering upn, I choose log in with a certificate, and get the same error you cited.  My expectation is that the cert replaces password, and the user will require mfa through their default method, which is authenticator app.

[#7]

@jroth710 

No, and my best guess is that the service is broken.

You and I are reaching for the exact same functionality, but it seems you can't get this working without a certificate policy that can be mapped in the configuration.

We'are also missing the posibility to use OCSP in favor of CRL.

[#8]

@jroth710 

FYI it is misleading, but if you look at the Microsoft documentation on CBA, the only way to do MFA with a cert is to add a Policy O.I.D rule that checks for a value in your cert. The cert then acts as the first factor and second factor. There seems to be no other MFA options supported with CBA yet.

[#9]

Also, if you you are getting that MFA sign in error regarding "first factor", and want it to work with CBA, you have to disable MFA enforcement at the user level and make sure they aren't included in any other conditional access policies that require MFA. Just make sure you have other user account protections such as additional Conditional Access Policies based on device or IP Range etc. 

[#10]

So you're saying that limiting its use to "single factor" implies having to have MFA disabled entirely for the user, while enabling it for "multi-factor" basically makes this the equivalent of a FIDO key, minus the hardware security and pin? It simply can't be configured as the equivalent of any other form of single factor, so some other factor is needed to go along with it in order to authenticate? If so, that's pretty weak..

I guess this part of the documentation made me think otherwise-- thinking the experience would be cert replaces password, then the user can choose from mobile app, passcode, fido key, etc as a 2nd factor..

"If a unique user is found and the user has a conditional access policy and needs multifactor authentication (MFA) and the certificate authentication binding rule satisfies MFA, then Azure AD signs the user in immediately. If the certificate satisfies only a single factor, then it requests the user for a second factor to complete Azure AD Multi-Factor Authentication."

https://docs.microsoft.com/en-us/azure/active-directory/authentication/concept-certificate-based-aut...

[#11]

I saw the same article and it contradicts the way I interpret this article and my testing so far:

"The policy OID in the certificate matches the configured value of 1.2.3.4 and it will satisfy multifactor authentication. Similarly, the issuer in the certificate matches the configured value of CN=ContosoCA,DC=Contoso,DC=org and it will satisfy single-factor authentication."

"Because policy OID rule takes precedence over issuer rule, the certificate will satisfy multifactor authentication."

https://docs.microsoft.com/en-us/azure/active-directory/authentication/how-to-certificate-based-auth...

In my testing, with password as first factor, cert is not available as second factor. Windows Hello, FIDO/yubikey, Authenticator passwordless act as 1st factor and 2nd factor so can't be used with cert. Phone sign in can't be used with MFA. If MFA is enforced on the user account, Cert auth will fail with the "first factor" error message you guys are getting.

The documentation says unless the policy information is included in the cert and there is a Policy OID rule to verify it, MFA will fail. I have yet to verify this works as I have not been able to get the "certificate policies" identifiers in our certs yet.

[#12]

yeah we don't have policy OID's either, so can't test. Haven't dug into it yet, but obviously not something that gets enabled in a standard CA rollout.

I'll also need to check to see if phone sign-in is enabled on my test account, and if so try without. It would be nice if Microsoft could give some clarity on the confusing documentation. If it truly can't be used as a "single-factor" --meaning it replaces password but user still needs at least some other factor -- they are ignoring the most obvious and beneficial use case -- eliminating the use of a password while still enforcing another factor of security.

[#13]

It can be used as a single factor, and I have tested that successfully. As I said, MFA needs to be disabled on the user account and on any Conditional Access Policies. For these users I'm disabling password and other authentication methods.

[#14]

@mikey365: "Currently, password can't be disabled when CBA is enabled and the option to sign in using a password is displayed.": https://learn.microsoft.com/en-us/azure/active-directory/authentication/concept-certificate-based-au... -> So your suggestion can not be done at the moment. Would be the end game though in my view.

It's like @jroth710 says: "They are ignoring the most obvious and beneficial use case -- eliminating the use of a password while still enforcing another factor of security."

When you go to the Azure Portal, you can now add authentication strengths policies: https://portal.azure.com/#view/Microsoft_AAD_IAM/AuthenticationMethodsMenuBlade/~/AuthStrengths. What we need is the "Certificate Based Authentication (Single Factor) + Microsoft Authenticator (Push Notification)" combination under 'Multifactor authentication'. I'll keep hoping

[#15]

@SjoerdV It can be done. I do it now for a handful of users. SmartCardLogin Required is enforced in AD, and the cert auth method is assigned to the user. What that message is saying is "password" will still be a visible sign in option for the user, but all they have to do is click "other ways to sign in" and then click certificate...

[#16]

Hi,

you have to configure under multifactor policy that is passwordless only, after that with all cba setup everthing will work.

I am ataching print screens from my environment.

[#17]

Yes I got it to work with CBA as a single factor, but as soon as I try to
a) enforce MFA (through CA) or
b) use CBA as a multi factor method (in CBA settings)
the login process breaks with "Multifactor authentication is required and the credential used is not supported. Try signing in with another method."

What I just want to achieve is:
- User logs in with username
- CBA is selected as first factor (user selects the certificate configured)
- Authenticator App is used as second factor (user types in the numbers at the prompt)

If you (or anyone else) have a way to get this to work, I am very interested;-)

[#18]

Ah, finally got it to work. But just the other way around:
- User logs in with username
- Authenticator App is used as first factor (because passwordless is selected) (user types in the numbers at the prompt)
- CBA is selected as second factor (user selects the certificate configured)

In my setup CBA is configured with 'multi factor' as protection level

CA has two rules:
- one regular 'MFA required' (just like always)
- a second one (new policy!) requiring 'phishing resistant MFA' with 'Require authentication strength (Preview)' grant

That's Great!

[#19]

i have configured cba as single factor,in policies mutlifactor authenticstion as passwordless and in my ios configured authenticstor for phone sign in.
This way it worked first cba snd than numner matching from passwordless sign in 🙂

[#20]

Great stuff! I Really like the flexibility of this system.

To top it of I also use a 'Location based' CA rule, so even when my full browser profile gets hijacked (including session tokens) it won't work, off my private network.

Still I would like to see browsers encrypting their cookie database with some machine specific key, to make the cookies not work if they are used on a different machine. It feels very strange this massive security hole has gone unplugged for so long...

Cheers!