Hello Jakub,

I have prepared a patch (see Novell bugzilla) that adds a check for the "Decrypt integrity check failed" Kerberos error code to the switch statement, which then returns PAM_AUTH_ERR.

I tested that patch with OpenSUSE12.2 + KDM as well as SSH password based login and can confirm that the misleading error message goes away (for SSH there was only a misleading syslog error but not for the user).

However, the mentioned patch only changes the PAM return code when using Kerberos with a password. I am not sure if there may be other spots in the krb5_child that may also need fixing, as there are other possibilities to use Kerberos auth (forwarded TGT, keytab, and so on).

Best regards,
Joschi Brauchle

On 09/09/2012 04:03 PM, Jakub Hrozek wrote:
On Fri, Sep 07, 2012 at 05:44:59PM +0200, Joschi Brauchle wrote:
Hello,

I noticed a problem when using pam_sss (1.8.3) under OpenSUSE 12.2 +
KDE and filed a bugreport there:
https://bugzilla.novell.com/show_bug.cgi?id=779246

When a Kerberos user enters a wrong password, a KDM "Critical error"
message pops up (see link above for a screenshot).

In /var/log/messages, there is
------
Sep  7 11:34:03 test-os122 [sssd[krb5_child[1102]]]: Decrypt integrity check
failed
Sep  7 11:34:03 test-os122 [sssd[krb5_child[1102]]]: Decrypt integrity check
failed
Sep  7 11:34:03 test-os122 kdm: :0[1085]: pam_sss(xdm:auth): system info:
[Decrypt integrity check failed]
Sep  7 11:34:03 test-os122 kdm: :0[1085]: pam_sss(xdm:auth): authentication
failure; logname= uid=0 euid=0 tty=:0 ruser= rhost= user=testuser
Sep  7 11:34:03 test-os122 kdm: :0[1085]: pam_sss(xdm:auth):
received for user
testuser: 4 (System error)
------

As far as I know, "decrypt integrity fails" is the default Kerberos
error message for a wrong password. Hence, this is not a "System
error", but rather an authentication error.

When looking at the code of "krb5_child.c", it seems like the
default return code when checking the Kerberos TGT is
"PAM_SYSTEM_ERR", which also gets returned in the event of a simply
wrong password.

I guess, pam_sss should instead return "PAM_AUTH_ERR", is that correct?
Has this been fixed in versions > 1.8.3?


You are absolutely correct, nice catch Joschi.

It has not been fixed so, far, I have filed
https://fedorahosted.org/sssd/ticket/1515 to track this
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