Double password check in Debian Etch login

brgsousa · 10-08-2008, 02:14 PM

Hi,
i am having a problem with linux login.
The old administrator did something with pam files i think. And now we have to enter user password twice to make it log in.
That is making automated scripts etc to go wrong.

Any clues so that it asks only one time?

Matir · 10-08-2008, 06:03 PM

Look at the pam configuration and see what modules are being used other than pam_unix.so in the auth stack. Particularly, anything like pam_ssh, pam_mount, etc. If so, they should usually be called with the try_first_pass option. Also, do the prompts look the same?

brgsousa · 10-09-2008, 06:58 AM

The authentication screen from PuTTY looks like this:

Code:

Using username "root".
Using keyboard-interactive authentication.
Password:
Using keyboard-interactive authentication.
Password:
Last login: Wed Oct  8 19:24:04 2008 from 10.1.4.55
hostname_here:~#

Did you mean auth stack by this?

Code:

# ls /lib/security
pam_access.so   pam_limits.so       pam_rootok.so     pam_unix_passwd.so
pam_debug.so    pam_listfile.so     pam_securetty.so  pam_unix_session.so
pam_deny.so     pam_mail.so         pam_shells.so     pam_unix.so
pam_env.so      pam_mkhomedir.so    pam_smbpass.so    pam_userdb.so
pam_filter.so   pam_motd.so         pam_stress.so     pam_warn.so
pam_ftp.so      pam_nologin.so      pam_tally.so      pam_wheel.so
pam_group.so    pam_permit.so       pam_time.so       pam_winbind.so
pam_issue.so    pam_radius_auth.so  pam_unix_acct.so
pam_lastlog.so  pam_rhosts_auth.so  pam_unix_auth.so

Matir · 10-09-2008, 07:03 AM

What distribution are you on? On Debian-based systems, we have /etc/pam.d that contains the pam configuration files which tell PAM which modules to load and what options to pass to those modules.

Matir · 10-09-2008, 07:11 AM

Oops, I totally had forgotten the subject of the thread. Guess I've already been looking at too many this morning.

Look at /etc/pam.d/common-auth and see if pam_unix is called twice.

Also, does logging in at the console generate a double prompt as well? Perhaps it's an issue with SSH's configuration if it's only via SSH.

brgsousa · 10-09-2008, 09:16 AM

It looks like this:

Code:

#
# /etc/pam.d/common-auth - authentication settings common to all services
#
# This file is included from other service-specific PAM config files,
# and should contain a list of the authentication modules that define
# the central authentication scheme for use on the system
# (e.g., /etc/shadow, LDAP, Kerberos, etc.).  The default is to use the
# traditional Unix authentication mechanisms.
#
#auth   sufficient      pam_radius_auth
auth    sufficient      pam_winbind.so
auth    required        pam_unix.so nullok_secure

In console it asks twice too... :/

I just noticed that is not relevant what you enter for password for the first time. The second prompt that is checked

Matir · 10-09-2008, 09:19 AM

Are you authenticating against a domain? The first prompt is pam_winbind asking for the domain, and the 2nd is pam_unix. My guess is that there's no domain in use, or else a correct first password would 'suffice' via pam_winbind. If there's no domain in use, you can comment out the pam_winbind.so line.

brgsousa · 10-09-2008, 09:31 AM

This server is a mail server that authenticates mail users in AD server. But i think this is misconfiguration.
If i comment this line

Code:

auth    sufficient      pam_winbind.so

will it work?

Matir · 10-09-2008, 11:04 AM

It should work. I don't *THINK* pam.d/common-auth is used in the mail stack, but it depends on what mailserver you're using. Look and see if there's a pam.d/<mailserver> file with a separate configuration and make sure it doesn't have "@include common-auth" in it.

brgsousa · 10-13-2008, 01:03 PM

Yes, it does interfere in dovecot configuration.

/etc/pam.d/dovecot:

Code:

#%PAM-1.0

@include common-auth
@include common-account
@include common-session

I commented "auth sufficient pam_winbind.so" line in common-auth and common-account files and email stoped authenticating.

Matir · 10-13-2008, 01:17 PM

In common-auth, try adding "try_first_pass" to the pam_unix.so line, after nullok_secure.

brgsousa · 10-14-2008, 07:04 AM

I commented 'account sufficient pam_winbind.so' line in common-auth, common-account and common-session.

And dovecot is like this now:

Code:

#%PAM-1.0

account sufficient      pam_winbind.so
auth    sufficient      pam_winbind.so
session required        pam_winbind.so

#@include common-auth
#@include common-account
#@include common-session

Now, everything is working

thanks for your help dude

Matir · 10-14-2008, 07:58 AM

That works too

Glad you got it fixed!