[Samba] pam_winbind fails to authenticate domain users on my debian wheezy domain member servers

Thu Jan 2 10:53:25 MST 2014

Dear Rowland,

thank you for your quick reply.

I tried again using the "cached_login" option as you pointed out (also
changed "winbind offline logon = yes" in my smb.conf), but that did not
change anything.

I also checked for apparmor and selinux, none of which seem to be active
(not even installed on my debian systems)

Here is my (latest) stack of pam configs for ssh:

/etc/pam.d/sshd:

# PAM configuration for the Secure Shell service

# Read environment variables from /etc/environment and
# /etc/security/pam_env.conf.
auth       required     pam_env.so # [1]
# In Debian 4.0 (etch), locale-related environment variables were moved to
# /etc/default/locale, so read that as well.
auth       required     pam_env.so envfile=/etc/default/locale

# Standard Un*x authentication.
@include common-auth

# Disallow non-root logins when /etc/nologin exists.
account    required     pam_nologin.so

# Uncomment and edit /etc/security/access.conf if you need to set complex
# access limits that are hard to express in sshd_config.
# account  required     pam_access.so

# Standard Un*x authorization.
@include common-account

# Standard Un*x session setup and teardown.
@include common-session

# Print the message of the day upon successful login.
# This includes a dynamically generated part from /run/motd.dynamic
# and a static (admin-editable) part from /etc/motd.
session    optional     pam_motd.so  motd=/run/motd.dynamic noupdate
session    optional     pam_motd.so # [1]

# Print the status of the user's mailbox upon successful login.
session    optional     pam_mail.so standard noenv # [1]

# Set up user limits from /etc/security/limits.conf.
session    required     pam_limits.so

# Set up SELinux capabilities (need modified pam)
# session  required     pam_selinux.so multiple

# Standard Un*x password updating.
@include common-password

/etc/pam.d/common-auth

#
# /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.
#
# As of pam 1.0.1-6, this file is managed by pam-auth-update by default.
# To take advantage of this, it is recommended that you configure any
# local modules either before or after the default block, and use
# pam-auth-update to manage selection of other modules.  See
# pam-auth-update(8) for details.

# here are the per-package modules (the "Primary" block)
auth    [success=2 default=ignore]    pam_unix.so nullok_secure
auth    [success=1 default=ignore]    pam_winbind.so krb5_auth
krb5_ccache_type=FILE cached_login try_first_pass
# here's the fallback if no module succeeds
auth    requisite            pam_deny.so
# prime the stack with a positive return value if there isn't one already;
# this avoids us returning an error just because nothing sets a success code
# since the modules above will each just jump around
auth    required            pam_permit.so
# and here are more per-package modules (the "Additional" block)
# end of pam-auth-update config

/etc/pam.d/common-account

#
# /etc/pam.d/common-account - authorization settings common to all services
#
# This file is included from other service-specific PAM config files,
# and should contain a list of the authorization modules that define
# the central access policy for use on the system.  The default is to
# only deny service to users whose accounts are expired in /etc/shadow.
#
# As of pam 1.0.1-6, this file is managed by pam-auth-update by default.
# To take advantage of this, it is recommended that you configure any
# local modules either before or after the default block, and use
# pam-auth-update to manage selection of other modules.  See
# pam-auth-update(8) for details.
#

# here are the per-package modules (the "Primary" block)
account    [success=2 new_authtok_reqd=done default=ignore]    pam_unix.so
account    [success=1 new_authtok_reqd=done default=ignore]
pam_winbind.so
# here's the fallback if no module succeeds
account    requisite            pam_deny.so
# prime the stack with a positive return value if there isn't one already;
# this avoids us returning an error just because nothing sets a success code
# since the modules above will each just jump around
account    required            pam_permit.so
# and here are more per-package modules (the "Additional" block)
# end of pam-auth-update config

/etc/pam.d/common-session

#
# /etc/pam.d/common-session - session-related modules common to all services
#
# This file is included from other service-specific PAM config files,
# and should contain a list of modules that define tasks to be performed
# at the start and end of sessions of *any* kind (both interactive and
# non-interactive).
#
# As of pam 1.0.1-6, this file is managed by pam-auth-update by default.
# To take advantage of this, it is recommended that you configure any
# local modules either before or after the default block, and use
# pam-auth-update to manage selection of other modules.  See
# pam-auth-update(8) for details.

# here are the per-package modules (the "Primary" block)
session    [default=1]            pam_permit.so
# here's the fallback if no module succeeds
session    requisite            pam_deny.so
# prime the stack with a positive return value if there isn't one already;
# this avoids us returning an error just because nothing sets a success code
# since the modules above will each just jump around
session    required            pam_permit.so
# and here are more per-package modules (the "Additional" block)
session    required    pam_unix.so
session    optional            pam_winbind.so
# end of pam-auth-update config

/etc/common-password

#
# /etc/pam.d/common-password - password-related modules common to all
services
#
# This file is included from other service-specific PAM config files,
# and should contain a list of modules that define the services to be
# used to change user passwords.  The default is pam_unix.

# Explanation of pam_unix options:
#
# The "sha512" option enables salted SHA512 passwords.  Without this option,
# the default is Unix crypt.  Prior releases used the option "md5".
#
# The "obscure" option replaces the old `OBSCURE_CHECKS_ENAB' option in
# login.defs.
#
# See the pam_unix manpage for other options.

# As of pam 1.0.1-6, this file is managed by pam-auth-update by default.
# To take advantage of this, it is recommended that you configure any
# local modules either before or after the default block, and use
# pam-auth-update to manage selection of other modules.  See
# pam-auth-update(8) for details.

# here are the per-package modules (the "Primary" block)
password    [success=2 default=ignore]    pam_unix.so obscure sha512
password    [success=1 default=ignore]    pam_winbind.so use_authtok
try_first_pass
# here's the fallback if no module succeeds
password    requisite            pam_deny.so
# prime the stack with a positive return value if there isn't one already;
# this avoids us returning an error just because nothing sets a success code
# since the modules above will each just jump around
password    required            pam_permit.so
# and here are more per-package modules (the "Additional" block)
# end of pam-auth-update config

I don't have pam_mkhomedir.so because the user home directories for my
domain users are already existing
I also don't have pam_cap.so -- actually don't know what it is good for

I also checked the authentication logs again and compared them to the logs
generated on the opensuse domain member (where pam_winbind works nicely).
The lines which seem to be the most suspicious on the debian wheezy
machines are:

Jan  2 12:23:55 websrv sshd[3541]: pam_winbind(sshd:auth): request
wbcLogonUser failed: WBC_ERR_AUTH_ERROR, PAM error: PAM_SYSTEM_ERR (4),
NTSTATUS: NT_STATUS_CONNECTION_DISCONNECTED, Error message was:
NT_STATUS_CONNECTION_DISCONNECTED
Jan  2 12:23:55 websrv sshd[3541]: pam_winbind(sshd:auth): internal module
error (retval = PAM_SYSTEM_ERR(4), user = 'georg')
Jan  2 12:23:55 websrv sshd[3541]: pam_winbind(sshd:auth):
[pamh:0x7f1d54cb2030] LEAVE: pam_sm_authenticate returning 4
(PAM_SYSTEM_ERR)

on OpenSuSE the request wbcLogonUser reports ok (or success, don't remember
exactly)

So, if I interpret the logs correctly, already the AUTH module of
pam_winbind fails, and the other sections of pam sshd are not even processed

With kind regards,

Georg