Secure/Lock accounts with PAM tally2
pam_tally2 is a PAM module to allow interaction in users interfaces on numbers of failed login attempt it can reset count on success, can deny access if too many attempts fail.
this module is unique because it not just reflect remote connection but also reflect the ttys and any system login method as it uses PAM
example from tty:
Centos release 6.5 (Final) Kernel 2.6.32-431.el6.x86 on an x86_64 centos-6 login:n1x Account locked due to 8 failed logins Password:
some parameters
- deny used to block access of numbers of failed attempts
- unlock_time used to set a time duration for blocked access in seconds
- even_deny_root root is excluded by default, you set this parameter to tell tally2 count for root too
- root_unlock_time same as unlock_time but for root only
example PAM config:
auth required pam_tally2.so deny=2 unlock_time=30 even_deny_root root_unlock_time=10
to reflect the tty access we have to configure our tally2 module in /etc/pam.d/system-auth
here is our final layout for system-auth
#%PAM-1.0 # This file is auto-generated. # User changes will be destroyed the next. auth required pam_env.so auth required pam_tally2.so deny=2 unlock_time=30 even_deny_root root_unlock_time=10 auth sufficient pam_unix.so nullok try_first_pass auth requisite pam_succeed_if.so uid >= 500 quiet auth required pam_deny.so account required pam_tally2.so account required pam_unix.so account sufficient pam_localuser.so account sufficient pam_succeed_if.so uid < 500 quiet account required pam_permit.so password requisite pam_cracklib.so try_first_pass retry=3 type= password sufficient pam_unix.so sha512 shadow nullok try_first_pass use_authtok password required pam_deny.so session optional pam_keyinit.so revoke session required pam_limits.so session [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid session required pam_unix.so ~
to reflect the remote connections that use password example sshd
we config our /etc/pam.d/password-auth with tally
#%PAM-1.0 # This file is auto-generated. # User changes will be destroyed the next time authconfig is run. auth required pam_env.so auth required pam_tally2.so deny=2 unlock_time=30 even_deny_root root_unlock_time=10 auth sufficient pam_unix.so nullok try_first_pass auth requisite pam_succeed_if.so uid >= 500 quiet auth required pam_deny.so account required pam_tally2.so account required pam_unix.so account sufficient pam_localuser.so account sufficient pam_succeed_if.so uid < 500 quiet account required pam_permit.so password requisite pam_cracklib.so try_first_pass retry=3 type= password sufficient pam_unix.so sha512 shadow nullok try_first_pass use_authtok password required pam_deny.so session optional pam_keyinit.so revoke session required pam_limits.so session [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid session required pam_unix.so
notice that we have done 2 things one in auth interface that verifies the account and 2nd one in the account interface to reflect the permissions of the account
here is some output of /var/log/secure
Aug 5 02:09:53 centos-6 login: pam_tally2(login:auth): user root (0) tally 3, deny 2 Aug 5 02:13:37 centos-6 sshd[12921]: pam_tally2(sshd:auth): user root (0) tally 10, deny 2
as you see tally2 kills the connection 🙂
for manual interaction with tally2 counter
there is a command called pam_tally2
[root@centos-6 ~]# pam_tally2 Login Failures Latest failure From root 2 08/05/15 02:11:45 192.168.72.1
to remove a counter failures
[root@centos-6 ~]# pam_tally2 -r -u root Login Failures Latest failure From root 10 08/05/15 02:13:37 192.168.72.1 [root@centos-6 ~]# pam_tally2 -r -u root Login Failures Latest failure From root 0
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