On 01/30/2015 10:54 AM, Orion Poplawski wrote:
On 01/29/2015 01:47 AM, Sumit Bose wrote:
> On Wed, Jan 28, 2015 at 03:11:15PM -0700, Orion Poplawski wrote:
>> I'm looking for some help with this problem. I'd like to have
>> fail2ban block
>> systems trying to authenticate via smtp or imap. However, for known
>> users I get:
>>
>> Jan 28 13:33:36 mail auth: pam_unix(dovecot:auth): authentication
>> failure;
>> logname= uid=0 euid=0 tty=dovecot ruser=frank rhost=189.22.108.130
>> user=known_user
>> Jan 28 13:33:37 mail auth: pam_sss(dovecot:auth): authentication
>> failure;
>> logname= uid=0 euid=0 tty=dovecot ruser=frank rhost=189.22.108.130
>> user=known_user
>>
>> and for unknown users I get:
>>
>> Jan 28 13:27:16 mail auth: pam_unix(dovecot:auth): authentication
>> failure;
>> logname= uid=0 euid=0 tty=dovecot ruser=unknown_user
>> rhost=189.22.108.130
>>
>> so I can't key off of the pam_unix messages because that will lock
>> out known
>> users, and keying off of pam_sss will only block attacks that guess
>> a correct
>> username. Is there some way I can get pam_sss to log the unknown
>> user attempts?
>
> How does your full pam configuration looks like. E.g. on Fedora I have a
>
> auth requisite pam_succeed_if.so uid >= 1000 quiet_success
>
> line between pam_unix and pam_sss. Since the user is not known it will
> not have a uid and not go pass this line.
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 500 quiet
auth sufficient pam_sss.so use_first_pass
auth required pam_deny.so
What you say doesn't make sense to me though. As I read the docs, if
uid < 500 (as returned by pam_unix), pam_succeed_if will fail and stop
pam processing, so as to prevent authenticating system users against
sss. But if uid >= 500, it continues on to pam_sss. For unknown
users (no uid), it would seem to me that it would have to continue on
to sss, otherwise how would you authenticate users not in
/etc/passwd? It just appears to me that pam_sss is not logging
attempts by unknown users, and I'm not sure why.
May be at this point it would make sense to file a ticket so that we
have it recorded and provide a more formal investigation.
--
Thank you,
Dmitri Pal
Sr. Engineering Manager IdM portfolio
Red Hat, Inc.