[Dovecot] Dovecot under brute force attack - nice attacker

[henry ritzlmayr]

Am Donnerstag, den 04.06.2009, 09:51 -0700 schrieb Mark Sapiro:
> On Thu, Jun 04, 2009 at 12:16:00PM +0200, henry ritzlmayr wrote:
> > 
> > The problem:
> > If the attacker wouldn't have closed and reopened the connection
> > no log would have been generated and he/she would have endless 
> > tries. Not even an iptables/hashlimit or fail2ban would have kicked in.
> > 
> > How to reproduce:
> > telnet dovecot-server pop3
> > user test
> > pass test1
> > user test
> > pass test2
> > ...
> > QUIT
> > ->Only the last try gets logged.
> 
> 
> I see the same thing with Dovecot 1.2.rc4 on CentOS 5, but pam logs every
> failed attempt:
> 
> Jun  4 09:37:40 sbh16 dovecot-auth: pam_unix(dovecot:auth): check pass; user unknown
> Jun  4 09:37:40 sbh16 dovecot-auth: pam_unix(dovecot:auth): authentication failure; logname= uid=0 euid=0 tty=dovecot ruser=zzz rhost=127.0.0.1
> Jun  4 09:38:05 sbh16 dovecot-auth: pam_unix(dovecot:auth): check pass; user unknown
> Jun  4 09:38:05 sbh16 dovecot-auth: pam_unix(dovecot:auth): authentication failure; logname= uid=0 euid=0 tty=dovecot ruser=mmm rhost=127.0.0.1
> 
> So, fail2ban will block based on the pam log.
> 
Good to know. We have ldap here, but it certainly would be possible
to do the authentication through pam->ldap.

thanks 
Henry