full-disclosure - Re: sshd logins without a source

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Message-ID: <4E7C78BF.6070401@blackhat.bz>
Date: Fri, 23 Sep 2011 20:17:03 +0800
From: BH <lists@...ckhat.bz>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: sshd logins without a source

Hi all,

Thank you all for the suggestions.

The systems in question are all Debian based. A typical log stanza for a 
login would be:

Sep 23 18:51:26 test sshd[25011]: Accepted publickey for root from 
10.0.1.1 port 35398 ssh2
Sep 23 18:51:27 test sshd[25011]: pam_unix(sshd:session): session opened 
for user root by (uid=0)

Or in the case of password authentication:

Sep 23 19:37:33 test sshd[30552]: Accepted password for root from 
10.0.1.1 port 50102 ssh2
Sep 23 19:37:33 test sshd[30552]: pam_unix(sshd:session): session opened 
for user root by (uid=0)

I am unable to reproduce an event from sshd that shows a login without a 
corresponding address, in every case I have tested the IP address is 
logged. I guess this could possibly mean the logs have been altered, 
from what I can tell only for this event.

The b/wtmp files dont have any events relevant. Only a single binary was 
running on them afterwards which was doing SIP attacks. The file was 
rm'ed but a copy was taken which I have.

The syslog configs match backups along with the sshd binary matching 
earlier copies.

Thanks

On 23/09/2011 8:05 PM, paul.szabo@...ney.edu.au wrote:
> Dear Laurelai,
>
>>> I do not think that sshd normally logs its source. ... To produce the
>>> desired log, I added to /etc/hosts.allow the line
>>> sshd : all : spawn /usr/bin/logger -t"%d[%p]" "Connection source %h port %r"
>>
>> Don't most modern Linux distros log sshd by default? If for whatever
>> reason yours doesn't you can set the log level in the sshd config.
>
> My Debian sshd comes with "LogLevel INFO" in /etc/ssh/sshd_config.
> I never found documentation on what a "LogLevel VERBOSE" would do,
> so never changed it; my hosts.allow line does exactly what I want,
> and a similar line can do it for telnetd also. (Don't laugh...)
>
> Cheers, Paul
>
> Paul Szabo   psz@...hs.usyd.edu.au   http://www.maths.usyd.edu.au/u/psz/
> School of Mathematics and Statistics   University of Sydney    Australia
>
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Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/