Bug#784112: /usr/sbin/saslauthd: saslauthd segfaults

Thomas Kupka itchy.de at gmail.com
Tue May 12 14:09:13 UTC 2015 

Dan,

the only lead I could have is a correlation between peaks of failed login
attempts (from malicious sources most likely, at a rate of precisely one
attempt every 5 seconds) and the segfaults. Does this help?

extract from mail.log:
May 10 10:17:50 mail cyrus/pop3[23539]: badlogin: no-data [60.29.221.174]
plaintext test SASL(-13): authentication failure: checkpass failed
May 10 10:17:55 mail cyrus/pop3[23540]: badlogin: no-data [60.29.221.174]
plaintext test SASL(-13): authentication failure: checkpass failed
May 10 10:18:00 mail cyrus/pop3[23541]: badlogin: no-data [60.29.221.174]
plaintext test SASL(-13): authentication failure: checkpass failed

extract from messages:
May 10 10:18:09 mail kernel: [641457.138137] saslauthd[18768]: segfault at
0 ip 00007fdf751b8c8a sp 00007ffd3cf92e58 error 4 in libc-2.19.so
[7fdf75137000+19f000]
May 10 10:18:14 mail kernel: [641461.917719] saslauthd[18773]: segfault at
0 ip 00007fdf751b8c8a sp 00007ffd3cf92e58 error 4 in libc-2.19.so
[7fdf75137000+19f000]
May 10 10:18:19 mail kernel: [641466.650182] saslauthd[18764]: segfault at
0 ip 00007fdf751b8c8a sp 00007ffd3cf92e58 error 4 in libc-2.19.so
[7fdf75137000+19f000]

After this peak was over, there have been no more segfaults for the next 8
hours.

On Tue, May 12, 2015 at 3:42 PM, Dan White <dwhite at olp.net> wrote:

> Thomas,
>
> Can you provide a reproducible case? e.g., does this happen on the first
> authentication attempt after starting saslauthd (with the shadow backend),
> or are there other factors at play that you can identify?
>
>
> On 05/12/15 11:08 +0200, Thomas Kupka wrote:
>
>> I have changed the backend to pam and had no segfaults for the last 3
>> days.
>> Seem like only the shadow backend has this issue.
>>
>> On Fri, May 8, 2015 at 9:10 AM, Thomas Kupka <itchy.de at gmail.com> wrote:
>>
>>
>>> On Wed, 6 May 2015 09:10:15 -0500 Dan White <dwhite at olp.net> wrote:
>>>
>>> > Can you get a backtrace from the core dump, and debug output, e.g.:
>>> >
>>> > saslauthd -d -c -m /var/spool/postfix/
>>>
>>> It does not seem that debug gives out any interesting information. Here
>>> are the last lines from when the child processes died:
>>>
>>> saslauthd[19194] :do_auth         : auth success: [user=thomas]
>>> [service=imap] [realm=] [mech=shadow]
>>> saslauthd[19194] :do_request      : response: OK
>>> saslauthd[19195] :rel_accept_lock : released accept lock
>>> saslauthd[19193] :get_accept_lock : acquired accept lock
>>> saslauthd[19193] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19193] :do_auth         : auth failure: [user=noauth]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19193] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=spam]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19193] :rel_accept_lock : released accept lock
>>> saslauthd[19193] :do_auth         : auth failure: [user=test]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=info]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19193] :get_accept_lock : acquired accept lock
>>> saslauthd[19193] :rel_accept_lock : released accept lock
>>> saslauthd[19193] :do_auth         : auth failure: [user=admin]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=administrator]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19193] :get_accept_lock : acquired accept lock
>>> saslauthd[19193] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=postmaster]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=sales]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=support]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=webmaster]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Incorrect password]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=help]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=contact]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=office]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>> saslauthd[19194] :do_auth         : auth failure: [user=staff]
>>> [service=smtp] [realm=] [mech=shadow] [reason=Invalid username]
>>> saslauthd[19194] :get_accept_lock : acquired accept lock
>>> saslauthd[19194] :rel_accept_lock : released accept lock
>>>
>>> The failed authentication attempts are certainly malicious software
>>> trying
>>> out default credentials but they seem to be handled normally.
>>>
>>> > This backend doesn't get used much these days. pam should functionally
>>> > replace it. Does it also produce a segfault?
>>>
>>> I will try this. I have shadow backend running for about 10 years now and
>>> never had this urge to change it.
>>>
>>> Thomas
>>>
>>> On Wed, May 6, 2015 at 4:10 PM, Dan White <dwhite at olp.net> wrote:
>>>
>>>  On 05/03/15 10:24 +0200, Thomas Kupka wrote:
>>>>
>>>>  Package: sasl2-bin
>>>>> Version: 2.1.26.dfsg1-13
>>>>> Severity: important
>>>>> File: /usr/sbin/saslauthd
>>>>>
>>>>> Dear Maintainer,
>>>>>
>>>>> since upgrading to Jessie, all saslauthd processes segfault on a
>>>>> multiple daily basis:
>>>>>
>>>>> May  3 06:26:12 mail kernel: [22739.740552] saslauthd[763]: segfault at
>>>>> 0 ip 00007faffd5d8c8a sp 00007ffda85ebe48 error 4 in libc-2.19.so
>>>>> [7faffd557000+19f000]
>>>>> May  3 06:26:12 mail kernel: [22739.928344] saslauthd[739]: segfault at
>>>>> 0 ip 00007faffd5d8c8a sp 00007ffda85ebe48 error 4 in libc-2.19.so
>>>>> [7faffd557000+19f000]
>>>>> May  3 06:26:12 mail kernel: [22740.127304] saslauthd[760]: segfault at
>>>>> 0 ip 00007faffd5d8c8a sp 00007ffda85ebe48 error 4 in libc-2.19.so
>>>>> [7faffd557000+19f000]
>>>>> May  3 10:04:24 mail kernel: [35831.420577] saslauthd[761]: segfault at
>>>>> 0 ip 00007faffd5d8c8a sp 00007ffda85ebe48 error 4 in libc-2.19.so
>>>>> [7faffd557000+19f000]
>>>>> May  3 10:04:24 mail kernel: [35831.607218] saslauthd[762]: segfault at
>>>>> 0 ip 00007faffd5d8c8a sp 00007ffda85ebe48 error 4 in libc-2.19.so
>>>>> [7faffd557000+19f000]
>>>>> May  3 10:04:24 mail postfix/smtpd[17269]: warning: SASL authentication
>>>>> failure: cannot connect to saslauthd server: Connection refused
>>>>>
>>>>>
>>>> Can you get a backtrace from the core dump, and debug output, e.g.:
>>>>
>>>> saslauthd -d -c -m /var/spool/postfix/var/run/saslauthd -a shadow
>>>>
>>>> I can't reproduce your segfault on my unstable system running
>>>> 2.1.26.dfsg1-13. However, I'm several version behind on some of the
>>>> linked
>>>> libraries.
>>>>
>>>>  -- Configuration Files:
>>>>
>>>>> /etc/default/saslauthd changed:
>>>>> START=yes
>>>>> DESC="SASL Authentication Daemon"
>>>>> NAME="saslauthd"
>>>>> MECHANISMS="shadow"
>>>>>
>>>>>
>>>> This backend doesn't get used much these days. pam should functionally
>>>> replace it. Does it also produce a segfault?
>>>>
>>>> --
>>>> Dan White
>>>>
>>>>
>>>
>>>
>>>
>  _______________________________________________
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>>
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>>
>
>
> --
> Dan White
> BTC Broadband
> Network Admin Lead
> Ph  918.366.0248 (direct)   main: (918)366-8000
> Fax 918.366.6610            email: dwhite at olp.net
> http://www.btcbroadband.com
>
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