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Old 19th May 2011, 17:33
Djamu Djamu is offline
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Default saslauthd memory leak > fix

This is an old issue that still isn't resolved on debian & derivates ( others ? )
maybe someone should include it in the howtos.

saslauthd's memory usage starts to climb handling invalid authentication requests, eventually eating all your server memory ( & swap ).
this is in fact a very serious issue, as it facilitates (D)DOS attacks by someone sending lots of crap auth. requests until the OOM process killer kicks in.

there's an easy workaround by changing /etc/default/saslauthd
OPTIONS="-c -m /var/spool/postfix/var/run/saslauthd -r"
OPTIONS="-n 0 -c -m /var/spool/postfix/var/run/saslauthd -r"
adding "-n 0" effectively prevents the saslauthd daemon from using thread processes by using forks instead.
( on 1 of my servers it used up 8GB and 16GB swap.... which was freed up instantaneously upon changing the config and invoking /etc/init.d/saslauthd restart )

if anybody has a better solution.. feel free to post

my 5 cents
Windows, the only virus you pay for

Last edited by Djamu; 19th May 2011 at 17:42.
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Old 2nd September 2014, 07:24
falcon7700 falcon7700 is offline
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Default (bump) Still a problem on Debian Squeeze

Recently ran into this problem on a "Prefect Server" built on Squeeze.

So, thanks again for the solution ;-)
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Old 9th September 2014, 09:50
Sir Henry Sir Henry is offline
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Thank you, this is indeed still a problem with the current version on Debian Squeeze. Look at the yearly memory graph, it is very interesting. The server stalled when the committed memory exceeded the available physical RAM (8GB) plus swap (2GB). This leak went unnoticed (*blush*) for one year to crash at last.

I found the culprit by adding another graph showing memory usage by process. Problem now solved with the no-thread option.
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Cheers, Sir Henry

Last edited by Sir Henry; 9th September 2014 at 09:54.
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Old 9th September 2014, 18:13
webguyz webguyz is online now
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Hmm. I don't have a /etc/default/saslauthd file, but I am using ISPConfig aand Postfix and I do see sasl auths going on in my mail.log so I mus be using it.

Is there an alternate location it might be in?

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Old 9th September 2014, 18:15
till till is offline
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If you use dovecot, then postfix is authenticating against dovecot and not saslauthd. saslauthd is used on courier setups.
Till Brehm
Get ISPConfig support and the ISPConfig 3 manual from ispconfig.org.
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Old 9th September 2014, 19:01
Sir Henry Sir Henry is offline
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Depending on your distribution this could also be in /etc/saslauthd.conf.
Cheers, Sir Henry
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