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From Luke Kenneth Casson Leighton <l...@samba-tng.org>
Subject Re: lib/apr_signal.c
Date Wed, 11 Jul 2001 15:07:31 GMT
On Wed, Jul 11, 2001 at 07:43:14AM -0700, rbb@covalent.net wrote:
> 
> APR doesn't really handle signals, for a very good reason.  They are
> incredibly non-portable, and very difficult to deal with.  Having said
> that, there are some APR functions for dealing with signals.
> 
> 1)  apr_signal.  Just like signal, only portable and predictable
> 
> 2)  apr_signal_thread  puts a single thread into sigwait.  Whenever ANY
> signal is received that thread is woken up, and a function is called.  The
> function is passed in to the setup_signal_thread function.
> 
> 3)  You can get a list of signals understood by the machine.  I can't
> remember the function, but it is there.
> 
> Most of Apache specifically tries to avoid any signals, although the
> parent still relies on SIGWINCH, SIGTERM, and SIGHUP.  And the children
> rely on SIGTERM and sometimes on SIGINT.

okay... so... what you are saying, effectively, is that apache is
vulnerable to a SIGPIPE DOS attack, amongst others.

for xvl, i think... i think what i will do is simply rip all of the
signal handling / fault / blocking etc. code out.  xvl doesn't
use apr_signal_thread() - it doesn't use threads [yet :)]

when this issue has been addressed [DOS attacks possible via
signals], i'll follow suit.

all best,

luke


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