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Bugtraq Archives: socket buffer DoS/administrative limits (fwd)

socket buffer DoS/administrative limits (fwd)


Brian F. Feldman (greenFREEBSD.ORG)
Fri, 17 Sep 1999 12:35:50 -0400


---------- Forwarded message ----------
Date: Fri, 17 Sep 1999 12:32:01 -0400 (EDT)
From: Brian F. Feldman <greenFreeBSD.ORG>
To: hackersFreeBSD.ORG
Subject: socket buffer DoS/administrative limits

   Yes folks, it's that time again: time for more administrative limits!
I've worked out a resource limit (for FreeBSD in this case, but not
non-portable) which allows prevention of DoS by mbuf starvation. Others
are working on making the networking code more resilient, while this is
a general resource limit which can be used in any case.
   I've chosen the name "sbsize" (RLIMIT_SBSIZE) for this. Here's what
happens with the limit in action (note that the pdksh in use has been
patched to include the ulimit):

{"/home/green"}$ ulimit -b 2000000 ; ulimit -a | grep sbsize
sbsize(bytes) 2000000
{"/home/green"}$ ./testsockbuf
socketpair: No buffer space available
14 sockets had been allocated

   And another DoS attempt has been foiled with administrative limits :)
I'm sorry for not having something working sooner, but I ran into the problem
of my KASSERT() being tripped, which ended up being caused by me not
grokking an evil local define (look for "#define (snd|rcv) "...) correctly.
After fixing that, everything is wonderful.
   The patch, which applies to FreeBSD 4.0-CURRENT, and should be easily
portable or backportable, can be found at:

                http://www.FreeBSD.org/~green/sbsize4.patch

--
 Brian Fundakowski Feldman           \  FreeBSD: The Power to Serve!  /
 greenFreeBSD.org                    `------------------------------'

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This archive was generated by hypermail 2.0b3 on Fri Sep 17 1999 - 17:04:56 CDT