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From: Mike Silbersack <silby@FreeBSD.org>
Date: Sun, 23 Feb 2003 11:04:58 -0800 (PST)
To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org,
	cvs-all@FreeBSD.org
Subject: cvs commit: src/sys/netinet tcp_syncache.c
X-FreeBSD-CVS-Branch: RELENG_4
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silby       2003/02/23 11:04:58 PST

  Modified files:        (Branch: RELENG_4)
    sys/netinet          tcp_syncache.c 
  Log:
  Improve the security and performance of syncookies:
  
  Security improvements:
  - Increase the size of each syncookie secret from 32 to 128 bits
    in order to make brute force attacks on the secrets much more
    difficult.
  - Always return the lowest order dword from the MD5 hash; this
    allows us to expose 2 more bits of the cookie and makes ACK
    floods which seek to guess the cookie value more difficult.
  
  Performance improvements:
  - Increase the lifetime of each syncookie from 4 seconds to 16
    seconds.  This increases the usefulness of syncookies during
    an attack.
  - From Yahoo!: Reduce the number of calls to MD5Update; this
    results in a ~17% increase in cookie generation time here.
  
  Reviewed by:    hsu, jayanth, jlemon, nectar
  
  Revision  Changes    Path
  1.5.2.13  +47 -26    src/sys/netinet/tcp_syncache.c

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