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		 NetBSD Security Advisory 2009-012

		 =================================
Topic:		SHA2 implementation potential buffer overflow
Version:	NetBSD-current:		affected prior to 2009-05-26

		NetBSD 5.0:		affected

		NetBSD 4.0.*:		affected

		NetBSD 4.0:		affected
Severity:	Denial of Service
Fixed:		NetBSD-current:		May 26, 2009

		NetBSD-5-0 branch:	Jul 11, 2009

		NetBSD-5 branch:	Jul 11, 2009

		NetBSD-4-0 branch:	Jul 22, 2009

		NetBSD-4 branch:	Jul 22, 2009
Please note that NetBSD releases prior to 4.0 are no longer supported.

It is recommended that all users upgrade to a supported release.
Abstract

========
An error initializing a SHA2 context causes vulnerable applications using

libcrypto to suffer from a 4- or 8-byte buffer overflow (for SHA256 and

SHA512 correspondingly) with fixed content, potentially causing

applications to crash.
Technical Details

=================
A program using the SHA2 implementation from sys/sha2.h in NetBSD and

linking against libcrypto is vulnerable to a 4- or 8-byte buffer

overflow (for SHA256 and SHA512 correspondingly) with fixed content.
The overflow occurs at the time the hash init function is called (e.g.

SHA256_Init). The init functions then pass the wrong size for the

context as an argument to the memset function which then overwrites

4 bytes of the memory buffer located after the one holding the context.
In the NetBSD base system, this affects the libssh library as well as

the pkg_install framework. In libssh, the overflow occurs on the heap

of the program using it, in pkg_install a stack overflow occurs.
Solutions and Workarounds

=========================
A workaround for this issue for programs in the NetBSD base system

is to disable SHA256 as a HMAC for the secure shell and to avoid

using the audit facility as well as signed packages.
To determine whether or not a package is signed, run the command
	% tar tzf package.tgz
on the package. If the first file of the package is +PKG_HASH,

then the package is signed.
The following instructions describe how to upgrade your libcrypto

and libc binaries by updating your source tree and rebuilding and

installing a new version of the three facilities.
* NetBSD-current:
	Systems running NetBSD-current dated from before 2009-05-26

	should be upgraded to NetBSD-current dated 2009-05-27 or later.
	The following files/directories need to be updated from the

	netbsd-current CVS branch (aka HEAD):

		common/lib/libc/hash/sha2

		distrib/sets/lists

		lib/libc

		lib/libcrypto

		sys/sys
	To update from CVS, re-build, and re-install lorem:

		# cd src

		# cvs update -d -P common/lib/libc/hash/sha2

		# cvs update -d -P distrib/sets/lists

		# cvs update -d -P lib/libc

		# cvs update -d -P lib/libcrypto

		# cvs update -d -P sys/sys

		# cd sys/sys

		# make USETOOLS=no cleandir

		# make USETOOLS=no includes

		# cd ../../lib/libc

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install

		# cd ../libcrypt

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install

		# cd ../libcrypto

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install
* NetBSD 5.*:
	Systems running NetBSD 5.* sources dated from before

	2009-07-11 should be upgraded from NetBSD 5.* sources dated

	2009-07-12 or later.
	The following files/directories need to be updated from the

	netbsd-5 or netbsd-5-0 branches:

		common/lib/libc/hash/sha2

		distrib/sets/lists

		lib/libc

		lib/libcrypto

		sys/sys
	To update from CVS, re-build, and re-install libc and libcrypto:
		# cd src

		# cvs update -r  -d -P common/lib/libc/hash/sha2

		# cvs update -r  -d -P distrib/sets/lists

		# cvs update -r  -d -P lib/libc

		# cvs update -r  -d -P lib/libcrypto

		# cvs update -r  -d -P sys/sys

		# cd sys/sys

		# make USETOOLS=no cleandir

		# make USETOOLS=no includes

		# cd ../../lib/libc

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install

		# cd ../libcrypt

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install

		# cd ../libcrypto

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install
* NetBSD 4.*:
	Systems running NetBSD 4.* sources dated from before

	2009-07-22 should be upgraded from NetBSD 4.* sources dated

	2009-07-23 or later.
	The following files/directories need to be updated from the

	netbsd-4 or netbsd-4-0 branches:

		common/lib/libc/hash/sha2

		distrib/sets/lists

		lib/libc

		lib/libcrypto

		sys/sys
	To update from CVS, re-build, and re-install libc and libcrypto:
		# cd src

		# cvs update -r  -d -P common/lib/libc/hash/sha2

		# cvs update -r  -d -P distrib/sets/lists

		# cvs update -r  -d -P lib/libc

		# cvs update -r  -d -P lib/libcrypto

		# cvs update -r  -d -P sys/sys

		# cd sys/sys

		# make USETOOLS=no cleandir

		# make USETOOLS=no includes

		# cd ../../lib/libc

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install

		# cd ../libcrypt

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install

		# cd ../libcrypto

		# make USETOOLS=no cleandir dependall

		# make USETOOLS=no install
Thanks To

=========
Joerg Sonnenberger for finding, reporting and fixing the issue.
Revision History

================
	2009-07-28	Initial release
More Information

================
Advisories may be updated as new information becomes available.

The most recent version of this advisory (PGP signed) can be found at

  http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2009-012.t...
Information about NetBSD and NetBSD security can be found at

http://www.NetBSD.org/ and http://www.NetBSD.org/Security/.
Copyright 2009, The NetBSD Foundation, Inc.  All Rights Reserved.

Redistribution permitted only in full, unmodified form.
$NetBSD: NetBSD-SA2009-012.txt,v 1.1 2009/07/28 18:29:29 tonnerre Exp $
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