(Trustix Issues Fix) OpenSSL Uses Potentially Predictable Pseudo-Random Number Generator
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SecurityTracker Alert ID: 1001977 |
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SecurityTracker URL: http://securitytracker.com/id/1001977
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CVE Reference:
GENERIC-MAP-NOMATCH
(Links to External Site)
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Date: Jul 11 2001
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Impact:
Disclosure of authentication information
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Fix Available: Yes Vendor Confirmed: Yes
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Version(s): up to 0.9.6a
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Description:
OpenSSL announced a vulnerability in the cryptographic toolkit's pseudo-random number generator (PRNG) that could allow an attacker to predict future PRNG output.
The pseudo-random number generator (PRNG) in SSLeay/OpenSSL reportedly contains a design error that weakens the function such that it could become predictable.
The PRNG function (source code file crypto/md_rand.c) uses a hash function to update its internal secret state and to generate output. The secret state consists of two items: 1) a chaining variable message digest 'md' that is the output of the hash function, and 2) a large buffer variable 'state' that is is accessed circularly and used for storing additional entropy.
When generating output bytes, vulnerable versions of OpenSSL set the 'md' variable to the hash of one half of its previous value (which is also the same half that was used as PRNG output, meaning that it is not a secret value) and some other data, including bytes from 'state'. In addition, the number of bytes used from 'state' depended on the number of bytes requested as PRNG output and could be as small as one, making a brute-force analysis of all possible cases feasible.
These two design flaws make it possible to reconstruct the complete internal PRNG state from the output of one large PRNG request (large enough gain knowledge on the 'md' variable) followed by enough consecutive 1-byte PRNG requests to cycle through all of 'state'.
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Impact:
A user could potentially determine future PRNG output, which could lead to an attack of the system using the PRNG output.
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Solution:
The vendor has released a fix. See the Source Message for the vendor's advisory containing directions on how to obtain the appropriate fix.
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Vendor URL: www.openssl.org/ (Links to External Site)
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Cause:
Randomization error
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Underlying OS:
Linux (Trustix)
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Message History:
This archive entry is a follow-up to the message listed below.
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Source Message Contents
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Date: Wed, 11 Jul 2001 14:41:41 +0200
Subject: TSLSA-2001-0012 - OpenSSL
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
- --------------------------------------------------------------------------
Trustix Secure Linux Security Advisory #2001-0012
Package name: OpenSSL
Date: 2001-07-11
Affected versions: TSL 1.01, 1.1, 1.2
--------------------------------------------------------------------------
Problem description:
From the OpenSSL Advisory:
The pseudo-random number generator (PRNG) in SSLeay/OpenSSL versions
up to 0.9.6a is weakened by a design error. Knowing the output of
specific PRNG requests (including a number of consecutive very short
PRNG requests) would allow an attacker to determine the PRNG's
internal state and thus to predict future PRNG output.
Action:
We recommend that all systems with this package installed are upgraded.
Location:
All TSL updates are available from
<URI:http://www.trustix.net/pub/Trustix/updates/>
<URI:ftp://ftp.trustix.net/pub/Trustix/updates/>
Automatic updates:
Users of the SWUP tool, can enjoy having updates automatically
installed using 'swup --upgrade'.
Note that kernel packages are not normally fit to be upgraded this way
and therefore excluded in the default configuration.
Get SWUP from:
<URI:ftp://ftp.trustix.net/pub/Trustix/software/swup/>
Questions?
Check out our mailing lists:
<URI:http://www.trustix.net/support/>
Verification:
This advisory along with all TSL packages are signed with the TSL sign key.
This key available from:
<URI:http://www.trustix.net/TSL-GPG-KEY>
The advisory itself is available from the errata page at
<URI:http://www.trustix.net/errata/trustix-1.2/>
or directly at
<URI:http://www.trustix.net/errata/misc/2001/TSL-2001-0012-openssl.asc.txt>
MD5sums of the packages:
- --------------------------------------------------------------------------
caa5dc40088b00e9a77c4721939783b1 ./1.2/SRPMS/openssl-0.9.6-2tr.src.rpm
e2c6604fc4013abea33c23b6b9a7cbad ./1.2/RPMS/openssl-devel-0.9.6-2tr.i586.rpm
0a64aca805351c89eb87eb992c0005d1 ./1.2/RPMS/openssl-0.9.6-2tr.i586.rpm
6849562cfee9afa4d22ef6f599292fc3 ./1.1/SRPMS/openssl-0.9.5a-2tr.src.rpm
ec88b361720e40d6507b472ab397490a ./1.1/RPMS/openssl-devel-0.9.5a-2tr.i586.rpm
605b5b006f4b0c6d3894ee50fbffbb33 ./1.1/RPMS/openssl-0.9.5a-2tr.i586.rpm
- --------------------------------------------------------------------------
Trustix Security Team
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Comment: For info see http://www.gnupg.org
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