Bug 84597 - OpenSSL CBC timing attack
OpenSSL CBC timing attack
Product: Red Hat Enterprise Linux 2.1
Classification: Red Hat
Component: openssl (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Nalin Dahyabhai
Brian Brock
: Security
Depends On:
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Reported: 2003-02-19 08:25 EST by Mark J. Cox (Product Security)
Modified: 2007-11-30 17:06 EST (History)
3 users (show)

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Doc Type: Bug Fix
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Last Closed: 2003-04-15 07:26:42 EDT
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Description Mark J. Cox (Product Security) 2003-02-19 08:25:42 EST
In an upcoming paper, Brice Canvel, Alain Hiltgen, Serge Vaudenay, and
Martin Vuagnoux describe and demonstrate a timing-based attack on CBC
ciphersuites in SSL and TLS. An active attacker may be able to use timing
observations to distinguish between two different error cases: cipher
padding errors and MAC verification errors. Over multiple connections this
can leak sufficient information to make it possible to retrieve the
plaintext of a common, fixed block.

In order for an attack to be sucessful, an attacker must be able to act as
a man-in-the-middle to intercept and modify multiple connections, which all
involve a common fixed plaintext block (such as a password), and have good
network conditions that allow small changes in timing to be reliably observed.

A patch is available from the OpenSSL project
Comment 1 Rich Graves 2003-02-19 22:51:26 EST
I know you're going to want to backport the fix, but please please please
consider biting the bullet and figuring out how to just get to 0.9.6i. There
have been ***lots*** of not-as-security-critical bugs fixed between b and i. The
one biting me today is that the very cool http://www.washington.edu/pubcookie/
simply will not work on any RedHat system.
Comment 2 Greg Pyhl 2003-03-05 06:48:00 EST
Could someone please provide some status update here? Other distributors have
released their updated openssl packages weeks ago. Is RHL vulnerable and if so,
when is the patch coming? Thanks.
Comment 3 Mark J. Cox (Product Security) 2003-03-05 06:56:47 EST
We wanted to make sure that a fix for the critical sendmail vulnerability
would be available on Monday so we adjusted the priority of the OpenSSL errata
accordingly.  We are working on updated OpenSSL packages and will make them
available shortly.
Comment 4 Mark J. Cox (Product Security) 2003-03-06 10:15:28 EST
Updated OpenSSL packages for Red Hat Linux are now available

Leaving this bug open until packages for Red Hat Linux Advanced Server are also
Comment 5 Mark J. Cox (Product Security) 2003-04-15 07:26:42 EDT
Was actually fixed some time ago, see latest OpenSSL advisory

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