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Bug 455556 - dev-libs/openssl : TLS CBC padding timing attack
Summary: dev-libs/openssl : TLS CBC padding timing attack
Status: RESOLVED DUPLICATE of bug 455592
Alias: None
Product: Gentoo Security
Classification: Unclassified
Component: Vulnerabilities (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Gentoo Security
Depends on:
Reported: 2013-02-05 09:28 UTC by Agostino Sarubbo
Modified: 2013-02-06 00:20 UTC (History)
1 user (show)

See Also:
Package list:
Runtime testing required: ---


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Description Agostino Sarubbo gentoo-dev 2013-02-05 09:28:01 UTC
From $URL :

A flaw in how TLS/DTLS, when CBC-mode encryption is used, communicates was reported.  This 
vulnerability can allow for a Man-in-the-Middle attacker to recover plaintext from a TLS/DTLS 
connection, when CBC-mode encryption is used.

This flaw is in the TLS specification, and not a bug in a specific implementation (as such, it 
affects nearly all implementations).  As such, it affects all TLS and DTLS implementations that are 
compliant with TLS 1.1 or 1.2, or with DTLS 1.0 or 1.2.  It also applies to implementations of SSL 
3.0 and TLS 1.0 that incorporate countermeasures to deal with previous padding oracle attacks.  All 
TLS/DTLS ciphersuites that include CBC-mode encryption are potentially vulnerable.

The paper indicates that with OpenSSL, a full plaintext recovery attack is possible, and with 
GnuTLS, a partial plaintext recovery is possible (recovering up to 4 bits of the last byte in any 
block of plaintext).

To perform a successful attack, when TLS is used, a large number of TLS sessions are required 
(target plaintext must be sent repeatedly in the same position in the plaintext stream across the 
sessions).  For DTLS, a successful attack can be carried out in a single session.  The attacker 
must also be located close to the machine being attacked.

Further details are noted in the paper.

Current status of fixes in various implementations:

* OpenSSL has a patch in development
* NSS has a patch in development
* GnuTLS is fixed in versions 2.12.23, 3.0.28, and 3.1.7
* PolarSSL is fixed in version 1.2.5
* BouncyCastle has a patch that will be included in the forthcoming 1.48 version

External References:
Comment 1 Hanno Böck gentoo-dev 2013-02-06 00:20:02 UTC

*** This bug has been marked as a duplicate of bug 455592 ***