Bug 455556

Summary:	dev-libs/openssl : TLS CBC padding timing attack
Product:	Gentoo Security	Reporter:	Agostino Sarubbo <ago>
Component:	Vulnerabilities	Assignee:	Gentoo Security <security>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	base-system
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
URL:	https://bugzilla.redhat.com/show_bug.cgi?id=907589
Whiteboard:
Package list:		Runtime testing required:	---

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:

http://www.isg.rhul.ac.uk/tls/
http://www.isg.rhul.ac.uk/tls/TLStiming.pdf
http://www.gnutls.org/security.html#GNUTLS-SA-2013-1
https://polarssl.org/tech-updates/releases/polarssl-1.2.5-released

Comment 1 Hanno Böck gentoo-dev

2013-02-06 00:20:02 UTC


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