Bug 640210 (CVE-2017-3738)

Summary:	[TRACKER] rsaz_1024_mul_avx2 overflow bug on x86_64 (CVE-2017-3738)
Product:	Gentoo Security	Reporter:	Thomas Deutschmann (RETIRED) <whissi>
Component:	Vulnerabilities	Assignee:	Gentoo Security <security>
Status:	RESOLVED FIXED
Severity:	normal	Keywords:	Tracker
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
URL:	https://mta.openssl.org/pipermail/openssl-announce/2017-December/000110.html
Whiteboard:
Package list:		Runtime testing required:	---
Bug Depends on:	640172, 640212
Bug Blocks:

Description Thomas Deutschmann (RETIRED) gentoo-dev

2017-12-07 18:23:25 UTC

rsaz_1024_mul_avx2 overflow bug on x86_64 (CVE-2017-3738)
=========================================================

Severity: Low

There is an overflow bug in the AVX2 Montgomery multiplication procedure
used in exponentiation with 1024-bit moduli. No EC algorithms are affected.
Analysis suggests that attacks against RSA and DSA as a result of this defect
would be very difficult to perform and are not believed likely. Attacks
against DH1024 are considered just feasible, because most of the work
necessary to deduce information about a private key may be performed offline.
The amount of resources required for such an attack would be significant.
However, for an attack on TLS to be meaningful, the server would have to share
the DH1024 private key among multiple clients, which is no longer an option
since CVE-2016-0701.

This only affects processors that support the AVX2 but not ADX extensions
like Intel Haswell (4th generation).

Note: The impact from this issue is similar to CVE-2017-3736, CVE-2017-3732
and CVE-2015-3193.

Due to the low severity of this issue we are not issuing a new release of
OpenSSL 1.1.0 at this time. The fix will be included in OpenSSL 1.1.0h when it
becomes available. The fix is also available in commit e502cc86d in the OpenSSL
git repository.

OpenSSL 1.0.2 users should upgrade to 1.0.2n

This issue was reported to OpenSSL on 22nd November 2017 by David Benjamin
(Google). The issue was originally found via the OSS-Fuzz project. The fix was
developed by Andy Polyakov of the OpenSSL development team.

Comment 1 Christopher Díaz Riveros (RETIRED) gentoo-dev

2018-01-08 16:11:28 UTC

This issue was resolved and addressed in
 GLSA 201712-03 at https://security.gentoo.org/glsa/201712-03
by GLSA coordinator Thomas Deutschmann (whissi).