[ASA-201804-6] lib32-openssl: private key recovery

[Remi Gacogne]

Arch Linux Security Advisory ASA-201804-6
=========================================

Severity: Medium
Date    : 2018-04-15
CVE-ID  : CVE-2017-3738
Package : lib32-openssl
Type    : private key recovery
Remote  : Yes
Link    : https://security.archlinux.org/AVG-551

Summary
=======

The package lib32-openssl before version 1:1.1.0.h-1 is vulnerable to
private key recovery.

Resolution
==========

Upgrade to 1:1.1.0.h-1.

# pacman -Syu "lib32-openssl>=1:1.1.0.h-1"

The problem has been fixed upstream in version 1.1.0.h.

Workaround
==========

None.

Description
===========

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.

Impact
======

A remote attacker might be able to recover a private key (in very
unlikely cases).

References
==========

https://www.openssl.org/news/vulnerabilities.html#2017-3738
https://www.openssl.org/news/secadv/20171207.txt
https://github.com/openssl/openssl/commit/5630661aecbea5fe3c4740f5fea744a1f07a6253
https://security.archlinux.org/CVE-2017-3738

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