Arch Linux: 201707-1 High: Libgcrypt Private Key Recovery Advisory

Arch Linux Security Advisory ASA-201707-1
========================================
Severity: High
Date    : 2017-07-03
CVE-ID  : CVE-2017-7526
Package : libgcrypt
Type    : private key recovery
Remote  : No
Link    : https://security.archlinux.org/AVG-338

Summary
======
The package libgcrypt before version 1.7.8-1 is vulnerable to private
key recovery.

Resolution
=========
Upgrade to 1.7.8-1.

# pacman -Syu "libgcrypt>=1.7.8-1"

The problem has been fixed upstream in version 1.7.8.

Workaround
=========
None.

Description
==========
The pattern of squarings and multiplications in left-to-right sliding
windows in libgcrypt <= 1.7.7 leaks significant information about
exponent bits, allowing for the very efficient recovery of a full
1024-bit RSA key.

Impact
=====
A local attacker can use a side-channel attack to recover a secret
private key.

References
=========
https://eprint.iacr.org/2017/627
https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commitdiff;h=a9f612def801c8145d551d995475e5d51a4c988c;hp=0e6788517eac6f508fa32ec5d5c1cada7fb980bc
https://security.archlinux.org/CVE-2017-7526