Arch Linux: 201708-13 Moderate StrongSwan DoS Fix Advisory

Arch Linux Security Advisory ASA-201708-13
=========================================
Severity: Low
Date    : 2017-08-14
CVE-ID  : CVE-2017-11185
Package : strongswan
Type    : denial of service
Remote  : Yes
Link    : https://security.archlinux.org/AVG-382

Summary
======
The package strongswan before version 5.5.3-4 is vulnerable to denial
of service.

Resolution
=========
Upgrade to 5.5.3-4.

# pacman -Syu "strongswan>=5.5.3-4"

The problem has been fixed upstream but no release is available yet.

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

Description
==========
Fixed a DoS vulnerability in the gmp plugin that was caused by
insufficient input validation when verifying RSA signatures, which
requires decryption with the operation m^e mod n, where m is the
signature, and e and n are the exponent and modulus of the public key.
The value m is an integer between 0 and n-1, however, the gmp plugin
did not verify this. So if m equals n the calculation results in 0, in
which case mpz_export() returns NULL. This result wasn't handled
properly causing a null-pointer dereference.

Impact
=====
The attacker is able to crash the application via a specially crafted
RSA signature.

References
=========
https://wiki.strongswan.org/versions/66
https://www.strongswan.org/blog/2017/08/14/strongswan-vulnerability-.html
https://security.archlinux.org/CVE-2017-11185