Wednesday, May 20, 2015

Fixing Logjam for Pound

The recently discovered problem "Logjam" in TLS (or the Diffie Hellman algorithm to be exact) is also present in pound by Apsis. Especially if you're using a pre-build binary via apt-get or rpm, as the DH parameters are built into the pound binary itself.

So, to block the support of DH Export, it is enough to change or specify a "Ciphers" setting:




However, to be absolutely on the safe side, I'd recommend to compile your own binary with 2048 bit long DH params (the default ones are "just" 1024 bit anyway).

Luckily the steps are quite simple and straight forward:
  1. wget
  2. tar -xzf Pound-2.7.tgz
  3. cd Pound-2.7
  4. ./configure --with-dh=2048 --prefix= --exec_prefix=/usr
  5. make
  6. make install
This will look for pound.cfg in /etc/pound.cfg (Debian uses /etc/pound/pound.cfg) and install pound in /usr/sbin - just like the Debian/Ubuntu package does - so you can keep / reuse their init.d script.

Also consider adding "Disable SSLv3" (just above Ciphers) to disable SSL3 which is considered insecure.

Using all this will give you a solid A- on