Following up on the CVE-2014-0160 vulnerability, heartbleed. We've created some iptables rules to block all heartbeat queries using the very powerful u32 module.

The rules allow you to mitigate systems that can't yet be patched by blocking ALL the heartbeat handshakes. We also like the capability to log external scanners :)

The rules have been specifically created for HTTPS traffic and may be adapted for other protocols; SMTPS/IMAPS/...

# Log rules
iptables -t filter -A INPUT  -p tcp --dport 443  -m u32 --u32 \ "52=0x18030000:0x1803FFFF" -j LOG --log-prefix "BLOCKED: HEARTBEAT"

# Block rules
iptables -t filter -A INPUT  -p tcp --dport 443  -m u32 --u32 \ "52=0x18030000:0x1803FFFF" -j DROP

# Wireshark rules
$ tshark  -i interface port 443 -R 'frame[68:1] == 18'
$ tshark  -i interface port 443 -R 'ssl.record.content_type == 24'

We believe that this should only be used as a temporary fix to decrease the exposure window. The log rule should allow you to test the firewall rules before being used in production. It goes without saying that if you have any suggested improvements to these rules we would be grateful if you could share them with the security community.

Clearly, use of these rules is at your own risk ;)

ECSC SOC Team Researchers:
Adam Shore
Alex Innes
Fabien Bourdaire