Suricata IDS – IPv4 evasion

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Suricata IDS – IPv4 evasion


From: Jérémy BEAUME <jeremy.beaume () protonmail com>

Date: Wed, 15 Feb 2017 16:59:05 -0500


Here are the details of the (patched) IPv4 evasion I found in Suricata IDS/IPS:

# Software
Suricata IDS/IPS
website : https://suricata-ids.org/
editor : Open Information Security Foundation (OISF) https://oisf.net/

# Impacted version

3.2.x before 3.2.13.13
3.1.3 and before

All execution mode are impacted : nfqueue, af-packet, ...

# Vulnerability description

Suricata did not used the IP protocol field value to identify
fragments from a same packet, whereas the RFC 791 states that 2
fragments should be defragmented together only if the protocol
field have the same value.
This flaw makes it possible to craft a packet that will only
be defragmented by Suricata (and not the destination host), leading to
a packet injection in the IDS detection engine.

# Impact on security

An attacker can fully evade any TCP signature, without any logs / alerts.

# Resources and links :

New patched Suricata versions :
https://suricata-ids.org/2017/02/15/suricata-3-2-1-available/
https://suricata-ids.org/2017/02/15/suricata-3-2-1-available/

Bug tracker and patch commit :
https://redmine.openinfosecfoundation.org/issues/2019
https://github.com/inliniac/suricata/commit/4a04f814b15762eb446a5ead4d69d021512df6f8

# Thanks and note

I'd like to give a special thanks to the suricata development team and
especially Victor Julien : I contacted him concerning the issue, got an answer
the same day, and it was corrected on github 2 working days after.
Really impressive guys.

If anyone needs more information about this, feel free to contact me at
jeremy [dot] beaume (a) protonmail [dot] com

Cheers !
Jeremy BEAUME

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