From 0ddbda1f829a2d1b27d7e6519900201111702823 Mon Sep 17 00:00:00 2001
From: Ivan Nardi <12729895+IvanNardi@users.noreply.github.com>
Date: Mon, 16 Sep 2024 18:38:26 +0200
Subject: Add an heuristic to detect encrypted/obfuscated OpenVPN flows (#2547)

Based on the paper: "OpenVPN is Open to VPN Fingerprinting"
See: https://www.usenix.org/conference/usenixsecurity22/presentation/xue-diwen

Basic idea:
* the distribution of the first byte of the messages (i.e. the distribution
of the op-codes) is quite unique
* this fingerprint might be still detectable even if the OpenVPN packets are
somehow fully encrypted/obfuscated

The heuristic is disabled by default.
---
 tests/cfgs/openvpn_heuristic_enabled/config.txt | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 tests/cfgs/openvpn_heuristic_enabled/config.txt

(limited to 'tests/cfgs/openvpn_heuristic_enabled/config.txt')

diff --git a/tests/cfgs/openvpn_heuristic_enabled/config.txt b/tests/cfgs/openvpn_heuristic_enabled/config.txt
new file mode 100644
index 000000000..81203be0f
--- /dev/null
+++ b/tests/cfgs/openvpn_heuristic_enabled/config.txt
@@ -0,0 +1 @@
+--cfg=openvpn,dpi.heuristics,0x01 --cfg=packets_limit_per_flow,64
-- 
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