From 67cca286caa6e33f3134bd36834d2484538f4f78 Mon Sep 17 00:00:00 2001
From: Philipp Reisner <philipp.reisner@linbit.com>
Date: Mon, 28 Apr 2014 18:43:30 +0200
Subject: [PATCH] drbd: Fix a hole in the challange-response connection
 authentication

In the implementation as it was, the two peers sent each other
a challenge, and expects the challenge hashed with the shared
secret back.

A attacker could simply wait for the challenge of the peer, and
send the same challenge back. Then it waits for the response, and
sends the same response back.

Prevent this by not accepting a challenge from the peer that is
the same as the challenge sent to the peer.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
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