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drbd: Fix a hole in the challange-response connection authentication

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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>
This commit is contained in:
Philipp Reisner 2014-04-28 18:43:30 +02:00 • committed by Jens Axboe
parent f9c78128f8
commit 67cca286ca
1 changed files with 12 additions and 0 deletions

12
drivers/block/drbd/drbd_receiver.c
View file

@ -4846,6 +4846,12 @@ static int drbd_do_auth(struct drbd_connection *connection)
goto fail;
}
if (pi.size < CHALLENGE_LEN) {
drbd_err(connection, "AuthChallenge payload too small.\n");
rv = -1;
goto fail;
}
peers_ch = kmalloc(pi.size, GFP_NOIO);
if (peers_ch == NULL) {
drbd_err(connection, "kmalloc of peers_ch failed\n");
@ -4859,6 +4865,12 @@ static int drbd_do_auth(struct drbd_connection *connection)
goto fail;
}
if (!memcmp(my_challenge, peers_ch, CHALLENGE_LEN)) {
drbd_err(connection, "Peer presented the same challenge!\n");
rv = -1;
goto fail;
}
resp_size = crypto_hash_digestsize(connection->cram_hmac_tfm);
response = kmalloc(resp_size, GFP_NOIO);
if (response == NULL) {