blob: cc280cb33656af2e8b73c2cb41964655ac94c9fc [file] [log] [blame]
From 62506e0346de0976ecb5bfedfb340ac2e6b73de8 Mon Sep 17 00:00:00 2001
From: Jouni Malinen <j@w1.fi>
Date: Tue, 7 Jan 2020 17:35:45 +0200
Subject: [PATCH] mac80211: Fix TKIP replay protection immediately after key
setup
commit 6f601265215a421f425ba3a4850a35861d024643 upstream.
TKIP replay protection was skipped for the very first frame received
after a new key is configured. While this is potentially needed to avoid
dropping a frame in some cases, this does leave a window for replay
attacks with group-addressed frames at the station side. Any earlier
frame sent by the AP using the same key would be accepted as a valid
frame and the internal RSC would then be updated to the TSC from that
frame. This would allow multiple previously transmitted group-addressed
frames to be replayed until the next valid new group-addressed frame
from the AP is received by the station.
Fix this by limiting the no-replay-protection exception to apply only
for the case where TSC=0, i.e., when this is for the very first frame
protected using the new key, and the local RSC had not been set to a
higher value when configuring the key (which may happen with GTK).
Signed-off-by: Jouni Malinen <j@w1.fi>
Link: https://lore.kernel.org/r/20200107153545.10934-1-j@w1.fi
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/net/mac80211/tkip.c b/net/mac80211/tkip.c
index 7914b8e3ce8c..2e7bd8b9f43c 100644
--- a/net/mac80211/tkip.c
+++ b/net/mac80211/tkip.c
@@ -263,9 +263,21 @@ int ieee80211_tkip_decrypt_data(struct crypto_cipher *tfm,
if ((keyid >> 6) != key->conf.keyidx)
return TKIP_DECRYPT_INVALID_KEYIDX;
- if (rx_ctx->ctx.state != TKIP_STATE_NOT_INIT &&
- (iv32 < rx_ctx->iv32 ||
- (iv32 == rx_ctx->iv32 && iv16 <= rx_ctx->iv16)))
+ /* Reject replays if the received TSC is smaller than or equal to the
+ * last received value in a valid message, but with an exception for
+ * the case where a new key has been set and no valid frame using that
+ * key has yet received and the local RSC was initialized to 0. This
+ * exception allows the very first frame sent by the transmitter to be
+ * accepted even if that transmitter were to use TSC 0 (IEEE 802.11
+ * described TSC to be initialized to 1 whenever a new key is taken into
+ * use).
+ */
+ if (iv32 < rx_ctx->iv32 ||
+ (iv32 == rx_ctx->iv32 &&
+ (iv16 < rx_ctx->iv16 ||
+ (iv16 == rx_ctx->iv16 &&
+ (rx_ctx->iv32 || rx_ctx->iv16 ||
+ rx_ctx->ctx.state != TKIP_STATE_NOT_INIT)))))
return TKIP_DECRYPT_REPLAY;
if (only_iv) {
--
2.7.4