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authorJouni Malinen <j@w1.fi>2020-01-07 17:35:45 +0200
committerJohannes Berg <johannes.berg@intel.com>2020-01-15 09:52:12 +0100
commit6f601265215a421f425ba3a4850a35861d024643 (patch)
tree693a07fc329a7e24148574d5525e955647b82db6 /net
parent26ec17a1dc5ecdd8d91aba63ead6f8b5ad5dea0d (diff)
mac80211: Fix TKIP replay protection immediately after key setup
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>
Diffstat (limited to 'net')
-rw-r--r--net/mac80211/tkip.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/net/mac80211/tkip.c b/net/mac80211/tkip.c
index 727dc9f3f3b3..e7f57bb18f6e 100644
--- a/net/mac80211/tkip.c
+++ b/net/mac80211/tkip.c
@@ -263,9 +263,21 @@ int ieee80211_tkip_decrypt_data(struct arc4_ctx *ctx,
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) {

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