diff options
| author | Jouni Malinen <j@w1.fi> | 2020-01-07 17:35:45 +0200 |
|---|---|---|
| committer | Johannes Berg <johannes.berg@intel.com> | 2020-01-15 09:52:12 +0100 |
| commit | 6f601265215a421f425ba3a4850a35861d024643 (patch) | |
| tree | 693a07fc329a7e24148574d5525e955647b82db6 /net/mac80211/tkip.c | |
| parent | 26ec17a1dc5ecdd8d91aba63ead6f8b5ad5dea0d (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/mac80211/tkip.c')
| -rw-r--r-- | net/mac80211/tkip.c | 18 |
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) { |