On 03/24/2018 03:29 AM, Alexander Wetzel wrote:
Rekeying a pairwise key with encryption offload and only keyid 0 has two
potential races which can freeze the wlan conection till rekeyed again:
1) For incomming packets:
If the local STA installs the key prior to the remote STA we still
have the old key active in the hardware for a short time after
mac80211 switched to the new key.
The card can still hand over packets decoded with the old key to
mac80211, bumping the new PN (IV) value to an incorrect high number and
tricking the local replay detection to drop all packets really sent
with the new key.
2) For outgoing packets:
If mac80211 is providing the PN (IV) and hands over the cleartext
packets for encryption to the hardware immediately prior to a key
change the driver/card may process the queued packets after
switching to the new key.
This will immediatelly bump the PN (IV) value on the remote STA to
an incorrect high number, also freezing the connection.
Both issues can be prevented by deleting the key from the hardware prior
to switching to the new key in mac80211, falling back to software
encryption/decryption till the switch to the new key is completed.
What will happen to drivers like ath10k that cannot do software encrypt/decrypt?
ath10k can support multiple key-ids as far as I can tell,
so maybe it would just never hit this code?
Thanks,
Ben
Signed-off-by: Alexander Wetzel <[email protected]>
---
net/mac80211/key.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/net/mac80211/key.c b/net/mac80211/key.c
index aee05ec3f7ea..266ea0b507e7 100644
--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -332,10 +332,15 @@ static void ieee80211_key_replace(struct
ieee80211_sub_if_data *sdata,
WARN_ON(new && old && new->conf.keyidx != old->conf.keyidx);
- if (old)
+ if (old) {
idx = old->conf.keyidx;
- else
+ /* Make sure the card can't encrypt/decrypt packets with
+ * the old key prior to switching to new key in mac80211.
+ */
+ ieee80211_key_disable_hw_accel(old);
+ } else {
idx = new->conf.keyidx;
+ }
if (sta) {
if (pairwise) {
--
Ben Greear <[email protected]>
Candela Technologies Inc http://www.candelatech.com
