[PATCH 4.9 08/60] mac80211/wpa: use constant time memory comparison for MACs

Greg Kroah-Hartman
2017-06-19T15:29:14Z

From: Jason A. Donenfeld <Jason@zx2c4.com>

commit 98c67d187db7808b1f3c95f2110dd4392d034182 upstream.

Otherwise, we enable all sorts of forgeries via timing attack.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-wireless@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/mac80211/wpa.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/net/mac80211/wpa.c
+++ b/net/mac80211/wpa.c
@@ -17,6 +17,7 @@
#include <asm/unaligned.h>
#include <net/mac80211.h>
#include <crypto/aes.h>
+#include <crypto/algapi.h>

#include "ieee80211_i.h"
#include "michael.h"
@@ -153,7 +154,7 @@ ieee80211_rx_h_michael_mic_verify(struct
data_len = skb->len - hdrlen - MICHAEL_MIC_LEN;
key = &rx->key->conf.key[NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY];
michael_mic(key, hdr, data, data_len, mic);
- if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0)
+ if (crypto_memneq(mic, data + data_len, MICHAEL_MIC_LEN))
goto mic_fail;

/* remove Michael MIC from payload */
@@ -1047,7 +1048,7 @@ ieee80211_crypto_aes_cmac_decrypt(struct
bip_aad(skb, aad);
ieee80211_aes_cmac(key->u.aes_cmac.tfm, aad,
skb->data + 24, skb->len - 24, mic);
- if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
+ if (crypto_memneq(mic, mmie->mic, sizeof(mmie->mic))) {
key->u.aes_cmac.icverrors++;
return RX_DROP_UNUSABLE;
}
@@ -1097,7 +1098,7 @@ ieee80211_crypto_aes_cmac_256_decrypt(st
bip_aad(skb, aad);
ieee80211_aes_cmac_256(key->u.aes_cmac.tfm, aad,
skb->data + 24, skb->len - 24, mic);
- if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
+ if (crypto_memneq(mic, mmie->mic, sizeof(mmie->mic))) {
key->u.aes_cmac.icverrors++;
return RX_DROP_UNUSABLE;
}
@@ -1201,7 +1202,7 @@ ieee80211_crypto_aes_gmac_decrypt(struct
if (ieee80211_aes_gmac(key->u.aes_gmac.tfm, aad, nonce,
skb->data + 24, skb->len - 24,
mic) < 0 ||
- memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
+ crypto_memneq(mic, mmie->mic, sizeof(mmie->mic))) {
key->u.aes_gmac.icverrors++;
return RX_DROP_UNUSABLE;
}