[PATCH 6/6] mac80211/wpa: use constant time memory comparison for MACs

[Jason A. Donenfeld]

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

Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com>
Cc: Johannes Berg <johan...@sipsolutions.net>
Cc: linux-wirel...@vger.kernel.org
Cc: sta...@vger.kernel.org
---
 net/mac80211/wpa.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
index c1ef22df865f..cc19614ff4e6 100644
--- 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 ieee80211_rx_data 
*rx)
        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 */
@@ -1048,7 +1049,7 @@ ieee80211_crypto_aes_cmac_decrypt(struct 
ieee80211_rx_data *rx)
                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;
                }
@@ -1098,7 +1099,7 @@ ieee80211_crypto_aes_cmac_256_decrypt(struct 
ieee80211_rx_data *rx)
                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;
                }
@@ -1202,7 +1203,7 @@ ieee80211_crypto_aes_gmac_decrypt(struct 
ieee80211_rx_data *rx)
                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;
                }
-- 
2.13.1