On Monday 11 April 2011 15:39:33 Johannes Berg wrote:
> On Sat, 2011-04-09 at 12:34 +0200, Christian Lamparter wrote:
> > diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
> > index f1765de..a2c18b6 100644
> > --- a/net/mac80211/wpa.c
> > +++ b/net/mac80211/wpa.c
> > @@ -87,33 +87,35 @@ ieee80211_rx_h_michael_mic_verify(struct ieee80211_rx_data *rx)
> > struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
> > struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
> >
> > + if (!ieee80211_has_protected(hdr->frame_control) ||
> > + !ieee80211_is_data_present(hdr->frame_control)) {
> > + return RX_CONTINUE;
> > + }
>
> But is this check correct? What if the driver _completely_ pretends that the
> frame wasn't encrypted? Do we strictly require that it leaves the protected
> bit set?
OnT: It looks like this patch might also help to relieve ath9k & ath9k_htc of
some workarounds. see: 56363ddeeed "ath9k: fix spurious MIC failure reports".
(ath5k seems to be fine though?!)
BTW: what to do about this?
- if (rx->sdata->vif.type == NL80211_IFTYPE_AP && keyidx) {
- /*
- * APs with pairwise keys should never receive Michael MIC
- * errors for non-zero keyidx because these are reserved for
- * group keys and only the AP is sending real multicast
- * frames in the BSS.
- */
- return; [Drop Unusable]
- }
for now, I've kept the code. But I'm not quite sure why, at least
I couldn't find the passage in the spec that says "GTK MIC failures in AP mode
can be ignored" [Although, 8.5.1 (see "196 hole")& 8.3.2.3 (last sentence)
hint in this direction]?
Regards,
Christian
---
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index fc2ff78..a1bef0f 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2354,47 +2354,6 @@ ieee80211_rx_h_mgmt(struct ieee80211_rx_data *rx)
return RX_QUEUED;
}
-static void ieee80211_rx_michael_mic_report(struct ieee80211_hdr *hdr,
- struct ieee80211_rx_data *rx)
-{
- int keyidx;
- unsigned int hdrlen;
-
- hdrlen = ieee80211_hdrlen(hdr->frame_control);
- if (rx->skb->len >= hdrlen + 4)
- keyidx = rx->skb->data[hdrlen + 3] >> 6;
- else
- keyidx = -1;
-
- if (!rx->sta) {
- /*
- * Some hardware seem to generate incorrect Michael MIC
- * reports; ignore them to avoid triggering countermeasures.
- */
- return;
- }
-
- if (!ieee80211_has_protected(hdr->frame_control))
- return;
-
- if (rx->sdata->vif.type == NL80211_IFTYPE_AP && keyidx) {
- /*
- * APs with pairwise keys should never receive Michael MIC
- * errors for non-zero keyidx because these are reserved for
- * group keys and only the AP is sending real multicast
- * frames in the BSS.
- */
- return;
- }
-
- if (!ieee80211_is_data(hdr->frame_control) &&
- !ieee80211_is_auth(hdr->frame_control))
- return;
-
- mac80211_ev_michael_mic_failure(rx->sdata, keyidx, hdr, NULL,
- GFP_ATOMIC);
-}
-
/* TODO: use IEEE80211_RX_FRAGMENTED */
static void ieee80211_rx_cooked_monitor(struct ieee80211_rx_data *rx,
struct ieee80211_rate *rate)
@@ -2738,12 +2697,6 @@ static bool ieee80211_prepare_and_rx_handle(struct ieee80211_rx_data *rx,
if (!prepares)
return false;
- if (status->flag & RX_FLAG_MMIC_ERROR) {
- if (status->rx_flags & IEEE80211_RX_RA_MATCH)
- ieee80211_rx_michael_mic_report(hdr, rx);
- return false;
- }
-
if (!consume) {
skb = skb_copy(skb, GFP_ATOMIC);
if (!skb) {
diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
index f1765de..9dc3b5f 100644
--- a/net/mac80211/wpa.c
+++ b/net/mac80211/wpa.c
@@ -87,42 +87,76 @@ ieee80211_rx_h_michael_mic_verify(struct ieee80211_rx_data *rx)
struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
- /* No way to verify the MIC if the hardware stripped it */
- if (status->flag & RX_FLAG_MMIC_STRIPPED)
+ /*
+ * it makes no sense to check for MIC errors on anything other
+ * than data frames.
+ */
+ if (!ieee80211_is_data_present(hdr->frame_control))
+ return RX_CONTINUE;
+
+ /*
+ * No way to verify the MIC if the hardware stripped it or
+ * the IV with the key index. In this case we have solely rely
+ * on the driver to set RX_FLAG_MMIC_ERROR in the event of a
+ * MIC failure report.
+ */
+ if (status->flag & (RX_FLAG_MMIC_STRIPPED | RX_FLAG_IV_STRIPPED)) {
+ if (status->flag & RX_FLAG_MMIC_ERROR)
+ goto mic_fail;
+
+ if (!(status->flag & RX_FLAG_IV_STRIPPED))
+ goto update_iv;
+
return RX_CONTINUE;
+ }
+ /*
+ * Some hardware seems to generate Michael MIC failure reports; even
+ * though, the frame was not encrypted with TKIP and therefore has no
+ * MIC. Ignore the flag them to avoid triggering countermeasures.
+ */
if (!rx->key || rx->key->conf.cipher != WLAN_CIPHER_SUITE_TKIP ||
- !ieee80211_has_protected(hdr->frame_control) ||
- !ieee80211_is_data_present(hdr->frame_control))
+ !(status->flag & RX_FLAG_DECRYPTED))
return RX_CONTINUE;
+ if (rx->sdata->vif.type == NL80211_IFTYPE_AP && rx->key->conf.keyidx) {
+ /*
+ * APs with pairwise keys should never receive Michael MIC
+ * errors for non-zero keyidx because these are reserved for
+ * group keys and only the AP is sending real multicast
+ * frames in the BSS. (
+ */
+ return RX_DROP_UNUSABLE;
+ }
+
+ if (status->flag & RX_FLAG_MMIC_ERROR)
+ goto mic_fail;
+
hdrlen = ieee80211_hdrlen(hdr->frame_control);
if (skb->len < hdrlen + MICHAEL_MIC_LEN)
return RX_DROP_UNUSABLE;
data = skb->data + hdrlen;
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 (!(status->rx_flags & IEEE80211_RX_RA_MATCH))
- return RX_DROP_UNUSABLE;
-
- mac80211_ev_michael_mic_failure(rx->sdata, rx->key->conf.keyidx,
- (void *) skb->data, NULL,
- GFP_ATOMIC);
- return RX_DROP_UNUSABLE;
- }
+ if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0)
+ goto mic_fail;
/* remove Michael MIC from payload */
skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
+update_iv:
/* update IV in key information to be able to detect replays */
rx->key->u.tkip.rx[rx->queue].iv32 = rx->tkip_iv32;
rx->key->u.tkip.rx[rx->queue].iv16 = rx->tkip_iv16;
return RX_CONTINUE;
+
+mic_fail:
+ mac80211_ev_michael_mic_failure(rx->sdata, rx->key->conf.keyidx,
+ (void *) skb->data, NULL, GFP_ATOMIC);
+ return RX_DROP_UNUSABLE;
}
--
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