mac80211: prevent mixed key and fragment cache attacks

commit 94034c40ab4a3fcf581fbc7f8fdf4e29943c4a24 upstream.

Simultaneously prevent mixed key attacks (CVE-2020-24587) and fragment
cache attacks (CVE-2020-24586). This is accomplished by assigning a
unique color to every key (per interface) and using this to track which
key was used to decrypt a fragment. When reassembling frames, it is
now checked whether all fragments were decrypted using the same key.

To assure that fragment cache attacks are also prevented, the ID that is
assigned to keys is unique even over (re)associations and (re)connects.
This means fragments separated by a (re)association or (re)connect will
not be reassembled. Because mac80211 now also prevents the reassembly of
mixed encrypted and plaintext fragments, all cache attacks are prevented.

Cc: stable@vger.kernel.org
Signed-off-by: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Link: https://lore.kernel.org/r/20210511200110.3f8290e59823.I622a67769ed39257327a362cfc09c812320eb979@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 1046520d726d89730d0aadb14f4b55f392dfec1d..16510a57f2e7f161d6912a21daba74c1e3b2da1c 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -94,6 +94,7 @@ struct ieee80211_fragment_entry {
        u8 rx_queue;
        bool check_sequential_pn; /* needed for CCMP/GCMP */
        u8 last_pn[6]; /* PN of the last fragment if CCMP was used */
+       unsigned int key_color;
 };
 
 

diff --git a/net/mac80211/key.c b/net/mac80211/key.c
index 91a4e606edcdb4337898bc6fe2a277108be32edf..a2050d5776cecbd0dc64dc88eb596f102e465980 100644 (file)
--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -646,6 +646,7 @@ int ieee80211_key_link(struct ieee80211_key *key,
                       struct sta_info *sta)
 {
        struct ieee80211_local *local = sdata->local;
+       static atomic_t key_color = ATOMIC_INIT(0);
        struct ieee80211_key *old_key;
        int idx = key->conf.keyidx;
        bool pairwise = key->conf.flags & IEEE80211_KEY_FLAG_PAIRWISE;
@@ -680,6 +681,12 @@ int ieee80211_key_link(struct ieee80211_key *key,
        key->sdata = sdata;
        key->sta = sta;
 
+       /*
+        * Assign a unique ID to every key so we can easily prevent mixed
+        * key and fragment cache attacks.
+        */
+       key->color = atomic_inc_return(&key_color);
+
        increment_tailroom_need_count(sdata);
 
        ieee80211_key_replace(sdata, sta, pairwise, old_key, key);

diff --git a/net/mac80211/key.h b/net/mac80211/key.h
index 9951ef06323e743d2c33156d15e5a21478584cd9..9ac5c00dbe80d7bde7451bc8331fce268175c0dd 100644 (file)
--- a/net/mac80211/key.h
+++ b/net/mac80211/key.h
@@ -123,6 +123,8 @@ struct ieee80211_key {
        } debugfs;
 #endif
 
+       unsigned int color;
+
        /*
         * key config, must be last because it contains key
         * material as variable length member

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index eaad526cd0bfbe2747bb8d5df24144c5ed0842ae..85d7ac83d8477e95bc847ef953c3b5af7bbd5990 100644 (file)
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1869,6 +1869,7 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
                         * next fragment has a sequential PN value.
                         */
                        entry->check_sequential_pn = true;
+                       entry->key_color = rx->key->color;
                        memcpy(entry->last_pn,
                               rx->key->u.ccmp.rx_pn[queue],
                               IEEE80211_CCMP_PN_LEN);
@@ -1906,6 +1907,11 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 
                if (!requires_sequential_pn(rx, fc))
                        return RX_DROP_UNUSABLE;
+
+               /* Prevent mixed key and fragment cache attacks */
+               if (entry->key_color != rx->key->color)
+                       return RX_DROP_UNUSABLE;
+
                memcpy(pn, entry->last_pn, IEEE80211_CCMP_PN_LEN);
                for (i = IEEE80211_CCMP_PN_LEN - 1; i >= 0; i--) {
                        pn[i]++;