package/kernel/mac80211/patches/subsys/380-mac80211-assure-all-fragments-are-encrypted.patch

   1 From: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
   2 Date: Tue, 11 May 2021 20:02:42 +0200
   3 Subject: [PATCH] mac80211: assure all fragments are encrypted
   4
   5 Do not mix plaintext and encrypted fragments in protected Wi-Fi
   6 networks. This fixes CVE-2020-26147.
   7
   8 Previously, an attacker was able to first forward a legitimate encrypted
   9 fragment towards a victim, followed by a plaintext fragment. The
  10 encrypted and plaintext fragment would then be reassembled. For further
  11 details see Section 6.3 and Appendix D in the paper "Fragment and Forge:
  12 Breaking Wi-Fi Through Frame Aggregation and Fragmentation".
  13
  14 Because of this change there are now two equivalent conditions in the
  15 code to determine if a received fragment requires sequential PNs, so we
  16 also move this test to a separate function to make the code easier to
  17 maintain.
  18
  19 Cc: stable@vger.kernel.org
  20 Signed-off-by: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
  21 Signed-off-by: Johannes Berg <johannes.berg@intel.com>
  22 ---
  23
  24 --- a/net/mac80211/rx.c
  25 +++ b/net/mac80211/rx.c
  26 @@ -2204,6 +2204,16 @@ ieee80211_reassemble_find(struct ieee802
  27         return NULL;
  28  }
  29
  30 +static bool requires_sequential_pn(struct ieee80211_rx_data *rx, __le16 fc)
  31 +{
  32 +       return rx->key &&
  33 +               (rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP ||
  34 +                rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP_256 ||
  35 +                rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP ||
  36 +                rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP_256) &&
  37 +               ieee80211_has_protected(fc);
  38 +}
  39 +
  40  static ieee80211_rx_result debug_noinline
  41  ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
  42  {
  43 @@ -2248,12 +2258,7 @@ ieee80211_rx_h_defragment(struct ieee802
  44                 /* This is the first fragment of a new frame. */
  45                 entry = ieee80211_reassemble_add(rx->sdata, frag, seq,
  46                                                  rx->seqno_idx, &(rx->skb));
  47 -               if (rx->key &&
  48 -                   (rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP ||
  49 -                    rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP_256 ||
  50 -                    rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP ||
  51 -                    rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP_256) &&
  52 -                   ieee80211_has_protected(fc)) {
  53 +               if (requires_sequential_pn(rx, fc)) {
  54                         int queue = rx->security_idx;
  55
  56                         /* Store CCMP/GCMP PN so that we can verify that the
  57 @@ -2295,11 +2300,7 @@ ieee80211_rx_h_defragment(struct ieee802
  58                 u8 pn[IEEE80211_CCMP_PN_LEN], *rpn;
  59                 int queue;
  60
  61 -               if (!rx->key ||
  62 -                   (rx->key->conf.cipher != WLAN_CIPHER_SUITE_CCMP &&
  63 -                    rx->key->conf.cipher != WLAN_CIPHER_SUITE_CCMP_256 &&
  64 -                    rx->key->conf.cipher != WLAN_CIPHER_SUITE_GCMP &&
  65 -                    rx->key->conf.cipher != WLAN_CIPHER_SUITE_GCMP_256))
  66 +               if (!requires_sequential_pn(rx, fc))
  67                         return RX_DROP_UNUSABLE;
  68                 memcpy(pn, entry->last_pn, IEEE80211_CCMP_PN_LEN);
  69                 for (i = IEEE80211_CCMP_PN_LEN - 1; i >= 0; i--) {