From 42d98e02193d163c1523a8840a2effcc4c6eb111 Mon Sep 17 00:00:00 2001 From: Mathy Vanhoef Date: Tue, 11 May 2021 20:02:43 +0200 Subject: [PATCH] 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 Link: https://lore.kernel.org/r/20210511200110.3f8290e59823.I622a67769ed39257327a362cfc09c812320eb979@changeid Signed-off-by: Johannes Berg Signed-off-by: Greg Kroah-Hartman --- net/mac80211/ieee80211_i.h | 1 + net/mac80211/key.c | 7 +++++++ net/mac80211/key.h | 2 ++ net/mac80211/rx.c | 6 ++++++ 4 files changed, 16 insertions(+) diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h index d691378..13d990c 100644 --- a/net/mac80211/ieee80211_i.h +++ b/net/mac80211/ieee80211_i.h @@ -97,6 +97,7 @@ 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 8c5f829..6a72c33 100644 --- a/net/mac80211/key.c +++ b/net/mac80211/key.c @@ -799,6 +799,7 @@ int ieee80211_key_link(struct ieee80211_key *key, struct ieee80211_sub_if_data *sdata, struct sta_info *sta) { + 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; @@ -850,6 +851,12 @@ 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); ret = ieee80211_key_replace(sdata, sta, pairwise, old_key, key); diff --git a/net/mac80211/key.h b/net/mac80211/key.h index 7ad72e9..1e326c8 100644 --- a/net/mac80211/key.h +++ b/net/mac80211/key.h @@ -128,6 +128,8 @@ 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 abe5a03..c17a0ab 100644 --- a/net/mac80211/rx.c +++ b/net/mac80211/rx.c @@ -2265,6 +2265,7 @@ 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); @@ -2302,6 +2303,11 @@ 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]++; -- 2.7.4