Prevent ieee80211_get_txkey() from returning the integrity group temporal

key (IGTK) if a node doesn't have management frame protection (MFP) enabled.
The IGTK is not initialized if MFP is disabled, so using it triggers this
panic in ieee80211_encrypt(): panic("invalid key cipher 0x%x", k->k_cipher)

(As far as I can tell, at present, MFP is never enabled.)

Problem reported and fix tested by tj@ on athn(4) hostap

diff --git a/sys/net80211/ieee80211_crypto.c b/sys/net80211/ieee80211_crypto.c
index 046412f..8ede6e3 100644 (file)
--- a/sys/net80211/ieee80211_crypto.c
+++ b/sys/net80211/ieee80211_crypto.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ieee80211_crypto.c,v 1.73 2018/04/28 14:46:10 stsp Exp $      */
+/*     $OpenBSD: ieee80211_crypto.c,v 1.74 2018/09/24 20:14:59 stsp Exp $      */
 
 /*-
  * Copyright (c) 2008 Damien Bergamini <damien.bergamini@free.fr>
@@ -196,13 +196,12 @@ ieee80211_get_txkey(struct ieee80211com *ic, const struct ieee80211_frame *wh,
            ni->ni_rsncipher != IEEE80211_CIPHER_USEGROUP)
                return &ni->ni_pairwise_key;
 
-       if ((ic->ic_flags & IEEE80211_F_WEPON) ||
-           !IEEE80211_IS_MULTICAST(wh->i_addr1) ||
-           (wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) !=
-           IEEE80211_FC0_TYPE_MGT)
-               kid = ic->ic_def_txkey;
-       else
+       /* All other cases (including WEP) use a group key. */
+       if (ni->ni_flags & IEEE80211_NODE_MFP)
                kid = ic->ic_igtk_kid;
+       else
+               kid = ic->ic_def_txkey;
+
        return &ic->ic_nw_keys[kid];
 }