AP: Allow PTK rekeying without Ext KeyID to be disabled as a workaround

[thirdparty/hostap.git] / hostapd / hostapd.conf

diff --git a/hostapd/hostapd.conf b/hostapd/hostapd.conf
index 0433fed8a75a741ef981d4634822401daaeecb04..0f8461d492905a343079911c59e920bc74c7ddda 100644 (file)
--- a/hostapd/hostapd.conf
+++ b/hostapd/hostapd.conf
@@ -904,6 +904,8 @@ eapol_key_index_workaround=0
 
 # EAP reauthentication period in seconds (default: 3600 seconds; 0 = disable
 # reauthentication).
+# Note: Reauthentications may enforce a disconnection, check the related
+# parameter wpa_deny_ptk0_rekey for details.
 #eap_reauth_period=3600
 
 # Use PAE group address (01:80:c2:00:00:03) instead of individual target
@@ -1608,8 +1610,40 @@ own_ip_addr=127.0.0.1
 
 # Maximum lifetime for PTK in seconds. This can be used to enforce rekeying of
 # PTK to mitigate some attacks against TKIP deficiencies.
+# Warning: PTK rekeying is buggy with many drivers/devices and with such
+# devices, the only secure method to rekey the PTK without Extended Key ID
+# support requires a disconnection. Check the related parameter
+# wpa_deny_ptk0_rekey for details.
 #wpa_ptk_rekey=600
 
+# Workaround for PTK rekey issues
+#
+# Rekeying the PTK without using "Extended Key ID for Individually Addressed
+# Frames" (two different Key ID values for pairwise keys) can, depending on the
+# used cards/drivers, impact the security and stability of connections. Both
+# ends can accidentally trick one end to drop all packets send by it until the
+# connection is torn down or rekeyed again. Additionally, some drivers may
+# skip/break the encryption for the time window the key is updated (normally a
+# few milliseconds).
+#
+# To avoid such issues, hostapd can now replace all PTK rekeys using only keyid
+# 0 (PTK0 rekeys) with disconnection that forces the remote stations to
+# reconnect instead.
+#
+# EAP reauthentication depends on replacing the PTK and is therefore just
+# another way to rekey the PTK and is affected by this parameter, too.
+#
+# "Extended Key ID for Individually Addressed Frames" is avoiding the issues
+# using two separate keys and this parameter will be ignored when using it
+# (i.e., PTK rekeying is allowed regardless of this parameter value).
+#
+# Available options:
+# 0 = always rekey when configured/instructed (default)
+# 1 = only rekey when the local driver is explicitly indicating it can perform
+#      this operation without issues
+# 2 = never allow PTK0 rekeys
+#wpa_deny_ptk0_rekey=0
+
 # The number of times EAPOL-Key Message 1/4 and Message 3/4 in the RSN 4-Way
 # Handshake are retried per 4-Way Handshake attempt.
 # (dot11RSNAConfigPairwiseUpdateCount)