nl80211: support 4-way handshake offloading for WPA/WPA2-PSK in AP mode

Let drivers advertise support for AP-mode WPA/WPA2-PSK 4-way handshake
offloading with a new NL80211_EXT_FEATURE_4WAY_HANDSHAKE_AP_PSK flag.

Extend use of NL80211_ATTR_PMK attribute indicating it might be passed
as part of NL80211_CMD_START_AP command, and contain the PSK (which is
the PMK, hence the name).

The driver is assumed to handle the 4-way handshake by itself in this
case, instead of relying on userspace.
Signed-off-by: Chung-Hsien Hsu <stanley.hsu@cypress.com>
Signed-off-by: Chi-Hsien Lin <chi-hsien.lin@cypress.com>
Link: https://lore.kernel.org/r/20200623134938.39997-2-chi-hsien.lin@cypress.comSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/uapi/linux/nl80211.h

@@ -183,18 +183,27 @@
  *
  * By setting @NL80211_EXT_FEATURE_4WAY_HANDSHAKE_STA_PSK flag drivers
  * can indicate they support offloading EAPOL handshakes for WPA/WPA2
- * preshared key authentication. In %NL80211_CMD_CONNECT the preshared
- * key should be specified using %NL80211_ATTR_PMK. Drivers supporting
- * this offload may reject the %NL80211_CMD_CONNECT when no preshared
- * key material is provided, for example when that driver does not
- * support setting the temporal keys through %CMD_NEW_KEY.
+ * preshared key authentication in station mode. In %NL80211_CMD_CONNECT
+ * the preshared key should be specified using %NL80211_ATTR_PMK. Drivers
+ * supporting this offload may reject the %NL80211_CMD_CONNECT when no
+ * preshared key material is provided, for example when that driver does
+ * not support setting the temporal keys through %NL80211_CMD_NEW_KEY.
  *
  * Similarly @NL80211_EXT_FEATURE_4WAY_HANDSHAKE_STA_1X flag can be
  * set by drivers indicating offload support of the PTK/GTK EAPOL
- * handshakes during 802.1X authentication. In order to use the offload
- * the %NL80211_CMD_CONNECT should have %NL80211_ATTR_WANT_1X_4WAY_HS
- * attribute flag. Drivers supporting this offload may reject the
- * %NL80211_CMD_CONNECT when the attribute flag is not present.
+ * handshakes during 802.1X authentication in station mode. In order to
+ * use the offload the %NL80211_CMD_CONNECT should have
+ * %NL80211_ATTR_WANT_1X_4WAY_HS attribute flag. Drivers supporting this
+ * offload may reject the %NL80211_CMD_CONNECT when the attribute flag is
+ * not present.
+ *
+ * By setting @NL80211_EXT_FEATURE_4WAY_HANDSHAKE_AP_PSK flag drivers
+ * can indicate they support offloading EAPOL handshakes for WPA/WPA2
+ * preshared key authentication in AP mode. In %NL80211_CMD_START_AP
+ * the preshared key should be specified using %NL80211_ATTR_PMK. Drivers
+ * supporting this offload may reject the %NL80211_CMD_START_AP when no
+ * preshared key material is provided, for example when that driver does
+ * not support setting the temporal keys through %NL80211_CMD_NEW_KEY.
  *
  * For 802.1X the PMK or PMK-R0 are set by providing %NL80211_ATTR_PMK
  * using %NL80211_CMD_SET_PMK. For offloaded FT support also
@@ -2362,10 +2371,11 @@ enum nl80211_commands {
  *
  * @NL80211_ATTR_PMK: attribute for passing PMK key material. Used with
  *	%NL80211_CMD_SET_PMKSA for the PMKSA identified by %NL80211_ATTR_PMKID.
- *	For %NL80211_CMD_CONNECT it is used to provide PSK for offloading 4-way
- *	handshake for WPA/WPA2-PSK networks. For 802.1X authentication it is
- *	used with %NL80211_CMD_SET_PMK. For offloaded FT support this attribute
- *	specifies the PMK-R0 if NL80211_ATTR_PMKR0_NAME is included as well.
+ *	For %NL80211_CMD_CONNECT and %NL80211_CMD_START_AP it is used to provide
+ *	PSK for offloading 4-way handshake for WPA/WPA2-PSK networks. For 802.1X
+ *	authentication it is used with %NL80211_CMD_SET_PMK. For offloaded FT
+ *	support this attribute specifies the PMK-R0 if NL80211_ATTR_PMKR0_NAME
+ *	is included as well.
  *
  * @NL80211_ATTR_SCHED_SCAN_MULTI: flag attribute which user-space shall use to
  *	indicate that it supports multiple active scheduled scan requests.
@@ -5807,6 +5817,10 @@ enum nl80211_feature_flags {
  * @NL80211_EXT_FEATURE_OPERATING_CHANNEL_VALIDATION: Driver supports Operating
  *	Channel Validation (OCV) when using driver's SME for RSNA handshakes.
  *
+ * @NL80211_EXT_FEATURE_4WAY_HANDSHAKE_AP_PSK: Device wants to do 4-way
+ *	handshake with PSK in AP mode (PSK is passed as part of the start AP
+ *	command).
+ *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
  */
@@ -5863,6 +5877,7 @@ enum nl80211_ext_feature_index {
 	NL80211_EXT_FEATURE_SCAN_FREQ_KHZ,
 	NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211_TX_STATUS,
 	NL80211_EXT_FEATURE_OPERATING_CHANNEL_VALIDATION,
+	NL80211_EXT_FEATURE_4WAY_HANDSHAKE_AP_PSK,
 
 	/* add new features before the definition below */
 	NUM_NL80211_EXT_FEATURES,

net/wireless/nl80211.c

@@ -9442,7 +9442,9 @@ static int nl80211_crypto_settings(struct cfg80211_registered_device *rdev,
 		if (nla_len(info->attrs[NL80211_ATTR_PMK]) != WLAN_PMK_LEN)
 			return -EINVAL;
 		if (!wiphy_ext_feature_isset(&rdev->wiphy,
-					     NL80211_EXT_FEATURE_4WAY_HANDSHAKE_STA_PSK))
+					     NL80211_EXT_FEATURE_4WAY_HANDSHAKE_STA_PSK) &&
+		    !wiphy_ext_feature_isset(&rdev->wiphy,
+					     NL80211_EXT_FEATURE_4WAY_HANDSHAKE_AP_PSK))
 			return -EINVAL;
 		settings->psk = nla_data(info->attrs[NL80211_ATTR_PMK]);
 	}