cfg80211/nl80211: Optional authentication offload to userspace

This interface allows the host driver to offload the authentication to
user space. This is exclusively defined for host drivers that do not
define separate commands for authentication and association, but rely on
userspace SME (e.g., in wpa_supplicant for the ~WPA_DRIVER_FLAGS_SME
case) for the authentication to happen. This can be used to implement
SAE without full implementation in the kernel/firmware while still being
able to use NL80211_CMD_CONNECT with driver-based BSS selection.

Host driver sends NL80211_CMD_EXTERNAL_AUTH event to start/abort
authentication to the port on which connect is triggered and status
of authentication is further indicated by user space to host
driver through the same command response interface.

User space entities advertise this capability through the
NL80211_ATTR_EXTERNAL_AUTH_SUPP flag in the NL80211_CMD_CONNECT request.
Host drivers shall look at this capability to offload the authentication.

Signed-off-by: Srinivas Dasari <[e-mail]>
Signed-off-by: Jouni Malinen <[e-mail]>
[add socket connection ownership check]
Signed-off-by: Johannes Berg <[e-mail]>

include/net/cfg80211.h

···
  * @ASSOC_REQ_DISABLE_HT:  Disable HT (802.11n)
  * @ASSOC_REQ_DISABLE_VHT:  Disable VHT
  * @ASSOC_REQ_USE_RRM: Declare RRM capability in this association
+ * @CONNECT_REQ_EXTERNAL_AUTH_SUPPORT: User space indicates external
+ *	authentication capability. Drivers can offload authentication to
+ *	userspace if this flag is set. Only applicable for cfg80211_connect()
+ *	request (connect callback).
  */
 enum cfg80211_assoc_req_flags {
-	ASSOC_REQ_DISABLE_HT		= BIT(0),
-	ASSOC_REQ_DISABLE_VHT		= BIT(1),
-	ASSOC_REQ_USE_RRM		= BIT(2),
+	ASSOC_REQ_DISABLE_HT			= BIT(0),
+	ASSOC_REQ_DISABLE_VHT			= BIT(1),
+	ASSOC_REQ_USE_RRM			= BIT(2),
+	CONNECT_REQ_EXTERNAL_AUTH_SUPPORT	= BIT(3),
 };
 
 /**
···
 };
 
 /**
+ * struct cfg80211_external_auth_params - Trigger External authentication.
+ *
+ * Commonly used across the external auth request and event interfaces.
+ *
+ * @action: action type / trigger for external authentication. Only significant
+ *	for the authentication request event interface (driver to user space).
+ * @bssid: BSSID of the peer with which the authentication has
+ *	to happen. Used by both the authentication request event and
+ *	authentication response command interface.
+ * @ssid: SSID of the AP.  Used by both the authentication request event and
+ *	authentication response command interface.
+ * @key_mgmt_suite: AKM suite of the respective authentication. Used by the
+ *	authentication request event interface.
+ * @status: status code, %WLAN_STATUS_SUCCESS for successful authentication,
+ *	use %WLAN_STATUS_UNSPECIFIED_FAILURE if user space cannot give you
+ *	the real status code for failures. Used only for the authentication
+ *	response command interface (user space to driver).
+ */
+struct cfg80211_external_auth_params {
+	enum nl80211_external_auth_action action;
+	u8 bssid[ETH_ALEN] __aligned(2);
+	struct cfg80211_ssid ssid;
+	unsigned int key_mgmt_suite;
+	u16 status;
+};
+
+/**
  * struct cfg80211_ops - backend description for wireless configuration
  *
  * This struct is registered by fullmac card drivers and/or wireless stacks
···
  *	(invoked with the wireless_dev mutex held)
  * @del_pmk: delete the previously configured PMK for the given authenticator.
  *	(invoked with the wireless_dev mutex held)
+ *
+ * @external_auth: indicates result of offloaded authentication processing from
+ *     user space
  */
 struct cfg80211_ops {
 	int	(*suspend)(struct wiphy *wiphy, struct cfg80211_wowlan *wow);
···
 			   const struct cfg80211_pmk_conf *conf);
 	int	(*del_pmk)(struct wiphy *wiphy, struct net_device *dev,
 			   const u8 *aa);
+	int     (*external_auth)(struct wiphy *wiphy, struct net_device *dev,
+				 struct cfg80211_external_auth_params *params);
 };
 
 /*
···
 
 /* ethtool helper */
 void cfg80211_get_drvinfo(struct net_device *dev, struct ethtool_drvinfo *info);
+
+/**
+ * cfg80211_external_auth_request - userspace request for authentication
+ * @netdev: network device
+ * @params: External authentication parameters
+ * @gfp: allocation flags
+ * Returns: 0 on success, < 0 on error
+ */
+int cfg80211_external_auth_request(struct net_device *netdev,
+				   struct cfg80211_external_auth_params *params,
+				   gfp_t gfp);
 
 /* Logging, debugging and troubleshooting/diagnostic helpers. */
 

include/uapi/linux/nl80211.h

···
  *
  * @NL80211_CMD_RELOAD_REGDB: Request that the regdb firmware file is reloaded.
  *
+ * @NL80211_CMD_EXTERNAL_AUTH: This interface is exclusively defined for host
+ *	drivers that do not define separate commands for authentication and
+ *	association, but rely on user space for the authentication to happen.
+ *	This interface acts both as the event request (driver to user space)
+ *	to trigger the authentication and command response (userspace to
+ *	driver) to indicate the authentication status.
+ *
+ *	User space uses the %NL80211_CMD_CONNECT command to the host driver to
+ *	trigger a connection. The host driver selects a BSS and further uses
+ *	this interface to offload only the authentication part to the user
+ *	space. Authentication frames are passed between the driver and user
+ *	space through the %NL80211_CMD_FRAME interface. Host driver proceeds
+ *	further with the association after getting successful authentication
+ *	status. User space indicates the authentication status through
+ *	%NL80211_ATTR_STATUS_CODE attribute in %NL80211_CMD_EXTERNAL_AUTH
+ *	command interface.
+ *
+ *	Host driver reports this status on an authentication failure to the
+ *	user space through the connect result as the user space would have
+ *	initiated the connection through the connect request.
+ *
  * @NL80211_CMD_MAX: highest used command number
  * @__NL80211_CMD_AFTER_LAST: internal use
  */
···
 	NL80211_CMD_PORT_AUTHORIZED,
 
 	NL80211_CMD_RELOAD_REGDB,
+
+	NL80211_CMD_EXTERNAL_AUTH,
 
 	/* add new commands above here */
 
···
  * @NL80211_ATTR_PMKR0_NAME: PMK-R0 Name for offloaded FT.
  * @NL80211_ATTR_PORT_AUTHORIZED: (reserved)
  *
+ * @NL80211_ATTR_EXTERNAL_AUTH_ACTION: Identify the requested external
+ *     authentication operation (u32 attribute with an
+ *     &enum nl80211_external_auth_action value). This is used with the
+ *     &NL80211_CMD_EXTERNAL_AUTH request event.
+ * @NL80211_ATTR_EXTERNAL_AUTH_SUPPORT: Flag attribute indicating that the user
+ *     space supports external authentication. This attribute shall be used
+ *     only with %NL80211_CMD_CONNECT request. The driver may offload
+ *     authentication processing to user space if this capability is indicated
+ *     in NL80211_CMD_CONNECT requests from the user space.
+ *
  * @NUM_NL80211_ATTR: total number of nl80211_attrs available
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
···
 	NL80211_ATTR_WANT_1X_4WAY_HS,
 	NL80211_ATTR_PMKR0_NAME,
 	NL80211_ATTR_PORT_AUTHORIZED,
+
+	NL80211_ATTR_EXTERNAL_AUTH_ACTION,
+	NL80211_ATTR_EXTERNAL_AUTH_SUPPORT,
 
 	/* add attributes here, update the policy in nl80211.c */
 
···
 	/* keep last */
 	NUM_NL80211_NAN_MATCH_ATTR,
 	NL80211_NAN_MATCH_ATTR_MAX = NUM_NL80211_NAN_MATCH_ATTR - 1
+};
+
+/**
+ * nl80211_external_auth_action - Action to perform with external
+ *     authentication request. Used by NL80211_ATTR_EXTERNAL_AUTH_ACTION.
+ * @NL80211_EXTERNAL_AUTH_START: Start the authentication.
+ * @NL80211_EXTERNAL_AUTH_ABORT: Abort the ongoing authentication.
+ */
+enum nl80211_external_auth_action {
+	NL80211_EXTERNAL_AUTH_START,
+	NL80211_EXTERNAL_AUTH_ABORT,
 };
 
 #endif /* __LINUX_NL80211_H */

net/wireless/nl80211.c

···
 	[NL80211_ATTR_FILS_CACHE_ID] = { .len = 2 },
 	[NL80211_ATTR_PMK] = { .type = NLA_BINARY, .len = PMK_MAX_LEN },
 	[NL80211_ATTR_SCHED_SCAN_MULTI] = { .type = NLA_FLAG },
+	[NL80211_ATTR_EXTERNAL_AUTH_SUPPORT] = { .type = NLA_FLAG },
 };
 
 /* policy for the key attributes */
···
 		return -EINVAL;
 	}
 
+	if (nla_get_flag(info->attrs[NL80211_ATTR_EXTERNAL_AUTH_SUPPORT])) {
+		if (!info->attrs[NL80211_ATTR_SOCKET_OWNER]) {
+			GENL_SET_ERR_MSG(info,
+					 "external auth requires connection ownership");
+			return -EINVAL;
+		}
+		connect.flags |= CONNECT_REQ_EXTERNAL_AUTH_SUPPORT;
+	}
+
 	wdev_lock(dev->ieee80211_ptr);
 
 	err = cfg80211_connect(rdev, dev, &connect, connkeys,
···
 	return ret;
 }
 
+static int nl80211_external_auth(struct sk_buff *skb, struct genl_info *info)
+{
+	struct cfg80211_registered_device *rdev = info->user_ptr[0];
+	struct net_device *dev = info->user_ptr[1];
+	struct cfg80211_external_auth_params params;
+
+	if (rdev->ops->external_auth)
+		return -EOPNOTSUPP;
+
+	if (!info->attrs[NL80211_ATTR_SSID])
+		return -EINVAL;
+
+	if (!info->attrs[NL80211_ATTR_BSSID])
+		return -EINVAL;
+
+	if (!info->attrs[NL80211_ATTR_STATUS_CODE])
+		return -EINVAL;
+
+	memset(&params, 0, sizeof(params));
+
+	params.ssid.ssid_len = nla_len(info->attrs[NL80211_ATTR_SSID]);
+	if (params.ssid.ssid_len == 0 ||
+	    params.ssid.ssid_len > IEEE80211_MAX_SSID_LEN)
+		return -EINVAL;
+	memcpy(params.ssid.ssid, nla_data(info->attrs[NL80211_ATTR_SSID]),
+	       params.ssid.ssid_len);
+
+	memcpy(params.bssid, nla_data(info->attrs[NL80211_ATTR_BSSID]),
+	       ETH_ALEN);
+
+	params.status = nla_get_u16(info->attrs[NL80211_ATTR_STATUS_CODE]);
+
+	return rdev_external_auth(rdev, dev, &params);
+}
+
 #define NL80211_FLAG_NEED_WIPHY		0x01
 #define NL80211_FLAG_NEED_NETDEV	0x02
 #define NL80211_FLAG_NEED_RTNL		0x04
···
 		.cmd = NL80211_CMD_DEL_PMK,
 		.doit = nl80211_del_pmk,
 		.policy = nl80211_policy,
+		.internal_flags = NL80211_FLAG_NEED_NETDEV_UP |
+				  NL80211_FLAG_NEED_RTNL,
+	},
+	{
+		.cmd = NL80211_CMD_EXTERNAL_AUTH,
+		.doit = nl80211_external_auth,
+		.policy = nl80211_policy,
+		.flags = GENL_ADMIN_PERM,
 		.internal_flags = NL80211_FLAG_NEED_NETDEV_UP |
 				  NL80211_FLAG_NEED_RTNL,
 	},
···
  out:
 	nlmsg_free(msg);
 }
+
+int cfg80211_external_auth_request(struct net_device *dev,
+				   struct cfg80211_external_auth_params *params,
+				   gfp_t gfp)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
+	struct sk_buff *msg;
+	void *hdr;
+
+	if (!wdev->conn_owner_nlportid)
+		return -EINVAL;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, gfp);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = nl80211hdr_put(msg, 0, 0, 0, NL80211_CMD_EXTERNAL_AUTH);
+	if (!hdr)
+		goto nla_put_failure;
+
+	if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
+	    nla_put_u32(msg, NL80211_ATTR_IFINDEX, dev->ifindex) ||
+	    nla_put_u32(msg, NL80211_ATTR_AKM_SUITES, params->key_mgmt_suite) ||
+	    nla_put_u32(msg, NL80211_ATTR_EXTERNAL_AUTH_ACTION,
+			params->action) ||
+	    nla_put(msg, NL80211_ATTR_BSSID, ETH_ALEN, params->bssid) ||
+	    nla_put(msg, NL80211_ATTR_SSID, params->ssid.ssid_len,
+		    params->ssid.ssid))
+		goto nla_put_failure;
+
+	genlmsg_end(msg, hdr);
+	genlmsg_unicast(wiphy_net(&rdev->wiphy), msg,
+			wdev->conn_owner_nlportid);
+	return 0;
+
+ nla_put_failure:
+	nlmsg_free(msg);
+	return -ENOBUFS;
+}
+EXPORT_SYMBOL(cfg80211_external_auth_request);
 
 /* initialisation/exit functions */
 

net/wireless/rdev-ops.h

···
 	trace_rdev_return_int(&rdev->wiphy, ret);
 	return ret;
 }
+
+static inline int
+rdev_external_auth(struct cfg80211_registered_device *rdev,
+		   struct net_device *dev,
+		   struct cfg80211_external_auth_params *params)
+{
+	int ret = -EOPNOTSUPP;
+
+	trace_rdev_external_auth(&rdev->wiphy, dev, params);
+	if (rdev->ops->external_auth)
+		ret = rdev->ops->external_auth(&rdev->wiphy, dev, params);
+	trace_rdev_return_int(&rdev->wiphy, ret);
+	return ret;
+}
+
 #endif /* __CFG80211_RDEV_OPS */

net/wireless/trace.h

···
 		  WIPHY_PR_ARG, NETDEV_PR_ARG, MAC_PR_ARG(aa))
 );
 
+TRACE_EVENT(rdev_external_auth,
+	    TP_PROTO(struct wiphy *wiphy, struct net_device *netdev,
+		     struct cfg80211_external_auth_params *params),
+	    TP_ARGS(wiphy, netdev, params),
+	    TP_STRUCT__entry(WIPHY_ENTRY
+			     NETDEV_ENTRY
+			     MAC_ENTRY(bssid)
+			     __array(u8, ssid, IEEE80211_MAX_SSID_LEN + 1)
+			     __field(u16, status)
+	    ),
+	    TP_fast_assign(WIPHY_ASSIGN;
+			   NETDEV_ASSIGN;
+			   MAC_ASSIGN(bssid, params->bssid);
+			   memset(__entry->ssid, 0, IEEE80211_MAX_SSID_LEN + 1);
+			   memcpy(__entry->ssid, params->ssid.ssid,
+				  params->ssid.ssid_len);
+			   __entry->status = params->status;
+	    ),
+	    TP_printk(WIPHY_PR_FMT ", " NETDEV_PR_FMT ", bssid: " MAC_PR_FMT
+		      ", ssid: %s, status: %u", WIPHY_PR_ARG, NETDEV_PR_ARG,
+		      __entry->bssid, __entry->ssid, __entry->status)
+);
+
 /*************************************************************
  *	     cfg80211 exported functions traces		     *
  *************************************************************/