[RFC PATCH 1/1] wpa_supplicant: Implement SSID-based MAC address randomization

[João Lucas]

Signed-off-by: João Lucas <jlucas at disroot.org>
---
 wpa_supplicant/config.c         |  4 ++--
 wpa_supplicant/config_ssid.h    |  1 +
 wpa_supplicant/wpa_supplicant.c | 29 +++++++++++++++++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/wpa_supplicant/config.c b/wpa_supplicant/config.c
index 228b1b2c9..b127f899e 100644
--- a/wpa_supplicant/config.c
+++ b/wpa_supplicant/config.c
@@ -2729,7 +2729,7 @@ static const struct parse_data ssid_fields[] = {
 	{ INT(update_identifier) },
 	{ STR_RANGE(roaming_consortium_selection, 0, MAX_ROAMING_CONS_OI_LEN) },
 #endif /* CONFIG_HS20 */
-	{ INT_RANGE(mac_addr, 0, 3) },
+	{ INT_RANGE(mac_addr, 0, 4) },
 	{ FUNC_KEY(mac_value) },
 	{ INT_RANGE(pbss, 0, 2) },
 	{ INT_RANGE(wps_disabled, 0, 1) },
@@ -5562,7 +5562,7 @@ static const struct global_parse_data global_fields[] = {
 	{ STR(osu_dir), 0 },
 	{ STR(wowlan_triggers), CFG_CHANGED_WOWLAN_TRIGGERS },
 	{ INT(p2p_search_delay), 0},
-	{ INT_RANGE(mac_addr, 0, 2), 0 },
+	{ INT_RANGE(mac_addr, 0, 4), 0 },
 	{ INT(rand_addr_lifetime), 0 },
 	{ INT_RANGE(preassoc_mac_addr, 0, 2), 0 },
 	{ INT(key_mgmt_offload), 0},
diff --git a/wpa_supplicant/config_ssid.h b/wpa_supplicant/config_ssid.h
index c5a9dbccc..a14af3952 100644
--- a/wpa_supplicant/config_ssid.h
+++ b/wpa_supplicant/config_ssid.h
@@ -77,6 +77,7 @@ enum wpas_mac_addr_style {
 	WPAS_MAC_ADDR_STYLE_RANDOM = 1,
 	WPAS_MAC_ADDR_STYLE_RANDOM_SAME_OUI = 2,
 	WPAS_MAC_ADDR_STYLE_DEDICATED_PER_ESS = 3,
+	WPAS_MAC_ADDR_STYLE_DERIVED_FROM_ESS = 4,
 };
 
 /**
diff --git a/wpa_supplicant/wpa_supplicant.c b/wpa_supplicant/wpa_supplicant.c
index 132d91598..df520609e 100644
--- a/wpa_supplicant/wpa_supplicant.c
+++ b/wpa_supplicant/wpa_supplicant.c
@@ -20,6 +20,7 @@
 #include "crypto/crypto.h"
 #include "crypto/random.h"
 #include "crypto/sha1.h"
+#include "crypto/sha256.h"
 #include "eapol_supp/eapol_supp_sm.h"
 #include "eap_peer/eap.h"
 #include "eap_peer/eap_proxy.h"
@@ -2558,6 +2559,25 @@ void wpas_connect_work_done(struct wpa_supplicant *wpa_s)
 	radio_work_done(work);
 }
 
+int random_mac_addr_from_ssid(u8 *addr, struct wpa_supplicant *wpa_s,
+                              struct wpa_ssid *ssid)
+{
+  u8 digest[32];
+  const u8 *data[] = {ssid->ssid, wpa_s->perm_addr};
+  const size_t len[] = {ssid->ssid_len, ETH_ALEN};
+
+  wpa_dbg(wpa_s, MSG_DEBUG,
+          "Deriving MAC addr from SSID: '%s' and perm_addr " MACSTR, ssid->ssid,
+          MAC2STR(wpa_s->perm_addr));
+
+  if (sha256_vector(2, data, len, digest) < 0)
+    return -1;
+
+  os_memcpy(addr, digest, ETH_ALEN);
+  addr[0] &= 0xfe; /* unicast */
+  addr[0] |= 0x02; /* locally administered */
+  return 0;
+}
 
 int wpas_update_random_addr(struct wpa_supplicant *wpa_s,
 			    enum wpas_mac_addr_style style,
@@ -2605,6 +2625,15 @@ int wpas_update_random_addr(struct wpa_supplicant *wpa_s,
 		}
 		os_memcpy(addr, ssid->mac_value, ETH_ALEN);
 		break;
+	case WPAS_MAC_ADDR_STYLE_DERIVED_FROM_ESS:
+		if (!ssid) {
+			wpa_msg(wpa_s, MSG_INFO,
+				"Invalid 'ssid' for address policy 4");
+			return -1;
+		}
+		if (random_mac_addr_from_ssid(addr, wpa_s, ssid) < 0)
+			return -1;
+		break;
 	default:
 		return -1;
 	}
-- 
2.45.3