EAP-SIM/AKA: Add support for anonymous@realm

SIM-based EAP authentication with IMSI encryption requires a special EAP
Identity response: anonymous@realm. Then the server sends AKA-Identity
request which is answered with the encrypted IMSI. Add logic that
indicates if the special anonymous identity is used. Otherwise, this
field is used for storing the pseudonym.

Test: Connect to Carrier Wi-Fi, verify correct behavior from captures
Test: Connect to non IMSI encrypted EAP-AKA AP, verify pseudonym usage
Signed-off-by: Hai Shalom <haishalom@google.com>

src/eap_common/eap_sim_common.c

@@ -1203,3 +1203,19 @@ void eap_sim_report_notification(void *msg_ctx, int notification, int aka)
 		}
 	}
 }
+
+
+int eap_sim_anonymous_username(const u8 *id, size_t id_len)
+{
+	static const char *anonymous_id_prefix = "anonymous@";
+	size_t anonymous_id_len = os_strlen(anonymous_id_prefix);
+
+	if (id_len > anonymous_id_len &&
+	    os_memcmp(id, anonymous_id_prefix, anonymous_id_len) == 0)
+		return 1; /* 'anonymous@realm' */
+
+	if (id_len > 1 && id[0] == '@')
+		return 1; /* '@realm' */
+
+	return 0;
+}

src/eap_common/eap_sim_common.h

@@ -226,5 +226,6 @@ int eap_sim_msg_add_encr_end(struct eap_sim_msg *msg, u8 *k_encr,
 			     int attr_pad);
 
 void eap_sim_report_notification(void *msg_ctx, int notification, int aka);
+int eap_sim_anonymous_username(const u8 *id, size_t id_len);
 
 #endif /* EAP_SIM_COMMON_H */

src/eap_peer/eap_aka.c

@@ -623,7 +623,9 @@ static struct wpabuf * eap_aka_response_identity(struct eap_sm *sm,
 		identity_len = data->reauth_id_len;
 		data->reauth = 1;
 	} else if ((id_req == ANY_ID || id_req == FULLAUTH_ID) &&
-		   data->pseudonym) {
+		   data->pseudonym &&
+		   !eap_sim_anonymous_username(data->pseudonym,
+					       data->pseudonym_len)) {
 		identity = data->pseudonym;
 		identity_len = data->pseudonym_len;
 		eap_aka_clear_identities(sm, data, CLEAR_REAUTH_ID);
@@ -1027,7 +1029,9 @@ static struct wpabuf * eap_aka_process_challenge(struct eap_sm *sm,
 	if (data->last_eap_identity) {
 		identity = data->last_eap_identity;
 		identity_len = data->last_eap_identity_len;
-	} else if (data->pseudonym) {
+	} else if (data->pseudonym &&
+		   !eap_sim_anonymous_username(data->pseudonym,
+					       data->pseudonym_len)) {
 		identity = data->pseudonym;
 		identity_len = data->pseudonym_len;
 	} else {

src/eap_peer/eap_sim.c

@@ -493,7 +493,9 @@ static struct wpabuf * eap_sim_response_start(struct eap_sm *sm,
 		identity_len = data->reauth_id_len;
 		data->reauth = 1;
 	} else if ((id_req == ANY_ID || id_req == FULLAUTH_ID) &&
-		   data->pseudonym) {
+		   data->pseudonym &&
+		   !eap_sim_anonymous_username(data->pseudonym,
+					       data->pseudonym_len)) {
 		identity = data->pseudonym;
 		identity_len = data->pseudonym_len;
 		eap_sim_clear_identities(sm, data, CLEAR_REAUTH_ID);
@@ -769,7 +771,9 @@ static struct wpabuf * eap_sim_process_challenge(struct eap_sm *sm,
 	if (data->last_eap_identity) {
 		identity = data->last_eap_identity;
 		identity_len = data->last_eap_identity_len;
-	} else if (data->pseudonym) {
+	} else if (data->pseudonym &&
+		   !eap_sim_anonymous_username(data->pseudonym,
+					       data->pseudonym_len)) {
 		identity = data->pseudonym;
 		identity_len = data->pseudonym_len;
 	} else {