erp: remove 'complete' callback

Since ERP is only used for FILS and not behaving in the 'normal' ERP
fashion (dealing with actual EAP data, timeouts etc.) we can structure
ERP as a more synchronous protocol, removing the need for a complete
callback.

Now, erp_rx_packet returns a status, so FILS can decide how to handle
any failures. The complete callback was also removed in favor of a
getter for the RMSK (erp_get_rmsk). This allows FILS to syncronously
handle ERP, and potentially fail directly in fils_rx_authenticate.

src/erp.c

@@ -26,6 +26,7 @@
 
 #include <stdint.h>
 #include <stdio.h>
+#include <errno.h>
 
 #include <ell/ell.h>
 
@@ -50,11 +51,11 @@ struct erp_cache_entry {
 
 struct erp_state {
 	erp_tx_packet_func_t tx_packet;
-	erp_complete_func_t complete;
 	void *user_data;
 
 	struct erp_cache_entry *cache;
 
+	uint8_t rmsk[64];
 	uint8_t r_rk[64];
 	uint8_t r_ik[64];
 	char keyname_nai[254];
@@ -330,7 +331,7 @@ static bool erp_derive_reauth_keys(const uint8_t *emsk, size_t emsk_len,
 
 struct erp_state *erp_new(struct erp_cache_entry *cache,
 				erp_tx_packet_func_t tx_packet,
-				erp_complete_func_t complete, void *user_data)
+				void *user_data)
 {
 	struct erp_state *erp;
 
@@ -340,7 +341,6 @@ struct erp_state *erp_new(struct erp_cache_entry *cache,
 	erp = l_new(struct erp_state, 1);
 
 	erp->tx_packet = tx_packet;
-	erp->complete = complete;
 	erp->user_data = user_data;
 	erp->cache = cache;
 
@@ -398,12 +398,11 @@ bool erp_start(struct erp_state *erp)
 	return true;
 }
 
-void erp_rx_packet(struct erp_state *erp, const uint8_t *pkt, size_t len)
+int erp_rx_packet(struct erp_state *erp, const uint8_t *pkt, size_t len)
 {
 	struct erp_tlv_iter iter;
 	enum eap_erp_cryptosuite cs;
 	uint8_t hash[16];
-	uint8_t rmsk[64];
 	char info[256];
 	char *ptr = info;
 	const uint8_t *nai = NULL;
@@ -425,7 +424,7 @@ void erp_rx_packet(struct erp_state *erp, const uint8_t *pkt, size_t len)
 	type = pkt[4];
 
 	if (type != ERP_TYPE_REAUTH)
-		return;
+		goto eap_failed;
 
 	r = util_is_bit_set(pkt[5], 0);
 	if (r)
@@ -505,15 +504,18 @@ void erp_rx_packet(struct erp_state *erp, const uint8_t *pkt, size_t len)
 	ptr += 2;
 
 	hkdf_expand(L_CHECKSUM_SHA256, erp->r_rk, erp->cache->emsk_len,
-			info, ptr - info, rmsk, erp->cache->emsk_len);
+			info, ptr - info, erp->rmsk, erp->cache->emsk_len);
 
-	erp->complete(ERP_RESULT_SUCCESS, rmsk, erp->cache->emsk_len,
+	return 0;
-			erp->user_data);
-
-	return;
 
 eap_failed:
-	erp->complete(ERP_RESULT_FAIL, NULL, 0, erp->user_data);
+	return -EINVAL;
+}
+
+void erp_get_rmsk(struct erp_state *erp, void **rmsk, size_t *rmsk_len)
+{
+	*rmsk = erp->rmsk;
+	*rmsk_len = erp->cache->emsk_len;
 }
 
 void erp_init(void)

src/erp.h

@@ -30,16 +30,16 @@ enum erp_result {
 
 typedef void (*erp_tx_packet_func_t)(const uint8_t *erp_data, size_t len,
 					void *user_data);
-typedef void (*erp_complete_func_t)(enum erp_result result, const void *rmsk,
-					size_t rmsk_len, void *user_data);
 
 struct erp_state *erp_new(struct erp_cache_entry *cache,
 				erp_tx_packet_func_t tx_packet,
-				erp_complete_func_t complete, void *user_data);
+				void *user_data);
 void erp_free(struct erp_state *erp);
 
 bool erp_start(struct erp_state *erp);
-void erp_rx_packet(struct erp_state *erp, const uint8_t *erp_data, size_t len);
+int erp_rx_packet(struct erp_state *erp, const uint8_t *erp_data, size_t len);
+
+void erp_get_rmsk(struct erp_state *erp, void **rmsk, size_t *rmsk_len);
 
 void erp_cache_add(const char *id, const void *session_id, size_t session_len,
 			const void *emsk, size_t emsk_len,

src/fils.c

@@ -119,10 +119,9 @@ static void fils_erp_tx_func(const uint8_t *eap_data, size_t len,
 	fils->auth(data, ptr - data + tlv_len, fils->user_data);
 }
 
-static void fils_erp_complete(enum erp_result result, const void *rmsk,
+static int fils_derive_key_data(struct fils_sm *fils, const void *rmsk,
-				size_t rmsk_len, void *user_data)
+				size_t rmsk_len)
 {
-	struct fils_sm *fils = user_data;
 	struct ie_tlv_builder builder;
 	uint8_t key[FILS_NONCE_LEN * 2];
 	uint8_t key_data[64 + 48 + 16]; /* largest ICK, KEK, TK */
@@ -134,11 +133,6 @@ static void fils_erp_complete(enum erp_result result, const void *rmsk,
 	bool sha384;
 	unsigned int ie_len;
 
-	if (result != ERP_RESULT_SUCCESS) {
-		fils_failed(fils, MMPDU_STATUS_CODE_UNSPECIFIED, false);
-		return;
-	}
-
 	/*
 	 * IEEE 802.11ai - Section 12.12.2.5.3
 	 */
@@ -241,6 +235,8 @@ static void fils_erp_complete(enum erp_result result, const void *rmsk,
 			FILS_NONCE_LEN * 2, fils->user_data);
 
 	fils->in_auth = false;
+
+	return 0;
 }
 
 struct fils_sm *fils_sm_new(struct handshake_state *hs,
@@ -259,8 +255,7 @@ struct fils_sm *fils_sm_new(struct handshake_state *hs,
 	fils->hs = hs;
 	fils->in_auth = true;
 
-	fils->erp = erp_new(hs->erp_cache, fils_erp_tx_func,
+	fils->erp = erp_new(hs->erp_cache, fils_erp_tx_func, fils);
-				fils_erp_complete, fils);
 
 	return fils;
 }
@@ -294,6 +289,8 @@ void fils_rx_authenticate(struct fils_sm *fils, const uint8_t *frame,
 	const uint8_t *session = NULL;
 	const uint8_t *wrapped = NULL;
 	size_t wrapped_len = 0;
+	void *rmsk;
+	size_t rmsk_len;
 
 	if (!hdr) {
 		l_debug("Auth frame header did not validate");
@@ -353,9 +350,13 @@ void fils_rx_authenticate(struct fils_sm *fils, const uint8_t *frame,
 
 	memcpy(fils->anonce, anonce, FILS_NONCE_LEN);
 
-	erp_rx_packet(fils->erp, wrapped, wrapped_len);
+	if (erp_rx_packet(fils->erp, wrapped, wrapped_len) < 0)
+		goto auth_failed;
+
+	erp_get_rmsk(fils->erp, &rmsk, &rmsk_len);
+
+	fils_derive_key_data(fils, rmsk, rmsk_len);
 
-	/* EAP should now call the key materials callback, giving us the rMSK */
 	return;
 
 auth_failed: