EAP-FAST peer: Stop immediately on key derivation failure

If key derivation fails, there is no point in trying to continue
authentication. In theory, this could happen if memory allocation during
TLS PRF fails.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/eap_peer/eap_fast.c

@@ -267,8 +267,8 @@ static int eap_fast_derive_msk(struct eap_fast_data *data)
 }
 
 
-static void eap_fast_derive_key_auth(struct eap_sm *sm,
-				     struct eap_fast_data *data)
+static int eap_fast_derive_key_auth(struct eap_sm *sm,
+				    struct eap_fast_data *data)
 {
 	u8 *sks;
 
@@ -281,7 +281,7 @@ static void eap_fast_derive_key_auth(struct eap_sm *sm,
 	if (sks == NULL) {
 		wpa_printf(MSG_DEBUG, "EAP-FAST: Failed to derive "
 			   "session_key_seed");
-		return;
+		return -1;
 	}
 
 	/*
@@ -294,11 +294,12 @@ static void eap_fast_derive_key_auth(struct eap_sm *sm,
 	data->simck_idx = 0;
 	os_memcpy(data->simck, sks, EAP_FAST_SIMCK_LEN);
 	os_free(sks);
+	return 0;
 }
 
 
-static void eap_fast_derive_key_provisioning(struct eap_sm *sm,
-					     struct eap_fast_data *data)
+static int eap_fast_derive_key_provisioning(struct eap_sm *sm,
+					    struct eap_fast_data *data)
 {
 	os_free(data->key_block_p);
 	data->key_block_p = (struct eap_fast_key_block_provisioning *)
@@ -307,7 +308,7 @@ static void eap_fast_derive_key_provisioning(struct eap_sm *sm,
 				    sizeof(*data->key_block_p));
 	if (data->key_block_p == NULL) {
 		wpa_printf(MSG_DEBUG, "EAP-FAST: Failed to derive key block");
-		return;
+		return -1;
 	}
 	/*
 	 * RFC 4851, Section 5.2:
@@ -326,15 +327,19 @@ static void eap_fast_derive_key_provisioning(struct eap_sm *sm,
 	wpa_hexdump_key(MSG_DEBUG, "EAP-FAST: client_challenge",
 			data->key_block_p->client_challenge,
 			sizeof(data->key_block_p->client_challenge));
+	return 0;
 }
 
 
-static void eap_fast_derive_keys(struct eap_sm *sm, struct eap_fast_data *data)
+static int eap_fast_derive_keys(struct eap_sm *sm, struct eap_fast_data *data)
 {
+	int res;
+
 	if (data->anon_provisioning)
-		eap_fast_derive_key_provisioning(sm, data);
+		res = eap_fast_derive_key_provisioning(sm, data);
 	else
-		eap_fast_derive_key_auth(sm, data);
+		res = eap_fast_derive_key_auth(sm, data);
+	return res;
 }
 
 
@@ -1586,7 +1591,14 @@ static struct wpabuf * eap_fast_process(struct eap_sm *sm, void *priv,
 			} else
 				data->anon_provisioning = 0;
 			data->resuming = 0;
-			eap_fast_derive_keys(sm, data);
+			if (eap_fast_derive_keys(sm, data) < 0) {
+				wpa_printf(MSG_DEBUG,
+					   "EAP-FAST: Could not derive keys");
+				ret->methodState = METHOD_DONE;
+				ret->decision = DECISION_FAIL;
+				wpabuf_free(resp);
+				return NULL;
+			}
 		}
 
 		if (res == 2) {