ERP: Use macro for EMSKname length instead of hardcoded integer value

While RFC 5295 uses "8" as the value to use in the length field in KDF
context when deriving EMSKname, it is clearer to use the macro defining
EMSKname as the value since the KDF design in RFC 5295 encodes the
length of the derived data in octets in that part of the context data.
This change is just making the implementation easier to understand while
not actually changing the behavior.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/eap_peer/eap.c

@@ -526,7 +526,7 @@ static void eap_peer_erp_init(struct eap_sm *sm)
 
 	wpa_hexdump_key(MSG_DEBUG, "EAP: EMSK", emsk, emsk_len);
 
-	WPA_PUT_BE16(len, 8);
+	WPA_PUT_BE16(len, EAP_EMSK_NAME_LEN);
 	if (hmac_sha256_kdf(sm->eapSessionId, sm->eapSessionIdLen, "EMSK",
 			    len, sizeof(len),
 			    EMSKname, EAP_EMSK_NAME_LEN) < 0) {

src/eap_server/eap_server.c

@@ -452,7 +452,7 @@ static void eap_server_erp_init(struct eap_sm *sm)
 
 	wpa_hexdump_key(MSG_DEBUG, "EAP: EMSK", emsk, emsk_len);
 
-	WPA_PUT_BE16(len, 8);
+	WPA_PUT_BE16(len, EAP_EMSK_NAME_LEN);
 	if (hmac_sha256_kdf(sm->eap_if.eapSessionId, sm->eap_if.eapSessionIdLen,
 			    "EMSK", len, sizeof(len),
 			    EMSKname, EAP_EMSK_NAME_LEN) < 0) {