ecdh: Refactor ecdh_build_k to check errors codes.

src/ecdh.c

@@ -99,6 +99,7 @@ static int ecdh_build_k(ssh_session session) {
   const EC_GROUP *group = EC_KEY_get0_group(session->next_crypto->ecdh_privkey);
   EC_POINT *pubkey;
   void *buffer;
+  int rc;
   int len = (EC_GROUP_get_degree(group) + 7) / 8;
   bignum_CTX ctx = bignum_ctx_new();
   if (ctx == NULL) {
@@ -117,19 +118,48 @@ static int ecdh_build_k(ssh_session session) {
     return -1;
   }
 
-  if (session->server)
-      EC_POINT_oct2point(group,pubkey,ssh_string_data(session->next_crypto->ecdh_client_pubkey),
-              ssh_string_len(session->next_crypto->ecdh_client_pubkey),ctx);
-  else
-      EC_POINT_oct2point(group,pubkey,ssh_string_data(session->next_crypto->ecdh_server_pubkey),
-              ssh_string_len(session->next_crypto->ecdh_server_pubkey),ctx);
+  if (session->server) {
+      rc = EC_POINT_oct2point(group,
+                              pubkey,
+                              ssh_string_data(session->next_crypto->ecdh_client_pubkey),
+                              ssh_string_len(session->next_crypto->ecdh_client_pubkey),
+                              ctx);
+  } else {
+      rc = EC_POINT_oct2point(group,
+                              pubkey,
+                              ssh_string_data(session->next_crypto->ecdh_server_pubkey),
+                              ssh_string_len(session->next_crypto->ecdh_server_pubkey),
+                              ctx);
+  }
+  bignum_ctx_free(ctx);
+  if (rc <= 0) {
+      EC_POINT_clear_free(pubkey);
+      return -1;
+  }
+
   buffer = malloc(len);
-  ECDH_compute_key(buffer,len,pubkey,session->next_crypto->ecdh_privkey,NULL);
-  EC_POINT_free(pubkey);
-  BN_bin2bn(buffer,len,session->next_crypto->k);
+  if (buffer == NULL) {
+      EC_POINT_clear_free(pubkey);
+      return -1;
+  }
+
+  rc = ECDH_compute_key(buffer,
+                        len,
+                        pubkey,
+                        session->next_crypto->ecdh_privkey,
+                        NULL);
+  EC_POINT_clear_free(pubkey);
+  if (rc <= 0) {
+      free(buffer);
+      return -1;
+  }
+
+  BN_bin2bn(buffer, len, session->next_crypto->k);
   free(buffer);
+
   EC_KEY_free(session->next_crypto->ecdh_privkey);
-  session->next_crypto->ecdh_privkey=NULL;
+  session->next_crypto->ecdh_privkey = NULL;
+
 #ifdef DEBUG_CRYPTO
     ssh_print_hexa("Session server cookie",
                    session->next_crypto->server_kex.cookie, 16);
@@ -138,10 +168,6 @@ static int ecdh_build_k(ssh_session session) {
     ssh_print_bignum("Shared secret key", session->next_crypto->k);
 #endif
 
-#ifdef HAVE_LIBCRYPTO
-  bignum_ctx_free(ctx);
-#endif
-
   return 0;
 }