CDRIVER-2431 check for empty command before comparing name

Author: jmikola

src/mongoc/mongoc-client.c

@@ -1713,6 +1713,7 @@ _mongoc_client_command_with_opts (mongoc_client_t *client,
                                   bson_error_t *error)
 {
    mongoc_cmd_parts_t parts;
+   const char *command_name;
    mongoc_server_stream_t *server_stream = NULL;
    mongoc_cluster_t *cluster;
    bson_t reply_local;
@@ -1730,6 +1731,16 @@ _mongoc_client_command_with_opts (mongoc_client_t *client,
    parts.is_read_command = (mode & MONGOC_CMD_READ);
    parts.is_write_command = (mode & MONGOC_CMD_WRITE);
 
+   command_name = _mongoc_get_command_name (command);
+
+   if (!command_name) {
+      bson_set_error (error,
+                      MONGOC_ERROR_COMMAND,
+                      MONGOC_ERROR_COMMAND_INVALID_ARG,
+                      "Empty command document");
+      GOTO (err);
+   }
+
    reply_ptr = reply ? reply : &reply_local;
 
    if (mode == MONGOC_CMD_READ || mode == MONGOC_CMD_RAW) {
@@ -1783,8 +1794,7 @@ _mongoc_client_command_with_opts (mongoc_client_t *client,
       if ((mode & MONGOC_CMD_WRITE) &&
           !mongoc_write_concern_is_default (default_wc) &&
           (!opts || !bson_has_field (opts, "writeConcern"))) {
-         bool is_fam =
-            !strcasecmp (_mongoc_get_command_name (command), "findandmodify");
+         bool is_fam = !strcasecmp (command_name, "findandmodify");
 
          if ((is_fam && wire_version >= WIRE_VERSION_FAM_WRITE_CONCERN) ||
              (!is_fam && wire_version >= WIRE_VERSION_CMD_WRITE_CONCERN)) {

src/mongoc/mongoc-cmd.c

@@ -108,6 +108,7 @@ mongoc_cmd_parts_append_opts (mongoc_cmd_parts_t *parts,
                               int max_wire_version,
                               bson_error_t *error)
 {
+   const char *command_name;
    bool is_fam;
    mongoc_client_session_t *cs = NULL;
    mongoc_write_concern_t *wc;
@@ -120,8 +121,17 @@ mongoc_cmd_parts_append_opts (mongoc_cmd_parts_t *parts,
    /* not yet assembled */
    BSON_ASSERT (!parts->assembled.command);
 
-   is_fam =
-      !strcasecmp (_mongoc_get_command_name (parts->body), "findandmodify");
+   command_name = _mongoc_get_command_name (parts->body);
+
+   if (!command_name) {
+      bson_set_error (error,
+                      MONGOC_ERROR_COMMAND,
+                      MONGOC_ERROR_COMMAND_INVALID_ARG,
+                      "Empty command document");
+      RETURN (false);
+   }
+
+   is_fam = !strcasecmp (command_name, "findandmodify");
 
    while (bson_iter_next (iter)) {
       if (BSON_ITER_IS_KEY (iter, "collation")) {

tests/test-mongoc-client.c

@@ -1531,6 +1531,7 @@ static void
 test_command_empty (void)
 {
    mongoc_client_t *client;
+   mongoc_write_concern_t *wc;
    bson_error_t error;
    bool r;
 
@@ -1544,6 +1545,29 @@ test_command_empty (void)
                           MONGOC_ERROR_COMMAND_INVALID_ARG,
                           "Empty command document");
 
+   r = mongoc_client_command_with_opts (
+      client, "admin", tmp_bson ("{}"), NULL, tmp_bson ("{}"), NULL, &error);
+
+   ASSERT (!r);
+   ASSERT_ERROR_CONTAINS (error,
+                          MONGOC_ERROR_COMMAND,
+                          MONGOC_ERROR_COMMAND_INVALID_ARG,
+                          "Empty command document");
+
+   wc = mongoc_write_concern_new ();
+   mongoc_write_concern_set_w (wc, 1);
+   mongoc_client_set_write_concern (client, wc);
+
+   r = mongoc_client_write_command_with_opts (
+      client, "admin", tmp_bson ("{}"), NULL, NULL, &error);
+
+   ASSERT (!r);
+   ASSERT_ERROR_CONTAINS (error,
+                          MONGOC_ERROR_COMMAND,
+                          MONGOC_ERROR_COMMAND_INVALID_ARG,
+                          "Empty command document");
+
+   mongoc_write_concern_destroy (wc);
    mongoc_client_destroy (client);
 }