Bug#26585560 - MYSQL DAEMON SHOULD CREATE ITS PID FILE AS

               ROOT

DESCRIPTION
===========
If the .pid file is created at a world-writable location,
it can be compromised by replacing the server's pid with
another running server's (or some other non-mysql process)
PID causing abnormal behaviour.

ANALYSIS
========
In such a case, user should be warned that .pid file is
being created at a world-writable location.

FIX
===
A new function is_file_or_dir_world_writable() is defined
and it is called in create_pid_file() before .pid file
creation. If the location is world-writable, a relevant
warning is thrown.

NOTE
====
1. PID file is always created with permission bit 0664, so
for outside world its read-only.
2. Ignoring the case when permission is denied to get the
dir stats since the .pid file creation would fail anyway in
such a case.

1 files changed, 54 insertions, 0 deletions

diff --git a/sql-common/my_path_permissions.cc b/sql-common/my_path_permissions.cc
new file mode 100644
index 00000000000..22cd748ff03
--- /dev/null
+++ b/sql-common/my_path_permissions.cc
@@ -0,0 +1,54 @@
+/* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+
+   This program is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+   02110-1301, USA */
+
+#include "my_dir.h"
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+
+/**
+  Check if a file/dir is world-writable (only on non-Windows platforms)
+
+  @param [in] Path of the file/dir to be checked
+
+  @returns Status of the file/dir check
+    @retval -2 Permission denied to check attributes of file/dir
+    @retval -1 Error in reading file/dir
+    @retval  0 File/dir is not world-writable
+    @retval  1 File/dir is world-writable
+ */
+
+int is_file_or_dir_world_writable(const char *path)
+{
+  MY_STAT stat_info;
+  (void)path; // avoid unused param warning when built on Windows
+#ifndef _WIN32
+  if (!my_stat(path, &stat_info, MYF(0)))
+  {
+      return (errno == EACCES) ? -2 : -1;
+  }
+  if ((stat_info.st_mode & S_IWOTH) &&
+      ((stat_info.st_mode & S_IFMT) == S_IFREG ||   /* file   */
+       (stat_info.st_mode & S_IFMT) == S_IFDIR))    /* or dir */
+    return 1;
+#endif
+  return 0;
+}
+
+#ifdef  __cplusplus
+}
+#endif