Thursday, April 17, 2008

Secure Joomla file permissions - Linux with Apache

Joomla allows web based installation of extensions, because of this, on most Joomla setups I've looked at, the method of allowing PHP to install the Joomla extensions is to allow global write access (chmod 777) to the Joomla installation directories. This is not a secure way of managing a Joomla site.

A secure website should not have any folders or files with global write access, especially on shared servers, yet on 90% of Joomla websites I've looked at, this is the case.

An example is when you install community builder, probably the most used Joomla 3rd party extension. If Community Builder tries to write to the /images folder but fails to do so during installation, it will spit out, "You must chmod 777 your images folder", I forget the exact sentence.

So why do you open up global write access? The reason is that your ftp or shell account user is different from the PHP user. When PHP executes, it executes under a certain user, by default the Apache user which can be "apache" or "www-data" or something else depending on the Apache settings. So if a you have a folder that has permissions 0755, and is owned by "joe", apache cannot write to this folder because it has insufficient permissions.

Ways of enabling PHP to write to Joomla installation folders

  1. Change folder permission to 0777
  2. 0755 permissions, change owner to www-data and group to users
  3. 0755 permissions, change file group to apache group

In which cases would you use each permission setting?

Change folder permission to 0777

chmod 0777 path/to/folder
If you are on a shared server, then your only choice is (1) to chmod the folders to 0777. Only the root user can chown folders and files. Since most hosting accounts are on shared servers, the majority of Joomla sites (and other CMSs) will have installation folders with 0777 perms.

0755 permissions, change owner to www-data and group to users

chown www-data:users path/to/folder
This is probably the most recommended setting. This allows Apache to read and write from the folder since it is the owner of the folder, yet also allows users in the group "users" to write to the folder. Thefore, if your FTP users are under the group "users" they will be able to update files, while the Joomla installer will be able to install and update components.

0755 permissions, change file group to apache group

chown joe:www-data path/to/folder
This isn't the normally recommended way, but it is what I normally do. This permission setting allows only the user "joe" to write to the folder and not every other user. It also allows apache to write to the folder. So only joe can ftp into this folder and write as opposed to method (1) where any user in the group "user" can write to the folder via ftp. (this doesn't prevent anyone from using apache to write to that folder however).

How to install Joomla extensions on a shared server without giving global write access

  1. Install Extensions Manually via FTP and MySQL Queries
  2. Chmod 0777 only for the installation period, then chmod back to 0755

Install Extensions Manually via FTP and MySQL Queries

This allows you to install the extension, but if the extension wants to write to a folder later, you still have the permission problem since the folder is owned by your FTP user. However, it is good to know how to do this, since it can be a method if combined with other methods. If you have shell access this is easier. See my post on remotely installing Joomla, and use this for extensions. For the mysql portion, you need to retrieve the mysql queries from extensions XML install file and run those queries against your Joomla database. Then you also have to manually add the entry in the extension table, whether the components, modules or mambot table for that extension.

Chmod 0777 only for the installation period, then chmod back to 0755

I've written a PHP Shell script for this that you can run in the command line if you have Shell access to your server.

#!/usr/bin/php
<?php

// joomla extension folders, add more folders here if you need.
$folders = array(
 'media',
 'components',
 'modules',
 'templates',
 'mambots',
 'administrator/templates', 
 'administrator/components',
 'administrator/modules',
 'images',
 'images/stories'
);

// get Joomla directory
fputs(STDOUT, "Please enter the path to the Joomla directory: ");
$jpath = trim(fgets(STDIN));
// check for ending slash
if ($jpath[strlen($jpath)-1] != '/') {
 $jpath .= '/';
}
// make sure path exists
if (!is_dir($jpath)) {
 fputs(STDOUT, "$jpath is not a valid joomla directory");
 return 1;
} else {
 // check for each folder
 foreach($folders as $folder) {
  if (!is_dir($jpath.$folder)) {
   fputs(STDOUT, "Error: A required Joomla folder $jpath$folder was not found. \n");
   return 1;
  }
 }
}

fputs(STDOUT, "Joomla directory set to: $jpath \n");

// allow global write access on joomla extensions folders
foreach($folders as $folder) {
 fputs(STDOUT, "Unsecuring: $jpath$folder \n");
 if (!chmod($jpath.$folder, 0777)) {
  fputs(STDOUT, "Error: Could not change permissions on $jpath$folder. Please chmod 0777 $jpath$folder manually. \n");
 }
}

fputs(STDOUT, "Joomla directories are ready for writing. You can install your extension \n");
fputs(STDOUT, "Press any key when you complete your installation to secure Joomla again... \n");
$enter = trim(fgets(STDIN));

// remove global write access on joomla extensions folders
foreach($folders as $folder) {
 fputs(STDOUT, "Securing: $jpath$folder \n");
 if (!chmod($jpath.$folder, 0755)) {
  fputs(STDOUT, "Error: Could not change permissions on $jpath$folder. Please chmod 0755 $jpath$folder manually to secure.\n");
 }
}
fputs(STDOUT, "Joomla install directories secured. \n");

return 0;

?>
To run it, save it to a location on your joomla server, name it something like joomla_exts.php and invoke it in the shell with:
./joomla_exts.php
The script will prompt you for the Joomla folder, then it will chmod each installation directory to 0777, and tell you to make the component install. So you just install the component in the Joomla web based installer. After installation, just hit enter in the shell script to secure the Joomla installation directory again. This works better then that above method, since all folders will be 0755 after installing the component, but the folders created by the component will be owned by the apache user, allowing the component to write to them. Make sure you don't leave this script in the web root. Keep it under the web root, or delete it after use.

If you're totally lost, here is a bit on file permissions in Linux. Here is a very good article on setting up Apache including file permissions and virtual hosts.

1 comment:

bucabay said...

This post applies mostly to Joomla1.0. In Joomla1.5, you can choose to have Joomla access the file system via FTP. Choose this option to overcome the headache of non-ownership of files.