WordPress.org

Ready to get started?Download WordPress

Codex

Attention Interested in functions, hooks, classes, or methods? Check out the new WordPress Code Reference!

Difference between revisions of "Changing File Permissions"

(Started writing this on a diff page, put it here instead!)
m (The dangers of 777: the worst that can happen)
Line 173: Line 173:
 
This provides an avenue for someone to gain access to your files by hijacking basically any process on your server, this also includes any other users on your machine. So you should think carefully about modifying permissions on your machine. I've never come across anything that needed more than 767, so when you see 777 ask why its necessary.
 
This provides an avenue for someone to gain access to your files by hijacking basically any process on your server, this also includes any other users on your machine. So you should think carefully about modifying permissions on your machine. I've never come across anything that needed more than 767, so when you see 777 ask why its necessary.
   
Its usually pretty easy to have the enhanced features provided by the impressive WordPress plugins available, without having to put yourself at risk. Contact the Plugin author or your server support and request a workaround.
+
=== The Worst Outcome ===
   
  +
The worst that can happen as a result of using 777 permissions on a folder or even a file, is that if a malicious cracker or entity is able to upload a devious file or modify a current file to execute code, they will have complete control over your blog, including having your database information and password.
  +
  +
=== Find a Workaround ===
  +
  +
Its usually pretty easy to have the enhanced features provided by the impressive WordPress plugins available, without having to put yourself at risk. Contact the Plugin author or your server support and request a workaround.
   
 
== Finding Secure File Permissions ==
 
== Finding Secure File Permissions ==

Revision as of 01:11, 9 December 2008

On computer filesystems, different files and directories have permissions that specify who and what can read, write, modify and access them. This is important because WordPress may need access to write to files in your wp-content directory to enable certain functions.


Permission Modes

  6       4     0
 user   group  world
 r+w    w   
 4+2+0  4+0+0  0+0+0  = 640

The permission mode is computed by adding up the following values for the user, the file group, and for everyone else. The diagram shows how.

  • Read 4 - Allowed to read files
  • Write 2 - Allowed to write/modify files
  • eXecute1 - Read/write/delete/modify/directory


  4      0      0
 user   group  world
 r+w      
 4+0+0  0+0+0  0+0+0  = 400


Example Permission Modes

Mode Str Perms Explanation
0477 -r--rwxrwx owner has read only (4), other and group has rwx (7)
0677 -rw-rwxrwx owner has rw only(6), other and group has rwx (7)
0444 -r--r--r-- all have read only (4)
0666 -rw-rw-rw- all have rw only (6)
0400 -r-------- owner has read only(4), group and others have no permission(0)
0600 -rw------- owner has rw only, group and others have no permission
0470 -r--rwx--- owner has read only, group has rwx, others have no permission
0407 -r-----rwx owner has read only, other has rwx, group has no permission
0670 -rw-rwx--- owner has rw only, group has rwx, others have no permission
0607 -rw----rwx owner has rw only, group has no permission and others have rwx
See full list 0000 to 0777.


Permission Scheme for WordPress

All files should be owned by your user account on your web server, and should be writable by your username. Any file that needs write access from WordPress should be group-owned by the user account used by the webserver. For example, you may have a user account that lets you FTP files back and forth to your server, but your server itself may run using a separate user, in a separate usergroup. A user such as dhapache or nobody.

The file and folder permissions of wordpress should be the same for most users, depending on the type of installation you performed and the umask settings of your system environment at the time of install.

NOTE: If you installed WordPress yourself, you likely do not need to modify file permissions. Unless you are experiencing problems with permission errors, or you want to, you probably should not mess with this.

For core WordPress files, all should be writable only by your user account. However, if you utilize mod_rewrite Permalinks or other .htaccess features you should make sure that WordPress can also write to your /.htaccess file.


If you want to use the built-in theme editor, all files need to be group writable. Try using it before modifying file permissions, it should work.

Some plugins require the /wp-content/ folder be made writeable, but in such cases they will let you know during installation. In some cases, this may require assigning 755 permissions or higher (e.g. 777 on some hosts). The same is true for /wp-content/cache/ and maybe /wp-content/uploads/

Additional directories under /wp-content/ should be documented by whatever plugin / theme requires them. Permissions will vary.

/   
|- index.php
|- wp-admin
|   `- wp-admin.css
|- wp-blog-header.php
|- wp-comments-post.php
|- wp-commentsrss2.php
|- wp-config.php
|- wp-content
|   |- cache
|   |- plugins
|   |- themes
|   `- uploads
|- wp-cron.php
|- wp-includes
`- xmlrpc.php



Using an FTP Client

FTP programs ("clients") allow you to set permissions for files and directories on your remote host. This function is often called chmod or set permissions in the program menu.

In a WordPress install, two files that you will probably want to alter are the index page, and the css which controls the layout. Here's how you change index.php - the process is the same for any file.

In the screenshot below, look at the last column - that shows the permissions. It looks a bit confusing, but for now just note the sequence of letters.

Initial permissions

Right-click 'index.php' and select 'File Permissions'
A popup screen will appear.

Altering file permissions

Don't worry about the check boxes. Just delete the 'Numeric value:' and enter the number you need - in this case it's 666. Then click OK.

Permissions have been altered

You can now see that the file permissions have been changed.


Unhide the hidden files

By default, most FTP Clients, including FileZilla, keep hidden files, those files beginning with a period (.), from being displayed. But, at some point, you may need to see your hidden files so that you can change the permissions on that file. For example, you may need to make your .htaccess file, the file that controls permalinks, writeable.

To display hidden files in FileZilla, in it is necessary to select 'View' from the top menu, then select 'Show hidden files'. The screen display of files will refresh and any previously hidden file should come into view.

To get FileZilla to always show hidden files - under Edit, Settings, Remote File List, check the Always show hidden files box.


Using the Command Line

If you have shell/SSH access to your hosting account, you can use chmod to change file permissions, which is the preferred method for experienced users. Before you start using chmod it would be recommended to read some tutorials to make sure you understand what you can achieve with it. Setting incorrect permissions can take your site offline, so please take your time.

You can make all the files in your wp-content directory writable in two steps, but before making every single file and folder writable you should first try safer alternatives like modifying just the directory. Try each of these commands first and if they dont work then go recursive, which will make even your themes image files writable. Replace DIR with the folder you want to write in

chmod 746 -v DIR
chmod 747 -v DIR
chmod 756 -v DIR
chmod 757 -v DIR
chmod 764 -v DIR
chmod 765 -v DIR
chmod 766 -v DIR
chmod 767 -v DIR

If those fail to allow you to write, try them all again in order, except this time replace -v with -R, which will recursively change each file located in the folder. If after that you still cant write, you may now try 777.


About Chmod

chmod is a unix command that means "change mode" on a file. The -R flag means to apply the change to every file and directory inside of wp-content. 766 is the mode we are changing the directory to, it means that the directory is readable and writable by WordPress and any and all other users on your system. Finally, we have the name of the directory we are going to modify, wp-content. If 766 doesn't work, you can try 777, which makes all files and folders readable, writable, and executable by all users, groups, and processes.

If you use Permalinks you should also change permissions of .htaccess to make sure that WordPress can update it when you change settings such as adding a new page, redirect, category, etc.. which requires updating the .htaccess file when mod_rewrite Permalinks are being used.


  1. Go to the main directory of WordPress
  2. Enter chmod -v 666 .htaccess
NOTE: From a security standpoint, even a small amount of protection is preferable to a world-writeable directory. Start with low permissive settings like 744, working your way up until it works. Only use 777 if necessary, and hopefully only for a temporary amount of time.


The dangers of 777

The crux of this permission issue is how your server is configured. The username you use to FTP or SSH into your server is most likely not the username used by the server application itself to serve pages.


  7      7      7
 user   group  world
 r+w+x  r+w+x  r+w+x
 4+2+1  4+2+1  4+2+1  = 777

Often the Apache server is 'owned' by the dhapache or nobody user accounts. These accounts have a limited amount of access to files on the server, for a very good reason. By setting your personal files and folders owned by your user account to be World-Writable, you are literally making them World Writable. Now the dhapache and nobody users that run your server, serving pages, executing php interpreters, etc.. will have full access to your user account files.

This provides an avenue for someone to gain access to your files by hijacking basically any process on your server, this also includes any other users on your machine. So you should think carefully about modifying permissions on your machine. I've never come across anything that needed more than 767, so when you see 777 ask why its necessary.

The Worst Outcome

The worst that can happen as a result of using 777 permissions on a folder or even a file, is that if a malicious cracker or entity is able to upload a devious file or modify a current file to execute code, they will have complete control over your blog, including having your database information and password.

Find a Workaround

Its usually pretty easy to have the enhanced features provided by the impressive WordPress plugins available, without having to put yourself at risk. Contact the Plugin author or your server support and request a workaround.

Finding Secure File Permissions

The .htaccess file is one of the files that is accessed by the owner of the process running the server. So if you set the permissions too low, than your server won't be able to access the file and will cause an error. Therein lies the method to find the most secure settings. Start too restrictive and increase the permissions until it works.


Example Permission Settings

The following example has a custom compiled php-cgi binary and a custom php.ini file located in the cgi-bin directory for executing php scripts. To prevent the interpreter and php.ini file from being accessed directly in a web browser they are protected with a .htaccess file.

Default Permissions (umask 022)

644 -rw-r--r--  /home/user/wp-config.php
644 -rw-r--r--  /home/user/cgi-bin/.htaccess
644 -rw-r--r--  /home/user/cgi-bin/php.ini
755 -rwxr-xr-x  /home/user/cgi-bin/php.cgi
755 -rwxr-xr-x  /home/user/cgi-bin/php5.cgi

Secured Permissions

600 -rw-r--r--  /home/user/wp-config.php
604 -rw----r--  /home/user/cgi-bin/.htaccess
600 -rw-------  /home/user/cgi-bin/php.ini
711 -rwx--x--x  /home/user/cgi-bin/php.cgi
100 ---x------  /home/user/cgi-bin/php5.cgi


.htaccess permissions

644 > 604 - The bit allowing the group owner of the .htaccess file read permission was removed. 644 is normally required and recommended for .htaccess files.


php.ini permissions

644 > 600 - Previously all groups and all users with access to the server could access the php.ini, even by just requesting it from the site. The tricky thing is that because the php.ini file is only used by the php.cgi, we only needed to make sure the php.cgi process had access. The php.cgi runs as the same user that owns both files, so that single user is now the only user able to access this file.


php.cgi permissions

755 > 711 This file is a compiled php-cgi binary used instead of mod_php or the default vanilla php provided by the hosting company. The default permissions for this file are 755, which


php5.cgi permissions

755 > 100 - Because of the setup where the user account is the owner of the process running the php cgi, no other user or group needs access, so we disable all access except execution access. This is interesting because it really works. You can try reading the file, writing to the file, etc.. but the only access you have to this file is to run php scripts. And as the owner of the file you can always change the permission modes back again.

$ cat: php5.cgi: Permission denied
./php5.cgi:  Welcome


See Also