WordPress – configuration and troubleshooting

This article will contain a number of tips and tricks when working with WordPress.

Working with permaLinks

When changing permalinks around in wp-admin, WordPress will warn you if it is unable to make the changes directly to your .htaccess file. This happens when:

- The main .htaccess file for the site is not writable by the web server user
- The Apache vhost setting, AllowOverride, is not set to 'All'
- Apache mod_rewrite may not be enabled

If wp-admin is unable to write the changes into the .htaccess, you can do this manually by:

[root@web01 ~]# vim /var/www/vhosts/example.com/.htaccess
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
# END WordPress

Password protecting wp-admin

As people can oftentimes use weak passwords for their WordPress users, it is recommended to password protect the entire wp-admin login portal with a strong password as shown below:

First create the htaccess username and password:

[root@web01 ~]# htpasswd -c /etc/httpd/conf.d/example.com-wp-admin-htpasswd your_username

Then update the .htaccess file within the wp-admin directory by:

[root@web01 ~]# vim /var/www/vhosts/example.com/wp-admin/.htaccess
<Files admin-ajax.php>
    Order allow,deny
    Allow from all
    Satisfy any
AuthType Basic
AuthName " Restricted"
AuthUserFile /etc/httpd/conf.d/example.com-wp-admin-htpasswd
Require valid-user

Disable PHP execution in uploads directory

When a site becomes compromised, malware is often uploaded that can be executed easily. Below is a common example for disabling PHP execution within the wp-content/uploads directory to help minimize the impact of a compromise:

[root@web01 ~]# vim /var/www/vhosts/example.com/wp-content/uploads/.htaccess
# Prevent PHP execution
<Files *.php>
deny from all

Blocking xmlrpc.php attacks

XML-RPC is often subjected to brute force attacks within WordPress. These attempts can create severe resource contention issues, causing performance issues for the site.

Before blocking this blindly, there are modules such as JetPack, WordPress Desktop and Mobile apps that need XML-RPC enabled. So use caution! JetPack can mitigate these brute force attacks if the option is enabled within the plugin.

First determine if xmlrpc.php is being brute forced by checking your site’s access log as shown below. Generally hundreds or thousands of these entries would be found within a short period of time.

[root@web01 ~]# tail /var/log/httpd/example.com-access.log
xxx.xxx.xxx.xxx - - [19/May/2016:15:45:02 +0000] "POST /xmlrpc.php HTTP/1.1" 200 247 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.1"
xxx.xxx.xxx.xxx - - [19/May/2016:15:45:02 +0000] "POST /xmlrpc.php HTTP/1.1" 200 247 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.1"
xxx.xxx.xxx.xxx - - [19/May/2016:15:45:03 +0000] "POST /xmlrpc.php HTTP/1.1" 200 247 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.1"

The brute force attacks against xmlrpc.php can be blocked by adding the following in the site’s .htaccess file:

[root@web01 ~]# vim /var/www/vhosts/example.com/.htaccess
# Block WordPress xmlrpc.php requests
<Files xmlrpc.php>
order allow,deny
deny from all

Force SSL on wp-admin

To force all logins for wp-admin to go over SSL, update the site’s wp-config.php with the options below. Just be sure to put this before the line “/* That’s all, stop editing! Happy blogging. */”:

[root@web01 ~]# vim /var/www/vhosts/example.com/wp-config.php
define('FORCE_SSL_LOGIN', true);
define('FORCE_SSL_ADMIN', true);
/* That's all, stop editing! Happy blogging. */

Make WordPress aware of SSL termination on the load balancer

When using SSL termination on the load balancer or perhaps through something like CloudFlare, you can sometimes create a redirect loop on the site. WordPress needs to believe that everything is really going over SSL since the load balancer is already handling that, and not the server. This can be corrected by adding the following near the top of the site’s .htaccess file:

[root@web01 ~]# vim /var/www/vhosts/example.com/.htaccess
SetEnvIf X-Forwarded-Proto https HTTPS=on

Search for outdated versions of WordPress

A primary reason why WordPress sites get compromised is due to outdated versions of the software. If a server has dozens of WordPress sites, it can be time consuming to determine what sites are running what versions. Shown below is a quick method of obtaining the versions of WordPress on the server:

[root@web01 ~]# yum install mlocate
[root@web01 ~]# updatedb
[root@web01 ~]# locate wp-includes/version.php | while read x; do echo -n "$x : WordPress Version " && egrep '^\s*\$wp_version\s*=' "$x" | cut -d\' -f2; done | column -t -s :
/var/www/vhosts/example.com/wp-includes/version.php         WordPress Version 4.3.1
/var/www/vhosts/example2.com/wp-includes/version.php        WordPress Version 4.3.3
/var/www/vhosts/example3.com/wp-includes/version.php        WordPress Version 3.9.4
/var/www/vhosts/example4.com/wp-includes/version.php        WordPress Version 3.7.1

Compare the versions returned against the following site to see how old the version is:

Error establishing a database connection

This error usually means one of three things:

- The database credentials within wp-config.php may be wrong
- The database server is busy and cannot accept additional connections
- The database itself may be corrupted

To ensure the database credentials are correct, test them by doing the following:

[root@web01 ~]# cat /var/www/vhosts/example.com/wp-config.php | grep -iE 'DB_USER|DB_PASSWORD|DB_HOST|DB_NAME'
define('DB_NAME', 'example');
define('DB_USER', 'wordpress');
define('DB_PASSWORD', 'mysecurepassword');
define('DB_HOST', 'localhost');
[root@web01 ~]# mysql -h localhost -uwordpress -pmysecurepassword
mysql> show databases;
| Database           |
| information_schema |
| example            |
2 rows in set (0.00 sec)

Confirm that Apache MaxClients does not exceed the max-connections variable within MySQL. While this example is specific for CentOS 6, it can be easily adapted for any distro. To check these variables, run the following:

[root@web01 ~]# cat /etc/httpd/conf/httpd.conf |grep MaxClients |grep -v \# | head -1
    MaxClients            63
[root@web01 ~]# mysql -e 'show variables where Variable_name like "max_connections";'
| Variable_name   | Value |
| max_connections | 65    |

Check for database corruption by adding the following before the line ‘/* That’s all, stop editing! Happy blogging. */’ in the wp-config.php:

[root@web01 ~]# vim /var/www/vhosts/example.com/wp-config.php
define( 'WP_ALLOW_REPAIR', true );

From there, do the following to repair the corruption:

- Point your browser to the following URL replacing placing the domain according:  http://www.example.com/wp-admin/maint/repair.php
- Select 'Repair database'
- Once done, remove the WP_ALLOW_REPAIR from the wp-config.php

Reset the WordPress Admin password

If you find yourself locked out of wp-admin, you can restore access to the portal by updating the active themes function.php file right after the opening comments as shown below. Just be sure to remove this code immediately after the password is updated:

[root@web01 ~]# vim /var/www/vhosts/example.com/wp-content/themes/twentyfifteen/functions.php
wp_set_password( 'your_secure_password_here', 1 );

Another way of resetting the admin password is to update MySQL directly by:

[root@web01 ~]# mysql
mysql> use your_wordpress_db_name;
mysql> UPDATE wp_users SET user_pass=MD5('your_new_password_here') WHERE user_login='admin';

Find number of SQL queries executed on each page load

To quickly determine how many queries a page is making to the database, add the following to the active theme’s footer.php near the top:

[root@web01 ~]# vim /var/www/vhosts/example.com/wp-content/themes/twentyfifteen/footer.php
<?php if ( current_user_can( 'manage_options' ) ) {
echo $wpdb->num_queries . " SQL queries performed.";
} else {
  // Uncomment the below line to show SQL queries to everybody
  echo $wpdb->num_queries . " SQL queries performed.";

This will display the query count at the bottom of every page. The public will be able to see this, so do not leave this in your footer.php longer than needed. In the example above on the second to last line, you can comment that out so only someone logged into WordPress will be able to see the results.

Enable the WordPress debug log

WordPress has the ability to log all errors, notices and warnings to a file called debug.log. This file is placed by default in wp-content/debug.log. This will hide the errors from showing up on the production site, and simply allow the developers to review them at their leisure.

To enable this, first create the log file and allow it to be writable by the web server user, then insert the following before the line ‘/* That’s all, stop editing! Happy blogging. */’ in the wp-config.php file as shown below:

[root@web01 ~]# touch /var/www/vhosts/example.com/wp-content/debug.log
[root@web01 ~]# chown apache:apache /var/www/vhosts/example.com/wp-content/debug.log
[root@web01 ~]# vim /var/www/vhosts/example.com/wp-config.php
// Enable WP_DEBUG mode
define( 'WP_DEBUG', true );

// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );

// Disable display of errors and warnings 
define( 'WP_DEBUG_DISPLAY', false );
@ini_set( 'display_errors', 0 );
/* That's all, stop editing! Happy blogging. */

Deactivating WordPress plugins

This is useful when trying to determine which plugins are causing memory leaks or overall performance issues. This should only be done after creating a backup of the database and also manually backing up the wp-content/plugins directory so a rollback option exists just in case.

Keep in mind this will break the site since you may be disabling plugins that the site requires to work.

If you prefer to disable to disable the modules one by one until the problem module is identified:

[root@web01 ~]# cd /var/www/vhosts/example.com/wp-content/plugins
[root@web01 ~]# mv akismet akismet.disabled

To disable all the modules at once, then enable them one by one after testing the site each time to see if the issue manifests, do the following:

[root@web01 ~]# mkdir /var/www/vhosts/example.com/wp-content/plugins.disabled
[root@web01 ~]# mv /var/www/vhosts/example.com/wp-content/plugins/* /var/www/vhosts/example.com/wp-content/plugins.disabled
[root@web01 ~]# cd /var/www/vhosts/example.com/wp-content/plugins
[root@web01 ~]# mv ../plugins.disabled/akismet .
[root@web01 ~]# mv ../plugins.disabled/buddypress .