Securely update wordpress instance

Background

WordPress wants you to have automatic updates turned on for your installation. According to them this is the best way to securely update wordpress. While this is party true because time is key when it comes to web security. If you have patched your installation before anyone tries to exploit the vulnerabilities you might have that’s a good thing. But the problem is that many of these vulnerabilities depend on the web server having write access to your files. And in order to have automatic updates turned on you will have to grant wordpress (the web server) write access to all files that it might want to update.

Securely update wordpress

For a long time wordpress have offered another way of semi automatically updating your wordpress, this depends on you handing over your credentials for file transfers to wordpress. What wordpress does is basically a regular login using ftp or sftp and uploading the new files this way. According to me this is a vast improvement (maybe because I’ve been the victim of wordpress “hacks” that used the possibility to change my files on disk).

But what if you only have sftp/ssh access with key? Or you dont want to give your personal password to wordpress every time you want to do upgrades?

WordPress have a built in solution for this very similar to the one described above. You can actually use ssh keys to do the upgrade.  Create a RSA key pair WITH PASS PHRASE on your web server and store it somewhere safe where only you and the httpd daemon have access to read it.

Then its time to allow this key access to your account, but please restrict access from localhost or the servers own IP. This key should never be allowed to be used from outside. Your .ssh/authorized_keys could look something like this:

[..]
from="127.0.0.1" ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC19oGbaEW7NKBQ5vn3auFbUKAasopYYPv03FxhEjbZwhoVTO44BIR0oIdMs1u1v5Y4gDH77ndCI/6fqwJQwc1D0YYH/45wUOEaB4MuPlCxlp7yxE+FyzMspi9mP8HETS+jEfzLIQ01F424yfVweQME9fxeCP0MFO+XK0SuMCk5ibdvaxYwCuRwPFkHcnyKIrDnIgGXv0D8YdC+K/RW/Ghpu9C7Rn2q0pQDbSHj7/xddO7aD+X6DPZfbHS/5ZrJnB+oWf7b9j5FmH8ldBSGBvUr6kplnDr1dKN/98bwRp1FpcxzShAX3q9nj44FwPhKV5JEOw146YJxXXks40ia1da5

Then you can configure this in wp-config.php

define('FTP_PUBKEY','/usr/local/www/ssh/updatekey.pub');
define('FTP_PRIKEY','/usr/local/www/ssh/updatekey');
define('FTP_USER','peter');
define('FTP_HOST','framkant.org');

When doing updates in the future wordpress will ask you for the pass phrase of your ssh key instead of your personal password. In this way the sensitive authentication “material” is never transferred over the internet.

There is still the possibility that malicious code in wordpress or a malicious plugin/theme could steal this key since it have read access to the private key and you give it the pass phrase. But this is still much better than giving it your password.