Date: Mon, 21 Nov 2016 11:54:33 -0500 From: Scott Arciszewski <scott@...agonie.com> To: oss-security@...ts.openwall.com Subject: WordPress (all versions): SPOF, RCE, and Negligence This is the function that fetches downloads from the WordPress update servers: https://github.com/WordPress/WordPress/blob/f5b6731777bbd1dfe290867d2240a2a68e2f0cf1/wp-admin/includes/class-wp-upgrader.php#L252-L283 The only verification it offers is an MD5 checksum, which is sent by the server that also serves the file: https://github.com/WordPress/WordPress/blob/eeefec932f3d4f3b50369f6523c2cd8fad3d467f/wp-admin/includes/file.php#L482-L525 At no point lower in the automatic update process is a cryptographic signature verified. The update server is trusted explicitly and implicitly by every WordPress website online. WordPress powers an estimated 26% of websites on the Internet. Consequently, the WordPress update server is one of the largest single points of failure (SPOF) on the Internet. If you manage to hack their infrastructure, you can push a false update to millions of WordPress blogs and get reliable remote code execution everywhere. They are aware of this issue, and have been for years: https://core.trac.wordpress.org/ticket/25052 Additionally, PHP before 5.6.0 had terrible SSL/TLS support. It may also be possible to get targeted RCE out of a MitM condition due to their stubborn insistence on supporting PHP 5.2.4. I need to do more research here. The WordPress culture, for those who are not aware, prioritizes higher adoption rates over better security. They see backwards compatibility as a usability problem more than a liability. The WordPress team also promotes the use of the misnomer "responsible disclosure" over the more accurate "coordinated disclosure", and refuse to entertain suggestions to improve their vernacular. In short, WordPress is semi-toxic towards improving their own security-- mostly out of negligence and stubbornness rather than outright hostility (see: OpenCart). I don't believe there's much chance of fixing this, due to political problems rather than technological problems. The first step towards a reliable solution would look like this: 1. Up the minimum PHP version to at least 5.6.0. 2. Use openssl_sign() and openssl_verify() with an RSA keypair maintained by their team. A total solution would incorporate all of the elements listed here for both core updates and theme/plugin updates: https://paragonie.com/blog/2016/10/guide-automatic-security-updates-for-php-developers#elements-automatic-updates Should anyone wish to endure the steep uphill battle to try to get WordPress to fix this problem _before_ we see headlines titled "WormPress: How your blog was hacked" in the news, godspeed. Scott Arciszewski Chief Development Officer Paragon Initiative Enterprises <https://paragonie.com>
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