Junos OS PHPRC Environment Variable Manipulation RCE

Description

This module exploits a PHP environment variable manipulation vulnerability affecting Juniper SRX firewalls and EX switches. The affected Juniper devices run FreeBSD and every FreeBSD process can access their stdin by opening /dev/fd/0. The exploit also makes use of two useful PHP features. The first being 'auto_prepend_file' which causes the provided file to be added using the 'require' function. The second PHP function is 'allow_url_include' which allows the use of URL-aware fopen wrappers. By enabling allow_url_include, the exploit can use any protocol wrapper with auto_prepend_file. The module then uses data:// to provide a file inline which includes the base64 encoded PHP payload.

By default this exploit returns a session confined to a FreeBSD jail with limited functionality. There is a datastore option 'JAIL_BREAK', that when set to true, will steal the necessary tokens from a user authenticated to the J-Web application, in order to overwrite the root password hash. If there is no user authenticated to the J-Web application this exploit will try to create one. If unsuccesfull this method will not work. The module then authenticates with the new root password over SSH and then rewrites the original root password hash to /etc/master.passwd. There is an option to set allow ssh root login, if disabled.