ACE via file inclusion in Redirection allows admins to execute any PHP file in the filesystem (WordPress plugin)

[dxw Security <harry () dxw com>]

Details
================
Software: Redirection
Version: 2.7.3
Homepage: https://wordpress.org/plugins/redirection/
Advisory report: https://advisories.dxw.com/advisories/ace-file-inclusion-redirection/
CVE: Awaiting assignment
CVSS: 9 (High; AV:N/AC:L/Au:S/C:C/I:C/A:C)

Description
================
ACE via file inclusion in Redirection allows admins to execute any PHP file in the filesystem

Vulnerability
================



If you are logged in as an administrator on any site by using the setup page for the redirection plugin you can run 
arbitrary code and completely compromise the system.
This is done by writing the URL to redirect to in the format file://path/to/file/here. Unfortunately the plugin 
executes any PHP within that file. This means that any file with any extension on the filesystem that contains a small 
amount of user controlled data can be turned into a back door. The plugin also has the functionality to create files 
and place user controlled data in them. This results in attacker controlled code running and complete compromise of the 
system.
When the code for handling a redirect looks at the URL to redirect to it does the following:





class Pass_Action extends Red_Action {
    function process_before( $code, $target ) {
        // Determine what we are passing to: local URL, remote URL, file
        if ( substr( $target, 0, 7 ) === \'http://\' || substr( $target, 0, 8 ) === \'https://\' ) {
            echo @wp_remote_fopen( $target );
            die();
        }
        else if ( substr( $target, 0, 7 ) === \'file://\' ) {
            $parts = explode( \'?\', substr( $target, 7 ) );
            if ( count( $parts ) > 1 ) {
                // Put parameters into the environment $args = explode( \'&\', $parts[1] );
                if ( count( $args ) > 0 ) {
                    foreach ( $args as $arg ) {
                        $tmp = explode( \'=\', $arg );
                        if ( count( $tmp ) === 1 )
                            $_GET[ $arg ] = \'\';
                        else
                            $_GET[ $tmp[0] ] = $tmp[1];
                    }
                }
            }

            include( $parts[0] );
            exit();
        }
        else {
            $_SERVER[\'REQUEST_URI\'] = $target;
            if ( strpos( $target, \'?\' ) ) {
                $_SERVER[\'QUERY_STRING\'] = substr( $target, strpos( $target, \'?\' ) + 1 );
                parse_str( $_SERVER[\'QUERY_STRING\'], $_GET );
            }
        }

        return true;
    }
}







The above code behaves as expected if the url to redirect to is a HTTP or HTTPS URL.
If the URL begins with file:// it passes the path to the include function.
Its also worth mentioning that if the URL is not http, https or file, then the code allows the $_GET parameter to be 
contaminated with unescaped values, which may result in SQL injections.




Proof of concept
================

echo ‘<?php phpinfo();’ > dog-meme.jpg
Visit /wp-admin/media-new.php
Upload dog-meme.jpg
Copy the URL of the file (i.e. http://localhost/wp-content/uploads/2017/10/dog-meme.jpg)
Visit /wp-admin/tools.php?page=redirection.php
Fill “Source URL” with “/test”
Fill “Target URL” with “file:///var/www/html/wp-content/uploads/2017/10/dog-meme.jpg” (this will probably require some 
modification if your WP installation is at a different path or dog-meme.jpg is saved in a different directory)
Set “Group” to “Redirections”
Press “Add Redirect”
Press “Edit” on the newly added redirect
Press the cog icon
Set “When matched” to “Pass-through”
Press “Save”


Mitigations
================
Upgrade to version 2.8 or later.

Disclosure policy
================
dxw believes in responsible disclosure. Your attention is drawn to our disclosure policy: 
https://advisories.dxw.com/disclosure/

Please contact us on security () dxw com to acknowledge this report if you received it via a third party (for example, 
plugins () wordpress org) as they generally cannot communicate with us on your behalf.

This vulnerability will be published if we do not receive a response to this report with 14 days.

Timeline
================

2017-10-02: Discovered
2017-10-03: Reported via website contact form
2017-10-04: Response received. Plugin author reports this as intended behaviour, as
it is assumed that the administrator has full access to the system. However, also future version will include a fix.

2017-10-18: Author reported fixed in 2.8
2018-06-12: Advisory published



Discovered by dxw:
================
Glyn Wintle
Please visit advisories.dxw.com for more information.
            


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