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ParoX
Asked: 2010-12-14 18:13:09 +0800 CST

Stopping PHP ability to read/write other PHP files

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I host a very small hosting site that hosts a type of chat software. I give each user a /home/ jailed ftp but they have their own www folder they can upload things to.

One of my users uploaded this php file: http://pastebin.com/YAJW8weh - which seems to be able to save php files and allow him to download them.

Using this I think he was able to access some of my files and one of my php files had my MySQL password in the php, which he then gained access to a database with all my clients passwords.

How can I stop this from happening again? What precautions should I take when giving users their own /home/ directory.

linux php apache-2.2 security permissions

3 Answers

  1. You'll have to protect your website and Linux/Unix does this very well, set minimal permissions for group and others on your website's root directory:

    chmod 0711 /var/virtualhosts/example.com

# ls -ald /var/virtualhosts/example.com
drwx--x--x  4 example    example    4096 Oct  9 08:43 example.com

    Restrict access to files in PHP with open_basedir:

    # virtual host config
php_admin_value open_basedir "/var/virtualhosts/example.com:/tmp"

# directory config
<Directory /home/bad_user>
    php_admin_value open_basedir "/home/bad_user:/tmp"
</Directory>

    Disable dangerous functions from PHP:

    # /etc/php.ini
disable_functions = "dl,shell_exec,passthru,exec,
                    popen,system,proc_terminate,proc_close,stream_socket_server"

    Use su - user to test permissions they have on your website.

    su - apache -s /bin/bash 
cd /var/virtualhosts/example.com
ls -al
cat /var/virtualhosts/example.com/db.config.php
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  2. Best Answer

    You want to disable php for the home folder.

    When using PHP as an Apache module (default on Ubuntu 10.04), add the following to your Apache configuration

    <Directory /home>
  php_admin_value engine Off
</Directory>

    You should probably also use Options -ExecCGI and AllowOverride None there for safety. See the official Apache security tips. If your webserver have other kinds of scripts enabled (like mod_perl), be sure to disable them for the home folder too.

    • 0

  3. suPHP is really your best bet here. You would setup each user to run their scripts as their own user, then chmod their directories so that other users cannot read them. Do not rely on open_basedir, it's not going to work 100%.

    Since you are allowing uploads, you are always going to have to worry about people uploading things they shouldn't. I'd suggest running something like Linux Malware Detect. It alerts you when things like shells and DoS scripts get uploaded to your servers.

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