It-tmiem ta' Suhosin; x'inhu l-ieħor?

Għal ħafna snin, I zealously have used Suhosin with any implementations of PHP5 on Apache2 or PHP-FPM Nginx webservers to defend against SQL injection and other common web attacks. Fil-fatt, PHP5 kien tant diżastruż, kemm f'termini ta' sigurtà ewlenija, and its functions and modules that I could have never conceived using it without any significant hardening that Suhosin provides.

As PHP5 is depreciated and my legacy programs are all gone, I am left with several implementation of PHP7 and no available Suhosin patches.

Although, it is still technically possible to add Suhosin to PHP 7.0 and 7.1 (pre-alpha – not for production), it is fair to say that the project has long been gone and PHP7 already proved that it can be troublesome like it was its predecessor. As I am thinking about a new addition to the WAF and core security of PHP7, these are some of the solutions I came with:

Disabling Bad or Unnecessary Functions

There are many risky functions built inside the PHP that are potentially dangerous and should be disabled inside ‘php.ini’ by default. You can find the config file using the below command and disable the functions via vi or nano.

php -i | grep "php.ini"

PLEASE NOTE: If you are running various versions of PHP simultaneously or the program is installed as part of another third-party application, then the chances are high that you have multiple ‘php.ini’ installed and it is not clear which one is loaded by the webserver. Make sure that you are editing the correct version (php -v).

Add the below line at the end of ‘php.ini’ file, make sure that you saved the file, and restart the webserver. You can learn about each of these PHP functions at this address. As a measured action, you may want to add them one by one to make sure that it does not negatively affect your applications.

disable_functions = popen, eval, leak, exec, shell_exec, curl_exec, curl_multi_exec, parse_ini_file, mysql_connect, system, phpinfo, escapeshellarg, escapeshellcmd, passthru, symlink, show_source, mail, sendmail, proc_open, proc_nice, proc_terminate, proc_get_status, proc_close, pfsockopen, posix_kill, posix_mkfifo, posix_setpgid, posix_setsid, posix_setuid

Disabling Register Globals and Base64

Register Global is a function by PHP that allows input arrays to the URL to be converted to variable inside your code. Therefore, any potentially vulnerable code can be exploited by an attacker who can pass malicious arrays using HTTP GET or POST requests.

Register Globals can be easily disabled by adding the below line at the end of ‘php.ini’. Do not forget to restart the webserver to execute the changes.

register_globals = Off

Just like Register Globals, Base64 is another often unnecessary feature that open the door into malicious back-doors. You can disable Base64 decoder permanently by adding the below line to the end of ‘php.ini’.

base64_decode = Off