PHP Security: Limit Resources Used By Script

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How do I control and put limits on php scripts such as maximum execution time of each script and upload file size?

PHP supports the following resource limits directives in php.ini file:

  1. max_execution_time : Maximum execution time of each script, in seconds.
  2. max_input_time : Maximum amount of time each script may spend parsing request data.
  3. memory_limit : Maximum amount of memory a script may consume.

PHP limits

Edit /etc/php.ini or /etc/php/7.0/fpm/php.ini (fpm-php 7 config), enter:
# vi /etc/php.ini
OR
# vi /etc/php/7.0/fpm/php.ini
Set up values as follows:

max_execution_time =  30
max_input_time = 30
memory_limit = 40M

Set maximum size of POST data that PHP will accept:

post_max_size = 8M

Set maximum allowed size for uploaded files:

upload_max_filesize = 2M

Turn on or off HTTP file uploads (disallow uploading unless necessary):

file_uploads = Off

Make sure PHP redirects appropriately with the following:

cgi.force_redirect = 0

Disable file requests as fopen calls with the following

allow_url_fopen = Off

Turn on SQL safe mode:

sql.safe_mode = On

If you set sql.safe_mode, you need to set the following too:
mysqli.default_host = "192.168.1.252"
mysqli.default_port = "3306"
mysqli.default_user = "userNameHere"
mysqli.default_pw = "PasswordHere"

Now your Perl/Php/Python scripts can directly connect to the database without passing host,user and password information. Next, reload Apache web server:
# service httpd reload
OR
Reload lighttpd web server:
# /etc/init.d/lighttpd reload
OR reload php7.0-fpm:
# /etc/init.d/php7.0-fpm reload
OR use systemctl command:
# systemctl reload php7.0-fpm
Note any attempt to exceed these limits will result in a “500 Server Error”. For more information see Linux: 25 PHP Security Best Practices For Sys Admins

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

6 comment

  1. @vivek, do you personally use ‘vi’ to edit files ???? vi sucks. vim rocks.

    BTW, isn’t this very basic ? Somebody who reads the manual well b4 setup, knows this. But its funny that there are ppl who don’t do that LOL.

  2. @vivek, vi is ok for editing simple config files. but its WORST for editing config files like those of apache. vi cannot highlight whereas vim can.

    vi is not always symlinked to vim. in my system (Arch) its linked to ex. and it sucks to core.
    I’ve removed it, and set $EDITOR globally to vim. even on my VPS I use vim instead of vi. :)

    BTW, where’s the global comment feed ?

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