32 comment

1. This is not enought because you can always use “`” that will bypass these limitation.

   1. That’s not true: When shell_exec() has been disabled, the backticks are unavailable as well.
      See http://php.net/manual/en/language.operators.execution.php:
      “Note: The backtick operator is disabled when safe mode is enabled or shell_exec() is disabled.”

      1. Sorry, I overlooked the comment by “Experts” that was not filed as a reply to Davide.

2. I guess if you really need those functions, you can overwrite the configuration using ini_set function in your script to enable them for a particular site.

   1. I can’t understand if they can be re-enabled in scripts why should we disable them? hackers may use ini_set() to enable them! Or is there any restrictions/limits for hackers while calling ini_set() that I don’t know?

3. Davide you are wrong “`” using shell_exec function so if we disable shell_exec then “`” will be disabled too

4. Why is “parse_ini_file” disabled?

5. You should make sure the user cannot override the setting using .htaccess or custom php.ini

6. show_source is an alias of highlight_file.
   Why would you disable this function?
   You can read the contents of a file with readfile() or file_get_contents :/

7. readfile() and file_get_contents() functions are subject to the open_basedir restriction.
   Obviously you should set the open_basedir php setting to your docroot, so the scripts won’t be able to read files above docroot in your file system!

8. if i create a custom php.ini file, it would overwrite disable_functions directive, so this is useless.
   how can you overcome that???

9. “ubuntu lover”: Either you want to disable those functions or not. If you want you have to change php.ini: overwrite disable_functions and set a new list or modify the existing one. I’m not sure you think it makes it useless. Only the server admin can do that and he will only disable the functions he wants, editing that list.
   Also Eric says: “if you really need those functions, you can overwrite the configuration using ini_set function in your script to enable them for a particular site.” But again you can do that only on the server side.

10. this functions easily bypassed with cgi telnet perl script!

    1. So what’s the solution? To disable telnet?

       1. =S

       2. if telnet is enabled.. you need to re-assess your system security

11. it didnot work for me

12. Helo, sorry my english is not so good. My Question: How can I enable exec on Linux? Thanks for the Answers :-) Bye

13. Here is the list i use. Most script dont use any of these functions anyway (except for chmod maybe, for file management script or something).

    exec, passthru, shell_exec, system, proc_open, posix_mkfifo, pg_lo_import, dbmopen, dbase_open, popen, chgrp, chown, chmod, symlink, pcntl_exec,
    apache_child_terminate, apache_setenv, define_syslog_variables, posix_getpwuid, posix_kill, posix_mkfifo, posix_setpgid, posix_setsid, posix_setuid,
    posix_setuid, posix_uname, proc_close, pclose, proc_nice, proc_terminate, shell_exec

14. only disable those setting,it it enough ? how about the following too over ?

    disable_functions = show_source, system, shell_exec, passthru, exec, popen, proc_open, allow_url_fopen, phpinfo, gzinflate, fsockopen, pfsockopen
    

15. imo you should look limitations in wordpress not in php. It’s program not language unsafe.

16. Best one I could found is this :

    #Protect your website from Hacking using this php.ini By Mauritania Attacker

    safe_mode = On
    disable_functions = "ln, cat, popen, pclose, posix_getpwuid, posix_getgrgid, posix_kill, parse_perms, system, dl, passthru, exec, shell_exec, popen, proc_close, proc_get_status, proc_nice, proc_open, escapeshellcmd, escapeshellarg, show_source, posix_mkfifo, mysql_list_dbs, get_current_user, getmyuid, pconnect, link, symlink, pcntl_exec, ini_alter, pfsockopen, leak, apache_child_terminate, posix_kill, posix_setpgid, posix_setsid, posix_setuid, proc_terminate, syslog, fpassthru, stream_select, socket_select, socket_create, socket_create_listen, socket_create_pair, socket_listen, socket_accept, socket_bind, socket_strerror, pcntl_fork, pcntl_signal, pcntl_waitpid, pcntl_wexitstatus, pcntl_wifexited, pcntl_wifsignaled, pcntl_wifstopped, pcntl_wstopsig, pcntl_wtermsig, openlog, apache_get_modules, apache_get_version, apache_getenv, apache_note, apache_setenv, virtual, chmod, file_upload, delete, deleted, edit, fwrite, cmd, rename, unlink, mkdir, mv, touch, cp, cd, pico"
    safe_mode_gid = On
    open_basedir = On
    register_globals = Off
    exec = Off
    shell_exec = Off
    allow_url_fopen = Off
    allow_url_include = Off

17. Hello Experts,
    i have a problem i have installed mysql and lamp on my fedora linux .
    i have configured phpmyadmin also so that it can connect to the mysql socket.
    all works with http://localhost/ and http://localhost/phpmyadmin in the browser …
    but when i tried running my db.php file which contains following

    give me errors
    Warning: mysql_connect(): No such file or directory in /opt/lampp/htdocs/hellophp/index.php on line 2
    No such file or directory

    this works fine on my windows but not on linux although all configuration of lampp is fine..help

18. here is my code :

    mysql_connect(“localhost:3306″,”root”,”sach”) or die(mysql_error());
    mysql_select_db(“sample”) or die(mysql_error());

19. i have tried removing 3306 still not working
    same problem
    Warning: mysql_connect(): No such file or directory in /opt/lampp/htdocs/hellophp/index.php on line 2

20. This article is laughable at best. Sure, the functions mentioned can be used to exploit security issues, but if your server is properly configured, you shouldn’t need to do so.

    exec, passthru, shell_exec, system, proc_open and popen are all dependent on server permissions. If your server is configured properly, the user accounts should not be able to do anything dangerous with these.

    curl_exec and curl_multi_exec are both quite useful. I don’t see how these can be dangerous.

    parse_ini_file and show_source are both completely harmless. I highly recommend you read up on what these do before you go blindly recommending people disable them.

    1. Maybe these restrictions are useful on servers where different webspace users (i.e. actual people) “share” one UNIX user account (separate accounts only on the FTP server etc.). IIRC this is the case in typical Apache installations (all PHP scripts run as user “apache”, and there are no separate PHP interpreter processes being created which could get their user ID changed).
       So if PHP scripts were allowed full access, the FTP server’s restrictions would become useless. (But still then you need to disable CGI, otherwise one can upload and execute shell scripts…)

21. I use this list:

    apache_child_terminate, apache_setenv, define_syslog_variables, escapeshellarg, escapeshellcmd, eval, exec, fp, fput, ftp_connect, ftp_exec, ftp_get, ftp_login, ftp_nb_fput, ftp_put, ftp_raw, ftp_rawlist, highlight_file, ini_alter, ini_get_all, ini_restore, inject_code, openlog, passthru, php_uname, phpAds_remoteInfo, phpAds_XmlRpc, phpAds_xmlrpcDecode, phpAds_xmlrpcEncode, popen, posix_getpwuid, posix_kill, posix_mkfifo, posix_setpgid, posix_setsid, posix_setuid, posix_setuid, posix_uname, proc_close, proc_get_status, proc_nice, proc_open, proc_terminate, shell_exec, show_source, syslog, system, xmlrpc_entity_decode, ini_set
    

    Works fine.

    Thanks.

    1. php_uname is used by Composer
       openlog is used by some modules in Drupal 8

22. Why not to use mod_security2 with some good rules to protect the web site from such attacks?

23. Hi,

    Where to get good mod_secuirty2 rules ?

    Thanks.

24. Those who advising to disable ‘eval’ should read PHP documentation and understand that language instead of blindly copy-paste “smart” advises and reporting without testing that it’s “works good” for them.

    Eval – is a language construct(same as ‘echo’) and CAN NOT be disabled without third party extension such as Suhosin

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