Security and Safe Mode

Security and Safe Mode Configuration Directives
Nome Padrão Modificável Changelog
safe_mode "0" PHP_INI_SYSTEM Removed in PHP 5.4.0.
safe_mode_gid "0" PHP_INI_SYSTEM Available since PHP 4.1.0. Removed in PHP 5.4.0.
safe_mode_include_dir NULL PHP_INI_SYSTEM Available since PHP 4.1.0. Removed in PHP 5.4.0.
safe_mode_exec_dir "" PHP_INI_SYSTEM Removed in PHP 5.4.0.
safe_mode_allowed_env_vars "PHP_" PHP_INI_SYSTEM Removed in PHP 5.4.0.
safe_mode_protected_env_vars "LD_LIBRARY_PATH" PHP_INI_SYSTEM Removed in PHP 5.4.0.
Para mais detalhes e definições dos modos PHP_INI_*, veja Aonde uma configuração deve ser definida.

Here's a short explanation of the configuration directives.

safe_mode boolean

Whether to enable PHP's safe mode. If PHP is compiled with --enable-safe-mode then defaults to On, otherwise Off.

Aviso

Esta funcionalidade tornou-se OBSOLETA desde o PHP 5.3.0 e foi REMOVIDA desde o PHP 5.4.0.

safe_mode_gid boolean

By default, Safe Mode does a UID compare check when opening files. If you want to relax this to a GID compare, then turn on safe_mode_gid. Whether to use UID (FALSE) or GID (TRUE) checking upon file access.

safe_mode_include_dir string

UID/GID checks are bypassed when including files from this directory and its subdirectories (directory must also be in include_path or full path must including).

As of PHP 4.2.0, this directive can take a colon (semi-colon on Windows) separated path in a fashion similar to the include_path directive, rather than just a single directory. The restriction specified is actually a prefix, not a directory name. This means that "safe_mode_include_dir = /dir/incl" also allows access to "/dir/include" and "/dir/incls" if they exist. When you want to restrict access to only the specified directory, end with a slash. For example: "safe_mode_include_dir = /dir/incl/" If the value of this directive is empty, no files with different UID/GID can be included in PHP 4.2.3 and as of PHP 4.3.3. In earlier versions, all files could be included.
safe_mode_exec_dir string

If PHP is used in safe mode, system() and the other functions executing system programs refuse to start programs that are not in this directory. You have to use / as directory separator on all environments including Windows.

safe_mode_allowed_env_vars string

Setting certain environment variables may be a potential security breach. This directive contains a comma-delimited list of prefixes. In Safe Mode, the user may only alter environment variables whose names begin with the prefixes supplied here. By default, users will only be able to set environment variables that begin with PHP_ (e.g. PHP_FOO=BAR).

Nota:

If this directive is empty, PHP will let the user modify ANY environment variable!

safe_mode_protected_env_vars string

This directive contains a comma-delimited list of environment variables that the end user won't be able to change using putenv(). These variables will be protected even if safe_mode_allowed_env_vars is set to allow to change them.

See also: open_basedir, disable_functions, disable_classes, register_globals, display_errors, and log_errors.

When safe_mode is on, PHP checks to see if the owner of the current script matches the owner of the file to be operated on by a file function or its directory. For example:

-rw-rw-r--    1 rasmus   rasmus       33 Jul  1 19:20 script.php 
-rw-r--r--    1 root     root       1116 May 26 18:01 /etc/passwd
Running script.php:
<?php
 readfile
('/etc/passwd'); 
?>
results in this error when safe mode is enabled:
Warning: SAFE MODE Restriction in effect. The script whose uid is 500 is not 
allowed to access /etc/passwd owned by uid 0 in /docroot/script.php on line 2

However, there may be environments where a strict UID check is not appropriate and a relaxed GID check is sufficient. This is supported by means of the safe_mode_gid switch. Setting it to On performs the relaxed GID checking, setting it to Off (the default) performs UID checking.

If instead of safe_mode, you set an open_basedir directory then all file operations will be limited to files under the specified directory. For example (Apache httpd.conf example):

<Directory /docroot>
  php_admin_value open_basedir /docroot 
</Directory>
If you run the same script.php with this open_basedir setting then this is the result:
Warning: open_basedir restriction in effect. File is in wrong directory in 
/docroot/script.php on line 2 

You can also disable individual functions. Note that the disable_functions directive can not be used outside of the php.ini file which means that you cannot disable functions on a per-virtualhost or per-directory basis in your httpd.conf file. If we add this to our php.ini file:

disable_functions = readfile,system
Then we get this output:
Warning: readfile() has been disabled for security reasons in 
/docroot/script.php on line 2 

Aviso

These PHP restrictions are not valid in executed binaries, of course.

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User Contributed Notes 1 note

up
-2
rayro at gmx dot de
5 years ago
Theres a failure with open_basedir and per-host configuration
in apache as described in bug #42836: http://bugs.php.net/bug.php?id=42836

I got the same errors on my development windows system and apache 2.2.4 with php 5.3.beta1.

This error (or similar) is shown:
Warning: Unknown: open_basedir restriction in effect. File(...)
is not within the allowed path(s): (� �� �@5�,�)

Fix:
  - try slashes at the end of the folder name
  or
  - put "php_admin_value open_basedir ..." at first of all in the configuration
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