Safe Mode

[Ilia A.]

In the process of writing an installer in PHP for one of my projects I've come
in contact with a number of servers running PHP with safe_mode enabled.

As you can probably imagine the installer at first broke completely because of
safe_mode restrictions. Despite the restriction I was able to write php code
that was able to bypass safe_mode restriction in every single case, which
should tell you just how "safe" that option is.

There are numerous ways to bypass it, rely on file system utils if they are in
the path, make the script copy itself and then write stuff as webserver,
install a small script into cgi-bin directory that will do the same thing
etc...
The number of ways to bypass this feature are too numerous to list here.

I should also point out that safe_mode implementation has numerous bugs in
every PHP version including the very latest CVS.

It is my belief that safe_mode gives people who use false sense of security by
"supposedly" securing their webserver from their own users, which is
pointless since a "dedicated user" can cause plenty of damage by using
while(1) include $PHP_SELF; etc...
In addition safe_mode makes the developer life extremely difficult since it
blocks the most common operations that ARE ALLOWED by the webserver's file
permissions, why does PHP take on the role that is not done in any other
programming language?
It is nearly impossible to write a PHP file system code that would work with
safe_mode it is much easier to just release C/Perl/Python etc.. code that
will do the very same thing and run via a command line or the user's cgi-bin
directory.
For example, if a user uploads test.php with their FTP and test.php creates a
file, it will no longer be able to read that file under safe_mode since the
uid of the script and the file it created differ.

IMHO safe_mode should be removed from the php core, because it lulls web
server admins into false sense of security thus not taking the time to setup
proper file system permissions in addition to severely crippling the PHP's
file system functionality.

If the safe_mode like functionality remains it should simply block all file
system and shell execution code since with it most of that code becomes
useless anyway.

Regards,

Ilia

[Rasmus Lerdorf]

> If the safe_mode like functionality remains it should simply block all file
> system and shell execution code since with it most of that code becomes
> useless anyway.

It already does this. You can only execute things in the
safe_mode_exec_dir.

-Rasmus

[Stig S. Bakken]

I'm +1 on removing safe mode in PHP 5, and encourage the use of
system-level sandboxes/prisons instead.

- Stig

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