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Bug #52587 Clearstatcache() has no effect
Submitted: 2010-08-12 03:20 UTC Modified: 2010-08-12 11:14 UTC
Votes:4
Avg. Score:4.5 ± 0.9
Reproduced:2 of 2 (100.0%)
Same Version:1 (50.0%)
Same OS:0 (0.0%)
From: a-krcrai at microsoft dot com Assigned: pajoye
Status: Assigned Package: *Directory/Filesystem functions
PHP Version: 5.3.3 OS: Windows
Private report: No CVE-ID:
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 [2010-08-12 03:20 UTC] a-krcrai at microsoft dot com
Description:
------------
The results of is_readable() and is_writable() are being cached from the first result on a filesystem object regardless of whether or not clearstatcache() is used or in what form (arguments supplied, etc).  This has only been tested on the Windows build of PHP 5.3.3 via the CLI.  It's possible that other functions are being improperly cached as well, but I haven't had time to test for all of them as of yet.

This does *not*, however, occur in the corresponding Windows builds of PHP 5.3.2.  In that version, no caching took place on either of those functions at all.

You can easily reproduce this issue if you're running Windows ACL-related tests on the filesystem in PHP 5.3.3.  The sample script I put together requires the use of SetACL (better cross-Windows version portability; http://setacl.sourceforge.net) to alter the file permissions.  Relative to the test script, create a directory named "testdir", then touch a file within that directory and name it "testfile".  We will be using that file for our test.


This bug occurs on the ZIP-build of PHP 5.3.3 (both nts and zts) run via CLI without any extensions loaded.  It has been successfully reproduced in Windows XP, Windows 2003, Windows 2003 R2, Windows Vista/7, Windows 2008, and Windows 2008 R2.  Has not been tested on Linux.


Test script:
---------------
<?php

exec( "setacl.exe -on testdir -ot file -actn setprot -op \"dacl:p_nc;sacl:p_nc\" -rec cont_obj" );  //Isolate from any perms inherited from parent.
exec( "setacl.exe -on testdir -ot file -actn clear -clr DACL -rec cont_obj" );  //Clear any remaining perms.
exec( "setacl.exe -on testdir -ot file -actn ace -ace \"n:Everyone;m:grant;p:full\"" );  //Ensures that the parent dir perms won't affect the results.

exec( "setacl.exe -on testdir/testfile -ot file -actn ace -ace \"n:Everyone;m:deny;p:full\"" );

var_dump( is_readable( "testdir/testfile" ) );
var_dump( is_writable( "testdir/testfile" ) );

//Tried different variations of clearstatcache() by themselves and combined.  Made no difference either way.  Using sleep() after setacl call made no difference, either.
clearstatcache();
clearstatcache( TRUE, "testdir/testfile" );

exec( "setacl.exe -on testdir/testfile -ot file -actn clear -clr DACL" );
exec( "setacl.exe -on testdir/testfile -ot file -actn ace -ace \"n:Everyone;m:grant;p:full\"" );

/* Copy these two var_dumps into a separate PHP file and execute it immediately after this script....  You'll see the correct bool(true) results then.  
 * You can also achieve that result by calling that separate script from this one via an exec() call (but not as an include).  --Kris */
var_dump( is_readable( "testdir/testfile" ) );
var_dump( is_writable( "testdir/testfile" ) );


Expected result:
----------------
bool(false)
bool(false)
bool(true)
bool(true)


Actual result:
--------------
bool(false)
bool(false)
bool(false)
bool(false)


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 [2010-08-12 04:42 UTC] kalle@php.net
-Status: Open +Status: Feedback
 [2010-08-12 04:42 UTC] kalle@php.net
Just did a test following the steps from your comment, my results are so far:

php-trunk, VC9, x86, ZTS/NTS:
bool(true)
bool(true)
bool(true)
bool(true)

php-53, VC9, x86, ZTS/NTS:
bool(true)
bool(true)
bool(true)
bool(true)


I interpreted your steps as:
1) mkdir testdir
2) php -r "file_put_contents('./testdir/testfile', 'PHP on Windows');"
3) Make a php file with the above code inside
4) php bug52587.php

About ACL:
C:\php>setacl -help
SetACL by Helge Klein

Homepage:        http://setacl.sourceforge.net
Version:         2.0.3.0
Copyright:       Helge Klein
License:         GPL



Did you use VC6 or VC9 binaries for your testing?
 [2010-08-12 04:53 UTC] a-krcrai at microsoft dot com
-Status: Feedback +Status: Open
 [2010-08-12 04:53 UTC] a-krcrai at microsoft dot com
If you're getting all true dumps, then that means that either you're using 5.2.x (which I'm assuming you're not), or it means that the directory/file exists but that the permissions aren't being successfully applied (or some other weird ACL issue on your system).

This is because, even if you couldn't reproduce the bug, you should still be getting false for the first two results, since full access is being denied (meaning the file should be neither readable nor writable).

Fortunately, debugging this is pretty simple.  I'd like you to do two things for me, if you don't mind:

1. Pipe the exec calls to an array (see php.net/exec for details on how to do this), then do a print_r() of said array and paste the output of that here.  This will show us if SetACL is having trouble setting the permissions on your system.

2. *Either*:

After the first pair of var_dumps, go ahead and temporarily toss in a die() statement and re-run the script.  Then, from the command-line, type "notepad testdir/testfile".  If the SetACL calls executed properly, this should pop-up a Notepad window with an "Access Denied" popup message.  If, on the other hand, Notepad loads your file just fine, then that means the file is readable and thus the ACL permissions were never applied.

*Or*:

If you have Powershell installed, open that and CD to whatever directory your PHP script is in.  Then type "get-acl testdir/testfile | format-list" and paste the output here.
 [2010-08-12 04:54 UTC] a-krcrai at microsoft dot com
Oh, and this was reproduced on both VC6 and VC9 I'm pretty sure.
 [2010-08-12 11:14 UTC] pajoye@php.net
-Status: Open +Status: Assigned -Assigned To: +Assigned To: pajoye
 [2010-08-12 11:14 UTC] pajoye@php.net
Will double check that with Kris once I'm back.
 [2013-01-31 15:19 UTC] snooops84 at googlemail dot com
Hello,
im able to reproduce this on Debian 6 (Linux some 2.6.32-5-amd64 #1 SMP Sun Sep 
23 10:07:46 UTC 2012 x86_64 GNU/Linux) with PHP 5.3.3-7+squeeze14.

getfacl meyer.txt
user:www-data:rwx		#effective:r--

my test.php
if (is_writable('meyer.txt')) {
        echo 'writeable';
}
else {
        echo 'not writeable';
}


if i execute this with su - www-data -s /bin/bash i get "not writeable", but if 
i try to move it by hand with as www-data with mv meyer.txt foo.txt it works! i 
get the same behavior with fopen (it returns false).
 
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