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Bug #68926 is_writable returns false but file_put_contents works
Submitted: 2015-01-27 21:38 UTC Modified: 2017-10-24 05:46 UTC
Votes:14
Avg. Score:4.4 ± 0.7
Reproduced:13 of 13 (100.0%)
Same Version:1 (7.7%)
Same OS:3 (23.1%)
From: lukyer at gmail dot com Assigned: ab (profile)
Status: Assigned Package: *Directory/Filesystem functions
PHP Version: 5.6Git-2015-01-27 (Git) OS: Windows 8 64b Prof.
Private report: No CVE-ID: None
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 [2015-01-27 21:38 UTC] lukyer at gmail dot com
Description:
------------
When samba drive is mapped in Windows, call to is_writable returns false on folders and files although these are actually writable.

is_readable seems working ok.

Test script:
---------------
echo is_writeable("Z://fdvtest"); // returns 0
file_put_contents("Z://fdvtest/file", "content"); // works fine


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 [2015-01-28 14:53 UTC] ab@php.net
-Status: Open +Status: Feedback
 [2015-01-28 14:53 UTC] ab@php.net
Cannot reproduce here:

var_dump(is_writable('p:\tmp'));
var_dump(file_put_contents('p:\tmp\hello.txt', 'hello'));

this delivers

bool(true)
int(5)

@lukyer please check what exactly is causing this behavior and provide some more data, so we can reproduce and debug.

Thanks.
 [2015-01-29 07:12 UTC] lukyer at gmail dot com
-Status: Feedback +Status: Open
 [2015-01-29 07:12 UTC] lukyer at gmail dot com
Drive Z in my case is Samba mapped drive using "Map network drive" function in Windows Explorer. "tmp (\\192.168.0.15\bughunt)". Any other drives works as expected. Just network Samba drives are problematic.

var_dump(is_writable('Z:\tmp'));
var_dump(file_put_contents('Z:\tmp\hello.txt', 'hello'));

output:

bool(false)
int(5)
 [2015-02-12 19:00 UTC] ab@php.net
-Status: Open +Status: Analyzed
 [2015-02-12 19:00 UTC] ab@php.net
I've spent some time on debugging this and can confirm. The reason for this behavior is here https://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/ChangeNotes.html#id2578661 .

You probably could check that
- you use samba3 or above
- the folder owner is mapped to something like "nobody", with either full or restricted access rights (use right click -> security -> advanced)

You also could play with the access rights on the linux machine, just to see whether it changes something in PHP behavior.

The issue here is that unmapped unix user accounts are mapped to built-in windows SIDs, which are obviously have nothing to do with windows ACLs. We could currently look whether it's possible to cover this part within PHP. In general it looks more like samba compat issue, because as you've mentioned - the native shares work well.

Regards
 [2015-02-12 19:05 UTC] ab@php.net
-Assigned To: +Assigned To: ab
 [2015-06-04 19:13 UTC] webmastersguide2000 at yahoo dot com
I get a similar symptom going back to at least 5.4.19, but without Samba.

We are running:
PHP Version 5.4.19


System	Windows NT DEV-LMS2 6.1 build 7601 (Windows Server 2008 R2 Enterprise Edition Service Pack 1) i586
Build Date	Aug 21 2013 01:06:09
Compiler	MSVC9 (Visual C++ 2008)
Architecture	x86
Configure Command	cscript /nologo configure.js "--enable-snapshot-build" "--enable-debug-pack" "--disable-zts" "--disable-isapi" "--disable-nsapi" "--without-mssql" "--without-pdo-mssql" "--without-pi3web" "--with-pdo-oci=C:\php-sdk\oracle\instantclient10\sdk,shared" "--with-oci8=C:\php-sdk\oracle\instantclient10\sdk,shared" "--with-oci8-11g=C:\php-sdk\oracle\instantclient11\sdk,shared" "--with-enchant=shared" "--enable-object-out-dir=../obj/" "--enable-com-dotnet=shared" "--with-mcrypt=static" "--disable-static-analyze" "--with-pgo"

In my case at least, is_writeable also returns false for directories which are writeable.
 [2015-06-04 21:06 UTC] yohgaki@php.net
This issue is related to SAMBA.
Anyone who experiences this, please add your Samba configurations.
There is similar issue reported for session storage on mounted (shared) file system. This may be the reason why some users have session storage issue on mounted files under windows.
 [2015-06-04 21:28 UTC] webmastersguide2000 at yahoo dot com
> This issue is related to SAMBA.

The problem does occur when files are accessed locally, without SMB. (SAMBA is Linux, SMB is Windows).
In our case, the storage is _also_ shared from the affected machine to other clients via SMB, but the problem occurs when the files are accessed locally, not via SMB.
 [2015-06-05 17:34 UTC] ab@php.net
@webmastersguide2000,

thanks for the report.

How it looks like, your issue is different from what is originally reported here. If it is on the local FS, it's most likely a misconfiguration. The unmapped unix users are unlikely to be in the game, but what were imaginable for example is the ACLs difference concerning the system account for CLI and the impersonated account used under IIS.

If you still think it's the same issue, please prove it with some stable reproduce case. Maybe some rolle could play that those files are additionally shared through SMB. Please test also the latest VC11 builds like PHP 5.6, the 5.4 branch only accepts the security fixes so we won't be able to pass any corrections there, just for the case.

Thanks.
 [2016-08-26 12:48 UTC] alex dot goris at fastlikehell dot com
I believe I have this bug in my development environment.
I am running PHP 5.6.22, 64-bit version, my workstation is Windows 10 Pro x64.
I am developing in Visual Studio using the DevSense phptools plugin, this plugin debugs the code using xdebug and the built-in webserver of php.exe

I have created the following test script:
<?php
var_dump(is_writable("//10.151.140.102/TestAlex/SubFolder1/"));
var_dump(file_put_contents("//10.151.140.102/TestAlex/SubFolder1/Test.txt", "Testing..."));
var_dump(is_writable("//127.0.0.1/c$/temp/SubFolder1/"));
var_dump(file_put_contents("//127.0.0.1/c$/temp/SubFolder1/Test.txt", "Testing..."));
?>

Which outputs:
script1.php:2:boolean false
script1.php:3:int 10
script1.php:4:boolean true
script1.php:5:int 10

Note that the first line returns false
However, I do have write permissions on the //10.151.140.102/TestAlex/SubFolder1/ folder.
Also, the Test.txt file exists in that directory with the 'Tersting...' string.

Note that am a member of the Administrators group on the 10.151.140.102 machine.

I was surprised to see the is_writable() function returning true on the \\127.0.0.1\c$\... share, this I can not explain...
This is going wrong on 2 different development machines (both running above mentioned configuration).

On our test webserver, which runs Windows 2008 R2 x64, Apache 2.4.4 and php 5.6.16 the is_writable() function correctly sees the \\10.151.140.102\TestAlex\... path as writable and returns true
 [2016-12-02 23:10 UTC] anrdaemon at freemail dot ru
This is not directly related to Samba.
Accessing AD share from a machine not joined to domain produce similar results.

Bottom line is: You MUST NOT make any decisions based on manual ACL inspection, if you are not the access control entity.

I've had to namespace something to get my code going forward.

<?php
namespace Same\As\One\You\Use\Them\In;
function is_readable($file)
{
    if(file_exists($file) && is_file($file))
    {
        $f = @fopen($file, 'rb');
        if(fclose($f))
        {
            return true;
        }
    }

    return false;
}

function is_writable($file)
{
    $result = false;
    if(file_exists($file) && is_file($file))
    {
        $f = @fopen($file, 'ab');
        if(fclose($f))
        {
            return true;
        }
    }

    return false;
}
?>
 [2017-10-24 05:46 UTC] kalle@php.net
-Status: Analyzed +Status: Assigned
 [2019-02-28 08:50 UTC] david dot sautter at web dot de
I confirm, that this issue is not related to Samba. My setup is a mapped NFSv4 network drive between two linux machines. The client is not part of the domain, while the server is. 

(https://stackoverflow.com/questions/54904676/php-is-writable-false-for-nfs-share-even-though-it-is-writable-for-the-user-www)
This Stackoverflow question covers additional information about my setup. User id mapping seems to be correct for example.
 
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