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Date: Thu, 07 Jan 2010 00:39:40 -0500
From: Raman Gupta <rocketraman AT fastmail DOT fm>
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To: cygwin AT cygwin DOT com
Subject: Re: 1.7.1-1 noacl on samba share has incorrect directory write bit
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On 01/06/2010 10:01 PM, Larry Hall (Cygwin) wrote:
> On 01/06/2010 09:22 PM, Raman Gupta wrote:
>> I have an smbfs mount (served by samba 3.4.2) in noacl mode on cygwin
>> 1.7.1-1:
>>
>> //smserver/smshare on /mnt/shar type smbfs (binary,notexec,noacl,user)
>>
>> Here is the directory as seen on the unix server directly:
>>
>> root AT smserver foo]# ls -ald bar
>> dr-xr-sr-x. 2 root agroup 4096 2007-04-21 23:23 bar
>>
>> As you can see, the directory bar is not writable.
>>
>> However, here is what cygwin in noacl mode sees:
>>
>> Raman Gupta AT client /mnt/shar/foo
>> $ ls -ald bar
>> drwxr-xr-x 1 Raman Gupta None 0 2007-04-21 23:23 bar
>>
>> The mode shown is 755 rather than 555, and indeed cygwin does not have
>> write access to this directory:
>>
>> Raman Gupta AT client /mnt/shar/foo/bar
>> $ touch baz
>> touch: cannot touch `baz': Permission denied
>>
>> Shouldn't cygwin therefore read the permissions as 555?
>>
>> In acl mode, cygwin does correctly show these directory permissions as
>> 555.
>>
>> Note that read-only *files* are correctly displayed by cygwin/noacl as
>> 444.
>
> Well, you've told Cygwin that it shouldn't consult the file system
> for permissions. So you see is what Cygwin defaults to in these
> situations. If you ask Cygwin to tell you the permissions on
> something in a file system where you also told it not to check the
> permissions, you don't expect to see  the actual correct
 > permissions, do you?

Well... yes -- at least in this case. As per the documentation 
(http://www.cygwin.com/cygwin-ug-net/using.html#mount-table):

"Cygwin ignores filesystem ACLs and only fakes a subset of permission 
bits based on the DOS readonly attribute"

On the server:

root AT smserver foo]# ls -ald bar baz
dr-xr-sr-x. 2 root agroup 4096 2007-04-21 23:23 bar
drwxrwsr-x. 2 root agroup 4096 2007-04-21 23:23 baz

Since the default behavior of Samba is to map the DOS read-only flag 
as per the write bits 
(http://www.samba.org/samba/docs/man/manpages-3/smb.conf.5.html#MAPREADONLY), 
the write bits carry over to the DOS readonly attribute on the share. 
This can be verified via the DOS attrib command on the client:

Raman Gupta AT client /mnt/shar/foo
$ attrib bar
      R     \\smserver\smshare\foo\bar

Raman Gupta AT client /mnt/shar/foo
$ attrib baz
            \\smserver\smshare\foo\baz

and yet, Cygwin reports owner write bit set in both cases:

Raman Gupta AT client /mnt/shar/foo
$ ls -ald bar baz
drwxr-xr-x 1 Raman Gupta None 0 2007-04-21 23:23 bar
drwxr-xr-x 1 Raman Gupta None 0 2007-04-21 23:23 baz

Therefore, it appears that cygwin is following its own documentation 
for files but not for directories.

Cheers,
Raman

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