To: cygwin@cygwin.com
From: Gmane User <fma@doe.carleton.ca>
Subject:  Re: Admin can read user file from bash, despite permissions
Date:  Thu, 10 Apr 2008 11:14:41 -0400
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References:  <ftkisc$jj1$1@ger.gmane.org> <20080410084231.GB548@calimero.vinschen.de>
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Corinna Vinschen wrote:
> On Apr 10 04:19, Gmane User wrote:
>> I have a power user file that has go-rwx.  However, the administrator
>> account can "less" the contents from a bash command line.  This is
>> both logging onto Windows 2000 as admin, as well as ssh'ing in
>> (loopback) from the power user log-in session.  The administrator can
>> also "mv" the file to a different name, but it can't create a new file
>> in the same folder e.g. by "cp".
>>
>> CACLS shows an extensive set of permissions for the power user owner,
>> but only READ_CONTROL, FILE_READ_EA, & FILE_READ_ATTRIBUTES for
>> LaptopName\None and Everyone.  I've come across nothing on the web
>> (yet) about a special privilege that allows administrators the level
>> of access that it seems to have.  In fact, if I just open up a DOS
>> shell as Administrator, I cannot "more" the said file.  So it seems to
>> be specific to Cygwin rather than Windows.
>> [...]
>> what is the explanation?
> 
> The secret word for tonight is "Privileges".  See
> http://msdn2.microsoft.com/en-us/library/bb530716(vs.85).aspx
> 
> Administrators have the SE_BACKUP_NAME privilege by default.  Cygwin
> opens the files with the FILE_FLAG_BACKUP_SEMANTICS flag set, see
> http://msdn2.microsoft.com/en-us/library/aa363858.aspx So, all accounts
> with the backup privilege (usually admins and backup operators) can open
> all files.  That's the same as with the "root" user on UNIX.
> 
> It does not work with the standard Windows tools, because these tools
> don't open files with FILE_FLAG_BACKUP_SEMANTICS.  Sort of an
> obfuscation, if you ask me.
> 
> cp doesn't work because the current release of Cygwin doesn't use
> the FILE_FLAG_BACKUP_SEMANTICS flag in every necessary place so far.

Thank you, Corinna.  That was very informative.

BTW, I found this site to be invaluable for those ramping up:
http://www.pluralsight.com/wiki/default.aspx/Keith.GuideBook/WhatIsAPrivilege.html

Cheers!


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