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From: Eric Blake <ebb9@byu.net>
Subject:  Re: [BUG 1.7] Read-only files are not.
Date: Thu, 1 Jan 2009 00:06:40 +0000 (UTC)
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David Rothenberger <daveroth <at> acm.org> writes:

> 
> It seems that read-only files in Cygwin 1.7 are not truly
> read-only. The sequence of steps below shows that "chmod 444 file1"
> does not make the file read-only in Cygwin 1.7, while it does in
> Cygwin 1.5. It may have something to do with the Read Only DOS
> attribute. This is set by Cygwin 1.5 but not by Cygwin 1.7. If I
> manually set it for Cygwin 1.7, the file does become read-only.

Are you perchance running as an Administrator, and therefore you have backup 
privileges?  If so, then you have root-like power, and cygwin exposes that by 
opening files with intent to backup even when the ACLs would otherwise make the 
file unreadable.  Therefore, even though none of S_IRUSR, S_IRGRP, S_IROTH are 
set in the posixy st_mode bits, access(file, R_OK) returns 0 and open() is able 
to exploit your root-like powers to read that file.

I thought Corinna mentioned this in the release notes.

> 
> (This issue was brought to my attention by a failing subversion test
> after building for 1.7.)

The findutils testsuite also had to make accomodations to skip certain tests 
when run with root-like privileges.

-- 
Eric Blake




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