X-Recipient: archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status: No, hits=-3.2 required=5.0 	tests=AWL,BAYES_00,J_CHICKENPOX_64,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS,SPF_PASS,UNPARSEABLE_RELAY
X-Spam-Check-By: sourceware.org
To: cygwin AT cygwin DOT com
From: Eric Blake <ebb9 AT byu DOT net>
Subject:  Re: [BUG 1.7] Read-only files are not.
Date: Thu, 1 Jan 2009 00:06:40 +0000 (UTC)
Lines: 30
Message-ID:  <loom.20090101T000200-655@post.gmane.org>
References:  <495C00DF DOT 5020208 AT acm DOT org>
Mime-Version:  1.0
Content-Type:  text/plain; charset=us-ascii
Content-Transfer-Encoding:  7bit
User-Agent: Loom/3.14 (http://gmane.org/)
X-IsSubscribed: yes
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id: <cygwin.cygwin.com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com

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




--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/