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Message-ID: <3E8E15A4.154B92FA@ieee.org>
Date: Fri, 04 Apr 2003 18:30:44 -0500
From: "Pierre A. Humblet" <Pierre DOT Humblet AT ieee DOT org>
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To: cygwin AT cygwin DOT com
Subject: Ash ntsec woes [was: Re: Postinstall failure: file not found]
References: <F84TDnJkHHFvhsl5AsK000144fd AT hotmail DOT com> <3E8DA250 DOT E8687FCA AT ieee DOT org> <20030404151741 DOT GA249497 AT Worldnet> <20030404152605 DOT GA599585 AT Worldnet>
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Here is how sh behaves when executing a script with strange permissions
/> cat sayhi
echo hi
/> getfacl sayhi
# file: sayhi
# owner: AdministratorS
# group: Users
user::---
user:PHumblet:rwx
group::---
mask:rwx
other:---
/> sh -c sayhi    <== OK
hi                
/> sh -c /sayhi   <== Does not realize file is executable
/sayhi: not found 
/> setfacl -s u::---,g::---,o:--- sayhi
/> sh -c sayhi    <== Goes ahead even though file is unreadable
/> echo $?
255

The reason why ash is inconsistent is that when it searches 
a command on PATH it does NOT check for executable or even
readable files.
There is code that used to do that on line 558 of exec.c,
but it is "#ifdef notdef".
On the other hand, absolute paths are checked with stat on lines
459 and 472 (partly in Cygwin specific code).

So ash is always too permissive or too strict when looking up
commands, although its builtin "test" is fine. 
The "just right" way in Cygwin is to use access(X_OK) on all
3 lines listed above.

Pierre

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