Re: Simple HowTo

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On Thu, 2007-12-20 at 09:07 -0800, Les wrote:

> Note that the PATH environment variable determines the locations
> searched and the order in which they are searched.  The last location
> should be /usr/bin.  Care should be exercised in setting up applications
> such that the path and file name choices within the path sequence do not
> mask system operation programs.  For instance if there is a system
> command say "sed" for example, but you create a program or script and
> call it "sed", then place it in the path before /usr/bin, the result
> will be that you will execute the "sed" script rather than the system
> command.  Not only will this affect direct "sed" commands, but it will
> also cause scripts calling "sed" to malfunction when that script is in
> the path before the "sed" program.
> 
> 	I know that quotes are not necessary, but I put them there to emphasize
> the name of the command and script to trigger your eyes to check it out.
> 
> 	One other issue is the users who place their directory or one that they
> have write access to in the path.  This is a security issue.  If you
> then inadvertantly run a virus script, it can generate the executable in
> your local executable directory.  Then just one instance of exercising
> that directory as root or via suedo, and you have problems.  As a
> developer, I have used a local "bin" directory to check out scripts.  I
> generatlly make it under root, and executable as group and world, but
> not root.  Then I can put trials in it amd work with them (this was on
> solaris, so I suspect it will also work on Linux, but I haven't tried
> it).  Just be careful.
----
of course the 'path' parse order is a feature, not a flaw.

It allows you to substitute alternative versions of programs say
in /usr/local/bin or ~/bin while still keeping the standard versions
where they are.

Security of course is always a concern but if someone is writing files
onto your executiion paths on your filesystem without your knowledge,
you were already 'boned' ;-)

Craig

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