Re: hard links create local DoS vulnerability and security proble

[H. Peter Anvin]

Followup to:  <xltptfhd0wk.fsf@xxxxxxxxxxxxxxxxxxx>
By author:    Mathieu Chouquet-Stringer <mathieu@xxxxxxxxxxx>
In newsgroup: linux.dev.kernel
> 
> It's always been my understanding that you cannot have suid shell script
> because you could easily change the IFS. Am i wrong? (
> 

Well, sort of.

You can't have a setuid shell script using #!/bin/bash because
/bin/bash doesn't support it.

You *can* have a setuid Perl script using #!/usr/bin/perl because Perl
knows how to run setuid safely.

It's up to the script interpreter (if it is setuid or has an setuid
wrapper available -- Perl does it the latter way) to decide to honour
the setuid bit on a script.

If you really want to use a setuid script, you can create
a setuid /usr/bin/setuidbash which would do whatever sanitization you
felt was appropriate, and then exec bash with the appropriate
permissions.  Then put #!/usr/bin/setuidbash in your scripts.

	-hpa


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