sh.1, nval.3, shell.3 + shcomp + suid_exec ... / was: Re:[ksh93-integration-discuss] Re: unreferenced filesexception_listwas Re: [osol-code]Roundtwo:((pre-)pre-review)ksh93-integrationwebrev2007-02-02

[David Korn]

cc: 
Subject: Re: Re: sh.1, nval.3, shell.3 + shcomp + suid_exec ... / was:  Re:[ksh93-integration-discuss] Re: unreferenced  filesexception_listwas Re:  [osol-code]Roundtwo:((pre-)pre-review)ksh93-integrationwebrev2007-02-02
--------

> >If the exec command supports #!, and #! also works for scripts
> >that are setuid and/or execute only, then there is no need for
> >suid_exec.
> 
> It works for set-uid scripts; it does not work for execute
> only scripts (except those which are setuid, I think)
> 
> >For execute only scripts, the exec call needs to open the
> >file and pass down the open file descriptor as /dev/fd/n
> >where n is the file descriptor.
> 
> This we'd need to fix, perhaps.  I don't see any sane reason
> for execute only scripts to normally work.
Why should shell scripts be different than C programs.  You don't
need read permission to execute a C program so you shouldn't
need it to execute a shell script.
> 
> (This is compounded by the fact that the kernel may not be able
> to determine how to open execute only scripts; but a set-uid root
> helper program would get into trouble even more quickly as it is
> certain to fail over NFS)
At the kernel level, shouldn't it can bypass ordinary file file
permissions or temporarily do a setuid root to open the file.
> 
> Could ksh93 use /proc/self/path/$(basename $0) in error messages
> rather than /dev/fd/X?
The shell tried to change $0 when it encounters /dev/fd/X but the
method depends on the system.  The link to /proc/self/exe gives
the pathname for the interpreter, not the script.

It would be nice of for ps, #! displayed the name of the script
rather than the name of the interpreter.
> 
> Casper
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> http://mail.opensolaris.org/mailman/listinfo/ksh93-integration-discuss
> 

David Korn
dgk at research.att.com