setuid shell scripts

[Chris Torek]

In article <5300 at watdcsu.waterloo.edu> dmcanzi at watdcsu.waterloo.edu
(David Canzi) writes:
>Okay, how about this?
>(2) checks that all directories in the path are searchable by
>    the invoker, owned only by root or bin, and modifiable only
>    by owner.

Since you can check only one path component at a time, this is still
susceptible to spoofing.

(The `access()' syscall has the same problem.  The only way to be
*sure* that user 1234 has the permission to do something is to be user
1234 and do the something.  setreuid() does the trick, as does a
correct implementation of saved setuid [i.e., not the one in SysV].)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris