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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: execve() ignores shell script setuid bit
Date: 20 Jan 1996 21:59:12 GMT
Organization: Utah Valley State College, Orem, Utah
Lines: 31
Message-ID: <4drojg$oj@park.uvsc.edu>
References: <30FEC809.167EB0E7@lasorda.princeton.edu>
NNTP-Posting-Host: 198.17.250.210
Luoqi Chen <luoqi@lasorda.princeton.edu> wrote:
]
] I installed FreeBSD on my PC just a couple of weeks ago. Today I noticed
] that setuid shell script doesn't run with effective uid set. I checked
] with kern_exec.c, it seemed to me that execve() uses the attributes
] of the interpreter rather than those of the script, to check for the
] setuid and setgid bits. Is this a bug or a feature (or simply I misread
] the source code)? I am using FreeBSD 2.1 release.
This is a security feature.
You will need to write a C program if you wish to explicitly
compromise the security of your machine, and have it system(3)
the shell script.
Typically, you will want to hide the shell script via permissions
on the script and the directory it is located in if you want to
give ordinary users access to the calling program.
Obviously, this still leaves a number of possible holes which
a hacker could driver his truck through -- you'd be better of
rewriting the whole thing as a C program... assuming you really
need SUID in the first place, and can't solve the problem some
other way.
Terry Lambert
terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.