Very Computer

i have a script say
and it contains,

#Script A
sh

Lets call it A, if i set the uid bit and gid bit and i make it executable
by world. ie
-rwsrwsrwx
and somebody runs the script,
As a result, the executer will get a sh prompt,
if he does whoami, he does not get my username but his. Why?
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Vishal C. Thakkar                               4632, South Hagadorn Road,
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Taken from man exec :

   Note that the set-user-ID and set-group-ID functions do not apply to
   scripts; thus, if execlp() or execvp() executes a script, the
set-user-ID
   and set-group-ID bits are ignored, even if they are set.

STANDARDS CONFORMANCE
   execlp(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1

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Herve Couppe de Lahongrais (SEU)       | Eurocontrol Experimental Centre

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1) Edit and compile the following file foo.c

#include <stdlib.h>

int     main(int argc, char *argv[])
{
        return system("my_whoami");

Quote:}

fred> chmod u+s foo

3) Edit the script my_whoami

#!/bin/sh
whoami

4) Set the exec bit on the script my_whoami

fred> chmod a+x my_whoami

5) Run foo as user fred : it prints "fred"

6) Run foo as another user : it also prints "fred"

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Herve Couppe de Lahongrais (SEU)       | Eurocontrol Experimental Centre

|>> So, is it possible to have the desired effect using a system() call from
|>> a C program which is SUID and GUID ?

|> Yes, it is possible.

No, not with modern shells.  They'll drop the privileges unless called
with -p, which is impossible with system().  You'll have to use execve(2)
directly.

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Andreas Schwab                                      "And now for something