You're performing too much work copying your argument list. :P
The wrapper should be entirely transparent: busybox shouldn't
even notice it has been run through it, so it should be called
with the exact same argv. Here's what I do.
Notes:
* untested, please check carefully. The actual code I use depends
on skalibs; I modified it to remove the dependency to post it here.
(Which increased both the source code size and binary code size: yes,
the standard libc APIs suck that much and I wrote skalibs for a reason.)
* BUSYBOX and LIST should be auto-generated to match the final path
to the busybox binary and the list of authorized privileged applets.
* It is necessary to copy argv[0] because basename() can modify its
argument. (Have I ever mentioned that the standard libc APIs suck ?)
I'm doing it with a VLA to avoid pulling in malloc. The VLA can't smash
the stack, because the kernel limits argv.
* No, Rich, I won't do a dichotomic search on a list that size. ;)
-----
#include <string.h>
#include <libgen.h>
#include <stdio.h>
#include <unistd.h>
#define BUSYBOX "/bin/busybox"
static char const *LIST[] =
{
"passwd",
"ping",
"ping6",
"su",
0
} ;
static int okay (char const *s)
{
register char const **p = LIST ;
for (; *p ; p++) if (!strcmp(s, *p)) return 1 ;
return 0 ;
}
int main (int argc, char const *const *argv, char const *const *envp)
{
{
char tmp[strlen(argv[0]) + 1] ;
strcpy(tmp, argv[0]) ;
if (!okay(basename(tmp)))
{
fprintf(stderr, "busybox-setuid: unable to run %s: unauthorized
applet\n", argv[0]) ;
return 1 ;
}
}
execve(BUSYBOX, argv, envp) ;
perror("busybox-setuid: unable to exec " BUSYBOX) ;
return 2 ;
}
-----
--
Laurent
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