/*
** This program checks to see if your version of setuid works.
** Compile it, make it setuid root, and run it as yourself (NOT as
** root).
**
** NOTE: This should work everywhere, but Linux has the ability
** to use the undocumented setcap() call to make this break.
**
** Compilation is trivial -- just "cc t_setuid.c". Make it setuid,
** root and then execute it as a non-root user.
*/
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#ifndef lint
static char id[] = "@(#)$Id: t_setuid.c,v 8.2.2.1 2000/05/31 00:29:47 gshapiro Exp $";
#endif /* ! lint */
static void
printuids(str, r, e)
char *str;
int r, e;
{
printf("%s (should be %d/%d): r/euid=%d/%d\n", str, r, e,
getuid(), geteuid());
}
int
main(argc, argv)
int argc;
char **argv;
{
int fail = 0;
uid_t realuid = getuid();
printuids("initial uids", realuid, 0);
if (geteuid() != 0)
{
printf("SETUP ERROR: re-run setuid root\n");
exit(1);
}
if (getuid() == 0)
{
printf("SETUP ERROR: must be run by a non-root user\n");
exit(1);
}
if (setuid(1) < 0)
printf("setuid(1) failure\n");
printuids("after setuid(1)", 1, 1);
if (geteuid() != 1)
{
fail++;
printf("MAYDAY! Wrong effective uid\n");
}
if (getuid() != 1)
{
fail++;
printf("MAYDAY! Wrong real uid\n");
}
/* do activity here */
if (setuid(0) == 0)
{
fail++;
printf("MAYDAY! setuid(0) succeeded (should have failed)\n");
}
else
{
printf("setuid(0) failed (this is correct)\n");
}
printuids("after setuid(0)", 1, 1);
if (geteuid() != 1)
{
fail++;
printf("MAYDAY! Wrong effective uid\n");
}
if (getuid() != 1)
{
fail++;
printf("MAYDAY! Wrong real uid\n");
}
printf("\n");
if (fail)
{
printf("\nThis system cannot use setuid (maybe use setreuid)\n");
exit(1);
}
printf("\nIt is safe to use setuid on this system\n");
exit(0);
}
