sendmail/test/t_setuid.c

/*
 * Copyright (c) 2001 Proofpoint, Inc. and its suppliers.
 *  All rights reserved.
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the sendmail distribution.
 *
 */

/*
**  This program checks to see if your version of setuid works.
**  Compile it, make it set-user-ID 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 set-user-ID,
**  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 8.8 2013-11-22 20:52:01 ca Exp $";
#endif /* ! lint */

static void
printuids(str, r, e)
    char *str;
    uid_t r, e;
{
    printf("%s (should be %d/%d): r/euid=%d/%d\n", str, (int) r, (int) e,
           (int) getuid(), (int) 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 set-user-ID 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);
}