sendmail/test/t_dropgid.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 setgid works.
**  Compile it, make it set-group-ID guest, and run it as yourself (NOT as
**  root and not as member of the group guest).
**
**  Compilation is trivial -- just "cc t_dropgid.c".  Make it set-group-ID
**  guest 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_dropgid.c,v 1.7 2013-11-22 20:52:01 ca Exp $";
#endif /* ! lint */

static void
printgids(str, r, e)
    char *str;
    gid_t r, e;
{
    printf("%s (should be %d/%d): r/egid=%d/%d\n", str, (int) r, (int) e,
           (int) getgid(), (int) getegid());
}

/* define only one of these */
#if HASSETEGID
# define SETGIDCALL "setegid"
#endif /* HASSETEGID */
#if HASSETREGID
# define SETGIDCALL "setregid"
#endif /* HASSETREGID */
#if HASSETRESGID
# define SETGIDCALL "setresgid"
#endif /* HASSETRESGID */

#ifndef SETGIDCALL
#  define SETGIDCALL    "setgid"
#endif /* ! SETGIDCALL */

int
main(argc, argv)
    int argc;
    char **argv;
{
    int fail = 0;
    int res;
    gid_t realgid = getgid();
    gid_t effgid = getegid();
    char *prg = argv[0];

    printgids("initial gids", realgid, effgid);

    if (effgid == realgid)
    {
        printf("SETUP ERROR: re-run set-group-ID guest\n");
        printf("Use chgrp(1) and chmod(1)\n");
        printf("For example, do this as root ");
        printf("(nobody is the name of a group in this example):\n");
        printf("# chgrp nobody %s\n", prg);
        printf("# chmod g+s nobody %s\n", prg);
        exit(1);
    }

#if HASSETREGID
    res = setregid(realgid, realgid);
    printf("setregid(%d)=%d %s\n", (int) realgid, res,
        res < 0 ? "failure" : "ok");
    printgids("after setregid()", realgid, realgid);
#endif /* HASSETREGID */
#if HASSETRESGID
    res = setresgid(realgid, realgid, realgid);
    printf("setresgid(%d)=%d %s\n", (int) realgid, res,
        res < 0 ? "failure" : "ok");
    printgids("after setresgid()", realgid, realgid);
#endif /* HASSETRESGID */
#if HASSETEGID
    res = setegid(realgid);
    printf("setegid(%d)=%d %s\n", (int) realgid, res,
        res < 0 ? "failure" : "ok");
    printgids("after setegid()", realgid, realgid);
#endif /* HASSETEGID */
    res = setgid(realgid);
    printf("setgid(%d)=%d %s\n", (int) realgid, res,
        res < 0 ? "failure" : "ok");
    printgids("after setgid()", realgid, realgid);

    if (getegid() != realgid)
    {
        fail++;
        printf("MAYDAY!  Wrong effective gid\n");
    }

    if (getgid() != realgid)
    {
        fail++;
        printf("MAYDAY!  Wrong real gid\n");
    }

    /* do activity here */
    if (setgid(effgid) == 0)
    {
        fail++;
        printf("MAYDAY!  setgid(%d) succeeded (should have failed)\n",
            effgid);
    }
    else
    {
        printf("setgid(%d) failed (this is correct)\n", effgid);
    }
    printgids("after setgid() to egid", realgid, realgid);

    if (getegid() != realgid)
    {
        fail++;
        printf("MAYDAY!  Wrong effective gid\n");
    }
    if (getgid() != realgid)
    {
        fail++;
        printf("MAYDAY!  Wrong real gid\n");
    }
    printf("\n");

    if (fail > 0)
    {
        printf("\nThis system cannot use %s to give up set-group-ID rights\n",
               SETGIDCALL);
#if !HASSETEGID
        printf("Maybe compile with -DHASSETEGID and try again\n");
#endif /* !HASSETEGID */
#if !HASSETREGID
        printf("Maybe compile with -DHASSETREGID and try again\n");
#endif /* !HASSETREGID */
#if !HASSETRESGID
        printf("Maybe compile with -DHASSETRESGID and try again\n");
#endif /* !HASSETRESGID */
        exit(1);
    }

    printf("\nIt is possible to use %s on this system\n", SETGIDCALL);
    exit(0);
}