sendmail/test/t_exclopen.c

/*
 * Copyright (c) 1999 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 tests your system to see if you have the lovely
**  security-defeating semantics that an open with O_CREAT|O_EXCL
**  set will successfully open a file named by a symbolic link that
**  points to a non-existent file.  Sadly, Posix is mute on what
**  should happen in this situation.
**
**  Results to date:
**  AIX 3.2     OK
**  BSD family  OK
**    BSD/OS 2.1    OK
**    FreeBSD 2.1   OK
**  DEC OSF/1 3.0   OK
**  HP-UX 9.04  FAIL
**  HP-UX 9.05  FAIL
**  HP-UX 9.07  OK
**  HP-UX 10.01 OK
**  HP-UX 10.10 OK
**  HP-UX 10.20 OK
**  Irix 5.3    OK
**  Irix 6.2    OK
**  Irix 6.3    OK
**  Irix 6.4    OK
**  Linux       OK
**  NeXT 2.1    OK
**  Solaris 2.x OK
**  SunOS 4.x   OK
**  Ultrix 4.3  OK
*/

#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

#ifndef lint
static char id[] = "@(#)$Id: t_exclopen.c,v 8.7 2013-11-22 20:52:01 ca Exp $";
#endif /* ! lint */

static char Attacker[128];
static char Attackee[128];

static void
bail(status)
    int status;
{
    (void) unlink(Attacker);
    (void) unlink(Attackee);
    exit(status);
}

int
main(argc, argv)
    int argc;
    char **argv;
{
    struct stat st;

    sprintf(Attacker, "/tmp/attacker.%d.%ld", getpid(), time(NULL));
    sprintf(Attackee, "/tmp/attackee.%d.%ld", getpid(), time(NULL));

    if (symlink(Attackee, Attacker) < 0)
    {
        printf("Could not create %s->%s symlink: %d\n",
            Attacker, Attackee, errno);
        bail(1);
    }
    (void) unlink(Attackee);
    if (stat(Attackee, &st) >= 0)
    {
        printf("%s already exists -- remove and try again.\n",
            Attackee);
        bail(1);
    }
    if (open(Attacker, O_WRONLY|O_CREAT|O_EXCL, 0644) < 0)
    {
        int save_errno = errno;

        if (stat(Attackee, &st) >= 0)
        {
            printf("Weird.  Open failed but %s was created anyhow (errno = %d)\n",
                Attackee, save_errno);
            bail(1);
        }
        printf("Good show!  Exclusive open works properly with symbolic links (errno = %d).\n",
            save_errno);
        bail(0);
    }
    if (stat(Attackee, &st) < 0)
    {
        printf("Weird.  Open succeeded but %s was not created\n",
            Attackee);
        bail(2);
    }
    printf("Bad news: you can do an exclusive open through a symbolic link\n");
    printf("\tBe sure you #define BOGUS_O_EXCL in conf.h\n");
    bail(1);

    /* NOTREACHED */
    exit(0);
}