compat_mkstemps.c

   1 /* $Id: compat_mkstemps.c,v 1.1 2021/09/19 15:05:39 schwarze Exp $ */
   2 /*
   3  * Copyright (c) 2015, 2021 Ingo Schwarze <schwarze@openbsd.org>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  *
  17  * Parts of the algorithm of this function are inspired by OpenBSD
  18  * mkdtemp(3) by Theo de Raadt and Todd Miller, but the code differs.
  19  */
  20 #include "config.h"
  21
  22 #include <sys/stat.h>
  23 #include <errno.h>
  24 #include <fcntl.h>
  25 #include <limits.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28
  29 int
  30 mkstemps(char *path, int suffixlen)
  31 {
  32         char    *start, *end, *cp;
  33         int      fd, tries;
  34         char     backup;
  35
  36         end = strchr(path, '\0');
  37         if (suffixlen < 0 || suffixlen > end - path - 6) {
  38                 errno = EINVAL;
  39                 return -1;
  40         }
  41         end -= suffixlen;
  42         for (start = end; start > path; start--)
  43                 if (start[-1] != 'X')
  44                         break;
  45
  46         backup = *end;
  47         for (tries = INT_MAX; tries; tries--) {
  48                 *end = '\0';
  49                 cp = mktemp(path);
  50                 *end = backup;
  51                 if (cp == NULL)
  52                         return -1;
  53                 fd = open(path, O_CREAT | O_EXCL | O_RDWR, S_IRUSR | S_IWUSR);
  54                 if (fd != -1)
  55                         return fd;
  56                 for (cp = start; cp < end; cp++)
  57                         *cp = 'X';
  58                 if (errno != EEXIST)
  59                         return -1;
  60         }
  61         errno = EEXIST;
  62         return -1;
  63 }