lib/mkdtemp.c

   1 /* Copyright (C) 1999, 2001-2002 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
  17    Boston, MA 02110-1301  USA.  */
  18
  19 /* Extracted from misc/mkdtemp.c and sysdeps/posix/tempname.c.  */
  20
  21 #ifdef HAVE_CONFIG_H
  22 # include "config.h"
  23 #endif
  24
  25 /* Specification.  */
  26 #include "mkdtemp.h"
  27
  28 #include <errno.h>
  29 #ifndef __set_errno
  30 # define __set_errno(Val) errno = (Val)
  31 #endif
  32
  33 #include <stddef.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36
  37 #include <stdio.h>
  38 #ifndef TMP_MAX
  39 # define TMP_MAX 238328
  40 #endif
  41
  42 #if HAVE_STDINT_H_WITH_UINTMAX || _LIBC
  43 # include <stdint.h>
  44 #endif
  45
  46 #if HAVE_INTTYPES_H_WITH_UINTMAX || _LIBC
  47 # include <inttypes.h>
  48 #endif
  49
  50 #if HAVE_UNISTD_H || _LIBC
  51 # include <unistd.h>
  52 #endif
  53
  54 #if HAVE_GETTIMEOFDAY || _LIBC
  55 # if HAVE_SYS_TIME_H || _LIBC
  56 #  include <sys/time.h>
  57 # endif
  58 #else
  59 # if HAVE_TIME_H || _LIBC
  60 #  include <time.h>
  61 # endif
  62 #endif
  63
  64 #include <sys/stat.h>
  65 #if STAT_MACROS_BROKEN
  66 # undef S_ISDIR
  67 #endif
  68 #if !defined S_ISDIR && defined S_IFDIR
  69 # define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
  70 #endif
  71 #if !S_IRUSR && S_IREAD
  72 # define S_IRUSR S_IREAD
  73 #endif
  74 #if !S_IRUSR
  75 # define S_IRUSR 00400
  76 #endif
  77 #if !S_IWUSR && S_IWRITE
  78 # define S_IWUSR S_IWRITE
  79 #endif
  80 #if !S_IWUSR
  81 # define S_IWUSR 00200
  82 #endif
  83 #if !S_IXUSR && S_IEXEC
  84 # define S_IXUSR S_IEXEC
  85 #endif
  86 #if !S_IXUSR
  87 # define S_IXUSR 00100
  88 #endif
  89
  90 #if !_LIBC
  91 # define __getpid getpid
  92 # define __gettimeofday gettimeofday
  93 # define __mkdir mkdir
  94 #endif
  95
  96 /* Use the widest available unsigned type if uint64_t is not
  97    available.  The algorithm below extracts a number less than 62**6
  98    (approximately 2**35.725) from uint64_t, so ancient hosts where
  99    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
 100    which is better than not having mkstemp at all.  */
 101 #if !defined UINT64_MAX && !defined uint64_t
 102 # define uint64_t uintmax_t
 103 #endif
 104
 105 /* These are the characters used in temporary filenames.  */
 106 static const char letters[] =
 107 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 108
 109 /* Generate a temporary file name based on TMPL.  TMPL must match the
 110    rules for mk[s]temp (i.e. end in "XXXXXX").  The name constructed
 111    does not exist at the time of the call to __gen_tempname.  TMPL is
 112    overwritten with the result.
 113
 114    KIND is:
 115    __GT_DIR:            create a directory, which will be mode 0700.
 116
 117    We use a clever algorithm to get hard-to-predict names. */
 118 static int
 119 gen_tempname (tmpl)
 120      char *tmpl;
 121 {
 122   int len;
 123   char *XXXXXX;
 124   static uint64_t value;
 125   uint64_t random_time_bits;
 126   int count, fd = -1;
 127   int save_errno = errno;
 128
 129   len = strlen (tmpl);
 130   if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
 131     {
 132       __set_errno (EINVAL);
 133       return -1;
 134     }
 135
 136   /* This is where the Xs start.  */
 137   XXXXXX = &tmpl[len - 6];
 138
 139   /* Get some more or less random data.  */
 140 #ifdef RANDOM_BITS
 141   RANDOM_BITS (random_time_bits);
 142 #else
 143 # if HAVE_GETTIMEOFDAY || _LIBC
 144   {
 145     struct timeval tv;
 146     __gettimeofday (&tv, NULL);
 147     random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
 148   }
 149 # else
 150   random_time_bits = time (NULL);
 151 # endif
 152 #endif
 153   value += random_time_bits ^ __getpid ();
 154
 155   for (count = 0; count < TMP_MAX; value += 7777, ++count)
 156     {
 157       uint64_t v = value;
 158
 159       /* Fill in the random bits.  */
 160       XXXXXX[0] = letters[v % 62];
 161       v /= 62;
 162       XXXXXX[1] = letters[v % 62];
 163       v /= 62;
 164       XXXXXX[2] = letters[v % 62];
 165       v /= 62;
 166       XXXXXX[3] = letters[v % 62];
 167       v /= 62;
 168       XXXXXX[4] = letters[v % 62];
 169       v /= 62;
 170       XXXXXX[5] = letters[v % 62];
 171
 172       fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
 173
 174       if (fd >= 0)
 175         {
 176           __set_errno (save_errno);
 177           return fd;
 178         }
 179       else if (errno != EEXIST)
 180         return -1;
 181     }
 182
 183   /* We got out of the loop because we ran out of combinations to try.  */
 184   __set_errno (EEXIST);
 185   return -1;
 186 }
 187
 188 /* Generate a unique temporary directory from TEMPLATE.
 189    The last six characters of TEMPLATE must be "XXXXXX";
 190    they are replaced with a string that makes the filename unique.
 191    The directory is created, mode 700, and its name is returned.
 192    (This function comes from OpenBSD.) */
 193 char *
 194 mkdtemp (template)
 195      char *template;
 196 {
 197   if (gen_tempname (template))
 198     return NULL;
 199   else
 200     return template;
 201 }