gnu/dist/texinfo/lib/tempname.c

   1 /*      $NetBSD$        */
   2
   3 /* tempname.c - generate the name of a temporary file.
   4
   5    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
   6    2000, 2001, 2002, 2003 Free Software Foundation, Inc.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2, or (at your option)
  11    any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License along
  19    with this program; if not, write to the Free Software Foundation,
  20    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  21
  22 #if HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #include <sys/types.h>
  27 #include <assert.h>
  28
  29 #include <errno.h>
  30 #ifndef __set_errno
  31 # define __set_errno(Val) errno = (Val)
  32 #endif
  33
  34 #include <stdio.h>
  35 #ifndef P_tmpdir
  36 # define P_tmpdir "/tmp"
  37 #endif
  38 #ifndef TMP_MAX
  39 # define TMP_MAX 238328
  40 #endif
  41 #ifndef __GT_FILE
  42 # define __GT_FILE      0
  43 # define __GT_BIGFILE   1
  44 # define __GT_DIR       2
  45 # define __GT_NOCREATE  3
  46 #endif
  47
  48 #include <stddef.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51
  52 #if HAVE_FCNTL_H || _LIBC
  53 # include <fcntl.h>
  54 #endif
  55
  56 #if HAVE_SYS_TIME_H || _LIBC
  57 # include <sys/time.h>
  58 #endif
  59
  60 #if HAVE_STDINT_H || _LIBC
  61 # include <stdint.h>
  62 #endif
  63 #if HAVE_INTTYPES_H
  64 # include <inttypes.h>
  65 #endif
  66
  67 #if HAVE_UNISTD_H || _LIBC
  68 # include <unistd.h>
  69 #endif
  70
  71 #include <sys/stat.h>
  72 #if STAT_MACROS_BROKEN
  73 # undef S_ISDIR
  74 #endif
  75 #if !defined S_ISDIR && defined S_IFDIR
  76 # define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
  77 #endif
  78 #if !S_IRUSR && S_IREAD
  79 # define S_IRUSR S_IREAD
  80 #endif
  81 #if !S_IRUSR
  82 # define S_IRUSR 00400
  83 #endif
  84 #if !S_IWUSR && S_IWRITE
  85 # define S_IWUSR S_IWRITE
  86 #endif
  87 #if !S_IWUSR
  88 # define S_IWUSR 00200
  89 #endif
  90 #if !S_IXUSR && S_IEXEC
  91 # define S_IXUSR S_IEXEC
  92 #endif
  93 #if !S_IXUSR
  94 # define S_IXUSR 00100
  95 #endif
  96
  97 #if _LIBC
  98 # define struct_stat64 struct stat64
  99 #else
 100 # define struct_stat64 struct stat
 101 # define __getpid getpid
 102 # define __gettimeofday gettimeofday
 103 # define __mkdir mkdir
 104 # define __open open
 105 # define __open64 open
 106 # define __lxstat64(version, path, buf) lstat (path, buf)
 107 # define __xstat64(version, path, buf) stat (path, buf)
 108 #endif
 109
 110 #if ! (HAVE___SECURE_GETENV || _LIBC)
 111 # define __secure_getenv getenv
 112 #endif
 113
 114 #ifdef _LIBC
 115 # include <hp-timing.h>
 116 # if HP_TIMING_AVAIL
 117 #  define RANDOM_BITS(Var) \
 118   if (__builtin_expect (value == UINT64_C (0), 0))                            \
 119     {                                                                         \
 120       /* If this is the first time this function is used initialize           \
 121          the variable we accumulate the value in to some somewhat             \
 122          random value.  If we'd not do this programs at startup time          \
 123          might have a reduced set of possible names, at least on slow         \
 124          machines.  */                                                        \
 125       struct timeval tv;                                                      \
 126       __gettimeofday (&tv, NULL);                                             \
 127       value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;                      \
 128     }                                                                         \
 129   HP_TIMING_NOW (Var)
 130 # endif
 131 #endif
 132
 133 /* Use the widest available unsigned type if uint64_t is not
 134    available.  The algorithm below extracts a number less than 62**6
 135    (approximately 2**35.725) from uint64_t, so ancient hosts where
 136    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
 137    which is better than not having mkstemp at all.  */
 138 #if !defined UINT64_MAX && !defined uint64_t
 139 # define uint64_t uintmax_t
 140 #endif
 141
 142 /* Return nonzero if DIR is an existent directory.  */
 143 static int
 144 direxists (const char *dir)
 145 {
 146   struct_stat64 buf;
 147   return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
 148 }
 149
 150 /* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
 151    non-null and exists, uses it; otherwise uses the first of $TMPDIR,
 152    P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
 153    for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
 154    doesn't exist, none of the searched dirs exists, or there's not
 155    enough space in TMPL. */
 156 int
 157 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
 158                int try_tmpdir)
 159 {
 160   const char *d;
 161   size_t dlen, plen;
 162
 163   if (!pfx || !pfx[0])
 164     {
 165       pfx = "file";
 166       plen = 4;
 167     }
 168   else
 169     {
 170       plen = strlen (pfx);
 171       if (plen > 5)
 172         plen = 5;
 173     }
 174
 175   if (try_tmpdir)
 176     {
 177       d = __secure_getenv ("TMPDIR");
 178       if (d != NULL && direxists (d))
 179         dir = d;
 180       else if (dir != NULL && direxists (dir))
 181         /* nothing */ ;
 182       else
 183         dir = NULL;
 184     }
 185   if (dir == NULL)
 186     {
 187       if (direxists (P_tmpdir))
 188         dir = P_tmpdir;
 189       else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
 190         dir = "/tmp";
 191       else
 192         {
 193           __set_errno (ENOENT);
 194           return -1;
 195         }
 196     }
 197
 198   dlen = strlen (dir);
 199   while (dlen > 1 && dir[dlen - 1] == '/')
 200     dlen--;                     /* remove trailing slashes */
 201
 202   /* check we have room for "${dir}/${pfx}XXXXXX\0" */
 203   if (tmpl_len < dlen + 1 + plen + 6 + 1)
 204     {
 205       __set_errno (EINVAL);
 206       return -1;
 207     }
 208
 209   sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
 210   return 0;
 211 }
 212
 213 /* These are the characters used in temporary filenames.  */
 214 static const char letters[] =
 215 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 216
 217 /* Generate a temporary file name based on TMPL.  TMPL must match the
 218    rules for mk[s]temp (i.e. end in "XXXXXX").  The name constructed
 219    does not exist at the time of the call to __gen_tempname.  TMPL is
 220    overwritten with the result.
 221
 222    KIND may be one of:
 223    __GT_NOCREATE:       simply verify that the name does not exist
 224                         at the time of the call.
 225    __GT_FILE:           create the file using open(O_CREAT|O_EXCL)
 226                         and return a read-write fd.  The file is mode 0600.
 227    __GT_BIGFILE:        same as __GT_FILE but use open64().
 228    __GT_DIR:            create a directory, which will be mode 0700.
 229
 230    We use a clever algorithm to get hard-to-predict names. */
 231 int
 232 __gen_tempname (char *tmpl, int kind)
 233 {
 234   int len;
 235   char *XXXXXX;
 236   static uint64_t value;
 237   uint64_t random_time_bits;
 238   unsigned int count;
 239   int fd = -1;
 240   int save_errno = errno;
 241   struct_stat64 st;
 242
 243   /* A lower bound on the number of temporary files to attempt to
 244      generate.  The maximum total number of temporary file names that
 245      can exist for a given template is 62**6.  It should never be
 246      necessary to try all these combinations.  Instead if a reasonable
 247      number of names is tried (we define reasonable as 62**3) fail to
 248      give the system administrator the chance to remove the problems.  */
 249   unsigned int attempts_min = 62 * 62 * 62;
 250
 251   /* The number of times to attempt to generate a temporary file.  To
 252      conform to POSIX, this must be no smaller than TMP_MAX.  */
 253   unsigned int attempts = attempts_min < TMP_MAX ? TMP_MAX : attempts_min;
 254
 255   len = strlen (tmpl);
 256   if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
 257     {
 258       __set_errno (EINVAL);
 259       return -1;
 260     }
 261
 262   /* This is where the Xs start.  */
 263   XXXXXX = &tmpl[len - 6];
 264
 265   /* Get some more or less random data.  */
 266 #ifdef RANDOM_BITS
 267   RANDOM_BITS (random_time_bits);
 268 #else
 269 # if HAVE_GETTIMEOFDAY || _LIBC
 270   {
 271     struct timeval tv;
 272     __gettimeofday (&tv, NULL);
 273     random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
 274   }
 275 # else
 276   random_time_bits = time (NULL);
 277 # endif
 278 #endif
 279   value += random_time_bits ^ __getpid ();
 280
 281   for (count = 0; count < attempts; value += 7777, ++count)
 282     {
 283       uint64_t v = value;
 284
 285       /* Fill in the random bits.  */
 286       XXXXXX[0] = letters[v % 62];
 287       v /= 62;
 288       XXXXXX[1] = letters[v % 62];
 289       v /= 62;
 290       XXXXXX[2] = letters[v % 62];
 291       v /= 62;
 292       XXXXXX[3] = letters[v % 62];
 293       v /= 62;
 294       XXXXXX[4] = letters[v % 62];
 295       v /= 62;
 296       XXXXXX[5] = letters[v % 62];
 297
 298       switch (kind)
 299         {
 300         case __GT_FILE:
 301           fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 302           break;
 303
 304         case __GT_BIGFILE:
 305           fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 306           break;
 307
 308         case __GT_DIR:
 309           fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
 310           break;
 311
 312         case __GT_NOCREATE:
 313           /* This case is backward from the other three.  __gen_tempname
 314              succeeds if __xstat fails because the name does not exist.
 315              Note the continue to bypass the common logic at the bottom
 316              of the loop.  */
 317           if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
 318             {
 319               if (errno == ENOENT)
 320                 {
 321                   __set_errno (save_errno);
 322                   return 0;
 323                 }
 324               else
 325                 /* Give up now. */
 326                 return -1;
 327             }
 328           continue;
 329
 330         default:
 331           assert (! "invalid KIND in __gen_tempname");
 332         }
 333
 334       if (fd >= 0)
 335         {
 336           __set_errno (save_errno);
 337           return fd;
 338         }
 339       else if (errno != EEXIST)
 340         return -1;
 341     }
 342
 343   /* We got out of the loop because we ran out of combinations to try.  */
 344   __set_errno (EEXIST);
 345   return -1;
 346 }