lib/tempname.c

   1 /* Copyright (C) 1991-1999, 2000 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., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #if HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 #include <sys/types.h>
  24 #include <assert.h>
  25
  26 #include <errno.h>
  27 #ifndef __set_errno
  28 # define __set_errno(Val) errno = (Val)
  29 #endif
  30
  31 #include <stdio.h>
  32 #ifndef P_tmpdir
  33 # define P_tmpdir "/tmp"
  34 #endif
  35 #ifndef TMP_MAX
  36 # define TMP_MAX 238328
  37 #endif
  38 #ifndef __GT_FILE
  39 # define __GT_FILE      0
  40 # define __GT_BIGFILE   1
  41 # define __GT_DIR       2
  42 # define __GT_NOCREATE  3
  43 #endif
  44
  45 #if STDC_HEADERS || _LIBC
  46 # include <stddef.h>
  47 # include <stdlib.h>
  48 # include <string.h>
  49 #endif
  50
  51 #if HAVE_FCNTL_H || _LIBC
  52 # include <fcntl.h>
  53 #endif
  54
  55 #if HAVE_SYS_TIME_H || _LIBC
  56 # include <sys/time.h>
  57 #endif
  58
  59 #if HAVE_STDINT_H || _LIBC
  60 # include <stdint.h>
  61 #endif
  62
  63 #if HAVE_UNISTD_H || _LIBC
  64 # include <unistd.h>
  65 #endif
  66
  67 #include <sys/stat.h>
  68 #if STAT_MACROS_BROKEN
  69 # undef S_ISDIR
  70 #endif
  71 #if !defined S_ISDIR && defined S_IFDIR
  72 # define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
  73 #endif
  74 #if !S_IRUSR && S_IREAD
  75 # define S_IRUSR S_IREAD
  76 #endif
  77 #if !S_IRUSR
  78 # define S_IRUSR 00400
  79 #endif
  80 #if !S_IWUSR && S_IWRITE
  81 # define S_IWUSR S_IWRITE
  82 #endif
  83 #if !S_IWUSR
  84 # define S_IWUSR 00200
  85 #endif
  86 #if !S_IXUSR && S_IEXEC
  87 # define S_IXUSR S_IEXEC
  88 #endif
  89 #if !S_IXUSR
  90 # define S_IXUSR 00100
  91 #endif
  92
  93 #if _LIBC
  94 # define struct_stat64 struct stat64
  95 #else
  96 # define struct_stat64 struct stat
  97 # define __getpid getpid
  98 # define __gettimeofday gettimeofday
  99 # define __mkdir mkdir
 100 # define __open open
 101 # define __open64 open
 102 # define __lxstat64(version, path, buf) lstat (path, buf)
 103 # define __xstat64(version, path, buf) stat (path, buf)
 104 #endif
 105
 106 #if ! (HAVE___SECURE_GETENV || _LIBC)
 107 # define __secure_getenv getenv
 108 #endif
 109
 110 /* Use the widest available unsigned type if uint64_t is not
 111    available.  The algorithm below extracts a number less than 62**6
 112    (approximately 2**35.725) from uint64_t, so ancient hosts where
 113    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
 114    which is better than not having mkstemp at all.  */
 115 #if !defined UINT64_MAX && !defined uint64_t
 116 # define uint64_t uintmax_t
 117 #endif
 118
 119 /* Return nonzero if DIR is an existent directory.  */
 120 static int
 121 direxists (const char *dir)
 122 {
 123   struct_stat64 buf;
 124   return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
 125 }
 126
 127 /* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
 128    non-null and exists, uses it; otherwise uses the first of $TMPDIR,
 129    P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
 130    for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
 131    doesn't exist, none of the searched dirs exists, or there's not
 132    enough space in TMPL. */
 133 int
 134 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
 135                int try_tmpdir)
 136 {
 137   const char *d;
 138   size_t dlen, plen;
 139
 140   if (!pfx || !pfx[0])
 141     {
 142       pfx = "file";
 143       plen = 4;
 144     }
 145   else
 146     {
 147       plen = strlen (pfx);
 148       if (plen > 5)
 149         plen = 5;
 150     }
 151
 152   if (try_tmpdir)
 153     {
 154       d = __secure_getenv ("TMPDIR");
 155       if (d != NULL && direxists (d))
 156         dir = d;
 157       else if (dir != NULL && direxists (dir))
 158         /* nothing */ ;
 159       else
 160         dir = NULL;
 161     }
 162   if (dir == NULL)
 163     {
 164       if (direxists (P_tmpdir))
 165         dir = P_tmpdir;
 166       else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
 167         dir = "/tmp";
 168       else
 169         {
 170           __set_errno (ENOENT);
 171           return -1;
 172         }
 173     }
 174
 175   dlen = strlen (dir);
 176   while (dlen > 1 && dir[dlen - 1] == '/')
 177     dlen--;                     /* remove trailing slashes */
 178
 179   /* check we have room for "${dir}/${pfx}XXXXXX\0" */
 180   if (tmpl_len < dlen + 1 + plen + 6 + 1)
 181     {
 182       __set_errno (EINVAL);
 183       return -1;
 184     }
 185
 186   sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
 187   return 0;
 188 }
 189
 190 /* These are the characters used in temporary filenames.  */
 191 static const char letters[] =
 192 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 193
 194 /* Generate a temporary file name based on TMPL.  TMPL must match the
 195    rules for mk[s]temp (i.e. end in "XXXXXX").  The name constructed
 196    does not exist at the time of the call to __gen_tempname.  TMPL is
 197    overwritten with the result.
 198
 199    KIND may be one of:
 200    __GT_NOCREATE:       simply verify that the name does not exist
 201                         at the time of the call.
 202    __GT_FILE:           create the file using open(O_CREAT|O_EXCL)
 203                         and return a read-write fd.  The file is mode 0600.
 204    __GT_BIGFILE:        same as __GT_FILE but use open64().
 205    __GT_DIR:            create a directory, which will be mode 0700.
 206
 207    We use a clever algorithm to get hard-to-predict names. */
 208 int
 209 __gen_tempname (char *tmpl, int kind)
 210 {
 211   int len;
 212   char *XXXXXX;
 213   static uint64_t value;
 214   uint64_t random_time_bits;
 215   int count, fd = -1;
 216   int save_errno = errno;
 217   struct_stat64 st;
 218
 219   len = strlen (tmpl);
 220   if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
 221     {
 222       __set_errno (EINVAL);
 223       return -1;
 224     }
 225
 226   /* This is where the Xs start.  */
 227   XXXXXX = &tmpl[len - 6];
 228
 229   /* Get some more or less random data.  */
 230 #if HAVE_GETTIMEOFDAY || _LIBC
 231   {
 232     struct timeval tv;
 233     __gettimeofday (&tv, NULL);
 234     random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
 235   }
 236 #else
 237   random_time_bits = time (NULL);
 238 #endif
 239   value += random_time_bits ^ __getpid ();
 240
 241   for (count = 0; count < TMP_MAX; value += 7777, ++count)
 242     {
 243       uint64_t v = value;
 244
 245       /* Fill in the random bits.  */
 246       XXXXXX[0] = letters[v % 62];
 247       v /= 62;
 248       XXXXXX[1] = letters[v % 62];
 249       v /= 62;
 250       XXXXXX[2] = letters[v % 62];
 251       v /= 62;
 252       XXXXXX[3] = letters[v % 62];
 253       v /= 62;
 254       XXXXXX[4] = letters[v % 62];
 255       v /= 62;
 256       XXXXXX[5] = letters[v % 62];
 257
 258       switch (kind)
 259         {
 260         case __GT_FILE:
 261           fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 262           break;
 263
 264         case __GT_BIGFILE:
 265           fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 266           break;
 267
 268         case __GT_DIR:
 269           fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
 270           break;
 271
 272         case __GT_NOCREATE:
 273           /* This case is backward from the other three.  __gen_tempname
 274              succeeds if __xstat fails because the name does not exist.
 275              Note the continue to bypass the common logic at the bottom
 276              of the loop.  */
 277           if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
 278             {
 279               if (errno == ENOENT)
 280                 {
 281                   __set_errno (save_errno);
 282                   return 0;
 283                 }
 284               else
 285                 /* Give up now. */
 286                 return -1;
 287             }
 288           continue;
 289
 290         default:
 291           assert (! "invalid KIND in __gen_tempname");
 292         }
 293
 294       if (fd >= 0)
 295         {
 296           __set_errno (save_errno);
 297           return fd;
 298         }
 299       else if (errno != EEXIST)
 300         return -1;
 301     }
 302
 303   /* We got out of the loop because we ran out of combinations to try.  */
 304   __set_errno (EEXIST);
 305   return -1;
 306 }