src/system/libroot/posix/glibc/stdio-common/tempname.c

   1 /* Copyright (C) 1991-1999, 2000, 2001 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    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
  28 #include <stdio.h>
  29 #ifndef P_tmpdir
  30 # define P_tmpdir "/tmp"
  31 #endif
  32 #ifndef TMP_MAX
  33 # define TMP_MAX 238328
  34 #endif
  35 #ifndef __GT_FILE
  36 # define __GT_FILE      0
  37 # define __GT_BIGFILE   1
  38 # define __GT_DIR       2
  39 # define __GT_NOCREATE  3
  40 #endif
  41
  42 #if STDC_HEADERS || _LIBC
  43 # include <stddef.h>
  44 # include <stdlib.h>
  45 # include <string.h>
  46 #endif
  47
  48 #if HAVE_FCNTL_H || _LIBC
  49 # include <fcntl.h>
  50 #endif
  51
  52 #if HAVE_SYS_TIME_H || _LIBC
  53 # include <sys/time.h>
  54 #endif
  55
  56 #if HAVE_STDINT_H || _LIBC
  57 # include <stdint.h>
  58 #endif
  59
  60 #if HAVE_UNISTD_H || _LIBC
  61 # include <unistd.h>
  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 struct_stat64 struct stat64
  92 #else
  93 # define struct_stat64 struct stat
  94 # define __getpid getpid
  95 # define __gettimeofday gettimeofday
  96 # define __mkdir mkdir
  97 # define __open open
  98 # define __open64 open
  99 # define __lxstat64(version, path, buf) lstat (path, buf)
 100 # define __xstat64(version, path, buf) stat (path, buf)
 101 #endif
 102
 103 #define __secure_getenv getenv
 104
 105 #if 0
 106 #ifdef _LIBC
 107 # include <hp-timing.h>
 108 # if HP_TIMING_AVAIL
 109 #  define RANDOM_BITS(Var) \
 110   if (__builtin_expect (value == UINT64_C (0), 0))                            \
 111     {                                                                         \
 112       /* If this is the first time this function is used initialize           \
 113          the variable we accumulate the value in to some somewhat             \
 114          random value.  If we'd not do this programs at startup time          \
 115          might have a reduced set of possible names, at least on slow         \
 116          machines.  */                                                        \
 117       struct timeval tv;                                                      \
 118       __gettimeofday (&tv, NULL);                                             \
 119       value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;                      \
 120     }                                                                         \
 121   HP_TIMING_NOW (Var)
 122 # endif
 123 #endif
 124 #endif
 125
 126 /* Use the widest available unsigned type if uint64_t is not
 127    available.  The algorithm below extracts a number less than 62**6
 128    (approximately 2**35.725) from uint64_t, so ancient hosts where
 129    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
 130    which is better than not having mkstemp at all.  */
 131 #if !defined UINT64_MAX && !defined uint64_t
 132 # define uint64_t uintmax_t
 133 #endif
 134
 135 int __path_search(char *tmpl, size_t tmpl_len, const char *dir,
 136                                   const char *pfx, int try_tmpdir);
 137 int __gen_tempname(char *tmpl, int kind);
 138
 139 /* Return nonzero if DIR is an existent directory.  */
 140 static int
 141 direxists(const char *dir)
 142 {
 143         struct stat st;
 144         return stat(dir, &st) == 0 && S_ISDIR(st.st_mode);
 145 }
 146
 147
 148 /* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
 149    non-null and exists, uses it; otherwise uses the first of $TMPDIR,
 150    P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
 151    for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
 152    doesn't exist, none of the searched dirs exists, or there's not
 153    enough space in TMPL. */
 154 int
 155 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
 156                int try_tmpdir)
 157 {
 158   const char *d;
 159   size_t dlen, plen;
 160
 161   if (!pfx || !pfx[0])
 162     {
 163       pfx = "file";
 164       plen = 4;
 165     }
 166   else
 167     {
 168       plen = strlen (pfx);
 169       if (plen > 5)
 170         plen = 5;
 171     }
 172
 173   if (try_tmpdir)
 174     {
 175       d = __secure_getenv ("TMPDIR");
 176       if (d != NULL && direxists (d))
 177         dir = d;
 178       else if (dir != NULL && direxists (dir))
 179         /* nothing */ ;
 180       else
 181         dir = NULL;
 182     }
 183   if (dir == NULL)
 184     {
 185       if (direxists (P_tmpdir))
 186         dir = P_tmpdir;
 187       else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
 188         dir = "/tmp";
 189       else
 190         {
 191           __set_errno (ENOENT);
 192           return -1;
 193         }
 194     }
 195
 196   dlen = strlen (dir);
 197   while (dlen > 1 && dir[dlen - 1] == '/')
 198     dlen--;                     /* remove trailing slashes */
 199
 200   /* check we have room for "${dir}/${pfx}XXXXXX\0" */
 201   if (tmpl_len < dlen + 1 + plen + 6 + 1)
 202     {
 203       __set_errno (EINVAL);
 204       return -1;
 205     }
 206
 207   sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
 208   return 0;
 209 }
 210
 211 /* These are the characters used in temporary filenames.  */
 212 static const char letters[] =
 213 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 214
 215 /* Generate a temporary file name based on TMPL.  TMPL must match the
 216    rules for mk[s]temp (i.e. end in "XXXXXX").  The name constructed
 217    does not exist at the time of the call to __gen_tempname.  TMPL is
 218    overwritten with the result.
 219
 220    KIND may be one of:
 221    __GT_NOCREATE:       simply verify that the name does not exist
 222                         at the time of the call.
 223    __GT_FILE:           create the file using open(O_CREAT|O_EXCL)
 224                         and return a read-write fd.  The file is mode 0600.
 225    __GT_BIGFILE:        same as __GT_FILE but use open64().
 226    __GT_DIR:            create a directory, which will be mode 0700.
 227
 228    We use a clever algorithm to get hard-to-predict names. */
 229 int
 230 __gen_tempname (char *tmpl, int kind)
 231 {
 232   int len;
 233   char *XXXXXX;
 234   static uint64_t value;
 235   uint64_t random_time_bits;
 236   unsigned int count;
 237   int fd = -1;
 238   int save_errno = errno;
 239   struct stat st;
 240
 241   /* A lower bound on the number of temporary files to attempt to
 242      generate.  The maximum total number of temporary file names that
 243      can exist for a given template is 62**6.  It should never be
 244      necessary to try all these combinations.  Instead if a reasonable
 245      number of names is tried (we define reasonable as 62**3) fail to
 246      give the system administrator the chance to remove the problems.  */
 247   unsigned int attempts_min = 62 * 62 * 62;
 248
 249   /* The number of times to attempt to generate a temporary file.  To
 250      conform to POSIX, this must be no smaller than TMP_MAX.  */
 251   unsigned int attempts = attempts_min < TMP_MAX ? TMP_MAX : attempts_min;
 252
 253   len = strlen (tmpl);
 254   if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
 255     {
 256       __set_errno (EINVAL);
 257       return -1;
 258     }
 259
 260   /* This is where the Xs start.  */
 261   XXXXXX = &tmpl[len - 6];
 262
 263   /* Get some more or less random data.  */
 264 #ifdef RANDOM_BITS
 265   RANDOM_BITS (random_time_bits);
 266 #else
 267 # if HAVE_GETTIMEOFDAY || _LIBC
 268   {
 269     struct timeval tv;
 270     gettimeofday(&tv, NULL);
 271     random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
 272   }
 273 # else
 274   random_time_bits = time (NULL);
 275 # endif
 276 #endif
 277   value += random_time_bits ^ getpid();
 278
 279   for (count = 0; count < attempts; value += 7777, ++count)
 280     {
 281       uint64_t v = value;
 282
 283       /* Fill in the random bits.  */
 284       XXXXXX[0] = letters[v % 62];
 285       v /= 62;
 286       XXXXXX[1] = letters[v % 62];
 287       v /= 62;
 288       XXXXXX[2] = letters[v % 62];
 289       v /= 62;
 290       XXXXXX[3] = letters[v % 62];
 291       v /= 62;
 292       XXXXXX[4] = letters[v % 62];
 293       v /= 62;
 294       XXXXXX[5] = letters[v % 62];
 295
 296       switch (kind)
 297         {
 298         case __GT_FILE:
 299         case __GT_BIGFILE:
 300           fd = open(tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 301           break;
 302
 303         case __GT_DIR:
 304           fd = mkdir(tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
 305           break;
 306
 307         case __GT_NOCREATE:
 308           /* This case is backward from the other three.  __gen_tempname
 309              succeeds if __xstat fails because the name does not exist.
 310              Note the continue to bypass the common logic at the bottom
 311              of the loop.  */
 312           if (stat(tmpl, &st) < 0)
 313             {
 314               if (errno == ENOENT)
 315                 {
 316                   __set_errno (save_errno);
 317                   return 0;
 318                 }
 319               else
 320                 /* Give up now. */
 321                 return -1;
 322             }
 323           continue;
 324
 325         default:
 326           assert (! "invalid KIND in __gen_tempname");
 327         }
 328
 329       if (fd >= 0)
 330         {
 331           __set_errno (save_errno);
 332           return fd;
 333         }
 334       else if (errno != EEXIST)
 335         return -1;
 336     }
 337
 338   /* We got out of the loop because we ran out of combinations to try.  */
 339   __set_errno (EEXIST);
 340   return -1;
 341 }