summary refs log tree commit diff
path: root/sysdeps/posix/tempname.c
blob: 1f86549df3cd2a4c50abd7e37554edd9d739c5ce (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
/* Copyright (C) 1991-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#if HAVE_CONFIG_H
# include <config.h>
#endif

#include <sys/types.h>
#include <assert.h>

#include <errno.h>
#ifndef __set_errno
# define __set_errno(Val) errno = (Val)
#endif

#include <stdio.h>
#ifndef P_tmpdir
# define P_tmpdir "/tmp"
#endif
#ifndef TMP_MAX
# define TMP_MAX 238328
#endif
#ifndef __GT_FILE
# define __GT_FILE	0
# define __GT_DIR	1
# define __GT_NOCREATE	2
#endif

#if STDC_HEADERS || _LIBC
# include <stddef.h>
# include <stdlib.h>
# include <string.h>
#endif

#if HAVE_FCNTL_H || _LIBC
# include <fcntl.h>
#endif

#if HAVE_SYS_TIME_H || _LIBC
# include <sys/time.h>
#endif

#if HAVE_STDINT_H || _LIBC
# include <stdint.h>
#endif

#if HAVE_UNISTD_H || _LIBC
# include <unistd.h>
#endif

#include <sys/stat.h>
#if STAT_MACROS_BROKEN
# undef S_ISDIR
#endif
#if !defined S_ISDIR && defined S_IFDIR
# define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
#endif
#if !S_IRUSR && S_IREAD
# define S_IRUSR S_IREAD
#endif
#if !S_IRUSR
# define S_IRUSR 00400
#endif
#if !S_IWUSR && S_IWRITE
# define S_IWUSR S_IWRITE
#endif
#if !S_IWUSR
# define S_IWUSR 00200
#endif
#if !S_IXUSR && S_IEXEC
# define S_IXUSR S_IEXEC
#endif
#if !S_IXUSR
# define S_IXUSR 00100
#endif

#if _LIBC
# define struct_stat64 struct stat64
#else
# define struct_stat64 struct stat
# define __getpid getpid
# define __gettimeofday gettimeofday
# define __mkdir mkdir
# define __open open
# define __open64 open
# define __lxstat64(version, path, buf) lstat (path, buf)
# define __xstat64(version, path, buf) stat (path, buf)
#endif

#if ! (HAVE_SECURE_GETENV || _LIBC)
# ifdef HAVE___SECURE_GETENV
#  define __libc_secure_getenv __secure_getenv
# else
#  define __libc_secure_getenv getenv
# endif
#endif

#ifdef _LIBC
# include <hp-timing.h>
# if HP_TIMING_AVAIL
#  define RANDOM_BITS(Var) \
  if (__builtin_expect (value == UINT64_C (0), 0))			      \
    {									      \
      /* If this is the first time this function is used initialize	      \
	 the variable we accumulate the value in to some somewhat	      \
	 random value.  If we'd not do this programs at startup time	      \
	 might have a reduced set of possible names, at least on slow	      \
	 machines.  */							      \
      struct timeval tv;						      \
      __gettimeofday (&tv, NULL);					      \
      value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;		      \
    }									      \
  HP_TIMING_NOW (Var)
# endif
#endif

/* Use the widest available unsigned type if uint64_t is not
   available.  The algorithm below extracts a number less than 62**6
   (approximately 2**35.725) from uint64_t, so ancient hosts where
   uintmax_t is only 32 bits lose about 3.725 bits of randomness,
   which is better than not having mkstemp at all.  */
#if !defined UINT64_MAX && !defined uint64_t
# define uint64_t uintmax_t
#endif

/* Return nonzero if DIR is an existent directory.  */
static int
direxists (const char *dir)
{
  struct_stat64 buf;
  return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
}

/* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
   non-null and exists, uses it; otherwise uses the first of $TMPDIR,
   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
   doesn't exist, none of the searched dirs exists, or there's not
   enough space in TMPL. */
int
__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
	       int try_tmpdir)
{
  const char *d;
  size_t dlen, plen;

  if (!pfx || !pfx[0])
    {
      pfx = "file";
      plen = 4;
    }
  else
    {
      plen = strlen (pfx);
      if (plen > 5)
	plen = 5;
    }

  if (try_tmpdir)
    {
      d = __libc_secure_getenv ("TMPDIR");
      if (d != NULL && direxists (d))
	dir = d;
      else if (dir != NULL && direxists (dir))
	/* nothing */ ;
      else
	dir = NULL;
    }
  if (dir == NULL)
    {
      if (direxists (P_tmpdir))
	dir = P_tmpdir;
      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
	dir = "/tmp";
      else
	{
	  __set_errno (ENOENT);
	  return -1;
	}
    }

  dlen = strlen (dir);
  while (dlen > 1 && dir[dlen - 1] == '/')
    dlen--;			/* remove trailing slashes */

  /* check we have room for "${dir}/${pfx}XXXXXX\0" */
  if (tmpl_len < dlen + 1 + plen + 6 + 1)
    {
      __set_errno (EINVAL);
      return -1;
    }

  sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
  return 0;
}

/* These are the characters used in temporary filenames.  */
static const char letters[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

/* Generate a temporary file name based on TMPL.  TMPL must match the
   rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).
   The name constructed does not exist at the time of the call to
   __gen_tempname.  TMPL is overwritten with the result.

   KIND may be one of:
   __GT_NOCREATE:	simply verify that the name does not exist
			at the time of the call.
   __GT_FILE:		create the file using open(O_CREAT|O_EXCL)
			and return a read-write fd.  The file is mode 0600.
   __GT_DIR:		create a directory, which will be mode 0700.

   We use a clever algorithm to get hard-to-predict names. */
int
__gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
{
  int len;
  char *XXXXXX;
  static uint64_t value;
  uint64_t random_time_bits;
  unsigned int count;
  int fd = -1;
  int save_errno = errno;
  struct_stat64 st;

  /* A lower bound on the number of temporary files to attempt to
     generate.  The maximum total number of temporary file names that
     can exist for a given template is 62**6.  It should never be
     necessary to try all these combinations.  Instead if a reasonable
     number of names is tried (we define reasonable as 62**3) fail to
     give the system administrator the chance to remove the problems.  */
#define ATTEMPTS_MIN (62 * 62 * 62)

  /* The number of times to attempt to generate a temporary file.  To
     conform to POSIX, this must be no smaller than TMP_MAX.  */
#if ATTEMPTS_MIN < TMP_MAX
  unsigned int attempts = TMP_MAX;
#else
  unsigned int attempts = ATTEMPTS_MIN;
#endif

  len = strlen (tmpl);
  if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
    {
      __set_errno (EINVAL);
      return -1;
    }

  /* This is where the Xs start.  */
  XXXXXX = &tmpl[len - 6 - suffixlen];

  /* Get some more or less random data.  */
#ifdef RANDOM_BITS
  RANDOM_BITS (random_time_bits);
#else
# if HAVE_GETTIMEOFDAY || _LIBC
  {
    struct timeval tv;
    __gettimeofday (&tv, NULL);
    random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
  }
# else
  random_time_bits = time (NULL);
# endif
#endif
  value += random_time_bits ^ __getpid ();

  for (count = 0; count < attempts; value += 7777, ++count)
    {
      uint64_t v = value;

      /* Fill in the random bits.  */
      XXXXXX[0] = letters[v % 62];
      v /= 62;
      XXXXXX[1] = letters[v % 62];
      v /= 62;
      XXXXXX[2] = letters[v % 62];
      v /= 62;
      XXXXXX[3] = letters[v % 62];
      v /= 62;
      XXXXXX[4] = letters[v % 62];
      v /= 62;
      XXXXXX[5] = letters[v % 62];

      switch (kind)
	{
	case __GT_FILE:
	  fd = __open (tmpl,
		       (flags & ~O_ACCMODE)
		       | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
	  break;

	case __GT_DIR:
	  fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
	  break;

	case __GT_NOCREATE:
	  /* This case is backward from the other three.  __gen_tempname
	     succeeds if __xstat fails because the name does not exist.
	     Note the continue to bypass the common logic at the bottom
	     of the loop.  */
	  if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
	    {
	      if (errno == ENOENT)
		{
		  __set_errno (save_errno);
		  return 0;
		}
	      else
		/* Give up now. */
		return -1;
	    }
	  continue;

	default:
	  assert (! "invalid KIND in __gen_tempname");
	}

      if (fd >= 0)
	{
	  __set_errno (save_errno);
	  return fd;
	}
      else if (errno != EEXIST)
	return -1;
    }

  /* We got out of the loop because we ran out of combinations to try.  */
  __set_errno (EEXIST);
  return -1;
}