1/*	$NetBSD: tempname.c,v 1.1.1.1 2016/01/14 00:11:29 christos Exp $	*/
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.  */
143static int
144direxists (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 $TMPDIR,
152   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
153   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
154   doesn't exist, none of the searched dirs exists, or there's not
155   enough space in TMPL. */
156int
157__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
158	       int try_tmpdir)
159{
160  const char *d;
161  size_t dlen, plen;
162
163  if (!pfx || !pfx[0])
164    {
165      pfx = "file";
166      plen = 4;
167    }
168  else
169    {
170      plen = strlen (pfx);
171      if (plen > 5)
172	plen = 5;
173    }
174
175  if (try_tmpdir)
176    {
177      d = __secure_getenv ("TMPDIR");
178      if (d != NULL && direxists (d))
179	dir = d;
180      else if (dir != NULL && direxists (dir))
181	/* nothing */ ;
182      else
183	dir = NULL;
184    }
185  if (dir == NULL)
186    {
187      if (direxists (P_tmpdir))
188	dir = P_tmpdir;
189      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
190	dir = "/tmp";
191      else
192	{
193	  __set_errno (ENOENT);
194	  return -1;
195	}
196    }
197
198  dlen = strlen (dir);
199  while (dlen > 1 && dir[dlen - 1] == '/')
200    dlen--;			/* remove trailing slashes */
201
202  /* check we have room for "${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.  */
214static 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. */
231int
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}
347