1/* tempname.c - generate the name of a temporary file.
2
3   Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
4   2000, 2001, 2002, 2003 Free Software Foundation, Inc.
5
6   This program is free software; you can redistribute it and/or modify
7   it under the terms of the GNU General Public License as published by
8   the Free Software Foundation; either version 2, or (at your option)
9   any later version.
10
11   This program is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14   GNU General Public License for more details.
15
16   You should have received a copy of the GNU General Public License along
17   with this program; if not, write to the Free Software Foundation,
18   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
19
20#if HAVE_CONFIG_H
21# include <config.h>
22#endif
23
24#include <sys/types.h>
25#include <assert.h>
26
27#include <errno.h>
28#ifndef __set_errno
29# define __set_errno(Val) errno = (Val)
30#endif
31
32#include <stdio.h>
33#ifndef P_tmpdir
34# define P_tmpdir "/tmp"
35#endif
36#ifndef TMP_MAX
37# define TMP_MAX 238328
38#endif
39#ifndef __GT_FILE
40# define __GT_FILE	0
41# define __GT_BIGFILE	1
42# define __GT_DIR	2
43# define __GT_NOCREATE	3
44#endif
45
46#include <stddef.h>
47#include <stdlib.h>
48#include <string.h>
49
50#if HAVE_FCNTL_H || _LIBC
51# include <fcntl.h>
52#endif
53
54#if HAVE_SYS_TIME_H || _LIBC
55# include <sys/time.h>
56#endif
57
58#if HAVE_STDINT_H || _LIBC
59# include <stdint.h>
60#endif
61#if HAVE_INTTYPES_H
62# include <inttypes.h>
63#endif
64
65#if HAVE_UNISTD_H || _LIBC
66# include <unistd.h>
67#endif
68
69#include <sys/stat.h>
70#if STAT_MACROS_BROKEN
71# undef S_ISDIR
72#endif
73#if !defined S_ISDIR && defined S_IFDIR
74# define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
75#endif
76#if !S_IRUSR && S_IREAD
77# define S_IRUSR S_IREAD
78#endif
79#if !S_IRUSR
80# define S_IRUSR 00400
81#endif
82#if !S_IWUSR && S_IWRITE
83# define S_IWUSR S_IWRITE
84#endif
85#if !S_IWUSR
86# define S_IWUSR 00200
87#endif
88#if !S_IXUSR && S_IEXEC
89# define S_IXUSR S_IEXEC
90#endif
91#if !S_IXUSR
92# define S_IXUSR 00100
93#endif
94
95#if _LIBC
96# define struct_stat64 struct stat64
97#else
98# define struct_stat64 struct stat
99# define __getpid getpid
100# define __gettimeofday gettimeofday
101# define __mkdir mkdir
102# define __open open
103# define __open64 open
104# define __lxstat64(version, path, buf) lstat (path, buf)
105# define __xstat64(version, path, buf) stat (path, buf)
106#endif
107
108#if ! (HAVE___SECURE_GETENV || _LIBC)
109# define __secure_getenv getenv
110#endif
111
112#ifdef _LIBC
113# include <hp-timing.h>
114# if HP_TIMING_AVAIL
115#  define RANDOM_BITS(Var) \
116  if (__builtin_expect (value == UINT64_C (0), 0))			      \
117    {									      \
118      /* If this is the first time this function is used initialize	      \
119	 the variable we accumulate the value in to some somewhat	      \
120	 random value.  If we'd not do this programs at startup time	      \
121	 might have a reduced set of possible names, at least on slow	      \
122	 machines.  */							      \
123      struct timeval tv;						      \
124      __gettimeofday (&tv, NULL);					      \
125      value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;		      \
126    }									      \
127  HP_TIMING_NOW (Var)
128# endif
129#endif
130
131/* Use the widest available unsigned type if uint64_t is not
132   available.  The algorithm below extracts a number less than 62**6
133   (approximately 2**35.725) from uint64_t, so ancient hosts where
134   uintmax_t is only 32 bits lose about 3.725 bits of randomness,
135   which is better than not having mkstemp at all.  */
136#if !defined UINT64_MAX && !defined uint64_t
137# define uint64_t uintmax_t
138#endif
139
140/* Return nonzero if DIR is an existent directory.  */
141static int
142direxists (const char *dir)
143{
144  struct_stat64 buf;
145  return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
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 $TMPDIR,
150   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
151   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
152   doesn't exist, none of the searched dirs exists, or there's not
153   enough space in TMPL. */
154int
155__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
156	       int try_tmpdir)
157{
158  const char *d;
159  size_t dlen, plen;
160
161  if (!pfx || !pfx[0])
162    {
163      pfx = "file";
164      plen = 4;
165    }
166  else
167    {
168      plen = strlen (pfx);
169      if (plen > 5)
170	plen = 5;
171    }
172
173  if (try_tmpdir)
174    {
175      d = __secure_getenv ("TMPDIR");
176      if (d != NULL && direxists (d))
177	dir = d;
178      else if (dir != NULL && direxists (dir))
179	/* nothing */ ;
180      else
181	dir = NULL;
182    }
183  if (dir == NULL)
184    {
185      if (direxists (P_tmpdir))
186	dir = P_tmpdir;
187      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
188	dir = "/tmp";
189      else
190	{
191	  __set_errno (ENOENT);
192	  return -1;
193	}
194    }
195
196  dlen = strlen (dir);
197  while (dlen > 1 && dir[dlen - 1] == '/')
198    dlen--;			/* remove trailing slashes */
199
200  /* check we have room for "${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.  */
212static 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. */
229int
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_stat64 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	  fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
300	  break;
301
302	case __GT_BIGFILE:
303	  fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
304	  break;
305
306	case __GT_DIR:
307	  fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
308	  break;
309
310	case __GT_NOCREATE:
311	  /* This case is backward from the other three.  __gen_tempname
312	     succeeds if __xstat fails because the name does not exist.
313	     Note the continue to bypass the common logic at the bottom
314	     of the loop.  */
315	  if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
316	    {
317	      if (errno == ENOENT)
318		{
319		  __set_errno (save_errno);
320		  return 0;
321		}
322	      else
323		/* Give up now. */
324		return -1;
325	    }
326	  continue;
327
328	default:
329	  assert (! "invalid KIND in __gen_tempname");
330	}
331
332      if (fd >= 0)
333	{
334	  __set_errno (save_errno);
335	  return fd;
336	}
337      else if (errno != EEXIST)
338	return -1;
339    }
340
341  /* We got out of the loop because we ran out of combinations to try.  */
342  __set_errno (EEXIST);
343  return -1;
344}
345