1/* Copyright (C) 1991-1999, 2000, 2001 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   This program is free software; you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation; either version 2, or (at your option)
7   any later version.
8
9   This program 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
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License
15   along with this program; if not, write to the Free Software Foundation,
16   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
17
18#if HAVE_CONFIG_H
19# include <config.h>
20#endif
21
22#include <sys/types.h>
23#include <assert.h>
24
25#include <errno.h>
26#ifndef __set_errno
27# define __set_errno(Val) errno = (Val)
28#endif
29
30#include <stdio.h>
31#ifndef P_tmpdir
32# define P_tmpdir "/tmp"
33#endif
34#ifndef TMP_MAX
35# define TMP_MAX 238328
36#endif
37#ifndef __GT_FILE
38# define __GT_FILE	0
39# define __GT_BIGFILE	1
40# define __GT_DIR	2
41# define __GT_NOCREATE	3
42#endif
43
44#if STDC_HEADERS || _LIBC
45# include <stddef.h>
46# include <string.h>
47#endif
48
49#include <stdlib.h>
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#ifdef _LIBC
111# include <hp-timing.h>
112# if HP_TIMING_AVAIL
113#  define RANDOM_BITS(Var) \
114  if (__builtin_expect (value == UINT64_C (0), 0))			      \
115    {									      \
116      /* If this is the first time this function is used initialize	      \
117	 the variable we accumulate the value in to some somewhat	      \
118	 random value.  If we'd not do this programs at startup time	      \
119	 might have a reduced set of possible names, at least on slow	      \
120	 machines.  */							      \
121      struct timeval tv;						      \
122      __gettimeofday (&tv, NULL);					      \
123      value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;		      \
124    }									      \
125  HP_TIMING_NOW (Var)
126# endif
127#endif
128
129/* Use the widest available unsigned type if uint64_t is not
130   available.  The algorithm below extracts a number less than 62**6
131   (approximately 2**35.725) from uint64_t, so ancient hosts where
132   uintmax_t is only 32 bits lose about 3.725 bits of randomness,
133   which is better than not having mkstemp at all.  */
134#if !defined UINT64_MAX && !defined uint64_t
135# define uint64_t uintmax_t
136#endif
137
138/* Return nonzero if DIR is an existent directory.  */
139static int
140direxists (const char *dir)
141{
142  struct_stat64 buf;
143  return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
144}
145
146/* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
147   non-null and exists, uses it; otherwise uses the first of $TMPDIR,
148   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
149   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
150   doesn't exist, none of the searched dirs exists, or there's not
151   enough space in TMPL. */
152int
153__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
154	       int try_tmpdir)
155{
156  const char *d;
157  size_t dlen, plen;
158
159  if (!pfx || !pfx[0])
160    {
161      pfx = "file";
162      plen = 4;
163    }
164  else
165    {
166      plen = strlen (pfx);
167      if (plen > 5)
168	plen = 5;
169    }
170
171  if (try_tmpdir)
172    {
173      d = __secure_getenv ("TMPDIR");
174      if (d != NULL && direxists (d))
175	dir = d;
176      else if (dir != NULL && direxists (dir))
177	/* nothing */ ;
178      else
179	dir = NULL;
180    }
181  if (dir == NULL)
182    {
183      if (direxists (P_tmpdir))
184	dir = P_tmpdir;
185      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
186	dir = "/tmp";
187      else
188	{
189	  __set_errno (ENOENT);
190	  return -1;
191	}
192    }
193
194  dlen = strlen (dir);
195  while (dlen > 1 && dir[dlen - 1] == '/')
196    dlen--;			/* remove trailing slashes */
197
198  /* check we have room for "${dir}/${pfx}XXXXXX\0" */
199  if (tmpl_len < dlen + 1 + plen + 6 + 1)
200    {
201      __set_errno (EINVAL);
202      return -1;
203    }
204
205  sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
206  return 0;
207}
208
209/* These are the characters used in temporary filenames.  */
210static const char letters[] =
211"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
212
213/* Generate a temporary file name based on TMPL.  TMPL must match the
214   rules for mk[s]temp (i.e. end in "XXXXXX").  The name constructed
215   does not exist at the time of the call to __gen_tempname.  TMPL is
216   overwritten with the result.
217
218   KIND may be one of:
219   __GT_NOCREATE:	simply verify that the name does not exist
220			at the time of the call.
221   __GT_FILE:		create the file using open(O_CREAT|O_EXCL)
222			and return a read-write fd.  The file is mode 0600.
223   __GT_BIGFILE:	same as __GT_FILE but use open64().
224   __GT_DIR:		create a directory, which will be mode 0700.
225
226   We use a clever algorithm to get hard-to-predict names. */
227int
228__gen_tempname (char *tmpl, int kind)
229{
230  int len;
231  char *XXXXXX;
232  static uint64_t value;
233  uint64_t random_time_bits;
234  unsigned int count;
235  int fd = -1;
236  int save_errno = errno;
237  struct_stat64 st;
238
239  /* A lower bound on the number of temporary files to attempt to
240     generate.  The maximum total number of temporary file names that
241     can exist for a given template is 62**6.  It should never be
242     necessary to try all these combinations.  Instead if a reasonable
243     number of names is tried (we define reasonable as 62**3) fail to
244     give the system administrator the chance to remove the problems.  */
245  unsigned int attempts_min = 62 * 62 * 62;
246
247  /* The number of times to attempt to generate a temporary file.  To
248     conform to POSIX, this must be no smaller than TMP_MAX.  */
249  unsigned int attempts = attempts_min < TMP_MAX ? TMP_MAX : attempts_min;
250
251  len = strlen (tmpl);
252  if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
253    {
254      __set_errno (EINVAL);
255      return -1;
256    }
257
258  /* This is where the Xs start.  */
259  XXXXXX = &tmpl[len - 6];
260
261  /* Get some more or less random data.  */
262#ifdef RANDOM_BITS
263  RANDOM_BITS (random_time_bits);
264#else
265# if HAVE_GETTIMEOFDAY || _LIBC
266  {
267    struct timeval tv;
268    __gettimeofday (&tv, NULL);
269    random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
270  }
271# else
272  random_time_bits = time (NULL);
273# endif
274#endif
275  value += random_time_bits ^ __getpid ();
276
277  for (count = 0; count < attempts; value += 7777, ++count)
278    {
279      uint64_t v = value;
280
281      /* Fill in the random bits.  */
282      XXXXXX[0] = letters[v % 62];
283      v /= 62;
284      XXXXXX[1] = letters[v % 62];
285      v /= 62;
286      XXXXXX[2] = letters[v % 62];
287      v /= 62;
288      XXXXXX[3] = letters[v % 62];
289      v /= 62;
290      XXXXXX[4] = letters[v % 62];
291      v /= 62;
292      XXXXXX[5] = letters[v % 62];
293
294      switch (kind)
295	{
296	case __GT_FILE:
297	  fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
298	  break;
299
300	case __GT_BIGFILE:
301	  fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
302	  break;
303
304	case __GT_DIR:
305	  fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
306	  break;
307
308	case __GT_NOCREATE:
309	  /* This case is backward from the other three.  __gen_tempname
310	     succeeds if __xstat fails because the name does not exist.
311	     Note the continue to bypass the common logic at the bottom
312	     of the loop.  */
313	  if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
314	    {
315	      if (errno == ENOENT)
316		{
317		  __set_errno (save_errno);
318		  return 0;
319		}
320	      else
321		/* Give up now. */
322		return -1;
323	    }
324	  continue;
325
326	default:
327	  assert (! "invalid KIND in __gen_tempname");
328	}
329
330      if (fd >= 0)
331	{
332	  __set_errno (save_errno);
333	  return fd;
334	}
335      else if (errno != EEXIST)
336	return -1;
337    }
338
339  /* We got out of the loop because we ran out of combinations to try.  */
340  __set_errno (EEXIST);
341  return -1;
342}
343