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
135int __path_search(char *tmpl, size_t tmpl_len, const char *dir,
136				  const char *pfx, int try_tmpdir);
137int __gen_tempname(char *tmpl, int kind);
138
139/* Return nonzero if DIR is an existent directory.  */
140static int
141direxists(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 $TMPDIR,
150   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
151   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
152   doesn't exist, none of the searched dirs exists, or there's not
153   enough space in TMPL. */
154int
155__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
156	       int try_tmpdir)
157{
158  const char *d;
159  size_t dlen, plen;
160
161  if (!pfx || !pfx[0])
162    {
163      pfx = "file";
164      plen = 4;
165    }
166  else
167    {
168      plen = strlen (pfx);
169      if (plen > 5)
170	plen = 5;
171    }
172
173  if (try_tmpdir)
174    {
175      d = __secure_getenv ("TMPDIR");
176      if (d != NULL && direxists (d))
177	dir = d;
178      else if (dir != NULL && direxists (dir))
179	/* nothing */ ;
180      else
181	dir = NULL;
182    }
183  if (dir == NULL)
184    {
185      if (direxists (P_tmpdir))
186	dir = P_tmpdir;
187      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
188	dir = "/tmp";
189      else
190	{
191	  __set_errno (ENOENT);
192	  return -1;
193	}
194    }
195
196  dlen = strlen (dir);
197  while (dlen > 1 && dir[dlen - 1] == '/')
198    dlen--;			/* remove trailing slashes */
199
200  /* check we have room for "${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 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}
342