1 /* tempname.c - generate the name of a temporary file.
3 Copyright (C) 1991-2003, 2005-2007, 2009-2018 Free Software Foundation, Inc.
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
18 /* Extracted from glibc sysdeps/posix/tempname.c. See also tmpdir.c. */
22 # include "tempname.h"
25 #include <sys/types.h>
30 # define __set_errno(Val) errno = (Val)
35 # define P_tmpdir "/tmp"
38 # define TMP_MAX 238328
43 # define __GT_NOCREATE 2
45 #if !_LIBC && (GT_FILE != __GT_FILE || GT_DIR != __GT_DIR \
46 || GT_NOCREATE != __GT_NOCREATE)
47 # error report this to bug-gnulib@gnu.org
62 # define struct_stat64 struct stat64
64 # define struct_stat64 struct stat
65 # define __try_tempname try_tempname
66 # define __gen_tempname gen_tempname
67 # define __getpid getpid
68 # define __gettimeofday gettimeofday
69 # define __mkdir mkdir
71 # define __lxstat64(version, file, buf) lstat (file, buf)
75 # include <hp-timing.h>
77 # define RANDOM_BITS(Var) \
78 if (__builtin_expect (value == UINT64_C (0), 0)) \
80 /* If this is the first time this function is used initialize \
81 the variable we accumulate the value in to some somewhat \
82 random value. If we'd not do this programs at startup time \
83 might have a reduced set of possible names, at least on slow \
86 __gettimeofday (&tv, NULL); \
87 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
93 /* Use the widest available unsigned type if uint64_t is not
94 available. The algorithm below extracts a number less than 62**6
95 (approximately 2**35.725) from uint64_t, so ancient hosts where
96 uintmax_t is only 32 bits lose about 3.725 bits of randomness,
97 which is better than not having mkstemp at all. */
98 #if !defined UINT64_MAX && !defined uint64_t
99 # define uint64_t uintmax_t
103 /* Return nonzero if DIR is an existent directory. */
105 direxists (const char *dir)
108 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
111 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
112 non-null and exists, uses it; otherwise uses the first of $TMPDIR,
113 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
114 for use with mk[s]temp. Will fail (-1) if DIR is non-null and
115 doesn't exist, none of the searched dirs exists, or there's not
116 enough space in TMPL. */
118 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
138 d = __secure_getenv ("TMPDIR");
139 if (d != NULL && direxists (d))
141 else if (dir != NULL && direxists (dir))
148 if (direxists (P_tmpdir))
150 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
154 __set_errno (ENOENT);
160 while (dlen > 1 && dir[dlen - 1] == '/')
161 dlen--; /* remove trailing slashes */
163 /* check we have room for "${dir}/${pfx}XXXXXX\0" */
164 if (tmpl_len < dlen + 1 + plen + 6 + 1)
166 __set_errno (EINVAL);
170 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
175 /* These are the characters used in temporary file names. */
176 static const char letters[] =
177 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
180 __try_tempname (char *tmpl, int suffixlen, void *args,
181 int (*tryfunc) (char *, void *))
185 static uint64_t value;
186 uint64_t random_time_bits;
189 int save_errno = errno;
191 /* A lower bound on the number of temporary files to attempt to
192 generate. The maximum total number of temporary file names that
193 can exist for a given template is 62**6. It should never be
194 necessary to try all of these combinations. Instead if a reasonable
195 number of names is tried (we define reasonable as 62**3) fail to
196 give the system administrator the chance to remove the problems. */
197 #define ATTEMPTS_MIN (62 * 62 * 62)
199 /* The number of times to attempt to generate a temporary file. To
200 conform to POSIX, this must be no smaller than TMP_MAX. */
201 #if ATTEMPTS_MIN < TMP_MAX
202 unsigned int attempts = TMP_MAX;
204 unsigned int attempts = ATTEMPTS_MIN;
208 if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
210 __set_errno (EINVAL);
214 /* This is where the Xs start. */
215 XXXXXX = &tmpl[len - 6 - suffixlen];
217 /* Get some more or less random data. */
219 RANDOM_BITS (random_time_bits);
223 __gettimeofday (&tv, NULL);
224 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
227 value += random_time_bits ^ __getpid ();
229 for (count = 0; count < attempts; value += 7777, ++count)
233 /* Fill in the random bits. */
234 XXXXXX[0] = letters[v % 62];
236 XXXXXX[1] = letters[v % 62];
238 XXXXXX[2] = letters[v % 62];
240 XXXXXX[3] = letters[v % 62];
242 XXXXXX[4] = letters[v % 62];
244 XXXXXX[5] = letters[v % 62];
246 fd = tryfunc (tmpl, args);
249 __set_errno (save_errno);
252 else if (errno != EEXIST)
256 /* We got out of the loop because we ran out of combinations to try. */
257 __set_errno (EEXIST);
262 try_file (char *tmpl, void *flags)
264 int *openflags = flags;
266 (*openflags & ~O_ACCMODE)
267 | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
271 try_dir (char *tmpl, void *flags _GL_UNUSED)
273 return __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
277 try_nocreate (char *tmpl, void *flags _GL_UNUSED)
281 if (__lxstat64 (_STAT_VER, tmpl, &st) == 0 || errno == EOVERFLOW)
282 __set_errno (EEXIST);
283 return errno == ENOENT ? 0 : -1;
286 /* Generate a temporary file name based on TMPL. TMPL must match the
287 rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).
288 The name constructed does not exist at the time of the call to
289 __gen_tempname. TMPL is overwritten with the result.
292 __GT_NOCREATE: simply verify that the name does not exist
293 at the time of the call.
294 __GT_FILE: create the file using open(O_CREAT|O_EXCL)
295 and return a read-write fd. The file is mode 0600.
296 __GT_DIR: create a directory, which will be mode 0700.
298 We use a clever algorithm to get hard-to-predict names. */
300 __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
302 int (*tryfunc) (char *, void *);
315 tryfunc = try_nocreate;
319 assert (! "invalid KIND in __gen_tempname");
322 return __try_tempname (tmpl, suffixlen, &flags, tryfunc);