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