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, 2005 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
19 #include <sys/cdefs.h>
20 __RCSID("$NetBSD: tempname.c,v 1.2 2016/05/17 14:00:09 christos Exp $");
21
22
23 #ifdef HAVE_CONFIG_H
24 # include <config.h>
25 #endif
26
27 #include <sys/types.h>
28 #include <assert.h>
29
30 #include <errno.h>
31 #ifndef __set_errno
32 # define __set_errno(Val) errno = (Val)
33 #endif
34
35 #include <stdio.h>
36 #ifndef P_tmpdir
37 # define P_tmpdir "/tmp"
38 #endif
39 #ifndef TMP_MAX
40 # define TMP_MAX 238328
41 #endif
42 #ifndef __GT_FILE
43 # define __GT_FILE 0
44 # define __GT_BIGFILE 1
45 # define __GT_DIR 2
46 # define __GT_NOCREATE 3
47 #endif
48
49 #include <stddef.h>
50 #include <stdlib.h>
51 #include <string.h>
52
53 #include <fcntl.h>
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 #if HAVE_INTTYPES_H
63 # include <inttypes.h>
64 #endif
65
66 #if HAVE_UNISTD_H || _LIBC
67 # include <unistd.h>
68 #endif
69
70 #include <sys/stat.h>
71
72 #if _LIBC
73 # define struct_stat64 struct stat64
74 #else
75 # include "stat-macros.h"
76 # define struct_stat64 struct stat
77 # define __getpid getpid
78 # define __gettimeofday gettimeofday
79 # define __mkdir mkdir
80 # define __open open
81 # define __open64 open
82 # define __lxstat64(version, file, buf) lstat (file, buf)
83 # define __xstat64(version, file, buf) stat (file, buf)
84 #endif
85
86 #if ! (HAVE___SECURE_GETENV || _LIBC)
87 # define __secure_getenv getenv
88 #endif
89
90 #ifdef _LIBC
91 # include <hp-timing.h>
92 # if HP_TIMING_AVAIL
93 # define RANDOM_BITS(Var) \
94 if (__builtin_expect (value == UINT64_C (0), 0)) \
95 { \
96 /* If this is the first time this function is used initialize \
97 the variable we accumulate the value in to some somewhat \
98 random value. If we'd not do this programs at startup time \
99 might have a reduced set of possible names, at least on slow \
100 machines. */ \
101 struct timeval tv; \
102 __gettimeofday (&tv, NULL); \
103 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
104 } \
105 HP_TIMING_NOW (Var)
106 # endif
107 #endif
108
109 /* Use the widest available unsigned type if uint64_t is not
110 available. The algorithm below extracts a number less than 62**6
111 (approximately 2**35.725) from uint64_t, so ancient hosts where
112 uintmax_t is only 32 bits lose about 3.725 bits of randomness,
113 which is better than not having mkstemp at all. */
114 #if !defined UINT64_MAX && !defined uint64_t
115 # define uint64_t uintmax_t
116 #endif
117
118 /* Return nonzero if DIR is an existent directory. */
119 static int
direxists(const char * dir)120 direxists (const char *dir)
121 {
122 struct_stat64 buf;
123 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
124 }
125
126 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
127 non-null and exists, uses it; otherwise uses the first of $TMPDIR,
128 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
129 for use with mk[s]temp. Will fail (-1) if DIR is non-null and
130 doesn't exist, none of the searched dirs exists, or there's not
131 enough space in TMPL. */
132 int
__path_search(char * tmpl,size_t tmpl_len,const char * dir,const char * pfx,int try_tmpdir)133 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
134 int try_tmpdir)
135 {
136 const char *d;
137 size_t dlen, plen;
138
139 if (!pfx || !pfx[0])
140 {
141 pfx = "file";
142 plen = 4;
143 }
144 else
145 {
146 plen = strlen (pfx);
147 if (plen > 5)
148 plen = 5;
149 }
150
151 if (try_tmpdir)
152 {
153 d = __secure_getenv ("TMPDIR");
154 if (d != NULL && direxists (d))
155 dir = d;
156 else if (dir != NULL && direxists (dir))
157 /* nothing */ ;
158 else
159 dir = NULL;
160 }
161 if (dir == NULL)
162 {
163 if (direxists (P_tmpdir))
164 dir = P_tmpdir;
165 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
166 dir = "/tmp";
167 else
168 {
169 __set_errno (ENOENT);
170 return -1;
171 }
172 }
173
174 dlen = strlen (dir);
175 while (dlen > 1 && dir[dlen - 1] == '/')
176 dlen--; /* remove trailing slashes */
177
178 /* check we have room for "${dir}/${pfx}XXXXXX\0" */
179 if (tmpl_len < dlen + 1 + plen + 6 + 1)
180 {
181 __set_errno (EINVAL);
182 return -1;
183 }
184
185 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
186 return 0;
187 }
188
189 /* These are the characters used in temporary file names. */
190 static const char letters[] =
191 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
192
193 /* Generate a temporary file name based on TMPL. TMPL must match the
194 rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed
195 does not exist at the time of the call to __gen_tempname. TMPL is
196 overwritten with the result.
197
198 KIND may be one of:
199 __GT_NOCREATE: simply verify that the name does not exist
200 at the time of the call.
201 __GT_FILE: create the file using open(O_CREAT|O_EXCL)
202 and return a read-write fd. The file is mode 0600.
203 __GT_BIGFILE: same as __GT_FILE but use open64().
204 __GT_DIR: create a directory, which will be mode 0700.
205
206 We use a clever algorithm to get hard-to-predict names. */
207 int
__gen_tempname(char * tmpl,int kind)208 __gen_tempname (char *tmpl, int kind)
209 {
210 int len;
211 char *XXXXXX;
212 static uint64_t value;
213 uint64_t random_time_bits;
214 unsigned int count;
215 int fd = -1;
216 int save_errno = errno;
217 struct_stat64 st;
218
219 /* A lower bound on the number of temporary files to attempt to
220 generate. The maximum total number of temporary file names that
221 can exist for a given template is 62**6. It should never be
222 necessary to try all these combinations. Instead if a reasonable
223 number of names is tried (we define reasonable as 62**3) fail to
224 give the system administrator the chance to remove the problems. */
225 unsigned int attempts_min = 62 * 62 * 62;
226
227 /* The number of times to attempt to generate a temporary file. To
228 conform to POSIX, this must be no smaller than TMP_MAX. */
229 unsigned int attempts = attempts_min < TMP_MAX ? TMP_MAX : attempts_min;
230
231 len = strlen (tmpl);
232 if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
233 {
234 __set_errno (EINVAL);
235 return -1;
236 }
237
238 /* This is where the Xs start. */
239 XXXXXX = &tmpl[len - 6];
240
241 /* Get some more or less random data. */
242 #ifdef RANDOM_BITS
243 RANDOM_BITS (random_time_bits);
244 #else
245 # if HAVE_GETTIMEOFDAY || _LIBC
246 {
247 struct timeval tv;
248 __gettimeofday (&tv, NULL);
249 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
250 }
251 # else
252 random_time_bits = time (NULL);
253 # endif
254 #endif
255 value += random_time_bits ^ __getpid ();
256
257 for (count = 0; count < attempts; value += 7777, ++count)
258 {
259 uint64_t v = value;
260
261 /* Fill in the random bits. */
262 XXXXXX[0] = letters[v % 62];
263 v /= 62;
264 XXXXXX[1] = letters[v % 62];
265 v /= 62;
266 XXXXXX[2] = letters[v % 62];
267 v /= 62;
268 XXXXXX[3] = letters[v % 62];
269 v /= 62;
270 XXXXXX[4] = letters[v % 62];
271 v /= 62;
272 XXXXXX[5] = letters[v % 62];
273
274 switch (kind)
275 {
276 case __GT_FILE:
277 fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
278 break;
279
280 case __GT_BIGFILE:
281 fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
282 break;
283
284 case __GT_DIR:
285 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
286 break;
287
288 case __GT_NOCREATE:
289 /* This case is backward from the other three. __gen_tempname
290 succeeds if __xstat fails because the name does not exist.
291 Note the continue to bypass the common logic at the bottom
292 of the loop. */
293 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
294 {
295 if (errno == ENOENT)
296 {
297 __set_errno (save_errno);
298 return 0;
299 }
300 else
301 /* Give up now. */
302 return -1;
303 }
304 continue;
305
306 default:
307 assert (! "invalid KIND in __gen_tempname");
308 }
309
310 if (fd >= 0)
311 {
312 __set_errno (save_errno);
313 return fd;
314 }
315 else if (errno != EEXIST)
316 return -1;
317 }
318
319 /* We got out of the loop because we ran out of combinations to try. */
320 __set_errno (EEXIST);
321 return -1;
322 }
323