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, 2006, 2007 Free Software Foundation,
5 Inc.
6
7 This program is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>. */
19
20 /* Extracted from glibc sysdeps/posix/tempname.c. See also tmpdir.c. */
21
22 #if !_LIBC
23 # include <config.h>
24 # include "tempname.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 #include <sys/time.h>
55 #include <stdint.h>
56 #include <unistd.h>
57
58 #include <sys/stat.h>
59
60 #if _LIBC
61 # define struct_stat64 struct stat64
62 # define small_open __open
63 # define large_open __open64
64 #else
65 # define struct_stat64 struct stat
66 # define small_open open
67 # define large_open open
68 # define __gen_tempname gen_tempname
69 # define __getpid getpid
70 # define __gettimeofday gettimeofday
71 # define __mkdir mkdir
72 # define __lxstat64(version, file, buf) lstat (file, buf)
73 # define __xstat64(version, file, buf) stat (file, buf)
74 #endif
75
76 #if ! (HAVE___SECURE_GETENV || _LIBC)
77 # define __secure_getenv getenv
78 #endif
79
80 #ifdef _LIBC
81 # include <hp-timing.h>
82 # if HP_TIMING_AVAIL
83 # define RANDOM_BITS(Var) \
84 if (__builtin_expect (value == UINT64_C (0), 0)) \
85 { \
86 /* If this is the first time this function is used initialize \
87 the variable we accumulate the value in to some somewhat \
88 random value. If we'd not do this programs at startup time \
89 might have a reduced set of possible names, at least on slow \
90 machines. */ \
91 struct timeval tv; \
92 __gettimeofday (&tv, NULL); \
93 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
94 } \
95 HP_TIMING_NOW (Var)
96 # endif
97 #endif
98
99 /* Use the widest available unsigned type if uint64_t is not
100 available. The algorithm below extracts a number less than 62**6
101 (approximately 2**35.725) from uint64_t, so ancient hosts where
102 uintmax_t is only 32 bits lose about 3.725 bits of randomness,
103 which is better than not having mkstemp at all. */
104 #if !defined UINT64_MAX && !defined uint64_t
105 # define uint64_t uintmax_t
106 #endif
107
108 #if _LIBC
109 /* Return nonzero if DIR is an existent directory. */
110 static int
direxists(const char * dir)111 direxists (const char *dir)
112 {
113 struct_stat64 buf;
114 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
115 }
116
117 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
118 non-null and exists, uses it; otherwise uses the first of $TMPDIR,
119 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
120 for use with mk[s]temp. Will fail (-1) if DIR is non-null and
121 doesn't exist, none of the searched dirs exists, or there's not
122 enough space in TMPL. */
123 int
__path_search(char * tmpl,size_t tmpl_len,const char * dir,const char * pfx,int try_tmpdir)124 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
125 int try_tmpdir)
126 {
127 const char *d;
128 size_t dlen, plen;
129
130 if (!pfx || !pfx[0])
131 {
132 pfx = "file";
133 plen = 4;
134 }
135 else
136 {
137 plen = strlen (pfx);
138 if (plen > 5)
139 plen = 5;
140 }
141
142 if (try_tmpdir)
143 {
144 d = __secure_getenv ("TMPDIR");
145 if (d != NULL && direxists (d))
146 dir = d;
147 else if (dir != NULL && direxists (dir))
148 /* nothing */ ;
149 else
150 dir = NULL;
151 }
152 if (dir == NULL)
153 {
154 if (direxists (P_tmpdir))
155 dir = P_tmpdir;
156 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
157 dir = "/tmp";
158 else
159 {
160 __set_errno (ENOENT);
161 return -1;
162 }
163 }
164
165 dlen = strlen (dir);
166 while (dlen > 1 && dir[dlen - 1] == '/')
167 dlen--; /* remove trailing slashes */
168
169 /* check we have room for "${dir}/${pfx}XXXXXX\0" */
170 if (tmpl_len < dlen + 1 + plen + 6 + 1)
171 {
172 __set_errno (EINVAL);
173 return -1;
174 }
175
176 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
177 return 0;
178 }
179 #endif /* _LIBC */
180
181 /* These are the characters used in temporary file names. */
182 static const char letters[] =
183 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
184
185 /* Generate a temporary file name based on TMPL. TMPL must match the
186 rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed
187 does not exist at the time of the call to __gen_tempname. TMPL is
188 overwritten with the result.
189
190 KIND may be one of:
191 __GT_NOCREATE: simply verify that the name does not exist
192 at the time of the call.
193 __GT_FILE: create the file using open(O_CREAT|O_EXCL)
194 and return a read-write fd. The file is mode 0600.
195 __GT_BIGFILE: same as __GT_FILE but use open64().
196 __GT_DIR: create a directory, which will be mode 0700.
197
198 We use a clever algorithm to get hard-to-predict names. */
199 int
__gen_tempname(char * tmpl,int kind)200 __gen_tempname (char *tmpl, int kind)
201 {
202 int len;
203 char *XXXXXX;
204 static uint64_t value;
205 uint64_t random_time_bits;
206 unsigned int count;
207 int fd = -1;
208 int save_errno = errno;
209 struct_stat64 st;
210
211 /* A lower bound on the number of temporary files to attempt to
212 generate. The maximum total number of temporary file names that
213 can exist for a given template is 62**6. It should never be
214 necessary to try all these combinations. Instead if a reasonable
215 number of names is tried (we define reasonable as 62**3) fail to
216 give the system administrator the chance to remove the problems. */
217 #define ATTEMPTS_MIN (62 * 62 * 62)
218
219 /* The number of times to attempt to generate a temporary file. To
220 conform to POSIX, this must be no smaller than TMP_MAX. */
221 #if ATTEMPTS_MIN < TMP_MAX
222 unsigned int attempts = TMP_MAX;
223 #else
224 unsigned int attempts = ATTEMPTS_MIN;
225 #endif
226
227 len = strlen (tmpl);
228 if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
229 {
230 __set_errno (EINVAL);
231 return -1;
232 }
233
234 /* This is where the Xs start. */
235 XXXXXX = &tmpl[len - 6];
236
237 /* Get some more or less random data. */
238 #ifdef RANDOM_BITS
239 RANDOM_BITS (random_time_bits);
240 #else
241 {
242 struct timeval tv;
243 __gettimeofday (&tv, NULL);
244 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
245 }
246 #endif
247 value += random_time_bits ^ __getpid ();
248
249 for (count = 0; count < attempts; value += 7777, ++count)
250 {
251 uint64_t v = value;
252
253 /* Fill in the random bits. */
254 XXXXXX[0] = letters[v % 62];
255 v /= 62;
256 XXXXXX[1] = letters[v % 62];
257 v /= 62;
258 XXXXXX[2] = letters[v % 62];
259 v /= 62;
260 XXXXXX[3] = letters[v % 62];
261 v /= 62;
262 XXXXXX[4] = letters[v % 62];
263 v /= 62;
264 XXXXXX[5] = letters[v % 62];
265
266 switch (kind)
267 {
268 case __GT_FILE:
269 fd = small_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
270 break;
271
272 case __GT_BIGFILE:
273 fd = large_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
274 break;
275
276 case __GT_DIR:
277 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
278 break;
279
280 case __GT_NOCREATE:
281 /* This case is backward from the other three. __gen_tempname
282 succeeds if __xstat fails because the name does not exist.
283 Note the continue to bypass the common logic at the bottom
284 of the loop. */
285 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
286 {
287 if (errno == ENOENT)
288 {
289 __set_errno (save_errno);
290 return 0;
291 }
292 else
293 /* Give up now. */
294 return -1;
295 }
296 continue;
297
298 default:
299 assert (! "invalid KIND in __gen_tempname");
300 }
301
302 if (fd >= 0)
303 {
304 __set_errno (save_errno);
305 return fd;
306 }
307 else if (errno != EEXIST)
308 return -1;
309 }
310
311 /* We got out of the loop because we ran out of combinations to try. */
312 __set_errno (EEXIST);
313 return -1;
314 }
315