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