Line data Source code
1 : /* tempname.c - generate the name of a temporary file.
2 :
3 : Copyright (C) 1991-2003, 2005-2007, 2009-2016 Free Software Foundation, Inc.
4 :
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.
9 :
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.
14 :
15 : You should have received a copy of the GNU General Public License
16 : along with this program. If not, see <http://www.gnu.org/licenses/>. */
17 :
18 : /* Extracted from glibc sysdeps/posix/tempname.c. See also tmpdir.c. */
19 :
20 : #if !_LIBC
21 : # include <config.h>
22 : # include "tempname.h"
23 : #endif
24 :
25 : #include <sys/types.h>
26 : #include <assert.h>
27 :
28 : #include <errno.h>
29 : #ifndef __set_errno
30 : # define __set_errno(Val) errno = (Val)
31 : #endif
32 :
33 : #include <stdio.h>
34 : #ifndef P_tmpdir
35 : # define P_tmpdir "/tmp"
36 : #endif
37 : #ifndef TMP_MAX
38 : # define TMP_MAX 238328
39 : #endif
40 : #ifndef __GT_FILE
41 : # define __GT_FILE 0
42 : # define __GT_DIR 1
43 : # define __GT_NOCREATE 2
44 : #endif
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
48 : #endif
49 :
50 : #include <stddef.h>
51 : #include <stdlib.h>
52 : #include <string.h>
53 :
54 : #include <fcntl.h>
55 : #include <sys/time.h>
56 : #include <stdint.h>
57 : #include <unistd.h>
58 :
59 : #include <sys/stat.h>
60 :
61 : #if _LIBC
62 : # define struct_stat64 struct stat64
63 : #else
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
70 : # define __open open
71 : # define __lxstat64(version, file, buf) lstat (file, buf)
72 : # define __secure_getenv secure_getenv
73 : #endif
74 :
75 : #ifdef _LIBC
76 : # include <hp-timing.h>
77 : # if HP_TIMING_AVAIL
78 : # define RANDOM_BITS(Var) \
79 : if (__builtin_expect (value == UINT64_C (0), 0)) \
80 : { \
81 : /* If this is the first time this function is used initialize \
82 : the variable we accumulate the value in to some somewhat \
83 : random value. If we'd not do this programs at startup time \
84 : might have a reduced set of possible names, at least on slow \
85 : machines. */ \
86 : struct timeval tv; \
87 : __gettimeofday (&tv, NULL); \
88 : value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
89 : } \
90 : HP_TIMING_NOW (Var)
91 : # endif
92 : #endif
93 :
94 : /* Use the widest available unsigned type if uint64_t is not
95 : available. The algorithm below extracts a number less than 62**6
96 : (approximately 2**35.725) from uint64_t, so ancient hosts where
97 : uintmax_t is only 32 bits lose about 3.725 bits of randomness,
98 : which is better than not having mkstemp at all. */
99 : #if !defined UINT64_MAX && !defined uint64_t
100 : # define uint64_t uintmax_t
101 : #endif
102 :
103 : #if _LIBC
104 : /* Return nonzero if DIR is an existent directory. */
105 : static int
106 : direxists (const char *dir)
107 : {
108 : struct_stat64 buf;
109 : return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
110 : }
111 :
112 : /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
113 : non-null and exists, uses it; otherwise uses the first of $TMPDIR,
114 : P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
115 : for use with mk[s]temp. Will fail (-1) if DIR is non-null and
116 : doesn't exist, none of the searched dirs exists, or there's not
117 : enough space in TMPL. */
118 : int
119 : __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
120 : int try_tmpdir)
121 : {
122 : const char *d;
123 : size_t dlen, plen;
124 :
125 : if (!pfx || !pfx[0])
126 : {
127 : pfx = "file";
128 : plen = 4;
129 : }
130 : else
131 : {
132 : plen = strlen (pfx);
133 : if (plen > 5)
134 : plen = 5;
135 : }
136 :
137 : if (try_tmpdir)
138 : {
139 : d = __secure_getenv ("TMPDIR");
140 : if (d != NULL && direxists (d))
141 : dir = d;
142 : else if (dir != NULL && direxists (dir))
143 : /* nothing */ ;
144 : else
145 : dir = NULL;
146 : }
147 : if (dir == NULL)
148 : {
149 : if (direxists (P_tmpdir))
150 : dir = P_tmpdir;
151 : else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
152 : dir = "/tmp";
153 : else
154 : {
155 : __set_errno (ENOENT);
156 : return -1;
157 : }
158 : }
159 :
160 : dlen = strlen (dir);
161 : while (dlen > 1 && dir[dlen - 1] == '/')
162 : dlen--; /* remove trailing slashes */
163 :
164 : /* check we have room for "${dir}/${pfx}XXXXXX\0" */
165 : if (tmpl_len < dlen + 1 + plen + 6 + 1)
166 : {
167 : __set_errno (EINVAL);
168 : return -1;
169 : }
170 :
171 : sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
172 : return 0;
173 : }
174 : #endif /* _LIBC */
175 :
176 : /* These are the characters used in temporary file names. */
177 : static const char letters[] =
178 : "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
179 :
180 : int
181 0 : __try_tempname (char *tmpl, int suffixlen, void *args,
182 : int (*tryfunc) (char *, void *))
183 : {
184 : int len;
185 : char *XXXXXX;
186 : static uint64_t value;
187 : uint64_t random_time_bits;
188 : unsigned int count;
189 0 : int fd = -1;
190 0 : int save_errno = errno;
191 :
192 : /* A lower bound on the number of temporary files to attempt to
193 : generate. The maximum total number of temporary file names that
194 : can exist for a given template is 62**6. It should never be
195 : necessary to try all of these combinations. Instead if a reasonable
196 : number of names is tried (we define reasonable as 62**3) fail to
197 : give the system administrator the chance to remove the problems. */
198 : #define ATTEMPTS_MIN (62 * 62 * 62)
199 :
200 : /* The number of times to attempt to generate a temporary file. To
201 : conform to POSIX, this must be no smaller than TMP_MAX. */
202 : #if ATTEMPTS_MIN < TMP_MAX
203 : unsigned int attempts = TMP_MAX;
204 : #else
205 0 : unsigned int attempts = ATTEMPTS_MIN;
206 : #endif
207 :
208 0 : len = strlen (tmpl);
209 0 : if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
210 : {
211 0 : __set_errno (EINVAL);
212 0 : return -1;
213 : }
214 :
215 : /* This is where the Xs start. */
216 0 : XXXXXX = &tmpl[len - 6 - suffixlen];
217 :
218 : /* Get some more or less random data. */
219 : #ifdef RANDOM_BITS
220 : RANDOM_BITS (random_time_bits);
221 : #else
222 : {
223 : struct timeval tv;
224 0 : __gettimeofday (&tv, NULL);
225 0 : random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
226 : }
227 : #endif
228 0 : value += random_time_bits ^ __getpid ();
229 :
230 0 : for (count = 0; count < attempts; value += 7777, ++count)
231 : {
232 0 : uint64_t v = value;
233 :
234 : /* Fill in the random bits. */
235 0 : XXXXXX[0] = letters[v % 62];
236 0 : v /= 62;
237 0 : XXXXXX[1] = letters[v % 62];
238 0 : v /= 62;
239 0 : XXXXXX[2] = letters[v % 62];
240 0 : v /= 62;
241 0 : XXXXXX[3] = letters[v % 62];
242 0 : v /= 62;
243 0 : XXXXXX[4] = letters[v % 62];
244 0 : v /= 62;
245 0 : XXXXXX[5] = letters[v % 62];
246 :
247 0 : fd = tryfunc (tmpl, args);
248 0 : if (fd >= 0)
249 : {
250 0 : __set_errno (save_errno);
251 0 : return fd;
252 : }
253 0 : else if (errno != EEXIST)
254 0 : return -1;
255 : }
256 :
257 : /* We got out of the loop because we ran out of combinations to try. */
258 0 : __set_errno (EEXIST);
259 0 : return -1;
260 : }
261 :
262 : static int
263 0 : try_file (char *tmpl, void *flags)
264 : {
265 0 : int *openflags = flags;
266 0 : return __open (tmpl,
267 0 : (*openflags & ~O_ACCMODE)
268 0 : | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
269 : }
270 :
271 : static int
272 0 : try_dir (char *tmpl, void *flags _GL_UNUSED)
273 : {
274 0 : return __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
275 : }
276 :
277 : static int
278 0 : try_nocreate (char *tmpl, void *flags _GL_UNUSED)
279 : {
280 : struct_stat64 st;
281 :
282 0 : if (__lxstat64 (_STAT_VER, tmpl, &st) == 0)
283 0 : __set_errno (EEXIST);
284 0 : return errno == ENOENT ? 0 : -1;
285 : }
286 :
287 : /* Generate a temporary file name based on TMPL. TMPL must match the
288 : rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).
289 : The name constructed does not exist at the time of the call to
290 : __gen_tempname. TMPL is overwritten with the result.
291 :
292 : KIND may be one of:
293 : __GT_NOCREATE: simply verify that the name does not exist
294 : at the time of the call.
295 : __GT_FILE: create the file using open(O_CREAT|O_EXCL)
296 : and return a read-write fd. The file is mode 0600.
297 : __GT_DIR: create a directory, which will be mode 0700.
298 :
299 : We use a clever algorithm to get hard-to-predict names. */
300 : int
301 0 : __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
302 : {
303 : int (*tryfunc) (char *, void *);
304 :
305 0 : switch (kind)
306 : {
307 : case __GT_FILE:
308 0 : tryfunc = try_file;
309 0 : break;
310 :
311 : case __GT_DIR:
312 0 : tryfunc = try_dir;
313 0 : break;
314 :
315 : case __GT_NOCREATE:
316 0 : tryfunc = try_nocreate;
317 0 : break;
318 :
319 : default:
320 0 : assert (! "invalid KIND in __gen_tempname");
321 : abort ();
322 : }
323 0 : return __try_tempname (tmpl, suffixlen, &flags, tryfunc);
324 : }
|
