Line data Source code
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 : # include "randint.h"
26 : #endif
27 :
28 : #include <sys/types.h>
29 : #include <assert.h>
30 :
31 : #include <errno.h>
32 : #ifndef __set_errno
33 : # define __set_errno(Val) errno = (Val)
34 : #endif
35 :
36 : #include <stdio.h>
37 : #ifndef P_tmpdir
38 : # define P_tmpdir "/tmp"
39 : #endif
40 : #ifndef TMP_MAX
41 : # define TMP_MAX 238328
42 : #endif
43 : #ifndef __GT_FILE
44 : # define __GT_FILE 0
45 : # define __GT_BIGFILE 1
46 : # define __GT_DIR 2
47 : # define __GT_NOCREATE 3
48 : #endif
49 :
50 : #include <stdbool.h>
51 : #include <stddef.h>
52 : #include <stdlib.h>
53 : #include <string.h>
54 :
55 : #include <fcntl.h>
56 : #include <sys/time.h>
57 : #include <stdint.h>
58 : #include <unistd.h>
59 :
60 : #include <sys/stat.h>
61 :
62 : #if _LIBC
63 : # define struct_stat64 struct stat64
64 : # define small_open __open
65 : # define large_open __open64
66 : #else
67 : # define struct_stat64 struct stat
68 : # define small_open open
69 : # define large_open open
70 : # define __gen_tempname gen_tempname
71 : # define __getpid getpid
72 : # define __gettimeofday gettimeofday
73 : # define __mkdir mkdir
74 : # define __lxstat64(version, file, buf) lstat (file, buf)
75 : # define __xstat64(version, file, buf) stat (file, buf)
76 : #endif
77 :
78 : #if ! (HAVE___SECURE_GETENV || _LIBC)
79 : # define __secure_getenv getenv
80 : #endif
81 :
82 : #if _LIBC
83 : /* Return nonzero if DIR is an existent directory. */
84 : static int
85 : direxists (const char *dir)
86 : {
87 : struct_stat64 buf;
88 : return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
89 : }
90 :
91 : /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
92 : non-null and exists, uses it; otherwise uses the first of $TMPDIR,
93 : P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
94 : for use with mk[s]temp. Will fail (-1) if DIR is non-null and
95 : doesn't exist, none of the searched dirs exists, or there's not
96 : enough space in TMPL. */
97 : int
98 : __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
99 : int try_tmpdir)
100 : {
101 : const char *d;
102 : size_t dlen, plen;
103 :
104 : if (!pfx || !pfx[0])
105 : {
106 : pfx = "file";
107 : plen = 4;
108 : }
109 : else
110 : {
111 : plen = strlen (pfx);
112 : if (plen > 5)
113 : plen = 5;
114 : }
115 :
116 : if (try_tmpdir)
117 : {
118 : d = __secure_getenv ("TMPDIR");
119 : if (d != NULL && direxists (d))
120 : dir = d;
121 : else if (dir != NULL && direxists (dir))
122 : /* nothing */ ;
123 : else
124 : dir = NULL;
125 : }
126 : if (dir == NULL)
127 : {
128 : if (direxists (P_tmpdir))
129 : dir = P_tmpdir;
130 : else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
131 : dir = "/tmp";
132 : else
133 : {
134 : __set_errno (ENOENT);
135 : return -1;
136 : }
137 : }
138 :
139 : dlen = strlen (dir);
140 : while (dlen > 1 && dir[dlen - 1] == '/')
141 : dlen--; /* remove trailing slashes */
142 :
143 : /* check we have room for "${dir}/${pfx}XXXXXX\0" */
144 : if (tmpl_len < dlen + 1 + plen + 6 + 1)
145 : {
146 : __set_errno (EINVAL);
147 : return -1;
148 : }
149 :
150 : sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
151 : return 0;
152 : }
153 : #endif /* _LIBC */
154 :
155 : static inline bool
156 18 : check_x_suffix (char const *s, size_t len)
157 : {
158 18 : return strspn (s, "X") == len;
159 : }
160 :
161 : /* These are the characters used in temporary file names. */
162 : static const char letters[] =
163 : "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
164 :
165 : /* Generate a temporary file name based on TMPL. TMPL must end in a
166 : a sequence of at least X_SUFFIX_LEN "X"s. The name constructed
167 : does not exist at the time of the call to __gen_tempname. TMPL is
168 : overwritten with the result.
169 :
170 : KIND may be one of:
171 : __GT_NOCREATE: simply verify that the name does not exist
172 : at the time of the call.
173 : __GT_FILE: create the file using open(O_CREAT|O_EXCL)
174 : and return a read-write fd. The file is mode 0600.
175 : __GT_BIGFILE: same as __GT_FILE but use open64().
176 : __GT_DIR: create a directory, which will be mode 0700.
177 :
178 : We use a clever algorithm to get hard-to-predict names. */
179 : int
180 18 : gen_tempname_len (char *tmpl, int kind, size_t x_suffix_len)
181 : {
182 : size_t len;
183 : char *XXXXXX;
184 : unsigned int count;
185 18 : int fd = -1;
186 18 : int save_errno = errno;
187 : struct_stat64 st;
188 : struct randint_source *rand_src;
189 :
190 : /* A lower bound on the number of temporary files to attempt to
191 : generate. The maximum total number of temporary file names that
192 : can exist for a given template is 62**6. It should never be
193 : necessary to try all these combinations. Instead if a reasonable
194 : number of names is tried (we define reasonable as 62**3) fail to
195 : give the system administrator the chance to remove the problems. */
196 : #define ATTEMPTS_MIN (62 * 62 * 62)
197 :
198 : /* The number of times to attempt to generate a temporary file. To
199 : conform to POSIX, this must be no smaller than TMP_MAX. */
200 : #if ATTEMPTS_MIN < TMP_MAX
201 : unsigned int attempts = TMP_MAX;
202 : #else
203 18 : unsigned int attempts = ATTEMPTS_MIN;
204 : #endif
205 :
206 18 : len = strlen (tmpl);
207 18 : if (len < x_suffix_len || ! check_x_suffix (&tmpl[len - x_suffix_len],
208 : x_suffix_len))
209 : {
210 0 : __set_errno (EINVAL);
211 0 : return -1;
212 : }
213 :
214 18 : rand_src = randint_all_new (NULL, 8);
215 18 : if (! rand_src)
216 0 : return -1;
217 :
218 : /* This is where the Xs start. */
219 18 : XXXXXX = &tmpl[len - x_suffix_len];
220 :
221 18 : for (count = 0; count < attempts; ++count)
222 : {
223 : size_t i;
224 :
225 185 : for (i = 0; i < x_suffix_len; i++)
226 : {
227 167 : XXXXXX[i] = letters[randint_genmax (rand_src, sizeof letters - 2)];
228 : }
229 :
230 18 : switch (kind)
231 : {
232 0 : case __GT_FILE:
233 0 : fd = small_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
234 0 : break;
235 :
236 13 : case __GT_BIGFILE:
237 13 : fd = large_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
238 13 : break;
239 :
240 1 : case __GT_DIR:
241 1 : fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
242 1 : break;
243 :
244 4 : case __GT_NOCREATE:
245 : /* This case is backward from the other three. This function
246 : succeeds if __xstat fails because the name does not exist.
247 : Note the continue to bypass the common logic at the bottom
248 : of the loop. */
249 4 : if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
250 : {
251 4 : if (errno == ENOENT)
252 : {
253 3 : __set_errno (save_errno);
254 3 : fd = 0;
255 3 : goto done;
256 : }
257 : else
258 : {
259 : /* Give up now. */
260 1 : fd = -1;
261 1 : goto done;
262 : }
263 : }
264 0 : continue;
265 :
266 0 : default:
267 0 : assert (! "invalid KIND in __gen_tempname");
268 : }
269 :
270 14 : if (fd >= 0)
271 : {
272 9 : __set_errno (save_errno);
273 9 : goto done;
274 : }
275 5 : else if (errno != EEXIST)
276 : {
277 5 : fd = -1;
278 5 : goto done;
279 : }
280 : }
281 :
282 0 : randint_all_free (rand_src);
283 :
284 : /* We got out of the loop because we ran out of combinations to try. */
285 0 : __set_errno (EEXIST);
286 0 : return -1;
287 :
288 18 : done:
289 : {
290 18 : int saved_errno = errno;
291 18 : randint_all_free (rand_src);
292 18 : __set_errno (saved_errno);
293 : }
294 18 : return fd;
295 : }
296 :
297 : int
298 0 : __gen_tempname (char *tmpl, int kind)
299 : {
300 0 : return gen_tempname_len (tmpl, kind, 6);
301 : }
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