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1 | /* tempname.c - generate the name of a temporary file. |
2 | ||
7a6dbc2f | 3 | Copyright (C) 1991-2003, 2005-2007, 2009-2018 Free Software Foundation, Inc. |
2d8adcbd MM |
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 | |
7a6dbc2f | 16 | along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
2d8adcbd MM |
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) | |
2d8adcbd MM |
72 | #endif |
73 | ||
74 | #ifdef _LIBC | |
75 | # include <hp-timing.h> | |
76 | # if HP_TIMING_AVAIL | |
77 | # define RANDOM_BITS(Var) \ | |
78 | if (__builtin_expect (value == UINT64_C (0), 0)) \ | |
79 | { \ | |
80 | /* If this is the first time this function is used initialize \ | |
81 | the variable we accumulate the value in to some somewhat \ | |
82 | random value. If we'd not do this programs at startup time \ | |
83 | might have a reduced set of possible names, at least on slow \ | |
84 | machines. */ \ | |
85 | struct timeval tv; \ | |
86 | __gettimeofday (&tv, NULL); \ | |
87 | value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \ | |
88 | } \ | |
89 | HP_TIMING_NOW (Var) | |
90 | # endif | |
91 | #endif | |
92 | ||
93 | /* Use the widest available unsigned type if uint64_t is not | |
94 | available. The algorithm below extracts a number less than 62**6 | |
95 | (approximately 2**35.725) from uint64_t, so ancient hosts where | |
96 | uintmax_t is only 32 bits lose about 3.725 bits of randomness, | |
97 | which is better than not having mkstemp at all. */ | |
98 | #if !defined UINT64_MAX && !defined uint64_t | |
99 | # define uint64_t uintmax_t | |
100 | #endif | |
101 | ||
102 | #if _LIBC | |
103 | /* Return nonzero if DIR is an existent directory. */ | |
104 | static int | |
105 | direxists (const char *dir) | |
106 | { | |
107 | struct_stat64 buf; | |
108 | return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode); | |
109 | } | |
110 | ||
111 | /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is | |
112 | non-null and exists, uses it; otherwise uses the first of $TMPDIR, | |
113 | P_tmpdir, /tmp that exists. Copies into TMPL a template suitable | |
114 | for use with mk[s]temp. Will fail (-1) if DIR is non-null and | |
115 | doesn't exist, none of the searched dirs exists, or there's not | |
116 | enough space in TMPL. */ | |
117 | int | |
118 | __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx, | |
119 | int try_tmpdir) | |
120 | { | |
121 | const char *d; | |
122 | size_t dlen, plen; | |
123 | ||
124 | if (!pfx || !pfx[0]) | |
125 | { | |
126 | pfx = "file"; | |
127 | plen = 4; | |
128 | } | |
129 | else | |
130 | { | |
131 | plen = strlen (pfx); | |
132 | if (plen > 5) | |
133 | plen = 5; | |
134 | } | |
135 | ||
136 | if (try_tmpdir) | |
137 | { | |
138 | d = __secure_getenv ("TMPDIR"); | |
139 | if (d != NULL && direxists (d)) | |
140 | dir = d; | |
141 | else if (dir != NULL && direxists (dir)) | |
142 | /* nothing */ ; | |
143 | else | |
144 | dir = NULL; | |
145 | } | |
146 | if (dir == NULL) | |
147 | { | |
148 | if (direxists (P_tmpdir)) | |
149 | dir = P_tmpdir; | |
150 | else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp")) | |
151 | dir = "/tmp"; | |
152 | else | |
153 | { | |
154 | __set_errno (ENOENT); | |
155 | return -1; | |
156 | } | |
157 | } | |
158 | ||
159 | dlen = strlen (dir); | |
160 | while (dlen > 1 && dir[dlen - 1] == '/') | |
161 | dlen--; /* remove trailing slashes */ | |
162 | ||
163 | /* check we have room for "${dir}/${pfx}XXXXXX\0" */ | |
164 | if (tmpl_len < dlen + 1 + plen + 6 + 1) | |
165 | { | |
166 | __set_errno (EINVAL); | |
167 | return -1; | |
168 | } | |
169 | ||
170 | sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx); | |
171 | return 0; | |
172 | } | |
173 | #endif /* _LIBC */ | |
174 | ||
175 | /* These are the characters used in temporary file names. */ | |
176 | static const char letters[] = | |
177 | "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; | |
178 | ||
179 | int | |
180 | __try_tempname (char *tmpl, int suffixlen, void *args, | |
181 | int (*tryfunc) (char *, void *)) | |
182 | { | |
183 | int len; | |
184 | char *XXXXXX; | |
185 | static uint64_t value; | |
186 | uint64_t random_time_bits; | |
187 | unsigned int count; | |
188 | int fd = -1; | |
189 | int save_errno = errno; | |
190 | ||
191 | /* A lower bound on the number of temporary files to attempt to | |
192 | generate. The maximum total number of temporary file names that | |
193 | can exist for a given template is 62**6. It should never be | |
194 | necessary to try all of these combinations. Instead if a reasonable | |
195 | number of names is tried (we define reasonable as 62**3) fail to | |
196 | give the system administrator the chance to remove the problems. */ | |
197 | #define ATTEMPTS_MIN (62 * 62 * 62) | |
198 | ||
199 | /* The number of times to attempt to generate a temporary file. To | |
200 | conform to POSIX, this must be no smaller than TMP_MAX. */ | |
201 | #if ATTEMPTS_MIN < TMP_MAX | |
202 | unsigned int attempts = TMP_MAX; | |
203 | #else | |
204 | unsigned int attempts = ATTEMPTS_MIN; | |
205 | #endif | |
206 | ||
207 | len = strlen (tmpl); | |
208 | if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6)) | |
209 | { | |
210 | __set_errno (EINVAL); | |
211 | return -1; | |
212 | } | |
213 | ||
214 | /* This is where the Xs start. */ | |
215 | XXXXXX = &tmpl[len - 6 - suffixlen]; | |
216 | ||
217 | /* Get some more or less random data. */ | |
218 | #ifdef RANDOM_BITS | |
219 | RANDOM_BITS (random_time_bits); | |
220 | #else | |
221 | { | |
222 | struct timeval tv; | |
223 | __gettimeofday (&tv, NULL); | |
224 | random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; | |
225 | } | |
226 | #endif | |
227 | value += random_time_bits ^ __getpid (); | |
228 | ||
229 | for (count = 0; count < attempts; value += 7777, ++count) | |
230 | { | |
231 | uint64_t v = value; | |
232 | ||
233 | /* Fill in the random bits. */ | |
234 | XXXXXX[0] = letters[v % 62]; | |
235 | v /= 62; | |
236 | XXXXXX[1] = letters[v % 62]; | |
237 | v /= 62; | |
238 | XXXXXX[2] = letters[v % 62]; | |
239 | v /= 62; | |
240 | XXXXXX[3] = letters[v % 62]; | |
241 | v /= 62; | |
242 | XXXXXX[4] = letters[v % 62]; | |
243 | v /= 62; | |
244 | XXXXXX[5] = letters[v % 62]; | |
245 | ||
246 | fd = tryfunc (tmpl, args); | |
247 | if (fd >= 0) | |
248 | { | |
249 | __set_errno (save_errno); | |
250 | return fd; | |
251 | } | |
252 | else if (errno != EEXIST) | |
253 | return -1; | |
254 | } | |
255 | ||
256 | /* We got out of the loop because we ran out of combinations to try. */ | |
257 | __set_errno (EEXIST); | |
258 | return -1; | |
259 | } | |
260 | ||
261 | static int | |
262 | try_file (char *tmpl, void *flags) | |
263 | { | |
264 | int *openflags = flags; | |
265 | return __open (tmpl, | |
266 | (*openflags & ~O_ACCMODE) | |
267 | | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); | |
268 | } | |
269 | ||
270 | static int | |
271 | try_dir (char *tmpl, void *flags _GL_UNUSED) | |
272 | { | |
273 | return __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR); | |
274 | } | |
275 | ||
276 | static int | |
277 | try_nocreate (char *tmpl, void *flags _GL_UNUSED) | |
278 | { | |
279 | struct_stat64 st; | |
280 | ||
7a6dbc2f | 281 | if (__lxstat64 (_STAT_VER, tmpl, &st) == 0 || errno == EOVERFLOW) |
2d8adcbd MM |
282 | __set_errno (EEXIST); |
283 | return errno == ENOENT ? 0 : -1; | |
284 | } | |
285 | ||
286 | /* Generate a temporary file name based on TMPL. TMPL must match the | |
287 | rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix). | |
288 | The name constructed does not exist at the time of the call to | |
289 | __gen_tempname. TMPL is overwritten with the result. | |
290 | ||
291 | KIND may be one of: | |
292 | __GT_NOCREATE: simply verify that the name does not exist | |
293 | at the time of the call. | |
294 | __GT_FILE: create the file using open(O_CREAT|O_EXCL) | |
295 | and return a read-write fd. The file is mode 0600. | |
296 | __GT_DIR: create a directory, which will be mode 0700. | |
297 | ||
298 | We use a clever algorithm to get hard-to-predict names. */ | |
299 | int | |
300 | __gen_tempname (char *tmpl, int suffixlen, int flags, int kind) | |
301 | { | |
302 | int (*tryfunc) (char *, void *); | |
303 | ||
304 | switch (kind) | |
305 | { | |
306 | case __GT_FILE: | |
307 | tryfunc = try_file; | |
308 | break; | |
309 | ||
310 | case __GT_DIR: | |
311 | tryfunc = try_dir; | |
312 | break; | |
313 | ||
314 | case __GT_NOCREATE: | |
315 | tryfunc = try_nocreate; | |
316 | break; | |
317 | ||
318 | default: | |
319 | assert (! "invalid KIND in __gen_tempname"); | |
320 | abort (); | |
321 | } | |
322 | return __try_tempname (tmpl, suffixlen, &flags, tryfunc); | |
323 | } |