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