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 Free Software Foundation, Inc. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License along 17 with this program; if not, write to the Free Software Foundation, 18 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ 19 20 #if HAVE_CONFIG_H 21 # include <config.h> 22 #endif 23 24 #include <sys/types.h> 25 #include <assert.h> 26 27 #include <errno.h> 28 #ifndef __set_errno 29 # define __set_errno(Val) errno = (Val) 30 #endif 31 32 #include <stdio.h> 33 #ifndef P_tmpdir 34 # define P_tmpdir "/tmp" 35 #endif 36 #ifndef TMP_MAX 37 # define TMP_MAX 238328 38 #endif 39 #ifndef __GT_FILE 40 # define __GT_FILE 0 41 # define __GT_BIGFILE 1 42 # define __GT_DIR 2 43 # define __GT_NOCREATE 3 44 #endif 45 46 #include <stddef.h> 47 #include <stdlib.h> 48 #include <string.h> 49 50 #if HAVE_FCNTL_H || _LIBC 51 # include <fcntl.h> 52 #endif 53 54 #if HAVE_SYS_TIME_H || _LIBC 55 # include <sys/time.h> 56 #endif 57 58 #if HAVE_STDINT_H || _LIBC 59 # include <stdint.h> 60 #endif 61 #if HAVE_INTTYPES_H 62 # include <inttypes.h> 63 #endif 64 65 #if HAVE_UNISTD_H || _LIBC 66 # include <unistd.h> 67 #endif 68 69 #include <sys/stat.h> 70 #if STAT_MACROS_BROKEN 71 # undef S_ISDIR 72 #endif 73 #if !defined S_ISDIR && defined S_IFDIR 74 # define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR) 75 #endif 76 #if !S_IRUSR && S_IREAD 77 # define S_IRUSR S_IREAD 78 #endif 79 #if !S_IRUSR 80 # define S_IRUSR 00400 81 #endif 82 #if !S_IWUSR && S_IWRITE 83 # define S_IWUSR S_IWRITE 84 #endif 85 #if !S_IWUSR 86 # define S_IWUSR 00200 87 #endif 88 #if !S_IXUSR && S_IEXEC 89 # define S_IXUSR S_IEXEC 90 #endif 91 #if !S_IXUSR 92 # define S_IXUSR 00100 93 #endif 94 95 #if _LIBC 96 # define struct_stat64 struct stat64 97 #else 98 # define struct_stat64 struct stat 99 # define __getpid getpid 100 # define __gettimeofday gettimeofday 101 # define __mkdir mkdir 102 # define __open open 103 # define __open64 open 104 # define __lxstat64(version, path, buf) lstat (path, buf) 105 # define __xstat64(version, path, buf) stat (path, buf) 106 #endif 107 108 #if ! (HAVE___SECURE_GETENV || _LIBC) 109 # define __secure_getenv getenv 110 #endif 111 112 #ifdef _LIBC 113 # include <hp-timing.h> 114 # if HP_TIMING_AVAIL 115 # define RANDOM_BITS(Var) \ 116 if (__builtin_expect (value == UINT64_C (0), 0)) \ 117 { \ 118 /* If this is the first time this function is used initialize \ 119 the variable we accumulate the value in to some somewhat \ 120 random value. If we'd not do this programs at startup time \ 121 might have a reduced set of possible names, at least on slow \ 122 machines. */ \ 123 struct timeval tv; \ 124 __gettimeofday (&tv, NULL); \ 125 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \ 126 } \ 127 HP_TIMING_NOW (Var) 128 # endif 129 #endif 130 131 /* Use the widest available unsigned type if uint64_t is not 132 available. The algorithm below extracts a number less than 62**6 133 (approximately 2**35.725) from uint64_t, so ancient hosts where 134 uintmax_t is only 32 bits lose about 3.725 bits of randomness, 135 which is better than not having mkstemp at all. */ 136 #if !defined UINT64_MAX && !defined uint64_t 137 # define uint64_t uintmax_t 138 #endif 139 140 /* Return nonzero if DIR is an existent directory. */ 141 static int 142 direxists (const char *dir) 143 { 144 struct_stat64 buf; 145 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode); 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_stat64 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 fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 300 break; 301 302 case __GT_BIGFILE: 303 fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 304 break; 305 306 case __GT_DIR: 307 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR); 308 break; 309 310 case __GT_NOCREATE: 311 /* This case is backward from the other three. __gen_tempname 312 succeeds if __xstat fails because the name does not exist. 313 Note the continue to bypass the common logic at the bottom 314 of the loop. */ 315 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0) 316 { 317 if (errno == ENOENT) 318 { 319 __set_errno (save_errno); 320 return 0; 321 } 322 else 323 /* Give up now. */ 324 return -1; 325 } 326 continue; 327 328 default: 329 assert (! "invalid KIND in __gen_tempname"); 330 } 331 332 if (fd >= 0) 333 { 334 __set_errno (save_errno); 335 return fd; 336 } 337 else if (errno != EEXIST) 338 return -1; 339 } 340 341 /* We got out of the loop because we ran out of combinations to try. */ 342 __set_errno (EEXIST); 343 return -1; 344 } 345