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 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 19 20 #ifdef 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 #include <fcntl.h> 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 #if HAVE_INTTYPES_H 60 # include <inttypes.h> 61 #endif 62 63 #if HAVE_UNISTD_H || _LIBC 64 # include <unistd.h> 65 #endif 66 67 #include <sys/stat.h> 68 69 #if _LIBC 70 # define struct_stat64 struct stat64 71 #else 72 # include "stat-macros.h" 73 # define struct_stat64 struct stat 74 # define __getpid getpid 75 # define __gettimeofday gettimeofday 76 # define __mkdir mkdir 77 # define __open open 78 # define __open64 open 79 # define __lxstat64(version, file, buf) lstat (file, buf) 80 # define __xstat64(version, file, buf) stat (file, buf) 81 #endif 82 83 #if ! (HAVE___SECURE_GETENV || _LIBC) 84 # define __secure_getenv getenv 85 #endif 86 87 #ifdef _LIBC 88 # include <hp-timing.h> 89 # if HP_TIMING_AVAIL 90 # define RANDOM_BITS(Var) \ 91 if (__builtin_expect (value == UINT64_C (0), 0)) \ 92 { \ 93 /* If this is the first time this function is used initialize \ 94 the variable we accumulate the value in to some somewhat \ 95 random value. If we'd not do this programs at startup time \ 96 might have a reduced set of possible names, at least on slow \ 97 machines. */ \ 98 struct timeval tv; \ 99 __gettimeofday (&tv, NULL); \ 100 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \ 101 } \ 102 HP_TIMING_NOW (Var) 103 # endif 104 #endif 105 106 /* Use the widest available unsigned type if uint64_t is not 107 available. The algorithm below extracts a number less than 62**6 108 (approximately 2**35.725) from uint64_t, so ancient hosts where 109 uintmax_t is only 32 bits lose about 3.725 bits of randomness, 110 which is better than not having mkstemp at all. */ 111 #if !defined UINT64_MAX && !defined uint64_t 112 # define uint64_t uintmax_t 113 #endif 114 115 /* Return nonzero if DIR is an existent directory. */ 116 static int 117 direxists (const char *dir) 118 { 119 struct_stat64 buf; 120 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode); 121 } 122 123 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is 124 non-null and exists, uses it; otherwise uses the first of $TMPDIR, 125 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable 126 for use with mk[s]temp. Will fail (-1) if DIR is non-null and 127 doesn't exist, none of the searched dirs exists, or there's not 128 enough space in TMPL. */ 129 int 130 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx, 131 int try_tmpdir) 132 { 133 const char *d; 134 size_t dlen, plen; 135 136 if (!pfx || !pfx[0]) 137 { 138 pfx = "file"; 139 plen = 4; 140 } 141 else 142 { 143 plen = strlen (pfx); 144 if (plen > 5) 145 plen = 5; 146 } 147 148 if (try_tmpdir) 149 { 150 d = __secure_getenv ("TMPDIR"); 151 if (d != NULL && direxists (d)) 152 dir = d; 153 else if (dir != NULL && direxists (dir)) 154 /* nothing */ ; 155 else 156 dir = NULL; 157 } 158 if (dir == NULL) 159 { 160 if (direxists (P_tmpdir)) 161 dir = P_tmpdir; 162 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp")) 163 dir = "/tmp"; 164 else 165 { 166 __set_errno (ENOENT); 167 return -1; 168 } 169 } 170 171 dlen = strlen (dir); 172 while (dlen > 1 && dir[dlen - 1] == '/') 173 dlen--; /* remove trailing slashes */ 174 175 /* check we have room for "${dir}/${pfx}XXXXXX\0" */ 176 if (tmpl_len < dlen + 1 + plen + 6 + 1) 177 { 178 __set_errno (EINVAL); 179 return -1; 180 } 181 182 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx); 183 return 0; 184 } 185 186 /* These are the characters used in temporary file names. */ 187 static const char letters[] = 188 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; 189 190 /* Generate a temporary file name based on TMPL. TMPL must match the 191 rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed 192 does not exist at the time of the call to __gen_tempname. TMPL is 193 overwritten with the result. 194 195 KIND may be one of: 196 __GT_NOCREATE: simply verify that the name does not exist 197 at the time of the call. 198 __GT_FILE: create the file using open(O_CREAT|O_EXCL) 199 and return a read-write fd. The file is mode 0600. 200 __GT_BIGFILE: same as __GT_FILE but use open64(). 201 __GT_DIR: create a directory, which will be mode 0700. 202 203 We use a clever algorithm to get hard-to-predict names. */ 204 int 205 __gen_tempname (char *tmpl, int kind) 206 { 207 int len; 208 char *XXXXXX; 209 static uint64_t value; 210 uint64_t random_time_bits; 211 unsigned int count; 212 int fd = -1; 213 int save_errno = errno; 214 struct_stat64 st; 215 216 /* A lower bound on the number of temporary files to attempt to 217 generate. The maximum total number of temporary file names that 218 can exist for a given template is 62**6. It should never be 219 necessary to try all these combinations. Instead if a reasonable 220 number of names is tried (we define reasonable as 62**3) fail to 221 give the system administrator the chance to remove the problems. */ 222 unsigned int attempts_min = 62 * 62 * 62; 223 224 /* The number of times to attempt to generate a temporary file. To 225 conform to POSIX, this must be no smaller than TMP_MAX. */ 226 unsigned int attempts = attempts_min < TMP_MAX ? TMP_MAX : attempts_min; 227 228 len = strlen (tmpl); 229 if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX")) 230 { 231 __set_errno (EINVAL); 232 return -1; 233 } 234 235 /* This is where the Xs start. */ 236 XXXXXX = &tmpl[len - 6]; 237 238 /* Get some more or less random data. */ 239 #ifdef RANDOM_BITS 240 RANDOM_BITS (random_time_bits); 241 #else 242 # if HAVE_GETTIMEOFDAY || _LIBC 243 { 244 struct timeval tv; 245 __gettimeofday (&tv, NULL); 246 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; 247 } 248 # else 249 random_time_bits = time (NULL); 250 # endif 251 #endif 252 value += random_time_bits ^ __getpid (); 253 254 for (count = 0; count < attempts; value += 7777, ++count) 255 { 256 uint64_t v = value; 257 258 /* Fill in the random bits. */ 259 XXXXXX[0] = letters[v % 62]; 260 v /= 62; 261 XXXXXX[1] = letters[v % 62]; 262 v /= 62; 263 XXXXXX[2] = letters[v % 62]; 264 v /= 62; 265 XXXXXX[3] = letters[v % 62]; 266 v /= 62; 267 XXXXXX[4] = letters[v % 62]; 268 v /= 62; 269 XXXXXX[5] = letters[v % 62]; 270 271 switch (kind) 272 { 273 case __GT_FILE: 274 fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 275 break; 276 277 case __GT_BIGFILE: 278 fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 279 break; 280 281 case __GT_DIR: 282 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR); 283 break; 284 285 case __GT_NOCREATE: 286 /* This case is backward from the other three. __gen_tempname 287 succeeds if __xstat fails because the name does not exist. 288 Note the continue to bypass the common logic at the bottom 289 of the loop. */ 290 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0) 291 { 292 if (errno == ENOENT) 293 { 294 __set_errno (save_errno); 295 return 0; 296 } 297 else 298 /* Give up now. */ 299 return -1; 300 } 301 continue; 302 303 default: 304 assert (! "invalid KIND in __gen_tempname"); 305 } 306 307 if (fd >= 0) 308 { 309 __set_errno (save_errno); 310 return fd; 311 } 312 else if (errno != EEXIST) 313 return -1; 314 } 315 316 /* We got out of the loop because we ran out of combinations to try. */ 317 __set_errno (EEXIST); 318 return -1; 319 } 320