1 /* tempname.c - generate the name of a temporary file. 2 3 Copyright (C) 1991-2003, 2005-2007, 2009-2011 Free Software Foundation, Inc. 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 16 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 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 __gen_tempname gen_tempname 66 # define __getpid getpid 67 # define __gettimeofday gettimeofday 68 # define __mkdir mkdir 69 # define __open open 70 # define __open64 open 71 # define __lxstat64(version, file, buf) lstat (file, buf) 72 # define __xstat64(version, file, buf) stat (file, buf) 73 #endif 74 75 #if ! (HAVE___SECURE_GETENV || _LIBC) 76 # define __secure_getenv getenv 77 #endif 78 79 #ifdef _LIBC 80 # include <hp-timing.h> 81 # if HP_TIMING_AVAIL 82 # define RANDOM_BITS(Var) \ 83 if (__builtin_expect (value == UINT64_C (0), 0)) \ 84 { \ 85 /* If this is the first time this function is used initialize \ 86 the variable we accumulate the value in to some somewhat \ 87 random value. If we'd not do this programs at startup time \ 88 might have a reduced set of possible names, at least on slow \ 89 machines. */ \ 90 struct timeval tv; \ 91 __gettimeofday (&tv, NULL); \ 92 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \ 93 } \ 94 HP_TIMING_NOW (Var) 95 # endif 96 #endif 97 98 /* Use the widest available unsigned type if uint64_t is not 99 available. The algorithm below extracts a number less than 62**6 100 (approximately 2**35.725) from uint64_t, so ancient hosts where 101 uintmax_t is only 32 bits lose about 3.725 bits of randomness, 102 which is better than not having mkstemp at all. */ 103 #if !defined UINT64_MAX && !defined uint64_t 104 # define uint64_t uintmax_t 105 #endif 106 107 #if _LIBC 108 /* Return nonzero if DIR is an existent directory. */ 109 static int 110 direxists (const char *dir) 111 { 112 struct_stat64 buf; 113 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode); 114 } 115 116 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is 117 non-null and exists, uses it; otherwise uses the first of $TMPDIR, 118 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable 119 for use with mk[s]temp. Will fail (-1) if DIR is non-null and 120 doesn't exist, none of the searched dirs exists, or there's not 121 enough space in TMPL. */ 122 int 123 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx, 124 int try_tmpdir) 125 { 126 const char *d; 127 size_t dlen, plen; 128 129 if (!pfx || !pfx[0]) 130 { 131 pfx = "file"; 132 plen = 4; 133 } 134 else 135 { 136 plen = strlen (pfx); 137 if (plen > 5) 138 plen = 5; 139 } 140 141 if (try_tmpdir) 142 { 143 d = __secure_getenv ("TMPDIR"); 144 if (d != NULL && direxists (d)) 145 dir = d; 146 else if (dir != NULL && direxists (dir)) 147 /* nothing */ ; 148 else 149 dir = NULL; 150 } 151 if (dir == NULL) 152 { 153 if (direxists (P_tmpdir)) 154 dir = P_tmpdir; 155 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp")) 156 dir = "/tmp"; 157 else 158 { 159 __set_errno (ENOENT); 160 return -1; 161 } 162 } 163 164 dlen = strlen (dir); 165 while (dlen > 1 && dir[dlen - 1] == '/') 166 dlen--; /* remove trailing slashes */ 167 168 /* check we have room for "${dir}/${pfx}XXXXXX\0" */ 169 if (tmpl_len < dlen + 1 + plen + 6 + 1) 170 { 171 __set_errno (EINVAL); 172 return -1; 173 } 174 175 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx); 176 return 0; 177 } 178 #endif /* _LIBC */ 179 180 /* These are the characters used in temporary file names. */ 181 static const char letters[] = 182 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; 183 184 /* Generate a temporary file name based on TMPL. TMPL must match the 185 rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix). 186 The name constructed does not exist at the time of the call to 187 __gen_tempname. TMPL is overwritten with the result. 188 189 KIND may be one of: 190 __GT_NOCREATE: simply verify that the name does not exist 191 at the time of the call. 192 __GT_FILE: create the file using open(O_CREAT|O_EXCL) 193 and return a read-write fd. The file is mode 0600. 194 __GT_DIR: create a directory, which will be mode 0700. 195 196 We use a clever algorithm to get hard-to-predict names. */ 197 int 198 __gen_tempname (char *tmpl, int suffixlen, int flags, int kind) 199 { 200 int len; 201 char *XXXXXX; 202 static uint64_t value; 203 uint64_t random_time_bits; 204 unsigned int count; 205 int fd = -1; 206 int save_errno = errno; 207 struct_stat64 st; 208 209 /* A lower bound on the number of temporary files to attempt to 210 generate. The maximum total number of temporary file names that 211 can exist for a given template is 62**6. It should never be 212 necessary to try all these combinations. Instead if a reasonable 213 number of names is tried (we define reasonable as 62**3) fail to 214 give the system administrator the chance to remove the problems. */ 215 #define ATTEMPTS_MIN (62 * 62 * 62) 216 217 /* The number of times to attempt to generate a temporary file. To 218 conform to POSIX, this must be no smaller than TMP_MAX. */ 219 #if ATTEMPTS_MIN < TMP_MAX 220 unsigned int attempts = TMP_MAX; 221 #else 222 unsigned int attempts = ATTEMPTS_MIN; 223 #endif 224 225 len = strlen (tmpl); 226 if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6)) 227 { 228 __set_errno (EINVAL); 229 return -1; 230 } 231 232 /* This is where the Xs start. */ 233 XXXXXX = &tmpl[len - 6 - suffixlen]; 234 235 /* Get some more or less random data. */ 236 #ifdef RANDOM_BITS 237 RANDOM_BITS (random_time_bits); 238 #else 239 { 240 struct timeval tv; 241 __gettimeofday (&tv, NULL); 242 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; 243 } 244 #endif 245 value += random_time_bits ^ __getpid (); 246 247 for (count = 0; count < attempts; value += 7777, ++count) 248 { 249 uint64_t v = value; 250 251 /* Fill in the random bits. */ 252 XXXXXX[0] = letters[v % 62]; 253 v /= 62; 254 XXXXXX[1] = letters[v % 62]; 255 v /= 62; 256 XXXXXX[2] = letters[v % 62]; 257 v /= 62; 258 XXXXXX[3] = letters[v % 62]; 259 v /= 62; 260 XXXXXX[4] = letters[v % 62]; 261 v /= 62; 262 XXXXXX[5] = letters[v % 62]; 263 264 switch (kind) 265 { 266 case __GT_FILE: 267 fd = __open (tmpl, 268 (flags & ~O_ACCMODE) 269 | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 270 break; 271 272 case __GT_DIR: 273 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR); 274 break; 275 276 case __GT_NOCREATE: 277 /* This case is backward from the other three. __gen_tempname 278 succeeds if __xstat fails because the name does not exist. 279 Note the continue to bypass the common logic at the bottom 280 of the loop. */ 281 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0) 282 { 283 if (errno == ENOENT) 284 { 285 __set_errno (save_errno); 286 return 0; 287 } 288 else 289 /* Give up now. */ 290 return -1; 291 } 292 continue; 293 294 default: 295 assert (! "invalid KIND in __gen_tempname"); 296 abort (); 297 } 298 299 if (fd >= 0) 300 { 301 __set_errno (save_errno); 302 return fd; 303 } 304 else if (errno != EEXIST) 305 return -1; 306 } 307 308 /* We got out of the loop because we ran out of combinations to try. */ 309 __set_errno (EEXIST); 310 return -1; 311 } 312