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, 2006, 2007 Free Software Foundation, 5 Inc. 6 7 This program is free software: you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or 10 (at your option) any later version. 11 12 This program is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20/* Extracted from glibc sysdeps/posix/tempname.c. See also tmpdir.c. */ 21 22#if !_LIBC 23# include <config.h> 24# include "tempname.h" 25#endif 26 27#include <sys/types.h> 28#include <assert.h> 29 30#include <errno.h> 31#ifndef __set_errno 32# define __set_errno(Val) errno = (Val) 33#endif 34 35#include <stdio.h> 36#ifndef P_tmpdir 37# define P_tmpdir "/tmp" 38#endif 39#ifndef TMP_MAX 40# define TMP_MAX 238328 41#endif 42#ifndef __GT_FILE 43# define __GT_FILE 0 44# define __GT_BIGFILE 1 45# define __GT_DIR 2 46# define __GT_NOCREATE 3 47#endif 48 49#include <stddef.h> 50#include <stdlib.h> 51#include <string.h> 52 53#include <fcntl.h> 54#include <sys/time.h> 55#include <stdint.h> 56#include <unistd.h> 57 58#include <sys/stat.h> 59 60#if _LIBC 61# define struct_stat64 struct stat64 62# define small_open __open 63# define large_open __open64 64#else 65# define struct_stat64 struct stat 66# define small_open open 67# define large_open open 68# define __gen_tempname gen_tempname 69# define __getpid getpid 70# define __gettimeofday gettimeofday 71# define __mkdir mkdir 72# define __lxstat64(version, file, buf) lstat (file, buf) 73# define __xstat64(version, file, buf) stat (file, buf) 74#endif 75 76#if ! (HAVE___SECURE_GETENV || _LIBC) 77# define __secure_getenv getenv 78#endif 79 80#ifdef _LIBC 81# include <hp-timing.h> 82# if HP_TIMING_AVAIL 83# define RANDOM_BITS(Var) \ 84 if (__builtin_expect (value == UINT64_C (0), 0)) \ 85 { \ 86 /* If this is the first time this function is used initialize \ 87 the variable we accumulate the value in to some somewhat \ 88 random value. If we'd not do this programs at startup time \ 89 might have a reduced set of possible names, at least on slow \ 90 machines. */ \ 91 struct timeval tv; \ 92 __gettimeofday (&tv, NULL); \ 93 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \ 94 } \ 95 HP_TIMING_NOW (Var) 96# endif 97#endif 98 99/* Use the widest available unsigned type if uint64_t is not 100 available. The algorithm below extracts a number less than 62**6 101 (approximately 2**35.725) from uint64_t, so ancient hosts where 102 uintmax_t is only 32 bits lose about 3.725 bits of randomness, 103 which is better than not having mkstemp at all. */ 104#if !defined UINT64_MAX && !defined uint64_t 105# define uint64_t uintmax_t 106#endif 107 108#if _LIBC 109/* Return nonzero if DIR is an existent directory. */ 110static int 111direxists (const char *dir) 112{ 113 struct_stat64 buf; 114 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode); 115} 116 117/* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is 118 non-null and exists, uses it; otherwise uses the first of $TMPDIR, 119 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable 120 for use with mk[s]temp. Will fail (-1) if DIR is non-null and 121 doesn't exist, none of the searched dirs exists, or there's not 122 enough space in TMPL. */ 123int 124__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx, 125 int try_tmpdir) 126{ 127 const char *d; 128 size_t dlen, plen; 129 130 if (!pfx || !pfx[0]) 131 { 132 pfx = "file"; 133 plen = 4; 134 } 135 else 136 { 137 plen = strlen (pfx); 138 if (plen > 5) 139 plen = 5; 140 } 141 142 if (try_tmpdir) 143 { 144 d = __secure_getenv ("TMPDIR"); 145 if (d != NULL && direxists (d)) 146 dir = d; 147 else if (dir != NULL && direxists (dir)) 148 /* nothing */ ; 149 else 150 dir = NULL; 151 } 152 if (dir == NULL) 153 { 154 if (direxists (P_tmpdir)) 155 dir = P_tmpdir; 156 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp")) 157 dir = "/tmp"; 158 else 159 { 160 __set_errno (ENOENT); 161 return -1; 162 } 163 } 164 165 dlen = strlen (dir); 166 while (dlen > 1 && dir[dlen - 1] == '/') 167 dlen--; /* remove trailing slashes */ 168 169 /* check we have room for "${dir}/${pfx}XXXXXX\0" */ 170 if (tmpl_len < dlen + 1 + plen + 6 + 1) 171 { 172 __set_errno (EINVAL); 173 return -1; 174 } 175 176 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx); 177 return 0; 178} 179#endif /* _LIBC */ 180 181/* These are the characters used in temporary file names. */ 182static const char letters[] = 183"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; 184 185/* Generate a temporary file name based on TMPL. TMPL must match the 186 rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed 187 does not exist at the time of the call to __gen_tempname. TMPL is 188 overwritten with the result. 189 190 KIND may be one of: 191 __GT_NOCREATE: simply verify that the name does not exist 192 at the time of the call. 193 __GT_FILE: create the file using open(O_CREAT|O_EXCL) 194 and return a read-write fd. The file is mode 0600. 195 __GT_BIGFILE: same as __GT_FILE but use open64(). 196 __GT_DIR: create a directory, which will be mode 0700. 197 198 We use a clever algorithm to get hard-to-predict names. */ 199int 200__gen_tempname (char *tmpl, int kind) 201{ 202 int len; 203 char *XXXXXX; 204 static uint64_t value; 205 uint64_t random_time_bits; 206 unsigned int count; 207 int fd = -1; 208 int save_errno = errno; 209 struct_stat64 st; 210 211 /* A lower bound on the number of temporary files to attempt to 212 generate. The maximum total number of temporary file names that 213 can exist for a given template is 62**6. It should never be 214 necessary to try all these combinations. Instead if a reasonable 215 number of names is tried (we define reasonable as 62**3) fail to 216 give the system administrator the chance to remove the problems. */ 217#define ATTEMPTS_MIN (62 * 62 * 62) 218 219 /* The number of times to attempt to generate a temporary file. To 220 conform to POSIX, this must be no smaller than TMP_MAX. */ 221#if ATTEMPTS_MIN < TMP_MAX 222 unsigned int attempts = TMP_MAX; 223#else 224 unsigned int attempts = ATTEMPTS_MIN; 225#endif 226 227 len = strlen (tmpl); 228 if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX")) 229 { 230 __set_errno (EINVAL); 231 return -1; 232 } 233 234 /* This is where the Xs start. */ 235 XXXXXX = &tmpl[len - 6]; 236 237 /* Get some more or less random data. */ 238#ifdef RANDOM_BITS 239 RANDOM_BITS (random_time_bits); 240#else 241 { 242 struct timeval tv; 243 __gettimeofday (&tv, NULL); 244 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; 245 } 246#endif 247 value += random_time_bits ^ __getpid (); 248 249 for (count = 0; count < attempts; value += 7777, ++count) 250 { 251 uint64_t v = value; 252 253 /* Fill in the random bits. */ 254 XXXXXX[0] = letters[v % 62]; 255 v /= 62; 256 XXXXXX[1] = letters[v % 62]; 257 v /= 62; 258 XXXXXX[2] = letters[v % 62]; 259 v /= 62; 260 XXXXXX[3] = letters[v % 62]; 261 v /= 62; 262 XXXXXX[4] = letters[v % 62]; 263 v /= 62; 264 XXXXXX[5] = letters[v % 62]; 265 266 switch (kind) 267 { 268 case __GT_FILE: 269 fd = small_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 270 break; 271 272 case __GT_BIGFILE: 273 fd = large_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 274 break; 275 276 case __GT_DIR: 277 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR); 278 break; 279 280 case __GT_NOCREATE: 281 /* This case is backward from the other three. __gen_tempname 282 succeeds if __xstat fails because the name does not exist. 283 Note the continue to bypass the common logic at the bottom 284 of the loop. */ 285 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0) 286 { 287 if (errno == ENOENT) 288 { 289 __set_errno (save_errno); 290 return 0; 291 } 292 else 293 /* Give up now. */ 294 return -1; 295 } 296 continue; 297 298 default: 299 assert (! "invalid KIND in __gen_tempname"); 300 } 301 302 if (fd >= 0) 303 { 304 __set_errno (save_errno); 305 return fd; 306 } 307 else if (errno != EEXIST) 308 return -1; 309 } 310 311 /* We got out of the loop because we ran out of combinations to try. */ 312 __set_errno (EEXIST); 313 return -1; 314} 315