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wget/lib/tempname.c

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/* tempname.c - generate the name of a temporary file.
Copyright (C) 1991-2003, 2005-2007, 2009-2019 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Extracted from glibc sysdeps/posix/tempname.c. See also tmpdir.c. */
#if !_LIBC
# include <config.h>
# include "tempname.h"
#endif
#include <sys/types.h>
#include <assert.h>
#include <errno.h>
#ifndef __set_errno
# define __set_errno(Val) errno = (Val)
#endif
#include <stdio.h>
#ifndef P_tmpdir
# define P_tmpdir "/tmp"
#endif
#ifndef TMP_MAX
# define TMP_MAX 238328
#endif
#ifndef __GT_FILE
# define __GT_FILE 0
# define __GT_DIR 1
# define __GT_NOCREATE 2
#endif
#if !_LIBC && (GT_FILE != __GT_FILE || GT_DIR != __GT_DIR \
|| GT_NOCREATE != __GT_NOCREATE)
# error report this to bug-gnulib@gnu.org
#endif
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/time.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/stat.h>
#if _LIBC
# define struct_stat64 struct stat64
#else
# define struct_stat64 struct stat
# define __try_tempname try_tempname
# define __gen_tempname gen_tempname
# define __getpid getpid
# define __gettimeofday gettimeofday
# define __mkdir mkdir
# define __open open
# define __lxstat64(version, file, buf) lstat (file, buf)
#endif
#ifdef _LIBC
# include <hp-timing.h>
# if HP_TIMING_AVAIL
# define RANDOM_BITS(Var) \
if (__builtin_expect (value == UINT64_C (0), 0)) \
{ \
/* If this is the first time this function is used initialize \
the variable we accumulate the value in to some somewhat \
random value. If we'd not do this programs at startup time \
might have a reduced set of possible names, at least on slow \
machines. */ \
struct timeval tv; \
__gettimeofday (&tv, NULL); \
value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
} \
HP_TIMING_NOW (Var)
# endif
#endif
/* Use the widest available unsigned type if uint64_t is not
available. The algorithm below extracts a number less than 62**6
(approximately 2**35.725) from uint64_t, so ancient hosts where
uintmax_t is only 32 bits lose about 3.725 bits of randomness,
which is better than not having mkstemp at all. */
#if !defined UINT64_MAX && !defined uint64_t
# define uint64_t uintmax_t
#endif
#if _LIBC
/* Return nonzero if DIR is an existent directory. */
static int
direxists (const char *dir)
{
struct_stat64 buf;
return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
}
/* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
non-null and exists, uses it; otherwise uses the first of $TMPDIR,
P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
for use with mk[s]temp. Will fail (-1) if DIR is non-null and
doesn't exist, none of the searched dirs exists, or there's not
enough space in TMPL. */
int
__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
int try_tmpdir)
{
const char *d;
size_t dlen, plen;
if (!pfx || !pfx[0])
{
pfx = "file";
plen = 4;
}
else
{
plen = strlen (pfx);
if (plen > 5)
plen = 5;
}
if (try_tmpdir)
{
d = __secure_getenv ("TMPDIR");
if (d != NULL && direxists (d))
dir = d;
else if (dir != NULL && direxists (dir))
/* nothing */ ;
else
dir = NULL;
}
if (dir == NULL)
{
if (direxists (P_tmpdir))
dir = P_tmpdir;
else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
dir = "/tmp";
else
{
__set_errno (ENOENT);
return -1;
}
}
dlen = strlen (dir);
while (dlen > 1 && dir[dlen - 1] == '/')
dlen--; /* remove trailing slashes */
/* check we have room for "${dir}/${pfx}XXXXXX\0" */
if (tmpl_len < dlen + 1 + plen + 6 + 1)
{
__set_errno (EINVAL);
return -1;
}
sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
return 0;
}
#endif /* _LIBC */
/* These are the characters used in temporary file names. */
static const char letters[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
int
__try_tempname (char *tmpl, int suffixlen, void *args,
int (*tryfunc) (char *, void *))
{
int len;
char *XXXXXX;
static uint64_t value;
uint64_t random_time_bits;
unsigned int count;
int fd = -1;
int save_errno = errno;
/* A lower bound on the number of temporary files to attempt to
generate. The maximum total number of temporary file names that
can exist for a given template is 62**6. It should never be
necessary to try all of these combinations. Instead if a reasonable
number of names is tried (we define reasonable as 62**3) fail to
give the system administrator the chance to remove the problems. */
#define ATTEMPTS_MIN (62 * 62 * 62)
/* The number of times to attempt to generate a temporary file. To
conform to POSIX, this must be no smaller than TMP_MAX. */
#if ATTEMPTS_MIN < TMP_MAX
unsigned int attempts = TMP_MAX;
#else
unsigned int attempts = ATTEMPTS_MIN;
#endif
len = strlen (tmpl);
if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
{
__set_errno (EINVAL);
return -1;
}
/* This is where the Xs start. */
XXXXXX = &tmpl[len - 6 - suffixlen];
/* Get some more or less random data. */
#ifdef RANDOM_BITS
RANDOM_BITS (random_time_bits);
#else
{
struct timeval tv;
__gettimeofday (&tv, NULL);
random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
}
#endif
value += random_time_bits ^ __getpid ();
for (count = 0; count < attempts; value += 7777, ++count)
{
uint64_t v = value;
/* Fill in the random bits. */
XXXXXX[0] = letters[v % 62];
v /= 62;
XXXXXX[1] = letters[v % 62];
v /= 62;
XXXXXX[2] = letters[v % 62];
v /= 62;
XXXXXX[3] = letters[v % 62];
v /= 62;
XXXXXX[4] = letters[v % 62];
v /= 62;
XXXXXX[5] = letters[v % 62];
fd = tryfunc (tmpl, args);
if (fd >= 0)
{
__set_errno (save_errno);
return fd;
}
else if (errno != EEXIST)
return -1;
}
/* We got out of the loop because we ran out of combinations to try. */
__set_errno (EEXIST);
return -1;
}
static int
try_file (char *tmpl, void *flags)
{
int *openflags = flags;
return __open (tmpl,
(*openflags & ~O_ACCMODE)
| O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
}
static int
try_dir (char *tmpl, void *flags _GL_UNUSED)
{
return __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
}
static int
try_nocreate (char *tmpl, void *flags _GL_UNUSED)
{
struct_stat64 st;
if (__lxstat64 (_STAT_VER, tmpl, &st) == 0 || errno == EOVERFLOW)
__set_errno (EEXIST);
return errno == ENOENT ? 0 : -1;
}
/* Generate a temporary file name based on TMPL. TMPL must match the
rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).
The name constructed does not exist at the time of the call to
__gen_tempname. TMPL is overwritten with the result.
KIND may be one of:
__GT_NOCREATE: simply verify that the name does not exist
at the time of the call.
__GT_FILE: create the file using open(O_CREAT|O_EXCL)
and return a read-write fd. The file is mode 0600.
__GT_DIR: create a directory, which will be mode 0700.
We use a clever algorithm to get hard-to-predict names. */
int
__gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
{
int (*tryfunc) (char *, void *);
switch (kind)
{
case __GT_FILE:
tryfunc = try_file;
break;
case __GT_DIR:
tryfunc = try_dir;
break;
case __GT_NOCREATE:
tryfunc = try_nocreate;
break;
default:
assert (! "invalid KIND in __gen_tempname");
abort ();
}
return __try_tempname (tmpl, suffixlen, &flags, tryfunc);
}
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