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posix: Sync tempname with gnulib [BZ #26648]
It syncs with gnulib commit b1268f22f443e8e4b9e. The try_tempname_len now uses getrandom on each iteration to get entropy and only uses the clock plus ASLR as source of entropy if getrandom fails. Checked on x86_64-linux-gnu and i686-linux-gnu.
This commit is contained in:
Adhemerval Zanella
parent
42dda89dcb
commit
4dddd7e9cb
@ -16,7 +16,7 @@
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<https://www.gnu.org/licenses/>. */
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#if !_LIBC
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# include <config.h>
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# include <libc-config.h>
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# include "tempname.h"
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#endif
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@ -24,9 +24,6 @@
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#include <assert.h>
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#include <errno.h>
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#ifndef __set_errno
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# define __set_errno(Val) errno = (Val)
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#endif
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#include <stdio.h>
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#ifndef P_tmpdir
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@ -50,11 +47,11 @@
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#include <string.h>
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#include <fcntl.h>
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#include <time.h>
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#include <stdalign.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <sys/random.h>
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#include <sys/stat.h>
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#include <time.h>
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#if _LIBC
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# define struct_stat64 struct stat64
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@ -62,32 +59,38 @@
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#else
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# define struct_stat64 struct stat
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# define __gen_tempname gen_tempname
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# define __getpid getpid
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# define __mkdir mkdir
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# define __open open
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# define __secure_getenv secure_getenv
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# define __lstat64(file, buf) lstat (file, buf)
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# define __stat64(file, buf) stat (file, buf)
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# define __getrandom getrandom
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# define __clock_gettime64 clock_gettime
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# define __timespec64 timespec
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#endif
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#ifdef _LIBC
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# include <random-bits.h>
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# define RANDOM_BITS(Var) ((Var) = random_bits ())
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# else
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# define RANDOM_BITS(Var) \
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{ \
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struct timespec ts; \
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clock_gettime (CLOCK_REALTIME, &ts); \
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(Var) = ((uint64_t) tv.tv_nsec << 16) ^ tv.tv_sec; \
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/* Use getrandom if it works, falling back on a 64-bit linear
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congruential generator that starts with Var's value
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mixed in with a clock's low-order bits if available. */
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typedef uint_fast64_t random_value;
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#define RANDOM_VALUE_MAX UINT_FAST64_MAX
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#define BASE_62_DIGITS 10 /* 62**10 < UINT_FAST64_MAX */
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#define BASE_62_POWER (62LL * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62)
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static random_value
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random_bits (random_value var)
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{
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random_value r;
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/* Without GRND_NONBLOCK it can be blocked for minutes on some systems. */
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if (__getrandom (&r, sizeof r, GRND_NONBLOCK) == sizeof r)
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return r;
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#if _LIBC || (defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME)
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/* Add entropy if getrandom did not work. */
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struct __timespec64 tv;
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__clock_gettime64 (CLOCK_MONOTONIC, &tv);
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var ^= tv.tv_nsec;
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#endif
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return 2862933555777941757 * var + 3037000493;
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}
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#endif
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/* Use the widest available unsigned type if uint64_t is not
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available. The algorithm below extracts a number less than 62**6
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(approximately 2**35.725) from uint64_t, so ancient hosts where
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uintmax_t is only 32 bits lose about 3.725 bits of randomness,
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which is better than not having mkstemp at all. */
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#if !defined UINT64_MAX && !defined uint64_t
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# define uint64_t uintmax_t
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#endif
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#if _LIBC
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/* Return nonzero if DIR is an existent directory. */
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@ -162,14 +165,45 @@ __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
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}
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#endif /* _LIBC */
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#if _LIBC
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static int try_tempname_len (char *, int, void *, int (*) (char *, void *),
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size_t);
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#endif
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static int
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try_file (char *tmpl, void *flags)
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{
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int *openflags = flags;
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return __open (tmpl,
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(*openflags & ~O_ACCMODE)
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| O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
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}
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static int
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try_dir (char *tmpl, void *flags _GL_UNUSED)
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{
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return __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
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}
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static int
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try_nocreate (char *tmpl, void *flags _GL_UNUSED)
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{
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struct_stat64 st;
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if (__lstat64 (tmpl, &st) == 0 || errno == EOVERFLOW)
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__set_errno (EEXIST);
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return errno == ENOENT ? 0 : -1;
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}
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/* These are the characters used in temporary file names. */
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static const char letters[] =
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"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
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/* Generate a temporary file name based on TMPL. TMPL must match the
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rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).
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rules for mk[s]temp (i.e., end in at least X_SUFFIX_LEN "X"s,
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possibly with a suffix).
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The name constructed does not exist at the time of the call to
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__gen_tempname. TMPL is overwritten with the result.
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this function. TMPL is overwritten with the result.
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KIND may be one of:
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__GT_NOCREATE: simply verify that the name does not exist
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@ -179,22 +213,43 @@ static const char letters[] =
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__GT_DIR: create a directory, which will be mode 0700.
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We use a clever algorithm to get hard-to-predict names. */
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#ifdef _LIBC
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static
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#endif
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int
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__gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
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gen_tempname_len (char *tmpl, int suffixlen, int flags, int kind,
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size_t x_suffix_len)
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{
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int len;
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static int (*const tryfunc[]) (char *, void *) =
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{
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[__GT_FILE] = try_file,
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[__GT_DIR] = try_dir,
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[__GT_NOCREATE] = try_nocreate
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};
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return try_tempname_len (tmpl, suffixlen, &flags, tryfunc[kind],
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x_suffix_len);
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}
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#ifdef _LIBC
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static
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#endif
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int
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try_tempname_len (char *tmpl, int suffixlen, void *args,
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int (*tryfunc) (char *, void *), size_t x_suffix_len)
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{
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size_t len;
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char *XXXXXX;
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unsigned int count;
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int fd = -1;
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int save_errno = errno;
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struct_stat64 st;
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/* A lower bound on the number of temporary files to attempt to
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generate. The maximum total number of temporary file names that
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can exist for a given template is 62**6. It should never be
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necessary to try all of these combinations. Instead if a reasonable
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number of names is tried (we define reasonable as 62**3) fail to
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give the system administrator the chance to remove the problems. */
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give the system administrator the chance to remove the problems.
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This value requires that X_SUFFIX_LEN be at least 3. */
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#define ATTEMPTS_MIN (62 * 62 * 62)
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/* The number of times to attempt to generate a temporary file. To
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@ -205,72 +260,50 @@ __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
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unsigned int attempts = ATTEMPTS_MIN;
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#endif
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/* A random variable. The initial value is used only the for fallback path
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on 'random_bits' on 'getrandom' failure. Its initial value tries to use
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some entropy from the ASLR and ignore possible bits from the stack
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alignment. */
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random_value v = ((uintptr_t) &v) / alignof (max_align_t);
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/* How many random base-62 digits can currently be extracted from V. */
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int vdigits = 0;
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/* Least unfair value for V. If V is less than this, V can generate
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BASE_62_DIGITS digits fairly. Otherwise it might be biased. */
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random_value const unfair_min
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= RANDOM_VALUE_MAX - RANDOM_VALUE_MAX % BASE_62_POWER;
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len = strlen (tmpl);
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if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
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if (len < x_suffix_len + suffixlen
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|| strspn (&tmpl[len - x_suffix_len - suffixlen], "X") < x_suffix_len)
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{
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__set_errno (EINVAL);
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return -1;
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}
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/* This is where the Xs start. */
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XXXXXX = &tmpl[len - 6 - suffixlen];
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XXXXXX = &tmpl[len - x_suffix_len - suffixlen];
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uint64_t pid = (uint64_t) __getpid () << 32;
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for (count = 0; count < attempts; ++count)
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{
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uint64_t v;
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/* Get some more or less random data. */
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RANDOM_BITS (v);
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v ^= pid;
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/* Fill in the random bits. */
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XXXXXX[0] = letters[v % 62];
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v /= 62;
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XXXXXX[1] = letters[v % 62];
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v /= 62;
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XXXXXX[2] = letters[v % 62];
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v /= 62;
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XXXXXX[3] = letters[v % 62];
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v /= 62;
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XXXXXX[4] = letters[v % 62];
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v /= 62;
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XXXXXX[5] = letters[v % 62];
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switch (kind)
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for (size_t i = 0; i < x_suffix_len; i++)
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{
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case __GT_FILE:
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fd = __open (tmpl,
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(flags & ~O_ACCMODE)
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| O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
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break;
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case __GT_DIR:
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fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
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break;
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case __GT_NOCREATE:
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/* This case is backward from the other three. __gen_tempname
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succeeds if lstat fails because the name does not exist.
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Note the continue to bypass the common logic at the bottom
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of the loop. */
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if (__lstat64 (tmpl, &st) < 0)
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if (vdigits == 0)
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{
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if (errno == ENOENT)
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{
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__set_errno (save_errno);
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return 0;
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}
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else
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/* Give up now. */
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return -1;
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}
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continue;
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do
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v = random_bits (v);
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while (unfair_min <= v);
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default:
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assert (! "invalid KIND in __gen_tempname");
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abort ();
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vdigits = BASE_62_DIGITS;
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}
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XXXXXX[i] = letters[v % 62];
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v /= 62;
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vdigits--;
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}
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fd = tryfunc (tmpl, args);
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if (fd >= 0)
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{
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__set_errno (save_errno);
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@ -284,3 +317,18 @@ __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
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__set_errno (EEXIST);
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return -1;
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}
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int
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__gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
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{
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return gen_tempname_len (tmpl, suffixlen, flags, kind, 6);
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}
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#if !_LIBC
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int
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try_tempname (char *tmpl, int suffixlen, void *args,
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int (*tryfunc) (char *, void *))
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{
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return try_tempname_len (tmpl, suffixlen, args, tryfunc, 6);
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}
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#endif
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