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Backport tempname changes from master (bug#57129)

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* lib/tempname.c: Backport from master, which uses current Gnulib.
This commit is contained in:
Paul Eggert 2022-08-17 20:30:26 -07:00
parent a4078fa628
commit 21751f02d3
1 changed files with 19 additions and 3 deletions
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22
lib/tempname.c
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@ -77,6 +77,12 @@ typedef uint_fast64_t random_value;
#define BASE_62_DIGITS 10 /* 62**10 < UINT_FAST64_MAX */
#define BASE_62_POWER (62LL * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62)
#if _LIBC || (defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME)
# define HAS_CLOCK_ENTROPY true
#else
# define HAS_CLOCK_ENTROPY false
#endif
static random_value
random_bits (random_value var, bool use_getrandom)
{
@ -84,7 +90,7 @@ random_bits (random_value var, bool use_getrandom)
/* Without GRND_NONBLOCK it can be blocked for minutes on some systems. */
if (use_getrandom && __getrandom (&r, sizeof r, GRND_NONBLOCK) == sizeof r)
return r;
#if _LIBC || (defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME)
#if HAS_CLOCK_ENTROPY
/* Add entropy if getrandom did not work. */
struct __timespec64 tv;
__clock_gettime64 (CLOCK_MONOTONIC, &tv);
@ -213,7 +219,7 @@ static const char letters[] =
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. */
*/
#ifdef _LIBC
static
#endif
@ -267,13 +273,20 @@ try_tempname_len (char *tmpl, int suffixlen, void *args,
alignment. */
random_value v = ((uintptr_t) &v) / alignof (max_align_t);
#if !HAS_CLOCK_ENTROPY
/* Arrange gen_tempname to return less predictable file names on
systems lacking clock entropy <https://bugs.gnu.org/57129>. */
static random_value prev_v;
v ^= prev_v;
#endif
/* How many random base-62 digits can currently be extracted from V. */
int vdigits = 0;
/* Whether to consume entropy when acquiring random bits. On the
first try it's worth the entropy cost with __GT_NOCREATE, which
is inherently insecure and can use the entropy to make it a bit
less secure. On the (rare) second and later attempts it might
more secure. On the (rare) second and later attempts it might
help against DoS attacks. */
bool use_getrandom = tryfunc == try_nocreate;
@ -318,6 +331,9 @@ try_tempname_len (char *tmpl, int suffixlen, void *args,
if (fd >= 0)
{
__set_errno (save_errno);
#if !HAS_CLOCK_ENTROPY
prev_v = v;
#endif
return fd;
}
else if (errno != EEXIST)