For __GT_NOCREATE (mktemp, tempnam, tmpnam) getrandom is also used
on first try, otherwise randomness is obtained using the clock plus
a linear congruential generator.
Also for getrandom GRND_NONBLOCK is used to avoid blocking indefinitely
on some older kernels.
Checked on x86_64-linux-gnu.
---
sysdeps/posix/tempname.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/sysdeps/posix/tempname.c b/sysdeps/posix/tempname.c
index 193d791103..06db694181 100644
--- a/sysdeps/posix/tempname.c
+++ b/sysdeps/posix/tempname.c
@@ -76,10 +76,11 @@ typedef uint_fast64_t random_value;
#define BASE_62_POWER (62LL * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62)
static random_value
-random_bits (random_value var)
+random_bits (random_value var, bool use_getrandom)
{
random_value r;
- if (__getrandom (&r, sizeof r, 0) == sizeof r)
+ /* 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)
/* Add entropy if getrandom is not supported. */
@@ -263,9 +264,10 @@ try_tempname_len (char *tmpl, int suffixlen, void *args,
some entropy from the ASLR and ignore possible bits from the stack
alignment. */
random_value v = ((uintptr_t) &v) / alignof (max_align_t);
+ v = random_bits (v, tryfunc == try_nocreate);
/* How many random base-62 digits can currently be extracted from V. */
- int vdigits = 0;
+ int vdigits = BASE_62_DIGITS;
/* Least unfair value for V. If V is less than this, V can generate
BASE_62_DIGITS digits fairly. Otherwise it might be biased. */
@@ -290,7 +292,7 @@ try_tempname_len (char *tmpl, int suffixlen, void *args,
if (vdigits == 0)
{
do
- v = random_bits (v);
+ v = random_bits (v, true);
while (unfair_min <= v);
vdigits = BASE_62_DIGITS;
--
2.25.1
