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util: add support for getrandom()

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Add support for the Linux getrandom() system call, which is available
in glibc since 2.25.
This commit is contained in:
Miroslav Lichvar
2017-06-15 17:35:33 +02:00
parent db93180ce1
commit c5735ebfe9
3 changed files with 42 additions and 0 deletions
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33
util.c
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@@ -1195,11 +1195,44 @@ UTI_GetRandomBytesUrandom(void *buf, unsigned int len)
/* ================================================== */
#ifdef HAVE_GETRANDOM
static void
get_random_bytes_getrandom(char *buf, unsigned int len)
{
static char rand_buf[256];
static unsigned int available = 0, disabled = 0;
unsigned int i;
for (i = 0; i < len; i++) {
if (!available) {
if (disabled)
break;
if (getrandom(rand_buf, sizeof (rand_buf), 0) != sizeof (rand_buf)) {
disabled = 1;
break;
}
available = sizeof (rand_buf);
}
buf[i] = rand_buf[--available];
}
if (i < len)
UTI_GetRandomBytesUrandom(buf, len);
}
#endif
/* ================================================== */
void
UTI_GetRandomBytes(void *buf, unsigned int len)
{
#ifdef HAVE_ARC4RANDOM
arc4random_buf(buf, len);
#elif defined(HAVE_GETRANDOM)
get_random_bytes_getrandom(buf, len);
#else
UTI_GetRandomBytesUrandom(buf, len);
#endif