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bsps: Use a state in default getentropy()

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Use the boot time to initialize the state.  Use the state, the current
CPU counter and a very simple pseudo random number generator for
getentropy(). At least, this enables to pass the test "GETENTROPY 1" on
ERC32.

Update #3239.
This commit is contained in:
Sebastian Huber
2017-11-17 09:43:17 +01:00
parent 2e2a41ecd9
commit 3d374d90f8
1 changed files with 36 additions and 21 deletions
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57
c/src/lib/libbsp/shared/getentropy-cpucounter.c
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@@ -20,35 +20,50 @@
* you need for example a strong crypto.
*/
#include <sys/param.h>
#include <unistd.h>
#include <string.h>
#include <rtems/sysinit.h>
#include <rtems/bsd.h>
#include <rtems/counter.h>
#include <rtems/sysinit.h>
static uint32_t state;
int getentropy(void *ptr, size_t n)
{
uint8_t *dest = ptr;
uint8_t *dest = ptr;
while (n > 0) {
rtems_counter_ticks ticks;
state ^= rtems_counter_read();
state *= 25169206;
state += 1679610226;
ticks = rtems_counter_read();
while (n > 0) {
size_t m;
if (n >= sizeof(ticks)) {
memcpy(dest, &ticks, sizeof(ticks));
n -= sizeof(ticks);
dest += sizeof(ticks);
} else {
/*
* Fill the remaining bytes with only the least
* significant byte of the time. That is the byte with
* the most changes.
*/
*dest = ticks & 0xFF;
--n;
++dest;
}
}
m = MIN(n, sizeof(state));
memcpy(dest, &state, m);
n -= m;
dest += m;
state *= 85236167;
state += 30557471;
}
return 0;
return 0;
}
static void getentropy_init(void)
{
struct bintime bt;
rtems_bsd_bintime(&bt);
state = (uint32_t) bt.frac;
state ^= (uint32_t) (bt.frac >> 32);
state ^= (uint32_t) bt.sec;
state ^= (uint32_t) (bt.sec >> 32);
}
RTEMS_SYSINIT_ITEM(
getentropy_init,
RTEMS_SYSINIT_DEVICE_DRIVERS,
RTEMS_SYSINIT_ORDER_LAST
);