From 3d374d90f8f2814a7ae6549d4c0fb83d4cc75511 Mon Sep 17 00:00:00 2001 From: Sebastian Huber Date: Fri, 17 Nov 2017 09:43:17 +0100 Subject: bsps: Use a state in default getentropy() 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. --- c/src/lib/libbsp/shared/getentropy-cpucounter.c | 65 +++++++++++++++---------- 1 file changed, 40 insertions(+), 25 deletions(-) diff --git a/c/src/lib/libbsp/shared/getentropy-cpucounter.c b/c/src/lib/libbsp/shared/getentropy-cpucounter.c index 15c8648047..8ef05df85c 100644 --- a/c/src/lib/libbsp/shared/getentropy-cpucounter.c +++ b/c/src/lib/libbsp/shared/getentropy-cpucounter.c @@ -20,35 +20,50 @@ * you need for example a strong crypto. */ +#include #include #include -#include +#include #include +#include + +static uint32_t state; int getentropy(void *ptr, size_t n) { - uint8_t *dest = ptr; - - while (n > 0) { - rtems_counter_ticks ticks; - - ticks = rtems_counter_read(); - - 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; - } - } - - return 0; + uint8_t *dest = ptr; + + state ^= rtems_counter_read(); + state *= 25169206; + state += 1679610226; + + while (n > 0) { + size_t m; + + m = MIN(n, sizeof(state)); + memcpy(dest, &state, m); + n -= m; + dest += m; + state *= 85236167; + state += 30557471; + } + + 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 +); -- cgit v1.2.3