core: add new RNG implementation

Adds a new cryptographically secure pseudo random number generator known
as Fortuna. The implementation is based on the description in [0]. This
implementation replaces the implementation in LTC which was used until
now.

Gathering of entropy has been refined with crypto_rng_add_event() to
better match how entropy is added to Fortuna. A enum crypto_rng_src
identifies the source of the event. The source also controls how the
event is added. There are two options available, queue it in a circular
buffer for later processing or adding it directly to a pool. The former
option is suitable when being called from an interrupt handler or some
other place where RPC to normal world is forbidden.

plat_prng_add_jitter_entropy_norpc() is removed and
plat_prng_add_jitter_entropy() is updated to use this new entropy source
scheme.

The configuration of LTC is simplified by this, now PRNG is always drawn
via prng_mpa_desc.

plat_rng_init() takes care of initializing the PRNG in order to allow
platforms to override or enhance the Fortuna integration.

[0] Link:https://www.schneier.com/academic/paperfiles/fortuna.pdf

Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/core/drivers/imx_snvs.c b/core/drivers/imx_snvs.c
index bf5a7df6..278d42f9 100644
--- a/core/drivers/imx_snvs.c
+++ b/core/drivers/imx_snvs.c
@@ -157,7 +157,7 @@ TEE_Result snvs_srtc_enable(void)
 }
 
 /* Reused from tee_time_arm_cntpct.c */
-void plat_prng_add_jitter_entropy(void)
+void plat_prng_add_jitter_entropy(enum crypto_rng_src sid, unsigned int *pnum)
 {
 	uint64_t tsc = snvs_srtc_read_lp_counter();
 	int bytes = 0, n;
@@ -181,6 +181,6 @@ void plat_prng_add_jitter_entropy(void)
 	if (bytes) {
 		FMSG("%s: 0x%02" PRIX16, __func__,
 		     acc & GENMASK_32(bytes * 8, 0));
-		tee_prng_add_entropy((uint8_t *)&acc, bytes);
+		crypto_rng_add_event(sid, pnum, (uint8_t *)&acc, bytes);
 	}
 }