sys/fortuna: remove need for now64

Use a timer to required a reseed, enable use of plain ztimer (no now64)

makefiles/pseudomodules.inc.mk

@@ -122,6 +122,7 @@ PSEUDOMODULES += posix_headers
 PSEUDOMODULES += printf_float
 PSEUDOMODULES += prng
 PSEUDOMODULES += prng_%
+PSEUDOMODULES += fortuna_reseed
 PSEUDOMODULES += qmc5883l_int
 PSEUDOMODULES += riotboot_%
 PSEUDOMODULES += rtt_cmd

sys/Kconfig

@@ -70,6 +70,10 @@ config MODULE_LIBSTDCPP
     depends on HAS_CPP
     select MODULE_CPP
 
+config MODULE_ATOMIC_UTILS
+    bool "Atomic access utility functions"
+    depends on TEST_KCONFIG
+
 config MODULE_SYS
     bool
     default y

sys/Makefile.dep

@@ -419,7 +419,10 @@ ifneq (,$(filter random,$(USEMODULE)))
     USEMODULE += fortuna
     USEMODULE += hashes
     USEMODULE += crypto
-    USEMODULE += xtimer
+    ifneq (,$(filter fortuna_reseed,$(USEMODULE)))
+        USEMODULE += atomic_utils
+        USEMODULE += xtimer
+    endif
   endif
 
   ifneq (,$(filter prng_tinymt32,$(USEMODULE)))

sys/random/Kconfig

@@ -19,14 +19,21 @@ choice RANDOM_IMPLEMENTATION
     default MODULE_PRNG_HWRNG if HAS_PERIPH_HWRNG
     default MODULE_PRNG_TINYMT32
 
-config MODULE_PRNG_FORTUNA
+menuconfig MODULE_PRNG_FORTUNA
     bool "Fortuna"
     select MODULE_HASHES
-    select MODULE_XTIMER
     select MODULE_FORTUNA
     select MODULE_CRYPTO
     select MODULE_CRYPTO_AES_128
 
+if MODULE_PRNG_FORTUNA
+
+config MODULE_FORTUNA_RESEED
+    bool "Reseed prng according to FORTUNA_RESEED_INTERVAL_MS"
+    select MODULE_XTIMER
+    select MODULE_ATOMIC_UTILS
+endif
+
 config MODULE_PRNG_HWRNG
     bool "Hardware RNG"
     depends on HAS_PERIPH_HWRNG

sys/random/fortuna.c

@@ -21,7 +21,6 @@
 
 #include "log.h"
 #include "mutex.h"
-
 #include "fortuna/fortuna.h"
 
 /**

sys/random/fortuna/fortuna.c

@@ -6,8 +6,16 @@
  */
 
 #include <string.h>
-
 #include "fortuna.h"
+#include "kernel_defines.h"
+#if FORTUNA_RESEED_INTERVAL_MS > 0 && IS_USED(MODULE_FORTUNA_RESEED)
+#include "atomic_utils.h"
+#if IS_USED(MODULE_ZTIMER_MSEC)
+#include "ztimer.h"
+#else
+#include "xtimer.h"
+#endif
+#endif
 
 /**
  * @brief Helper to increment the 128-bit counter (see section 9.4).
@@ -137,6 +145,31 @@ static int fortuna_pseudo_random_data(fortuna_state_t *state, uint8_t *out,
     return 0;
 }
 
+#if FORTUNA_RESEED_INTERVAL_MS > 0 && IS_USED(MODULE_FORTUNA_RESEED)
+void _reseed_callback(void *arg)
+{
+    fortuna_state_t *state = (fortuna_state_t *) arg;
+    state->needs_reseed = 1;
+}
+
+static void _reseed_timer_set(fortuna_state_t *state)
+{
+    atomic_store_u8(&state->needs_reseed, 0);
+#if IS_USED(MODULE_ZTIMER_MSEC)
+    ztimer_set(ZTIMER_MSEC, &state->reseed_timer, FORTUNA_RESEED_INTERVAL_MS);
+#else
+    xtimer_set(&state->reseed_timer, FORTUNA_RESEED_INTERVAL_MS * US_PER_MS);
+#endif
+}
+
+static void _reseed_timer_init(fortuna_state_t *state) {
+    /* initialize reseed timer */
+    state->reseed_timer.callback = _reseed_callback;
+    state->reseed_timer.arg = state;
+    _reseed_timer_set(state);
+}
+#endif
+
 /*
  * Corresponds to section 9.4.1 and 9.5.4.
  */
@@ -149,9 +182,9 @@ int fortuna_init(fortuna_state_t *state)
         sha256_init(&state->pools[i].ctx);
     }
 
-#if FORTUNA_RESEED_INTERVAL
-    /* set last reseed to ensure initial time diff is correct */
-    state->last_reseed = xtimer_now_usec64();
+#if FORTUNA_RESEED_INTERVAL_MS > 0 && IS_USED(MODULE_FORTUNA_RESEED)
+    /* reseed time init if required */
+    _reseed_timer_init(state);
 #endif
 
 #if FORTUNA_LOCK
@@ -174,9 +207,9 @@ int fortuna_random_data(fortuna_state_t *state, uint8_t *out, size_t bytes)
 #endif
 
     /* reseed the generator if needed, before returning data */
-#if FORTUNA_RESEED_INTERVAL
+#if FORTUNA_RESEED_INTERVAL_MS > 0 && IS_USED(MODULE_FORTUNA_RESEED)
     if (state->pools[0].len >= FORTUNA_MIN_POOL_SIZE &&
-        (xtimer_now_usec64() - state->last_reseed) > FORTUNA_RESEED_INTERVAL) {
+        atomic_load_u8(&state->needs_reseed)) {
 #else
     if (state->pools[0].len >= FORTUNA_MIN_POOL_SIZE) {
 #endif
@@ -196,8 +229,8 @@ int fortuna_random_data(fortuna_state_t *state, uint8_t *out, size_t bytes)
 
         fortuna_reseed(state, buf, len);
 
-#if FORTUNA_RESEED_INTERVAL
-        state->last_reseed = xtimer_now_usec64();
+#if FORTUNA_RESEED_INTERVAL_MS > 0 && IS_USED(MODULE_FORTUNA_RESEED)
+        _reseed_timer_set(state);
 #endif
 
 #if FORTUNA_CLEANUP

sys/random/fortuna/fortuna.h

@@ -27,8 +27,14 @@
 #ifndef FORTUNA_H
 #define FORTUNA_H
 
-#include "xtimer.h"
 #include "mutex.h"
+#if FORTUNA_RESEED_INTERVAL_MS > 0 && IS_USED(MODULE_FORTUNA_RESEED)
+#if IS_USED(MODULE_ZTIMER_MSEC)
+#include "ztimer.h"
+#else
+#include "xtimer.h"
+#endif
+#endif
 
 #include "crypto/aes.h"
 #include "hashes/sha256.h"
@@ -63,13 +69,17 @@ extern "C" {
 #define FORTUNA_SEED_SIZE           (64U)
 #endif
 
+#if IS_USED(MODULE_FORTUNA_RESEED) || DOXYGEN
 /**
  * @brief Reseed interval in us. After this interval, the PRNG must be
  *        reseeded. Per section 9.5.5, the recommended value is 100ms. Set to
  *        zero to disable this security feature.
+ *
+ * @note Requires `fortuna_reseed` module.
  */
-#ifndef FORTUNA_RESEED_INTERVAL
-#define FORTUNA_RESEED_INTERVAL     (0)
+#ifndef FORTUNA_RESEED_INTERVAL_MS
+#define FORTUNA_RESEED_INTERVAL_MS  100
+#endif
 #endif
 
 /**
@@ -138,12 +148,17 @@ typedef struct {
     fortuna_generator_t gen;
     fortuna_pool_t pools[FORTUNA_POOLS];
     uint32_t reseeds;
-#if FORTUNA_RESEED_INTERVAL > 0
-    uint64_t last_reseed;
-#endif
 #if FORTUNA_LOCK
     mutex_t lock;
 #endif
+#if FORTUNA_RESEED_INTERVAL_MS > 0 && IS_USED(MODULE_FORTUNA_RESEED)
+#if IS_USED(MODULE_ZTIMER_MSEC)
+    ztimer_t reseed_timer;
+#else
+    xtimer_t reseed_timer;
+#endif
+    uint8_t needs_reseed;
+#endif
 } fortuna_state_t;
 
 /**