Add storage_lock().

storage.c

@@ -641,6 +641,13 @@ static secbool pin_get_fails(uint32_t *ctr)
     return sectrue;
 }
 
+void storage_lock(void)
+{
+    unlocked = secfalse;
+    memzero(cached_keys, sizeof(cached_keys));
+    memzero(authentication_sum, sizeof(authentication_sum));
+}
+
 static secbool unlock(uint32_t pin)
 {
     const void *buffer = NULL;

storage.h

@@ -29,6 +29,7 @@ typedef void (*PIN_UI_WAIT_CALLBACK)(uint32_t wait, uint32_t progress);
 void storage_init(PIN_UI_WAIT_CALLBACK callback, const uint8_t *salt, const uint16_t salt_len);
 void storage_wipe(void);
 void storage_wipe_ex(uint32_t new_pin, uint32_t pin_fail_count);
+void storage_lock(void);
 secbool storage_unlock(const uint32_t pin);
 secbool storage_has_pin(void);
 uint32_t storage_get_pin_rem(void);