fix usage of RNG before setup

trezor/trezor-mcu@c8c8542
keepkey · Feb 19, 2018 · e4fc493 · e4fc493
1 parent 4531790
commit e4fc493
Show file tree

Hide file tree

Showing 2 changed files with 9 additions and 2 deletions.
diff --git a/keepkey/local/baremetal/keepkey_main.c b/keepkey/local/baremetal/keepkey_main.c
@@ -94,11 +94,12 @@ static void screen_test(void)
  */
 int main(void)
 {
+    /* Init board */
+    board_init();
+
     /* Init for safeguard against stack overflow (-fstack-protector-all) */
     __stack_chk_guard = (uintptr_t)random32();
 
-    /* Init board */
-    board_init();
     led_func(SET_RED_LED);
     dbg_print("Application Version %d.%d.%d\n\r", MAJOR_VERSION, MINOR_VERSION,
               PATCH_VERSION);

diff --git a/keepkey_board/local/baremetal/keepkey_board.c b/keepkey_board/local/baremetal/keepkey_board.c
@@ -31,6 +31,8 @@
 
 #include "keepkey_board.h"
 
+#include "rng.h"
+
 /* === Variables =========================================================== */
 
 /* Stack smashing protector (SSP) canary value storage */
@@ -99,6 +101,10 @@ void reset_rng(void)
     RNG_CR |= RNG_CR_IE | RNG_CR_RNGEN;
     /* this delay is required before rng data can be read */
     delay_us(5);
+
+    // to be extra careful and heed the STM32F205xx Reference manual, Section 20.3.1
+    // we don't use the first random number generated after setting the RNGEN bit in setup
+    random32();
 }
 
 /*