From 2cedc687e63f09fe3f372c8bdfaba7afca981c86 Mon Sep 17 00:00:00 2001
From: matejcik <ja@matejcik.cz>
Date: Wed, 29 Apr 2020 10:59:10 +0200
Subject: [PATCH] core: disable trezor-crypto BIP32 cache

---
 core/SConscript.firmware                      |  1 +
 core/SConscript.unix                          |  1 +
 .../modtrezorcrypto/modtrezorcrypto-bip32.h   | 23 +++++++++----------
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/core/SConscript.firmware b/core/SConscript.firmware
index a4f60c7c7..96c07d8c2 100644
--- a/core/SConscript.firmware
+++ b/core/SConscript.firmware
@@ -36,6 +36,7 @@ CPPDEFINES_MOD += [
     'AES_128',
     'AES_192',
     'RAND_PLATFORM_INDEPENDENT',
+    ('USE_BIP32_CACHE', '0'),
     ('USE_KECCAK', '1'),
     ('USE_ETHEREUM', '1' if EVERYTHING else '0'),
     ('USE_MONERO', '1' if EVERYTHING else '0'),
diff --git a/core/SConscript.unix b/core/SConscript.unix
index 03e34776f..f1bff0901 100644
--- a/core/SConscript.unix
+++ b/core/SConscript.unix
@@ -34,6 +34,7 @@ CPPPATH_MOD += [
 CPPDEFINES_MOD += [
     'AES_128',
     'AES_192',
+    ('USE_BIP32_CACHE', '0'),
     ('USE_KECCAK', '1'),
     ('USE_ETHEREUM', '1' if EVERYTHING else '0'),
     ('USE_MONERO', '1' if EVERYTHING else '0'),
diff --git a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
index 04648e930..96f8d6bfe 100644
--- a/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
+++ b/core/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
@@ -240,18 +240,17 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_derive_path(mp_obj_t self,
     mp_raise_ValueError("Path cannot be longer than 32 indexes");
   }
 
-  // convert path to int array
-  uint32_t pi;
-  uint32_t pints[plen];
-  for (pi = 0; pi < plen; pi++) {
-    pints[pi] = trezor_obj_get_uint(pitems[pi]);
-  }
-
-  if (!hdnode_private_ckd_cached(&o->hdnode, pints, plen, &o->fingerprint)) {
-    // derivation failed, reset the state and raise
-    o->fingerprint = 0;
-    memzero(&o->hdnode, sizeof(o->hdnode));
-    mp_raise_ValueError("Failed to derive path");
+  for (uint32_t pi = 0; pi < plen; pi++) {
+    if (pi == plen - 1) {
+      // fingerprint is calculated from the parent of the final derivation
+      o->fingerprint = hdnode_fingerprint(&o->hdnode);
+    }
+    uint32_t pitem = trezor_obj_get_uint(pitems[pi]);
+    if (!hdnode_private_ckd(&o->hdnode, pitem)) {
+      o->fingerprint = 0;
+      memzero(&o->hdnode, sizeof(o->hdnode));
+      mp_raise_ValueError("Failed to derive path");
+    }
   }
 
   return mp_const_none;