core/reset: check three words

closes #289

core/src/apps/management/common/layout.py

@@ -68,15 +68,16 @@ async def confirm_backup_again(ctx):
 async def _confirm_share_words(ctx, share_index, share_words):
     numbered = list(enumerate(share_words))
 
-    # check a word from the first half
+    # check three words
-    first_half = numbered[: len(numbered) // 2]
+    third = len(numbered) // 3
-    if not await _confirm_word(ctx, share_index, first_half):
+    # if the num of words is not dividable by 3 let's add 1
-        return False
+    # to have more words at the beggining and to check all of them
-
+    if len(numbered) % 3:
-    # check a word from the second half
+        third += 1
-    second_half = numbered[len(numbered) // 2 :]
+
-    if not await _confirm_word(ctx, share_index, second_half):
+    for part in utils.chunks(numbered, third):
-        return False
+        if not await _confirm_word(ctx, share_index, part):
+            return False
 
     return True
 

python/trezorlib/tests/device_tests/test_msg_resetdevice_shamir.py

@@ -84,7 +84,7 @@ class TestMsgResetDeviceT2(TrezorTest):
                         self.client.debug.press_yes()
 
                 # check share
-                for _ in range(2):
+                for _ in range(3):
                     time.sleep(1)
                     index = self.client.debug.state().reset_word_pos
                     self.client.debug.input(words[index])

python/trezorlib/tests/device_tests/test_msg_resetdevice_t2.py

@@ -64,7 +64,7 @@ class TestMsgResetDeviceT2(TrezorTest):
                     self.client.debug.press_yes()
 
             # check backup words
-            for _ in range(2):
+            for _ in range(3):
                 time.sleep(1)
                 index = self.client.debug.state().reset_word_pos
                 self.client.debug.input(words[index])
@@ -169,7 +169,7 @@ class TestMsgResetDeviceT2(TrezorTest):
                     self.client.debug.press_yes()
 
             # check backup words
-            for _ in range(2):
+            for _ in range(3):
                 time.sleep(1)
                 index = self.client.debug.state().reset_word_pos
                 self.client.debug.input(words[index])