From 28d30ffd2f73e0288613699b52a04e52a455fb76 Mon Sep 17 00:00:00 2001
From: matejcik <ja@matejcik.cz>
Date: Wed, 6 Nov 2019 13:56:52 +0100
Subject: [PATCH] core/webauthn: unify signatures of Credential.from_bytes and
 friends

---
 core/src/apps/webauthn/credential.py | 10 ++++------
 core/src/apps/webauthn/fido2.py      | 11 +++++++----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/core/src/apps/webauthn/credential.py b/core/src/apps/webauthn/credential.py
index a1fe3bfaad..e1d479556c 100644
--- a/core/src/apps/webauthn/credential.py
+++ b/core/src/apps/webauthn/credential.py
@@ -54,7 +54,7 @@ class Credential:
         return storage.device.next_u2f_counter() or 0
 
     @staticmethod
-    def from_bytes(data: bytes, rp_id_hash: bytes) -> Optional["Credential"]:
+    def from_bytes(data: bytes, rp_id_hash: bytes) -> "Credential":
         try:
             return Fido2Credential.from_cred_id(data, rp_id_hash)
         except Exception:
@@ -274,11 +274,9 @@ class U2fCredential(Credential):
         return app_name
 
     @staticmethod
-    def from_key_handle(
-        key_handle: bytes, rp_id_hash: bytes
-    ) -> Optional["U2fCredential"]:
+    def from_key_handle(key_handle: bytes, rp_id_hash: bytes) -> "U2fCredential":
         if len(key_handle) != _KEY_HANDLE_LENGTH:
-            return None
+            raise ValueError  # key length mismatch
 
         # check the keyHandle and generate the signing key
         node = U2fCredential._node_from_key_handle(rp_id_hash, key_handle, "<8L")
@@ -289,7 +287,7 @@ class U2fCredential(Credential):
             node = U2fCredential._node_from_key_handle(rp_id_hash, key_handle, ">8L")
         if node is None:
             # specific error logged in msg_authenticate_genkey
-            return None
+            raise ValueError  # failed to parse key handle in either direction
 
         cred = U2fCredential()
         cred.id = key_handle
diff --git a/core/src/apps/webauthn/fido2.py b/core/src/apps/webauthn/fido2.py
index 32600b1921..7a0098ea52 100644
--- a/core/src/apps/webauthn/fido2.py
+++ b/core/src/apps/webauthn/fido2.py
@@ -1162,8 +1162,9 @@ def msg_authenticate(req: Msg, dialog_mgr: DialogManager) -> Cmd:
     khlen = req.data[_REQ_CMD_AUTHENTICATE_KHLEN]
     auth = overlay_struct(req.data, req_cmd_authenticate(khlen))
 
-    cred = Credential.from_bytes(auth.keyHandle, bytes(auth.appId))
-    if cred is None:
+    try:
+        cred = Credential.from_bytes(auth.keyHandle, bytes(auth.appId))
+    except Exception:
         # specific error logged in msg_authenticate_genkey
         return msg_error(req.cid, _SW_WRONG_DATA)
 
@@ -1264,9 +1265,11 @@ def credentials_from_descriptor_list(
         credential_id = credential_descriptor["id"]
         if not isinstance(credential_id, (bytes, bytearray)):
             raise TypeError
-        cred = Credential.from_bytes(credential_id, rp_id_hash)
-        if cred is not None:
+        try:
+            cred = Credential.from_bytes(credential_id, rp_id_hash)
             cred_list.append(cred)
+        except Exception:
+            pass
 
     return cred_list