py/bitbox02: add offset of 27 when signing an ETH message

The use of this offset for uncompressed pubkeys started in Bitcoin,
and in Ethereum, usage is inconsistent.

MyEtherWallet supports both when verifying:

https://github.com/MyEtherWallet/MyEtherWallet/blob/052f697f3b269db4378f331dbb89d24b406bb7c7/src/components/VerifyMessageInput/VerifyMessageInput.vue#L118

Trezor adds this offset as well.

The testing.aopp.group AOPP demo site requires the offset.

Author: benma

py/bitbox02/CHANGELOG.md

@@ -0,0 +1,4 @@
+# Changelog
+
+## 6.0.0
+- Offset the recoverable ID by 27 in the signature returned by `eth_sign_msg()`.

py/bitbox02/bitbox02/bitbox02/__init__.py

@@ -16,7 +16,7 @@
 from __future__ import print_function
 import sys
 
-__version__ = "5.3.0"
+__version__ = "6.0.0"
 
 if sys.version_info.major != 3 or sys.version_info.minor < 6:
     print(

py/bitbox02/bitbox02/bitbox02/bitbox02.py

@@ -774,8 +774,16 @@ def eth_sign_msg(
     ) -> bytes:
         """
         Signs message, the msg will be prefixed with "\x19Ethereum message\n" + len(msg) in the
-        hardware
+        hardware. 27 is added to the recID to denote an uncompressed pubkey.
         """
+
+        def format_as_uncompressed(sig: bytes) -> bytes:
+            # 27 is the magic constant to add to the recoverable ID to denote an uncompressed
+            # pubkey.
+            s = list(sig)
+            s[64] += 27
+            return bytes(s)
+
         request = eth.ETHRequest()
         # pylint: disable=no-member
         request.sign_msg.CopyFrom(eth.ETHSignMessageRequest(coin=coin, keypath=keypath, msg=msg))
@@ -800,9 +808,10 @@ def eth_sign_msg(
             if self.debug:
                 print(f"Antiklepto nonce verification PASSED")
 
-            return signature
+            return format_as_uncompressed(signature)
 
-        return self._eth_msg_query(request, expected_response="sign").sign.signature
+        signature = self._eth_msg_query(request, expected_response="sign").sign.signature
+        return format_as_uncompressed(signature)
 
     def reset(self) -> bool:
         """