Handle exception for get_signing_address to get previous behaviour

- Before deprecating `pyethereum` NULL_ADDRESS was returned instead of raising an exception

gnosis/safe/signatures.py

@@ -1,8 +1,11 @@
 from typing import List, Tuple, Union
 
 from eth_keys import keys
+from eth_keys.exceptions import BadSignature
 from hexbytes import HexBytes
 
+from gnosis.eth.constants import NULL_ADDRESS
+
 
 def signature_split(
     signatures: Union[bytes, str], pos: int = 0
@@ -53,7 +56,10 @@ def signatures_to_bytes(signatures: List[Tuple[int, int, int]]) -> bytes:
 def get_signing_address(signed_hash: Union[bytes, str], v: int, r: int, s: int) -> str:
     """
     :return: checksummed ethereum address, for example `0x568c93675A8dEb121700A6FAdDdfE7DFAb66Ae4A`
-    :rtype: str
+    :rtype: str or `NULL_ADDRESS` if signature is not valid
     """
-    public_key = keys.ecdsa_recover(signed_hash, keys.Signature(vrs=(v - 27, r, s)))
-    return public_key.to_checksum_address()
+    try:
+        public_key = keys.ecdsa_recover(signed_hash, keys.Signature(vrs=(v - 27, r, s)))
+        return public_key.to_checksum_address()
+    except BadSignature:
+        return NULL_ADDRESS

gnosis/safe/tests/test_signatures.py

@@ -0,0 +1,26 @@
+from django.test import TestCase
+
+from eth_account import Account
+from web3 import Web3
+
+from gnosis.eth.constants import NULL_ADDRESS
+
+from ..signatures import get_signing_address
+
+
+class TestSafeSignature(TestCase):
+    def test_get_signing_address(self):
+        account = Account.create()
+        # Random hash
+        random_hash = Web3.keccak(text="tanxugueiras")
+        signature = account.signHash(random_hash)
+        self.assertEqual(
+            get_signing_address(random_hash, signature.v, signature.r, signature.s),
+            account.address,
+        )
+
+        # Invalid signature will return the `NULL_ADDRESS`
+        self.assertEqual(
+            get_signing_address(random_hash, signature.v - 8, signature.r, signature.s),
+            NULL_ADDRESS,
+        )