1 files changed, 88 insertions, 0 deletions
diff --git a/python-packages/order_utils/src/zero_ex/order_utils/signature_utils.py b/python-packages/order_utils/src/zero_ex/order_utils/signature_utils.py
new file mode 100644
index 000000000..12525ba88
--- /dev/null
+++ b/python-packages/order_utils/src/zero_ex/order_utils/signature_utils.py
@@ -0,0 +1,88 @@
+"""Signature utilities."""
+
+from typing import Dict, Tuple
+import json
+from pkg_resources import resource_string
+
+from eth_utils import is_address, to_checksum_address
+from web3 import Web3
+import web3.exceptions
+from web3.utils import datatypes
+
+from zero_ex.dev_utils.type_assertions import assert_is_hex_string
+
+
+# prefer `black` formatting. pylint: disable=C0330
+EXCHANGE_ABI = json.loads(
+    resource_string("zero_ex.contract_artifacts", "artifacts/Exchange.json")
+)["compilerOutput"]["abi"]
+
+network_to_exchange_addr: Dict[str, str] = {
+    "1": "0x4f833a24e1f95d70f028921e27040ca56e09ab0b",
+    "3": "0x4530c0483a1633c7a1c97d2c53721caff2caaaaf",
+    "42": "0x35dd2932454449b14cee11a94d3674a936d5d7b2",
+    "50": "0x48bacb9266a570d521063ef5dd96e61686dbe788",
+}
+
+
+# prefer `black` formatting. pylint: disable=C0330
+def is_valid_signature(
+    provider: Web3.HTTPProvider, data: str, signature: str, signer_address: str
+) -> Tuple[bool, str]:
+    # docstring considered all one line by pylint: disable=line-too-long
+    """Check the validity of the supplied signature.
+
+    Check if the supplied ``signature`` corresponds to signing ``data`` with
+    the private key corresponding to ``signer_address``.
+
+    :param provider: A Web3 provider able to access the 0x Exchange contract.
+    :param data: The hex encoded data signed by the supplied signature.
+    :param signature: The hex encoded signature.
+    :param signer_address: The hex encoded address that signed the data to
+        produce the supplied signature.
+    :rtype: Boolean indicating whether the given signature is valid.
+
+    >>> is_valid_signature(
+    ...     Web3.HTTPProvider("http://127.0.0.1:8545"),
+    ...     '0x6927e990021d23b1eb7b8789f6a6feaf98fe104bb0cf8259421b79f9a34222b0',
+    ...     '0x1B61a3ed31b43c8780e905a260a35faefcc527be7516aa11c0256729b5b351bc3340349190569279751135161d22529dc25add4f6069af05be04cacbda2ace225403',
+    ...     '0x5409ed021d9299bf6814279a6a1411a7e866a631',
+    ... )
+    (True, '')
+    """  # noqa: E501 (line too long)
+    # TODO: make this provider check more flexible. pylint: disable=fixme
+    # https://app.asana.com/0/684263176955174/901300863045491/f
+    if not isinstance(provider, Web3.HTTPProvider):
+        raise TypeError("provider is not a Web3.HTTPProvider")
+    assert_is_hex_string(data, "data")
+    assert_is_hex_string(signature, "signature")
+    assert_is_hex_string(signer_address, "signer_address")
+    if not is_address(signer_address):
+        raise ValueError("signer_address is not a valid address")
+
+    web3_instance = Web3(provider)
+    # false positive from pylint: disable=no-member
+    network_id = web3_instance.net.version
+    contract_address = network_to_exchange_addr[network_id]
+    # false positive from pylint: disable=no-member
+    contract: datatypes.Contract = web3_instance.eth.contract(
+        address=to_checksum_address(contract_address), abi=EXCHANGE_ABI
+    )
+    try:
+        return (
+            contract.call().isValidSignature(
+                data, to_checksum_address(signer_address), signature
+            ),
+            "",
+        )
+    except web3.exceptions.BadFunctionCallOutput as exception:
+        known_revert_reasons = [
+            "LENGTH_GREATER_THAN_0_REQUIRED",
+            "SIGNATURE_UNSUPPORTED",
+            "LENGTH_0_REQUIRED",
+            "LENGTH_65_REQUIRED",
+        ]
+        for known_revert_reason in known_revert_reasons:
+            if known_revert_reason in str(exception):
+                return (False, known_revert_reason)
+        return (False, f"Unknown: {exception}")