added a check for POA extraData

fixed linting errors

Author: voith

tests/core/eth-module/test_poa.py

@@ -1,5 +1,8 @@
 import pytest
 
+from web3.exceptions import (
+    ValidationError,
+)
 from web3.middleware import (
     construct_fixture_middleware,
     geth_poa_middleware,
@@ -12,7 +15,7 @@ def test_long_extra_data(web3):
         'eth_getBlockByNumber': {'extraData': '0x' + 'ff' * 33},
     })
     web3.middleware_stack.inject(return_block_with_long_extra_data, layer=0)
-    with pytest.raises(ValueError):
+    with pytest.raises(ValidationError):
         web3.eth.getBlock('latest')
 
 

web3/middleware/validation.py

@@ -1,11 +1,17 @@
 from cytoolz import (
+    complement,
     compose,
     curry,
     dissoc,
 )
 from eth_utils.curried import (
     apply_formatter_at_index,
+    apply_formatter_if,
     apply_formatters_to_dict,
+    is_null,
+)
+from hexbytes import (
+    HexBytes,
 )
 
 from web3.exceptions import (
@@ -15,6 +21,11 @@
     construct_web3_formatting_middleware,
 )
 
+MAX_EXTRADATA_LENGTH = 32
+
+
+is_not_null = complement(is_null)
+
 
 @curry
 def validate_chain_id(web3, chain_id):
@@ -30,6 +41,23 @@ def validate_chain_id(web3, chain_id):
         )
 
 
+def check_extradata_length(val):
+    if not isinstance(val, (str, int, bytes)):
+        return val
+    result = HexBytes(val)
+    if len(result) > MAX_EXTRADATA_LENGTH:
+        raise ValidationError(
+            "The field extraData is %d bytes, but should be %d. "
+            "It is quite likely that you are connected to a POA chain. "
+            "Refer "
+            "http://web3py.readthedocs.io/en/latest/middleware.html#geth-style-proof-of-authority "
+            "for more details. The full extraData is: %r" % (
+                len(result), MAX_EXTRADATA_LENGTH, result
+            )
+        )
+    return val
+
+
 def transaction_normalizer(transaction):
     return dissoc(transaction, 'chainId')
 
@@ -44,6 +72,14 @@ def transaction_param_validator(web3):
     )
 
 
+BLOCK_VALIDATORS = {
+    'extraData': check_extradata_length,
+}
+
+
+block_validator = apply_formatters_to_dict(BLOCK_VALIDATORS)
+
+
 @curry
 def chain_id_validator(web3):
     return compose(
@@ -52,13 +88,20 @@ def chain_id_validator(web3):
     )
 
 
+extra_data_validator = apply_formatter_if(is_not_null, block_validator)
+
+
 def build_validators_with_web3(w3):
     return dict(
         request_formatters={
             'eth_sendTransaction': chain_id_validator(w3),
             'eth_estimateGas': chain_id_validator(w3),
             'eth_call': chain_id_validator(w3),
-        }
+        },
+        result_formatters={
+            'eth_getBlockByHash': extra_data_validator,
+            'eth_getBlockByNumber': extra_data_validator,
+        },
     )