slither-read-storage native POA support

slither/tools/read_storage/__main__.py

@@ -128,11 +128,6 @@ def main() -> None:
 
     srs = SlitherReadStorage(contracts, args.max_depth)
 
-    try:
-        srs.block = int(args.block)
-    except ValueError:
-        srs.block = str(args.block or "latest")
-
     if args.rpc_url:
         # Remove target prefix e.g. rinkeby:0x0 -> 0x0.
         address = target[target.find(":") + 1 :]
@@ -143,6 +138,11 @@ def main() -> None:
 
         srs.rpc = args.rpc_url
 
+    try:
+        srs.block = int(args.block)
+    except ValueError:
+        srs.block = str(args.block or "latest")
+
     if args.variable_name:
         # Use a lambda func to only return variables that have same name as target.
         # x is a tuple (`Contract`, `StateVariable`).

slither/tools/read_storage/read_storage.py

@@ -8,6 +8,8 @@
 from eth_typing.evm import ChecksumAddress
 from eth_utils import keccak
 from web3 import Web3
+from web3.exceptions import ExtraDataLengthError
+from web3.middleware import geth_poa_middleware
 
 from slither.core.declarations import Contract, Structure
 from slither.core.solidity_types import ArrayType, ElementaryType, MappingType, UserDefinedType
@@ -52,7 +54,7 @@ def __init__(self, contracts: List[Contract], max_depth: int) -> None:
         self._slot_info: Dict[str, SlotInfo] = {}
         self._target_variables: List[Tuple[Contract, StateVariable]] = []
         self._web3: Optional[Web3] = None
-        self.block: Union[str, int] = "latest"
+        self._block: Optional[int] = None
         self.rpc: Optional[str] = None
         self.storage_address: Optional[str] = None
         self.table: Optional[MyPrettyTable] = None
@@ -73,6 +75,26 @@ def log(self) -> str:
     def log(self, log: str) -> None:
         self._log = log
 
+    @property
+    def block(self) -> int:
+        """If the RPC is for a POA network, the first call to get_block fails, so we inject geth_poa_middleware"""
+        if not self._block:
+            try:
+                self._block = self.web3.eth.get_block("latest")["number"]
+            except ExtraDataLengthError:
+                self.web3.middleware_onion.inject(geth_poa_middleware, layer=0)
+                self._block = self.web3.eth.get_block("latest")["number"]
+        return self._block
+
+    @block.setter
+    def block(self, block: Union[str, int]) -> None:
+        """If the RPC is for a POA network, the first call to get_block fails, so we inject geth_poa_middleware"""
+        try:
+            self._block = self.web3.eth.get_block(block)["number"]
+        except ExtraDataLengthError:
+            self.web3.middleware_onion.inject(geth_poa_middleware, layer=0)
+            self._block = self.web3.eth.get_block(block)["number"]
+
     @property
     def web3(self) -> Web3:
         if not self._web3: