slither-read-storage native POA support (#1843)

* Native support for POA networks in read_storage

* Set `srs.rpc` before `srs.block`

* Type hint

* New RpcInfo class w/ RpcInfo.web3 and RpcInfo.block
In SlitherReadStorage, self.rpc_info: Optional[RpcInfo]
replaces self.rpc, self._block, self._web3

* Black

* Update test_read_storage.py

* Add import in __init__.py

* Avoid instantiating SRS twice

* Add comment about `get_block` for POA networks

* Pylint

* Black

* Allow other valid block string arguments
["latest", "earliest", "pending", "safe", "finalized"]

* `args.block` can be in ["latest", "earliest", "pending", "safe", "finalized"]

* Use BlockTag enum class for valid `str` arguments

* Tweak `RpcInfo.__init__()` signature

* get rid of `or "latest"`

* Import BlockTag

* Use `web3.types.BlockIdentifier`

* Revert BlockTag enum

* Pylint and black

* Replace missing newline

* Update slither/tools/read_storage/__main__.py

Better, cleaner python

Co-authored-by: alpharush <0xalpharush@protonmail.com>

* Drop try/except around args.block parsing
allow ValueError if user provides invalid block arg

* Remove unused import

---------

Co-authored-by: alpharush <0xalpharush@protonmail.com>

slither/tools/read_storage/__init__.py

@@ -1 +1 @@
-from .read_storage import SlitherReadStorage
+from .read_storage import SlitherReadStorage, RpcInfo

slither/tools/read_storage/__main__.py

@@ -7,7 +7,7 @@ import argparse
 from crytic_compile import cryticparser
 
 from slither import Slither
-from slither.tools.read_storage.read_storage import SlitherReadStorage
+from slither.tools.read_storage.read_storage import SlitherReadStorage, RpcInfo
 
 
 def parse_args() -> argparse.Namespace:
@@ -126,14 +126,13 @@ def main() -> None:
     else:
         contracts = slither.contracts
 
-    srs = SlitherReadStorage(contracts, args.max_depth)
-
-    try:
-        srs.block = int(args.block)
-    except ValueError:
-        srs.block = str(args.block or "latest")
-
+    rpc_info = None
     if args.rpc_url:
+        valid = ["latest", "earliest", "pending", "safe", "finalized"]
+        block = args.block if args.block in valid else int(args.block)
+        rpc_info = RpcInfo(args.rpc_url, block)
+
+    srs = SlitherReadStorage(contracts, args.max_depth, rpc_info)
     # Remove target prefix e.g. rinkeby:0x0 -> 0x0.
     address = target[target.find(":") + 1 :]
     # Default to implementation address unless a storage address is given.
@@ -141,8 +140,6 @@ def main() -> None:
         args.storage_address = address
     srs.storage_address = args.storage_address
 
-        srs.rpc = args.rpc_url
-
     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

@@ -6,8 +6,11 @@ import dataclasses
 
 from eth_abi import decode, encode
 from eth_typing.evm import ChecksumAddress
-from eth_utils import keccak
+from eth_utils import keccak, to_checksum_address
 from web3 import Web3
+from web3.types import BlockIdentifier
+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
@@ -42,18 +45,43 @@ class SlitherReadStorageException(Exception):
     pass
 
 
+class RpcInfo:
+    def __init__(self, rpc_url: str, block: BlockIdentifier = "latest") -> None:
+        assert isinstance(block, int) or block in [
+            "latest",
+            "earliest",
+            "pending",
+            "safe",
+            "finalized",
+        ]
+        self.rpc: str = rpc_url
+        self._web3: Web3 = Web3(Web3.HTTPProvider(self.rpc))
+        """If the RPC is for a POA network, the first call to get_block fails, so we inject geth_poa_middleware"""
+        try:
+            self._block: int = self.web3.eth.get_block(block)["number"]
+        except ExtraDataLengthError:
+            self._web3.middleware_onion.inject(geth_poa_middleware, layer=0)
+            self._block: int = self.web3.eth.get_block(block)["number"]
+
+    @property
+    def web3(self) -> Web3:
+        return self._web3
+
+    @property
+    def block(self) -> int:
+        return self._block
+
+
 # pylint: disable=too-many-instance-attributes
 class SlitherReadStorage:
-    def __init__(self, contracts: List[Contract], max_depth: int) -> None:
+    def __init__(self, contracts: List[Contract], max_depth: int, rpc_info: RpcInfo = None) -> None:
         self._checksum_address: Optional[ChecksumAddress] = None
         self._contracts: List[Contract] = contracts
         self._log: str = ""
         self._max_depth: int = max_depth
         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.rpc: Optional[str] = None
+        self.rpc_info: Optional[RpcInfo] = rpc_info
         self.storage_address: Optional[str] = None
         self.table: Optional[MyPrettyTable] = None
 
@@ -73,18 +101,12 @@ class SlitherReadStorage:
     def log(self, log: str) -> None:
         self._log = log
 
-    @property
-    def web3(self) -> Web3:
-        if not self._web3:
-            self._web3 = Web3(Web3.HTTPProvider(self.rpc))
-        return self._web3
-
     @property
     def checksum_address(self) -> ChecksumAddress:
         if not self.storage_address:
             raise ValueError
         if not self._checksum_address:
-            self._checksum_address = self.web3.to_checksum_address(self.storage_address)
+            self._checksum_address = to_checksum_address(self.storage_address)
         return self._checksum_address
 
     @property
@@ -223,11 +245,12 @@ class SlitherReadStorage:
         """Fetches the slot value of `SlotInfo` object
         :param slot_info:
         """
+        assert self.rpc_info is not None
         hex_bytes = get_storage_data(
-            self.web3,
+            self.rpc_info.web3,
             self.checksum_address,
             int.to_bytes(slot_info.slot, 32, byteorder="big"),
-            self.block,
+            self.rpc_info.block,
         )
         slot_info.value = self.convert_value_to_type(
             hex_bytes, slot_info.size, slot_info.offset, slot_info.type_string
@@ -600,15 +623,15 @@ class SlitherReadStorage:
             (int): The length of the array.
         """
         val = 0
-        if self.rpc:
+        if self.rpc_info:
             # The length of dynamic arrays is stored at the starting slot.
             # Convert from hexadecimal to decimal.
             val = int(
                 get_storage_data(
-                    self.web3,
+                    self.rpc_info.web3,
                     self.checksum_address,
                     int.to_bytes(slot, 32, byteorder="big"),
-                    self.block,
+                    self.rpc_info.block,
                 ).hex(),
                 16,
             )

tests/tools/read-storage/test_read_storage.py

@@ -12,7 +12,7 @@ from web3 import Web3
 from web3.contract import Contract
 
 from slither import Slither
-from slither.tools.read_storage import SlitherReadStorage
+from slither.tools.read_storage import SlitherReadStorage, RpcInfo
 
 TEST_DATA_DIR = Path(__file__).resolve().parent / "test_data"
 
@@ -105,8 +105,8 @@ def test_read_storage(web3, ganache, solc_binary_path) -> None:
     sl = Slither(Path(TEST_DATA_DIR, "storage_layout-0.8.10.sol").as_posix(), solc=solc_path)
     contracts = sl.contracts
 
-    srs = SlitherReadStorage(contracts, 100)
-    srs.rpc = ganache.provider
+    rpc_info: RpcInfo = RpcInfo(ganache.provider)
+    srs = SlitherReadStorage(contracts, 100, rpc_info)
     srs.storage_address = address
     srs.get_all_storage_variables()
     srs.get_storage_layout()