"""Validates State Proof."""
import json
from collections import OrderedDict
from rlp import DecodingError
from rlp import decode as rlp_decode
from rlp import encode as rlp_encode
from .constants import (
BLANK_NODE,
NODE_TYPE_BLANK,
NODE_TYPE_BRANCH,
NODE_TYPE_EXTENSION,
NODE_TYPE_LEAF,
)
from .utils import NIBBLE_TERMINATOR, sha3_256, unpack_to_nibbles
[docs]
class SubTrie:
"""Utility class for SubTrie and State Proof validation."""
def __init__(self, root_hash=None):
"""MPT SubTrie dictionary like interface."""
self._subtrie = OrderedDict()
self.set_root_hash(root_hash)
@property
def root_hash(self):
"""Return 32 bytes string."""
return self._root_hash
@root_hash.setter
def root_hash(self, value):
self.set_root_hash(value)
[docs]
def set_root_hash(self, root_hash=None):
"""."""
self._root_hash = root_hash
@staticmethod
def _get_node_type(node):
if node == BLANK_NODE:
return NODE_TYPE_BLANK
if len(node) == 2:
nibbles = unpack_to_nibbles(node[0])
has_terminator = nibbles and nibbles[-1] == NIBBLE_TERMINATOR
return NODE_TYPE_LEAF if has_terminator else NODE_TYPE_EXTENSION
if len(node) == 17:
return NODE_TYPE_BRANCH
[docs]
@staticmethod
async def verify_spv_proof(expected_value, proof_nodes, serialized=True):
"""Verify State Proof."""
try:
if serialized:
proof_nodes = rlp_decode(proof_nodes)
new_trie = await SubTrie.get_new_trie_with_proof_nodes(proof_nodes)
expected_value = json.loads(expected_value)
for encoded_node in list(new_trie._subtrie.values()):
try:
decoded_node = rlp_decode(encoded_node)
# branch node
if SubTrie._get_node_type(decoded_node) == NODE_TYPE_BRANCH:
if (
json.loads(rlp_decode(decoded_node[-1])[0].decode("utf-8"))
) == expected_value:
return True
# leaf or extension node
if SubTrie._get_node_type(decoded_node) == NODE_TYPE_LEAF:
if (
json.loads(rlp_decode(decoded_node[1])[0].decode("utf-8"))
) == expected_value:
return True
except DecodingError:
continue
return False
except Exception:
return False
[docs]
@staticmethod
async def get_new_trie_with_proof_nodes(proof_nodes):
"""Return SubTrie created from proof_nodes."""
new_trie = SubTrie()
for node in proof_nodes:
R = rlp_encode(node)
H = sha3_256(R)
new_trie._subtrie[H] = R
return new_trie