bug: merkleProve

[zgfzgf]

uint size = (_auditPath.length - off) / 33;

for example: _auditPath.length - off = 65.
before 33 is ok. after 32 data (65-33) is is arbitrary.

eth-contracts/contracts/core/cross_chain_manager/libs/EthCrossChainUtils.sol

Lines 44 to 66 in d16252b

	function merkleProve(bytes memory _auditPath, bytes32 _root) internal pure returns (bytes memory) {
	uint256 off = 0;
	bytes memory value;
	(value, off) = ZeroCopySource.NextVarBytes(_auditPath, off);
	bytes32 hash = Utils.hashLeaf(value);
	uint size = (_auditPath.length - off) / 33;
	bytes32 nodeHash;
	byte pos;
	for (uint i = 0; i < size; i++) {
	(pos, off) = ZeroCopySource.NextByte(_auditPath, off);
	(nodeHash, off) = ZeroCopySource.NextHash(_auditPath, off);
	if (pos == 0x00) {
	hash = Utils.hashChildren(nodeHash, hash);
	} else if (pos == 0x01) {
	hash = Utils.hashChildren(hash, nodeHash);
	} else {
	revert("merkleProve, NextByte for position info failed");
	}
	}
	require(hash == _root, "merkleProve, expect root is not equal actual root");
	return value;
	}

[tanZiWen]

why you think it's a bug? how can attack it?