decoder.py

import requests
from evmdasm import EvmBytecode
from termcolor import cprint
from tqdm import tqdm
from time import sleep
from json import JSONDecodeError
from web3 import Web3

import kofig

def getHashes(bytecode) -> list:
    opcodes = EvmBytecode(bytecode).disassemble()

    hashes = set()
    for i in range(len(opcodes) - 3):
        if (
            opcodes[i].name == "PUSH4"
            and opcodes[i + 1].name == "EQ"
            and opcodes[i + 2].name == "PUSH2"
            and opcodes[i + 3].name == "JUMPI"
        ):
            hashes.add(opcodes[i].operand)
    return list(hashes)

def getSignature(hash):
    response = requests.get('https://www.4byte.directory/api/v1/signatures/?hex_signature=' + hash)
    try:
        results = response.json()['results']
        results.sort(key=lambda r: r['created_at'])
        return (True, [m['text_signature'] for m in results])
    except JSONDecodeError:
        return (False, None)

def getFunction(hash, sign):
    if not sign:
        cprint(f'No match found for hash {hash}', 'red')
        return None
    if len(sign) > 2:
        print(f'Multiple matches found for hash {hash}:', ', '.join(sign))
    return sign[0]

def getAbiForFunc(sign):
    name, sign = sign[0].split('(', 1)
    args = sign[:-1].split(',')
    if args == ['']:
        args = []
    return {
        "type": "function",
        "name": name,
        "inputs": [{"type": t} for t in args],
        "outputs": [{"type": "unknown"}],
    }

def decodeABI(rpc, address):
    w3 = Web3(Web3.HTTPProvider(rpc))

    bytecode = w3.eth.get_code(Web3.toChecksumAddress(address))
    hashes = getHashes(bytecode)

    signatures = {}

    cprint('Decoding hashes...', 'cyan')
    for hash in tqdm(hashes):
        (status, signature_for_hash) = getSignature(hash)
        while not status:
            sleep(1)
            (status, signature_for_hash) = getSignature(hash)
        signatures[hash] = signature_for_hash

    abi = []
    functions = []
    for hash, sign in signatures.items():
        func = getFunction(hash, sign)
        if not func: continue
        functions.append(func)
        abi.append(getAbiForFunc(sign))
    
    cprint('Initialized interface with functions:', 'green')
    for func in sorted(functions):
        print('   ', func)
    
    cprint('\nABI for contract:', 'green')
    print(abi)