EVMole

EVMole is a powerful library that extracts information from Ethereum Virtual Machine (EVM) bytecode, including function selectors, arguments, and state mutability, even for unverified contracts.

Key Features

• Multi-language support: Available as JavaScript, Rust, and Python libraries.
• High accurancy and performance: Outperforms existing tools.
• Broad compatibility: Tested with both Solidity and Vyper compiled contracts.
• Lightweight: Clean codebase with minimal external dependencies.
• Unverified contract analysis: Extracts information even from unverified bytecode.

Usage

JavaScript

API documentation and usage examples (node, vite, webpack, parcel, esbuild)

$ npm i evmole

import { functionSelectors, functionArguments, functionStateMutability } from 'evmole'

const code = '0x6080604052348015600e575f80fd5b50600436106030575f3560e01c80632125b65b146034578063b69ef8a8146044575b5f80fd5b6044603f3660046046565b505050565b005b5f805f606084860312156057575f80fd5b833563ffffffff811681146069575f80fd5b925060208401356001600160a01b03811681146083575f80fd5b915060408401356001600160e01b0381168114609d575f80fd5b80915050925092509256'

console.log(functionSelectors(code));                   // [ '2125b65b', 'b69ef8a8' ]
console.log(functionArguments(code, '2125b65b'));       // 'uint32,address,uint224'
console.log(functionStateMutability(code, '2125b65b')); // 'pure'

Rust

Documentation is available on docs.rs

let code = hex::decode("6080604052348015600e575f80fd5b50600436106030575f3560e01c80632125b65b146034578063b69ef8a8146044575b5f80fd5b6044603f3660046046565b505050565b005b5f805f606084860312156057575f80fd5b833563ffffffff811681146069575f80fd5b925060208401356001600160a01b03811681146083575f80fd5b915060408401356001600160e01b0381168114609d575f80fd5b80915050925092509256").unwrap();

println!("{:x?} | {} | {:?}",
    evmole::function_selectors(&code, 0),
    evmole::function_arguments(&code, &[0x21, 0x25, 0xb6, 0x5b], 0),
    evmole::function_state_mutability(&code, &[0x21, 0x25, 0xb6, 0x5b], 0),
);
// [[21, 25, b6, 5b], [b6, 9e, f8, a8]] | uint32,address,uint224 | Pure

Python

API documentation

$ pip install evmole --upgrade

from evmole import function_selectors, function_arguments, function_state_mutability

code = '0x6080604052348015600e575f80fd5b50600436106030575f3560e01c80632125b65b146034578063b69ef8a8146044575b5f80fd5b6044603f3660046046565b505050565b005b5f805f606084860312156057575f80fd5b833563ffffffff811681146069575f80fd5b925060208401356001600160a01b03811681146083575f80fd5b915060408401356001600160e01b0381168114609d575f80fd5b80915050925092509256'

print(function_selectors(code))                    # ['2125b65b', 'b69ef8a8']
print(function_arguments(code, '2125b65b'))        # uint32,address,uint224
print(function_state_mutability(code, '2125b65b')) # pure

Foundry

Foundy's cast uses the Rust implementation of EVMole

$ cast selectors $(cast code 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2)
0x06fdde03	
0x095ea7b3	address,uint256
0x18160ddd	
0x23b872dd	address,address,uint256
...

$ cast selectors --resolve $(cast code 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2)
0x06fdde03	                       	name()
0x095ea7b3	address,uint256        	approve(address,uint256)
0x18160ddd	                       	totalSupply()
0x23b872dd	address,address,uint256	transferFrom(address,address,uint256)
...

Benchmark

function selectors

FP/FN - False Positive/False Negative errors; smaller is better

Dataset		evmole rs · js · py	whatsabi	sevm	evmhound	heimdall	smpl
largest1k 1000 addresses 24427 functions	FP addrs	1 🥈	0 🥇	0 🥇	75	18	95
	FN addrs	0 🥇	0 🥇	0 🥇	40	111	9
	FP funcs	192 🥈	0 🥇	0 🥇	720	600	749
	FN funcs	0 🥇	0 🥇	0 🥇	191	147	12
	Time	0.5s · 0.7s · 0.6s	3.2s	47s(*)	0.5s	341s(*)	1.8s
random50k 50000 addresses 1171102 functions	FP addrs	1 🥇	43	1	693	3	4136
	FN addrs	9 🥇	11	10	2903	4708	77
	FP funcs	3 🥇	51	3	10798	29	14652
	FN funcs	10 🥇	12	11	3538	6098	96
	Time	4.5s · 8.5s · 7.8s	54s	2472s(*)	6.1s	8576s(*)	46s
vyper 780 addresses 21244 functions	FP addrs	0 🥇	30	0	19	0	185
	FN addrs	0 🥇	780	0	300	780	480
	FP funcs	0 🥇	30	0	19	0	197
	FN funcs	0 🥇	21244	0	8273	21244	12971
	Time	0.4s · 0.6s · 0.4s	2.4s	57s(*)	0.4s	27s(*)	1.1s

function arguments

Errors - when at least 1 argument is incorrect: (uint256,string) ≠ (uint256,bytes)

Dataset		evmole rs · js · py	heimdall	smpl
largest1k 24427 functions	Errors	14.0% 🥇 3410	31.1% 7593	58.3% 14242
	Time	1.1s · 4.8s · 1.4s	342s(*)	0.7s
random50k 1171102 functions	Errors	4.5% 🥇 52662	19.4% 227612	54.9% 643213
	Time	25s · 127 · 32	8544s(*)	9.5s
vyper 21244 functions	Errors	48.5% 🥇 10300	100.0% 21244	56.8% 12077
	Time	0.8s · 3.0s · 1.0s	28s(*)	0.6s

function state mutability

Errors - Results are not equal (treating view and pure as equivalent to nonpayable)

Errors strict - Results are strictly unequal (nonpayable ≠ view). Some ABIs mark pure/view functions as nonpayable, so not all strict errors indicate real issues.

Dataset		evmole rs · js · py	whatsabi	sevm	heimdall	smpl
largest1k 24427 functions	Errors	0.0% 🥇 0	68.1% 16623	2.1% 501	25.4% 6201	2.6% 643
	Errors strict	18.7% 🥇 4558	79.3% 19370	59.0% 14417	54.9% 13403	60.9% 14864
	Time	9.5s · 19s · 9.4s	3.8s	46s(*)	339s(*)	0.7s
random50k 1160861 functions	Errors	0.0% 🥇 35	30.2% 351060	0.3% 3370	11.6% 134195	2.2% 24961
	Errors strict	6.7% 🥇 77945	58.1% 674922	55.7% 646831	27.7% 321494	57.7% 670318
	Time	214s · 471s · 240s	85s	2335s(*)	8151s(*)	9.4s
vyper 21166 functions	Errors	0.5% 🥇 110	100.0% 21166	76.3% 16150	100.0% 21166	1.8% 390
	Errors strict	4.2% 🥇 888	100.0% 21166	90.2% 19092	100.0% 21166	59.6% 12610
	Time	10s · 15s · 10s	2.4s	52s(*)	28s(*)	0.6s

See benchmark/README.md for the methodology and commands to reproduce these results

versions: evmole v0.5.1; whatsabi v0.14.1; sevm v0.7.3; evm-hound-rs v0.1.4; heimdall-rs v0.8.4

^(*): sevm and heimdall-rs are full decompilers, not limited to extracting function selectors

How it works

Short: Executes code with a custom EVM and traces CALLDATA usage.

Long: TODO

License

MIT