Guess an ABI from an Ethereum contract address, even if it's unverified.
We parse EVM bytecode to find 4-byte JUMPI instructions and confirm that
they're valid internal JUMPDEST targets.
By getting the 4-byte function signature hash selectors, we can use them to call functions on unverified contracts that were compiled using bytecode layout techniques similar to Solidity.
We can also look up the 4-byte selectors on APIs like 4byte.directory to discover possible original function signatures.
import { ethers } from "ethers";
import { whatsabi } from "@shazow/whatsabi";
const provider = new ethers.getDefaultProvider(); // substitute with your fav provider
const address = "0x00000000006c3852cbEf3e08E8dF289169EdE581"; // Or your fav contract address
const code = await provider.getCode(address); // Load the bytecode
// Get just the callable selectors
const selectors = whatsabi.selectorsFromBytecode(code);
console.log(selectors); // -> ["0x06fdde03", "0x46423aa7", "0x55944a42", ...]
// Get an ABI-like list of interfaces
const abi = whatsabi.abiFromBytecode(code);
console.log(abi);
// -> [
// {"type": "event", "hash": "0x721c20121297512b72821b97f5326877ea8ecf4bb9948fea5bfcb6453074d37f"},
// {"type": "function", "payable": true, "selector": "0x06fdde03"},
// {"type": "function", "payable": true, "selector": "0x46423aa7"},
// ...
// We also have a suite of database loaders for convenience
const signatureLookup = new whatsabi.loaders.SamczunSignatureLookup();
console.log(await signatureLookup.loadFunctions("0x06fdde03"));
// -> ["name()"]);
console.log(await signatureLookup.loadFunctions("0x46423aa7"));
// -> ["getOrderStatus(bytes32)"]);
// We also have event loaders!
console.log(await signatureLookup.loadEvents("0x721c20121297512b72821b97f5326877ea8ecf4bb9948fea5bfcb6453074d37f");
// -> ["CounterIncremented(uint256,address)"]
// There are more fancy loaders in whatsabi.loaders.*, take a look!- abi.w1nt3r.xyz - A frontend for whatsabi by @w1nt3r_eth - github.com/w1nt3r-eth/abi.w1nt3r.xyz
- Event parsing is janky, haven't found a reliable pattern so assume it's best effort. Feel free to open an issue with good failure examples, especially false negatives.
- This technique of parsing function selectors from the EVM bytecode only works if the bytecode layout is similar to how Solidity compiles it. It's possible to write assembly/bytecode that does not conform to this layout, which will fail to detect function selectors. Note that functions are not a native thing in the EVM, but rather it's an abstraction layer built on top of it by compilers.
- This library does not try to guess the function arguments, if any. That would be a cool addition in the future!
$ cat .env
export INFURA_API_KEY="..."
export ETHERSCAN_API_KEY="..."
$ nix develop # Or use your system's package manager to install node/ts/etc
[dev] $ npm install
[dev] $ ONLINE=1 make test- ethers.js for being excellent, and having a helpful assembler sub-package was inspiring.
- @jacobdehart for the library name and logo that is totally a wasabi and not a green poop!
MIT