multichain-address-validator/src/validators/polkadot_validator.ts

Multichain address validator for Bitcoin and other blockchains.

import cryptoUtils from '../crypto/utils.js'
import {Address} from '../types.js'
import {getAddress} from '../helpers.js'

// from https://github.com/paritytech/substrate/wiki/External-Address-Format-(SS58)
const addressFormats = [
    {addressLength: 3, accountIndexLength: 1, checkSumLength: 1},
    {addressLength: 4, accountIndexLength: 2, checkSumLength: 1},
    {addressLength: 5, accountIndexLength: 2, checkSumLength: 2},
    {addressLength: 6, accountIndexLength: 4, checkSumLength: 1},
    {addressLength: 7, accountIndexLength: 4, checkSumLength: 2},
    {addressLength: 8, accountIndexLength: 4, checkSumLength: 3},
    {addressLength: 9, accountIndexLength: 4, checkSumLength: 4},
    {addressLength: 10, accountIndexLength: 8, checkSumLength: 1},
    {addressLength: 11, accountIndexLength: 8, checkSumLength: 2},
    {addressLength: 12, accountIndexLength: 8, checkSumLength: 3},
    {addressLength: 13, accountIndexLength: 8, checkSumLength: 4},
    {addressLength: 14, accountIndexLength: 8, checkSumLength: 5},
    {addressLength: 15, accountIndexLength: 8, checkSumLength: 6},
    {addressLength: 16, accountIndexLength: 8, checkSumLength: 7},
    {addressLength: 17, accountIndexLength: 8, checkSumLength: 8},
    {addressLength: 34, accountIndexLength: 32, checkSumLength: 2},
];

function verifyChecksum(address: string) {
    try {
        const preImage = '53533538505245'
        const decoded = cryptoUtils.base58(address);
        const addressType = cryptoUtils.byteArray2hexStr(decoded.slice(0, 1));
        const addressAndChecksum = decoded.slice(1)

        // get the address format
        const addressFormat = addressFormats.find(af => af.addressLength === addressAndChecksum.length);

        if (!addressFormat) {
            throw new Error('Invalid address length');
        }

        const decodedAddress = cryptoUtils.byteArray2hexStr(addressAndChecksum.slice(0, addressFormat.accountIndexLength));
        const checksum = cryptoUtils.byteArray2hexStr(addressAndChecksum.slice(-addressFormat.checkSumLength));

        const calculatedHash = cryptoUtils
            .blake2b(preImage + addressType + decodedAddress, 64)
            .substr(0, addressFormat.checkSumLength * 2)
            .toUpperCase();

        return calculatedHash == checksum;
    } catch (err) {
        return false;
    }
}

export default {
    isValidAddress(address: Address) {
        return verifyChecksum(getAddress(address))
    },
}