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/* eslint-disable @typescript-eslint/no-unsafe-member-access */
/* eslint-disable @typescript-eslint/no-unsafe-assignment */
import { BufferReader } from "@node-lightning/bufio";
import bech32 from "bech32";
import { ADDRESS_VERSION } from "./address-version";
import * as crypto from "./crypto";
import { FIELD_TYPE } from "./field-type";
import { hrpToPico } from "./hrp-pico";
import { Invoice } from "./invoice";
import { WordCursor } from "./word-cursor";
/**
* Decodes an invoice into an Invoice object
* @param invoice
* @return
*/
export function decode(invoice: string): Invoice {
// Decode the invoice into prefix and words.
// The words will be interated over to decode the rest of thee invoice
const { prefix, words } = bech32.decode(invoice, Number.MAX_SAFE_INTEGER);
// Parse the prefix into the network and the value in pico bitcoin.
const { network, picoBtc } = parsePrefix(prefix);
// Construct a word cursor to read from the remaining data
const wordcursor = new WordCursor(words);
const timestamp = wordcursor.readUIntBE(7); // read 7 words / 35 bits
const fields = [];
const unknownFields = [];
// read fields until at signature
while (wordcursor.wordsRemaining > 104) {
const type = wordcursor.readUIntBE(1); // read 1 word / 5 bits
const len = wordcursor.readUIntBE(2); // read 2 words / 10 bits
let value;
switch (type) {
case 0:
continue; // read off padding
case FIELD_TYPE.PAYMENT_HASH: // p - 256-bit sha256 payment_hash
value = wordcursor.readBytes(len);
// push non-standard length field into unknown fields
if (len !== 52) {
unknownFields.push({ type, value });
continue;
}
break;
case FIELD_TYPE.ROUTE: // r - variable, one or more entries containing extra routing info
{
value = [];
const bytes = wordcursor.readBytes(len);
const bytecursor = new BufferReader(bytes);
while (!bytecursor.eof) {
value.push({
pubkey: bytecursor.readBytes(33),
short_channel_id: bytecursor.readBytes(8),
fee_base_msat: bytecursor.readUInt32BE(),
fee_proportional_millionths: bytecursor.readUInt32BE(),
cltv_expiry_delta: bytecursor.readUInt16BE(),
});
}
}
break;
case FIELD_TYPE.EXPIRY: // x - expiry time in seconds
value = wordcursor.readUIntBE(len);
break;
case FIELD_TYPE.FALLBACK_ADDRESS: // f - variable depending on version
{
const version = wordcursor.readUIntBE(1);
const address = wordcursor.readBytes(len - 1);
value = {
version,
address,
};
if (
version !== ADDRESS_VERSION.SEGWIT &&
version !== ADDRESS_VERSION.P2PKH &&
version !== ADDRESS_VERSION.P2SH
) {
unknownFields.push({ type, value });
continue;
}
}
break;
case FIELD_TYPE.SHORT_DESC: // d - short description of purpose of payment utf-8
value = wordcursor.readBytes(len).toString("utf8");
break;
case FIELD_TYPE.PAYEE_NODE: // n - 33-byte public key of the payee node
value = wordcursor.readBytes(len);
if (len !== 53) {
unknownFields.push({ type, value });
continue;
}
break;
case FIELD_TYPE.HASH_DESC: // h - 256-bit sha256 description of purpose of payment
value = wordcursor.readBytes(len);
if (len !== 52) {
unknownFields.push({ type, value });
continue;
}
break;
case FIELD_TYPE.MIN_FINAL_CLTV_EXPIRY: // c - min_final_cltv_expiry to use for the last HTLC in the route
value = wordcursor.readUIntBE(len);
break;
default:
value = wordcursor.readBytes(len);
unknownFields.push({ type, value });
continue;
}
fields.push({ type, value });
}
const sigBytes = wordcursor.readBytes(103); // read 512-bit sig
const r = sigBytes.slice(0, 32);
const s = sigBytes.slice(32);
const recoveryFlag = wordcursor.readUIntBE(1);
wordcursor.position = 0;
let preHashData = wordcursor.readBytes(words.length - 104, true);
preHashData = Buffer.concat([Buffer.from(prefix), preHashData]);
const hashData = crypto.sha256(preHashData);
// extract the pubkey for verifying the signature by either:
// 1: using the payee field value (n)
// 2: performing signature recovery
const payeeNodeField = fields.find(p => p.type === FIELD_TYPE.PAYEE_NODE);
const pubkey = payeeNodeField
? payeeNodeField.value // use payee node provided
: crypto.ecdsaRecovery(hashData, sigBytes, recoveryFlag); // recovery pubkey from ecdsa sig
// validate signature
// note if we performed signature recovery this will always match
// so we may want to just skip this if we had signature recovery
if (!crypto.ecdsaVerify(pubkey, hashData, sigBytes)) throw new Error("Signature invalid");
// constuct the invoice
const result = new Invoice();
result._value = picoBtc; // directly assign pico value since there is not setter
result.network = network;
result.timestamp = timestamp;
result.fields = fields;
result.unknownFields = unknownFields;
result.signature = { r, s, recoveryFlag };
result.pubkey = pubkey;
result.hashData = hashData;
result.usedSigRecovery = !!payeeNodeField;
return result;
}
//////////////
/**
* Parses the prefix into network and value and then performs
* validations on the values.
*
* This code is rough. Should refactor into two steps:
* 1) tokenize
* 2) parse tokens
*
* Value is returned as pico bitcoin.
*/
function parsePrefix(prefix: string): { network: string; picoBtc: bigint } {
if (!prefix.startsWith("ln")) throw new Error("Invalid prefix");
let network = "";
let tempValue = "";
let value;
let multiplier;
let hasNetwork = false;
let hasAmount = false;
for (let i = 2; i < prefix.length; i++) {
const charCode = prefix.charCodeAt(i);
if (!hasNetwork) {
if (charCode >= 97 && charCode <= 122) network += prefix[i];
else hasNetwork = true;
}
if (hasNetwork && !hasAmount) {
if (charCode >= 48 && charCode <= 57) tempValue += prefix[i];
else Eif (tempValue) hasAmount = true;
else throw new Error("Invalid amount");
}
if (hasAmount) {
if (charCode >= 97 && charCode <= 122) multiplier = prefix[i];
else throw new Error("Invalid character");
}
}
// returns null if we do not have a value
if (tempValue === "") value = null;
// otherwise we multiply by the value by the pico amount to obtain
// the actual pico value of the
else value = BigInt(tempValue) * hrpToPico(multiplier);
if (!isValidNetwork(network)) throw new Error("Invalid network");
if (!isValidValue(value)) throw new Error("Invalid amount");
return {
network,
picoBtc: value,
};
}
function isValidNetwork(network) {
return network === "bc" || network === "tb" || network === "bcrt" || network === "sb";
}
function isValidValue(value) {
return value === null || value > 0;
}
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