bitcoinjs-lib/src/payments/bip341.js

Client-side Bitcoin JavaScript library

'use strict';
Object.defineProperty(exports, '__esModule', { value: true });
exports.tweakKey =
  exports.tapTweakHash =
  exports.tapleafHash =
  exports.findScriptPath =
  exports.toHashTree =
  exports.rootHashFromPath =
  exports.MAX_TAPTREE_DEPTH =
  exports.LEAF_VERSION_TAPSCRIPT =
    void 0;
const buffer_1 = require('buffer');
const ecc_lib_1 = require('../ecc_lib');
const bcrypto = require('../crypto');
const bufferutils_1 = require('../bufferutils');
const types_1 = require('../types');
exports.LEAF_VERSION_TAPSCRIPT = 0xc0;
exports.MAX_TAPTREE_DEPTH = 128;
const isHashBranch = ht => 'left' in ht && 'right' in ht;
/**
 * Calculates the root hash from a given control block and leaf hash.
 * @param controlBlock - The control block buffer.
 * @param leafHash - The leaf hash buffer.
 * @returns The root hash buffer.
 * @throws {TypeError} If the control block length is less than 33.
 */
function rootHashFromPath(controlBlock, leafHash) {
  if (controlBlock.length < 33)
    throw new TypeError(
      `The control-block length is too small. Got ${controlBlock.length}, expected min 33.`,
    );
  const m = (controlBlock.length - 33) / 32;
  let kj = leafHash;
  for (let j = 0; j < m; j++) {
    const ej = controlBlock.slice(33 + 32 * j, 65 + 32 * j);
    if (kj.compare(ej) < 0) {
      kj = tapBranchHash(kj, ej);
    } else {
      kj = tapBranchHash(ej, kj);
    }
  }
  return kj;
}
exports.rootHashFromPath = rootHashFromPath;
/**
 * Build a hash tree of merkle nodes from the scripts binary tree.
 * @param scriptTree - the tree of scripts to pairwise hash.
 */
function toHashTree(scriptTree) {
  if ((0, types_1.isTapleaf)(scriptTree))
    return { hash: tapleafHash(scriptTree) };
  const hashes = [toHashTree(scriptTree[0]), toHashTree(scriptTree[1])];
  hashes.sort((a, b) => a.hash.compare(b.hash));
  const [left, right] = hashes;
  return {
    hash: tapBranchHash(left.hash, right.hash),
    left,
    right,
  };
}
exports.toHashTree = toHashTree;
/**
 * Given a HashTree, finds the path from a particular hash to the root.
 * @param node - the root of the tree
 * @param hash - the hash to search for
 * @returns - array of sibling hashes, from leaf (inclusive) to root
 * (exclusive) needed to prove inclusion of the specified hash. undefined if no
 * path is found
 */
function findScriptPath(node, hash) {
  if (isHashBranch(node)) {
    const leftPath = findScriptPath(node.left, hash);
    if (leftPath !== undefined) return [...leftPath, node.right.hash];
    const rightPath = findScriptPath(node.right, hash);
    if (rightPath !== undefined) return [...rightPath, node.left.hash];
  } else if (node.hash.equals(hash)) {
    return [];
  }
  return undefined;
}
exports.findScriptPath = findScriptPath;
function tapleafHash(leaf) {
  const version = leaf.version || exports.LEAF_VERSION_TAPSCRIPT;
  return bcrypto.taggedHash(
    'TapLeaf',
    buffer_1.Buffer.concat([
      buffer_1.Buffer.from([version]),
      serializeScript(leaf.output),
    ]),
  );
}
exports.tapleafHash = tapleafHash;
function tapTweakHash(pubKey, h) {
  return bcrypto.taggedHash(
    'TapTweak',
    buffer_1.Buffer.concat(h ? [pubKey, h] : [pubKey]),
  );
}
exports.tapTweakHash = tapTweakHash;
function tweakKey(pubKey, h) {
  if (!buffer_1.Buffer.isBuffer(pubKey)) return null;
  if (pubKey.length !== 32) return null;
  if (h && h.length !== 32) return null;
  const tweakHash = tapTweakHash(pubKey, h);
  const res = (0, ecc_lib_1.getEccLib)().xOnlyPointAddTweak(pubKey, tweakHash);
  if (!res || res.xOnlyPubkey === null) return null;
  return {
    parity: res.parity,
    x: buffer_1.Buffer.from(res.xOnlyPubkey),
  };
}
exports.tweakKey = tweakKey;
function tapBranchHash(a, b) {
  return bcrypto.taggedHash('TapBranch', buffer_1.Buffer.concat([a, b]));
}
function serializeScript(s) {
  const varintLen = bufferutils_1.varuint.encodingLength(s.length);
  const buffer = buffer_1.Buffer.allocUnsafe(varintLen); // better
  bufferutils_1.varuint.encode(s.length, buffer);
  return buffer_1.Buffer.concat([buffer, s]);
}