Method verifyProgram

lib/script/script.js:3205–3262

* Verify a witness program. This runs after regular script * execution if a witness program is present. It will convert * the witness to a stack and execute the program. * @param {Witness} witness * @param {Script} output * @param {VerifyFlags} flags * @param {TX} tx * @param {N

(witness, output, flags, tx, index, value)

   */

  static verifyProgram(witness, output, flags, tx, index, value) {
    const program = output.getProgram();

    assert(program, 'verifyProgram called on non-witness-program.');
    assert((flags & Script.flags.VERIFY_WITNESS) !== 0);

    const stack = witness.toStack();
    let redeem;

    if (program.version === 0) {
      if (program.data.length === 32) {
        if (stack.length === 0)
          throw new ScriptError('WITNESS_PROGRAM_WITNESS_EMPTY');

        const witnessScript = stack.pop();

        if (!sha256.digest(witnessScript).equals(program.data))
          throw new ScriptError('WITNESS_PROGRAM_MISMATCH');

        redeem = Script.fromRaw(witnessScript);
      } else if (program.data.length === 20) {
        if (stack.length !== 2)
          throw new ScriptError('WITNESS_PROGRAM_MISMATCH');

        redeem = Script.fromPubkeyhash(program.data);
      } else {
        // Failure on version=0 (bad program data length).
        throw new ScriptError('WITNESS_PROGRAM_WRONG_LENGTH');
      }
    } else {
      // Anyone can spend (we can return true here
      // if we want to always relay these transactions).
      // Otherwise, if we want to act like an "old"
      // implementation and only accept them in blocks,
      // we can use the regular output script which will
      // succeed in a block, but fail in the mempool
      // due to VERIFY_CLEANSTACK.
      if (flags & Script.flags.VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM)
        throw new ScriptError('DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM');
      return;
    }

    // Witnesses still have push limits.
    for (let j = 0; j < stack.length; j++) {
      if (stack.get(j).length > consensus.MAX_SCRIPT_PUSH)
        throw new ScriptError('PUSH_SIZE');
    }

    // Verify the redeem script.
    redeem.execute(stack, flags, tx, index, value, 1);

    // Verify the stack values.
    if (stack.length !== 1)
      throw new ScriptError('CLEANSTACK');

    if (!stack.getBool(-1))
      throw new ScriptError('EVAL_FALSE');
  }