Merge pull request #1491 from bitcoinjs/finalizerCallback

Allow custom implementations of finalizers

Author: d-yokoi

src/psbt.js

@@ -226,22 +226,19 @@ class Psbt {
     range(this.data.inputs.length).forEach(idx => this.finalizeInput(idx));
     return this;
   }
-  finalizeInput(inputIndex) {
+  finalizeInput(inputIndex, finalScriptsFunc = getFinalScripts) {
     const input = utils_1.checkForInput(this.data.inputs, inputIndex);
     const { script, isP2SH, isP2WSH, isSegwit } = getScriptFromInput(
       inputIndex,
       input,
       this.__CACHE,
     );
     if (!script) throw new Error(`No script found for input #${inputIndex}`);
-    const scriptType = classifyScript(script);
-    if (!canFinalize(input, script, scriptType))
-      throw new Error(`Can not finalize input #${inputIndex}`);
     checkPartialSigSighashes(input);
-    const { finalScriptSig, finalScriptWitness } = getFinalScripts(
+    const { finalScriptSig, finalScriptWitness } = finalScriptsFunc(
+      inputIndex,
+      input,
       script,
-      scriptType,
-      input.partialSig,
       isSegwit,
       isP2SH,
       isP2WSH,
@@ -772,7 +769,20 @@ function getTxCacheValue(key, name, inputs, c) {
   if (key === '__FEE_RATE') return c.__FEE_RATE;
   else if (key === '__FEE') return c.__FEE;
 }
-function getFinalScripts(
+function getFinalScripts(inputIndex, input, script, isSegwit, isP2SH, isP2WSH) {
+  const scriptType = classifyScript(script);
+  if (!canFinalize(input, script, scriptType))
+    throw new Error(`Can not finalize input #${inputIndex}`);
+  return prepareFinalScripts(
+    script,
+    scriptType,
+    input.partialSig,
+    isSegwit,
+    isP2SH,
+    isP2WSH,
+  );
+}
+function prepareFinalScripts(
   script,
   scriptType,
   partialSig,

test/integration/csv.spec.ts

@@ -1,9 +1,11 @@
 import * as assert from 'assert';
+import { PsbtInput } from 'bip174/src/lib/interfaces';
 import { before, describe, it } from 'mocha';
 import * as bitcoin from '../..';
 import { regtestUtils } from './_regtest';
 const regtest = regtestUtils.network;
 const bip68 = require('bip68');
+const varuint = require('varuint-bitcoin');
 
 function toOutputScript(address: string): Buffer {
   return bitcoin.address.toOutputScript(address, regtest);
@@ -129,33 +131,28 @@ describe('bitcoinjs-lib (transactions w/ CSV)', () => {
 
       // fund the P2SH(CSV) address
       const unspent = await regtestUtils.faucet(p2sh.address!, 1e5);
-
-      const tx = new bitcoin.Transaction();
-      tx.version = 2;
-      tx.addInput(idToHash(unspent.txId), unspent.vout, sequence);
-      tx.addOutput(toOutputScript(regtestUtils.RANDOM_ADDRESS), 7e4);
-
-      // {Alice's signature} OP_TRUE
-      const signatureHash = tx.hashForSignature(
-        0,
-        p2sh.redeem!.output!,
-        hashType,
-      );
-      const redeemScriptSig = bitcoin.payments.p2sh({
-        network: regtest,
-        redeem: {
-          network: regtest,
-          output: p2sh.redeem!.output,
-          input: bitcoin.script.compile([
-            bitcoin.script.signature.encode(
-              alice.sign(signatureHash),
-              hashType,
-            ),
-            bitcoin.opcodes.OP_TRUE,
-          ]),
-        },
-      }).input;
-      tx.setInputScript(0, redeemScriptSig!);
+      const utx = await regtestUtils.fetch(unspent.txId);
+      // for non segwit inputs, you must pass the full transaction buffer
+      const nonWitnessUtxo = Buffer.from(utx.txHex, 'hex');
+
+      // This is an example of using the finalizeInput second parameter to
+      // define how you finalize the inputs, allowing for any type of script.
+      const tx = new bitcoin.Psbt({ network: regtest })
+        .setVersion(2)
+        .addInput({
+          hash: unspent.txId,
+          index: unspent.vout,
+          sequence,
+          redeemScript: p2sh.redeem!.output!,
+          nonWitnessUtxo,
+        })
+        .addOutput({
+          address: regtestUtils.RANDOM_ADDRESS,
+          value: 7e4,
+        })
+        .signInput(0, alice)
+        .finalizeInput(0, csvGetFinalScripts) // See csvGetFinalScripts below
+        .extractTransaction();
 
       // TODO: test that it failures _prior_ to expiry, unfortunately, race conditions when run concurrently
       // ...
@@ -430,3 +427,88 @@ describe('bitcoinjs-lib (transactions w/ CSV)', () => {
     },
   );
 });
+
+// This function is used to finalize a CSV transaction using PSBT.
+// See first test above.
+function csvGetFinalScripts(
+  inputIndex: number,
+  input: PsbtInput,
+  script: Buffer,
+  isSegwit: boolean,
+  isP2SH: boolean,
+  isP2WSH: boolean,
+): {
+  finalScriptSig: Buffer | undefined;
+  finalScriptWitness: Buffer | undefined;
+} {
+  // Step 1: Check to make sure the meaningful script matches what you expect.
+  const decompiled = bitcoin.script.decompile(script);
+  // Checking if first OP is OP_IF... should do better check in production!
+  // You may even want to check the public keys in the script against a
+  // whitelist depending on the circumstances!!!
+  // You also want to check the contents of the input to see if you have enough
+  // info to actually construct the scriptSig and Witnesses.
+  if (!decompiled || decompiled[0] !== bitcoin.opcodes.OP_IF) {
+    throw new Error(`Can not finalize input #${inputIndex}`);
+  }
+
+  // Step 2: Create final scripts
+  let payment: bitcoin.Payment = {
+    network: regtest,
+    output: script,
+    // This logic should be more strict and make sure the pubkeys in the
+    // meaningful script are the ones signing in the PSBT etc.
+    input: bitcoin.script.compile([
+      input.partialSig![0].signature,
+      bitcoin.opcodes.OP_TRUE,
+    ]),
+  };
+  if (isP2WSH && isSegwit)
+    payment = bitcoin.payments.p2wsh({
+      network: regtest,
+      redeem: payment,
+    });
+  if (isP2SH)
+    payment = bitcoin.payments.p2sh({
+      network: regtest,
+      redeem: payment,
+    });
+
+  function witnessStackToScriptWitness(witness: Buffer[]): Buffer {
+    let buffer = Buffer.allocUnsafe(0);
+
+    function writeSlice(slice: Buffer): void {
+      buffer = Buffer.concat([buffer, Buffer.from(slice)]);
+    }
+
+    function writeVarInt(i: number): void {
+      const currentLen = buffer.length;
+      const varintLen = varuint.encodingLength(i);
+
+      buffer = Buffer.concat([buffer, Buffer.allocUnsafe(varintLen)]);
+      varuint.encode(i, buffer, currentLen);
+    }
+
+    function writeVarSlice(slice: Buffer): void {
+      writeVarInt(slice.length);
+      writeSlice(slice);
+    }
+
+    function writeVector(vector: Buffer[]): void {
+      writeVarInt(vector.length);
+      vector.forEach(writeVarSlice);
+    }
+
+    writeVector(witness);
+
+    return buffer;
+  }
+
+  return {
+    finalScriptSig: payment.input,
+    finalScriptWitness:
+      payment.witness && payment.witness.length > 0
+        ? witnessStackToScriptWitness(payment.witness)
+        : undefined,
+  };
+}

ts_src/psbt.ts

@@ -274,7 +274,10 @@ export class Psbt {
     return this;
   }
 
-  finalizeInput(inputIndex: number): this {
+  finalizeInput(
+    inputIndex: number,
+    finalScriptsFunc: FinalScriptsFunc = getFinalScripts,
+  ): this {
     const input = checkForInput(this.data.inputs, inputIndex);
     const { script, isP2SH, isP2WSH, isSegwit } = getScriptFromInput(
       inputIndex,
@@ -283,16 +286,12 @@ export class Psbt {
     );
     if (!script) throw new Error(`No script found for input #${inputIndex}`);
 
-    const scriptType = classifyScript(script);
-    if (!canFinalize(input, script, scriptType))
-      throw new Error(`Can not finalize input #${inputIndex}`);
-
     checkPartialSigSighashes(input);
 
-    const { finalScriptSig, finalScriptWitness } = getFinalScripts(
+    const { finalScriptSig, finalScriptWitness } = finalScriptsFunc(
+      inputIndex,
+      input,
       script,
-      scriptType,
-      input.partialSig!,
       isSegwit,
       isP2SH,
       isP2WSH,
@@ -991,7 +990,49 @@ function getTxCacheValue(
   else if (key === '__FEE') return c.__FEE!;
 }
 
+/**
+ * This function must do two things:
+ * 1. Check if the `input` can be finalized. If it can not be finalized, throw.
+ *   ie. `Can not finalize input #${inputIndex}`
+ * 2. Create the finalScriptSig and finalScriptWitness Buffers.
+ */
+type FinalScriptsFunc = (
+  inputIndex: number, // Which input is it?
+  input: PsbtInput, // The PSBT input contents
+  script: Buffer, // The "meaningful" locking script Buffer (redeemScript for P2SH etc.)
+  isSegwit: boolean, // Is it segwit?
+  isP2SH: boolean, // Is it P2SH?
+  isP2WSH: boolean, // Is it P2WSH?
+) => {
+  finalScriptSig: Buffer | undefined;
+  finalScriptWitness: Buffer | undefined;
+};
+
 function getFinalScripts(
+  inputIndex: number,
+  input: PsbtInput,
+  script: Buffer,
+  isSegwit: boolean,
+  isP2SH: boolean,
+  isP2WSH: boolean,
+): {
+  finalScriptSig: Buffer | undefined;
+  finalScriptWitness: Buffer | undefined;
+} {
+  const scriptType = classifyScript(script);
+  if (!canFinalize(input, script, scriptType))
+    throw new Error(`Can not finalize input #${inputIndex}`);
+  return prepareFinalScripts(
+    script,
+    scriptType,
+    input.partialSig!,
+    isSegwit,
+    isP2SH,
+    isP2WSH,
+  );
+}
+
+function prepareFinalScripts(
   script: Buffer,
   scriptType: string,
   partialSig: PartialSig[],

types/psbt.d.ts

@@ -58,7 +58,7 @@ export declare class Psbt {
     getFeeRate(): number;
     getFee(): number;
     finalizeAllInputs(): this;
-    finalizeInput(inputIndex: number): this;
+    finalizeInput(inputIndex: number, finalScriptsFunc?: FinalScriptsFunc): this;
     validateSignaturesOfAllInputs(): boolean;
     validateSignaturesOfInput(inputIndex: number, pubkey?: Buffer): boolean;
     signAllInputsHD(hdKeyPair: HDSigner, sighashTypes?: number[]): this;
@@ -124,4 +124,19 @@ interface HDSignerAsync extends HDSignerBase {
     derivePath(path: string): HDSignerAsync;
     sign(hash: Buffer): Promise<Buffer>;
 }
+/**
+ * This function must do two things:
+ * 1. Check if the `input` can be finalized. If it can not be finalized, throw.
+ *   ie. `Can not finalize input #${inputIndex}`
+ * 2. Create the finalScriptSig and finalScriptWitness Buffers.
+ */
+declare type FinalScriptsFunc = (inputIndex: number, // Which input is it?
+input: PsbtInput, // The PSBT input contents
+script: Buffer, // The "meaningful" locking script Buffer (redeemScript for P2SH etc.)
+isSegwit: boolean, // Is it segwit?
+isP2SH: boolean, // Is it P2SH?
+isP2WSH: boolean) => {
+    finalScriptSig: Buffer | undefined;
+    finalScriptWitness: Buffer | undefined;
+};
 export {};