Fix: Taproot signature validation was incorrect again.

Output keys are not guaranteed to be tweaked against their pubkey's hash.
That is only a convention decided upon for NUMS properties.

Author: junderw

src/psbt.js

@@ -1283,8 +1283,10 @@ function getHashForSig(inputIndex, input, cache, forValidate, sighashTypes) {
 function getAllTaprootHashesForSig(inputIndex, input, inputs, cache) {
   const allPublicKeys = [];
   if (input.tapInternalKey) {
-    const outputKey = (0, bip371_1.tweakInternalPubKey)(inputIndex, input);
-    allPublicKeys.push(outputKey);
+    const key = getPrevoutTaprootKey(inputIndex, input, cache);
+    if (key) {
+      allPublicKeys.push(key);
+    }
   }
   if (input.tapScriptSig) {
     const tapScriptPubkeys = input.tapScriptSig.map(tss => tss.pubkey);
@@ -1295,8 +1297,12 @@ function getAllTaprootHashesForSig(inputIndex, input, inputs, cache) {
   );
   return allHashes.flat();
 }
+function getPrevoutTaprootKey(inputIndex, input, cache) {
+  const { script } = getScriptAndAmountFromUtxo(inputIndex, input, cache);
+  return (0, psbtutils_1.isP2TR)(script) ? script.subarray(2, 34) : null;
+}
 function trimTaprootSig(signature) {
-  return signature.length === 64 ? signature : signature.subarray(1);
+  return signature.length === 64 ? signature : signature.subarray(0, 64);
 }
 function getTaprootHashesForSig(
   inputIndex,
@@ -1318,7 +1324,8 @@ function getTaprootHashesForSig(
   const values = prevOuts.map(o => o.value);
   const hashes = [];
   if (input.tapInternalKey && !tapLeafHashToSign) {
-    const outputKey = (0, bip371_1.tweakInternalPubKey)(inputIndex, input);
+    const outputKey =
+      getPrevoutTaprootKey(inputIndex, input, cache) || Buffer.from([]);
     if ((0, bip371_1.toXOnly)(pubkey).equals(outputKey)) {
       const tapKeyHash = unsignedTx.hashForWitnessV1(
         inputIndex,

test/fixtures/psbt.json

@@ -310,7 +310,7 @@
       },
       {
         "description": "Sign PSBT with 3 inputs [P2PKH, P2TR (key-path), P2WPKH] and two outputs [P2TR, P2WPKH]",
-        "psbt": "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",
+        "psbt": "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",
         "isTaproot": true,
         "keys": [
           {
@@ -326,7 +326,7 @@
             "WIF": "cPPRdCmAMZMjPdHfRmTCmzYVruZHJ8GbM1FqN2W6DnmEPWDg29aL"
           }
         ],
-        "result": "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"
+        "result": "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"
       },
       {
         "description": "Sign PSBT with 1 input [P2TR] (script-path, 3-of-3) and one output [P2TR]",
@@ -896,7 +896,7 @@
     "nonExistantIndex": 42
   },
   "validateSignaturesOfTapKeyInput": {
-    "psbt": "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",
+    "psbt": "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",
     "index": 1,
     "pubkey": "Buffer.from('024fef5c5163bea69a93e74a59672bbeb081837077cb94cfa6e481a5cf00d8ab18', 'hex')",
     "incorrectPubkey": "Buffer.from('029583bf39ae0a609747ad199addd634fa6108559d6c5cd39b4c2183f1ab96e02a', 'hex')"

test/integration/taproot.spec.ts

@@ -629,6 +629,35 @@ describe('bitcoinjs-lib (transaction with taproot)', () => {
       'Should fail validation',
     );
   });
+
+  it('should succeed validating valid signatures for taproot (See issue #1934)', () => {
+    const schnorrValidator = (
+      pubkey: Buffer,
+      msghash: Buffer,
+      signature: Buffer,
+    ) => {
+      return ecc.verifySchnorr(msghash, pubkey, signature);
+    };
+
+    const psbtBase64 =
+      `cHNidP8BAF4CAAAAAU6UzYPa7tES0HoS+obnRJuXX41Ob64Zs59qDEyKsu1ZAAAAAAD/////AYA
+      zAjsAAAAAIlEgIlIzfR+flIWYTyewD9v+1N84IubZ/7qg6oHlYLzv1aYAAAAAAAEAXgEAAAAB8f+
+      afEJBun7sRQLFE1Olc/gK9LBaduUpz3vB4fjXVF0AAAAAAP3///8BECcAAAAAAAAiUSAiUjN9H5+
+      UhZhPJ7AP2/7U3zgi5tn/uqDqgeVgvO/VpgAAAAABASsQJwAAAAAAACJRICJSM30fn5SFmE8nsA/
+      b/tTfOCLm2f+6oOqB5WC879WmAQMEgwAAAAETQWQwNOao3RMOBWPuAQ9Iph7Qzk47MvroTHbJR49
+      MxKJmQ6hfhZa5wVVrdKYea5BW/loqa7al2pYYZMlGvdS06wODARcgjuYXxIpyOMVTYEvl35gDidC
+      m/vUICZyuNNZKaPz9dxAAAQUgjuYXxIpyOMVTYEvl35gDidCm/vUICZyuNNZKaPz9dxAA`.replace(
+        /\s+/g,
+        '',
+      );
+
+    const psbt = bitcoin.Psbt.fromBase64(psbtBase64);
+
+    assert(
+      psbt.validateSignaturesOfAllInputs(schnorrValidator),
+      'Should succeed validation',
+    );
+  });
 });
 
 function buildLeafIndexFinalizer(

ts_src/psbt.ts

@@ -29,7 +29,6 @@ import {
   isTaprootInput,
   checkTaprootInputFields,
   checkTaprootOutputFields,
-  tweakInternalPubKey,
   checkTaprootInputForSigs,
 } from './psbt/bip371';
 import {
@@ -42,6 +41,7 @@ import {
   isP2WPKH,
   isP2WSHScript,
   isP2SHScript,
+  isP2TR,
 } from './psbt/psbtutils';
 
 export interface TransactionInput {
@@ -1701,8 +1701,10 @@ function getAllTaprootHashesForSig(
 ): { pubkey: Buffer; hash: Buffer; leafHash?: Buffer }[] {
   const allPublicKeys = [];
   if (input.tapInternalKey) {
-    const outputKey = tweakInternalPubKey(inputIndex, input);
-    allPublicKeys.push(outputKey);
+    const key = getPrevoutTaprootKey(inputIndex, input, cache);
+    if (key) {
+      allPublicKeys.push(key);
+    }
   }
 
   if (input.tapScriptSig) {
@@ -1717,8 +1719,17 @@ function getAllTaprootHashesForSig(
   return allHashes.flat();
 }
 
+function getPrevoutTaprootKey(
+  inputIndex: number,
+  input: PsbtInput,
+  cache: PsbtCache,
+): Buffer | null {
+  const { script } = getScriptAndAmountFromUtxo(inputIndex, input, cache);
+  return isP2TR(script) ? script.subarray(2, 34) : null;
+}
+
 function trimTaprootSig(signature: Buffer): Buffer {
-  return signature.length === 64 ? signature : signature.subarray(1);
+  return signature.length === 64 ? signature : signature.subarray(0, 64);
 }
 
 function getTaprootHashesForSig(
@@ -1743,7 +1754,8 @@ function getTaprootHashesForSig(
 
   const hashes = [];
   if (input.tapInternalKey && !tapLeafHashToSign) {
-    const outputKey = tweakInternalPubKey(inputIndex, input);
+    const outputKey =
+      getPrevoutTaprootKey(inputIndex, input, cache) || Buffer.from([]);
     if (toXOnly(pubkey).equals(outputKey)) {
       const tapKeyHash = unsignedTx.hashForWitnessV1(
         inputIndex,