feat(utxo-core): add bip322 proof checker

BTC-2408

TICKET: BTC-2408

Author: davidkaplanbitgo

modules/utxo-core/src/bip322/utils.ts

@@ -33,3 +33,47 @@ export function getBip322ProofMessageAtIndex(psbt: utxolib.Psbt, inputIndex: num
   }
   return Buffer.from(proprietaryKeyVals[0].value);
 }
+
+/**
+ * checks if the transaction contains a BIP322 proof
+ * does not check if the proof is valid
+ * Source: https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki#user-content-Full
+ * @params tx The transaction or the PSBT to check
+ * @returns boolean
+ */
+export function isBip322ProofCheck(tx: utxolib.bitgo.UtxoPsbt | utxolib.bitgo.UtxoTransaction<bigint>): boolean {
+  if (tx instanceof utxolib.bitgo.UtxoPsbt) {
+    if (tx.version !== 0 || tx.locktime !== 0 || tx.data.outputs.length !== 1) {
+      return false;
+    }
+    const output = tx.txOutputs[0];
+    if (output.script.toString('hex') !== '6a' || output.value !== 0n) {
+      return false;
+    }
+
+    // Return true if there is a message encoded in every input in the proprietary field
+    return tx.data.inputs.every((input, index) => getBip322ProofMessageAtIndex(tx, index) !== undefined);
+  } else if (tx instanceof utxolib.bitgo.UtxoTransaction) {
+    if (tx.version !== 0 || tx.locktime !== 0 || tx.outs.length !== 1) {
+      return false;
+    }
+    if (tx.outs.length !== 1) {
+      return false;
+    }
+    const output = tx.outs[0];
+    // check that the only output is an OP_RETURN with 0 value
+    if (output.script.toString('hex') !== '6a' || output.value !== 0n) {
+      return false;
+    }
+
+    for (const input of tx.ins) {
+      if (input.index !== 0 || input.sequence !== 0) {
+        return false;
+      }
+    }
+
+    return true;
+  } else {
+    throw new Error('Unsupported transaction type for BIP322 proof check');
+  }
+}

modules/utxo-core/test/bip322/utils.ts

@@ -2,7 +2,7 @@ import assert from 'assert';
 
 import * as utxolib from '@bitgo/utxo-lib';
 
-import { getBip322ProofMessageAtIndex } from '../../src/bip322';
+import { getBip322ProofMessageAtIndex, isBip322ProofCheck } from '../../src/bip322';
 
 import { BIP322_FIXTURE_HELLO_WORLD_TOSIGN_PSBT } from './bip322.utils';
 
@@ -35,4 +35,50 @@ describe('BIP322 Proof utils', function () {
     assert.ok(messageBuffer, 'Message buffer should not be undefined');
     assert.deepStrictEqual(messageBuffer.toString('utf-8'), 'Hello World', 'Message does not match expected value');
   });
+
+  describe('isBip322ProofCheck', function () {
+    it('should work for PSBTs', function () {
+      const psbt = utxolib.bitgo.createPsbtFromBuffer(
+        BIP322_FIXTURE_HELLO_WORLD_TOSIGN_PSBT.toBuffer(),
+        utxolib.networks.bitcoin
+      );
+      assert.ok(isBip322ProofCheck(psbt), 'Expected PSBT to be a valid BIP322 proof');
+      assert.deepEqual(
+        isBip322ProofCheck(
+          utxolib.testutil.constructPsbt(
+            [{ scriptType: 'taprootKeyPathSpend', value: BigInt(1000) }],
+            [{ scriptType: 'p2sh', value: BigInt(900) }],
+            utxolib.networks.bitcoin,
+            utxolib.testutil.getDefaultWalletKeys(),
+            'unsigned'
+          )
+        ),
+        false
+      );
+    });
+
+    it('should work for Transactions', function () {
+      const psbt = utxolib.bitgo.createPsbtFromBuffer(
+        BIP322_FIXTURE_HELLO_WORLD_TOSIGN_PSBT.toBuffer(),
+        utxolib.networks.bitcoin
+      );
+      // Cannot extract the transaction because it has no signatures
+      const tx = psbt.getUnsignedTx();
+      assert.ok(isBip322ProofCheck(tx), 'Expected Transaction to be a valid BIP322 proof');
+      assert.deepEqual(
+        isBip322ProofCheck(
+          utxolib.testutil
+            .constructPsbt(
+              [{ scriptType: 'taprootKeyPathSpend', value: BigInt(1000) }],
+              [{ scriptType: 'p2sh', value: BigInt(900) }],
+              utxolib.networks.bitcoin,
+              utxolib.testutil.getDefaultWalletKeys(),
+              'unsigned'
+            )
+            .getUnsignedTx()
+        ),
+        false
+      );
+    });
+  });
 });