refactor(utxo-core): trimMessagePrefix fix function

modules/utxo-core/src/paygo/index.ts

@@ -1,2 +1,3 @@
 export * from './parsePayGoAttestation';
 export * from './psbt';
+export * from './trimMessagePrefix';

modules/utxo-core/src/testutil/trimMessagePrefix.ts → modules/utxo-core/src/paygo/trimMessagePrefix.ts

@@ -2,24 +2,24 @@ import * as utxolib from '@bitgo/utxo-lib';
 
 /** We receive a proof in the form:
  * 0x18Bitcoin Signed Message:\n<varint_length><ENTROPY><ADDRESS><UUID>
- * and when verifying our message we want to exclude the 0x18Bitcoin Signed Message:\n<varint_length>
- * of the proof so that we are left with the entropy address and uuid as our message.
- * This is what we are going to be verifying.
+ * and trims the 0x18Bitcoin Signed Message:\n<varin_length> and returns
+ * our message <ENTROPY><ADDRESS><UUID> in a Buffer.
  *
  * @param proof
  * @returns
  */
 export function trimMessagePrefix(proof: Buffer): Buffer {
   const prefix = '\u0018Bitcoin Signed Message:\n';
+  const prefixBuffer = Buffer.from(prefix, 'utf-8');
   if (proof.toString().startsWith(prefix)) {
-    proof = proof.slice(Buffer.from(prefix).length);
+    proof = proof.slice(prefixBuffer.length);
     utxolib.bufferutils.varuint.decode(proof, 0);
     // Determines how many bytes were consumed during our last varuint.decode(Buffer, offset)
     // So if varuint.decode(0xfd) then varuint.decode.bytes = 3
     // varuint.decode(0xfe) then varuint.decode.bytes = 5, etc.
     const varintBytesLength = utxolib.bufferutils.varuint.decode.bytes;
 
-    proof.slice(varintBytesLength);
+    return proof.slice(varintBytesLength);
   }
   return proof;
 }

modules/utxo-core/src/testutil/index.ts

@@ -2,4 +2,3 @@ export * from './fixtures.utils';
 export * from './key.utils';
 export * from './toPlainObject.utils';
 export * from './generatePayGoAttestationProof.utils';
-export * from './trimMessagePrefix';

modules/utxo-core/test/paygo/psbt/payGoAddressProof.ts

@@ -13,9 +13,10 @@ import {
   verifyPayGoAddressProof,
 } from '../../../src/paygo/psbt/payGoAddressProof';
 import { generatePayGoAttestationProof } from '../../../src/testutil/generatePayGoAttestationProof.utils';
-import { trimMessagePrefix } from '../../../src/testutil/trimMessagePrefix';
+import { trimMessagePrefix } from '../../../src/paygo/trimMessagePrefix';
 import { signMessage } from '../../../src/bip32utils';
-import { NIL_UUID } from '../../../src/paygo/attestation';
+import { createPayGoAttestationBuffer, NIL_UUID } from '../../../src/paygo/attestation';
+import { parsePayGoAttestation } from '../../../src/paygo';
 
 // To construct our PSBTs
 export const network = utxolib.networks.bitcoin;
@@ -46,9 +47,11 @@ export const addressToVerify = utxolib.address.toBase58Check(
 
 // this should be retuning a Buffer
 export const addressProofBuffer = generatePayGoAttestationProof(NIL_UUID, Buffer.from(addressToVerify));
+
 export const addressProofMsgBuffer = trimMessagePrefix(addressProofBuffer);
-// We know that that the entropy is a set 64 bytes.
-export const addressProofEntropy = addressProofMsgBuffer.subarray(0, 65);
+const payGoAttestationProofComponents = parsePayGoAttestation(addressProofBuffer);
+
+export const addressProofEntropy = payGoAttestationProofComponents.entropy;
 
 // signature with the given msg addressProofBuffer
 export const sig = signMessage(addressProofMsgBuffer.toString(), attestationPrvKey!, network);
@@ -131,3 +134,36 @@ describe('getPaygoAddressProofIndex', () => {
     );
   });
 });
+
+describe('trimMessagePrefix', function () {
+  it('should be the same proof constructed consistently', function () {
+    const psbt = getTestPsbt();
+    psbt.addOutput({ script: utxolib.address.toOutputScript(addressToVerify, network), value: BigInt(10000) });
+    const outputIndex = psbt.data.outputs.length - 1;
+    addPayGoAddressProof(psbt, outputIndex, sig, addressProofEntropy);
+    // manually check without the verify function to see if the entropy being stored
+    // in the psbt is the same as the entropy being extracted and trimmed.
+    const psbtOutputs = checkForOutput(psbt.data.outputs, outputIndex);
+    const stored = utxolib.bitgo.getProprietaryKeyValuesFromUnknownKeyValues(psbtOutputs, {
+      identifier: utxolib.bitgo.PSBT_PROPRIETARY_IDENTIFIER,
+      subtype: utxolib.bitgo.ProprietaryKeySubtype.PAYGO_ADDRESS_ATTESTATION_PROOF,
+    });
+
+    assert(stored[0].key.keydata.equals(payGoAttestationProofComponents.entropy));
+    assert(stored[0].value.equals(sig));
+
+    const reconstructedProofFromComponents = Buffer.concat([
+      payGoAttestationProofComponents.entropy,
+      payGoAttestationProofComponents.address,
+      payGoAttestationProofComponents.uuid,
+    ]);
+    const verifyConstructedProof = createPayGoAttestationBuffer(
+      addressToVerify,
+      stored[0].key.keydata,
+      utxolib.networks.bitcoin
+    );
+
+    assert(addressProofMsgBuffer.equals(reconstructedProofFromComponents));
+    assert(verifyConstructedProof.equals(reconstructedProofFromComponents));
+  });
+});