Merge pull request #6155 from BitGo/BTC-2047.adding-paygoinfo

feat(utxo-core): PayGo Attestation util functions

Author: christopher-fong

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

@@ -0,0 +1,19 @@
+import assert from 'assert';
+
+import * as utxolib from '@bitgo/utxo-lib';
+export const NIL_UUID = '00000000-0000-0000-0000-000000000000';
+
+/** This function reconstructs the proof <ENTROPY><ADDRESS><UUID>
+ * given the address and entropy.
+ *
+ * @param address
+ * @param entropy
+ * @returns
+ */
+export function createPayGoAttestationBuffer(address: string, entropy: Buffer, network: utxolib.Network): Buffer {
+  assert(address.length > 0);
+  const isValidAddress = utxolib.address.toOutputScript(address, network);
+  assert(isValidAddress, `Address ${address} is not a valid address.`);
+  const addressBuffer = Buffer.from(address);
+  return Buffer.concat([entropy, addressBuffer, Buffer.from(NIL_UUID)]);
+}

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

@@ -1 +1,2 @@
 export * from './ExtractAddressPayGoAttestation';
+export * from './psbt';

modules/utxo-core/src/paygo/psbt/Errors.ts

@@ -0,0 +1,36 @@
+export class PayGoError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = this.constructor.name;
+  }
+}
+
+export class ErrorNoPayGoProof extends PayGoError {
+  constructor(public outputIndex: number) {
+    super(`There is no paygo address proof encoded in the PSBT at output ${outputIndex}.`);
+  }
+}
+
+export class ErrorMultiplePayGoProof extends PayGoError {
+  constructor() {
+    super('There are multiple paygo address proofs encoded in the PSBT. Something went wrong.');
+  }
+}
+
+export class ErrorPayGoAddressProofFailedVerification extends PayGoError {
+  constructor() {
+    super('Cannot verify the paygo address signature with the provided pubkey.');
+  }
+}
+
+export class ErrorOutputIndexOutOfBounds extends PayGoError {
+  constructor(public outputIndex: number) {
+    super(`Output index ${outputIndex} is out of bounds for PSBT outputs.`);
+  }
+}
+
+export class ErrorMultiplePayGoProofAtPsbtIndex extends PayGoError {
+  constructor(public outputIndex: number) {
+    super(`There are multiple PayGo addresses in the PSBT output ${outputIndex}.`);
+  }
+}

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

@@ -0,0 +1 @@
+export * from './payGoAddressProof';

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

@@ -0,0 +1,110 @@
+import * as utxolib from '@bitgo/utxo-lib';
+import { checkForOutput } from 'bip174/src/lib/utils';
+
+import { verifyMessage } from '../../bip32utils';
+import { createPayGoAttestationBuffer } from '../attestation';
+
+import {
+  ErrorMultiplePayGoProof,
+  ErrorMultiplePayGoProofAtPsbtIndex,
+  ErrorNoPayGoProof,
+  ErrorOutputIndexOutOfBounds,
+  ErrorPayGoAddressProofFailedVerification,
+} from './Errors';
+
+/** This function adds the entropy and signature into the PSBT output unknown key vals.
+ * We store the entropy so that we reconstruct the message <ENTROPY><ADDRESS><UUID>
+ * to later verify.
+ *
+ * @param psbt - PSBT that we need to encode our paygo address into
+ * @param outputIndex - the index of the address in our output
+ * @param sig - the signature that we want to encode
+ */
+export function addPayGoAddressProof(
+  psbt: utxolib.bitgo.UtxoPsbt,
+  outputIndex: number,
+  sig: Buffer,
+  entropy: Buffer
+): void {
+  utxolib.bitgo.addProprietaryKeyValuesFromUnknownKeyValues(psbt, 'output', outputIndex, {
+    key: {
+      identifier: utxolib.bitgo.PSBT_PROPRIETARY_IDENTIFIER,
+      subtype: utxolib.bitgo.ProprietaryKeySubtype.PAYGO_ADDRESS_ATTESTATION_PROOF,
+      keydata: entropy,
+    },
+    value: sig,
+  });
+}
+
+/** Verify the paygo address signature is valid using verification pub key.
+ *
+ * @param psbt - PSBT we want to verify that the paygo address is in
+ * @param outputIndex - we have the output index that address is in
+ * @param uuid
+ * @returns
+ */
+export function verifyPayGoAddressProof(
+  psbt: utxolib.bitgo.UtxoPsbt,
+  outputIndex: number,
+  verificationPubkey: Buffer
+): void {
+  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 length is 0 or 1
+  if (stored.length === 0) {
+    throw new ErrorNoPayGoProof(outputIndex);
+  } else if (stored.length > 1) {
+    throw new ErrorMultiplePayGoProof();
+  }
+
+  // We get the signature and entropy from our PSBT unknown key vals
+  const signature = stored[0].value;
+  const entropy = stored[0].key.keydata;
+
+  // Get the the PayGo address from the txOutputs
+  const txOutputs = psbt.txOutputs;
+  if (outputIndex >= txOutputs.length) {
+    throw new ErrorOutputIndexOutOfBounds(outputIndex);
+  }
+  const output = txOutputs[outputIndex];
+  const addressFromOutput = utxolib.address.fromOutputScript(output.script, psbt.network);
+
+  // We construct our message <ENTROPY><ADDRESS><UUID>
+  const message = createPayGoAttestationBuffer(addressFromOutput, entropy, psbt.network);
+
+  if (!verifyMessage(message.toString(), verificationPubkey, signature, utxolib.networks.bitcoin)) {
+    throw new ErrorPayGoAddressProofFailedVerification();
+  }
+}
+
+/** Get the output index of the paygo output if there is one. It does this by
+ * checking if the metadata is on one of the outputs of the PSBT. If there is
+ * no paygo output, return undefined
+ *
+ * @param psbt
+ * @returns number - the index of the output address
+ */
+export function getPayGoAddressProofOutputIndex(psbt: utxolib.bitgo.UtxoPsbt): number | undefined {
+  const res = psbt.data.outputs.flatMap((output, outputIndex) => {
+    const proprietaryKeyVals = utxolib.bitgo.getPsbtOutputProprietaryKeyVals(output, {
+      identifier: utxolib.bitgo.PSBT_PROPRIETARY_IDENTIFIER,
+      subtype: utxolib.bitgo.ProprietaryKeySubtype.PAYGO_ADDRESS_ATTESTATION_PROOF,
+    });
+
+    if (proprietaryKeyVals.length > 1) {
+      throw new ErrorMultiplePayGoProofAtPsbtIndex(outputIndex);
+    }
+
+    return proprietaryKeyVals.length === 0 ? [] : [outputIndex];
+  });
+
+  return res.length === 0 ? undefined : res[0];
+}
+
+export function psbtOutputIncludesPaygoAddressProof(psbt: utxolib.bitgo.UtxoPsbt): boolean {
+  return getPayGoAddressProofOutputIndex(psbt) !== undefined;
+}

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

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

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

@@ -0,0 +1,25 @@
+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.
+ *
+ * @param proof
+ * @returns
+ */
+export function trimMessagePrefix(proof: Buffer): Buffer {
+  const prefix = '\u0018Bitcoin Signed Message:\n';
+  if (proof.toString().startsWith(prefix)) {
+    proof = proof.slice(Buffer.from(prefix).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;
+}

modules/utxo-core/test/paygo/attestation.ts

@@ -0,0 +1,24 @@
+import assert from 'assert';
+
+import { createPayGoAttestationBuffer } from '../../src/paygo/attestation';
+import { generatePayGoAttestationProof } from '../../src/testutil';
+
+import { addressProofEntropy, addressProofMsgBuffer, addressToVerify, network } from './psbt/payGoAddressProof';
+
+describe('createPayGoAttestationBuffer', () => {
+  it('should create a PayGo Attestation proof matching with original proof', () => {
+    const payGoAttestationProof = createPayGoAttestationBuffer(addressToVerify, addressProofEntropy, network);
+    assert.strictEqual(payGoAttestationProof.toString(), addressProofMsgBuffer.toString());
+    assert(Buffer.compare(payGoAttestationProof, addressProofMsgBuffer) === 0);
+  });
+
+  it('should create a PayGo Attestation proof that does not match with different uuid', () => {
+    const addressProofBufferDiffUuid = generatePayGoAttestationProof(
+      '00000000-0000-0000-0000-000000000001',
+      Buffer.from(addressToVerify)
+    );
+    const payGoAttestationProof = createPayGoAttestationBuffer(addressToVerify, addressProofEntropy, network);
+    assert.notStrictEqual(payGoAttestationProof.toString(), addressProofBufferDiffUuid.toString());
+    assert(Buffer.compare(payGoAttestationProof, addressProofBufferDiffUuid) !== 0);
+  });
+});

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

@@ -0,0 +1,133 @@
+import assert from 'assert';
+import crypto from 'crypto';
+
+import * as utxolib from '@bitgo/utxo-lib';
+import { decodeProprietaryKey } from 'bip174/src/lib/proprietaryKeyVal';
+import { KeyValue } from 'bip174/src/lib/interfaces';
+import { checkForOutput } from 'bip174/src/lib/utils';
+
+import {
+  addPayGoAddressProof,
+  getPayGoAddressProofOutputIndex,
+  psbtOutputIncludesPaygoAddressProof,
+  verifyPayGoAddressProof,
+} from '../../../src/paygo/psbt/payGoAddressProof';
+import { generatePayGoAttestationProof } from '../../../src/testutil/generatePayGoAttestationProof.utils';
+import { trimMessagePrefix } from '../../../src/testutil/trimMessagePrefix';
+import { signMessage } from '../../../src/bip32utils';
+import { NIL_UUID } from '../../../src/paygo/attestation';
+
+// To construct our PSBTs
+export const network = utxolib.networks.bitcoin;
+const keys = [1, 2, 3].map((v) => utxolib.bip32.fromSeed(Buffer.alloc(16, `test/2/${v}`), network));
+const rootWalletKeys = new utxolib.bitgo.RootWalletKeys([keys[0], keys[1], keys[2]]);
+
+// PSBT INPUTS AND OUTPUTS
+const psbtInputs = utxolib.testutil.inputScriptTypes.map((scriptType) => ({
+  scriptType,
+  value: BigInt(1000),
+}));
+const psbtOutputs = utxolib.testutil.outputScriptTypes.map((scriptType) => ({
+  scriptType,
+  value: BigInt(900),
+}));
+
+// wallet pub and priv key for tbtc
+const dummyPub1 = rootWalletKeys.deriveForChainAndIndex(50, 200);
+export const attestationPubKey = dummyPub1.user.publicKey;
+export const attestationPrvKey = dummyPub1.user.privateKey!;
+
+// our xpub converted to base58 address
+export const addressToVerify = utxolib.address.toBase58Check(
+  utxolib.crypto.hash160(Buffer.from(dummyPub1.backup.publicKey)),
+  utxolib.networks.bitcoin.pubKeyHash,
+  utxolib.networks.bitcoin
+);
+
+// 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);
+
+// signature with the given msg addressProofBuffer
+export const sig = signMessage(addressProofMsgBuffer.toString(), attestationPrvKey!, network);
+
+function getTestPsbt() {
+  return utxolib.testutil.constructPsbt(psbtInputs, psbtOutputs, network, rootWalletKeys, 'unsigned');
+}
+
+describe('addPaygoAddressProof and verifyPaygoAddressProof', () => {
+  function getPayGoProprietaryKey(proprietaryKeyVals: KeyValue[]) {
+    return proprietaryKeyVals
+      .map(({ key, value }) => {
+        return { key: decodeProprietaryKey(key), value };
+      })
+      .filter((keyValue) => {
+        return (
+          keyValue.key.identifier === utxolib.bitgo.PSBT_PROPRIETARY_IDENTIFIER &&
+          keyValue.key.subtype === utxolib.bitgo.ProprietaryKeySubtype.PAYGO_ADDRESS_ATTESTATION_PROOF
+        );
+      });
+  }
+
+  it('should add and verify a valid paygo address proof on the PSBT', () => {
+    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);
+    verifyPayGoAddressProof(psbt, outputIndex, attestationPubKey);
+  });
+
+  it('should throw an error if there are multiple PayGo proprietary keys in the PSBT', () => {
+    const outputIndex = 0;
+    const psbt = getTestPsbt();
+    addPayGoAddressProof(psbt, outputIndex, sig, addressProofEntropy);
+    addPayGoAddressProof(psbt, outputIndex, Buffer.from('signature2'), crypto.randomBytes(64));
+    const output = checkForOutput(psbt.data.outputs, outputIndex);
+    const proofInPsbt = getPayGoProprietaryKey(output.unknownKeyVals!);
+    assert(proofInPsbt.length !== 0);
+    assert(proofInPsbt.length > 1);
+    assert.throws(
+      () => verifyPayGoAddressProof(psbt, outputIndex, attestationPubKey),
+      (e: any) => e.message === 'There are multiple paygo address proofs encoded in the PSBT. Something went wrong.'
+    );
+  });
+});
+
+describe('verifyPaygoAddressProof', () => {
+  it('should throw an error if there is no PayGo address in PSBT', () => {
+    const psbt = getTestPsbt();
+    assert.throws(
+      () => verifyPayGoAddressProof(psbt, 0, attestationPubKey),
+      (e: any) => e.message === 'There is no paygo address proof encoded in the PSBT at output 0.'
+    );
+  });
+});
+
+describe('getPaygoAddressProofIndex', () => {
+  it('should get PayGo address proof index from PSBT if there is one', () => {
+    const psbt = getTestPsbt();
+    const outputIndex = 0;
+    addPayGoAddressProof(psbt, outputIndex, sig, Buffer.from(attestationPubKey));
+    assert(psbtOutputIncludesPaygoAddressProof(psbt));
+    assert(getPayGoAddressProofOutputIndex(psbt) === 0);
+  });
+
+  it('should return undefined if there is no PayGo address proof in PSBT', () => {
+    const psbt = getTestPsbt();
+    assert(getPayGoAddressProofOutputIndex(psbt) === undefined);
+    assert(!psbtOutputIncludesPaygoAddressProof(psbt));
+  });
+
+  it('should return an error and fail if we have multiple PayGo address in the PSBT in the same output index', () => {
+    const psbt = getTestPsbt();
+    const outputIndex = 0;
+    addPayGoAddressProof(psbt, outputIndex, sig, addressProofEntropy);
+    addPayGoAddressProof(psbt, outputIndex, sig, crypto.randomBytes(64));
+    assert.throws(
+      () => getPayGoAddressProofOutputIndex(psbt),
+      (e: any) => e.message === 'There are multiple PayGo addresses in the PSBT output 0.'
+    );
+  });
+});

modules/utxo-lib/src/bitgo/PsbtUtil.ts

@@ -20,6 +20,7 @@ export enum ProprietaryKeySubtype {
   MUSIG2_PARTICIPANT_PUB_KEYS = 0x01,
   MUSIG2_PUB_NONCE = 0x02,
   MUSIG2_PARTIAL_SIG = 0x03,
+  PAYGO_ADDRESS_ATTESTATION_PROOF = 0x04,
 }
 
 /**