chore(utxo-core): moved files to utxo-core

Issue: BTC-2150

TICKET: BTC-2150

Author: christopher-fong

modules/utxo-core/src/ExtractAddressPayGoAttestation.ts

@@ -0,0 +1,45 @@
+import assert from 'assert';
+
+import { varuint } from 'bitcoinjs-lib/src/bufferutils';
+
+// The signed address will always have the following structure:
+// 0x18Bitcoin Signed Message:\n<varint_length><ENTROPY><ADDRESS><UUID>
+
+const PrefixLength = Buffer.from([0x18]).length + Buffer.from('Bitcoin Signed Message:\n').length;
+// UUID has the structure 00000000-0000-0000-0000-000000000000, and after
+// we Buffer.from and get it's length its 36.
+const UuidBufferLength = 36;
+// The entropy will always be 64 bytes
+const EntropyLen = 64;
+
+/**
+ * This function takes in the attestation proof of a PayGo address of the from
+ * 0x18Bitcoin Signed Message:\n<varint_length><ENTROPY><ADDRESS><UUID> and returns
+ * the address given its length. It is assumed that the ENTROPY is 64 bytes in the Buffer
+ * so if not given an address proof length we can still extract the address from the proof.
+ *
+ * @param message
+ * @param adressProofLength
+ */
+export function extractAddressBufferFromPayGoAttestationProof(message: Buffer): Buffer {
+  if (message.length <= PrefixLength + EntropyLen + UuidBufferLength) {
+    throw new Error('PayGo attestation proof is too short to contain a valid address');
+  }
+
+  // This generates the first part before the varint length so that we can
+  // determine how many bytes this is and iterate through the Buffer.
+  let offset = PrefixLength;
+
+  // we decode the varint of the message which is uint32
+  // https://en.bitcoin.it/wiki/Protocol_documentation
+  const varInt = varuint.decode(message, offset);
+  assert(varInt);
+  offset += 1;
+
+  const addressLength = varInt - EntropyLen - UuidBufferLength;
+  offset += EntropyLen;
+
+  // we return what the Buffer subarray from the offset (beginning of address)
+  // to the end of the address index in the buffer.
+  return message.subarray(offset, offset + addressLength);
+}

modules/utxo-core/src/index.ts

@@ -4,3 +4,4 @@ export * as testutil from './testutil';
 export * from './dustThreshold';
 export * from './Output';
 export * from './xOnlyPubkey';
+export * from './ExtractAddressPayGoAttestation';

modules/utxo-core/test/ExtractAddressPayGoAttestation.ts

@@ -0,0 +1,44 @@
+import * as assert from 'assert';
+
+import * as utxolib from '@bitgo/utxo-lib';
+
+import { extractAddressBufferFromPayGoAttestationProof } from '../src/ExtractAddressPayGoAttestation';
+
+const addressFromPubKeyBase58 = 'bitgoAddressToExtract';
+const bufferAddressPubKeyB58 = Buffer.from(addressFromPubKeyBase58);
+
+describe('extractAddressBufferFromPayGoAttestationProof', () => {
+  it('should extractAddressBufferFromPayGoAttestationProof properly', () => {
+    const paygoAttestationProof = utxolib.testutil.generatePayGoAttestationProof(
+      '00000000-0000-0000-0000-000000000000',
+      bufferAddressPubKeyB58
+    );
+    const addressFromProof = extractAddressBufferFromPayGoAttestationProof(paygoAttestationProof);
+    assert.deepStrictEqual(Buffer.compare(addressFromProof, bufferAddressPubKeyB58), 0);
+  });
+
+  it('should extract the paygo address paygo attestation proof given a non nilUUID', () => {
+    const paygoAttestationProof = utxolib.testutil.generatePayGoAttestationProof(
+      '12345678-1234-4567-6890-231928472123',
+      bufferAddressPubKeyB58
+    );
+    const addressFromProof = extractAddressBufferFromPayGoAttestationProof(paygoAttestationProof);
+    assert.deepStrictEqual(Buffer.compare(addressFromProof, bufferAddressPubKeyB58), 0);
+  });
+
+  it('should not extract the correct address given a uuid of wrong format', () => {
+    const paygoAttestationProof = utxolib.testutil.generatePayGoAttestationProof(
+      '000000000000000-000000-0000000-000000-0000000000000000',
+      bufferAddressPubKeyB58
+    );
+    const addressFromProof = extractAddressBufferFromPayGoAttestationProof(paygoAttestationProof);
+    assert.notDeepStrictEqual(Buffer.compare(addressFromProof, bufferAddressPubKeyB58), 0);
+  });
+
+  it('should throw an error if the paygo attestation proof is too short', () => {
+    assert.throws(
+      () => extractAddressBufferFromPayGoAttestationProof(Buffer.from('shortproof-shrug')),
+      'PayGo attestation proof is too short to contain a valid address.'
+    );
+  });
+});