| 1 | import 'dart:async'; |
| 2 | import 'dart:io'; |
| 3 | import 'dart:isolate'; |
| 4 | import 'dart:typed_data'; |
| 5 | |
| 6 | import 'package:blockchain_utils/blockchain_utils.dart'; |
| 7 | import 'package:cw_bitcoin/payjoin/manager.dart'; |
| 8 | import 'package:cw_bitcoin/payjoin/payjoin_session_errors.dart'; |
| 9 | import 'package:cw_bitcoin/psbt/signer.dart'; |
| 10 | import 'package:cw_core/utils/print_verbose.dart'; |
| 11 | import 'package:cw_core/utils/proxy_wrapper.dart'; |
| 12 | import 'package:cw_core/utils/tor/abstract.dart'; |
| 13 | import 'package:payjoin_flutter/bitcoin_ffi.dart'; |
| 14 | import 'package:payjoin_flutter/common.dart'; |
| 15 | import 'package:payjoin_flutter/receive.dart'; |
| 16 | import 'package:payjoin_flutter/src/generated/frb_generated.dart' as pj; |
| 17 | import 'package:http/http.dart' as very_insecure_http_do_not_use; // for errors |
| 18 | |
| 19 | enum PayjoinReceiverRequestTypes { |
| 20 | processOriginalTx, |
| 21 | proposalSent, |
| 22 | getCandidateInputs, |
| 23 | checkIsOwned, |
| 24 | checkIsReceiverOutput, |
| 25 | processPsbt; |
| 26 | } |
| 27 | |
| 28 | class PayjoinReceiverWorker { |
| 29 | final SendPort sendPort; |
| 30 | final pendingRequests = <String, Completer<dynamic>>{}; |
| 31 | |
| 32 | PayjoinReceiverWorker._(this.sendPort); |
| 33 | static final client = ProxyWrapper().getHttpIOClient(); |
| 34 | static Future<void> run(List<Object> args) async { |
| 35 | await pj.core.init(); |
| 36 | CakeTor.instance = await CakeTorInstance.getInstance(); |
| 37 | |
| 38 | final sendPort = args[0] as SendPort; |
| 39 | final receiverJson = args[1] as String; |
| 40 | |
| 41 | final worker = PayjoinReceiverWorker._(sendPort); |
| 42 | final receivePort = ReceivePort(); |
| 43 | |
| 44 | sendPort.send(receivePort.sendPort); |
| 45 | receivePort.listen(worker.handleMessage); |
| 46 | |
| 47 | try { |
| 48 | final receiver = Receiver.fromJson(json: receiverJson); |
| 49 | |
| 50 | final uncheckedProposal = await worker.receiveUncheckedProposal(receiver); |
| 51 | |
| 52 | final originalTx = await uncheckedProposal.extractTxToScheduleBroadcast(); |
| 53 | sendPort.send({ |
| 54 | 'type': PayjoinReceiverRequestTypes.processOriginalTx, |
| 55 | 'tx': BytesUtils.toHexString(originalTx), |
| 56 | }); |
| 57 | |
| 58 | final payjoinProposal = await worker.processPayjoinProposal( |
| 59 | uncheckedProposal, |
| 60 | ); |
| 61 | final psbt = await worker.sendFinalProposal(payjoinProposal); |
| 62 | sendPort.send({ |
| 63 | 'type': PayjoinReceiverRequestTypes.proposalSent, |
| 64 | 'psbt': psbt, |
| 65 | }); |
| 66 | } catch (e) { |
| 67 | if (e is HttpException || |
| 68 | (e is very_insecure_http_do_not_use.ClientException && |
| 69 | e.message.contains("Software caused connection abort"))) { |
| 70 | sendPort.send(PayjoinSessionError.recoverable(e.toString())); |
| 71 | } else { |
| 72 | sendPort.send(PayjoinSessionError.unrecoverable(e.toString())); |
| 73 | } |
| 74 | } |
| 75 | } |
| 76 | |
| 77 | void handleMessage(dynamic message) async { |
| 78 | if (message is Map<String, dynamic>) { |
| 79 | final requestId = message['requestId'] as String?; |
| 80 | if (requestId != null && pendingRequests.containsKey(requestId)) { |
| 81 | pendingRequests[requestId]!.complete(message['result']); |
| 82 | pendingRequests.remove(requestId); |
| 83 | } |
| 84 | } |
| 85 | } |
| 86 | |
| 87 | Future<dynamic> _sendRequest(PayjoinReceiverRequestTypes type, |
| 88 | [Map<String, dynamic> data = const {}]) async { |
| 89 | final completer = Completer<dynamic>(); |
| 90 | final requestId = DateTime.now().millisecondsSinceEpoch.toString(); |
| 91 | pendingRequests[requestId] = completer; |
| 92 | |
| 93 | sendPort.send({ |
| 94 | ...data, |
| 95 | 'type': type, |
| 96 | 'requestId': requestId, |
| 97 | }); |
| 98 | |
| 99 | return completer.future; |
| 100 | } |
| 101 | |
| 102 | Future<UncheckedProposal> receiveUncheckedProposal(Receiver session) async { |
| 103 | while (true) { |
| 104 | printV("Polling for Proposal (${session.id()})"); |
| 105 | final extractReq = await session.extractReq( |
| 106 | ohttpRelay: await PayjoinManager.randomOhttpRelayUrl(), |
| 107 | ); |
| 108 | final request = extractReq.$1; |
| 109 | |
| 110 | final url = Uri.parse(request.url.asString()); |
| 111 | final httpRequest = await client.post(url, |
| 112 | headers: {'Content-Type': request.contentType}, body: request.body); |
| 113 | |
| 114 | final proposal = await session.processRes(body: httpRequest.bodyBytes, ctx: extractReq.$2); |
| 115 | if (proposal != null) return proposal; |
| 116 | sleep(Duration(seconds: 2)); |
| 117 | } |
| 118 | } |
| 119 | |
| 120 | Future<String> sendFinalProposal(PayjoinProposal finalProposal) async { |
| 121 | final req = await finalProposal.extractReq( |
| 122 | ohttpRelay: await PayjoinManager.randomOhttpRelayUrl(), |
| 123 | ); |
| 124 | final proposalReq = req.$1; |
| 125 | final proposalCtx = req.$2; |
| 126 | |
| 127 | final request = await client.post( |
| 128 | Uri.parse(proposalReq.url.asString()), |
| 129 | headers: {"Content-Type": proposalReq.contentType}, |
| 130 | body: proposalReq.body, |
| 131 | ); |
| 132 | |
| 133 | await finalProposal.processRes( |
| 134 | res: request.bodyBytes, |
| 135 | ohttpContext: proposalCtx, |
| 136 | ); |
| 137 | |
| 138 | return await finalProposal.psbt(); |
| 139 | } |
| 140 | |
| 141 | Future<PayjoinProposal> processPayjoinProposal(UncheckedProposal proposal) async { |
| 142 | await proposal.extractTxToScheduleBroadcast(); |
| 143 | // TODO Handle this. send to the main port on a timer? |
| 144 | |
| 145 | try { |
| 146 | // Receive Check 1: can broadcast |
| 147 | final pj1 = await proposal.assumeInteractiveReceiver(); |
| 148 | |
| 149 | // Receive Check 2: original PSBT has no receiver-owned inputs |
| 150 | final pj2 = await pj1.checkInputsNotOwned( |
| 151 | isOwned: (inputScript) async { |
| 152 | final result = await _sendRequest( |
| 153 | PayjoinReceiverRequestTypes.checkIsOwned, |
| 154 | {'input_script': inputScript}, |
| 155 | ); |
| 156 | return result as bool; |
| 157 | }, |
| 158 | ); |
| 159 | // Receive Check 3: sender inputs have not been seen before (prevent probing attacks) |
| 160 | final pj3 = await pj2.checkNoInputsSeenBefore(isKnown: (input) => false); |
| 161 | |
| 162 | // Identify receiver outputs |
| 163 | final pj4 = await pj3.identifyReceiverOutputs( |
| 164 | isReceiverOutput: (outputScript) async { |
| 165 | final result = await _sendRequest( |
| 166 | PayjoinReceiverRequestTypes.checkIsReceiverOutput, |
| 167 | {'output_script': outputScript}, |
| 168 | ); |
| 169 | return result as bool; |
| 170 | }, |
| 171 | ); |
| 172 | final pj5 = await pj4.commitOutputs(); |
| 173 | |
| 174 | final listUnspent = await _sendRequest(PayjoinReceiverRequestTypes.getCandidateInputs); |
| 175 | final unspent = listUnspent as List<UtxoWithPrivateKey>; |
| 176 | if (unspent.isEmpty) throw RecoverableError('No unspent outputs available'); |
| 177 | |
| 178 | final candidateInputs = await Future.wait(unspent.map(_inputPairFromUtxo)); |
| 179 | |
| 180 | // Prefer a UTXO that avoids the Unnecessary Input Heuristic (UIH2); |
| 181 | // fall back to the first candidate if none preserves privacy. |
| 182 | InputPair selectedUtxo = candidateInputs.first; |
| 183 | try { |
| 184 | selectedUtxo = await pj5.tryPreservingPrivacy(candidateInputs: candidateInputs); |
| 185 | } catch (_) {} |
| 186 | |
| 187 | final pj6 = await pj5.contributeInputs(replacementInputs: [selectedUtxo]); |
| 188 | final pj7 = await pj6.commitInputs(); |
| 189 | |
| 190 | // Finalize proposal |
| 191 | final payjoinProposal = await pj7.finalizeProposal( |
| 192 | processPsbt: (String psbt) async { |
| 193 | final result = |
| 194 | await _sendRequest(PayjoinReceiverRequestTypes.processPsbt, {'psbt': psbt}); |
| 195 | return result as String; |
| 196 | }, |
| 197 | // TODO set maxFeeRateSatPerVb |
| 198 | maxFeeRateSatPerVb: BigInt.from(10000), |
| 199 | ); |
| 200 | return payjoinProposal; |
| 201 | } catch (e) { |
| 202 | printV('Error occurred while finalizing proposal: $e'); |
| 203 | rethrow; |
| 204 | } |
| 205 | } |
| 206 | |
| 207 | Future<InputPair> _inputPairFromUtxo(UtxoWithPrivateKey utxo) async { |
| 208 | final txout = TxOut( |
| 209 | value: utxo.utxo.value, |
| 210 | scriptPubkey: Uint8List.fromList(utxo.ownerDetails.address.toScriptPubKey().toBytes()), |
| 211 | ); |
| 212 | |
| 213 | final psbtin = PsbtInput(witnessUtxo: txout, redeemScript: null, witnessScript: null); |
| 214 | |
| 215 | final previousOutput = OutPoint(txid: utxo.utxo.txHash, vout: utxo.utxo.vout); |
| 216 | |
| 217 | final txin = TxIn( |
| 218 | previousOutput: previousOutput, |
| 219 | scriptSig: await Script.newInstance(rawOutputScript: []), |
| 220 | witness: [], |
| 221 | sequence: 0, |
| 222 | ); |
| 223 | |
| 224 | return InputPair.newInstance(txin: txin, psbtin: psbtin); |
| 225 | } |
| 226 | } |