file upload actor
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randogoth
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174
lib/src/file_upload_actor.dart
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174
lib/src/file_upload_actor.dart
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import 'dart:convert';
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import 'dart:math';
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import 'dart:typed_data';
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import 'package:actors/actors.dart';
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import 'package:bip340/bip340.dart' as bip340;
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import 'package:crypto/crypto.dart';
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import 'package:http/http.dart' as http;
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import 'nip44.dart';
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import 'relay_connection.dart';
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const _kServicePubkey =
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'7de7d9f8c0aad59b0e325eef5e1c7d777a3b4c1b3df8ac71c72dae763a161435';
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const _kDefaultApiBaseUrl = 'https://upload.otherwhere.app';
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const _kDefaultRelayUrl = 'wss://relay.otherwhere.app/';
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const _kMaxFileBytes = 10 * 1024 * 1024; // 10 MB server-side limit
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sealed class FileUploadMessage {
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const FileUploadMessage();
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}
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final class RegisterForUpload extends FileUploadMessage {
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const RegisterForUpload();
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}
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final class UploadFile extends FileUploadMessage {
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final Uint8List bytes;
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final String contentType;
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const UploadFile({required this.bytes, required this.contentType});
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}
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sealed class FileUploadResult {
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const FileUploadResult();
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}
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final class UploaderRegistered extends FileUploadResult {
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const UploaderRegistered();
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}
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final class FileUploaded extends FileUploadResult {
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final String cdnUrl;
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const FileUploaded(this.cdnUrl);
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}
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class FileUploadActor with Handler<FileUploadMessage, FileUploadResult> {
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final String _privateKey;
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final String _publicKey;
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final String _appName;
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final String _appSecret;
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final String _apiBaseUrl;
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final String _relayUrl;
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final http.Client _httpClient;
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final RelayConnection Function(String) _connectionFactory;
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FileUploadActor({
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required String privateKey,
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required String appName,
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required String appSecret,
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String apiBaseUrl = _kDefaultApiBaseUrl,
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String relayUrl = _kDefaultRelayUrl,
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http.Client? httpClient,
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RelayConnection Function(String)? connectionFactory,
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}) : _privateKey = privateKey,
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_publicKey = bip340.getPublicKey(privateKey),
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_appName = appName,
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_appSecret = appSecret,
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_apiBaseUrl = apiBaseUrl,
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_relayUrl = relayUrl,
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_httpClient = httpClient ?? http.Client(),
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_connectionFactory = connectionFactory ?? WebSocketRelayConnection.new;
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@override
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Future<FileUploadResult> handle(FileUploadMessage message) => switch (message) {
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RegisterForUpload() => _register(),
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UploadFile(:final bytes, :final contentType) =>
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_upload(bytes, contentType),
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};
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@override
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Future<void> close() async => _httpClient.close();
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Future<UploaderRegistered> _register() async {
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final encryptedSecret =
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nip44Encrypt(_appSecret, _privateKey, _kServicePubkey);
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final eventJson = _signEvent(
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kind: 5392,
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tags: [
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['p', _kServicePubkey],
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['app', _appName],
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],
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content: encryptedSecret,
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);
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final conn = _connectionFactory(_relayUrl);
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try {
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await conn.connect();
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await conn.send(jsonEncode(['EVENT', jsonDecode(eventJson)]));
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} finally {
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await conn.close();
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}
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return const UploaderRegistered();
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}
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Future<FileUploaded> _upload(Uint8List bytes, String contentType) async {
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if (bytes.length > _kMaxFileBytes) {
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throw Exception(
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'File exceeds 10 MB limit (${bytes.length} bytes)',
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);
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}
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final (uploadUrl, cdnUrl) = await _requestUploadUrl(contentType);
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final putResponse = await _httpClient.put(
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Uri.parse(uploadUrl),
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headers: {'Content-Type': contentType},
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body: bytes,
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);
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if (putResponse.statusCode != 200 && putResponse.statusCode != 204) {
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throw Exception('Storage PUT failed: ${putResponse.statusCode}');
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}
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return FileUploaded(cdnUrl);
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}
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Future<(String, String)> _requestUploadUrl(String contentType) async {
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final url = '$_apiBaseUrl/upload/request';
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final authEvent = _signEvent(
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kind: 27235,
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tags: [
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['u', url],
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['method', 'POST'],
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],
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content: '',
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);
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// NIP-98: Authorization: Nostr <base64(utf8(json(event)))>
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final token = base64.encode(utf8.encode(authEvent));
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final response = await _httpClient.post(
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Uri.parse(url),
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headers: {
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'Authorization': 'Nostr $token',
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'Content-Type': 'application/json',
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},
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body: jsonEncode({'app': _appName, 'content_type': contentType}),
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);
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if (response.statusCode != 200) {
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throw Exception('Upload request failed: ${response.statusCode}');
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}
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final body = jsonDecode(response.body) as Map<String, dynamic>;
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return (body['upload_url'] as String, body['cdn_url'] as String);
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}
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String _signEvent({
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required int kind,
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required List<List<String>> tags,
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required String content,
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}) {
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final ts = DateTime.now().millisecondsSinceEpoch ~/ 1000;
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final ser = jsonEncode([0, _publicKey, ts, kind, tags, content]);
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final idBytes = sha256.convert(utf8.encode(ser)).bytes;
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final id =
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idBytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
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final rng = Random.secure();
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final aux = List.generate(32, (_) => rng.nextInt(256))
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.map((b) => b.toRadixString(16).padLeft(2, '0'))
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.join();
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final sig = bip340.sign(_privateKey, id, aux);
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return jsonEncode({
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'id': id,
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'pubkey': _publicKey,
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'created_at': ts,
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'kind': kind,
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'tags': tags,
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'content': content,
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'sig': sig,
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});
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}
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}
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131
lib/src/nip44.dart
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131
lib/src/nip44.dart
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@ -0,0 +1,131 @@
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import 'dart:convert';
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import 'dart:math';
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import 'dart:typed_data';
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import 'package:crypto/crypto.dart';
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import 'package:pointycastle/export.dart';
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/// Derives the NIP-44 v2 conversation key.
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/// secp256k1 ECDH(privkey, pubkey) → HKDF-SHA256(ikm=sharedX, salt=32·0x00, info="nip44-v2") → 32 bytes.
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Uint8List nip44ConversationKey(String privkeyHex, String pubkeyHex) {
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final domain = ECCurve_secp256k1();
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final priv = BigInt.parse(privkeyHex, radix: 16);
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// Nostr pubkeys are x-only; always reconstruct with even-y (0x02 prefix).
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final pubBytes = Uint8List.fromList([0x02, ...hexToBytes(pubkeyHex)]);
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final pub = domain.curve.decodePoint(pubBytes)!;
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final sharedX = (pub * priv)!
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.x!
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.toBigInteger()!
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.toRadixString(16)
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.padLeft(64, '0');
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return hkdf(hexToBytes(sharedX), Uint8List(32), utf8.encode('nip44-v2'), 32);
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}
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/// Encrypts [plaintext] with NIP-44 v2. Returns a base64 payload.
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String nip44Encrypt(String plaintext, String privkeyHex, String pubkeyHex) {
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final convKey = nip44ConversationKey(privkeyHex, pubkeyHex);
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final nonce = Uint8List(32);
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final rng = Random.secure();
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for (var i = 0; i < 32; i++) nonce[i] = rng.nextInt(256);
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final keys = hkdf(convKey, nonce, [], 76);
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final chachaKey = keys.sublist(0, 32);
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final chachaNonce = keys.sublist(32, 44); // 12 bytes — RFC 7539
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final hmacKey = keys.sublist(44, 76);
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final padded = _pad(utf8.encode(plaintext));
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final chacha = ChaCha7539Engine()
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..init(true, ParametersWithIV(KeyParameter(chachaKey), chachaNonce));
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final ciphertext = Uint8List(padded.length);
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chacha.processBytes(padded, 0, padded.length, ciphertext, 0);
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final mac =
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Hmac(sha256, hmacKey).convert([...nonce, ...ciphertext]).bytes;
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return base64.encode(
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Uint8List.fromList([0x02, ...nonce, ...ciphertext, ...mac]),
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);
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}
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/// Decrypts a NIP-44 v2 base64 [payload]. Throws on HMAC failure or unknown version.
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String nip44Decrypt(String payload, String privkeyHex, String pubkeyHex) {
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final bytes = base64.decode(payload);
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if (bytes[0] != 0x02) {
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throw Exception('Unsupported NIP-44 version: ${bytes[0]}');
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}
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final nonce = bytes.sublist(1, 33);
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final mac = bytes.sublist(bytes.length - 32);
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final ciphertext = bytes.sublist(33, bytes.length - 32);
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final convKey = nip44ConversationKey(privkeyHex, pubkeyHex);
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final keys = hkdf(convKey, nonce, [], 76);
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final chachaKey = keys.sublist(0, 32);
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final chachaNonce = keys.sublist(32, 44);
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final hmacKey = keys.sublist(44, 76);
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final expectedMac =
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Hmac(sha256, hmacKey).convert([...nonce, ...ciphertext]).bytes;
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if (!_constantTimeEqual(mac, expectedMac)) {
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throw Exception('NIP-44 HMAC verification failed');
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}
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final chacha = ChaCha7539Engine()
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..init(true, ParametersWithIV(KeyParameter(chachaKey), chachaNonce));
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final plainPadded = Uint8List(ciphertext.length);
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chacha.processBytes(ciphertext, 0, ciphertext.length, plainPadded, 0);
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return utf8.decode(_unpad(plainPadded));
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}
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/// Minimal HKDF-SHA256: extract then expand.
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Uint8List hkdf(Uint8List ikm, List<int> salt, List<int> info, int length) {
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final prk = Hmac(sha256, salt).convert(ikm).bytes;
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final output = <int>[];
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var t = <int>[];
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var counter = 1;
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while (output.length < length) {
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t = Hmac(sha256, prk).convert([...t, ...info, counter]).bytes;
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output.addAll(t);
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counter++;
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}
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return Uint8List.fromList(output.sublist(0, length));
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}
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/// Decodes a hex string to bytes.
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Uint8List hexToBytes(String hex) {
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final result = Uint8List(hex.length ~/ 2);
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for (var i = 0; i < result.length; i++) {
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result[i] = int.parse(hex.substring(i * 2, i * 2 + 2), radix: 16);
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}
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return result;
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}
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int _calcPaddedLen(int n) {
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if (n <= 32) return 32;
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final nextPow = 1 << (n - 1).toRadixString(2).length;
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final chunk = nextPow <= 256 ? 32 : nextPow ~/ 8;
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return chunk * ((n + chunk - 1) ~/ chunk);
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}
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Uint8List _pad(List<int> plaintext) {
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final n = plaintext.length;
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final padded = Uint8List(_calcPaddedLen(n) + 2);
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padded[0] = (n >> 8) & 0xff;
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padded[1] = n & 0xff;
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padded.setRange(2, 2 + n, plaintext);
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return padded;
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}
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Uint8List _unpad(Uint8List padded) {
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final n = (padded[0] << 8) | padded[1];
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return padded.sublist(2, 2 + n);
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}
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bool _constantTimeEqual(List<int> a, List<int> b) {
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if (a.length != b.length) return false;
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var result = 0;
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for (var i = 0; i < a.length; i++) result |= a[i] ^ b[i];
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return result == 0;
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}
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