freezer/lib/ui/login_on_other_device.dart

import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

import 'package:crypto/crypto.dart';
import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:freezer/api/definitions.dart';
import 'package:freezer/settings.dart';
import 'package:freezer/utils.dart';
import 'package:pointycastle/export.dart' as pc;
import 'package:pointycastle/src/platform_check/platform_check.dart';
import 'package:encrypt/encrypt.dart' as encrypt;
import 'package:freezer/translations.i18n.dart';

class LoginOnOtherDevice extends StatefulWidget {
  const LoginOnOtherDevice({super.key});

  @override
  State<LoginOnOtherDevice> createState() => _LoginOnOtherDeviceState();
}

class _LoginOnOtherDeviceState extends State<LoginOnOtherDevice> {
  String _ipAddress = '';
  String _code = '';
  String? _error;
  bool _loading = false;
  bool _step2 = false;
  final GlobalKey<FormState> _formKey = GlobalKey();

  late final encrypt.Key key;

  void _doHandshake() async {
    if (!_formKey.currentState!.validate()) return;

    setState(() {
      _loading = true;
      _error = null;
    });

    // generate keypair
    final keyGen = pc.RSAKeyGenerator();
    final secureRandom = pc.SecureRandom('Fortuna')
      ..seed(pc.KeyParameter(
          Platform.instance.platformEntropySource().getBytes(32)));

    keyGen.init(pc.ParametersWithRandom(
        pc.RSAKeyGeneratorParameters(BigInt.parse('65537'), 2048, 64),
        secureRandom));

    final keyPair = keyGen.generateKeyPair();
    final privKey = keyPair.privateKey as pc.RSAPrivateKey;
    final pubKey = keyPair.publicKey as pc.RSAPublicKey;

    // initial handshake
    final hash = Hmac(sha512, Utils.splitDigits(int.parse(_code)))
        .convert(Utils.serializeBigInt(pubKey.exponent! ^ pubKey.modulus!))
        .toString();
    late final Response res;
    try {
      res = await Dio().post('http://$_ipAddress/',
          data: jsonEncode({
            '_': 'handshake',
            'pubKey': [
              base64.encode(Utils.serializeBigInt(pubKey.modulus!)),
              base64.encode(Utils.serializeBigInt(pubKey.exponent!))
            ],
            'hash': hash,
          }),
          options: Options(responseType: ResponseType.json));
    } on DioException catch (e) {
      if (e.type == DioExceptionType.badResponse) {
        if (e.response?.statusCode == 403) {
          setState(() {
            _error = 'Wrong code';
            _loading = false;
          });
          return;
        }
        final data = e.response?.data as Map?;
        if (data != null && data['message'] is String) {
          setState(() {
            _error = 'Request failed: ${data['message']}';
            _loading = false;
          });

          return;
        }
        setState(() {
          _error = 'Request failed: $e';
          _loading = false;
        });

        return;
      }
    }

    print(res);
    final data = res.data as Map;
    if (!data['ok']) {
      setState(() {
        _error = data['message'] as String? ?? 'Unknown server error';
        _loading = false;
      });

      return;
    }

    final encryptedKey = data['key'] as String;
    final encrypter = encrypt.Encrypter(encrypt.RSA(privateKey: privKey));
    key = encrypt.Key(Uint8List.fromList(
        encrypter.decryptBytes(encrypt.Encrypted.fromBase64(encryptedKey))));

    setState(() {
      _loading = false;
      _step2 = true;
    });
  }

  void _loginUsingArl(String arl) async {
    setState(() {
      _loading = true;
    });

    final encrypter = encrypt.Encrypter(
      encrypt.AES(key),
    );
    final iv = encrypt.IV.fromSecureRandom(16);
    final encryptedARL = encrypter.encrypt(arl, iv: iv);

    // send it over with dio
    late final Response res;
    try {
      res = await Dio().post('http://$_ipAddress/',
          data: jsonEncode({
            '_': 'arl',
            'arl': encryptedARL.base64,
            'iv': iv.base64,
          }),
          options: Options(responseType: ResponseType.json));
    } on DioException catch (e) {
      if (e.type == DioExceptionType.badResponse) {
        final data = e.response?.data as Map?;
        if (data != null && data['message'] is String) {
          setState(() {
            _error = 'Request failed: ${data['message']}';
            _loading = false;
          });
        }
      }
      setState(() {
        _error = 'Request failed: $e';
        _loading = false;
      });
      return;
    }

    if (!res.data['ok']) {
      setState(() {
        _error = res.data['message'] as String? ?? 'Unknown server error.';
        _loading = false;
      });
      return;
    }

    Navigator.pop(context);
    ScaffoldMessenger.of(context).snack('Logged in successfully!'.i18n);
  }

  void _cancel() async {
    if (_step2) {
      final hash =
          Hmac(sha512, key.bytes).convert(utf8.encode(_code)).toString();
      await Dio().post('http://$_ipAddress/',
          data: jsonEncode({'_': 'cancel', 'hash': hash}));
    }

    Navigator.pop(context);
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: Text('Login on other device'.i18n),
      content: _step2
          ? Column(mainAxisSize: MainAxisSize.min, children: [
              if (_error != null)
                Text(_error!, style: const TextStyle(color: Colors.red)),
              OutlinedButton(
                  onPressed:
                      _loading ? null : () => _loginUsingArl(settings.arl!),
                  child: Text('Login with current ARL'.i18n)),
            ])
          : Form(
              key: _formKey,
              child: Column(
                  mainAxisSize: MainAxisSize.min,
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    if (_error != null)
                      Text(_error!, style: const TextStyle(color: Colors.red)),
                    TextFormField(
                      validator: (value) {
                        value ??= '';
                        final p = value.split(':');
                        if (p.length != 2) return 'Invalid IP and Port';
                        final ip = p[0];
                        final port = int.tryParse(p[1]);
                        if (port == null || port > 65535) return 'Invalid port';
                        final ipParts = ip.split('.');
                        if (ipParts.length != 4) return 'Invalid IP';
                        for (final part in ipParts) {
                          final a = int.tryParse(part);
                          if (a == null || a < 0 || a > 255) {
                            return 'Invalid IP';
                          }
                        }

                        return null;
                      },
                      onChanged: (value) => _ipAddress = value,
                      decoration:
                          InputDecoration(label: Text('IP Address'.i18n)),
                    ),
                    TextFormField(
                      validator: (value) {
                        value ??= '';
                        if (value.length != 6 || int.tryParse(value) == null) {
                          return 'Invalid code';
                        }

                        return null;
                      },
                      onChanged: (value) => _code = value,
                      decoration: InputDecoration(label: Text('Code'.i18n)),
                    )
                  ]),
            ),
      actions: [
        if (!_step2)
          TextButton(
            onPressed: _loading ? null : _doHandshake,
            child: Text('Login'.i18n),
          ),
        TextButton(onPressed: _cancel, child: Text('Cancel'.i18n))
      ],
    );
  }
}