yubioath-flutter/lib/oath/models.dart

/*
 * Copyright (C) 2022 Yubico.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import 'dart:typed_data';
import 'dart:convert';
import 'package:base32/base32.dart';
import 'package:logging/logging.dart';
import 'package:freezed_annotation/freezed_annotation.dart';
import 'package:flutter_gen/gen_l10n/app_localizations.dart';
import 'package:yubico_authenticator/app/logging.dart';

import '../core/models.dart';

part 'models.freezed.dart';
part 'models.g.dart';

const defaultPeriod = 30;
const defaultDigits = 6;
const defaultCounter = 0;
const defaultOathType = OathType.totp;
const defaultHashAlgorithm = HashAlgorithm.sha1;

final _log = Logger('oath.models');

enum HashAlgorithm {
  @JsonValue(0x01)
  sha1('SHA-1'),
  @JsonValue(0x02)
  sha256('SHA-256'),
  @JsonValue(0x03)
  sha512('SHA-512');

  final String displayName;
  const HashAlgorithm(this.displayName);
}

enum OathType {
  @JsonValue(0x10)
  hotp,
  @JsonValue(0x20)
  totp;

  const OathType();

  String getDisplayName(AppLocalizations l10n) => switch (this) {
        OathType.hotp => l10n.s_counter_based,
        OathType.totp => l10n.s_time_based
      };
}

enum KeystoreState { unknown, allowed, failed }

@freezed
class OathCredential with _$OathCredential {
  factory OathCredential(
      String deviceId,
      String id,
      String? issuer,
      String name,
      OathType oathType,
      int period,
      bool touchRequired) = _OathCredential;

  factory OathCredential.fromJson(Map<String, dynamic> json) =>
      _$OathCredentialFromJson(json);
}

@freezed
class OathCode with _$OathCode {
  factory OathCode(String value, int validFrom, int validTo) = _OathCode;

  factory OathCode.fromJson(Map<String, dynamic> json) =>
      _$OathCodeFromJson(json);
}

@freezed
class OathPair with _$OathPair {
  factory OathPair(OathCredential credential, OathCode? code) = _OathPair;

  factory OathPair.fromJson(Map<String, dynamic> json) =>
      _$OathPairFromJson(json);
}

@freezed
class OathState with _$OathState {
  factory OathState(
    String deviceId,
    Version version, {
    required bool hasKey,
    required bool remembered,
    required bool locked,
    required KeystoreState keystore,
  }) = _OathState;

  factory OathState.fromJson(Map<String, dynamic> json) =>
      _$OathStateFromJson(json);
}

@freezed
class CredentialData with _$CredentialData {
  const CredentialData._();

  factory CredentialData({
    String? issuer,
    required String name,
    required String secret,
    @Default(defaultOathType) OathType oathType,
    @Default(defaultHashAlgorithm) HashAlgorithm hashAlgorithm,
    @Default(defaultDigits) int digits,
    @Default(defaultPeriod) int period,
    @Default(defaultCounter) int counter,
  }) = _CredentialData;

  factory CredentialData.fromJson(Map<String, dynamic> json) =>
      _$CredentialDataFromJson(json);

  static List<CredentialData> multiFromUri(uri) {
    if (uri.scheme.toLowerCase() == 'otpauth-migration') {
      return CredentialData.fromMigration(uri);
    } else if (uri.scheme.toLowerCase() == 'otpauth') {
      return [CredentialData.fromUri(uri)];
    } else {
      throw ArgumentError('Invalid scheme');
    }
  }

  static List<CredentialData> fromMigration(uri) {
    List<dynamic> read(Uint8List bytes) {
      final index = bytes[0];
      final sublist1 = bytes.sublist(1, index + 1);
      final sublist2 = bytes.sublist(index + 1);
      return [sublist1, sublist2];
    }

    String b32Encode(Uint8List data) {
      final encodedData = base32.encode(data);
      return utf8.decode(encodedData.runes.toList());
    }

    final uriString = uri.toString();
    var data = Uint8List.fromList(
        base64.decode(Uri.decodeComponent(uriString.split('=')[1])));

    var credentials = <CredentialData>[];

    var tag = data[0];

    /*
      Assuming the credential(s) follow the format:
      cred = 0aLENGTH0aSECRET12NAME1aISSUER20ALGO28DIGITS30OATHxxx
      where xxx can be another cred.
      */
    while (tag == 10) {
      // 0a tag means new credential.

      // Extract secret, name, and issuer
      var secretTag = data[2];
      if (secretTag != 10) {
        // tag before secret is 0a hex
        throw ArgumentError('Invalid scheme, no secret tag');
      }
      data = data.sublist(3);
      final result1 = read(data);
      final secret = result1[0];
      data = result1[1];
      final decodedSecret = b32Encode(secret);

      var nameTag = data[0];
      if (nameTag != 18) {
        // tag before name is 12 hex
        throw ArgumentError('Invalid scheme, no name tag');
      }
      data = data.sublist(1);
      final result2 = read(data);
      final name = result2[0];
      data = result2[1];

      var issuerTag = data[0];
      List<int>? issuer;

      if (issuerTag == 26) {
        // tag before issuer is 1a hex, but issuer is optional.
        data = data.sublist(1);
        final result3 = read(data);
        issuer = result3[0];
        data = result3[1];
      }

      // Extract algorithm, number of digits, and oath type:
      var algoTag = data[0];
      if (algoTag != 32) {
        // tag before algo is 20 hex
        throw ArgumentError('Invalid scheme, no algo tag');
      }
      int algo = data[1];

      var digitsTag = data[2];
      if (digitsTag != 40) {
        // tag before digits is 28 hex
        throw ArgumentError('Invalid scheme, no digits tag');
      }
      var digits = data[3];

      var oathTag = data[4];
      if (oathTag != 48) {
        // tag before oath is 30 hex
        throw ArgumentError('Invalid scheme, no oath tag');
      }
      var oathType = data[5];

      int counter = defaultCounter;
      if (oathType == 1) {
        // if hotp, extract counter
        counter = data[7];
      }

      final credential = CredentialData(
        issuer:
            issuerTag != 26 ? null : utf8.decode(issuer!, allowMalformed: true),
        name: utf8.decode(name, allowMalformed: true),
        oathType: oathType == 1 ? OathType.hotp : OathType.totp,
        secret: decodedSecret,
        hashAlgorithm: algo == 1
            ? HashAlgorithm.sha1
            : (algo == 2 ? HashAlgorithm.sha256 : HashAlgorithm.sha512),
        digits: digits == 1 ? defaultDigits : 8,
        counter: counter,
      );

      credentials.add(credential);
      if (oathType == 1) {
        data = data.sublist(8);
      } else {
        data = data.sublist(6);
      }
      tag = data[0];
    }

    // Print all the extracted credentials
    for (var credential in credentials) {
      _log.debug(
          '${credential.issuer} (${credential.name}) ${credential.secret}');
    }

    return credentials;
  }

  factory CredentialData.fromUri(Uri uri) {
    final oathType = OathType.values.byName(uri.host.toLowerCase());
    final params = uri.queryParameters;
    String? issuer;
    String name = uri.pathSegments.join('/');
    final nameIndex = name.indexOf(':');
    if (nameIndex >= 0) {
      issuer = name.substring(0, nameIndex);
      name = name.substring(nameIndex + 1);
    }
    return CredentialData(
      issuer: params['issuer'] ?? issuer,
      name: name,
      oathType: oathType,
      hashAlgorithm: HashAlgorithm.values
          .byName(params['algorithm']?.toLowerCase() ?? 'sha1'),
      secret: params['secret']!,
      digits: int.tryParse(params['digits'] ?? '') ?? defaultDigits,
      period: int.tryParse(params['period'] ?? '') ?? defaultPeriod,
      counter: int.tryParse(params['counter'] ?? '') ?? defaultCounter,
    );
  }

  Uri toUri() => Uri(
        scheme: 'otpauth',
        host: oathType.name,
        path: issuer != null ? '$issuer:$name' : name,
        queryParameters: {
          'secret': secret,
          if (oathType == OathType.totp) 'period': period.toString(),
          if (oathType == OathType.hotp) 'counter': counter.toString(),
          if (issuer != null) 'issuer': issuer!,
          if (digits != 6) 'digits': digits.toString(),
          if (hashAlgorithm != HashAlgorithm.sha1)
            'algorithm': hashAlgorithm.name,
        },
      );
}