PowerToys/src/modules/Hosts/Hosts.FuzzTests/FuzzTests.cs

// Copyright (c) Microsoft Corporation
// The Microsoft Corporation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Text.RegularExpressions;

using Hosts.Tests.Mocks;
using HostsUILib.Helpers;
using HostsUILib.Models;
using HostsUILib.Settings;
using Moq;

namespace Hosts.FuzzTests
{
    public class FuzzTests
    {
        private static Mock<IUserSettings> _userSettings;
        private static Mock<IElevationHelper> _elevationHelper;
        private static Mock<IBackupManager> _backupManager;

        // Case1： Fuzzing method for ValidIPv4
        public static void FuzzValidIPv4(ReadOnlySpan<byte> input)
        {
            try
            {
                string address = System.Text.Encoding.UTF8.GetString(input);
                bool isValid = ValidationHelper.ValidIPv4(address);
            }
            catch (Exception ex) when (ex is RegexMatchTimeoutException)
            {
                throw;
            }
        }

        // Case2: fuzzing method for ValidIPv6
        public static void FuzzValidIPv6(ReadOnlySpan<byte> input)
        {
            try
            {
                string address = System.Text.Encoding.UTF8.GetString(input);
                bool isValid = ValidationHelper.ValidIPv6(address);
            }
            catch (Exception ex) when (ex is RegexMatchTimeoutException)
            {
                throw;
            }
        }

        // Case3: fuzzing method for ValidHosts
        public static void FuzzValidHosts(ReadOnlySpan<byte> input)
        {
            try
            {
                string hosts = System.Text.Encoding.UTF8.GetString(input);
                bool isValid = ValidationHelper.ValidHosts(hosts, true);
            }
            catch (Exception ex) when (ex is RegexMatchTimeoutException)
            {
                // It's important to filter out any *expected* exceptions from our code here.
                // However, catching all exceptions is considered an anti-pattern because it may suppress legitimate
                // issues, such as a NullReferenceException thrown by our code. In this case, we still re-throw
                // the exception, as the ToJsonFromXmlOrCsvAsync method is not expected to throw any exceptions.
                throw;
            }
        }

        public static void FuzzWriteAsync(ReadOnlySpan<byte> data)
        {
            try
            {
                _userSettings = new Mock<IUserSettings>();
                _elevationHelper = new Mock<IElevationHelper>();
                _elevationHelper.Setup(m => m.IsElevated).Returns(true);
                _backupManager = new Mock<IBackupManager>();

                var fileSystem = new CustomMockFileSystem();
                var service = new HostsService(fileSystem, _userSettings.Object, _elevationHelper.Object, _backupManager.Object);

                string input = System.Text.Encoding.UTF8.GetString(data);

                // Since the WriteAsync method does not involve content parsing, we won't fuzz the additionalLines in the hosts file.
                string additionalLines = " ";
                string hosts = input;
                string address = input;
                string comments = input;
                var entries = new List<Entry>
                {
                    new Entry(1, hosts, address, comments, true),
                };

                // fuzzing WriteAsync
                _ = Task.Run(async () => await service.WriteAsync(additionalLines, entries));
            }
            catch (Exception ex) when (ex is ArgumentException)
            {
                throw;
            }
        }
    }
}