WindowsSystemIdentityFactory.cs

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using System;
using System.DirectoryServices.AccountManagement;
using System.Runtime.Versioning;
using System.Security.Principal;
using System.Threading;
using System.Threading.Tasks;
 
using Microsoft.Extensions.Logging;
using Microsoft.Win32.SafeHandles;
 
using Tgstation.Server.Host.IO;
using Tgstation.Server.Host.Models;
using Tgstation.Server.Host.System;
 
namespace Tgstation.Server.Host.Security
{
    [SupportedOSPlatform("windows")]
    sealed class WindowsSystemIdentityFactory : ISystemIdentityFactory
    {
        readonly ILogger<WindowsSystemIdentityFactory> logger;
 
        static void GetUserAndDomainName(string input, out string username, out string domainName)
        {
            var splits = input.Split('\\');
            username = splits.Length > 1 ? splits[1] : splits[0];
            domainName = splits.Length > 1 ? splits[0] : null;
        }
 
        public WindowsSystemIdentityFactory(ILogger<WindowsSystemIdentityFactory> logger)
        {
            this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
        }
 
        public ISystemIdentity GetCurrent() => new WindowsSystemIdentity(WindowsIdentity.GetCurrent());
 
        public Task<ISystemIdentity> CreateSystemIdentity(User user, CancellationToken cancellationToken) => Task.Factory.StartNew(
            () =>
            {
                ArgumentNullException.ThrowIfNull(user);
 
                if (user.SystemIdentifier == null)
                    throw new InvalidOperationException("User's SystemIdentifier must not be null!");
 
                PrincipalContext pc = null;
                UserPrincipal principal = null;
 
                GetUserAndDomainName(user.SystemIdentifier, out _, out var domainName);
 
                bool TryGetPrincipalFromContextType(ContextType contextType)
                {
                    try
                    {
                        pc = domainName != null
                            ? new PrincipalContext(contextType, domainName)
                            : new PrincipalContext(contextType);
                        cancellationToken.ThrowIfCancellationRequested();
                        principal = UserPrincipal.FindByIdentity(pc, user.SystemIdentifier);
                    }
                    catch (OperationCanceledException)
                    {
                        throw;
                    }
                    catch (Exception ex)
                    {
                        logger.LogDebug(
                            ex,
                            "Error loading user for context type {contextType} and principal \"{domainName}\"!",
                            contextType,
                            domainName);
                    }
                    finally
                    {
                        if (principal == null)
                        {
                            pc?.Dispose();
                            cancellationToken.ThrowIfCancellationRequested();
                        }
                    }
 
                    return principal != null;
                }
 
                if (!TryGetPrincipalFromContextType(ContextType.Machine) && !TryGetPrincipalFromContextType(ContextType.Domain))
                    return null;
                return (ISystemIdentity)new WindowsSystemIdentity(principal);
            },
            cancellationToken,
            DefaultIOManager.BlockingTaskCreationOptions,
            TaskScheduler.Current);
 
        public Task<ISystemIdentity> CreateSystemIdentity(string username, string password, CancellationToken cancellationToken) => Task.Factory.StartNew(
            () =>
            {
                ArgumentNullException.ThrowIfNull(username);
                ArgumentNullException.ThrowIfNull(password);
 
                var originalUsername = username;
                GetUserAndDomainName(originalUsername, out username, out var domainName);
 
                var res = NativeMethods.LogonUser(username, domainName, password, 3 /*LOGON32_LOGON_NETWORK*/, 0 /*LOGON32_PROVIDER_DEFAULT*/, out var token);
                if (!res)
                {
                    logger.LogTrace("Invalid system identity/password combo for username {0}!", originalUsername);
                    return null;
                }
 
                logger.LogTrace("Authenticated username {0} using system identity!", originalUsername);
 
                // checked internally, windows identity always duplicates the handle when constructed
                using var handle = new SafeAccessTokenHandle(token);
                return (ISystemIdentity)new WindowsSystemIdentity(
                    new WindowsIdentity(handle.DangerousGetHandle()));   // https://github.com/dotnet/corefx/blob/6ed61acebe3214fcf79b4274f2bb9b55c0604a4d/src/System.Security.Principal.Windows/src/System/Security/Principal/WindowsIdentity.cs#L271
            },
            cancellationToken,
            DefaultIOManager.BlockingTaskCreationOptions,
            TaskScheduler.Current);
    }
}