Fix remote control at X11 greeter by correctly grabbing display and X…

…authority from Xorg process.

Agent/Services/Linux/AppLauncherLinux.cs

@@ -1,27 +1,31 @@
-using Microsoft.AspNetCore.SignalR.Client;
+using Immense.RemoteControl.Shared;
+using Microsoft.AspNetCore.SignalR.Client;
 using Microsoft.Extensions.Logging;
 using Remotely.Agent.Interfaces;
+using Remotely.Shared.Extensions;
 using Remotely.Shared.Models;
 using Remotely.Shared.Services;
 using Remotely.Shared.Utilities;
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
-using System.Security.Cryptography;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
-using System.Web.Services.Description;
 
 namespace Remotely.Agent.Services.Linux;
 
 
 public class AppLauncherLinux : IAppLauncher
 {
-    private readonly string _rcBinaryPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Desktop", EnvironmentHelper.DesktopExecutableFileName);
-    private readonly IProcessInvoker _processInvoker;
     private readonly ConnectionInfo _connectionInfo;
     private readonly ILogger<AppLauncherLinux> _logger;
+    private readonly IProcessInvoker _processInvoker;
+
+    private readonly string _rcBinaryPath = Path.Combine(
+        AppDomain.CurrentDomain.BaseDirectory, 
+        "Desktop", 
+        EnvironmentHelper.DesktopExecutableFileName);
 
     public AppLauncherLinux(
         IConfigService configService,
@@ -34,78 +38,6 @@ public AppLauncherLinux(
     }
 
 
-    private int StartLinuxDesktopApp(string args)
-    {
-        var xauthority = GetXorgAuth();
-
-        var display = ":0";
-        var whoString = _processInvoker.InvokeProcessOutput("who", "")?.Trim();
-        var username = "";
-
-        if (!string.IsNullOrWhiteSpace(whoString))
-        {
-            try
-            {
-                var whoLine = whoString
-                    .Split('\n', StringSplitOptions.RemoveEmptyEntries)
-                    .First();
-
-                var whoSplit = whoLine.Split(' ', StringSplitOptions.RemoveEmptyEntries);
-                username = whoSplit[0];
-                display = whoSplit.Last().TrimStart('(').TrimEnd(')');
-                xauthority = $"/home/{username}/.Xauthority";
-                args = $"-u {username} {args}";
-            }
-            catch (Exception ex)
-            {
-                _logger.LogError(ex, "Error while getting current X11 user.");
-            }
-        }
-
-        var psi = new ProcessStartInfo()
-        {
-            FileName = "sudo",
-            Arguments = args
-        };
-
-        psi.Environment.Add("DISPLAY", display);
-        psi.Environment.Add("XAUTHORITY", xauthority);
-        _logger.LogInformation(
-            "Attempting to launch screen caster with username {username}, xauthority {xauthority}, display {display}, and args {args}.",
-            username,
-            xauthority,
-            display,
-            args);
-        return Process.Start(psi)?.Id ?? throw new InvalidOperationException("Failed to launch desktop app.");
-    }
-
-    private string GetXorgAuth()
-    {
-        try
-        {
-            var processes = _processInvoker.InvokeProcessOutput("ps", "-eaf")?.Split(Environment.NewLine);
-            if (processes?.Length > 0)
-            {
-                var xorgLine = processes.FirstOrDefault(x => x.Contains("xorg", StringComparison.OrdinalIgnoreCase));
-                if (!string.IsNullOrWhiteSpace(xorgLine))
-                {
-                    var xorgSplit = xorgLine?.Split(" ".ToCharArray(), StringSplitOptions.RemoveEmptyEntries).ToList();
-                    var authIndex = xorgSplit?.IndexOf("-auth");
-                    if (authIndex > -1 && xorgSplit?.Count >= authIndex + 1)
-                    {
-                        var auth = xorgSplit[(int)authIndex + 1];
-                        if (!string.IsNullOrWhiteSpace(auth))
-                        {
-                            return auth;
-                        }
-                    }
-                }
-            }
-        }
-        catch { }
-        return string.Empty;
-    }
-
     public async Task<int> LaunchChatService(string pipeName, string userConnectionId, string requesterName, string orgName, string orgId, HubConnection hubConnection)
     {
         try
@@ -197,4 +129,124 @@ public async Task RestartScreenCaster(string[] viewerIds, string sessionId, stri
             throw;
         }
     }
+
+    private int StartLinuxDesktopApp(string args)
+    {
+        var xdisplay = ":0";
+        var xauthority = string.Empty;
+
+        var xResult = TryGetXAuth("Xorg");
+
+        if (!xResult.IsSuccess)
+        {
+            // If running Wayland, this still ends up still being unusable.
+            // This X server will only provide a black screen with any apps
+            // launched within the display it's using, but the display won't
+            // show anything being rendered by the Wayland compositor.  It's
+            // better than simply crashing, though, so I'll leave it here
+            // until Wayland support is added.
+            xResult = TryGetXAuth("Xwayland");
+        }
+
+        if (xResult.IsSuccess)
+        {
+            xdisplay = xResult.Value.XDisplay;
+            xauthority = xResult.Value.XAuthority;
+        }
+        else
+        {
+            _logger.LogError("Failed to get X server auth.");
+        }
+
+        var whoString = _processInvoker.InvokeProcessOutput("who", "")?.Trim();
+        var username = "";
+
+        if (!string.IsNullOrWhiteSpace(whoString))
+        {
+            try
+            {
+                var whoLines = whoString.Split('\n', StringSplitOptions.RemoveEmptyEntries);
+
+                var whoLine = whoLines.FirstOrDefault(x =>
+                    Regex.IsMatch(
+                        x.Split(" ", StringSplitOptions.RemoveEmptyEntries).Last(),
+                        @"\(:[\d]*\)"));
+
+                if (!string.IsNullOrWhiteSpace(whoLine))
+                {
+                    var whoSplit = whoLine.Split(' ', StringSplitOptions.RemoveEmptyEntries);
+                    username = whoSplit[0];
+                    xdisplay = whoSplit.Last().TrimStart('(').TrimEnd(')');
+                    xauthority = $"/home/{username}/.Xauthority";
+                    args = $"-u {username} {args}";
+
+                }
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Error while getting current X11 user.");
+            }
+        }
+
+        var psi = new ProcessStartInfo()
+        {
+            FileName = "sudo",
+            Arguments = args
+        };
+
+        psi.Environment.Add("DISPLAY", xdisplay);
+        psi.Environment.Add("XAUTHORITY", xauthority);
+        _logger.LogInformation(
+            "Attempting to launch screen caster with username {username}, xauthority {xauthority}, display {display}, and args {args}.",
+            username,
+            xauthority,
+            xdisplay,
+            args);
+        return Process.Start(psi)?.Id ?? throw new InvalidOperationException("Failed to launch desktop app.");
+    }
+
+    private Result<XAuthInfo> TryGetXAuth(string xServerProcess)
+    {
+        try
+        {
+            var xdisplay = ":0";
+            var xauthority = string.Empty;
+
+            var xprocess = _processInvoker
+                .InvokeProcessOutput("ps", $"-C {xServerProcess} -f")
+                ?.Split(Environment.NewLine)
+                ?.FirstOrDefault(x => x.Contains(" -auth "));
+
+            if (string.IsNullOrWhiteSpace(xprocess))
+            {
+                _logger.LogInformation("{xServerProcess} process not found.", xServerProcess);
+                return Result.Fail<XAuthInfo>($"{xServerProcess} process not found.");
+            }
+
+            _logger.LogInformation("Resolved X server process: {xprocess}", xprocess);
+
+            var xprocSplit = xprocess
+                .Split(" ", StringSplitOptions.RemoveEmptyEntries)
+                .ToList();
+
+            var xProcIndex = xprocSplit.IndexWhere(x => x.EndsWith(xServerProcess));
+            if (xProcIndex > -1 && xprocSplit[xProcIndex + 1].StartsWith(":"))
+            {
+                xdisplay = xprocSplit[xProcIndex + 1];
+            }
+
+            var authIndex = xprocSplit.IndexOf("-auth");
+            if (authIndex > -1)
+            {
+                xauthority = xprocSplit[authIndex + 1];
+            }
+            return Result.Ok(new XAuthInfo(xdisplay, xauthority));
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error while geting X auth for {xServerProcess}.", xServerProcess);
+            return Result.Fail<XAuthInfo>($"Error while geting X auth for {xServerProcess}.");
+        }
+    }
+    private record XAuthInfo(string XDisplay, string XAuthority);
 }

Shared/Extensions/IEnumerableExtensions.cs

@@ -16,4 +16,18 @@ public static async IAsyncEnumerable<T> ToAsyncEnumerable<T>(this IEnumerable<T>
             await Task.Yield();
         }
     }
+
+    public static int IndexWhere<T>(this IEnumerable<T> source, Func<T, bool> predicate)
+    {
+        var index = 0;
+        foreach (var item in source)
+        {
+            if (predicate(item))
+            {
+                return index;
+            }
+            index++;
+        }
+        return -1;
+    }   
 }