src/WebhookServer.Core/Execution/Native/InteractiveProcessLauncher.cs

@@ -43,7 +43,12 @@ internal static class InteractiveProcessLauncher
         }
     }
 
-    public static LaunchResult Launch(LaunchOptions opts)
+    /// <summary>
+    /// Launch into the session of whoever is logged in at the keyboard. Lets hooks
+    /// pop UI on the user's desktop. Caller must be SYSTEM (only SYSTEM can call
+    /// WTSQueryUserToken).
+    /// </summary>
+    public static LaunchResult LaunchAsActiveConsoleUser(LaunchOptions opts)
     {
         var sessionId = WTSGetActiveConsoleSessionId();
         if (sessionId == INVALID_SESSION_ID)
@@ -52,6 +57,44 @@ internal static class InteractiveProcessLauncher
         if (!WTSQueryUserToken(sessionId, out var userToken))
             throw LastError("WTSQueryUserToken (must run as SYSTEM)");
 
+        try { return LaunchWithToken(userToken, opts); }
+        finally { CloseHandle(userToken); }
+    }
+
+    /// <summary>
+    /// Launch under a username/password by calling LogonUser to obtain a token.
+    /// Used instead of psi.UserName/Password because CreateProcessWithLogonW (what
+    /// .NET uses under the hood) refuses to run when the caller is SYSTEM.
+    /// Tries interactive logon first, then batch.
+    /// </summary>
+    public static LaunchResult LaunchAsSpecificUser(string username, string password, string? domain, LaunchOptions opts)
+    {
+        var resolvedDomain = NormalizeDomain(domain);
+        IntPtr token;
+        if (!LogonUser(username, resolvedDomain, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, out token))
+        {
+            if (!LogonUser(username, resolvedDomain, password, LOGON32_LOGON_BATCH, LOGON32_PROVIDER_DEFAULT, out token))
+            {
+                var who = string.IsNullOrEmpty(domain) ? username : $"{domain}\\{username}";
+                throw LastError($"LogonUser ({who})");
+            }
+        }
+
+        try { return LaunchWithToken(token, opts); }
+        finally { CloseHandle(token); }
+    }
+
+    private static string? NormalizeDomain(string? domain)
+    {
+        if (string.IsNullOrEmpty(domain)) return null;
+        // "." is a common shorthand for "this machine"; LogonUser wants the actual
+        // machine name or null for local accounts.
+        if (domain == ".") return Environment.MachineName;
+        return domain;
+    }
+
+    private static LaunchResult LaunchWithToken(IntPtr sourceToken, LaunchOptions opts)
+    {
         IntPtr primaryToken = IntPtr.Zero;
         IntPtr envBlock = IntPtr.Zero;
         IntPtr stdoutRead = IntPtr.Zero, stdoutWrite = IntPtr.Zero;
@@ -62,7 +105,7 @@ internal static class InteractiveProcessLauncher
 
         try
         {
-            if (!DuplicateTokenEx(userToken, (uint)MAXIMUM_ALLOWED, IntPtr.Zero,
+            if (!DuplicateTokenEx(sourceToken, (uint)MAXIMUM_ALLOWED, IntPtr.Zero,
                     SECURITY_IMPERSONATION_LEVEL.SecurityImpersonation,
                     TOKEN_TYPE.TokenPrimary, out primaryToken))
                 throw LastError("DuplicateTokenEx");
@@ -140,7 +183,6 @@ internal static class InteractiveProcessLauncher
         }
         finally
         {
-            if (userToken != IntPtr.Zero) CloseHandle(userToken);
             if (primaryToken != IntPtr.Zero) CloseHandle(primaryToken);
             if (envBlock != IntPtr.Zero) DestroyEnvironmentBlock(envBlock);
             if (!succeeded)

src/WebhookServer.Core/Execution/Native/NativeMethods.cs

@@ -79,6 +79,19 @@ internal static class NativeMethods
         public uint dwThreadId;
     }
 
+    public const int LOGON32_LOGON_INTERACTIVE = 2;
+    public const int LOGON32_LOGON_BATCH = 4;
+    public const int LOGON32_PROVIDER_DEFAULT = 0;
+
+    [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+    public static extern bool LogonUser(
+        string lpszUsername,
+        string? lpszDomain,
+        string lpszPassword,
+        int dwLogonType,
+        int dwLogonProvider,
+        out IntPtr phToken);
+
     [DllImport("kernel32.dll")]
     public static extern uint WTSGetActiveConsoleSessionId();
 

src/WebhookServer.Core/Execution/ProcessExecutor.cs

@@ -1,6 +1,5 @@
 using System.Diagnostics;
 using System.Runtime.Versioning;
-using System.Security;
 using System.Text;
 using WebhookServer.Core.Execution.Native;
 using WebhookServer.Core.Models;
@@ -19,7 +18,8 @@ public sealed class ProcessExecutor : IExecutor
         var mode = endpoint.RunAs?.Mode ?? RunAsMode.Service;
         return mode switch
         {
-            RunAsMode.InteractiveUser => await RunInteractiveAsync(endpoint, ctx, startedAt, ct).ConfigureAwait(false),
+            RunAsMode.InteractiveUser => await RunWithLauncherAsync(endpoint, ctx, startedAt, useActiveConsole: true, ct).ConfigureAwait(false),
+            RunAsMode.SpecificUser => await RunWithLauncherAsync(endpoint, ctx, startedAt, useActiveConsole: false, ct).ConfigureAwait(false),
             _ => await RunWithProcessAsync(endpoint, ctx, startedAt, ct).ConfigureAwait(false),
         };
     }
@@ -32,12 +32,6 @@ public sealed class ProcessExecutor : IExecutor
         foreach (var (k, v) in envVars)
             psi.Environment[k] = v;
 
-        if (endpoint.RunAs?.Mode == RunAsMode.SpecificUser)
-        {
-            try { ApplySpecificUser(psi, endpoint.RunAs); }
-            catch (Exception ex) { return Failed(ctx.RunId, startedAt, ex.Message); }
-        }
-
         using var process = new Process { StartInfo = psi, EnableRaisingEvents = true };
 
         try
@@ -107,27 +101,42 @@ public sealed class ProcessExecutor : IExecutor
         };
     }
 
-    // ---------------- Interactive path: launches into the active console session. ----------------
+    // ---------------- Token-based path: InteractiveUser + SpecificUser. ----------------
 
-    private static async Task<ExecutionResult> RunInteractiveAsync(EndpointConfig endpoint, ExecutionContext ctx, DateTimeOffset startedAt, CancellationToken ct)
+    private static async Task<ExecutionResult> RunWithLauncherAsync(EndpointConfig endpoint, ExecutionContext ctx, DateTimeOffset startedAt, bool useActiveConsole, CancellationToken ct)
     {
         var (psi, envVars) = BuildStartInfo(endpoint, ctx);
+        var opts = new InteractiveProcessLauncher.LaunchOptions
+        {
+            FileName = psi.FileName,
+            Arguments = psi.ArgumentList.ToList(),
+            WorkingDirectory = string.IsNullOrEmpty(psi.WorkingDirectory) ? null : psi.WorkingDirectory,
+            ExtraEnvVars = envVars,
+            StdinBytes = endpoint.DataPassing.StdinJson ? ctx.BodyBytes : null,
+        };
 
         InteractiveProcessLauncher.LaunchResult launch;
         try
         {
-            launch = InteractiveProcessLauncher.Launch(new InteractiveProcessLauncher.LaunchOptions
+            if (useActiveConsole)
             {
-                FileName = psi.FileName,
-                Arguments = psi.ArgumentList.ToList(),
-                WorkingDirectory = string.IsNullOrEmpty(psi.WorkingDirectory) ? null : psi.WorkingDirectory,
-                ExtraEnvVars = envVars,
-                StdinBytes = endpoint.DataPassing.StdinJson ? ctx.BodyBytes : null,
-            });
+                launch = InteractiveProcessLauncher.LaunchAsActiveConsoleUser(opts);
+            }
+            else
+            {
+                var runAs = endpoint.RunAs ?? throw new InvalidOperationException("RunAs config missing");
+                if (string.IsNullOrEmpty(runAs.Username))
+                    return Failed(ctx.RunId, startedAt, "RunAs.Username is required when Mode = SpecificUser");
+                if (runAs.Password?.Plaintext is not { Length: > 0 } password)
+                    return Failed(ctx.RunId, startedAt, "RunAs.Password is required when Mode = SpecificUser");
+
+                var (domain, user) = ParseUserSpec(runAs.Username);
+                launch = InteractiveProcessLauncher.LaunchAsSpecificUser(user, password, domain, opts);
+            }
         }
         catch (Exception ex)
         {
-            return Failed(ctx.RunId, startedAt, $"interactive launch error: {ex.Message}");
+            return Failed(ctx.RunId, startedAt, $"launch error: {ex.Message}");
         }
 
         try
@@ -261,25 +270,6 @@ public sealed class ProcessExecutor : IExecutor
         return endpoint.InlineCommand ?? "";
     }
 
-    private static void ApplySpecificUser(ProcessStartInfo psi, RunAsConfig runAs)
-    {
-        if (string.IsNullOrEmpty(runAs.Username))
-            throw new InvalidOperationException("RunAs.Username is required when Mode = SpecificUser");
-        if (runAs.Password?.Plaintext is not { Length: > 0 } password)
-            throw new InvalidOperationException("RunAs.Password is required when Mode = SpecificUser");
-
-        var (domain, user) = ParseUserSpec(runAs.Username);
-        psi.UserName = user;
-        if (!string.IsNullOrEmpty(domain)) psi.Domain = domain;
-
-        var ss = new SecureString();
-        foreach (var ch in password) ss.AppendChar(ch);
-        ss.MakeReadOnly();
-        psi.Password = ss;
-
-        psi.LoadUserProfile = runAs.LoadProfile;
-    }
-
     private static (string Domain, string User) ParseUserSpec(string spec)
     {
         var bs = spec.IndexOf('\\');