Merge pull request #4490 from Flow-Launcher/fix-shell-link-buffer-issue

Program Plugin: Refactor ShellLinkReader and fix argument/description retrieval

Author: DavidGBrett

Plugins/Flow.Launcher.Plugin.Program/NativeMethods.txt

@@ -10,4 +10,13 @@ SLR_FLAGS
 IShellItem
 SHCreateItemFromParsingName
 IShellLinkW
-CoTaskMemFree
+ShellLink
+CoTaskMemFree
+IPropertyStore
+PROPERTYKEY
+PROPVARIANT
+PKEY_Link_Arguments
+PropVariantClear
+VARENUM
+INFOTIPSIZE
+MAX_PATH

Plugins/Flow.Launcher.Plugin.Program/Programs/ShellLinkHelper.cs

@@ -0,0 +1,4 @@
+namespace Flow.Launcher.Plugin.Program.Programs
+{
+    public readonly record struct ShellLinkReadResult(string TargetPath, string Description, string Arguments);
+}

Plugins/Flow.Launcher.Plugin.Program/Programs/ShellLinkReadResult.cs

@@ -0,0 +1,131 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.ComTypes;
+using Flow.Launcher.Plugin.Program.Logger;
+using Windows.Win32;
+using Windows.Win32.Foundation;
+using Windows.Win32.System.Com;
+using Windows.Win32.System.Com.StructuredStorage;
+using Windows.Win32.System.Variant;
+using Windows.Win32.UI.Shell;
+using Windows.Win32.UI.Shell.PropertiesSystem;
+using Windows.Win32.Storage.FileSystem;
+
+namespace Flow.Launcher.Plugin.Program.Programs
+{
+    public static class ShellLinkReader
+    {
+        // Retrieves the target path, arguments, and description from a shell link
+        public static ShellLinkReadResult Read(string path)
+        {
+            var link = new ShellLink();
+            try
+            {
+                try
+                {
+                    ((IPersistFile)link).Load(path, (int)STGM.STGM_READ);
+                    var hwnd = new HWND(IntPtr.Zero);
+                    // Use SLR_NO_UI to avoid showing any UI during resolution, like Problem with Shortcut dialogs
+                    // https://learn.microsoft.com/en-us/windows/win32/api/shobjidl_core/nf-shobjidl_core-ishelllinka-resolve
+                    ((IShellLinkW)link).Resolve(hwnd, (uint)SLR_FLAGS.SLR_NO_UI);
+                }
+                catch (COMException e)
+                {
+                    ProgramLogger.LogException(
+                        $"|ShellLinkReader|Read|{path}|Error occurred while loading or resolving shell link",
+                        e
+                    );
+                    return new ShellLinkReadResult(string.Empty, string.Empty, string.Empty);
+                }
+
+                var target = retrieveTargetPath((IShellLinkW)link, path);
+                var description = retrieveDescription((IShellLinkW)link, path);
+                var arguments = retrieveArguments((IPropertyStore)link, path);
+                return new ShellLinkReadResult(target, description, arguments);
+            }
+            finally
+            {
+                // release unmanaged memory
+                Marshal.ReleaseComObject(link);
+            }
+        }
+
+        private static unsafe string retrieveTargetPath(IShellLinkW shellLink, string path)
+        {
+            var data = new WIN32_FIND_DATAW();
+            try
+            {
+                Span<char> targetBuffer = stackalloc char[(int)PInvoke.MAX_PATH];
+                targetBuffer.Clear();
+                fixed (char* targetBufferPtr = targetBuffer)
+                {
+                    shellLink.GetPath((PWSTR)targetBufferPtr, (int)PInvoke.MAX_PATH, &data, (uint)SLGP_FLAGS.SLGP_SHORTPATH);
+                    return MemoryMarshal.CreateReadOnlySpanFromNullTerminated(targetBufferPtr).ToString();
+                }
+            }
+            catch (COMException e)
+            {
+                ProgramLogger.LogException($"|ShellLinkReader|retrieveTargetPath|{path}" +
+                    "|Error occurred while getting program target path from shell link", e);
+                return string.Empty;
+            }
+        }
+
+        private static unsafe string retrieveDescription(IShellLinkW shellLink, string path)
+        {
+            try
+            {
+                Span<char> descriptionBuffer = stackalloc char[(int)PInvoke.INFOTIPSIZE];
+                descriptionBuffer.Clear();
+                fixed (char* descriptionBufferPtr = descriptionBuffer)
+                {
+                    shellLink.GetDescription(descriptionBufferPtr, (int)PInvoke.INFOTIPSIZE);
+                    return MemoryMarshal.CreateReadOnlySpanFromNullTerminated(descriptionBufferPtr).ToString();
+                }
+            }
+            catch (COMException e)
+            {
+                // C:\\ProgramData\\Microsoft\\Windows\\Start Menu\\Programs\\MiracastView.lnk always cause exception
+                ProgramLogger.LogException(
+                    $"|ShellLinkReader|retrieveDescription|{path}" +
+                    "|Error caused likely due to trying to get the description of the program",
+                    e
+                );
+                return string.Empty;
+            }
+        }
+
+        private static string retrieveArguments(IPropertyStore shellLinkPropertyStore, string path)
+        {
+            PROPVARIANT argumentsProperty = new PROPVARIANT();
+
+            try
+            {
+                var argumentsKey = PInvoke.PKEY_Link_Arguments;
+                shellLinkPropertyStore.GetValue(in argumentsKey, out argumentsProperty);
+
+                // CsWin32 preserves native C unions, so nested union fields are generated as "Anonymous".
+                // see structure at https://learn.microsoft.com/en-ie/windows/win32/api/propidlbase/ns-propidlbase-propvariant#syntax
+                var propVariantHeader = argumentsProperty.Anonymous.Anonymous;
+                var propVariantValueUnion = propVariantHeader.Anonymous;
+                var propVariantType = propVariantHeader.vt;
+                
+                return propVariantType switch
+                {
+                    VARENUM.VT_EMPTY => string.Empty,
+                    VARENUM.VT_LPWSTR => propVariantValueUnion.pwszVal.ToString(),
+                    _ => string.Empty
+                };
+            }
+            catch (COMException e)
+            {
+                ProgramLogger.LogException($"|ShellLinkReader|retrieveArguments|{path}|Error occurred while getting program arguments", e);
+                return string.Empty;
+            }
+            finally
+            {
+                PInvoke.PropVariantClear(ref argumentsProperty);
+            }
+        }
+    }
+}

Plugins/Flow.Launcher.Plugin.Program/Programs/ShellLinkReader.cs

@@ -3,7 +3,6 @@
 using System.IO;
 using System.Linq;
 using System.Security;
-using System.Text;
 using System.Threading.Tasks;
 using Microsoft.Win32;
 using Flow.Launcher.Plugin.Program.Logger;
@@ -336,24 +335,22 @@ private static Win32 LnkProgram(string path)
         {
             var program = Win32Program(path);
             try
-            {
-                const int MAX_PATH = 260;
-                StringBuilder buffer = new StringBuilder(MAX_PATH);
-                ShellLinkHelper _helper = new ShellLinkHelper();
-                string target = _helper.retrieveTargetPath(path);
+            {   
+                var shellLink = ShellLinkReader.Read(path);
+                string target = shellLink.TargetPath;
 
                 if (!string.IsNullOrEmpty(target) && File.Exists(target))
                 {
                     program.LnkResolvedPath = Path.GetFullPath(target);
                     program.ExecutableName = Path.GetFileNameWithoutExtension(target);
 
-                    var args = _helper.arguments;
+                    var args = shellLink.Arguments;
                     if (!string.IsNullOrEmpty(args))
                     {
                         program.Args = args;
                     }
 
-                    var description = _helper.description;
+                    var description = shellLink.Description;
                     if (!string.IsNullOrEmpty(description))
                     {
                         program.Description = description;