From f6a8c8dc87089360002c87e637164b04ab088773 Mon Sep 17 00:00:00 2001
From: Jan De Dobbeleer <jan.de.dobbeleer@gmail.com>
Date: Tue, 13 Feb 2024 09:55:49 +0100
Subject: [PATCH] feat(windows): parse app exec links

---
 src/platform/shell.go         |  5 ++--
 src/platform/shell_unix.go    |  6 ++---
 src/platform/shell_windows.go | 16 ++++++++++++
 src/platform/win32_windows.go | 46 +++++++++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/src/platform/shell.go b/src/platform/shell.go
index 05f5ebfd..f70a801a 100644
--- a/src/platform/shell.go
+++ b/src/platform/shell.go
@@ -12,7 +12,6 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strconv"
@@ -609,12 +608,14 @@ func (env *Shell) CommandPath(command string) string {
 		env.Debug(path)
 		return path
 	}
-	path, err := exec.LookPath(command)
+
+	path, err := env.LookPath(command)
 	if err == nil {
 		env.cmdCache.set(command, path)
 		env.Debug(path)
 		return path
 	}
+
 	env.Error(err)
 	return ""
 }
diff --git a/src/platform/shell_unix.go b/src/platform/shell_unix.go
index 156f1453..36105aa5 100644
--- a/src/platform/shell_unix.go
+++ b/src/platform/shell_unix.go
@@ -3,8 +3,8 @@
 package platform
 
 import (
-	"errors"
 	"os"
+	"os/exec"
 	"strconv"
 	"strings"
 	"time"
@@ -156,8 +156,8 @@ func (env *Shell) ConvertToLinuxPath(path string) string {
 	return path
 }
 
-func (env *Shell) LookWinAppPath(_ string) (string, error) {
-	return "", errors.New("not relevant")
+func (env *Shell) LookPath(command string) (string, error) {
+	return exec.LookPath(command)
 }
 
 func (env *Shell) DirIsWritable(path string) bool {
diff --git a/src/platform/shell_windows.go b/src/platform/shell_windows.go
index ae8d699c..9a94608b 100644
--- a/src/platform/shell_windows.go
+++ b/src/platform/shell_windows.go
@@ -4,6 +4,8 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"strings"
 	"syscall"
 	"time"
@@ -249,3 +251,17 @@ func (env *Shell) Connection(connectionType ConnectionType) (*Connection, error)
 	env.Error(fmt.Errorf("Network type '%s' not found", connectionType))
 	return nil, &NotImplemented{}
 }
+
+func (env *Shell) LookPath(command string) (string, error) {
+	winAppPath := filepath.Join(env.Getenv("LOCALAPPDATA"), `\Microsoft\WindowsApps\`, command)
+	if !strings.HasSuffix(winAppPath, ".exe") {
+		winAppPath += ".exe"
+	}
+
+	path, err := exec.LookPath(command)
+	if err == nil && path != winAppPath {
+		return path, nil
+	}
+
+	return readWinAppLink(winAppPath)
+}
diff --git a/src/platform/win32_windows.go b/src/platform/win32_windows.go
index 8705e8f9..1986d1be 100644
--- a/src/platform/win32_windows.go
+++ b/src/platform/win32_windows.go
@@ -350,3 +350,49 @@ func (env *Shell) Memory() (*Memory, error) {
 		PhysicalPercentUsed:     float64(memStat.MemoryLoad),
 	}, nil
 }
+
+// openSymlink calls CreateFile Windows API with FILE_FLAG_OPEN_REPARSE_POINT
+// parameter, so that Windows does not follow symlink, if path is a symlink.
+// openSymlink returns opened file handle.
+func openSymlink(path string) (syscall.Handle, error) {
+	p, err := syscall.UTF16PtrFromString(path)
+	if err != nil {
+		return 0, err
+	}
+
+	attrs := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS)
+	// Use FILE_FLAG_OPEN_REPARSE_POINT, otherwise CreateFile will follow symlink.
+	// See https://docs.microsoft.com/en-us/windows/desktop/FileIO/symbolic-link-effects-on-file-systems-functions#createfile-and-createfiletransacted
+	attrs |= syscall.FILE_FLAG_OPEN_REPARSE_POINT
+	h, err := syscall.CreateFile(p, 0, 0, nil, syscall.OPEN_EXISTING, attrs, 0)
+	if err != nil {
+		return 0, err
+	}
+
+	return h, nil
+}
+
+func readWinAppLink(path string) (string, error) {
+	h, err := openSymlink(path)
+	if err != nil {
+		return "", err
+	}
+
+	defer syscall.CloseHandle(h) //nolint: errcheck
+
+	rdbbuf := make([]byte, syscall.MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
+	var bytesReturned uint32
+	err = syscall.DeviceIoControl(h, syscall.FSCTL_GET_REPARSE_POINT, nil, 0, &rdbbuf[0], uint32(len(rdbbuf)), &bytesReturned, nil)
+	if err != nil {
+		return "", err
+	}
+
+	rdb := (*REPARSE_DATA_BUFFER)(unsafe.Pointer(&rdbbuf[0]))
+	rb := (*GenericDataBuffer)(unsafe.Pointer(&rdb.DUMMYUNIONNAME))
+	appExecLink := (*AppExecLinkReparseBuffer)(unsafe.Pointer(&rb.DataBuffer))
+	if appExecLink.Version != 3 {
+		return "", errors.New("unknown AppExecLink version")
+	}
+
+	return appExecLink.Path()
+}