lua: validate script extension after resolving symlinks

app/geodata/download_test.go

@@ -40,11 +40,18 @@ func TestDownloadOneLuaGuard(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			data, err := os.ReadFile(staged.temp)
+			tx, err := swapAll([]stage{staged})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if err := tx.commit(); err != nil {
+				t.Fatal(err)
+			}
+			data, err := os.ReadFile(staged.target)
 			if err != nil || string(data) != luaGuardHeader+tc.body {
 				t.Fatalf("downloaded data = % x, %v", data, err)
 			}
-			program, err := xlua.Compile(staged.temp)
+			program, err := xlua.Compile(staged.target)
 			var syntaxErr *parse.Error
 			if program != nil || !errors.As(err, &syntaxErr) || syntaxErr.Pos.Line != 1 || syntaxErr.Pos.Column != 1 {
 				t.Fatalf("want Lua rejection at the first byte, got %v, %v", program, err)
@@ -57,7 +64,7 @@ func TestDownloadOneLuaGuard(t *testing.T) {
 				if len(list.Entry) != 1 || list.Entry[0].Code != tc.code {
 					t.Fatalf("header changed geodata: %v", &list)
 				}
-				if _, err := commongeodata.ParseDomainRules([]string{"ext:" + filepath.Base(staged.temp) + ":" + tc.code}, commongeodata.Domain_Full); err != nil {
+				if _, err := commongeodata.ParseDomainRules([]string{"ext:" + filepath.Base(staged.target) + ":" + tc.code}, commongeodata.Domain_Full); err != nil {
 					t.Fatalf("geodata loader rejected the header: %v", err)
 				}
 			}

common/lua/program_test.go

@@ -21,10 +21,7 @@ import (
 )
 
 func TestProgramStatesAreIndependent(t *testing.T) {
-	path := filepath.Join(t.TempDir(), "state.lua")
+	path := writeTestScript(t, "value = (value or 0) + 1")
-	if err := os.WriteFile(path, []byte("value = (value or 0) + 1"), 0o600); err != nil {
-		t.Fatal(err)
-	}
 	program, err := Compile(path)
 	if err != nil {
 		t.Fatal(err)
@@ -191,6 +188,22 @@ func TestCompileInlineDiagnostics(t *testing.T) {
 }
 */
 
+func TestCompileFileExtension(t *testing.T) {
+	for _, name := range []string{"script", "script.dat", "script.lua.txt", "script.LUA"} {
+		path := filepath.Join(t.TempDir(), name)
+		if err := os.WriteFile(path, []byte("value = 42"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		if program, err := Compile(path); program != nil || err == nil || !strings.Contains(err.Error(), "Lua file extension must be .lua") {
+			t.Fatalf("Compile(%q) = %v, %v; want nil program and .lua extension error", path, program, err)
+		}
+	}
+	path := writeTestScript(t, "value = 42") + string(filepath.Separator) + "."
+	if program, err := Compile(path); program == nil || err != nil {
+		t.Fatalf("Compile(%q) = %v, %v; want acceptance of the resolved .lua path", path, program, err)
+	}
+}
+
 func TestCompileRejectsReadFailure(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "unreadable.lua")
 	if err := os.WriteFile(path, []byte("value = 42"), 0o600); err != nil {
@@ -255,6 +268,10 @@ func writeTestScript(t *testing.T, code string) string {
 	if err := os.WriteFile(path, []byte(code), 0o600); err != nil {
 		t.Fatal(err)
 	}
+	path, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		t.Fatal(err)
+	}
 	return path
 }
 

common/platform/platform.go

@@ -93,7 +93,7 @@ func GetConfDirPath() string {
 	return configPath
 }
 
-// ResolveLuaFile finds a local Lua script and returns its absolute path.
+// ResolveLuaFile finds a local .lua script and returns its resolved absolute path.
 // Relative paths: XRAY_LOCATION_CONFDIR > XRAY_LOCATION_CONFIG > working dir > executable dir.
 func ResolveLuaFile(path string) (string, error) {
 	if path == "" {
@@ -113,7 +113,22 @@ func ResolveLuaFile(path string) (string, error) {
 			}
 		}
 	}
-	return resolveFile(paths)
+	path, err := resolveFile(paths)
+	if err != nil {
+		return "", err
+	}
+	return resolveLuaTarget(path)
+}
+
+func resolveLuaTarget(path string) (string, error) {
+	path, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		return "", fmt.Errorf("failed to resolve Lua file symlinks: %w", err)
+	}
+	if filepath.Ext(path) != ".lua" {
+		return "", errors.New("Lua file extension must be .lua")
+	}
+	return path, nil
 }
 
 func resolveFile(paths []string) (string, error) {

common/platform/platform_test.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 
 	"github.com/xtls/xray-core/common"
@@ -88,6 +89,10 @@ func TestResolveLuaFile(t *testing.T) {
 	for _, path := range paths[:3] {
 		common.Must(os.WriteFile(path, nil, 0o600))
 	}
+	for i, path := range paths {
+		paths[i], err = filepath.EvalSymlinks(path)
+		common.Must(err)
+	}
 	if got, err := ResolveLuaFile(paths[2]); err != nil || got != paths[2] {
 		t.Fatalf("absolute path = %q, %v; want %q", got, err, paths[2])
 	}
@@ -115,3 +120,35 @@ func TestResolveLuaFile(t *testing.T) {
 		}
 	}
 }
+
+func TestResolveLuaFileSymlink(t *testing.T) {
+	for _, tc := range []struct {
+		link, target string
+		valid        bool
+	}{
+		{"alias.lua", "data.dat", false},
+		{"alias.dat", "script.lua", true},
+	} {
+		t.Run(tc.link, func(t *testing.T) {
+			dir, err := filepath.EvalSymlinks(t.TempDir())
+			common.Must(err)
+			target := filepath.Join(dir, tc.target)
+			common.Must(os.WriteFile(target, nil, 0o600))
+			link := filepath.Join(dir, tc.link)
+			if err := os.Symlink(tc.target, link); err != nil {
+				if runtime.GOOS == "windows" {
+					t.Skipf("cannot create symlinks: %v", err)
+				}
+				t.Fatal(err)
+			}
+			got, err := ResolveLuaFile(link)
+			if tc.valid {
+				if err != nil || got != target {
+					t.Fatalf("ResolveLuaFile(%q) = %q, %v; want %q", link, got, err, target)
+				}
+			} else if err == nil || got != "" || !strings.Contains(err.Error(), "Lua file extension must be .lua") {
+				t.Fatalf("ResolveLuaFile(%q) = %q, %v; want .lua extension error", link, got, err)
+			}
+		})
+	}
+}