Line obfuscator optimization

line_obfuscator.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"go/ast"
+	"go/token"
 	mathrand "math/rand"
 	"strings"
 
@@ -79,11 +80,17 @@ func findBuildTags(commentGroups []*ast.CommentGroup) (buildTags []string) {
 	return buildTags
 }
 
-func transformLineInfo(fileIndex int, file *ast.File) ([]string, *ast.File) {
+func transformLineInfo(fileName string, file *ast.File, fset *token.FileSet) ([]string, *ast.File) {
 	// Save build tags and add file name leak protection
 	extraComments := append(findBuildTags(file.Comments), "", "//line :1")
-
 	file.Comments = nil
+
+	fileSeed := hashWithAsInt64(buildInfo.buildID, fileName)
+	fileRand := mathrand.New(mathrand.NewSource(fileSeed))
+
+	newLines := fileRand.Perm(fset.File(file.Package).LineCount())
+
+	funcCounter := 0
 	pre := func(cursor *astutil.Cursor) bool {
 		node := cursor.Node()
 		clearNodeComments(node)
@@ -98,10 +105,9 @@ func transformLineInfo(fileIndex int, file *ast.File) ([]string, *ast.File) {
 			return true
 		}
 
-		// TODO: Optimize the generated values of line numbers to reduce space usage.
+		comment := &ast.Comment{Text: fmt.Sprintf("//line %c.go:%d", nameCharset[fileRand.Intn(len(nameCharset))], 1+newLines[funcCounter])}
-		linePos := hashWithAsUint64(buildInfo.buildID, fmt.Sprintf("%d:%s", fileIndex, funcDecl.Name), PosMin, PosMax)
-		comment := &ast.Comment{Text: fmt.Sprintf("//line %c.go:%d", nameCharset[mathrand.Intn(len(nameCharset))], linePos)}
 		funcDecl.Doc = prependComment(funcDecl.Doc, comment)
+		funcCounter++
 		return true
 	}
 

main.go

@@ -292,7 +292,7 @@ func mainErr(args []string) error {
 			modpath, err := exec.Command("go", "list", "-m").Output()
 			if err == nil {
 				path := string(bytes.TrimSpace(modpath))
-				envGoPrivate = path+","+path+"_test"
+				envGoPrivate = path + "," + path + "_test"
 			}
 		}
 		// Explicitly set GOPRIVATE, since future garble processes won't
@@ -526,7 +526,7 @@ func transformCompile(args []string) ([]string, error) {
 			// messy.
 			name = "_cgo_" + name
 		default:
-			extraComments, file = transformLineInfo(i, file)
+			extraComments, file = transformLineInfo(origName, file, fset)
 			file = transformGo(file, info, blacklist)
 
 			// Uncomment for some quick debugging. Do not delete.
@@ -683,14 +683,14 @@ func hashWith(salt, value string) string {
 	return "z" + sum[:length]
 }
 
-func hashWithAsUint64(salt, value string, min, max uint64) uint64 {
+func hashWithAsInt64(salt, value string) int64 {
 	d := sha256.New()
 	io.WriteString(d, salt)
 	d.Write(seed)
 	io.WriteString(d, value)
 	sum := d.Sum(nil)
 	val := binary.LittleEndian.Uint64(sum)
-	return min + (val % (max - min))
+	return int64(val)
 }
 
 // buildBlacklist collects all the objects in a package which are known to be