garble/internal/literals/xor.go

package literals

import (
	"go/ast"
	"go/token"
)

type xor struct{}

// check that the obfuscator interface is implemented
var _ obfuscator = xor{}

func (x xor) obfuscate(data []byte) *ast.BlockStmt {
	key := make([]byte, len(data))
	genRandBytes(key)

	for i, b := range key {
		data[i] = data[i] ^ b
	}

	return &ast.BlockStmt{List: []ast.Stmt{
		&ast.AssignStmt{
			Lhs: []ast.Expr{&ast.Ident{Name: "key"}},
			Tok: token.DEFINE,
			Rhs: []ast.Expr{dataToByteSlice(key)},
		},
		&ast.AssignStmt{
			Lhs: []ast.Expr{&ast.Ident{Name: "data"}},
			Tok: token.DEFINE,
			Rhs: []ast.Expr{dataToByteSlice(data)},
		},
		&ast.RangeStmt{
			Key:   &ast.Ident{Name: "i"},
			Value: &ast.Ident{Name: "b"},
			Tok:   token.DEFINE,
			X:     &ast.Ident{Name: "key"},
			Body: &ast.BlockStmt{List: []ast.Stmt{
				&ast.AssignStmt{
					Lhs: []ast.Expr{&ast.IndexExpr{
						X:     &ast.Ident{Name: "data"},
						Index: &ast.Ident{Name: "i"},
					}},
					Tok: token.ASSIGN,
					Rhs: []ast.Expr{&ast.BinaryExpr{
						X: &ast.IndexExpr{
							X:     &ast.Ident{Name: "data"},
							Index: &ast.Ident{Name: "i"},
						},
						Op: token.XOR,
						Y:  &ast.Ident{Name: "b"},
					}},
				},
			}},
		},
	}}
}