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71 lines
1.6 KiB
Go
71 lines
1.6 KiB
Go
// Copyright (c) 2020, The Garble Authors.
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// See LICENSE for licensing information.
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package literals
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import (
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"go/ast"
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"go/token"
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mathrand "math/rand"
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ah "mvdan.cc/garble/internal/asthelper"
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)
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type shuffle struct{}
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// check that the obfuscator interface is implemented
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var _ obfuscator = shuffle{}
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func (shuffle) obfuscate(data []byte) *ast.BlockStmt {
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key := make([]byte, len(data))
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genRandBytes(key)
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fullData := make([]byte, len(data)+len(key))
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operators := make([]token.Token, len(fullData))
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for i := range operators {
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operators[i] = randOperator()
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}
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for i, b := range key {
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fullData[i], fullData[i+len(data)] = evalOperator(operators[i], data[i], b), b
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}
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shuffledIdxs := mathrand.Perm(len(fullData))
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shuffledFullData := make([]byte, len(fullData))
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for i, b := range fullData {
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shuffledFullData[shuffledIdxs[i]] = b
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}
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args := []ast.Expr{ah.Ident("data")}
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for i := range data {
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args = append(args, operatorToReversedBinaryExpr(
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operators[i],
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ah.IndexExpr("fullData", ah.IntLit(shuffledIdxs[i])),
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ah.IndexExpr("fullData", ah.IntLit(shuffledIdxs[len(data)+i])),
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))
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}
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return ah.BlockStmt(
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&ast.AssignStmt{
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Lhs: []ast.Expr{ah.Ident("fullData")},
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Tok: token.DEFINE,
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Rhs: []ast.Expr{ah.DataToByteSlice(shuffledFullData)},
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},
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&ast.DeclStmt{
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Decl: &ast.GenDecl{
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Tok: token.VAR,
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Specs: []ast.Spec{&ast.ValueSpec{
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Names: []*ast.Ident{ah.Ident("data")},
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Type: &ast.ArrayType{Elt: ah.Ident("byte")},
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}},
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},
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},
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&ast.AssignStmt{
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Lhs: []ast.Expr{ah.Ident("data")},
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Tok: token.ASSIGN,
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Rhs: []ast.Expr{ah.CallExpr(ah.Ident("append"), args...)},
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},
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)
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}
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