Source file src/crypto/internal/subtle/aliasing_appengine.go
Documentation: crypto/internal/subtle
1 // Copyright 2018 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 //go:build appengine 6 // +build appengine 7 8 // Package subtle implements functions that are often useful in cryptographic 9 // code but require careful thought to use correctly. 10 // 11 // This is a mirror of golang.org/x/crypto/internal/subtle. 12 package subtle // import "crypto/internal/subtle" 13 14 // This is the Google App Engine standard variant based on reflect 15 // because the unsafe package and cgo are disallowed. 16 17 import "reflect" 18 19 // AnyOverlap reports whether x and y share memory at any (not necessarily 20 // corresponding) index. The memory beyond the slice length is ignored. 21 func AnyOverlap(x, y []byte) bool { 22 return len(x) > 0 && len(y) > 0 && 23 reflect.ValueOf(&x[0]).Pointer() <= reflect.ValueOf(&y[len(y)-1]).Pointer() && 24 reflect.ValueOf(&y[0]).Pointer() <= reflect.ValueOf(&x[len(x)-1]).Pointer() 25 } 26 27 // InexactOverlap reports whether x and y share memory at any non-corresponding 28 // index. The memory beyond the slice length is ignored. Note that x and y can 29 // have different lengths and still not have any inexact overlap. 30 // 31 // InexactOverlap can be used to implement the requirements of the crypto/cipher 32 // AEAD, Block, BlockMode and Stream interfaces. 33 func InexactOverlap(x, y []byte) bool { 34 if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] { 35 return false 36 } 37 return AnyOverlap(x, y) 38 } 39