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 // +build !appengine 6 7 // Package subtle implements functions that are often useful in cryptographic 8 // code but require careful thought to use correctly. 9 package subtle // import "golang.org/x/crypto/internal/subtle" 10 11 import "unsafe" 12 13 // AnyOverlap reports whether x and y share memory at any (not necessarily 14 // corresponding) index. The memory beyond the slice length is ignored. 15 func AnyOverlap(x, y []byte) bool { 16 return len(x) > 0 && len(y) > 0 && 17 uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) && 18 uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1])) 19 } 20 21 // InexactOverlap reports whether x and y share memory at any non-corresponding 22 // index. The memory beyond the slice length is ignored. Note that x and y can 23 // have different lengths and still not have any inexact overlap. 24 // 25 // InexactOverlap can be used to implement the requirements of the crypto/cipher 26 // AEAD, Block, BlockMode and Stream interfaces. 27 func InexactOverlap(x, y []byte) bool { 28 if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] { 29 return false 30 } 31 return AnyOverlap(x, y) 32 } 33