Source file src/crypto/internal/subtle/aliasing.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 import "unsafe" 15 16 // AnyOverlap reports whether x and y share memory at any (not necessarily 17 // corresponding) index. The memory beyond the slice length is ignored. 18 func AnyOverlap(x, y []byte) bool { 19 return len(x) > 0 && len(y) > 0 && 20 uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) && 21 uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1])) 22 } 23 24 // InexactOverlap reports whether x and y share memory at any non-corresponding 25 // index. The memory beyond the slice length is ignored. Note that x and y can 26 // have different lengths and still not have any inexact overlap. 27 // 28 // InexactOverlap can be used to implement the requirements of the crypto/cipher 29 // AEAD, Block, BlockMode and Stream interfaces. 30 func InexactOverlap(x, y []byte) bool { 31 if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] { 32 return false 33 } 34 return AnyOverlap(x, y) 35 } 36