github.com/psiphon-Labs/psiphon-tunnel-core@v2.0.28+incompatible/psiphon/common/crypto/internal/subtle/aliasing.go (about)

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