1 // Copyright 2022 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 package subtle
6 7 import "crypto/internal/fips140/alias"
8 9 // XORBytes sets dst[i] = x[i] ^ y[i] for all i < n = min(len(x), len(y)),
10 // returning n, the number of bytes written to dst.
11 //
12 // If dst does not have length at least n,
13 // XORBytes panics without writing anything to dst.
14 //
15 // dst and x or y may overlap exactly or not at all,
16 // otherwise XORBytes may panic.
17 func XORBytes(dst, x, y []byte) int {
18 n := min(len(x), len(y))
19 if n == 0 {
20 return 0
21 }
22 if n > len(dst) {
23 panic("subtle.XORBytes: dst too short")
24 }
25 if alias.InexactOverlap(dst[:n], x[:n]) || alias.InexactOverlap(dst[:n], y[:n]) {
26 panic("subtle.XORBytes: invalid overlap")
27 }
28 xorBytes(&dst[0], &x[0], &y[0], n) // arch-specific
29 return n
30 }
31