1// Copyright 2016 The BoringSSL Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package runner
16
17import (
18	"encoding/binary"
19
20	"golang.org/x/crypto/chacha20"
21)
22
23// Use a different key from crypto/rand/deterministic.c.
24var deterministicRandKey = []byte("runner deterministic key 0123456")
25
26type deterministicRand struct {
27	numCalls uint64
28}
29
30func (d *deterministicRand) Read(buf []byte) (int, error) {
31	clear(buf)
32	var nonce [12]byte
33	binary.LittleEndian.PutUint64(nonce[:8], d.numCalls)
34	cipher, err := chacha20.NewUnauthenticatedCipher(deterministicRandKey, nonce[:])
35	if err != nil {
36		return 0, err
37	}
38	cipher.XORKeyStream(buf, buf)
39	d.numCalls++
40	return len(buf), nil
41}
42