1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "crypto/symmetric_key.h"
6 
7 #include <stddef.h>
8 #include <stdint.h>
9 
10 #include <algorithm>
11 #include <utility>
12 
13 #include "base/logging.h"
14 #include "base/strings/string_util.h"
15 #include "crypto/openssl_util.h"
16 #include "third_party/boringssl/src/include/openssl/evp.h"
17 #include "third_party/boringssl/src/include/openssl/rand.h"
18 
19 namespace crypto {
20 
21 SymmetricKey::~SymmetricKey() {
22   std::fill(key_.begin(), key_.end(), '\0');  // Zero out the confidential key.
23 }
24 
25 // static
26 std::unique_ptr<SymmetricKey> SymmetricKey::GenerateRandomKey(
27     Algorithm algorithm,
28     size_t key_size_in_bits) {
29   DCHECK_EQ(AES, algorithm);
30 
31   // Whitelist supported key sizes to avoid accidentaly relying on
32   // algorithms available in NSS but not BoringSSL and vice
33   // versa. Note that BoringSSL does not support AES-192.
34   if (key_size_in_bits != 128 && key_size_in_bits != 256)
35     return nullptr;
36 
37   size_t key_size_in_bytes = key_size_in_bits / 8;
38   DCHECK_EQ(key_size_in_bits, key_size_in_bytes * 8);
39 
40   if (key_size_in_bytes == 0)
41     return nullptr;
42 
43   OpenSSLErrStackTracer err_tracer(FROM_HERE);
44   std::unique_ptr<SymmetricKey> key(new SymmetricKey);
45   uint8_t* key_data = reinterpret_cast<uint8_t*>(
46       base::WriteInto(&key->key_, key_size_in_bytes + 1));
47 
48   int rv = RAND_bytes(key_data, static_cast<int>(key_size_in_bytes));
49   return rv == 1 ? std::move(key) : nullptr;
50 }
51 
52 // static
53 std::unique_ptr<SymmetricKey> SymmetricKey::DeriveKeyFromPassword(
54     Algorithm algorithm,
55     const std::string& password,
56     const std::string& salt,
57     size_t iterations,
58     size_t key_size_in_bits) {
59   DCHECK(algorithm == AES || algorithm == HMAC_SHA1);
60 
61   if (algorithm == AES) {
62     // Whitelist supported key sizes to avoid accidentaly relying on
63     // algorithms available in NSS but not BoringSSL and vice
64     // versa. Note that BoringSSL does not support AES-192.
65     if (key_size_in_bits != 128 && key_size_in_bits != 256)
66       return nullptr;
67   }
68 
69   size_t key_size_in_bytes = key_size_in_bits / 8;
70   DCHECK_EQ(key_size_in_bits, key_size_in_bytes * 8);
71 
72   if (key_size_in_bytes == 0)
73     return nullptr;
74 
75   OpenSSLErrStackTracer err_tracer(FROM_HERE);
76   std::unique_ptr<SymmetricKey> key(new SymmetricKey);
77   uint8_t* key_data = reinterpret_cast<uint8_t*>(
78       base::WriteInto(&key->key_, key_size_in_bytes + 1));
79   int rv = PKCS5_PBKDF2_HMAC_SHA1(
80       password.data(), password.length(),
81       reinterpret_cast<const uint8_t*>(salt.data()), salt.length(),
82       static_cast<unsigned>(iterations),
83       key_size_in_bytes, key_data);
84   return rv == 1 ? std::move(key) : nullptr;
85 }
86 
87 // static
88 std::unique_ptr<SymmetricKey> SymmetricKey::Import(Algorithm algorithm,
89                                                    const std::string& raw_key) {
90   if (algorithm == AES) {
91     // Whitelist supported key sizes to avoid accidentaly relying on
92     // algorithms available in NSS but not BoringSSL and vice
93     // versa. Note that BoringSSL does not support AES-192.
94     if (raw_key.size() != 128/8 && raw_key.size() != 256/8)
95       return nullptr;
96   }
97 
98   std::unique_ptr<SymmetricKey> key(new SymmetricKey);
99   key->key_ = raw_key;
100   return key;
101 }
102 
103 bool SymmetricKey::GetRawKey(std::string* raw_key) {
104   *raw_key = key_;
105   return true;
106 }
107 
108 SymmetricKey::SymmetricKey() = default;
109 
110 }  // namespace crypto
111