1 // Copyright 2023 The Chromium Authors
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/unexportable_key.h"
6
7 #include "base/check.h"
8 #include "crypto/sha2.h"
9 #include "crypto/signature_verifier.h"
10 #include "third_party/boringssl/src/include/openssl/bytestring.h"
11 #include "third_party/boringssl/src/include/openssl/ec.h"
12 #include "third_party/boringssl/src/include/openssl/ec_key.h"
13 #include "third_party/boringssl/src/include/openssl/ecdsa.h"
14 #include "third_party/boringssl/src/include/openssl/evp.h"
15 #include "third_party/boringssl/src/include/openssl/obj.h"
16
17 namespace crypto {
18
19 namespace {
20
CBBToVector(const CBB * cbb)21 std::vector<uint8_t> CBBToVector(const CBB* cbb) {
22 return std::vector<uint8_t>(CBB_data(cbb), CBB_data(cbb) + CBB_len(cbb));
23 }
24
25 class SoftwareECDSA : public UnexportableSigningKey {
26 public:
SoftwareECDSA(bssl::UniquePtr<EC_KEY> key)27 explicit SoftwareECDSA(bssl::UniquePtr<EC_KEY> key) : key_(std::move(key)) {}
28 ~SoftwareECDSA() override = default;
29
Algorithm() const30 SignatureVerifier::SignatureAlgorithm Algorithm() const override {
31 return SignatureVerifier::SignatureAlgorithm::ECDSA_SHA256;
32 }
33
GetSubjectPublicKeyInfo() const34 std::vector<uint8_t> GetSubjectPublicKeyInfo() const override {
35 bssl::UniquePtr<EVP_PKEY> pkey(EVP_PKEY_new());
36 CHECK(EVP_PKEY_set1_EC_KEY(pkey.get(), key_.get()));
37
38 bssl::ScopedCBB cbb;
39 CHECK(CBB_init(cbb.get(), /*initial_capacity=*/128) &&
40 EVP_marshal_public_key(cbb.get(), pkey.get()));
41 return CBBToVector(cbb.get());
42 }
43
GetWrappedKey() const44 std::vector<uint8_t> GetWrappedKey() const override {
45 bssl::ScopedCBB cbb;
46 CHECK(
47 CBB_init(cbb.get(), /*initial_capacity=*/128) &&
48 EC_KEY_marshal_private_key(cbb.get(), key_.get(),
49 EC_PKEY_NO_PARAMETERS | EC_PKEY_NO_PUBKEY));
50 return CBBToVector(cbb.get());
51 }
52
SignSlowly(base::span<const uint8_t> data)53 std::optional<std::vector<uint8_t>> SignSlowly(
54 base::span<const uint8_t> data) override {
55 std::vector<uint8_t> ret(ECDSA_size(key_.get()));
56 std::array<uint8_t, kSHA256Length> digest = SHA256Hash(data);
57 unsigned int ret_size;
58 CHECK(ECDSA_sign(0, digest.data(), digest.size(), ret.data(), &ret_size,
59 key_.get()));
60 ret.resize(ret_size);
61 return ret;
62 }
63
64 private:
65 bssl::UniquePtr<EC_KEY> key_;
66 };
67
68 class SoftwareProvider : public UnexportableKeyProvider {
69 public:
70 ~SoftwareProvider() override = default;
71
SelectAlgorithm(base::span<const SignatureVerifier::SignatureAlgorithm> acceptable_algorithms)72 std::optional<SignatureVerifier::SignatureAlgorithm> SelectAlgorithm(
73 base::span<const SignatureVerifier::SignatureAlgorithm>
74 acceptable_algorithms) override {
75 for (auto algo : acceptable_algorithms) {
76 if (algo == SignatureVerifier::SignatureAlgorithm::ECDSA_SHA256) {
77 return algo;
78 }
79 }
80
81 return std::nullopt;
82 }
83
GenerateSigningKeySlowly(base::span<const SignatureVerifier::SignatureAlgorithm> acceptable_algorithms)84 std::unique_ptr<UnexportableSigningKey> GenerateSigningKeySlowly(
85 base::span<const SignatureVerifier::SignatureAlgorithm>
86 acceptable_algorithms) override {
87 if (!SelectAlgorithm(acceptable_algorithms)) {
88 return nullptr;
89 }
90
91 bssl::UniquePtr<EC_KEY> key(EC_KEY_new_by_curve_name(NID_X9_62_prime256v1));
92 CHECK(EC_KEY_generate_key(key.get()));
93
94 return std::make_unique<SoftwareECDSA>(std::move(key));
95 }
96
FromWrappedSigningKeySlowly(base::span<const uint8_t> wrapped_key)97 std::unique_ptr<UnexportableSigningKey> FromWrappedSigningKeySlowly(
98 base::span<const uint8_t> wrapped_key) override {
99 bssl::UniquePtr<EC_GROUP> p256(
100 EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1));
101 CBS cbs;
102 CBS_init(&cbs, wrapped_key.data(), wrapped_key.size());
103 bssl::UniquePtr<EC_KEY> key(EC_KEY_parse_private_key(&cbs, p256.get()));
104 if (!key || CBS_len(&cbs) != 0) {
105 return nullptr;
106 }
107 return std::make_unique<SoftwareECDSA>(std::move(key));
108 }
109 };
110
111 } // namespace
112
113 std::unique_ptr<UnexportableKeyProvider>
GetSoftwareUnsecureUnexportableKeyProvider()114 GetSoftwareUnsecureUnexportableKeyProvider() {
115 return std::make_unique<SoftwareProvider>();
116 }
117
118 } // namespace crypto
119