1 // Copyright 2017 Google Inc.
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 // http://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 //
15 ///////////////////////////////////////////////////////////////////////////////
16
17 #include "tink/subtle/ecies_hkdf_sender_kem_boringssl.h"
18
19 #include <memory>
20 #include <string>
21 #include <utility>
22
23 #include "absl/memory/memory.h"
24 #include "absl/status/status.h"
25 #include "absl/strings/string_view.h"
26 #include "openssl/bn.h"
27 #include "openssl/evp.h"
28 #include "tink/internal/ec_util.h"
29 #include "tink/internal/ssl_unique_ptr.h"
30 #include "tink/subtle/common_enums.h"
31 #include "tink/subtle/hkdf.h"
32 #include "tink/util/secret_data.h"
33
34 namespace crypto {
35 namespace tink {
36 namespace subtle {
37
38 // static
39 util::StatusOr<std::unique_ptr<const EciesHkdfSenderKemBoringSsl>>
New(subtle::EllipticCurveType curve,const std::string & pubx,const std::string & puby)40 EciesHkdfSenderKemBoringSsl::New(subtle::EllipticCurveType curve,
41 const std::string& pubx,
42 const std::string& puby) {
43 switch (curve) {
44 case EllipticCurveType::NIST_P256:
45 case EllipticCurveType::NIST_P384:
46 case EllipticCurveType::NIST_P521:
47 return EciesHkdfNistPCurveSendKemBoringSsl::New(curve, pubx, puby);
48 case EllipticCurveType::CURVE25519:
49 return EciesHkdfX25519SendKemBoringSsl::New(curve, pubx, puby);
50 default:
51 return util::Status(absl::StatusCode::kUnimplemented,
52 "Unsupported elliptic curve");
53 }
54 }
55
EciesHkdfNistPCurveSendKemBoringSsl(subtle::EllipticCurveType curve,const std::string & pubx,const std::string & puby,internal::SslUniquePtr<EC_POINT> peer_pub_key)56 EciesHkdfNistPCurveSendKemBoringSsl::EciesHkdfNistPCurveSendKemBoringSsl(
57 subtle::EllipticCurveType curve, const std::string& pubx,
58 const std::string& puby, internal::SslUniquePtr<EC_POINT> peer_pub_key)
59 : curve_(curve),
60 pubx_(pubx),
61 puby_(puby),
62 peer_pub_key_(std::move(peer_pub_key)) {}
63
64 // static
65 util::StatusOr<std::unique_ptr<const EciesHkdfSenderKemBoringSsl>>
New(subtle::EllipticCurveType curve,const std::string & pubx,const std::string & puby)66 EciesHkdfNistPCurveSendKemBoringSsl::New(subtle::EllipticCurveType curve,
67 const std::string& pubx,
68 const std::string& puby) {
69 auto status =
70 internal::CheckFipsCompatibility<EciesHkdfNistPCurveSendKemBoringSsl>();
71 if (!status.ok()) return status;
72
73 auto status_or_ec_point = internal::GetEcPoint(curve, pubx, puby);
74 if (!status_or_ec_point.ok()) return status_or_ec_point.status();
75 std::unique_ptr<const EciesHkdfSenderKemBoringSsl> sender_kem(
76 new EciesHkdfNistPCurveSendKemBoringSsl(
77 curve, pubx, puby, std::move(status_or_ec_point.value())));
78 return std::move(sender_kem);
79 }
80
81 util::StatusOr<std::unique_ptr<const EciesHkdfSenderKemBoringSsl::KemKey>>
GenerateKey(subtle::HashType hash,absl::string_view hkdf_salt,absl::string_view hkdf_info,uint32_t key_size_in_bytes,subtle::EcPointFormat point_format) const82 EciesHkdfNistPCurveSendKemBoringSsl::GenerateKey(
83 subtle::HashType hash, absl::string_view hkdf_salt,
84 absl::string_view hkdf_info, uint32_t key_size_in_bytes,
85 subtle::EcPointFormat point_format) const {
86 if (peer_pub_key_.get() == nullptr) {
87 return util::Status(absl::StatusCode::kInternal,
88 "peer_pub_key_ wasn't initialized");
89 }
90
91 auto status_or_ec_group = internal::EcGroupFromCurveType(curve_);
92 if (!status_or_ec_group.ok()) {
93 return status_or_ec_group.status();
94 }
95 internal::SslUniquePtr<EC_GROUP> group =
96 std::move(status_or_ec_group.value());
97 internal::SslUniquePtr<EC_KEY> ephemeral_key(EC_KEY_new());
98 if (1 != EC_KEY_set_group(ephemeral_key.get(), group.get())) {
99 return util::Status(absl::StatusCode::kInternal, "EC_KEY_set_group failed");
100 }
101 if (1 != EC_KEY_generate_key(ephemeral_key.get())) {
102 return util::Status(absl::StatusCode::kInternal,
103 "EC_KEY_generate_key failed");
104 }
105 const BIGNUM* ephemeral_priv = EC_KEY_get0_private_key(ephemeral_key.get());
106 const EC_POINT* ephemeral_pub = EC_KEY_get0_public_key(ephemeral_key.get());
107 auto status_or_string_kem =
108 internal::EcPointEncode(curve_, point_format, ephemeral_pub);
109 if (!status_or_string_kem.ok()) {
110 return status_or_string_kem.status();
111 }
112 std::string kem_bytes = status_or_string_kem.value();
113 auto status_or_string_shared_secret = internal::ComputeEcdhSharedSecret(
114 curve_, ephemeral_priv, peer_pub_key_.get());
115 if (!status_or_string_shared_secret.ok()) {
116 return status_or_string_shared_secret.status();
117 }
118 util::SecretData shared_secret = status_or_string_shared_secret.value();
119 auto symmetric_key_or = Hkdf::ComputeEciesHkdfSymmetricKey(
120 hash, kem_bytes, shared_secret, hkdf_salt, hkdf_info, key_size_in_bytes);
121 if (!symmetric_key_or.ok()) {
122 return symmetric_key_or.status();
123 }
124 util::SecretData symmetric_key = symmetric_key_or.value();
125 return absl::make_unique<const KemKey>(std::move(kem_bytes),
126 std::move(symmetric_key));
127 }
128
EciesHkdfX25519SendKemBoringSsl(internal::SslUniquePtr<EVP_PKEY> peer_public_key)129 EciesHkdfX25519SendKemBoringSsl::EciesHkdfX25519SendKemBoringSsl(
130 internal::SslUniquePtr<EVP_PKEY> peer_public_key)
131 : peer_public_key_(std::move(peer_public_key)) {}
132
133 // static
134 util::StatusOr<std::unique_ptr<const EciesHkdfSenderKemBoringSsl>>
New(subtle::EllipticCurveType curve,const std::string & pubx,const std::string & puby)135 EciesHkdfX25519SendKemBoringSsl::New(subtle::EllipticCurveType curve,
136 const std::string& pubx,
137 const std::string& puby) {
138 auto status =
139 internal::CheckFipsCompatibility<EciesHkdfX25519SendKemBoringSsl>();
140 if (!status.ok()) return status;
141
142 if (curve != CURVE25519) {
143 return util::Status(absl::StatusCode::kInvalidArgument,
144 "curve is not CURVE25519");
145 }
146 if (pubx.size() != internal::X25519KeyPubKeySize()) {
147 return util::Status(absl::StatusCode::kInvalidArgument,
148 "pubx has unexpected length");
149 }
150 if (!puby.empty()) {
151 return util::Status(absl::StatusCode::kInvalidArgument,
152 "puby is not empty");
153 }
154
155 internal::SslUniquePtr<EVP_PKEY> peer_public_key(EVP_PKEY_new_raw_public_key(
156 /*type=*/EVP_PKEY_X25519, /*unused=*/nullptr,
157 /*in=*/reinterpret_cast<const uint8_t*>(pubx.data()),
158 /*len=*/internal::Ed25519KeyPubKeySize()));
159 if (peer_public_key == nullptr) {
160 return util::Status(absl::StatusCode::kInternal,
161 "EVP_PKEY_new_raw_public_key failed");
162 }
163 std::unique_ptr<const EciesHkdfSenderKemBoringSsl> sender_kem(
164 new EciesHkdfX25519SendKemBoringSsl(std::move(peer_public_key)));
165 return std::move(sender_kem);
166 }
167
168 util::StatusOr<std::unique_ptr<const EciesHkdfSenderKemBoringSsl::KemKey>>
GenerateKey(subtle::HashType hash,absl::string_view hkdf_salt,absl::string_view hkdf_info,uint32_t key_size_in_bytes,subtle::EcPointFormat point_format) const169 EciesHkdfX25519SendKemBoringSsl::GenerateKey(
170 subtle::HashType hash, absl::string_view hkdf_salt,
171 absl::string_view hkdf_info, uint32_t key_size_in_bytes,
172 subtle::EcPointFormat point_format) const {
173 if (point_format != EcPointFormat::COMPRESSED) {
174 return util::Status(
175 absl::StatusCode::kInvalidArgument,
176 "X25519 only supports compressed elliptic curve points");
177 }
178
179 // Generate an ephemeral key pair; the public key is the KEM key to use.
180 util::StatusOr<std::unique_ptr<internal::X25519Key>> ephemeral_key =
181 internal::NewX25519Key();
182
183 internal::SslUniquePtr<EVP_PKEY> ssl_priv_key(EVP_PKEY_new_raw_private_key(
184 /*type=*/EVP_PKEY_X25519, /*unused=*/nullptr,
185 /*in=*/(*ephemeral_key)->private_key,
186 /*len=*/internal::Ed25519KeyPrivKeySize()));
187 if (ssl_priv_key == nullptr) {
188 return util::Status(absl::StatusCode::kInternal,
189 "EVP_PKEY_new_raw_private_key failed");
190 }
191
192 util::StatusOr<util::SecretData> shared_secret =
193 internal::ComputeX25519SharedSecret(ssl_priv_key.get(),
194 peer_public_key_.get());
195
196 auto public_key = absl::string_view(
197 reinterpret_cast<const char*>((*ephemeral_key)->public_value),
198 internal::X25519KeyPubKeySize());
199
200 util::StatusOr<util::SecretData> symmetric_key_or =
201 Hkdf::ComputeEciesHkdfSymmetricKey(hash, public_key, *shared_secret,
202 hkdf_salt, hkdf_info,
203 key_size_in_bytes);
204 if (!symmetric_key_or.ok()) {
205 return symmetric_key_or.status();
206 }
207 util::SecretData symmetric_key = *symmetric_key_or;
208 return absl::make_unique<const KemKey>(std::string(public_key),
209 symmetric_key);
210 }
211
212 } // namespace subtle
213 } // namespace tink
214 } // namespace crypto
215