1 /*
2 * Copyright 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "hmac_operation.h"
18
19 #include <openssl/evp.h>
20 #include <openssl/hmac.h>
21
22 #include <keymaster/km_openssl/hmac_key.h>
23 #include <keymaster/km_openssl/openssl_err.h>
24 #include <keymaster/km_openssl/openssl_utils.h>
25
26 #if defined(OPENSSL_IS_BORINGSSL)
27 #include <openssl/mem.h>
28 typedef size_t openssl_size_t;
29 #else
30 typedef int openssl_size_t;
31 #endif
32
33 namespace keymaster {
34
CreateOperation(Key && key,const AuthorizationSet & begin_params,keymaster_error_t * error)35 OperationPtr HmacOperationFactory::CreateOperation(Key&& key, const AuthorizationSet& begin_params,
36 keymaster_error_t* error) {
37 uint32_t min_mac_length_bits;
38 if (!key.authorizations().GetTagValue(TAG_MIN_MAC_LENGTH, &min_mac_length_bits)) {
39 LOG_E("HMAC key must have KM_TAG_MIN_MAC_LENGTH", 0);
40 *error = KM_ERROR_INVALID_KEY_BLOB;
41 return nullptr;
42 }
43
44 uint32_t mac_length_bits = UINT32_MAX;
45 if (begin_params.GetTagValue(TAG_MAC_LENGTH, &mac_length_bits)) {
46 if (purpose() == KM_PURPOSE_VERIFY) {
47 LOG_E("MAC length may not be specified for verify", 0);
48 *error = KM_ERROR_INVALID_ARGUMENT;
49 return nullptr;
50 }
51 if ((mac_length_bits % 8) != 0) {
52 LOG_E("MAC length must be a multiple of 8", mac_length_bits);
53 *error = KM_ERROR_UNSUPPORTED_MAC_LENGTH;
54 return nullptr;
55 }
56 } else {
57 if (purpose() == KM_PURPOSE_SIGN) {
58 *error = KM_ERROR_MISSING_MAC_LENGTH;
59 return nullptr;
60 }
61 }
62
63 keymaster_digest_t digest;
64 if (!key.authorizations().GetTagValue(TAG_DIGEST, &digest)) {
65 LOG_E("%d digests found in HMAC key authorizations; must be exactly 1",
66 begin_params.GetTagCount(TAG_DIGEST));
67 *error = KM_ERROR_INVALID_KEY_BLOB;
68 return nullptr;
69 }
70
71 UniquePtr<HmacOperation> op(new (std::nothrow) HmacOperation(
72 move(key), purpose(), digest, mac_length_bits / 8, min_mac_length_bits / 8));
73 if (!op.get())
74 *error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
75 else
76 *error = op->error();
77
78 if (*error != KM_ERROR_OK) return nullptr;
79
80 return move(op);
81 }
82
83 static keymaster_digest_t supported_digests[] = {KM_DIGEST_SHA1, KM_DIGEST_SHA_2_224,
84 KM_DIGEST_SHA_2_256, KM_DIGEST_SHA_2_384,
85 KM_DIGEST_SHA_2_512};
SupportedDigests(size_t * digest_count) const86 const keymaster_digest_t* HmacOperationFactory::SupportedDigests(size_t* digest_count) const {
87 *digest_count = array_length(supported_digests);
88 return supported_digests;
89 }
90
HmacOperation(Key && key,keymaster_purpose_t purpose,keymaster_digest_t digest,size_t mac_length,size_t min_mac_length)91 HmacOperation::HmacOperation(Key&& key, keymaster_purpose_t purpose, keymaster_digest_t digest,
92 size_t mac_length, size_t min_mac_length)
93 : Operation(purpose, key.hw_enforced_move(), key.sw_enforced_move()), error_(KM_ERROR_OK),
94 mac_length_(mac_length), min_mac_length_(min_mac_length) {
95 // Initialize CTX first, so dtor won't crash even if we error out later.
96 HMAC_CTX_init(&ctx_);
97
98 const EVP_MD* md = nullptr;
99 switch (digest) {
100 case KM_DIGEST_NONE:
101 case KM_DIGEST_MD5:
102 error_ = KM_ERROR_UNSUPPORTED_DIGEST;
103 break;
104 case KM_DIGEST_SHA1:
105 md = EVP_sha1();
106 break;
107 case KM_DIGEST_SHA_2_224:
108 md = EVP_sha224();
109 break;
110 case KM_DIGEST_SHA_2_256:
111 md = EVP_sha256();
112 break;
113 case KM_DIGEST_SHA_2_384:
114 md = EVP_sha384();
115 break;
116 case KM_DIGEST_SHA_2_512:
117 md = EVP_sha512();
118 break;
119 }
120
121 if (md == nullptr) {
122 error_ = KM_ERROR_UNSUPPORTED_DIGEST;
123 return;
124 }
125
126 if (purpose == KM_PURPOSE_SIGN) {
127 if (mac_length > EVP_MD_size(md) || mac_length < kMinHmacLengthBits / 8) {
128 error_ = KM_ERROR_UNSUPPORTED_MAC_LENGTH;
129 return;
130 }
131 if (mac_length < min_mac_length) {
132 error_ = KM_ERROR_INVALID_MAC_LENGTH;
133 return;
134 }
135 }
136
137 KeymasterKeyBlob blob = key.key_material_move();
138 HMAC_Init_ex(&ctx_, blob.key_material, blob.key_material_size, md, nullptr /* engine */);
139 }
140
~HmacOperation()141 HmacOperation::~HmacOperation() {
142 HMAC_CTX_cleanup(&ctx_);
143 }
144
Begin(const AuthorizationSet &,AuthorizationSet *)145 keymaster_error_t HmacOperation::Begin(const AuthorizationSet& /* input_params */,
146 AuthorizationSet* /* output_params */) {
147 auto rc = GenerateRandom(reinterpret_cast<uint8_t*>(&operation_handle_),
148 (size_t)sizeof(operation_handle_));
149 if (rc != KM_ERROR_OK) return rc;
150
151 return error_;
152 }
153
Update(const AuthorizationSet &,const Buffer & input,AuthorizationSet *,Buffer *,size_t * input_consumed)154 keymaster_error_t HmacOperation::Update(const AuthorizationSet& /* additional_params */,
155 const Buffer& input, AuthorizationSet* /* output_params */,
156 Buffer* /* output */, size_t* input_consumed) {
157 if (!HMAC_Update(&ctx_, input.peek_read(), input.available_read()))
158 return TranslateLastOpenSslError();
159 *input_consumed = input.available_read();
160 return KM_ERROR_OK;
161 }
162
Abort()163 keymaster_error_t HmacOperation::Abort() {
164 return KM_ERROR_OK;
165 }
166
Finish(const AuthorizationSet & additional_params,const Buffer & input,const Buffer & signature,AuthorizationSet *,Buffer * output)167 keymaster_error_t HmacOperation::Finish(const AuthorizationSet& additional_params,
168 const Buffer& input, const Buffer& signature,
169 AuthorizationSet* /* output_params */, Buffer* output) {
170 keymaster_error_t error = UpdateForFinish(additional_params, input);
171 if (error != KM_ERROR_OK) return error;
172
173 uint8_t digest[EVP_MAX_MD_SIZE];
174 unsigned int digest_len;
175 if (!HMAC_Final(&ctx_, digest, &digest_len)) return TranslateLastOpenSslError();
176
177 switch (purpose()) {
178 case KM_PURPOSE_SIGN:
179 if (mac_length_ > digest_len) return KM_ERROR_UNSUPPORTED_MAC_LENGTH;
180 if (!output->reserve(mac_length_) || !output->write(digest, mac_length_))
181 return KM_ERROR_MEMORY_ALLOCATION_FAILED;
182 return KM_ERROR_OK;
183 case KM_PURPOSE_VERIFY: {
184 size_t siglen = signature.available_read();
185 if (siglen > digest_len || siglen < kMinHmacLengthBits / 8)
186 return KM_ERROR_UNSUPPORTED_MAC_LENGTH;
187 if (siglen < min_mac_length_) return KM_ERROR_INVALID_MAC_LENGTH;
188 if (CRYPTO_memcmp(signature.peek_read(), digest, siglen) != 0)
189 return KM_ERROR_VERIFICATION_FAILED;
190 return KM_ERROR_OK;
191 }
192 default:
193 return KM_ERROR_UNSUPPORTED_PURPOSE;
194 }
195 }
196
197 } // namespace keymaster
198