1 /*
2 * Copyright 2020, 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 <iostream>
18
19 #include <openssl/asn1.h>
20 #include <openssl/evp.h>
21 #include <openssl/x509v3.h>
22
23 #include <hardware/keymaster_defs.h>
24 #include <keymaster/android_keymaster_utils.h>
25 #include <keymaster/authorization_set.h>
26 #include <keymaster/km_openssl/asymmetric_key.h>
27 #include <keymaster/km_openssl/certificate_utils.h>
28 #include <keymaster/km_openssl/openssl_err.h>
29 #include <keymaster/logger.h>
30
31 namespace keymaster {
32
33 namespace {
34
35 constexpr const char kDefaultSubject[] = "Android Keystore Key";
36 constexpr int kDataEnciphermentKeyUsageBit = 3;
37 constexpr int kDigitalSignatureKeyUsageBit = 0;
38 constexpr int kKeyEnciphermentKeyUsageBit = 2;
39 constexpr int kKeyAgreementKeyUsageBit = 4;
40 constexpr int kMaxKeyUsageBit = 8;
41
min(T && a,T && b)42 template <typename T> T&& min(T&& a, T&& b) {
43 return (a < b) ? forward<T>(a) : forward<T>(b);
44 }
45
fake_sign_cert(X509 * cert)46 keymaster_error_t fake_sign_cert(X509* cert) {
47 X509_ALGOR_Ptr algor(X509_ALGOR_new());
48 if (!algor.get()) {
49 return TranslateLastOpenSslError();
50 }
51 X509_ALGOR_set0(algor.get(), OBJ_nid2obj(NID_sha256WithRSAEncryption), V_ASN1_NULL, nullptr);
52
53 // Set signature to a bit string containing a single byte, value 0.
54 uint8_t fake_sig = 0;
55 if (!X509_set1_signature_algo(cert, algor.get()) ||
56 !X509_set1_signature_value(cert, &fake_sig, sizeof(fake_sig))) {
57 return TranslateLastOpenSslError();
58 }
59
60 return KM_ERROR_OK;
61 }
62
63 } // namespace
64
make_name_from_str(const char name[],X509_NAME_Ptr * name_out)65 keymaster_error_t make_name_from_str(const char name[], X509_NAME_Ptr* name_out) {
66 if (name_out == nullptr) return KM_ERROR_UNEXPECTED_NULL_POINTER;
67 X509_NAME_Ptr x509_name(X509_NAME_new());
68 if (!x509_name.get()) {
69 return TranslateLastOpenSslError();
70 }
71 if (!X509_NAME_add_entry_by_txt(x509_name.get(), //
72 "CN", //
73 MBSTRING_ASC, reinterpret_cast<const uint8_t*>(&name[0]),
74 -1, // len
75 -1, // loc
76 0 /* set */)) {
77 return TranslateLastOpenSslError();
78 }
79 *name_out = move(x509_name);
80 return KM_ERROR_OK;
81 }
82
make_name_from_der(const keymaster_blob_t & name,X509_NAME_Ptr * name_out)83 keymaster_error_t make_name_from_der(const keymaster_blob_t& name, X509_NAME_Ptr* name_out) {
84 if (!name_out || !name.data) return KM_ERROR_UNEXPECTED_NULL_POINTER;
85
86 const uint8_t* p = name.data;
87 X509_NAME_Ptr x509_name(d2i_X509_NAME(nullptr, &p, name.data_length));
88 if (!x509_name.get()) {
89 return TranslateLastOpenSslError();
90 }
91
92 *name_out = move(x509_name);
93 return KM_ERROR_OK;
94 }
95
get_common_name(X509_NAME * name,UniquePtr<const char[]> * name_out)96 keymaster_error_t get_common_name(X509_NAME* name, UniquePtr<const char[]>* name_out) {
97 if (name == nullptr || name_out == nullptr) return KM_ERROR_UNEXPECTED_NULL_POINTER;
98 int len = X509_NAME_get_text_by_NID(name, NID_commonName, nullptr, 0);
99 UniquePtr<char[]> name_ptr(new (std::nothrow) char[len]);
100 if (!name_ptr) {
101 return KM_ERROR_MEMORY_ALLOCATION_FAILED;
102 }
103 X509_NAME_get_text_by_NID(name, NID_commonName, name_ptr.get(), len);
104 *name_out = UniquePtr<const char[]>{name_ptr.release()};
105 return KM_ERROR_OK;
106 }
107
get_certificate_params(const AuthorizationSet & caller_params,CertificateCallerParams * cert_params,KmVersion kmVersion)108 keymaster_error_t get_certificate_params(const AuthorizationSet& caller_params,
109 CertificateCallerParams* cert_params,
110 KmVersion kmVersion) {
111 if (!cert_params) return KM_ERROR_UNEXPECTED_NULL_POINTER;
112
113 BIGNUM_Ptr serial(BN_new());
114 if (!serial) {
115 return KM_ERROR_MEMORY_ALLOCATION_FAILED;
116 }
117
118 keymaster_blob_t serial_blob{.data = nullptr, .data_length = 0};
119 if (caller_params.GetTagValue(TAG_CERTIFICATE_SERIAL, &serial_blob)) {
120 if (BN_bin2bn(serial_blob.data, serial_blob.data_length, serial.get()) == nullptr) {
121 return TranslateLastOpenSslError();
122 }
123 } else {
124 // Default serial is one.
125 BN_one(serial.get());
126 }
127 cert_params->serial = move(serial);
128
129 cert_params->active_date_time = 0;
130 cert_params->expire_date_time = kUndefinedExpirationDateTime;
131
132 uint64_t tmp;
133 if (kmVersion < KmVersion::KEYMINT_1) {
134 if (caller_params.GetTagValue(TAG_ACTIVE_DATETIME, &tmp)) {
135 LOG_D("Using TAG_ACTIVE_DATETIME: %lu", tmp);
136 cert_params->active_date_time = static_cast<int64_t>(tmp);
137 }
138 if (caller_params.GetTagValue(TAG_ORIGINATION_EXPIRE_DATETIME, &tmp)) {
139 LOG_D("Using TAG_ORIGINATION_EXPIRE_DATETIME: %lu", tmp);
140 cert_params->expire_date_time = static_cast<int64_t>(tmp);
141 }
142 } else {
143 if (!caller_params.GetTagValue(TAG_CERTIFICATE_NOT_BEFORE, &tmp)) {
144 return KM_ERROR_MISSING_NOT_BEFORE;
145 }
146 LOG_D("Using TAG_CERTIFICATE_NOT_BEFORE: %lu", tmp);
147 cert_params->active_date_time = static_cast<int64_t>(tmp);
148
149 if (!caller_params.GetTagValue(TAG_CERTIFICATE_NOT_AFTER, &tmp)) {
150 return KM_ERROR_MISSING_NOT_AFTER;
151 }
152 LOG_D("Using TAG_CERTIFICATE_NOT_AFTER: %lu", tmp);
153 cert_params->expire_date_time = static_cast<int64_t>(tmp);
154 }
155
156 LOG_D("Got certificate date params: NotBefore = %ld, NotAfter = %ld",
157 cert_params->active_date_time, cert_params->expire_date_time);
158
159 keymaster_blob_t subject{};
160 if (caller_params.GetTagValue(TAG_CERTIFICATE_SUBJECT, &subject) && subject.data_length) {
161 return make_name_from_der(subject, &cert_params->subject_name);
162 }
163
164 return make_name_from_str(kDefaultSubject, &cert_params->subject_name);
165 }
166
make_key_usage_extension(bool is_signing_key,bool is_encryption_key,bool is_key_agreement_key,X509_EXTENSION_Ptr * usage_extension_out)167 keymaster_error_t make_key_usage_extension(bool is_signing_key, bool is_encryption_key,
168 bool is_key_agreement_key,
169 X509_EXTENSION_Ptr* usage_extension_out) {
170 if (usage_extension_out == nullptr) return KM_ERROR_UNEXPECTED_NULL_POINTER;
171
172 // Build BIT_STRING with correct contents.
173 ASN1_BIT_STRING_Ptr key_usage(ASN1_BIT_STRING_new());
174 if (!key_usage) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
175
176 for (size_t i = 0; i <= kMaxKeyUsageBit; ++i) {
177 if (!ASN1_BIT_STRING_set_bit(key_usage.get(), i, 0)) {
178 return TranslateLastOpenSslError();
179 }
180 }
181
182 if (is_signing_key) {
183 if (!ASN1_BIT_STRING_set_bit(key_usage.get(), kDigitalSignatureKeyUsageBit, 1)) {
184 return TranslateLastOpenSslError();
185 }
186 }
187
188 if (is_encryption_key) {
189 if (!ASN1_BIT_STRING_set_bit(key_usage.get(), kKeyEnciphermentKeyUsageBit, 1) ||
190 !ASN1_BIT_STRING_set_bit(key_usage.get(), kDataEnciphermentKeyUsageBit, 1)) {
191 return TranslateLastOpenSslError();
192 }
193 }
194
195 if (is_key_agreement_key) {
196 if (!ASN1_BIT_STRING_set_bit(key_usage.get(), kKeyAgreementKeyUsageBit, 1)) {
197 return TranslateLastOpenSslError();
198 }
199 }
200
201 // Convert to octets
202 int len = i2d_ASN1_BIT_STRING(key_usage.get(), nullptr);
203 if (len < 0) {
204 return TranslateLastOpenSslError();
205 }
206 UniquePtr<uint8_t[]> asn1_key_usage(new (std::nothrow) uint8_t[len]);
207 if (!asn1_key_usage.get()) {
208 return KM_ERROR_MEMORY_ALLOCATION_FAILED;
209 }
210 uint8_t* p = asn1_key_usage.get();
211 len = i2d_ASN1_BIT_STRING(key_usage.get(), &p);
212 if (len < 0) {
213 return TranslateLastOpenSslError();
214 }
215
216 // Build OCTET_STRING
217 ASN1_OCTET_STRING_Ptr key_usage_str(ASN1_OCTET_STRING_new());
218 if (!key_usage_str.get() ||
219 !ASN1_OCTET_STRING_set(key_usage_str.get(), asn1_key_usage.get(), len)) {
220 return TranslateLastOpenSslError();
221 }
222
223 X509_EXTENSION_Ptr key_usage_extension(X509_EXTENSION_create_by_NID(nullptr, //
224 NID_key_usage, //
225 true /* critical */,
226 key_usage_str.get()));
227 if (!key_usage_extension.get()) {
228 return TranslateLastOpenSslError();
229 }
230
231 *usage_extension_out = move(key_usage_extension);
232
233 return KM_ERROR_OK;
234 }
235
236 // Creates a rump certificate structure with serial, subject and issuer names, as well as
237 // activation and expiry date.
238 // Callers should pass an empty X509_Ptr and check the return value for KM_ERROR_OK (0) before
239 // accessing the result.
make_cert_rump(const X509_NAME * issuer,const CertificateCallerParams & cert_params,X509_Ptr * cert_out)240 keymaster_error_t make_cert_rump(const X509_NAME* issuer,
241 const CertificateCallerParams& cert_params, X509_Ptr* cert_out) {
242 if (!cert_out || !issuer) return KM_ERROR_UNEXPECTED_NULL_POINTER;
243
244 // Create certificate structure.
245 X509_Ptr certificate(X509_new());
246 if (!certificate.get()) return TranslateLastOpenSslError();
247
248 // Set the X509 version.
249 if (!X509_set_version(certificate.get(), 2 /* version 3 */)) return TranslateLastOpenSslError();
250
251 // Set the certificate serialNumber
252 ASN1_INTEGER_Ptr serial_number(ASN1_INTEGER_new());
253 if (!serial_number.get() || //
254 !BN_to_ASN1_INTEGER(cert_params.serial.get(), serial_number.get()) ||
255 !X509_set_serialNumber(certificate.get(),
256 serial_number.get() /* Don't release; copied */)) {
257 return TranslateLastOpenSslError();
258 }
259
260 if (!X509_set_subject_name(certificate.get(),
261 const_cast<X509_NAME*>(cert_params.subject_name.get()))) {
262 return TranslateLastOpenSslError();
263 }
264
265 if (!X509_set_issuer_name(certificate.get(), const_cast<X509_NAME*>(issuer))) {
266 return TranslateLastOpenSslError();
267 }
268
269 // Set activation date.
270 ASN1_TIME_Ptr notBefore(ASN1_TIME_new());
271 LOG_D("Setting notBefore to %ld: ", cert_params.active_date_time / 1000);
272 time_t notBeforeTime = static_cast<time_t>(cert_params.active_date_time / 1000);
273 if (!notBefore.get() || !ASN1_TIME_set(notBefore.get(), notBeforeTime) ||
274 !X509_set_notBefore(certificate.get(), notBefore.get() /* Don't release; copied */)) {
275 return TranslateLastOpenSslError();
276 }
277
278 // Set expiration date.
279 ASN1_TIME_Ptr notAfter(ASN1_TIME_new());
280 LOG_D("Setting notAfter to %ld: ", cert_params.expire_date_time / 1000);
281 time_t notAfterTime = static_cast<time_t>(cert_params.expire_date_time / 1000);
282
283 if (!notAfter.get() || !ASN1_TIME_set(notAfter.get(), notAfterTime) ||
284 !X509_set_notAfter(certificate.get(), notAfter.get() /* Don't release; copied */)) {
285 return TranslateLastOpenSslError();
286 }
287
288 *cert_out = move(certificate);
289 return KM_ERROR_OK;
290 }
291
make_cert(const EVP_PKEY * evp_pkey,const X509_NAME * issuer,const CertificateCallerParams & cert_params,X509_Ptr * cert_out)292 keymaster_error_t make_cert(const EVP_PKEY* evp_pkey, const X509_NAME* issuer,
293 const CertificateCallerParams& cert_params, X509_Ptr* cert_out) {
294
295 // Make the rump certificate with serial, subject, not before and not after dates.
296 X509_Ptr certificate;
297 if (keymaster_error_t error = make_cert_rump(issuer, cert_params, &certificate)) {
298 return error;
299 }
300
301 // Set the public key.
302 if (!X509_set_pubkey(certificate.get(), (EVP_PKEY*)evp_pkey)) {
303 return TranslateLastOpenSslError();
304 }
305
306 // Make and add the key usage extension.
307 X509_EXTENSION_Ptr key_usage_extension;
308 if (auto error =
309 make_key_usage_extension(cert_params.is_signing_key, cert_params.is_encryption_key,
310 cert_params.is_agreement_key, &key_usage_extension)) {
311 return error;
312 }
313 if (!X509_add_ext(certificate.get(), key_usage_extension.get() /* Don't release; copied */,
314 -1 /* insert at end */)) {
315 return TranslateLastOpenSslError();
316 }
317
318 *cert_out = move(certificate);
319 return KM_ERROR_OK;
320 }
321
sign_cert(X509 * certificate,const EVP_PKEY * signing_key)322 keymaster_error_t sign_cert(X509* certificate, const EVP_PKEY* signing_key) {
323 if (!certificate || !signing_key) return KM_ERROR_UNEXPECTED_NULL_POINTER;
324
325 // X509_sign takes the key as non-const, but per the BoringSSL dev team, that's a legacy
326 // mistake that hasn't yet been corrected.
327 auto sk = const_cast<EVP_PKEY*>(signing_key);
328
329 // Ed25519 has an internal digest so needs to have no digest fed into X509_sign.
330 const EVP_MD* digest = (EVP_PKEY_id(signing_key) == EVP_PKEY_ED25519) ? nullptr : EVP_sha256();
331
332 if (!X509_sign(certificate, sk, digest)) {
333 return TranslateLastOpenSslError();
334 }
335 return KM_ERROR_OK;
336 }
337
generate_self_signed_cert(const AsymmetricKey & key,const AuthorizationSet & params,bool fake_signature,keymaster_error_t * error)338 CertificateChain generate_self_signed_cert(const AsymmetricKey& key, const AuthorizationSet& params,
339 bool fake_signature, keymaster_error_t* error) {
340 keymaster_error_t err;
341 if (!error) error = &err;
342
343 EVP_PKEY_Ptr pkey(key.InternalToEvp());
344 if (pkey.get() == nullptr) {
345 *error = TranslateLastOpenSslError();
346 return {};
347 }
348
349 CertificateCallerParams cert_params{};
350 // Self signed certificates are only generated since Keymint 1.0. To keep the API stable for
351 // now, we pass KEYMINT_1 to get_certificate_params, which has the intended effect. If
352 // get_certificate_params ever has to distinguish between versions of KeyMint this needs to be
353 // changed.
354 *error = get_certificate_params(params, &cert_params, KmVersion::KEYMINT_1);
355 if (*error != KM_ERROR_OK) return {};
356
357 cert_params.is_signing_key =
358 (key.authorizations().Contains(TAG_PURPOSE, KM_PURPOSE_SIGN) ||
359 key.authorizations().Contains(TAG_PURPOSE, KM_PURPOSE_ATTEST_KEY));
360 cert_params.is_encryption_key = key.authorizations().Contains(TAG_PURPOSE, KM_PURPOSE_DECRYPT);
361 cert_params.is_agreement_key = key.authorizations().Contains(TAG_PURPOSE, KM_PURPOSE_AGREE_KEY);
362
363 X509_Ptr cert;
364 *error = make_cert(pkey.get(), cert_params.subject_name.get() /* issuer */, cert_params, &cert);
365 if (*error != KM_ERROR_OK) return {};
366
367 if (fake_signature) {
368 *error = fake_sign_cert(cert.get());
369 } else {
370 *error = sign_cert(cert.get(), pkey.get());
371 }
372 if (*error != KM_ERROR_OK) return {};
373
374 CertificateChain result(1);
375 if (!result) {
376 *error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
377 return {};
378 }
379
380 *error = encode_certificate(cert.get(), &result.entries[0]);
381 if (*error != KM_ERROR_OK) return {};
382
383 return result;
384 }
385
encode_certificate(X509 * certificate,keymaster_blob_t * blob)386 keymaster_error_t encode_certificate(X509* certificate, keymaster_blob_t* blob) {
387 int len = i2d_X509(certificate, nullptr /* ppout */);
388 if (len < 0) return TranslateLastOpenSslError();
389
390 blob->data = new (std::nothrow) uint8_t[len];
391 if (!blob->data) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
392
393 uint8_t* p = const_cast<uint8_t*>(blob->data);
394 blob->data_length = i2d_X509(certificate, &p);
395 return KM_ERROR_OK;
396 }
397
398 } // namespace keymaster
399