Shawn Willden | d67afae | 2014-08-19 12:36:27 -0600 | [diff] [blame] | 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 | |
Shawn Willden | a278f61 | 2014-12-23 11:22:21 -0700 | [diff] [blame] | 17 | #include "asymmetric_key.h" |
| 18 | |
Shawn Willden | 0f906ec | 2015-06-20 09:16:30 -0600 | [diff] [blame] | 19 | #include <new> |
| 20 | |
Shawn Willden | 4d04659 | 2016-01-05 18:24:22 -0700 | [diff] [blame] | 21 | #include <openssl/asn1.h> |
| 22 | #include <openssl/stack.h> |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 23 | #include <openssl/x509.h> |
| 24 | |
Shawn Willden | 4d04659 | 2016-01-05 18:24:22 -0700 | [diff] [blame] | 25 | #include "attestation_record.h" |
Shawn Willden | 567a4a0 | 2014-12-31 12:14:46 -0700 | [diff] [blame] | 26 | #include "openssl_err.h" |
Shawn Willden | d67afae | 2014-08-19 12:36:27 -0600 | [diff] [blame] | 27 | #include "openssl_utils.h" |
Shawn Willden | d67afae | 2014-08-19 12:36:27 -0600 | [diff] [blame] | 28 | |
| 29 | namespace keymaster { |
| 30 | |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 31 | keymaster_error_t AsymmetricKey::formatted_key_material(keymaster_key_format_t format, |
| 32 | UniquePtr<uint8_t[]>* material, |
Shawn Willden | d67afae | 2014-08-19 12:36:27 -0600 | [diff] [blame] | 33 | size_t* size) const { |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 34 | if (format != KM_KEY_FORMAT_X509) |
| 35 | return KM_ERROR_UNSUPPORTED_KEY_FORMAT; |
| 36 | |
Shawn Willden | d67afae | 2014-08-19 12:36:27 -0600 | [diff] [blame] | 37 | if (material == NULL || size == NULL) |
| 38 | return KM_ERROR_OUTPUT_PARAMETER_NULL; |
| 39 | |
Shawn Willden | 4d04659 | 2016-01-05 18:24:22 -0700 | [diff] [blame] | 40 | EVP_PKEY_Ptr pkey(EVP_PKEY_new()); |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 41 | if (!InternalToEvp(pkey.get())) |
Shawn Willden | 567a4a0 | 2014-12-31 12:14:46 -0700 | [diff] [blame] | 42 | return TranslateLastOpenSslError(); |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 43 | |
| 44 | int key_data_length = i2d_PUBKEY(pkey.get(), NULL); |
| 45 | if (key_data_length <= 0) |
Shawn Willden | 567a4a0 | 2014-12-31 12:14:46 -0700 | [diff] [blame] | 46 | return TranslateLastOpenSslError(); |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 47 | |
Shawn Willden | 0f906ec | 2015-06-20 09:16:30 -0600 | [diff] [blame] | 48 | material->reset(new (std::nothrow) uint8_t[key_data_length]); |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 49 | if (material->get() == NULL) |
| 50 | return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| 51 | |
| 52 | uint8_t* tmp = material->get(); |
| 53 | if (i2d_PUBKEY(pkey.get(), &tmp) != key_data_length) { |
| 54 | material->reset(); |
Shawn Willden | 567a4a0 | 2014-12-31 12:14:46 -0700 | [diff] [blame] | 55 | return TranslateLastOpenSslError(); |
Shawn Willden | f268d74 | 2014-08-19 15:36:26 -0600 | [diff] [blame] | 56 | } |
| 57 | |
| 58 | *size = key_data_length; |
| 59 | return KM_ERROR_OK; |
Shawn Willden | d67afae | 2014-08-19 12:36:27 -0600 | [diff] [blame] | 60 | } |
| 61 | |
Shawn Willden | 4d04659 | 2016-01-05 18:24:22 -0700 | [diff] [blame] | 62 | static keymaster_error_t build_attestation_extension(const AuthorizationSet& tee_enforced, |
| 63 | const AuthorizationSet& sw_enforced, |
| 64 | X509_EXTENSION_Ptr* extension) { |
| 65 | ASN1_OBJECT_Ptr oid( |
| 66 | OBJ_txt2obj(kAttestionRecordOid, 1 /* accept numerical dotted string form only */)); |
| 67 | if (!oid.get()) |
| 68 | return TranslateLastOpenSslError(); |
| 69 | |
| 70 | UniquePtr<uint8_t[]> attest_bytes; |
| 71 | size_t attest_bytes_len; |
| 72 | keymaster_error_t error = |
| 73 | build_attestation_record(sw_enforced, tee_enforced, &attest_bytes, &attest_bytes_len); |
| 74 | if (error != KM_ERROR_OK) |
| 75 | return error; |
| 76 | |
| 77 | ASN1_OCTET_STRING_Ptr attest_str(ASN1_OCTET_STRING_new()); |
| 78 | if (!attest_str.get() || |
| 79 | !ASN1_OCTET_STRING_set(attest_str.get(), attest_bytes.get(), attest_bytes_len)) |
| 80 | return TranslateLastOpenSslError(); |
| 81 | |
| 82 | extension->reset( |
| 83 | X509_EXTENSION_create_by_OBJ(nullptr, oid.get(), 0 /* not critical */, attest_str.get())); |
| 84 | if (!extension->get()) |
| 85 | return TranslateLastOpenSslError(); |
| 86 | |
| 87 | return KM_ERROR_OK; |
| 88 | } |
| 89 | |
| 90 | static bool add_public_key(EVP_PKEY* key, X509* certificate, keymaster_error_t* error) { |
| 91 | if (!X509_set_pubkey(certificate, key)) { |
| 92 | *error = TranslateLastOpenSslError(); |
| 93 | return false; |
| 94 | } |
| 95 | return true; |
| 96 | } |
| 97 | |
| 98 | static bool add_attestation_extension(const AuthorizationSet& tee_enforced, |
| 99 | const AuthorizationSet& sw_enforced, X509* certificate, |
| 100 | keymaster_error_t* error) { |
| 101 | X509_EXTENSION_Ptr attest_extension; |
| 102 | *error = build_attestation_extension(tee_enforced, sw_enforced, &attest_extension); |
| 103 | if (*error != KM_ERROR_OK) |
| 104 | return false; |
| 105 | |
| 106 | if (!X509_add_ext(certificate, attest_extension.get() /* Don't release; copied */, |
| 107 | -1 /* insert at end */)) { |
| 108 | *error = TranslateLastOpenSslError(); |
| 109 | return false; |
| 110 | } |
| 111 | |
| 112 | return true; |
| 113 | } |
| 114 | |
| 115 | static keymaster_error_t get_certificate_blob(X509* certificate, keymaster_blob_t* blob) { |
| 116 | int len = i2d_X509(certificate, nullptr); |
| 117 | if (len < 0) |
| 118 | return TranslateLastOpenSslError(); |
| 119 | |
| 120 | uint8_t* data = new uint8_t[len]; |
| 121 | if (!data) |
| 122 | return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| 123 | |
| 124 | uint8_t* p = data; |
| 125 | i2d_X509(certificate, &p); |
| 126 | |
| 127 | blob->data_length = len; |
| 128 | blob->data = data; |
| 129 | |
| 130 | return KM_ERROR_OK; |
| 131 | } |
| 132 | |
| 133 | static bool allocate_cert_chain(size_t entry_count, keymaster_cert_chain_t* chain, |
| 134 | keymaster_error_t* error) { |
| 135 | if (chain->entries) { |
| 136 | for (size_t i = 0; i < chain->entry_count; ++i) |
| 137 | delete[] chain->entries[i].data; |
| 138 | delete[] chain->entries; |
| 139 | } |
| 140 | |
| 141 | chain->entry_count = entry_count; |
| 142 | chain->entries = new keymaster_blob_t[entry_count]; |
| 143 | if (!chain->entries) { |
| 144 | *error = KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| 145 | return false; |
| 146 | } |
| 147 | return true; |
| 148 | } |
| 149 | |
| 150 | // Copies the intermediate and root certificates into chain, leaving the first slot for the leaf |
| 151 | // certificate. |
| 152 | static bool copy_attestation_chain(const KeymasterContext& context, |
| 153 | keymaster_algorithm_t sign_algorithm, |
| 154 | keymaster_cert_chain_t* chain, keymaster_error_t* error) { |
| 155 | |
| 156 | UniquePtr<keymaster_cert_chain_t, CertificateChainDelete> attest_key_chain( |
| 157 | context.AttestationChain(sign_algorithm, error)); |
| 158 | if (!attest_key_chain.get()) |
| 159 | return false; |
| 160 | |
| 161 | if (!allocate_cert_chain(attest_key_chain->entry_count + 1, chain, error)) |
| 162 | return false; |
| 163 | |
| 164 | chain->entries[0] = {}; // Leave empty for the leaf certificate. |
| 165 | for (size_t i = 0; i < attest_key_chain->entry_count; ++i) { |
| 166 | chain->entries[i + 1] = attest_key_chain->entries[i]; |
| 167 | attest_key_chain->entries[i].data = nullptr; |
| 168 | } |
| 169 | |
| 170 | return true; |
| 171 | } |
| 172 | |
| 173 | keymaster_error_t AsymmetricKey::GenerateAttestation(const KeymasterContext& context, |
| 174 | const AuthorizationSet& attest_params, |
| 175 | const AuthorizationSet& tee_enforced, |
| 176 | const AuthorizationSet& sw_enforced, |
| 177 | keymaster_cert_chain_t* cert_chain) const { |
| 178 | |
| 179 | keymaster_algorithm_t sign_algorithm; |
| 180 | if (!attest_params.GetTagValue(TAG_ALGORITHM, &sign_algorithm) || |
| 181 | (sign_algorithm != KM_ALGORITHM_RSA && sign_algorithm != KM_ALGORITHM_EC)) |
| 182 | return KM_ERROR_INCOMPATIBLE_ALGORITHM; |
| 183 | |
| 184 | EVP_PKEY_Ptr pkey(EVP_PKEY_new()); |
| 185 | if (!InternalToEvp(pkey.get())) |
| 186 | return TranslateLastOpenSslError(); |
| 187 | |
| 188 | X509_Ptr certificate(X509_new()); |
| 189 | if (!certificate.get()) |
| 190 | return TranslateLastOpenSslError(); |
| 191 | |
| 192 | if (!X509_set_version(certificate.get(), 2 /* version 3, but zero-based */)) |
| 193 | return TranslateLastOpenSslError(); |
| 194 | |
| 195 | ASN1_INTEGER_Ptr serialNumber(ASN1_INTEGER_new()); |
| 196 | if (!serialNumber.get() || |
| 197 | !ASN1_INTEGER_set( |
| 198 | serialNumber.get(), |
| 199 | 10000 /* TODO(swillden): Figure out what should go in serial number; probably a random |
| 200 | * value */) || |
| 201 | !X509_set_serialNumber(certificate.get(), serialNumber.get() /* Don't release; copied */)) |
| 202 | return TranslateLastOpenSslError(); |
| 203 | |
| 204 | // TODO(swillden): Find useful values (if possible) for issuerName and subjectName. |
| 205 | X509_NAME_Ptr issuerName(X509_NAME_new()); |
| 206 | if (!issuerName.get() || |
| 207 | !X509_set_subject_name(certificate.get(), issuerName.get() /* Don't release; copied */)) |
| 208 | return TranslateLastOpenSslError(); |
| 209 | |
| 210 | X509_NAME_Ptr subjectName(X509_NAME_new()); |
| 211 | if (!subjectName.get() || |
| 212 | !X509_set_subject_name(certificate.get(), subjectName.get() /* Don't release; copied */)) |
| 213 | return TranslateLastOpenSslError(); |
| 214 | |
| 215 | // TODO(swillden): Use key activity and expiration dates for notBefore and notAfter. |
| 216 | ASN1_TIME_Ptr notBefore(ASN1_TIME_new()); |
| 217 | if (!notBefore.get() || !ASN1_TIME_set(notBefore.get(), 0) || |
| 218 | !X509_set_notBefore(certificate.get(), notBefore.get() /* Don't release; copied */)) |
| 219 | return TranslateLastOpenSslError(); |
| 220 | |
| 221 | ASN1_TIME_Ptr notAfter(ASN1_TIME_new()); |
| 222 | if (!notAfter.get() || !ASN1_TIME_set(notAfter.get(), 10000) || |
| 223 | !X509_set_notAfter(certificate.get(), notAfter.get() /* Don't release; copied */)) |
| 224 | return TranslateLastOpenSslError(); |
| 225 | |
| 226 | keymaster_error_t error = KM_ERROR_OK; |
Shawn Willden | fc3cafd | 2016-01-11 08:55:50 -0700 | [diff] [blame^] | 227 | EVP_PKEY_Ptr sign_key(context.AttestationKey(sign_algorithm, &error)); |
Shawn Willden | 4d04659 | 2016-01-05 18:24:22 -0700 | [diff] [blame] | 228 | |
| 229 | if (!sign_key.get() || // |
| 230 | !add_public_key(pkey.get(), certificate.get(), &error) || |
| 231 | !add_attestation_extension(tee_enforced, sw_enforced, certificate.get(), &error)) |
| 232 | return error; |
| 233 | |
| 234 | if (!X509_sign(certificate.get(), sign_key.get(), EVP_sha256())) |
| 235 | return TranslateLastOpenSslError(); |
| 236 | |
| 237 | if (!copy_attestation_chain(context, sign_algorithm, cert_chain, &error)) |
| 238 | return error; |
| 239 | |
| 240 | return get_certificate_blob(certificate.get(), &cert_chain->entries[0]); |
| 241 | } |
| 242 | |
Shawn Willden | d67afae | 2014-08-19 12:36:27 -0600 | [diff] [blame] | 243 | } // namespace keymaster |