| /* |
| * Copyright 2014 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "asymmetric_key.h" |
| |
| #include <keymaster/new> |
| |
| #include <openssl/asn1.h> |
| #include <openssl/stack.h> |
| #include <openssl/x509.h> |
| #include <openssl/x509v3.h> |
| |
| #include "attestation_record.h" |
| #include "openssl_err.h" |
| #include "openssl_utils.h" |
| |
| namespace keymaster { |
| |
| namespace { |
| |
| constexpr int kDigitalSignatureKeyUsageBit = 0; |
| constexpr int kKeyEnciphermentKeyUsageBit = 2; |
| constexpr int kDataEnciphermentKeyUsageBit = 3; |
| constexpr int kMaxKeyUsageBit = 8; |
| |
| template <typename T> T min(T a, T b) { |
| return (a < b) ? a : b; |
| } |
| |
| static keymaster_error_t add_key_usage_extension(const AuthorizationSet& tee_enforced, |
| const AuthorizationSet& sw_enforced, |
| X509* certificate) { |
| // Build BIT_STRING with correct contents. |
| ASN1_BIT_STRING_Ptr key_usage(ASN1_BIT_STRING_new()); |
| |
| for (size_t i = 0; i <= kMaxKeyUsageBit; ++i) { |
| if (!ASN1_BIT_STRING_set_bit(key_usage.get(), i, 0)) { |
| return TranslateLastOpenSslError(); |
| } |
| } |
| |
| if (tee_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_SIGN) || |
| tee_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_VERIFY) || |
| sw_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_SIGN) || |
| sw_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_VERIFY)) { |
| if (!ASN1_BIT_STRING_set_bit(key_usage.get(), kDigitalSignatureKeyUsageBit, 1)) { |
| return TranslateLastOpenSslError(); |
| } |
| } |
| |
| if (tee_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_ENCRYPT) || |
| tee_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_DECRYPT) || |
| sw_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_ENCRYPT) || |
| sw_enforced.Contains(TAG_PURPOSE, KM_PURPOSE_DECRYPT)) { |
| if (!ASN1_BIT_STRING_set_bit(key_usage.get(), kKeyEnciphermentKeyUsageBit, 1) || |
| !ASN1_BIT_STRING_set_bit(key_usage.get(), kDataEnciphermentKeyUsageBit, 1)) { |
| return TranslateLastOpenSslError(); |
| } |
| } |
| |
| // Convert to octets |
| int len = i2d_ASN1_BIT_STRING(key_usage.get(), nullptr); |
| if (len < 0) { |
| return TranslateLastOpenSslError(); |
| } |
| UniquePtr<uint8_t[]> asn1_key_usage(new(std::nothrow) uint8_t[len]); |
| if (!asn1_key_usage.get()) { |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| } |
| uint8_t* p = asn1_key_usage.get(); |
| len = i2d_ASN1_BIT_STRING(key_usage.get(), &p); |
| if (len < 0) { |
| return TranslateLastOpenSslError(); |
| } |
| |
| // Build OCTET_STRING |
| ASN1_OCTET_STRING_Ptr key_usage_str(ASN1_OCTET_STRING_new()); |
| if (!key_usage_str.get() || |
| !ASN1_OCTET_STRING_set(key_usage_str.get(), asn1_key_usage.get(), len)) { |
| return TranslateLastOpenSslError(); |
| } |
| |
| X509_EXTENSION_Ptr key_usage_extension(X509_EXTENSION_create_by_NID(nullptr, // |
| NID_key_usage, // |
| false /* critical */, |
| key_usage_str.get())); |
| if (!key_usage_extension.get()) { |
| return TranslateLastOpenSslError(); |
| } |
| |
| if (!X509_add_ext(certificate, key_usage_extension.get() /* Don't release; copied */, |
| -1 /* insert at end */)) { |
| return TranslateLastOpenSslError(); |
| } |
| |
| return KM_ERROR_OK; |
| } |
| |
| } // anonymous namespace |
| |
| keymaster_error_t AsymmetricKey::formatted_key_material(keymaster_key_format_t format, |
| UniquePtr<uint8_t[]>* material, |
| size_t* size) const { |
| if (format != KM_KEY_FORMAT_X509) |
| return KM_ERROR_UNSUPPORTED_KEY_FORMAT; |
| |
| if (material == NULL || size == NULL) |
| return KM_ERROR_OUTPUT_PARAMETER_NULL; |
| |
| EVP_PKEY_Ptr pkey(EVP_PKEY_new()); |
| if (!InternalToEvp(pkey.get())) |
| return TranslateLastOpenSslError(); |
| |
| int key_data_length = i2d_PUBKEY(pkey.get(), NULL); |
| if (key_data_length <= 0) |
| return TranslateLastOpenSslError(); |
| |
| material->reset(new(std::nothrow) uint8_t[key_data_length]); |
| if (material->get() == NULL) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| uint8_t* tmp = material->get(); |
| if (i2d_PUBKEY(pkey.get(), &tmp) != key_data_length) { |
| material->reset(); |
| return TranslateLastOpenSslError(); |
| } |
| |
| *size = key_data_length; |
| return KM_ERROR_OK; |
| } |
| |
| static keymaster_error_t build_attestation_extension(const AuthorizationSet& attest_params, |
| const AuthorizationSet& tee_enforced, |
| const AuthorizationSet& sw_enforced, |
| const KeymasterContext& context, |
| X509_EXTENSION_Ptr* extension) { |
| ASN1_OBJECT_Ptr oid( |
| OBJ_txt2obj(kAttestionRecordOid, 1 /* accept numerical dotted string form only */)); |
| if (!oid.get()) |
| return TranslateLastOpenSslError(); |
| |
| UniquePtr<uint8_t[]> attest_bytes; |
| size_t attest_bytes_len; |
| keymaster_error_t error = build_attestation_record(attest_params, sw_enforced, tee_enforced, |
| context, &attest_bytes, &attest_bytes_len); |
| if (error != KM_ERROR_OK) |
| return error; |
| |
| ASN1_OCTET_STRING_Ptr attest_str(ASN1_OCTET_STRING_new()); |
| if (!attest_str.get() || |
| !ASN1_OCTET_STRING_set(attest_str.get(), attest_bytes.get(), attest_bytes_len)) |
| return TranslateLastOpenSslError(); |
| |
| extension->reset( |
| X509_EXTENSION_create_by_OBJ(nullptr, oid.get(), 0 /* not critical */, attest_str.get())); |
| if (!extension->get()) |
| return TranslateLastOpenSslError(); |
| |
| return KM_ERROR_OK; |
| } |
| |
| static bool add_public_key(EVP_PKEY* key, X509* certificate, keymaster_error_t* error) { |
| if (!X509_set_pubkey(certificate, key)) { |
| *error = TranslateLastOpenSslError(); |
| return false; |
| } |
| return true; |
| } |
| |
| static bool add_attestation_extension(const AuthorizationSet& attest_params, |
| const AuthorizationSet& tee_enforced, |
| const AuthorizationSet& sw_enforced, |
| const KeymasterContext& context, X509* certificate, |
| keymaster_error_t* error) { |
| X509_EXTENSION_Ptr attest_extension; |
| *error = build_attestation_extension(attest_params, tee_enforced, sw_enforced, context, |
| &attest_extension); |
| if (*error != KM_ERROR_OK) |
| return false; |
| |
| if (!X509_add_ext(certificate, attest_extension.get() /* Don't release; copied */, |
| -1 /* insert at end */)) { |
| *error = TranslateLastOpenSslError(); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| static keymaster_error_t get_certificate_blob(X509* certificate, keymaster_blob_t* blob) { |
| int len = i2d_X509(certificate, nullptr); |
| if (len < 0) |
| return TranslateLastOpenSslError(); |
| |
| uint8_t* data = new(std::nothrow) uint8_t[len]; |
| if (!data) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| uint8_t* p = data; |
| i2d_X509(certificate, &p); |
| |
| blob->data_length = len; |
| blob->data = data; |
| |
| return KM_ERROR_OK; |
| } |
| |
| static bool allocate_cert_chain(size_t entry_count, keymaster_cert_chain_t* chain, |
| keymaster_error_t* error) { |
| if (chain->entries) { |
| for (size_t i = 0; i < chain->entry_count; ++i) |
| delete[] chain->entries[i].data; |
| delete[] chain->entries; |
| } |
| |
| chain->entry_count = entry_count; |
| chain->entries = new(std::nothrow) keymaster_blob_t[entry_count]; |
| if (!chain->entries) { |
| *error = KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| return false; |
| } |
| return true; |
| } |
| |
| // Copies the intermediate and root certificates into chain, leaving the first slot for the leaf |
| // certificate. |
| static bool copy_attestation_chain(const KeymasterContext& context, |
| keymaster_algorithm_t sign_algorithm, |
| keymaster_cert_chain_t* chain, keymaster_error_t* error) { |
| |
| UniquePtr<keymaster_cert_chain_t, CertificateChainDelete> attest_key_chain( |
| context.AttestationChain(sign_algorithm, error)); |
| if (!attest_key_chain.get()) |
| return false; |
| |
| if (!allocate_cert_chain(attest_key_chain->entry_count + 1, chain, error)) |
| return false; |
| |
| chain->entries[0].data = nullptr; // Leave empty for the leaf certificate. |
| chain->entries[1].data_length = 0; |
| |
| for (size_t i = 0; i < attest_key_chain->entry_count; ++i) { |
| chain->entries[i + 1] = attest_key_chain->entries[i]; |
| attest_key_chain->entries[i].data = nullptr; |
| } |
| |
| return true; |
| } |
| |
| keymaster_error_t AsymmetricKey::GenerateAttestation(const KeymasterContext& context, |
| const AuthorizationSet& attest_params, |
| const AuthorizationSet& tee_enforced, |
| const AuthorizationSet& sw_enforced, |
| keymaster_cert_chain_t* cert_chain) const { |
| |
| keymaster_algorithm_t sign_algorithm; |
| if ((!sw_enforced.GetTagValue(TAG_ALGORITHM, &sign_algorithm) && |
| !tee_enforced.GetTagValue(TAG_ALGORITHM, &sign_algorithm))) |
| return KM_ERROR_UNKNOWN_ERROR; |
| |
| if ((sign_algorithm != KM_ALGORITHM_RSA && sign_algorithm != KM_ALGORITHM_EC)) |
| return KM_ERROR_INCOMPATIBLE_ALGORITHM; |
| |
| EVP_PKEY_Ptr pkey(EVP_PKEY_new()); |
| if (!InternalToEvp(pkey.get())) |
| return TranslateLastOpenSslError(); |
| |
| X509_Ptr certificate(X509_new()); |
| if (!certificate.get()) |
| return TranslateLastOpenSslError(); |
| |
| if (!X509_set_version(certificate.get(), 2 /* version 3, but zero-based */)) |
| return TranslateLastOpenSslError(); |
| |
| ASN1_INTEGER_Ptr serialNumber(ASN1_INTEGER_new()); |
| if (!serialNumber.get() || !ASN1_INTEGER_set(serialNumber.get(), 1) || |
| !X509_set_serialNumber(certificate.get(), serialNumber.get() /* Don't release; copied */)) |
| return TranslateLastOpenSslError(); |
| |
| X509_NAME_Ptr subjectName(X509_NAME_new()); |
| if (!subjectName.get() || |
| !X509_NAME_add_entry_by_txt(subjectName.get(), "CN", MBSTRING_ASC, |
| reinterpret_cast<const uint8_t*>("Android Keystore Key"), |
| -1 /* len */, -1 /* loc */, 0 /* set */) || |
| !X509_set_subject_name(certificate.get(), subjectName.get() /* Don't release; copied */)) |
| return TranslateLastOpenSslError(); |
| |
| ASN1_TIME_Ptr notBefore(ASN1_TIME_new()); |
| uint64_t activeDateTime = 0; |
| authorizations().GetTagValue(TAG_ACTIVE_DATETIME, &activeDateTime); |
| if (!notBefore.get() || !ASN1_TIME_set(notBefore.get(), activeDateTime / 1000) || |
| !X509_set_notBefore(certificate.get(), notBefore.get() /* Don't release; copied */)) |
| return TranslateLastOpenSslError(); |
| |
| ASN1_TIME_Ptr notAfter(ASN1_TIME_new()); |
| uint64_t usageExpireDateTime = UINT64_MAX; |
| authorizations().GetTagValue(TAG_USAGE_EXPIRE_DATETIME, &usageExpireDateTime); |
| // TODO(swillden): When trusty can use the C++ standard library change the calculation of |
| // notAfterTime to use std::numeric_limits<time_t>::max(), rather than assuming that time_t is |
| // 32 bits. |
| time_t notAfterTime = min(static_cast<uint64_t>(UINT32_MAX), usageExpireDateTime / 1000); |
| if (!notAfter.get() || !ASN1_TIME_set(notAfter.get(), notAfterTime) || |
| !X509_set_notAfter(certificate.get(), notAfter.get() /* Don't release; copied */)) |
| return TranslateLastOpenSslError(); |
| |
| keymaster_error_t error = add_key_usage_extension(tee_enforced, sw_enforced, certificate.get()); |
| if (error != KM_ERROR_OK) { |
| return error; |
| } |
| |
| EVP_PKEY_Ptr sign_key(context.AttestationKey(sign_algorithm, &error)); |
| |
| if (!sign_key.get() || // |
| !add_public_key(pkey.get(), certificate.get(), &error) || |
| !add_attestation_extension(attest_params, tee_enforced, sw_enforced, context, |
| certificate.get(), &error)) |
| return error; |
| |
| if (!copy_attestation_chain(context, sign_algorithm, cert_chain, &error)) |
| return error; |
| |
| // Copy subject key identifier from cert_chain->entries[1] as authority key_id. |
| if (cert_chain->entry_count < 2) { |
| // cert_chain must have at least two entries, one for the cert we're trying to create and |
| // one for the cert for the key that signs the new cert. |
| return KM_ERROR_UNKNOWN_ERROR; |
| } |
| |
| const uint8_t* p = cert_chain->entries[1].data; |
| X509_Ptr signing_cert(d2i_X509(nullptr, &p, cert_chain->entries[1].data_length)); |
| if (!signing_cert.get()) { |
| return TranslateLastOpenSslError(); |
| } |
| |
| // Set issuer to subject of batch certificate. |
| X509_NAME* issuerSubject = X509_get_subject_name(signing_cert.get()); |
| if (!issuerSubject) { |
| return KM_ERROR_UNKNOWN_ERROR; |
| } |
| if (!X509_set_issuer_name(certificate.get(), issuerSubject)) { |
| return TranslateLastOpenSslError(); |
| } |
| |
| UniquePtr<X509V3_CTX> x509v3_ctx(new(std::nothrow) X509V3_CTX); |
| if (!x509v3_ctx.get()) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| *x509v3_ctx = {}; |
| X509V3_set_ctx(x509v3_ctx.get(), signing_cert.get(), certificate.get(), nullptr /* req */, |
| nullptr /* crl */, 0 /* flags */); |
| |
| X509_EXTENSION_Ptr auth_key_id(X509V3_EXT_nconf_nid(nullptr /* conf */, x509v3_ctx.get(), |
| NID_authority_key_identifier, |
| const_cast<char*>("keyid:always"))); |
| if (!auth_key_id.get() || |
| !X509_add_ext(certificate.get(), auth_key_id.get() /* Don't release; copied */, |
| -1 /* insert at end */)) { |
| return TranslateLastOpenSslError(); |
| } |
| |
| if (!X509_sign(certificate.get(), sign_key.get(), EVP_sha256())) |
| return TranslateLastOpenSslError(); |
| |
| return get_certificate_blob(certificate.get(), &cert_chain->entries[0]); |
| } |
| |
| } // namespace keymaster |
