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/*
* Copyright (C) 2021 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 <android/hardware/keymaster/4.0/IKeymasterDevice.h>
#include <keymasterV4_0/attestation_record.h>
#include <keymasterV4_0/openssl_utils.h>
#include "keymaster4_common.h"
namespace android::hardware::keymaster::V4_0::fuzzer {
constexpr size_t kMinBytes = 1;
constexpr size_t kMaxBytes = 10;
class KeyMaster4AttestationFuzzer {
public:
void process(const uint8_t* data, size_t size);
private:
ErrorCode generateKey(const AuthorizationSet& keyDesc, hidl_vec<uint8_t>* keyBlob,
KeyCharacteristics* keyCharacteristics);
ErrorCode attestKey(hidl_vec<uint8_t>& keyBlob, const AuthorizationSet& attestParams,
hidl_vec<hidl_vec<uint8_t>>* certificateChain);
X509_Ptr parseCertificateBlob(const hidl_vec<uint8_t>& blob);
ASN1_OCTET_STRING* getAttestationRecord(const X509* certificate);
bool verifyAttestationRecord(const hidl_vec<uint8_t>& attestationCert);
void invokeAttestationRecord();
sp<IKeymasterDevice> mKeymaster = nullptr;
std::unique_ptr<FuzzedDataProvider> mFdp = nullptr;
};
ErrorCode KeyMaster4AttestationFuzzer::generateKey(const AuthorizationSet& key_desc,
hidl_vec<uint8_t>* keyBlob,
KeyCharacteristics* keyCharacteristics) {
ErrorCode error;
mKeymaster->generateKey(key_desc.hidl_data(),
[&](ErrorCode hidlError, const hidl_vec<uint8_t>& hidlKeyBlob,
const KeyCharacteristics& hidlKeyCharacteristics) {
error = hidlError;
*keyBlob = hidlKeyBlob;
*keyCharacteristics = hidlKeyCharacteristics;
});
return error;
}
ErrorCode KeyMaster4AttestationFuzzer::attestKey(hidl_vec<uint8_t>& keyBlob,
const AuthorizationSet& attestParams,
hidl_vec<hidl_vec<uint8_t>>* certificateChain) {
ErrorCode error;
auto rc = mKeymaster->attestKey(
keyBlob, attestParams.hidl_data(),
[&](ErrorCode hidlError, const hidl_vec<hidl_vec<uint8_t>>& hidlCertificateChain) {
error = hidlError;
*certificateChain = hidlCertificateChain;
});
if (!rc.isOk()) {
return ErrorCode::UNKNOWN_ERROR;
}
return error;
}
X509_Ptr KeyMaster4AttestationFuzzer::parseCertificateBlob(const hidl_vec<uint8_t>& blob) {
const uint8_t* p = blob.data();
return X509_Ptr(d2i_X509(nullptr, &p, blob.size()));
}
/**
* @brief getAttestationRecord() accepts a 'certificate' pointer and the return value points to the
* data owned by 'certificate'. Hence, 'certificate' should not be freed and the return value cannot
* outlive 'certificate'
*/
ASN1_OCTET_STRING* KeyMaster4AttestationFuzzer::getAttestationRecord(const X509* certificate) {
ASN1_OBJECT_Ptr oid(OBJ_txt2obj(kAttestionRecordOid, 1 /* dotted string format */));
if (!oid.get()) {
return nullptr;
}
int location = X509_get_ext_by_OBJ(certificate, oid.get(), -1 /* search from beginning */);
if (location == -1) {
return nullptr;
}
X509_EXTENSION* attestRecordExt = X509_get_ext(certificate, location);
if (!attestRecordExt) {
return nullptr;
}
ASN1_OCTET_STRING* attestRecord = X509_EXTENSION_get_data(attestRecordExt);
return attestRecord;
}
bool KeyMaster4AttestationFuzzer::verifyAttestationRecord(
const hidl_vec<uint8_t>& attestationCert) {
X509_Ptr cert(parseCertificateBlob(attestationCert));
if (!cert.get()) {
return false;
}
ASN1_OCTET_STRING* attestRecord = getAttestationRecord(cert.get());
if (!attestRecord) {
return false;
}
AuthorizationSet attestationSwEnforced;
AuthorizationSet attestationHwEnforced;
uint32_t attestationVersion;
uint32_t keymasterVersion;
SecurityLevel securityLevel;
SecurityLevel keymasterSecurityLevel;
hidl_vec<uint8_t> attestationChallenge;
hidl_vec<uint8_t> attestationUniqueId;
auto error = parse_attestation_record(
attestRecord->data, attestRecord->length, &attestationVersion, &securityLevel,
&keymasterVersion, &keymasterSecurityLevel, &attestationChallenge,
&attestationSwEnforced, &attestationHwEnforced, &attestationUniqueId);
if (error != ErrorCode::OK) {
return false;
}
hidl_vec<uint8_t> verifiedBootKey;
keymaster_verified_boot_t verifiedBootState;
bool device_locked;
hidl_vec<uint8_t> verifiedBootHash;
parse_root_of_trust(attestRecord->data, attestRecord->length, &verifiedBootKey,
&verifiedBootState, &device_locked, &verifiedBootHash);
return true;
}
void KeyMaster4AttestationFuzzer::invokeAttestationRecord() {
mKeymaster = IKeymasterDevice::getService();
if (!mKeymaster) {
return;
}
hidl_vec<uint8_t> keyBlob;
KeyCharacteristics keyCharacteristics;
generateKey(createAuthorizationSet(mFdp), &keyBlob, &keyCharacteristics);
hidl_vec<hidl_vec<uint8_t>> certificateChain;
std::vector<uint8_t> challenge, attestationId;
challenge =
mFdp->ConsumeBytes<uint8_t>(mFdp->ConsumeIntegralInRange<size_t>(kMinBytes, kMaxBytes));
attestationId =
mFdp->ConsumeBytes<uint8_t>(mFdp->ConsumeIntegralInRange<size_t>(kMinBytes, kMaxBytes));
attestKey(keyBlob,
AuthorizationSetBuilder()
.Authorization(TAG_ATTESTATION_CHALLENGE, challenge)
.Authorization(TAG_ATTESTATION_APPLICATION_ID, attestationId),
&certificateChain);
if (certificateChain.size() > 0) {
verifyAttestationRecord(certificateChain[mFdp->ConsumeIntegralInRange<size_t>(
0, certificateChain.size() - 1)]);
}
}
void KeyMaster4AttestationFuzzer::process(const uint8_t* data, size_t size) {
mFdp = std::make_unique<FuzzedDataProvider>(data, size);
invokeAttestationRecord();
}
extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
KeyMaster4AttestationFuzzer km4AttestationFuzzer;
km4AttestationFuzzer.process(data, size);
return 0;
}
} // namespace android::hardware::keymaster::V4_0::fuzzer
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