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/*
* Copyright 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 <string>
#include <vector>
#include <aidl/android/hardware/security/keymint/IRemotelyProvisionedComponent.h>
#include <android/binder_manager.h>
#include <cppbor.h>
#include <gflags/gflags.h>
#include <keymaster/cppcose/cppcose.h>
#include <openssl/base64.h>
#include <remote_prov/remote_prov_utils.h>
#include <sys/random.h>
using aidl::android::hardware::security::keymint::DeviceInfo;
using aidl::android::hardware::security::keymint::IRemotelyProvisionedComponent;
using aidl::android::hardware::security::keymint::MacedPublicKey;
using aidl::android::hardware::security::keymint::ProtectedData;
using aidl::android::hardware::security::keymint::RpcHardwareInfo;
using aidl::android::hardware::security::keymint::remote_prov::generateEekChain;
using aidl::android::hardware::security::keymint::remote_prov::getProdEekChain;
using aidl::android::hardware::security::keymint::remote_prov::jsonEncodeCsrWithBuild;
using namespace cppbor;
using namespace cppcose;
DEFINE_bool(test_mode, false, "If enabled, a fake EEK key/cert are used.");
DEFINE_string(output_format, "csr", "How to format the output. Defaults to 'csr'.");
namespace {
// Various supported --output_format values.
constexpr std::string_view kBinaryCsrOutput = "csr"; // Just the raw csr as binary
constexpr std::string_view kBuildPlusCsr = "build+csr"; // Text-encoded (JSON) build
// fingerprint plus CSR.
constexpr size_t kChallengeSize = 16;
std::string toBase64(const std::vector<uint8_t>& buffer) {
size_t base64Length;
int rc = EVP_EncodedLength(&base64Length, buffer.size());
if (!rc) {
std::cerr << "Error getting base64 length. Size overflow?" << std::endl;
exit(-1);
}
std::string base64(base64Length, ' ');
rc = EVP_EncodeBlock(reinterpret_cast<uint8_t*>(base64.data()), buffer.data(), buffer.size());
++rc; // Account for NUL, which BoringSSL does not for some reason.
if (rc != base64Length) {
std::cerr << "Error writing base64. Expected " << base64Length
<< " bytes to be written, but " << rc << " bytes were actually written."
<< std::endl;
exit(-1);
}
return base64;
}
std::vector<uint8_t> generateChallenge() {
std::vector<uint8_t> challenge(kChallengeSize);
ssize_t bytesRemaining = static_cast<ssize_t>(challenge.size());
uint8_t* writePtr = challenge.data();
while (bytesRemaining > 0) {
int bytesRead = getrandom(writePtr, bytesRemaining, /*flags=*/0);
if (bytesRead < 0) {
if (errno == EINTR) {
continue;
} else {
std::cerr << errno << ": " << strerror(errno) << std::endl;
exit(-1);
}
}
bytesRemaining -= bytesRead;
writePtr += bytesRead;
}
return challenge;
}
Array composeCertificateRequest(const ProtectedData& protectedData,
const DeviceInfo& verifiedDeviceInfo,
const std::vector<uint8_t>& challenge,
const std::vector<uint8_t>& keysToSignMac) {
Array macedKeysToSign = Array()
.add(std::vector<uint8_t>(0)) // empty protected headers as bstr
.add(Map()) // empty unprotected headers
.add(Null()) // nil for the payload
.add(keysToSignMac); // MAC as returned from the HAL
Array deviceInfo =
Array().add(EncodedItem(verifiedDeviceInfo.deviceInfo)).add(Map()); // Empty device info
Array certificateRequest = Array()
.add(std::move(deviceInfo))
.add(challenge)
.add(EncodedItem(protectedData.protectedData))
.add(std::move(macedKeysToSign));
return certificateRequest;
}
std::vector<uint8_t> getEekChain(uint32_t curve) {
if (FLAGS_test_mode) {
const std::vector<uint8_t> kFakeEekId = {'f', 'a', 'k', 'e', 0};
auto eekOrErr = generateEekChain(curve, 3 /* chainlength */, kFakeEekId);
if (!eekOrErr) {
std::cerr << "Failed to generate test EEK somehow: " << eekOrErr.message() << std::endl;
exit(-1);
}
auto [eek, pubkey, privkey] = eekOrErr.moveValue();
std::cout << "EEK raw keypair:" << std::endl;
std::cout << " pub: " << toBase64(pubkey) << std::endl;
std::cout << " priv: " << toBase64(privkey) << std::endl;
return eek;
}
return getProdEekChain(curve);
}
void writeOutput(const std::string instance_name, const Array& csr) {
if (FLAGS_output_format == kBinaryCsrOutput) {
auto bytes = csr.encode();
std::copy(bytes.begin(), bytes.end(), std::ostream_iterator<char>(std::cout));
} else if (FLAGS_output_format == kBuildPlusCsr) {
auto [json, error] = jsonEncodeCsrWithBuild(instance_name, csr);
if (!error.empty()) {
std::cerr << "Error JSON encoding the output: " << error;
exit(1);
}
std::cout << json << std::endl;
} else {
std::cerr << "Unexpected output_format '" << FLAGS_output_format << "'" << std::endl;
std::cerr << "Valid formats:" << std::endl;
std::cerr << " " << kBinaryCsrOutput << std::endl;
std::cerr << " " << kBuildPlusCsr << std::endl;
exit(1);
}
}
// Callback for AServiceManager_forEachDeclaredInstance that writes out a CSR
// for every IRemotelyProvisionedComponent.
void getCsrForInstance(const char* name, void* /*context*/) {
const std::vector<uint8_t> challenge = generateChallenge();
auto fullName = std::string(IRemotelyProvisionedComponent::descriptor) + "/" + name;
AIBinder* rkpAiBinder = AServiceManager_getService(fullName.c_str());
::ndk::SpAIBinder rkp_binder(rkpAiBinder);
auto rkp_service = IRemotelyProvisionedComponent::fromBinder(rkp_binder);
if (!rkp_service) {
std::cerr << "Unable to get binder object for '" << fullName << "', skipping.";
exit(-1);
}
std::vector<uint8_t> keysToSignMac;
std::vector<MacedPublicKey> emptyKeys;
DeviceInfo verifiedDeviceInfo;
ProtectedData protectedData;
RpcHardwareInfo hwInfo;
::ndk::ScopedAStatus status = rkp_service->getHardwareInfo(&hwInfo);
if (!status.isOk()) {
std::cerr << "Failed to get hardware info for '" << fullName
<< "'. Error code: " << status.getServiceSpecificError() << "." << std::endl;
exit(-1);
}
status = rkp_service->generateCertificateRequest(
FLAGS_test_mode, emptyKeys, getEekChain(hwInfo.supportedEekCurve), challenge,
&verifiedDeviceInfo, &protectedData, &keysToSignMac);
if (!status.isOk()) {
std::cerr << "Bundle extraction failed for '" << fullName
<< "'. Error code: " << status.getServiceSpecificError() << "." << std::endl;
exit(-1);
}
auto request =
composeCertificateRequest(protectedData, verifiedDeviceInfo, challenge, keysToSignMac);
writeOutput(std::string(name), request);
}
} // namespace
int main(int argc, char** argv) {
gflags::ParseCommandLineFlags(&argc, &argv, /*remove_flags=*/true);
AServiceManager_forEachDeclaredInstance(IRemotelyProvisionedComponent::descriptor,
/*context=*/nullptr, getCsrForInstance);
return 0;
}
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