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/*
* Copyright (c) 2019, 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 <iterator>
#include <tuple>
#include <android-base/properties.h>
#include <cppbor.h>
#include <json/json.h>
#include <openssl/base64.h>
#include <openssl/rand.h>
#include <remote_prov/remote_prov_utils.h>
namespace aidl::android::hardware::security::keymint::remote_prov {
bytevec kTestMacKey(32 /* count */, 0 /* byte value */);
bytevec randomBytes(size_t numBytes) {
bytevec retval(numBytes);
RAND_bytes(retval.data(), numBytes);
return retval;
}
ErrMsgOr<EekChain> generateEekChain(size_t length, const bytevec& eekId) {
if (length < 2) {
return "EEK chain must contain at least 2 certs.";
}
auto eekChain = cppbor::Array();
bytevec prev_priv_key;
for (size_t i = 0; i < length - 1; ++i) {
bytevec pub_key(ED25519_PUBLIC_KEY_LEN);
bytevec priv_key(ED25519_PRIVATE_KEY_LEN);
ED25519_keypair(pub_key.data(), priv_key.data());
// The first signing key is self-signed.
if (prev_priv_key.empty()) prev_priv_key = priv_key;
auto coseSign1 = constructCoseSign1(prev_priv_key,
cppbor::Map() /* payload CoseKey */
.add(CoseKey::KEY_TYPE, OCTET_KEY_PAIR)
.add(CoseKey::ALGORITHM, EDDSA)
.add(CoseKey::CURVE, ED25519)
.add(CoseKey::PUBKEY_X, pub_key)
.canonicalize()
.encode(),
{} /* AAD */);
if (!coseSign1) return coseSign1.moveMessage();
eekChain.add(coseSign1.moveValue());
prev_priv_key = priv_key;
}
bytevec pub_key(X25519_PUBLIC_VALUE_LEN);
bytevec priv_key(X25519_PRIVATE_KEY_LEN);
X25519_keypair(pub_key.data(), priv_key.data());
auto coseSign1 = constructCoseSign1(prev_priv_key,
cppbor::Map() /* payload CoseKey */
.add(CoseKey::KEY_TYPE, OCTET_KEY_PAIR)
.add(CoseKey::KEY_ID, eekId)
.add(CoseKey::ALGORITHM, ECDH_ES_HKDF_256)
.add(CoseKey::CURVE, cppcose::X25519)
.add(CoseKey::PUBKEY_X, pub_key)
.canonicalize()
.encode(),
{} /* AAD */);
if (!coseSign1) return coseSign1.moveMessage();
eekChain.add(coseSign1.moveValue());
return EekChain{eekChain.encode(), pub_key, priv_key};
}
bytevec getProdEekChain() {
bytevec prodEek;
prodEek.reserve(1 + sizeof(kCoseEncodedRootCert) + sizeof(kCoseEncodedGeekCert));
// In CBOR encoding, 0x82 indicates an array of two items
prodEek.push_back(0x82);
prodEek.insert(prodEek.end(), std::begin(kCoseEncodedRootCert), std::end(kCoseEncodedRootCert));
prodEek.insert(prodEek.end(), std::begin(kCoseEncodedGeekCert), std::end(kCoseEncodedGeekCert));
return prodEek;
}
ErrMsgOr<bytevec> verifyAndParseCoseSign1Cwt(const cppbor::Array* coseSign1,
const bytevec& signingCoseKey, const bytevec& aad) {
if (!coseSign1 || coseSign1->size() != kCoseSign1EntryCount) {
return "Invalid COSE_Sign1";
}
const cppbor::Bstr* protectedParams = coseSign1->get(kCoseSign1ProtectedParams)->asBstr();
const cppbor::Map* unprotectedParams = coseSign1->get(kCoseSign1UnprotectedParams)->asMap();
const cppbor::Bstr* payload = coseSign1->get(kCoseSign1Payload)->asBstr();
const cppbor::Bstr* signature = coseSign1->get(kCoseSign1Signature)->asBstr();
if (!protectedParams || !unprotectedParams || !payload || !signature) {
return "Invalid COSE_Sign1";
}
auto [parsedProtParams, _, errMsg] = cppbor::parse(protectedParams);
if (!parsedProtParams) {
return errMsg + " when parsing protected params.";
}
if (!parsedProtParams->asMap()) {
return "Protected params must be a map";
}
auto& algorithm = parsedProtParams->asMap()->get(ALGORITHM);
if (!algorithm || !algorithm->asInt() || algorithm->asInt()->value() != EDDSA) {
return "Unsupported signature algorithm";
}
// TODO(jbires): Handle CWTs as the CoseSign1 payload in a less hacky way. Since the CWT payload
// is extremely remote provisioning specific, probably just make a separate
// function there.
auto [parsedPayload, __, payloadErrMsg] = cppbor::parse(payload);
if (!parsedPayload) return payloadErrMsg + " when parsing key";
if (!parsedPayload->asMap()) return "CWT must be a map";
auto serializedKey = parsedPayload->asMap()->get(-4670552)->clone();
if (!serializedKey || !serializedKey->asBstr()) return "Could not find key entry";
bool selfSigned = signingCoseKey.empty();
auto key =
CoseKey::parseEd25519(selfSigned ? serializedKey->asBstr()->value() : signingCoseKey);
if (!key) return "Bad signing key: " + key.moveMessage();
bytevec signatureInput =
cppbor::Array().add("Signature1").add(*protectedParams).add(aad).add(*payload).encode();
if (!ED25519_verify(signatureInput.data(), signatureInput.size(), signature->value().data(),
key->getBstrValue(CoseKey::PUBKEY_X)->data())) {
return "Signature verification failed";
}
return serializedKey->asBstr()->value();
}
ErrMsgOr<std::vector<BccEntryData>> validateBcc(const cppbor::Array* bcc) {
if (!bcc || bcc->size() == 0) return "Invalid BCC";
std::vector<BccEntryData> result;
bytevec prevKey;
// TODO(jbires): Actually process the pubKey at the start of the new bcc entry
for (size_t i = 1; i < bcc->size(); ++i) {
const cppbor::Array* entry = bcc->get(i)->asArray();
if (!entry || entry->size() != kCoseSign1EntryCount) {
return "Invalid BCC entry " + std::to_string(i) + ": " + prettyPrint(entry);
}
auto payload = verifyAndParseCoseSign1Cwt(entry, std::move(prevKey), bytevec{} /* AAD */);
if (!payload) {
return "Failed to verify entry " + std::to_string(i) + ": " + payload.moveMessage();
}
auto& certProtParms = entry->get(kCoseSign1ProtectedParams);
if (!certProtParms || !certProtParms->asBstr()) return "Invalid prot params";
auto [parsedProtParms, _, errMsg] = cppbor::parse(certProtParms->asBstr()->value());
if (!parsedProtParms || !parsedProtParms->asMap()) return "Invalid prot params";
result.push_back(BccEntryData{*payload});
// This entry's public key is the signing key for the next entry.
prevKey = payload.moveValue();
}
return result;
}
JsonOutput jsonEncodeCsrWithBuild(const cppbor::Array& csr) {
const std::string kFingerprintProp = "ro.build.fingerprint";
if (!::android::base::WaitForPropertyCreation(kFingerprintProp)) {
return JsonOutput::Error("Unable to read build fingerprint");
}
bytevec csrCbor = csr.encode();
size_t base64Length;
int rc = EVP_EncodedLength(&base64Length, csrCbor.size());
if (!rc) {
return JsonOutput::Error("Error getting base64 length. Size overflow?");
}
std::vector<char> base64(base64Length);
rc = EVP_EncodeBlock(reinterpret_cast<uint8_t*>(base64.data()), csrCbor.data(), csrCbor.size());
++rc; // Account for NUL, which BoringSSL does not for some reason.
if (rc != base64Length) {
return JsonOutput::Error("Error writing base64. Expected " + std::to_string(base64Length) +
" bytes to be written, but " + std::to_string(rc) +
" bytes were actually written.");
}
Json::Value json(Json::objectValue);
json["build_fingerprint"] = ::android::base::GetProperty(kFingerprintProp, /*default=*/"");
json["csr"] = base64.data(); // Boring writes a NUL-terminated c-string
Json::StreamWriterBuilder factory;
factory["indentation"] = ""; // disable pretty formatting
return JsonOutput::Ok(Json::writeString(factory, json));
}
} // namespace aidl::android::hardware::security::keymint::remote_prov
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