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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "cast/receiver/channel/device_auth_namespace_handler.h"
#include <openssl/evp.h>
#include <memory>
#include <utility>
#include "cast/common/certificate/cast_cert_validator.h"
#include "cast/common/channel/message_util.h"
#include "cast/common/channel/proto/cast_channel.pb.h"
#include "cast/common/channel/virtual_connection.h"
#include "cast/common/channel/virtual_connection_router.h"
#include "platform/base/tls_credentials.h"
#include "util/crypto/digest_sign.h"
using ::cast::channel::AuthChallenge;
using ::cast::channel::AuthError;
using ::cast::channel::AuthResponse;
using ::cast::channel::CastMessage;
using ::cast::channel::DeviceAuthMessage;
using ::cast::channel::HashAlgorithm;
using ::cast::channel::SignatureAlgorithm;
namespace openscreen {
namespace cast {
namespace {
CastMessage GenerateErrorMessage(AuthError::ErrorType error_type) {
DeviceAuthMessage message;
AuthError* error = message.mutable_error();
error->set_error_type(error_type);
std::string payload;
message.SerializeToString(&payload);
CastMessage response;
response.set_protocol_version(
::cast::channel::CastMessage_ProtocolVersion_CASTV2_1_0);
response.set_namespace_(kAuthNamespace);
response.set_payload_type(::cast::channel::CastMessage_PayloadType_BINARY);
response.set_payload_binary(std::move(payload));
return response;
}
} // namespace
DeviceAuthNamespaceHandler::DeviceAuthNamespaceHandler(
CredentialsProvider* creds_provider)
: creds_provider_(creds_provider) {}
DeviceAuthNamespaceHandler::~DeviceAuthNamespaceHandler() = default;
void DeviceAuthNamespaceHandler::OnMessage(VirtualConnectionRouter* router,
CastSocket* socket,
CastMessage message) {
if (!socket) {
return; // Don't handle auth messages from local senders. That's nonsense.
}
if (message.payload_type() !=
::cast::channel::CastMessage_PayloadType_BINARY) {
return;
}
const std::string& payload = message.payload_binary();
DeviceAuthMessage device_auth_message;
if (!device_auth_message.ParseFromArray(payload.data(), payload.length())) {
// TODO(btolsch): Consider all of these cases for future error reporting
// mechanism.
return;
}
if (!device_auth_message.has_challenge()) {
return;
}
if (device_auth_message.has_response() || device_auth_message.has_error()) {
return;
}
const VirtualConnection virtual_conn{
message.destination_id(), message.source_id(), socket->socket_id()};
const AuthChallenge& challenge = device_auth_message.challenge();
const SignatureAlgorithm sig_alg = challenge.signature_algorithm();
HashAlgorithm hash_alg = challenge.hash_algorithm();
// TODO(btolsch): Reconsider supporting SHA1 after further metrics
// investigation.
if ((sig_alg != ::cast::channel::UNSPECIFIED &&
sig_alg != ::cast::channel::RSASSA_PKCS1v15) ||
(hash_alg != ::cast::channel::SHA1 &&
hash_alg != ::cast::channel::SHA256)) {
router->Send(virtual_conn, GenerateErrorMessage(
AuthError::SIGNATURE_ALGORITHM_UNAVAILABLE));
return;
}
const EVP_MD* digest =
hash_alg == ::cast::channel::SHA256 ? EVP_sha256() : EVP_sha1();
const absl::Span<const uint8_t> tls_cert_der =
creds_provider_->GetCurrentTlsCertAsDer();
const DeviceCredentials& device_creds =
creds_provider_->GetCurrentDeviceCredentials();
if (tls_cert_der.empty() || device_creds.certs.empty() ||
!device_creds.private_key) {
// TODO(btolsch): Add this to future error reporting.
router->Send(virtual_conn, GenerateErrorMessage(AuthError::INTERNAL_ERROR));
return;
}
std::unique_ptr<AuthResponse> auth_response(new AuthResponse());
auth_response->set_client_auth_certificate(device_creds.certs[0]);
for (auto it = device_creds.certs.begin() + 1; it != device_creds.certs.end();
++it) {
auth_response->add_intermediate_certificate(*it);
}
auth_response->set_signature_algorithm(::cast::channel::RSASSA_PKCS1v15);
auth_response->set_hash_algorithm(hash_alg);
std::string sender_nonce;
if (challenge.has_sender_nonce()) {
sender_nonce = challenge.sender_nonce();
auth_response->set_sender_nonce(sender_nonce);
}
auth_response->set_crl(device_creds.serialized_crl);
std::vector<uint8_t> to_be_signed;
to_be_signed.reserve(sender_nonce.size() + tls_cert_der.size());
to_be_signed.insert(to_be_signed.end(), sender_nonce.begin(),
sender_nonce.end());
to_be_signed.insert(to_be_signed.end(), tls_cert_der.begin(),
tls_cert_der.end());
ErrorOr<std::string> signature =
SignData(digest, device_creds.private_key.get(), to_be_signed);
if (!signature) {
router->Send(virtual_conn, GenerateErrorMessage(AuthError::INTERNAL_ERROR));
return;
}
auth_response->set_signature(std::move(signature.value()));
DeviceAuthMessage response_auth_message;
response_auth_message.set_allocated_response(auth_response.release());
std::string response_string;
response_auth_message.SerializeToString(&response_string);
CastMessage response;
response.set_protocol_version(
::cast::channel::CastMessage_ProtocolVersion_CASTV2_1_0);
response.set_namespace_(kAuthNamespace);
response.set_payload_type(::cast::channel::CastMessage_PayloadType_BINARY);
response.set_payload_binary(std::move(response_string));
router->Send(virtual_conn, std::move(response));
}
} // namespace cast
} // namespace openscreen
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