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Feature: encrypt the connection between game server and client

This commit is contained in:
Rubidium 2024-03-14 21:36:28 +01:00 committed by rubidium42
parent d26629c15b
commit 1cf8799810
12 changed files with 143 additions and 33 deletions
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6
src/network/core/core.h
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@ -13,6 +13,7 @@
#define NETWORK_CORE_CORE_H
#include "../../newgrf_config.h"
#include "../network_crypto.h"
#include "config.h"
bool NetworkCoreInitialize();
@ -43,6 +44,11 @@ class NetworkSocketHandler {
private:
bool has_quit; ///< Whether the current client has quit/send a bad packet
protected:
friend struct Packet;
std::unique_ptr<class NetworkEncryptionHandler> receive_encryption_handler; ///< The handler for decrypting received packets.
std::unique_ptr<class NetworkEncryptionHandler> send_encryption_handler; ///< The handler for encrypting sent packets.
public:
/** Create a new unbound socket */
NetworkSocketHandler() { this->has_quit = false; }

32
src/network/core/packet.cpp
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@ -48,7 +48,14 @@ Packet::Packet(NetworkSocketHandler *cs, size_t limit, size_t initial_read_size)
Packet::Packet(NetworkSocketHandler *cs, PacketType type, size_t limit) : pos(0), limit(limit), cs(cs)
{
/* Allocate space for the the size so we can write that in just before sending the packet. */
this->Send_uint16(0);
size_t size = EncodedLengthOfPacketSize();
if (cs != nullptr && cs->send_encryption_handler != nullptr) {
/* Allocate some space for the message authentication code of the encryption. */
size += cs->send_encryption_handler->MACSize();
}
assert(this->CanWriteToPacket(size));
this->buffer.resize(size, 0);
this->Send_uint8(type);
}
@ -64,6 +71,13 @@ void Packet::PrepareToSend()
this->buffer[0] = GB(this->Size(), 0, 8);
this->buffer[1] = GB(this->Size(), 8, 8);
if (cs != nullptr && cs->send_encryption_handler != nullptr) {
size_t offset = EncodedLengthOfPacketSize();
size_t mac_size = cs->send_encryption_handler->MACSize();
size_t message_offset = offset + mac_size;
cs->send_encryption_handler->Encrypt(std::span(&this->buffer[offset], mac_size), std::span(&this->buffer[message_offset], this->buffer.size() - message_offset));
}
this->pos = 0; // We start reading from here
this->buffer.shrink_to_fit();
}
@ -259,11 +273,21 @@ bool Packet::ParsePacketSize()
/**
* Prepares the packet so it can be read
* @return True when the packet was valid, otherwise false.
*/
void Packet::PrepareToRead()
bool Packet::PrepareToRead()
{
/* Put the position on the right place */
this->pos = static_cast<PacketSize>(EncodedLengthOfPacketSize());
if (cs == nullptr || cs->receive_encryption_handler == nullptr) return true;
size_t mac_size = cs->receive_encryption_handler->MACSize();
if (this->buffer.size() <= pos + mac_size) return false;
bool valid = cs->receive_encryption_handler->Decrypt(std::span(&this->buffer[pos], mac_size), std::span(&this->buffer[pos + mac_size], this->buffer.size() - pos - mac_size));
this->pos += static_cast<PacketSize>(mac_size);
return valid;
}
/**
@ -273,7 +297,9 @@ void Packet::PrepareToRead()
PacketType Packet::GetPacketType() const
{
assert(this->Size() >= EncodedLengthOfPacketSize() + EncodedLengthOfPacketType());
return static_cast<PacketType>(buffer[EncodedLengthOfPacketSize()]);
size_t offset = EncodedLengthOfPacketSize();
if (cs != nullptr && cs->send_encryption_handler != nullptr) offset += cs->send_encryption_handler->MACSize();
return static_cast<PacketType>(buffer[offset]);
}
/**

2
src/network/core/packet.h
View File

@ -74,7 +74,7 @@ public:
bool HasPacketSizeData() const;
bool ParsePacketSize();
size_t Size() const;
void PrepareToRead();
[[nodiscard]] bool PrepareToRead();
PacketType GetPacketType() const;
bool CanReadFromPacket(size_t bytes_to_read, bool close_connection = false);

6
src/network/core/tcp.cpp
View File

@ -188,7 +188,11 @@ std::unique_ptr<Packet> NetworkTCPSocketHandler::ReceivePacket()
}
}
p.PrepareToRead();
if (!p.PrepareToRead()) {
Debug(net, 0, "Invalid packet received (too small / decryption error)");
this->CloseConnection();
return nullptr;
}
return std::move(this->packet_recv);
}

4
src/network/core/tcp_game.cpp
View File

@ -85,7 +85,7 @@ NetworkRecvStatus NetworkGameSocketHandler::HandlePacket(Packet &p)
case PACKET_SERVER_AUTH_REQUEST: return this->Receive_SERVER_AUTH_REQUEST(p);
case PACKET_SERVER_NEED_COMPANY_PASSWORD: return this->Receive_SERVER_NEED_COMPANY_PASSWORD(p);
case PACKET_CLIENT_AUTH_RESPONSE: return this->Receive_CLIENT_AUTH_RESPONSE(p);
case PACKET_SERVER_AUTH_COMPLETED: return this->Receive_SERVER_AUTH_COMPLETED(p);
case PACKET_SERVER_ENABLE_ENCRYPTION: return this->Receive_SERVER_ENABLE_ENCRYPTION(p);
case PACKET_CLIENT_COMPANY_PASSWORD: return this->Receive_CLIENT_COMPANY_PASSWORD(p);
case PACKET_SERVER_WELCOME: return this->Receive_SERVER_WELCOME(p);
case PACKET_CLIENT_GETMAP: return this->Receive_CLIENT_GETMAP(p);
@ -168,7 +168,7 @@ NetworkRecvStatus NetworkGameSocketHandler::Receive_CLIENT_IDENTIFY(Packet &) {
NetworkRecvStatus NetworkGameSocketHandler::Receive_SERVER_AUTH_REQUEST(Packet &) { return this->ReceiveInvalidPacket(PACKET_SERVER_AUTH_REQUEST); }
NetworkRecvStatus NetworkGameSocketHandler::Receive_SERVER_NEED_COMPANY_PASSWORD(Packet &) { return this->ReceiveInvalidPacket(PACKET_SERVER_NEED_COMPANY_PASSWORD); }
NetworkRecvStatus NetworkGameSocketHandler::Receive_CLIENT_AUTH_RESPONSE(Packet &) { return this->ReceiveInvalidPacket(PACKET_CLIENT_AUTH_RESPONSE); }
NetworkRecvStatus NetworkGameSocketHandler::Receive_SERVER_AUTH_COMPLETED(Packet &) { return this->ReceiveInvalidPacket(PACKET_SERVER_AUTH_COMPLETED); }
NetworkRecvStatus NetworkGameSocketHandler::Receive_SERVER_ENABLE_ENCRYPTION(Packet &) { return this->ReceiveInvalidPacket(PACKET_SERVER_ENABLE_ENCRYPTION); }
NetworkRecvStatus NetworkGameSocketHandler::Receive_CLIENT_COMPANY_PASSWORD(Packet &) { return this->ReceiveInvalidPacket(PACKET_CLIENT_COMPANY_PASSWORD); }
NetworkRecvStatus NetworkGameSocketHandler::Receive_SERVER_WELCOME(Packet &) { return this->ReceiveInvalidPacket(PACKET_SERVER_WELCOME); }
NetworkRecvStatus NetworkGameSocketHandler::Receive_CLIENT_GETMAP(Packet &) { return this->ReceiveInvalidPacket(PACKET_CLIENT_GETMAP); }

7
src/network/core/tcp_game.h
View File

@ -15,7 +15,6 @@
#include "os_abstraction.h"
#include "tcp.h"
#include "../network_type.h"
#include "../network_crypto.h"
#include "../../core/pool_type.hpp"
#include <chrono>
@ -60,7 +59,7 @@ enum PacketGameType : uint8_t {
/* After the join step, the first perform game authentication and enabling encryption. */
PACKET_SERVER_AUTH_REQUEST, ///< The server requests the client to authenticate using a number of methods.
PACKET_CLIENT_AUTH_RESPONSE, ///< The client responds to the authentication request.
PACKET_SERVER_AUTH_COMPLETED, ///< The server indicates the authentication is completed.
PACKET_SERVER_ENABLE_ENCRYPTION, ///< The server tells that authentication has completed and requests to enable encryption with the keys of the last \c PACKET_CLIENT_AUTH_RESPONSE.
/* After the authentication is done, the next step is identification. */
PACKET_CLIENT_IDENTIFY, ///< Client telling the server the client's name and requested company.
@ -244,10 +243,10 @@ protected:
virtual NetworkRecvStatus Receive_CLIENT_AUTH_RESPONSE(Packet &p);
/**
* Indication to the client that authentication has completed.
* Indication to the client that authentication is complete and encryption has to be used from here on forward.
* @param p The packet that was just received.
*/
virtual NetworkRecvStatus Receive_SERVER_AUTH_COMPLETED(Packet &p);
virtual NetworkRecvStatus Receive_SERVER_ENABLE_ENCRYPTION(Packet &p);
/**
* Send a password to the server to authorize

5
src/network/core/udp.cpp
View File

@ -137,7 +137,10 @@ void NetworkUDPSocketHandler::ReceivePackets()
Debug(net, 1, "Received a packet with mismatching size from {}", address.GetAddressAsString());
continue;
}
p.PrepareToRead();
if (!p.PrepareToRead()) {
Debug(net, 1, "Invalid packet received (too small / decryption error)");
continue;
}
/* Handle the packet */
this->HandleUDPPacket(p, address);

16
src/network/network_client.cpp
View File

@ -707,7 +707,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_ERROR(Packet &p
NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_CHECK_NEWGRFS(Packet &p)
{
if (this->status != STATUS_AUTHENTICATED) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
if (this->status != STATUS_ENCRYPTED) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
uint grf_count = p.Recv_uint8();
NetworkRecvStatus ret = NETWORK_RECV_STATUS_OKAY;
@ -775,16 +775,18 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_AUTH_REQUEST(Pa
}
}
NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_AUTH_COMPLETED(Packet &)
NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_ENABLE_ENCRYPTION(Packet &)
{
if (this->status != STATUS_AUTH_GAME || this->authentication_handler == nullptr) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
Debug(net, 9, "Client::Receive_SERVER_AUTH_COMPLETED()");
Debug(net, 9, "Client::Receive_SERVER_ENABLE_ENCRYPTION()");
this->receive_encryption_handler = this->authentication_handler->CreateServerToClientEncryptionHandler();
this->send_encryption_handler = this->authentication_handler->CreateClientToServerEncryptionHandler();
this->authentication_handler = nullptr;
Debug(net, 9, "Client::status = AUTHENTICATED");
this->status = STATUS_AUTHENTICATED;
Debug(net, 9, "Client::status = ENCRYPTED");
this->status = STATUS_ENCRYPTED;
return this->SendIdentify();
}
@ -798,7 +800,7 @@ class CompanyPasswordRequest : public NetworkAuthenticationPasswordRequest {
NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_NEED_COMPANY_PASSWORD(Packet &p)
{
if (this->status < STATUS_AUTHENTICATED || this->status >= STATUS_AUTH_COMPANY) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
if (this->status < STATUS_ENCRYPTED || this->status >= STATUS_AUTH_COMPANY) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
Debug(net, 9, "Client::status = AUTH_COMPANY");
this->status = STATUS_AUTH_COMPANY;
@ -819,7 +821,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_NEED_COMPANY_PA
NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_WELCOME(Packet &p)
{
if (this->status < STATUS_AUTHENTICATED || this->status >= STATUS_AUTHORIZED) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
if (this->status < STATUS_ENCRYPTED || this->status >= STATUS_AUTHORIZED) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
Debug(net, 9, "Client::status = AUTHORIZED");
this->status = STATUS_AUTHORIZED;

4
src/network/network_client.h
View File

@ -25,7 +25,7 @@ private:
STATUS_INACTIVE, ///< The client is not connected nor active.
STATUS_JOIN, ///< We are trying to join a server.
STATUS_AUTH_GAME, ///< Last action was requesting game (server) password.
STATUS_AUTHENTICATED, ///< The game authentication has completed.
STATUS_ENCRYPTED, ///< The game authentication has completed and from here on the connection to the server is encrypted.
STATUS_NEWGRFS_CHECK, ///< Last action was checking NewGRFs.
STATUS_AUTH_COMPANY, ///< Last action was requesting company password.
STATUS_AUTHORIZED, ///< The client is authorized at the server.
@ -47,7 +47,7 @@ protected:
NetworkRecvStatus Receive_SERVER_ERROR(Packet &p) override;
NetworkRecvStatus Receive_SERVER_CLIENT_INFO(Packet &p) override;
NetworkRecvStatus Receive_SERVER_AUTH_REQUEST(Packet &p) override;
NetworkRecvStatus Receive_SERVER_AUTH_COMPLETED(Packet &p) override;
NetworkRecvStatus Receive_SERVER_ENABLE_ENCRYPTION(Packet &p) override;
NetworkRecvStatus Receive_SERVER_NEED_COMPANY_PASSWORD(Packet &p) override;
NetworkRecvStatus Receive_SERVER_WELCOME(Packet &p) override;
NetworkRecvStatus Receive_SERVER_WAIT(Packet &p) override;

12
src/network/network_server.cpp
View File

@ -457,15 +457,15 @@ NetworkRecvStatus ServerNetworkGameSocketHandler::SendAuthRequest()
return NETWORK_RECV_STATUS_OKAY;
}
/** Notify the client that the authentication has completed. */
NetworkRecvStatus ServerNetworkGameSocketHandler::SendAuthCompleted()
/** Notify the client that the authentication has completed and tell that for the remainder of this socket encryption is enabled. */
NetworkRecvStatus ServerNetworkGameSocketHandler::SendEnableEncryption()
{
Debug(net, 9, "client[{}] SendAuthCompleted()", this->client_id);
Debug(net, 9, "client[{}] SendEnableEncryption()", this->client_id);
/* Invalid packet when status is anything but STATUS_AUTH_GAME. */
if (this->status != STATUS_AUTH_GAME) return this->CloseConnection(NETWORK_RECV_STATUS_MALFORMED_PACKET);
auto p = std::make_unique<Packet>(this, PACKET_SERVER_AUTH_COMPLETED);
auto p = std::make_unique<Packet>(this, PACKET_SERVER_ENABLE_ENCRYPTION);
this->SendPacket(std::move(p));
return NETWORK_RECV_STATUS_OKAY;
}
@ -999,9 +999,11 @@ NetworkRecvStatus ServerNetworkGameSocketHandler::Receive_CLIENT_AUTH_RESPONSE(P
return this->SendError(GetErrorForAuthenticationMethod(authentication_method));
}
NetworkRecvStatus status = this->SendAuthCompleted();
NetworkRecvStatus status = this->SendEnableEncryption();
if (status != NETWORK_RECV_STATUS_OKAY) return status;
this->receive_encryption_handler = this->authentication_handler->CreateClientToServerEncryptionHandler();
this->send_encryption_handler = this->authentication_handler->CreateServerToClientEncryptionHandler();
this->authentication_handler = nullptr;
Debug(net, 9, "client[{}] status = IDENTIFY", this->client_id);

2
src/network/network_server.h
View File

@ -47,7 +47,7 @@ protected:
NetworkRecvStatus SendNewGRFCheck();
NetworkRecvStatus SendWelcome();
NetworkRecvStatus SendAuthRequest();
NetworkRecvStatus SendAuthCompleted();
NetworkRecvStatus SendEnableEncryption();
NetworkRecvStatus SendNeedCompanyPassword();
public:

80
src/tests/test_network_crypto.cpp
View File

@ -20,15 +20,21 @@
static_assert(NETWORK_SECRET_KEY_LENGTH >= X25519_KEY_SIZE * 2 + 1);
class MockNetworkSocketHandler : public NetworkSocketHandler {
public:
MockNetworkSocketHandler(std::unique_ptr<NetworkEncryptionHandler> &&receive = {}, std::unique_ptr<NetworkEncryptionHandler> &&send = {})
{
this->receive_encryption_handler = std::move(receive);
this->send_encryption_handler = std::move(send);
}
};
static MockNetworkSocketHandler mock_socket_handler;
static Packet CreatePacketForReading(Packet &source)
static std::tuple<Packet, bool> CreatePacketForReading(Packet &source, MockNetworkSocketHandler *socket_handler)
{
source.PrepareToSend();
Packet dest(&mock_socket_handler, COMPAT_MTU, source.Size());
Packet dest(socket_handler, COMPAT_MTU, source.Size());
auto transfer_in = [](Packet &source, char *dest_data, size_t length) {
auto transfer_out = [](char *dest_data, const char *source_data, size_t length) {
@ -39,9 +45,9 @@ static Packet CreatePacketForReading(Packet &source)
};
dest.TransferIn(transfer_in, source);
dest.PrepareToRead();
bool valid = dest.PrepareToRead();
dest.Recv_uint8(); // Ignore the type
return dest;
return { dest, valid };
}
class TestPasswordRequestHandler : public NetworkAuthenticationPasswordRequestHandler {
@ -60,13 +66,16 @@ static void TestAuthentication(NetworkAuthenticationServerHandler &server, Netwo
Packet request(&mock_socket_handler, PacketType{});
server.SendRequest(request);
request = CreatePacketForReading(request);
bool valid;
std::tie(request, valid) = CreatePacketForReading(request, &mock_socket_handler);
CHECK(valid);
CHECK(client.ReceiveRequest(request) == expected_request_result);
Packet response(&mock_socket_handler, PacketType{});
client.SendResponse(response);
response = CreatePacketForReading(response);
std::tie(response, valid) = CreatePacketForReading(response, &mock_socket_handler);
CHECK(valid);
CHECK(server.ReceiveResponse(response) == expected_response_result);
}
@ -200,3 +209,62 @@ TEST_CASE("Authentication_Combined")
TestAuthentication(*server, *client, NetworkAuthenticationServerHandler::AUTHENTICATED, NetworkAuthenticationClientHandler::READY_FOR_RESPONSE);
}
}
static void CheckEncryption(MockNetworkSocketHandler *sending_socket_handler, MockNetworkSocketHandler *receiving_socket_handler)
{
PacketType sent_packet_type{ 1 };
uint64_t sent_value = 0x1234567890ABCDEF;
std::set<PacketType> encrypted_packet_types;
for (int i = 0; i < 10; i++) {
Packet request(sending_socket_handler, sent_packet_type);
request.Send_uint64(sent_value);
auto [response, valid] = CreatePacketForReading(request, receiving_socket_handler);
CHECK(valid);
CHECK(response.Recv_uint64() == sent_value);
encrypted_packet_types.insert(request.GetPacketType());
}
/*
* Check whether it looks like encryption has happened. This is done by checking the value
* of the packet type after encryption. If after a few iterations more than one encrypted
* value has been seen, then we know that some type of encryption/scrambling is happening.
*
* Technically this check could fail erroneously when 16 subsequent encryptions yield the
* same encrypted packet type. However, with encryption that byte should have random value
* value, so the chance of this happening are tiny given enough iterations.
* Roughly in the order of 2**((iterations - 1) * 8), which with 10 iterations is in the
* one-in-sextillion (10**21) order of magnitude.
*/
CHECK(encrypted_packet_types.size() != 1);
}
TEST_CASE("Encryption handling")
{
X25519KeyExchangeOnlyServerHandler server(X25519SecretKey::CreateRandom());
X25519KeyExchangeOnlyClientHandler client(X25519SecretKey::CreateRandom());
TestAuthentication(server, client, NetworkAuthenticationServerHandler::AUTHENTICATED, NetworkAuthenticationClientHandler::READY_FOR_RESPONSE);
MockNetworkSocketHandler server_socket_handler(server.CreateClientToServerEncryptionHandler(), server.CreateServerToClientEncryptionHandler());
MockNetworkSocketHandler client_socket_handler(client.CreateServerToClientEncryptionHandler(), client.CreateClientToServerEncryptionHandler());
SECTION("Encyption happening client -> server") {
CheckEncryption(&client_socket_handler, &server_socket_handler);
}
SECTION("Encyption happening server -> client") {
CheckEncryption(&server_socket_handler, &client_socket_handler);
}
SECTION("Unencrypted packet sent causes invalid read packet") {
Packet request(&mock_socket_handler, PacketType{});
request.Send_uint64(0);
auto [response, valid] = CreatePacketForReading(request, &client_socket_handler);
CHECK(!valid);
}
}