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#include "core/convar/convar.h"
#include "engine/r2engine.h"
#include "shared/exploit_fixes/ns_limits.h"
#include "masterserver/masterserver.h"
#include <string>
#include <thread>
#include <bcrypt.h>
AUTOHOOK_INIT()
static ConVar* Cvar_net_debug_atlas_packet;
static ConVar* Cvar_net_debug_atlas_packet_insecure;
#define HMACSHA256_LEN (256 / 8)
BCRYPT_ALG_HANDLE HMACSHA256;
static bool InitHMACSHA256()
{
NTSTATUS status;
DWORD hashLength = NULL;
ULONG hashLengthSz = NULL;
if ((status = BCryptOpenAlgorithmProvider(&HMACSHA256, BCRYPT_SHA256_ALGORITHM, NULL, BCRYPT_ALG_HANDLE_HMAC_FLAG)))
{
spdlog::error("failed to initialize HMAC-SHA256: BCryptOpenAlgorithmProvider: error 0x{:08X}", (ULONG)status);
return false;
}
if ((status = BCryptGetProperty(HMACSHA256, BCRYPT_HASH_LENGTH, (PUCHAR)&hashLength, sizeof(hashLength), &hashLengthSz, 0)))
{
spdlog::error("failed to initialize HMAC-SHA256: BCryptGetProperty(BCRYPT_HASH_LENGTH): error 0x{:08X}", (ULONG)status);
return false;
}
if (hashLength != HMACSHA256_LEN)
{
spdlog::error("failed to initialize HMAC-SHA256: BCryptGetProperty(BCRYPT_HASH_LENGTH): unexpected value {}", hashLength);
return false;
}
return true;
}
// note: all Atlas connectionless packets should be idempotent so multiple attempts can be made to mitigate packet loss
// note: all long-running Atlas connectionless packet handlers should be started in a new thread (with copies of the data) to avoid blocking
// networking
static bool VerifyHMACSHA256(std::string key, std::string sig, std::string data)
{
bool result = false;
char hash[HMACSHA256_LEN];
NTSTATUS status;
BCRYPT_HASH_HANDLE h = NULL;
if ((status = BCryptCreateHash(HMACSHA256, &h, NULL, 0, (PUCHAR)key.c_str(), (ULONG)key.length(), 0)))
{
spdlog::error("failed to verify HMAC-SHA256: BCryptCreateHash: error 0x{:08X}", (ULONG)status);
goto cleanup;
}
if ((status = BCryptHashData(h, (PUCHAR)data.c_str(), (ULONG)data.length(), 0)))
{
spdlog::error("failed to verify HMAC-SHA256: BCryptHashData: error 0x{:08X}", (ULONG)status);
goto cleanup;
}
if ((status = BCryptFinishHash(h, (PUCHAR)&hash, (ULONG)sizeof(hash), 0)))
{
spdlog::error("failed to verify HMAC-SHA256: BCryptFinishHash: error 0x{:08X}", (ULONG)status);
goto cleanup;
}
if (std::string(hash, sizeof(hash)) == sig)
{
result = true;
goto cleanup;
}
cleanup:
if (h)
BCryptDestroyHash(h);
return result;
}
static void ProcessAtlasConnectionlessPacketSigreq1(R2::netpacket_t* packet, bool dbg, std::string pType, std::string pData)
{
if (pData.length() < HMACSHA256_LEN)
{
if (dbg)
spdlog::warn("ignoring Atlas connectionless packet (size={} type={}): invalid: too short for signature", packet->size, pType);
return;
}
std::string pSig; // is binary data, not actually an ASCII string
pSig = pData.substr(0, HMACSHA256_LEN);
pData = pData.substr(HMACSHA256_LEN);
if (!g_pMasterServerManager || !g_pMasterServerManager->m_sOwnServerAuthToken[0])
{
if (dbg)
spdlog::warn(
"ignoring Atlas connectionless packet (size={} type={}): invalid (data={}): no masterserver token yet",
packet->size,
pType,
pData);
return;
}
if (!VerifyHMACSHA256(std::string(g_pMasterServerManager->m_sOwnServerAuthToken), pSig, pData))
{
if (!Cvar_net_debug_atlas_packet_insecure->GetBool())
{
if (dbg)
spdlog::warn(
"ignoring Atlas connectionless packet (size={} type={}): invalid: invalid signature (key={})",
packet->size,
pType,
std::string(g_pMasterServerManager->m_sOwnServerAuthToken));
return;
}
spdlog::warn(
"processing Atlas connectionless packet (size={} type={}) with invalid signature due to net_debug_atlas_packet_insecure",
packet->size,
pType);
}
if (dbg)
spdlog::info("got Atlas connectionless packet (size={} type={} data={})", packet->size, pType, pData);
std::thread t([pData] { g_pMasterServerManager->ProcessConnectionlessPacketSigreq1(pData); });
t.detach();
return;
}
static void ProcessAtlasConnectionlessPacket(R2::netpacket_t* packet)
{
bool dbg = Cvar_net_debug_atlas_packet->GetBool();
// extract kind, null-terminated type, data
std::string pType, pData;
for (int i = 5; i < packet->size; i++)
{
if (packet->data[i] == '\x00')
{
pType.assign((char*)(&packet->data[5]), (size_t)(i - 5));
if (i + 1 < packet->size)
pData.assign((char*)(&packet->data[i + 1]), (size_t)(packet->size - i - 1));
break;
}
}
// v1 HMACSHA256-signed masterserver request
if (pType == "sigreq1")
{
ProcessAtlasConnectionlessPacketSigreq1(packet, dbg, pType, pData);
return;
}
if (dbg)
spdlog::warn("ignoring Atlas connectionless packet (size={} type={}): unknown type", packet->size, pType);
return;
}
AUTOHOOK(ProcessConnectionlessPacket, engine.dll + 0x117800, bool, , (void* a1, R2::netpacket_t* packet))
{
if (4 < packet->size && packet->data[4] == 'T')
{
ProcessAtlasConnectionlessPacket(packet);
return false;
}
if (!g_pServerLimits->CheckConnectionlessPacketLimits(packet))
return false;
return ProcessConnectionlessPacket(a1, packet);
}
ON_DLL_LOAD_RELIESON("engine.dll", ServerNetHooks, ConVar, (CModule module))
{
AUTOHOOK_DISPATCH_MODULE(engine.dll)
if (!InitHMACSHA256())
throw std::runtime_error("failed to initialize bcrypt");
if (!VerifyHMACSHA256(
"test",
"\x88\xcd\x21\x08\xb5\x34\x7d\x97\x3c\xf3\x9c\xdf\x90\x53\xd7\xdd\x42\x70\x48\x76\xd8\xc9\xa9\xbd\x8e\x2d\x16\x82\x59\xd3\xdd"
"\xf7",
"test"))
throw std::runtime_error("bcrypt HMAC-SHA256 is broken");
Cvar_net_debug_atlas_packet = new ConVar(
"net_debug_atlas_packet",
"0",
FCVAR_NONE,
"Whether to log detailed debugging information for Atlas connectionless packets (warning: this allows unlimited amounts of "
"arbitrary data to be logged)");
Cvar_net_debug_atlas_packet_insecure = new ConVar(
"net_debug_atlas_packet_insecure",
"0",
FCVAR_NONE,
"Whether to disable signature verification for Atlas connectionless packets (DANGEROUS: this allows anyone to impersonate Atlas)");
if (Cvar_net_debug_atlas_packet_insecure->GetBool())
spdlog::warn("DANGEROUS: Atlas connectionless packet signature verification disabled; anyone will be able to impersonate Atlas");
}
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