1 files changed, 218 insertions, 0 deletions
diff --git a/primedev/server/servernethooks.cpp b/primedev/server/servernethooks.cpp
new file mode 100644
index 00000000..148b735f
--- /dev/null
+++ b/primedev/server/servernethooks.cpp
@@ -0,0 +1,218 @@
+#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;
+
+static BCRYPT_ALG_HANDLE HMACSHA256;
+constexpr size_t HMACSHA256_LEN = 256 / 8;
+
+static bool InitHMACSHA256()
+{
+	NTSTATUS status;
+	DWORD hashLength = 0;
+	ULONG hashLengthSz = 0;
+
+	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;
+}
+
+// compare the HMAC-SHA256(data, key) against sig (note: all strings are treated as raw binary data)
+static bool VerifyHMACSHA256(std::string key, std::string sig, std::string data)
+{
+	uint8_t invalid = 1;
+	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;
+	}
+
+	// constant-time compare
+	if (sig.length() == sizeof(hash))
+	{
+		invalid = 0;
+		for (size_t i = 0; i < sizeof(hash); i++)
+			invalid |= (uint8_t)(sig[i]) ^ (uint8_t)(hash[i]);
+	}
+
+cleanup:
+	if (h)
+		BCryptDestroyHash(h);
+	return !invalid;
+}
+
+// v1 HMACSHA256-signed masterserver request (HMAC-SHA256(JSONData, MasterServerToken) + JSONData)
+static void ProcessAtlasConnectionlessPacketSigreq1(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(&MasterServerManager::ProcessConnectionlessPacketSigreq1, g_pMasterServerManager, pData);
+	t.detach();
+
+	return;
+}
+
+static void ProcessAtlasConnectionlessPacket(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;
+		}
+	}
+
+	// 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
+
+	// 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, netpacket_t* packet))
+{
+	// packet->data consists of 0xFFFFFFFF (int32 -1) to indicate packets aren't split, followed by a header consisting of a single
+	// character, which is used to uniquely identify the packet kind. Most kinds follow this with a null-terminated string payload
+	// then an arbitrary amoount of data.
+
+	// T (no rate limits since we authenticate packets before doing anything expensive)
+	if (4 < packet->size && packet->data[4] == 'T')
+	{
+		ProcessAtlasConnectionlessPacket(packet);
+		return false;
+	}
+
+	// check rate limits for the original unconnected packets
+	if (!g_pServerLimits->CheckConnectionlessPacketLimits(packet))
+		return false;
+
+	// A, H, I, N
+	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)");
+}