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path: root/NorthstarDLL/server/servernethooks.cpp
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Diffstat (limited to 'NorthstarDLL/server/servernethooks.cpp')
-rw-r--r--NorthstarDLL/server/servernethooks.cpp40
1 files changed, 25 insertions, 15 deletions
diff --git a/NorthstarDLL/server/servernethooks.cpp b/NorthstarDLL/server/servernethooks.cpp
index c367c1e1..905d3251 100644
--- a/NorthstarDLL/server/servernethooks.cpp
+++ b/NorthstarDLL/server/servernethooks.cpp
@@ -12,8 +12,8 @@ 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 BCRYPT_ALG_HANDLE HMACSHA256;
+constexpr size_t HMACSHA256_LEN = 256 / 8;
static bool InitHMACSHA256()
{
@@ -42,13 +42,10 @@ static bool InitHMACSHA256()
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
-
+// 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)
{
- bool result = false;
+ uint8_t invalid = 1;
char hash[HMACSHA256_LEN];
NTSTATUS status;
@@ -72,18 +69,21 @@ static bool VerifyHMACSHA256(std::string key, std::string sig, std::string data)
goto cleanup;
}
- if (std::string(hash, sizeof(hash)) == sig)
+ // constant-time compare
+ if (sig.length() == sizeof(hash))
{
- result = true;
- goto cleanup;
+ 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 result;
+ return !invalid;
}
+// v1 HMACSHA256-signed masterserver request (HMAC-SHA256(JSONData, MasterServerToken) + JSONData)
static void ProcessAtlasConnectionlessPacketSigreq1(R2::netpacket_t* packet, bool dbg, std::string pType, std::string pData)
{
if (pData.length() < HMACSHA256_LEN)
@@ -129,7 +129,7 @@ static void ProcessAtlasConnectionlessPacketSigreq1(R2::netpacket_t* packet, boo
if (dbg)
spdlog::info("got Atlas connectionless packet (size={} type={} data={})", packet->size, pType, pData);
- std::thread t([pData] { g_pMasterServerManager->ProcessConnectionlessPacketSigreq1(pData); });
+ std::thread t(&MasterServerManager::ProcessConnectionlessPacketSigreq1, g_pMasterServerManager, pData);
t.detach();
return;
@@ -152,6 +152,10 @@ static void ProcessAtlasConnectionlessPacket(R2::netpacket_t* packet)
}
}
+ // 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")
{
@@ -166,13 +170,22 @@ static void ProcessAtlasConnectionlessPacket(R2::netpacket_t* packet)
AUTOHOOK(ProcessConnectionlessPacket, engine.dll + 0x117800, bool, , (void* a1, R2::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);
}
@@ -202,7 +215,4 @@ ON_DLL_LOAD_RELIESON("engine.dll", ServerNetHooks, ConVar, (CModule module))
"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");
}