Guide [Source] CS:S x64 — Cheat Communication via Voice Data Sub-Channel

[byte_corvus]

Ever wondered how to sniff out other users of your build on the same server without relying on obvious spinbotting? If you are reversing the current CS:S x64 build, there is a slick way to establish peer-to-peer data exchange right under the server's nose.

The Source Engine server setup is lazy—it forwards CLC_VoiceData to all clients as SVC_VoiceData without inspecting the payload. By embedding a magic marker into these packets, we can identify other instances of our software and share metadata silently.

Technical Architecture
Most community servers are crawling with power-tripping admins who closet cheat. Implementing a stealthy identification system is a standard requirement for any decent private base. You just need to ensure you don't actually trigger the microphone icon permanently.

Critical Offsets & Signatures
Note that for the x64 build of Counter-Strike: Source, the message indices have shifted. In the standard Source 2007 SDK, the index was 9, but it's now 10 due to clc_Move shifts.

Spoiler: Engine Signatures & Layouts

SVC_VoiceData_Process (engine.dll):

48 89 6C 24 10 48 89 74 24 18 57 41 56 41 57 B8 B0 10 00 00

SVC_VoiceData Struct (x64) Details:

1. +0x00: vtable
2. +0x08: CNetMessage base
3. +0x28: int m_nFromClient (client ID)
4. +0x2C: bool m_bProximity
5. +0x30: int m_nLength (bits)
6. +0x40: bf_read descriptor

Implementation Logic
Below is a clean header defining the communication packet and the CLC message wrapper. We use a simple magic dword (0xDEAD1337) to sign our outgoing voice packets.

#define clc_VoiceData 10
#define svc_VoiceData 15

struct comm_packet_t {
    uint32_t magic;
    uint32_t version;
};

class CLC_VoiceData : public CNetMessage {
public:
    int GetType() const { return clc_VoiceData; }
    bool WriteToBuffer(bf_write& buffer) {
        buffer.WriteUBitLong(GetType(), NETMSG_TYPE_BITS);
        m_nLength = m_DataOut.GetNumBitsWritten();
        buffer.WriteUBitLong(m_nLength, 16);
        return buffer.WriteBits(m_DataOut.GetData(), m_nLength);
    }
    // ... members
};

When sending, you must set bVoice=true in the SendNetMsg call, or the engine will silently drop your packet. To avoid getting flagged or annoying other players, throttle your identification broadcast to roughly every 10 seconds (640-ish ticks).

Handling Incoming Packets
When hooking the dispatch, we parse the bitstream to find our magic marker. If it's there, we mark the entity as a fellow user and drop the packet so the engine doesn't try to play garbage audio.

bool CCommunication::on_voice_data_received(void* svc_msg) {
    auto base = reinterpret_cast<uintptr_t>(svc_msg);
    int client_index = *reinterpret_cast<int*>(base + 0x28);
    auto* pData = *reinterpret_cast<unsigned long**>(base + 0x40);
    
    // Bitstream reading logic here...
    uint32_t magic = read_bits(iCurBit, 32);
    if (magic == COMM_MAGIC) {
        m_detected[client_index + 1].detected = true;
        return true; // Packet handled
    }
    return false;
}

Preventive Troubleshooting

1. Mic Icon: It will appear briefly for other players. This is hard to avoid without deeper server-side bypasses.
2. Throttling: If you spam this every tick, the netchannel will overflow or the server will kick you for voice spam.
3. Version Checks: Always include a version field in your comm_packet_t to prevent crashing older builds of your cheat.

Anyone tested this on the latest patch for Steam? Drop your crash logs if the offsets shifted again.