Packet Interceptor

A Win32 hook for the ro client's send() function to intercept and transform outgoing network packets before they reach the target server.

How It Works

1. On DllMain(DLL_PROCESS_ATTACH), the hook installs an inline detour hook on ws2_32.dll's send()
2. Every outgoing send() call passes through send_intercept(), which reads the 2-byte opcode
3. Matching opcodes are dispatched to handler functions, unmatched packets continues to the original send()

Included Sample

• Login packet handler intercepts CA_LOGIN (0x0064), hashes the plaintext password with BLAKE2b-256 using the username as the key, and sends the replacement packet CA_LOGIN_HASHED (0x0C50) to the server.

Building

1. Open interceptor.vcxproj in Visual Studio 2022
2. Select Release | Win32
3. Build — outputs interceptor.dll to build/

Installation

Warp

1. Add the following to DLLSpec.yml:

Name: interceptor.dll
Funcs:
  - Name: "interceptor_init"
  - Ordinal: 1

2. Enable the Add custom DLLs patch

CFF Explorer

1. Open the game executable in CFF Explorer
2. Go to Import Adder
3. Browse and select interceptor.dll
4. Select the interceptor_init function from the export list
5. Click Add then Rebuild Import Table
6. Save the patched executable

Adding New Packet Handlers

1. Define the original and replacement packet structs in packets.hpp
2. Write a handler function in handler.hpp/cpp
3. Add a case to the switch in send_intercept() in interceptor.cpp

Build Requirements

• Visual Studio 2022
• C++17

Tested Client Compatibility

2025-06-04

Disclaimer

Use at your own risk.

Credits

• rAthena — for the packet structures and base type definitions
• skylove - for the client and for the updated warp