High-Performance Local Procedure Call (LPC) System

A C++17-based communication daemon designed for high-performance, networkless Inter-Process Communication (IPC). This system allows local processes (clients and services) to exchange information and execute remote procedures via Unix Named Pipes (FIFOs), similar to gRPC but optimized for single-host environments.

Key Features

• Custom Binary Protocol: Implemented a robust communication protocol with Big-Endian/Host byte order conversion to ensure data integrity across entity handshakes.
• High Concurrency: Utilizes an asynchronous, multi-threaded model (Detached Threads) to manage multiple simultaneous client-service connections without blocking the main event loop.
• I/O Optimization: Leveraged Scatter/Gather I/O (writev) and iovec structures to route large binary payloads between pipes with minimal system call overhead.
• Self-Healing Resource Management: Automated creation and cleanup of FIFO pipes in controlled directories (.dispatcher and .pipes), including symlink fallbacks for environments with restricted permissions.
• System Integrity: Handles system-level constraints such as file descriptor table limits and atomic pipe creation with retry logic.

Implemented Security & Extensions (Bonus)

Beyond the core requirements, this implementation includes advanced security and robustness features:

1. Payload Security Inspection

The dispatcher acts as a security proxy, scanning call payloads for malicious patterns before forwarding them to services.

• Signature Detection: Identifies shellcode indicators like /bin/sh, /bin/bash, and NOP sleds (0x90).
• Syscall Blocking: Detects byte sequences for int 0x80 or syscall to prevent unauthorized kernel access.
• Automatic Quarantine: Blocks suspicious requests and notifies the client with a SECURITY_BLOCKED status.

2. Protocol Extension (Integrity Verification)

Added a custom extension to the install payload for increased robustness:

• Checksum Verification: Utilizes the FNV-1a 32-bit hashing algorithm to verify the checksum of service access paths.
• Flags & Metadata: Supports a 1-byte flag system for future-proofing protocol features while maintaining backward compatibility.

Architecture

The Dispatcher acts as the central orchestration layer:

1. Service Registry: Services register via InstallRequestHeader, exposing an access path.
2. Connection Handshake: Clients request access to a path; the dispatcher creates unique session pipes (call_n and return_n).
3. Procedure Routing: The dispatcher captures, sanitizes, and proxies data between the client and the service.

Tech Stack

• Language: C++17
• Operating System: Linux (Unix System Programming)
• I/O: POSIX Named Pipes (FIFOs), writev, ioctl
• Synchronization: C++ Mutex, Detached Threads

How to Run

1. Build the Project:

   make

2. Start the Dispatcher:

   ./dispatcher

3. Run Tests: Navigate to the checker/ directory and execute ./run_tests.sh.

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Developers:

• Baran Denis-Constantin
• Epure Roberto-Constantin