README.md

Custom HTTP/HTTPS Proxy Server (C++)

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Overview

This project implements a fully functional HTTP/HTTPS proxy server in C++ from scratch. The proxy supports standard HTTP requests (via curl -x) and HTTPS traffic using the CONNECT method with secure bidirectional tunneling. It is designed to demonstrate low-level network programming, concurrency, caching, and system-level design concepts.

The proxy acts as an intermediary between clients and remote servers:

• For HTTP, it parses, forwards, caches, and logs requests.
• For HTTPS, it establishes a transparent TCP tunnel without inspecting encrypted data.

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✨ Key Features

HTTP Proxying

• Supports standard HTTP methods (GET, POST, etc.)
• Handles both:
  • origin-form requests (GET /path HTTP/1.1)
  • absolute-form requests (GET http://host/path HTTP/1.1)
• Normalizes host, path, and port before forwarding
• Correctly forwards request headers and bodies

HTTPS Proxying (CONNECT)

• Full support for CONNECT host:port HTTP/1.1
• Establishes a bidirectional TCP tunnel
• Compatible with browsers and curl -x
• Domain-level blocking for HTTPS requests

Correct Content-Length Handling

• Reads request bodies exactly according to Content-Length
• Prevents partial reads and protocol desynchronization
• Essential for correct handling of POST/PUT requests

Streaming Response Forwarding

• Responses are forwarded incrementally as they are received
• No requirement to buffer full responses in memory
• Enables low latency and efficient memory usage

LRU Cache

• Thread-safe Least Recently Used (LRU) cache
• Caches only:
  • HTTP GET requests
  • Successful 200 OK responses
• Cache key:

Domain Blocking

• Configurable via blocked_domains.txt
• Blocks:
• HTTP requests
• HTTPS CONNECT requests
• Enforcement happens before contacting the origin server

Logging

• Structured access logs with:
• Client IP
• Host
• Path or CONNECT
• Status code
• Bytes transferred
• Timestamp
• Uses Log Rotation Strategy

Metrics

• Tracks request counts per host
• Summary printed during graceful shutdown

Concurrency

• Thread-per-connection model
• Each client handled independently
• Shared resources protected using mutexes

Graceful Shutdown

• Handles SIGINT and SIGTERM
• Stops accepting new connections
• Allows active connections to complete
• Flushes logs and prints metrics summary

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Build Instructions

make

This produces the executable proxy in the project root.

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Run

./proxy

The proxy listens on port 8000 by default.

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Testing

# HTTP
curl -x http://localhost:8000 http://example.com

# HTTPS
curl -x http://localhost:8000 https://google.com

# Blocking test
curl -x http://localhost:8000 http://blocked-domain.com

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Blocking Configuration

Edit blocked_domains.txt (project root):

facebook.com
youtube.com

Restart the proxy after changes.

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Logging

Access logs are written to proxy.log or proxy.log.1 in the format:

[TIMESTAMP] CLIENT_IP HOST PATH|CONNECT STATUS_CODE BYTES_TRANSFERRED

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Limitations (Summary)

• No HTTP/2 support
• No TLS inspection or MITM
• HTTPS responses are not cached
• No chunked request decoding

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