Bypass Firewalls

Bypassing Firewalls With Http Tunneling

HTTP tunneling is a technique used to bypass firewalls and network restrictions by encapsulating network traffic within HTTP requests. This method can be particularly useful when you need to access resources or services that are blocked by a firewall. In this article, we’ll explore various HTTP tunneling techniques, tools, and provide practical examples with modern approaches and hardware acceleration.

⚠️

HTTP tunneling can be used to bypass network security measures. Always ensure you have proper authorization and comply with relevant policies and regulations before implementing these techniques. Unauthorized use may result in legal consequences and security breaches.

What is HTTP Tunneling?

HTTP tunneling involves wrapping non-HTTP traffic inside HTTP requests to pass through firewalls that allow HTTP traffic. This technique takes advantage of the fact that most firewalls are configured to allow outbound HTTP traffic on port 80 or HTTPS traffic on port 443.

graph LR
    A[Client] -->|Encrypted HTTP Request| B[Firewall]
    B -->|Allowed| C[HTTP Proxy]
    C -->|Decrypted Tunneled Traffic| D[Destination Server]
    D -->|Response| C
    C -->|Encrypted HTTP Response| B
    B -->|Allowed| A

Modern HTTP Tunneling Techniques

1. Asyncio-based CONNECT Method

Here’s an example of a modern, asyncio-based HTTP tunnel using the CONNECT method:

async_connect_tunnel.py

import asyncio
import aiohttp

async def http_connect_tunnel(host: str, port: int, proxy_url: str):
    async with aiohttp.ClientSession() as session:
        async with session.request(
            "CONNECT",
            f"https://{host}:{port}",
            proxy=proxy_url,
            ssl=False
        ) as response:
            if response.status != 200:
                raise Exception(f"CONNECT failed: {response.status}")

            reader, writer = await asyncio.open_connection(host, port, ssl=False)
            return reader, writer

async def main():
    reader, writer = await http_connect_tunnel('example.com', 443, 'http://proxy.example.com:8080')
    writer.write(b'GET / HTTP/1.1\r\nHost: example.com\r\n\r\n')
    await writer.drain()
    data = await reader.read(4096)
    print(data.decode())
    writer.close()
    await writer.wait_closed()

asyncio.run(main())

2. HTTP/2 Tunneling with hyper

HTTP/2 offers improved performance and multiplexing. Here’s an example using the hyper library:

http2_tunnel.py

from hyper import HTTP20Connection

def http2_tunnel(url: str, proxy_url: str):
    conn = HTTP20Connection(proxy_url, secure=False)
    conn.request('GET', url)
    resp = conn.get_response()
    return resp.read()

# Usage
result = http2_tunnel('https://example.com', 'proxy.example.com:8080')
print(result.decode())

Hardware-accelerated HTTP Tunneling

For high-performance scenarios, we can leverage GPU acceleration using NVIDIA’s CUDA toolkit with PyCUDA:

gpu_http_tunnel.py

import pycuda.driver as cuda
import pycuda.autoinit
from pycuda.compiler import SourceModule
import numpy as np

mod = SourceModule("""
__global__ void encrypt_tunnel(char *data, int len, char *key, int key_len)
{
    int idx = threadIdx.x + blockIdx.x * blockDim.x;
    if (idx < len) {
        data[idx] ^= key[idx % key_len];
    }
}
""")

encrypt_tunnel = mod.get_function("encrypt_tunnel")

def gpu_accelerated_tunnel(data: bytes, key: bytes):
    data_np = np.frombuffer(data, dtype=np.uint8)
    key_np = np.frombuffer(key, dtype=np.uint8)

    data_gpu = cuda.mem_alloc(data_np.nbytes)
    key_gpu = cuda.mem_alloc(key_np.nbytes)

    cuda.memcpy_htod(data_gpu, data_np)
    cuda.memcpy_htod(key_gpu, key_np)

    block_size = 256
    grid_size = (data_np.size + block_size - 1) // block_size

    encrypt_tunnel(
        data_gpu,
        np.int32(data_np.size),
        key_gpu,
        np.int32(key_np.size),
        block=(block_size, 1, 1),
        grid=(grid_size, 1)
    )

    result = np.empty_like(data_np)
    cuda.memcpy_dtoh(result, data_gpu)
    return result.tobytes()

# Usage
data = b"Secret message to be tunneled"
key = b"encryption_key"
encrypted_data = gpu_accelerated_tunnel(data, key)
decrypted_data = gpu_accelerated_tunnel(encrypted_data, key)
print(decrypted_data.decode())

Real-life Example: Secure File Transfer Through Corporate Firewall

Let’s implement a secure file transfer system that uses HTTP tunneling to bypass a corporate firewall:

secure_file_transfer.py

import asyncio
import aiohttp
import aiofiles
import base64
from cryptography.fernet import Fernet
from tqdm import tqdm

class SecureHTTPTunnel:
    def __init__(self, proxy_url: str, encryption_key: bytes):
        self.proxy_url = proxy_url
        self.fernet = Fernet(encryption_key)

    async def send_file(self, file_path: str, destination_url: str):
        async with aiofiles.open(file_path, 'rb') as file:
            content = await file.read()

        encrypted_content = self.fernet.encrypt(content)
        encoded_content = base64.b64encode(encrypted_content).decode()

        async with aiohttp.ClientSession() as session:
            async with session.post(destination_url, proxy=self.proxy_url, json={'file': encoded_content}) as response:
                return await response.text()

    async def receive_file(self, source_url: str, output_path: str):
        async with aiohttp.ClientSession() as session:
            async with session.get(source_url, proxy=self.proxy_url) as response:
                data = await response.json()

        encrypted_content = base64.b64decode(data['file'])
        decrypted_content = self.fernet.decrypt(encrypted_content)

        async with aiofiles.open(output_path, 'wb') as file:
            await file.write(decrypted_content)

async def main():
    proxy_url = 'http://corporate-proxy.example.com:8080'
    encryption_key = Fernet.generate_key()
    tunnel = SecureHTTPTunnel(proxy_url, encryption_key)

    # Sending a file
    with tqdm(total=100, desc="Sending file") as pbar:
        result = await tunnel.send_file('sensitive_document.pdf', 'https://secure-storage.example.com/upload')
        pbar.update(100)
    print(f"Send result: {result}")

    # Receiving a file
    with tqdm(total=100, desc="Receiving file") as pbar:
        await tunnel.receive_file('https://secure-storage.example.com/download', 'received_document.pdf')
        pbar.update(100)
    print("File received successfully")

asyncio.run(main())

This example demonstrates a secure file transfer system that:

Uses HTTP tunneling to bypass corporate firewalls
Encrypts file content before transmission
Utilizes asyncio for efficient I/O operations
Implements progress bars for better user experience

The SecureHTTPTunnel class encapsulates the tunneling and encryption logic, making it easy to send and receive files securely through the corporate proxy.

Performance Considerations

When implementing HTTP tunneling solutions, consider the following performance optimizations:

Use HTTP/2: Leverage multiplexing and header compression for improved efficiency.
Implement Caching: Cache frequently accessed resources to reduce network overhead.
Compress Data: Use compression algorithms like gzip to reduce payload size.
Utilize Connection Pooling: Reuse connections to minimize handshake overhead.

Here’s an example of implementing connection pooling with aiohttp:

connection_pooling.py

import aiohttp
import asyncio

async def pooled_requests(urls):
    conn = aiohttp.TCPConnector(limit=10)  # limit concurrent connections
    async with aiohttp.ClientSession(connector=conn) as session:
        tasks = [fetch(session, url) for url in urls]
        return await asyncio.gather(*tasks)

async def fetch(session, url):
    async with session.get(url) as response:
        return await response.text()

# Usage
urls = ['http://example.com', 'http://example.org', 'http://example.net']
results = asyncio.run(pooled_requests(urls))

Security Considerations

When implementing HTTP tunneling, it’s crucial to address security concerns:

End-to-End Encryption: Always use HTTPS for the entire communication path.
Authentication: Implement strong, multi-factor authentication for tunnel access.
Rate Limiting: Prevent abuse by implementing rate limiting on tunnel requests.
Logging and Monitoring: Maintain detailed logs and set up real-time monitoring for suspicious activities.

Here’s an example of implementing rate limiting using the aiolimiter library:

rate_limiting.py

from aiolimiter import AsyncLimiter
import asyncio
import aiohttp

rate_limiter = AsyncLimiter(10, 1)  # 10 requests per second

async def rate_limited_request(url):
    async with rate_limiter:
        async with aiohttp.ClientSession() as session:
            async with session.get(url) as response:
                return await response.text()

# Usage
urls = ['http://example.com'] * 20
results = asyncio.run(asyncio.gather(*[rate_limited_request(url) for url in urls]))

Conclusion

HTTP tunneling is a powerful technique for bypassing firewalls and accessing restricted resources. By leveraging modern approaches, hardware acceleration, and implementing robust security measures, you can create efficient and secure tunneling solutions. Always ensure compliance with organizational policies and regulations when using these techniques.

For more detailed research on HTTP tunneling and its implications, refer to the following resources:

Remember that while HTTP tunneling can be a valuable tool, it should be used responsibly and with proper authorization to maintain network security and integrity.

Writing Custom Packet Sniffers