hcproxy

hcproxy is a lightweight forward HTTP proxy that implements just one HTTP method -- CONNECT.

With decent network drivers tunneling is zero copy, which makes hcproxy fast and efficient. The price for this is 6 file descriptors per connection (client socket, server socket and two pipes).

Requirements

To compile: C++17 compiler.
To run: Linux, libc.
To run as daemon: systemd.

Compiling

git clone https://github.com/romkatv/hcproxy.git
cd hcproxy
make

Installing locally

Install hcproxy as a systemd service:

sudo make install

Verify that the service is running:

$ systemctl status hcproxy
● hcproxy.service - HTTP CONNECT proxy
   Loaded: loaded (/lib/systemd/system/hcproxy.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2018-07-13 13:02:09 UTC; 30s ago
   ...

Try it out:

$ curl -x localhost:8889 https://www.google.com/
<!doctype html>...

If you want to fetch an http URL (rather than https), use -p to force curl to use CONNECT for proxying all traffic:

$ curl -p -x localhost:8889 http://www.google.com/
<!doctype html>...

Installing remotely via SSH

./install-via-ssh certificate.pem user@12.34.56.78

Configuring

To change configuration, you'll need to modify the source code of main() in hcproxy.cc and recompile. For example, here's how you can change the port on which hcproxy listens and the timeout for establishing outgoing connections.

   hcproxy::Options opt;
+  opt.listen_port = 1234;
+  opt.connect_timeout = std::chrono::seconds(30);
   hcproxy::RunProxy(opt);

The list of options, their descriptions and default values can be found in the source code.

The behavior of hcproxy cannot be customized through request headers. It simply ignores all headers.

Using `hcproxy` as web browser proxy

You can use hcproxy as web browser proxy. However, unless you can convince your browser to tunnel all traffic via HTTP CONNECT, fetching plain http URLs won't work. WebSocket (ws and wss protocols) and https will work fine as they always go through CONNECT.

Troubleshooting

If hcproxy doesn't like an incoming request (e.g., it's not a CONNECT) or cannot connect to the downstream server, it simply closes the incoming connection. It never replies with an HTTP error. The only response it ever sends to the client is HTTP 200.

Logs are written to stderr. Severity levels:

INFO: Normal operation.
WARN: Request-related errors such as unparsable content or unresolvable hosts.
ERROR: Abnormal conditions that may affect all requests; for example, running out of file descriptors.
FATAL: Unexpected error or assertion failure; hcproxy will abort after writing the message.

To disable all logs except FATAL (which cannot be disabled), add -DHCP_MIN_LOG_LVL=FATAL compiler flag to Makefile and recompile.

If you've installed hcproxy as systemd service, you can read logs with journalctl. Start and stop events, as well as crashes and logs, are recorded there:

journalctl -u hcproxy | tail

romkatv/hcproxy