nccgroup/BinProxy

Overview

BinProxy is a proxy for arbitrary TCP connections. You can define custom message formats using the BinData gem.

Installation

Prerequisites

• Ruby 2.3 or later
• A C compiler, Ruby headers, etc., are needed to compile several dependencies.
  • On Ubuntu, sudo apt install build-essential ruby-dev should do it.
  • If you've installed a custom Ruby (e.g. with RVM), you probably already have what you need.
• openssl binary for --tls without an explicit cert/key.
• To build the UI, node.js and npm. (Not needed at runtime)

From Rubygems

gem install binproxy

You may need to use sudo, depending on your Ruby installation.

From Source

git clone https://github.com/nccgroup/BinProxy.git binproxy
cd binproxy

# Install ruby dependencies.
# Depending on your setup, one or both of these may require sudo.
gem install bundler && bundle

# The UI is built with a webpack/babel toolchain:
(cd ui && npm install) \
  && rake build-ui

# Confirm that everything works
# run.sh sets up the environment and passes all args to binproxy
./run.sh --help

To build and install the gem package:

gem build binproxy.gemspec

# Again, you may need sudo here
gem install binproxy-1.0.0.gem

Bug reports on installation issues are welcome!

Usage

Basic Usage

1. Run binproxy with no arguments.
2. Browse to http://localhost:4567/
3. Enter local and remote hostnames or IP addresses and ports, and click 'update'
4. Point a client at the local service, and watch the packets flow.

Command Line Flags

See --help for the complete list, but in short:

binproxy -c <class> [<local-host>] <local-port> <remote-host> <remote-port>

If you leave out the -c argument, a simple hex dump is shown.

If you leave out the local host, binproxy assumes localhost.

With the --socks-proxy or --http-proxy options, the remote host and port are determined dynamically, and should not be specified.

Examples

# Proxy from localhost:9000 -> example.com:9000
binproxy localhost 9000 example.com 9000

# Act as a SOCKS proxy on localhost:1080
# MITM and unwrap TLS on the proxied traffic, using a self-signed cert and key
binproxy -S --tls 1080

# "Poor substitute for Burp" mode:
#
# HTTP proxy; MITM TLS w/ pre-generated cert; simple header parsing
# Note: this will only work on HTTPS traffic, not plain HTTP!
# If you're working with the source repo, you generate the certs with:
#   rake makecert[example.com]
# And then import certs/ca-cert.pem into your browser or OS's trust store.
binproxy -H --tls \
  --tls-cert certs/example.com-cert.pem \
  --tls-key certs/example.com-key.pem \
  --class-name DumbHttp::Message \
  localhost 8080

Customizing

By default, the proxy uses the built-in RawMessage class, which just gives you a hexdump of each message (assuming 1:1 between messages and TCP packets)

You can view parsed protocol information by specifying a BinData::Record subclass† with the --class command line argument.

You may also wish to define the following in your class:

def summary
  # return a single-line description of this record
end

# currently supported options are
#   - nil : use default display
#   - "anon" : for structs, show contents directly
#   - "hex" : for numbers, display as 0x1234ABCD
#   - "hexdump" : for strings, display like `hexdump -C`
default_parameter display_as: "..."

# TODO: document state stuff
def self.initial_state
end

def current_state
end

def update_state
end

† Technically, any subclass of BinData::Base will work.

Dynamic Proxying

By default, BinProxy relays all traffic to a static upstream host and port. It can also be configured to act as a SOCKS (v4 or v4a) or HTTP proxy with the --socks-proxy and --http-proxy flags, respectively.

Note: Currently, the HTTP proxy only supports connections tunneled with the HTTP CONNNECT verb; it cannot proxy raw HTTP GET, POST, etc., requests. In practice, this means that HTTPS traffic will work, but plain HTTP traffic will not unless the client supports a flag to force tunneling, like curl -p.

TLS / SSL

Use the --tls flag to unwrap TLS encryption before processing messages. By default, BinProxy will generate a self-signed certificate. You can sepecify PEM files containing a certificate and key with --tls-cert and --tls-key. (If you've cloned the source repo, use rake makecert[example.com] to generate a static CA and a certificate with the appropriate hostname.)

Known issues

• The HTTP proxy functionality was thrown together at the last minute and is not particularly robust.

See also the TODO file for random ideas and wishlist items.

Credits

BinProxy's core TCP proxy functionality originated in a special purpose proxy written by Sean Devlin. Rusty Burchfield contributed the HTML UI for that proxy. While enough of the code has changed that they can no longer be blamed for any current bugs, BinProxy likely wouldn't exist without both of their work.