Px is a HTTP(s) proxy server that allows applications to authenticate through
an NTLM proxy server, typically used in corporate deployments, without having
to deal with the actual NTLM handshake. It is primarily designed to run on
Windows systems and authenticates on behalf of the application using the
currently logged in Windows user account.

Px is very similar to "NTLM Authorization Proxy Server" (http://ntlmaps.sourceforge.net/)
and Cntlm (http://cntlm.sourceforge.net/) in that it sits between the corporate
proxy and applications and offloads the NTLM authentication. The primary
difference in Px is to use the currently logged in user's credentials to log in
automatically rather than requiring the user to provide the username, password
(hash) and domain information. This is accomplished by using Microsoft SSPI to
generate the tokens and signatures required to authenticate with the NTLM proxy.

NTLMAps and Cntlm were designed for non-Windows users stuck behind a corporate
proxy.  As a result, they require the user to provide the correct credentials
to authenticate. On Windows, the user has already logged in with his credentials
so Px is designed for Windows users who would like to use tools that aren't
designed to deal with NTLM authentication, without having to supply and maintain
the credentials within Px.

The following link from Microsoft provides a good starting point to understand
how NTLM authentication works:

  https://msdn.microsoft.com/en-us/library/dd925287.aspx

Installation

Px can be obtained in multiple ways:-

- Download the latest binary ZIP from the releases page:
    https://github.com/genotrance/px/releases

- Download a source ZIP of the latest release from above link.

- Clone the latest source:
    git clone https://github.com/genotrance/px

- Download the latest source ZIP:
    https://github.com/genotrance/px/archive/master.zip

Running the source directly requires Python and all dependencies installed.

Once downloaded, extract to a folder of choice and use the --save and --install
commands as documented below.

Configuration

Px requires only one piece of information in order to function - the server
name and port of the NTLM proxy server. This needs to be configured in px.ini.
If not specified, Px will check Internet Options for any proxy definitions and
use them. Without this, Px will not work and exit immediately.

The noproxy capability allows Px to connect to hosts in the configured subnets
directly, bypassing the NTLM proxy altogether. This allows clients to connect
to hosts within the intranet without requiring additional configuration for
each client or at the NTLM proxy. If noproxy is defined, the NTLM proxy is
optional - this allows Px to run as a regular proxy full time if required.

There are a few other settings to tweak in the INI file but most are obvious.
All settings can be specified on the command line for convenience. The INI file
can also be created or updated from the command line using --save.

The binary distribution of Px runs in the background once started and can be
quit by running "px --quit". When run directly using Python, use CTRL-C to quit.

Px can also be setup to automatically run on startup with the --install flag.
This is done by adding an entry into the Window registry which can be removed
with --uninstall.

Usage

px [FLAGS]
python px.py [FLAGS]

Actions:
  --save
  Save configuration to px.ini or file specified with --config
    Allows setting up Px config directly from command line
    Values specified on CLI override any values in existing config file
    Values not specified on CLI or config file are set to defaults

  --install
  Add Px to the Windows registry to run on startup

  --uninstall
  Remove Px from the Windows registry

  --quit
  Quit a running instance of Px.exe

Configuration:
  --config=
  Specify config file. Valid file path, default: px.ini in working directory

  --proxy=  --server=  proxy:server= in INI file
  NTLM server(s) to connect through. IP:port, hostname:port
    Multiple proxies can be specified comma separated. Px will iterate through
    and use the one that works. Required field unless --noproxy is defined. If
    remote server is not in noproxy list and proxy is undefined, Px will reject
    the request

  --listen=  proxy:listen=
  IP interface to listen on. Valid IP address, default: 127.0.0.1

  --port=  proxy:port=
  Port to run this proxy. Valid port number, default: 3128

  --gateway  proxy:gateway=
  Allow remote machines to use proxy. 0 or 1, default: 0
    Overrides 'listen' and binds to all interfaces

  --hostonly  proxy:hostonly=
  Allow only local interfaces to use proxy. 0 or 1, default: 0
    Px allows all IP addresses assigned to local interfaces to use the service.
    This allows local apps as well as VM or container apps to use Px when in a
    NAT config. Px does this by listening on all interfaces and overriding the
    allow list.

  --allow=  proxy:allow=
  Allow connection from specific subnets. Comma separated, default: *.*.*.*
    Whitelist which IPs can use the proxy. --hostonly overrides any definitions
    unless --gateway mode is also specified
    127.0.0.1 - specific ip
    192.168.0.* - wildcards
    192.168.0.1-192.168.0.255 - ranges
    192.168.0.1/24 - CIDR

  --noproxy=  proxy:noproxy=
  Direct connect to specific subnets like a regular proxy. Comma separated
    Skip the NTLM proxy for connections to these subnets
    127.0.0.1 - specific ip
    192.168.0.* - wildcards
    192.168.0.1-192.168.0.255 - ranges
    192.168.0.1/24 - CIDR

  --useragent=  proxy:useragent=
  Override or send User-Agent header on client's behalf

  --workers=  settings:workers=
  Number of parallel workers (processes). Valid integer, default: 2

  --threads=  settings:threads=
  Number of parallel threads per worker (process). Valid integer, default: 5

  --idle=  settings:idle=
  Idle timeout in seconds for HTTP connect sessions. Valid integer, default: 30

  --socktimeout=  settings:socktimeout=
  Timeout in seconds for connections before giving up. Valid float, default: 5

  --proxyreload=  settings:proxyreload=
  Time interval in seconds before reloading proxy info. Valid int, default: 60
    Proxy info is reloaded from a PAC file found via WPAD or AutoConfig URL, or
    manual proxy info defined in Internet Options

  --foreground  settings:foreground=
  Run in foreground when frozen or with pythonw.exe. 0 or 1, default: 0
    Px will attach to the console and write to it even though the prompt is
    available for further commands. CTRL-C in the console will exit Px

  --debug  settings:log=
  Enable debug logging. default: 0
    Logs are written to working directory and over-written on startup
    A log is automatically created if Px crashes for some reason

Examples

  Use proxyserver.com:80 and allow requests from localhost only
  px --proxy=proxyserver.com:80

  Don't use any forward proxy at all, just log what's going on
  px --noproxy=0.0.0.0/0 --debug

  Allow requests from localhost and all locally assigned IP addresses. This is
  very useful for Docker for Windows and VMs in a NAT configuration because all
  requests originate from the host's IP
  px --proxy=proxyserver.com:80 --hostonly

  Allow requests from localhost, locally assigned IP addresses and the IPs
  specified in the allow list outside the host
  px --proxy=proxyserver:80 --hostonly --gateway --allow=172.*.*.*

  Allow requests from everywhere. Be careful, every client will use your login
  px --proxy=proxyserver.com:80 --gateway

NOTE:
  In Docker for Windows you need to set your proxy to http://<your ip>:3128 (oractual port
  Px is listening to) and be aware of docker/for-win#1380.

  Workaround: docker build --build-arg http_proxy=http://<your ip>:3128 --build-arg
              https_proxy=http://<your ip>:3128 -t containername ../dir/with/Dockerfile

Dependencies

Px doesn't have any GUI and runs completely in the background. It is distributed
using Python 3.x and PyInstaller to have a self-contained executable but can
also be run using a Python distribution with the following additional packages.

  netaddr, psutil, pypac, winkerberos
  futures on Python 2.x

In order to make Px a capable proxy server, it is designed to run in multiple
processes. The number of parallel workers or processes is configurable. However,
this only works on Python 3.3+ since that's when support was added to share
sockets across processes in Windows. On older versions of Python, Px will run
multi-threaded but in a single process. The number of threads per process is
also configurable.

Feedback

Px is definitely a work in progress and any feedback or suggestions are welcome.
It is hosted on GitHub (https://github.com/genotrance/px) with an MIT license
so issues, forks and PRs are most appreciated.

Credits

Px is based on code from all over the internet and especially acknowledges these sources:-

http://stackoverflow.com/questions/2969481/ntlm-authentication-in-python
http://www.oki-osk.jp/esc/python/proxy/
http://stupidpythonideas.blogspot.com/2014/09/sockets-and-multiprocessing.html
https://curl.haxx.se/mail/lib-2014-09/0070.html
https://github.com/fl4re/curl/blob/master/lib/curl_sasl_sspi.c
mongodb/winkerberos#19
https://www.tillett.info/2013/05/13/how-to-create-a-windows-program-that-works-as-both-as-a-gui-and-console-application/
http://www.boku.ru/2016/02/28/posting-to-console-from-gui-app/

Thank you to the following contributors as well for their PRs:-

https://github.com/ccbur
https://github.com/McBane87