RDS Factor

Two-factor authentication for Remote Desktop Services (RDS).

RDS Factor consist of two components:

• A server component that talks RADIUS with RD Web and the RD Gateway.
• An updated version of the RD Web pages that interacts with the RADIUS server and an opt-in multi-factor form.

RDS Factor works by sending an SMS to the user after they've authenticated with their user name and password. The SMS contains a key which when entered, allow them entrance to RD Web. Clicking on an application in RD Web opens a window in the gateway for that user. In that way, users that are not authenticated via RD Web cannot access the RD Gateway. Compare this to the standard RDS setup, where there is no way to share state between RD Web and RD Gateway, meaning that the gateway is always open for logging in with credentials.

You can also disable two-factor authentication in RDS Factor. In this case, RDS Factor maintains state between RD Web and RD Gateway, ensuring that users must have logged into RD Web before connections are allowed through the gateway. This allows custom multi-factor authenticators in front of RD Web to also protect the gateway.

Tested on Windows 2012 R2.

Prerequisites

An RDS setup. There are many options for orchestrating the RDS setup; the minimal RDS setup for use with RDS Factor consist of two servers:

• Active Directory; and
• RDS with Gateway component enabled

Use 'Active Directory Users and Computers' to add a mobile number to relevant LDAP users in the Active Directory. The tool is not installed per default; you can find it in Add Roles -> Features -> Remote Server Administration Tools -> AD DS Tools -> AD DS Snap-Ins And Command-Line Tools

Installation

Grap the latest rdsfactor.zip release from github. And unzip it.

RD Web update

RDS factor comes with a customized version of the RD Web pages. To install these run:

C:\RDSFactor> install-web.bat

After install go and configure the application in IIS. RDWeb -> Pages -> Application Settings. You should configure the following settings:

• RadiusSecret Shared secret — of your own chosing — used for encrypting RADIUS traffic
• RadiusServer IP of the radius server

RADIUS server installation

The RADIUS server component can be installed on any server reacheable by both the RD Web and the RD Gateway. To install the server as a service run:

C:\RDSFactor> install-server.bat

After install go and configure the server. Open the file RDSFactor/server/bin/release/conf.ini for editing. You should configure the following settings:

• LDAPDomain IP of LDAP server to authenticate user and lookup phonenumber against
• ADField LDAP attribute to use for looking up the user's phonenumber
• EnableOTP Boolean (0|1) that indicates whether to use the 2. factor for auth
• Debug Enable debug output to RDSFactor/server/bin/release/log.txt
• {client}={shared secret} IP of RD Web and shared secret — same as RadiusSecret — for encryption
• Provider URL of SMS provider. RDS Factor inserts the number and a message in the two variable, ***NUMBER*** and ***TEXTMESSAGE***, in the provider URL. An example URL using the SMS gateway cpsms: https://www.cpsms.dk/sms/?username=myuser&password=mypassword&recipient=NUMBER&message=TEXTMESSAGE&from=CPSMS

To reload the configuration restart the RADIUS server service by running

C:\RDSFactor> restart-server.bat

Configure RD Gateway

The gateway must be configured to talk to the RADIUS RDSFactor server. Open up the 'Remote Desktop Manager' and Right Click on RDS -> Properties -> RD CAP Store.

Here you must:

• Check 'Request clients to send statement of health'
• Check 'Central Server running NPS'
• Enter the name or IP of the server running the RDSFactor server and add the shared secret

Logging

Log output from the RADAR client in RD Web is output into:

C:\RDSFactor\web\RDWeb\Pages\log> radius_client.txt

Log output from the RADAR server:

C:\RDSFactor\server\bin\Release> log.txt

Hacking on RDS Factor

The core RADIUS server is included in this project as a git submodule. Fetch it by:

C:\RDSFactor> git submodule update --init

Open the RDSFactorWeb project in Visual Studio.

Acknowledgements

• Claus Isager — for the first open source two-factor RDS authenticator, the basis for this project.
• Nikolay Semov — for the core RADIUS server

License

RDS Factor is an open source project, sponsored by Origo Systems A/S, and released under terms of the GNU General Public License, version 3.