Yubistack

This is a Golang implementation of the Yubico second factor authentication stack. Yubistack aimed to perform Yubikey (see wiki) token validation.

You can check Yubico website for information about what is a Yubikey or how to get one.

Getting started

In order to be able to develop on this project and run the various examples you need to have the following tool installed in your environment:

• git
• go toolchain, starting from version 1.11 as the project is using the newly introduced modules feature.
• make

In order to run the examples you will additionally require:

• sqlite
• curl

Due to the fact that this program manipulate sensible data (yubikeys aes key) it is highly recommended to use the samples data provided in order to avoid potential leaks.

A good way to start using this project is to run the examples from the examples directory. There is a make target make examples which will run those in proper order.

Another entrypoint would be to check the test directory, which contains programs to benchmark the yubistack authentication flow.

Build and run

You can run a simple development server by issuing the following commands:

• clone this repository: git clone gitlab.booking.com/pps/yubistack
• build the YK-Val module: make ykval
• generate a proper configuration: ./examples/ykval/run.sh --only-config
• run it with ./ykval --config=./examples/ykval/ykval.toml

Once this is running you can test if it works using this curl example: curl -k -s https://localhost:8081/wsapi/verify?otp=dteffujehknhfjbrjnlnldnhcujvddbikngjrtgh&id=1&nonce=gsgiiftz8lc8lxaa&timestamp=1&hash=4qh8RI0V2gsUSRXdBKQSmcMzivzCPJ8gc1iYdwIpx78=

# First create and populate a sqlite3 databases
cat assets/sql/sqlite/ykksm.sql examples/ykval/ykksm.sql | sqlite3 ykksm.db
cat assets/sql/sqlite/ykval.sql examples/ykval/ykval.sql | sqlite3 ykval.db
echo "UPDATE yubikeys SET modified=$(date +%s)" | sqlite3 ykval.db

# You can now start the server
go run cmd/yubistack/main.go --config examples/ykval/config.toml

# Once this is done you can try to authenticate
http -vv "http://localhost:8080/wsapi/verify?otp=dteffujehknhfjbrjnlnldnhcujvddbikngjrtgh&id=1&nonce=gsgiiftz8lc8lxaa&timestamp=1"

Modular components

Following Yubico implementation the Yubistack project is built around three components:

• ykksm: is the Yubikey Key Storage Module (YK-KSM), it holds the AES keys of the yubikeys and is responsible for the crypto part of the authentication protocol.
• ykval: is the Yubikey Validation module (YK-VAL), this module is responsible for validating tokens and handle the consensus flow.
• ykauth: is the last module responsible for authentication of the user. it supports adding a PIN in front of a token and validating it against a database, it then delegates token validation to the ykval module.

For more information about the architecture design, the protocol and how everything is plug together in Yubistack, check out the design documentation.

Background and Yubico API differences

Yubistack project was started in an attempt to bring reliability and security to our critical infrastructure. At Booking.com we are enhancing security by requiring second factor authentication. Employees can use Yubikeys to issue a token we then validate to provide access.

Yubico is already providing a reference implementation on their GitHub. However, we did not consider it suitable for various reasons: the setup was not clear, we could not easily discern how things fit together, it was not easy to integrate it within our infrastructure (metrics, logs, and packaging), the documentation was lacking, and we needed a more capable API.

You can see a more detailed description of the choices we made in the design documentation

Licence

Apache-2.0 License, see LICENSE

Acknowledgment

This software was originally developed at Booking.com. With approval from Booking.com, this software was released