Yubico U2F Validation Server

This project is no longer actively maintained.

The Yubico U2F Validation Server (u2fval) is a server that provides U2F registration and authentication through a simple JSON based REST API.


u2flib-server is installable by one of three means

  1. via pip

  2. via git

  3. via python setup.py

Installation via pip


pip install u2fval

Alternatively, you can run:

pip install u2fval-<version>.tar.gz

Where the .tar.gz file is a source release of the project.

Installation via git

  • Run these commands to check out the source code:

    git clone https://github.com/Yubico/u2fval.git
    cd u2fval
    git submodule init
    git submodule update
  • Build a source release tar ball by running:

    python setup.py sdist

The resulting build will be created in the dist/ subdirectory.

Installation via python setup.py

You can install directly from the git checkout by running the following commands:

python setup.py install


Configuration is kept in /etc/yubico/u2fval/u2fval.conf, see the default configuration file for more information (also available in the conf/ directory of any source release of this project).

The Yubico U2F Validation Server needs an SQL database to work. Optionally a memcached server can be used to store transient data which doesn’t need to be persisted to the database (if not available this data will be stored in the main database). The default configuration uses an in-memory SQLite3 database which you probably want to change to something like

SQLALCHEMY_DATABASE_URI = 'sqlite:////etc/yubico/u2fval/u2fval.db'

Once the configuration file has been configured with database credentials, the database can be initialized by running the following command:

u2fval db init

API Clients

To be able to use the server, a client needs to be created. This is done using the u2fval client create command. For example:

u2fval client create example \
  https://example.com/app-identity.json \

See u2fval client create --help for more information.

Authenticating Clients

Each client request needs to be authenticated. This authentication is outside of the scope of the Yubico U2F Validation Server and can be handled by the webserver or some WSGI middleware. Once authenticated, the client name should be set in the REMOTE_USER server environment variable.


The server can either be run standalone (intended for testing purposes) using the u2fval run command, or be hosted by any WSGI capable web server, such as Apache with mod_wsgi enabled.

Accessing the Server

Once the server is set up and at least one client has been created, the client can access the server via the REST API. Find the API documentation in the doc/ directory.