== u2flib-server
Provides functionality for working with the server side aspects of the U2F
protocol as defined in the link:http://fidoalliance.org/specifications/download[FIDO specifications].
It supports Python 2.7, Python 3.3+ and PyPy 2.7+.

To read more about U2F and how to use a U2F library, visit
link:http://developers.yubico.com/U2F[developers.yubico.com/U2F].

=== Dependencies
u2flib-server depends on link:https://pypi.python.org/pypi/cryptography[cryptography],
which requires libffi, OpenSSL, and a C compiler to build.
On a Debian or Ubuntu system, the build dependencies can be installed with
the following command: 

  $ sudo apt-get install build-essential libssl-dev libffi-dev python-dev

For Windows the cryptography project provides prebuilt wheels.
For other platforms refer to link:https://cryptography.io/en/stable/installation/[cryptography installation].

=== Installation
u2flib-server is installable by running the following command:

  $ pip install python-u2flib-server

==== Check out the code
Run these commands to check out the source code:

  git clone https://github.com/Yubico/python-u2flib-server.git
  cd python-u2flib-server
  git submodule init
  git submodule update

==== Build a source release
To build a source release tar ball, run this command:

  python setup.py sdist

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

=== Example
See `examples/u2f_server.py` for a working example of a HTTP server for
U2F enrollment and authentication. `u2f_server.py` can be run as a stand-alone
server, and can be used to test a U2F client implementation, such as
python-u2flib-host, using for example cURL.

The examples below show cURL command to register a U2F device, and to
authenticate it.

==== Registration
Registration is initiated by sending a request to the server:

----
$ curl http://localhost:8081/enroll
{"appId": "http://localhost:8081", "registeredKeys": [], "registerRequests": [{"version": "U2F_V2", "challenge": "9TCtiRRLBFqMokOWfepjej99lMKQhZfm20Sgtay-FMs"}]}
----
The RegisterRequest data is then fed to the U2F client, resulting in the
RegisterResponse data, which is passed back to the server:
----
$ curl http://localhost:8081/bind -d'data={"registrationData": " ", "clientData": "eyJvcmlnaW4iOiAiaHR0cDovL2xvY2FsaG9zdDo4MDgxIiwgImNoYWxsZW5nZSI6ICI5VEN0aVJSTEJGcU1va09XZmVwamVqOTlsTUtRaFpmbTIwU2d0YXktRk1zIiwgInR5cCI6ICJuYXZpZ2F0b3IuaWQuZmluaXNoRW5yb2xsbWVudCJ9","version":"U2F_V2"}'
true
----
The result, "true", indicates that registration was successful.

==== Authentication
Authentication for a previously registered U2F device is done by sending a
request to the server:

----
$ curl http://localhost:8081/sign
{"appId": "http://localhost:8081", "registeredKeys": [{"version": "U2F_V2", "appId": "http://localhost:8081", "keyHandle": "slre1LIz6KuBkc1fCwcL5id-lcn-5CREyyDHfugB58ckjdGwF7jII3aehr6M7WaC2BGs8rjTlB1ykjvFWTdeYA"}], "challenge": "FnueX-NpT9kB7I41dc8DvPXU1-yj7oO_cBT3e9PWOAw"}
----
The AuthenticateRequest data is then fed to the U2F client, resulting in an
AuthenticateResponse object which is passed back to the server:
----
$ curl http://localhost:8081/verify -d'data={"keyHandle": "slre1LIz6KuBkc1fCwcL5id-lcn-5CREyyDHfugB58ckjdGwF7jII3aehr6M7WaC2BGs8rjTlB1ykjvFWTdeYA", "signatureData": "AQAAAAEwRgIhALhe7LTwnBHTPQQIGbn_wPR80S7-HPPliZh966vL3VeiAiEA35w-BVDROwdLGlztLgejw9bnXSrYY0-3EC-_qhi0XaI", "clientData": "eyJvcmlnaW4iOiAiaHR0cDovL2xvY2FsaG9zdDo4MDgxIiwgImNoYWxsZW5nZSI6ICJGbnVlWC1OcFQ5a0I3STQxZGM4RHZQWFUxLXlqN29PX2NCVDNlOVBXT0F3IiwgInR5cCI6ICJuYXZpZ2F0b3IuaWQuZ2V0QXNzZXJ0aW9uIn0"}'
{"touch": 1, "counter": 1}
----
The response indicates success, giving the U2F devices internal counter value,
as well as the value of the user presence parameter.
