tlsauth 0.4-1
Implements TLS Authentication - simple client certificate CA inclusive
License: BSD
Keywords: crypto authentication TLS certificate x509 CA

* tlsauth

This is a simple example how to setup TLS Certificate Authentication
for your online services. The example is based on nginx and WSGI but
should work also with an FCGI backend with PHP.

Using tlsauth you can authenticate your users based on certificates
instead of passwords. In fact you don't have to store neither the
usernames, their email addresses nor their nicks, it is all contained
in the Client certificate that is stored and presented by the
user. You can be sure, unless your signing key is compromised, noone
else can create valid certificates but you. This eliminates the need
to remember passwords and prohibits password bruteforcing. Using
nginx, you can even display totally different content depending if an
request is authenticated or not, routing unauthenticated users to
static html for example while authenticated users having access to
some dynamic content.

I don't want to scare you but this is essentially a self-signed CA, it
provides all the neccessary basic tools to make this hassle-free. Your
users only need to go through a registration procedure and then they
could enjoy seamless single-sign-on to all your services, never being
asked for a password again.

** CA and https service install
*** create a "localhost CA" in ./root-ca
    #+BEGIN_SRC sh
./tlsauth.py root-ca createca http://localhost/crl.pem "Example CA" ca@example.com
    #+END_SRC
*** create a "client authentication CA" in ./sub-ca
    #+BEGIN_SRC sh
./tlsauth.py sub-ca createca http://localhost/client-crl.pem "hostname client CA" email@example.com root-ca
    #+END_SRC
*** create https server certificate
    #+BEGIN_SRC sh
./tlsauth.py root-ca newcsr localhost root@localhost >server.key
    #+END_SRC
*** Sign server cert with CA
    #+BEGIN_SRC sh
./tlsauth.py sign <server.key >server.pem
    #+END_SRC
*** Remove Root CA private key
It is important to remove and store the root CA private key in a safe
offline location, as it can be used to mount a MITM attack against all
users, who trust this key. You need this key in 1 year, when you need
to renew your client CA certificate (per default it's only valid for
one year!)
    #+BEGIN_SRC sh
mv root-ca/private/root.key <private and save location>
    #+END_SRC
*** Setup nginx to serve
    #+BEGIN_SRC sh
server {
    listen        443;
    ssl on;
    server_name localhost;

    ssl_certificate      <pathto>/tlsauth/server.cert;
    ssl_certificate_key  <pathto>/tlsauth/server.key;
    ssl_client_certificate <pathto>/tlsauth/sub-ca/public/root.pem;
    ssl_verify_client optional;

    location / {
       include uwsgi_params;
       uwsgi_param verified $ssl_client_verify;
       uwsgi_param dn $ssl_client_s_dn;
       if ( $ssl_client_verify = "SUCCESS") {
          uwsgi_pass 127.0.0.1:8080;
       }
       try_files $uri $uri/ /index.html;
    }
}
#+END_SRC
  don't forget to restart nginx.

  Now if users have a proper client cert installed the environment of
  the WSGI application will contain the variables 'verified' and 'dn'
  variables set accordingly.
** webserver Demo
  There's a bundled demo, to try it out:
*** set up uwsgi
    #+BEGIN_SRC sh
edit flask-demo/tlsdemo_wsgi.py
    #+END_SRC
*** install python dependencies
    #+BEGIN_SRC sh
virtualenv --distribute env
source env/bin/activate
pip install Flask uwsgi
    #+END_SRC
*** run flask application
    #+BEGIN_SRC sh
basedir=$PWD
env/bin/uwsgi --socket 127.0.0.1:8080 --chdir $basedir/flask-demo -pp $basedir -w tlsdemo_wsgi -p 1 --virtualenv $basedir/env
    #+END_SRC
** Client side setup
How to create a proper Client certificate.
*** Create a client certificate
   #+BEGIN_SRC sh
./tlsauth.py root-ca newcsr joe joe@localhost >joe.key
   #+END_SRC
   send the resulting "user.csr" to the CA for signing. In this case
   you are both, but in a normal case this step is done by arbitrary
   users who send this csr file during the registration process to the
   site.

   Store user.key away somewhere safe offline, you'll need it later
   once more.
*** CA signs users cert signing request
   #+BEGIN_SRC sh
./tlsauth.py root-ca sign <joe.key >joe.cert
   #+END_SRC
   CA sends back the signed 'user.cert" to the sender. As a
   convenience feature also the root CA cert should be sent to the
   user, so he can import this also in his CA store.
*** Create PKCS#12 cert for your browser
   Using the returned cert from the CA we convert it together with the
   secret key part to a PKCS#12
   #+BEGIN_SRC sh
./tlsauth.py root-ca p12 joe.key <joe.cert >joe.p12
   #+END_SRC
   This asks for a passphrase which is needed only once when importing
   into the browser.
*** Import the certificates in Firefox
  1. Using the menu open the Preferences dialog.
  2. Select the Advanced toolbar icon
  3. click on the "View certificates" button
  4. On the "Authorities" tab click on the Import button and import
     the root CA cert (this must be supplied by the CA to you).
  5. on the "Your Certificates" tab click on the "Import" button and
     load the file "user.cert.p12"

  if everything went ok the new certificate should appear under the
  "Your Certificates" tab
*** Securing keys
    Store away private key in joe.key again together with the pkcs12
    cert joe.p12 in a safe offline location (maybe your backup?), if
    you reinstall your browser you want to import user.cert.p12 back
    into it again.

    If you now surf to https://localhost with this firefox, the flask
    application should report back your distinguished name. If you
    browse to this location with another browser which lacks this
    certificate you will probably see the default nginx installation
    html page.
** Python usage
   see test.py
** Changes
*** v0.4
    Fixed dangerously exposed Root CA key, by introducing a sub CA
    only for signing the client authentication keys, and thus
    eliminating the chance for a MITM attack in case the Root CA gets
    compromised.