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couch_jwt_auth

couch_jwt_auth is authentication plugin for CouchDB. It accepts JSON Web Token in the Authorization HTTP header and creates CouchDB user context from the token information. couch_jwt_auth doesn't use CouchDB authentication database. User roles are read directly from JWT and not from the authentication database.

The plugin doesn't support unsecured JWTs or digital signature algorithms. Only hash-based message authentication codes are supported. I might add support for digital signature algorithms later.

If you want to learn more around JWT itself, the intro on their site is just amazing and explains the concepts really well.

Installation

  1. Install rebar if you don't already have it, which is used to compile the Erlang project.
$ brew install rebar
  1. Clone (download) the repo:
$ git clone https://github.com/softapalvelin/couch_jwt_auth.git
  1. Build the plugin files:
$ cd couch_jwt_auth $ ./build.sh $ make plugin
  1. Find where CouchDB is installed:
$ brew info couchdb | grep Cellar

It should ouput something like: /usr/local/Cellar/couchdb/1.6.1_3 (657 files, 17M) *, a path like the one at the beginning (/usr/local/Cellar/couchdb/1.6.1_3) is what you're after :). That's CouchDB's root in your Mac. Use whatever your local path is in the following commands:

  1. Ensure the plugins directory exists:
$ mkdir -p /usr/local/Cellar/couchdb/1.6.1_3/lib/couchdb/plugins
  1. Move the plugin to CouchDB's plugins folder:
$ mv couch_jwt_auth-1.0.1-18-1.6.1 /usr/local/Cellar/couchdb/1.6.1_3/lib/couchdb/plugins/couch_jwt_auth
  1. Configure the couch_jwt_auth:

Copy the default config file to CouchDB's etc folder:

$ cp /usr/local/Cellar/couchdb/1.6.1_3/lib/couchdb/plugins/couch_jwt_auth/priv/default.d/jwt_auth.ini /usr/local/etc/couchdb/default.d

Edit /usr/local/etc/couchdb/default.d/jwt_auth.ini and at least change the hs_secret value. This is your JWT shared secret that you will use somewhere else to authenticate with. This value has to be encoded in base64. openssl can help us with that. Choose a secret like supersecret :) and run this:

echo -n 'supersecret' | openssl base64

It will output a base64 string like c3VwZXJzZWNyZXQ=, put that in like:

hs_secret = c3VwZXJzZWNyZXQ=

Here's a nice command to get a random secret:

openssl rand -base64 32 | tr -d /=+ | cut -c -30

If you're using couchdb-jwt-auth-server to leverage authentication through the _users db (see below), make sure that you set username_claim to this:

username_claim=name

This means that instead of using sub as the username_claim, it uses name which is the field that CouchDB uses in its _users database to tell users apart. This wiki page contains more information about configuration options.

Edit /usr/local/etc/couchdb/local.ini and add couch_jwt_auth to CouchDB's authentication_handlers httpd section. It's ok to have more options on that line :):

[httpd]
authentication_handlers = ..., {couch_jwt_auth, jwt_authentication_handler}, ...
  1. Restart couchdb and you're good to go.

Note that you can copy the same compiled plugin to your production instance of CouchDB. In my Ubuntu deployment of CouchDB, the plugins live at /usr/lib/x86_64-linux-gnu/couchdb/plugins. So the steps are the same apart from the fact that you may need to push the built file somehow.

Alternatively, you can try to push it through CouchDB's HTTP API but it doesn't seem to work at all times. See this post for more on how to go about it.

Test with Curl

$ curl http://127.0.0.1:5984/_session

You should see jwt in the authentication_handlers. Next you can test sending JWT with the request. HMAC secret for this test is secret so the Base64URL encoded secret is c2VjcmV0.

Now you can generate a sample JWT from http://jwt.io. The token is included in the Authorization HTTP header like this:

$ curl -H "Authorization: Bearer TOKEN_HERE" http://127.0.0.1:5984/_session

With default options you should see the JWT "sub" claim content in the CouchDB username:

$ curl -H "Authorization: Bearer
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgQ"
http://127.0.0.1:5984/_session

will output:

$ {"ok":true,"userCtx":{"name":"1234567890","roles":[]},"info":{"authentication_db":"_users","authentication_handlers":[...,"jwt",...],"authenticated":"jwt"}}

Use cases

Auth0 is an identity service that supports many identity providers like Google, Facebook, Twitter and so on. Auth0 generates a JWT that can be parsed by this plugin. Here is a sample application that uses Auth0 to authenticate a user with CouchDB.

If you want to leverage CouchDB's _users database as your authentication mechanism you still can! Have a look at couchdb-jwt-auth-server for a NodeJS implementation that allows you to generate JWT tokens that this plugin can consume.

The motivation section in couchdb-jtw-auth-server explains very well how and why you would want to use this approach over cookies.

Apache v2.0 license.