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Wednesday, February 16, 2011

Authentication in Mongo and Mongoid

Mongo has primitive authentication - just basic user/password authentication per database.

It's preferred mode of operation is no authentication in a trusted environment. That's fine, but it's not always possible. I want to run mongo on a Amazon EC2 node and access it from remote clients so I need to use authentication. On top of that, I already have the database running without authentication on a node.

Here are the steps you need to make the migration to a server with authentication...

1. Create an admin user on the database
Open up a mongo shell on the machine running the server
$ mongo
> use admin
> db.addUser("your_admin_user", "your_password")
> exit


2. Restart your Mongo server with --auth
It is CRITICAL that you restart with the --auth option. Users and passwords are simply ignored without this option.
$ mongod --auth


3. Set up database specific users
$ mongo
> use admin
> db.auth("your_admin_user", "your_password")
> show dbs
> use your_db
> db.addUser("your_db_user", "your_password")
> db.system.users.find()
> exit


4. Set up authenticated access from your application
I work in Ruby and use Mongoid as the Object Document Mapper to access Mongo. Mongoid, in turn uses the Ruby Mongo Driver. If you are using Mongoid outside of Rails then you will need a configuration block along the lines of this;

Mongoid.configure do |config|
name = "your_db"
config.database = Mongo::Connection.new.db(name)
config.database.authenticate("your_db_user", "your_password")
end

Note that you are authenticating with the Ruby Mongo driver - not with Mongoid.

If you are working with Rails then you'll need to add username and password into your config/database.yml file. I see that the Devise authentication gem can work with Mongo to handle authentication of individual users but I've not explored that yet.

5. Clearly there is an issue having your password in plain text in your code
The bottom line is that you probably don't want to trust Mongo authentication for critical data. In that case, you really need to set up Mongo access in a secure environment and perhaps handle interfacing this with the outside work through a separate gateway application, say a Sinatra app that handles all authentication itself.

For my needs I have non-critical data - I just want to prevent access to arbitrary users (i.e. port scanning scripts) and only access from a few defined scripts on specific machines. So for now this will work for me.

With mongo authentication in place, how do you handle backing up and restoring the database?

On the machine hosting the server you can use these two variants of the dump and restore commands:
$ mongodump -d your_db -o . -u your_db_user -p your_password
[...]
$ mongorestore -u your_db_user -p your_password your_db


To work with all databases you would use the admin user

In order for someone to break into your database someone has to
1: Guess/crack your admin username and password
or
2: Guess/crack your specific database, your db username and password.

You have to evaluate the chances of this along with the value of the data in the database before going down this path.
You can also configure the database to use a non-standard port. There is no harm in this but it offers minimal to no additional security as many malicious scripts will scan across all ports on a machine looking for one that responds.

Caveat emptor...


 

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