Token Based Authentication

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From the course by The Hong Kong University of Science and Technology

Server-side Development with NodeJS, Express and MongoDB

242 ratings

The Hong Kong University of Science and Technology

Server-side Development with NodeJS, Express and MongoDB

242 ratings

Course 5 of 5 in the Specialization Full Stack Web and Multiplatform Mobile App Development

This course deals with all things server-side. We base the entire course around the NodeJS platform. We start with a brief overview of the Web protocols: HTTP and HTTPS. We examine NodeJS and NodeJS modules: Express for building web servers. On the database side, we review basic CRUD operations, NoSQL databases, in particular MongoDB and Mongoose for accessing MongoDB from NodeJS. We examine the REST concepts and building a RESTful API. We touch upon authentication and security. Finally we review backend as a service (BaaS) approaches, including mobile BaaS, both open-source and commercial BaaS services. At the end of this course, you will be able to: - Demonstrate an understanding of server-side concepts, CRUD and REST - Build and configure a backend server using NodeJS framework - Build a RESTful API for the front-end to access backend services

From the lesson

Halt! Who goes there?

This module is dedicated to user authentication. We first develop a full-fledged REST API server with Express, Mongo and Mongoose. Thereafter we examine basic authentication and session-based authentication briefly. We then develop token-based authentication with the support of JSON web tokens and the Passport module.

Exercise (Video): User Authentication with Passport25:20

Token Based Authentication14:41

Exercise (Video): User Authentication with Passport and JSON Web Token47:11

Meet the Instructors

Jogesh K. Muppala
Associate Professor
Department of Computer Science and Engineering

[MUSIC]

In the previous lessons,

we have seen several different kinds of authentication schemes.

We started with basic authentication, then we looked at how we can use cookies for

doing authentication, and even signed cookies, and

thereafter, we looked at session-based authentication.

Where the server is keeping track of information about each client, and

then the cookie will be used as a way of indexing into the server-side

database to extract additional information, to validate the user.

Now, the cookie and session-based authentications are not scalable,

because there server needs to keep track of all the different users.

Even though, this is done outside the HTTP protocol itself, but

still the fact that you need to keep track

of all the section information of the server site, makes it not very scalable.

So this is where token-based authentication has

proved to be very useful.

we'll look at token-base authentication a little more detailed in this lecture and

exercise that follows.

Again, quickly reviewing cookies and session based authentication.

With cookie based authentication,

we notice that cookies are stored on the client side, and the cookies are included

in every outgoing request message whereby, the server is reminded about

that specific client, by extracting information from the cookie.

Cookie can be used together with sessions, whereby the cookies store the session ID,

and then when the server receives the incoming request from the cookie,

it extracts the session ID and uses that as an index into the server-side session

store to retrieve the session information for the particular client.

Now, this approach as I said,

is not very scalable because if you have thousands of sessions, the server needs to

keep track of all these thousands of sessions on the server side.

Even though it is done independent of HTTP in a store,

either a file store or a database.

But still,

the fact that you need to track all of these information makes it not scalable.

So, again, to remind you one more time,

why do we talk about token-based authentication?

Session-based authentication, as we have seen earlier, works perfectly fine for

web applications and can easily take care of user authentication.

But then, session-based authentication, while it's the principle of

stateless servers and also leads to scalability problems.

The second issue is, mobile applications do not

handled session-based authentications very well.

Similarly, mobile applications have a hard time dealing with cookies.

So, in such circumstances where your server is serving data for

both a web application, as well as a mobile app.

Then, the session based authentication will not be very useful, and

this is where token based authentication becomes a lot more easy to use.

In a token-based authentication as the name in place,

the server will issue a token to a validated user, and all subsequent

requests coming from the client side, will bear the token in the request itself.

Either in the form of a request header or in the body of the request message.

Furthermore, token-based authentication also helps us to

deal with what are called CORS or CSRF problems.

Cross-origin resource sharing problems and so

on, I'll briefly talk about cost in the next module.

But for the moment, token-based authentication addresses some of

the issues that lies with cars and cross-site request forgery related issues.

Not only that, token-based authentication is a lot more easy for

one application to share its authentication with another application.

Of course, this is all done in a secure manner.

But, with session based authentication, that is not straight forward.

How does token-based authentication work?

In token-based authentication,

the user first needs to validate himself or herself on the server side.

Now, this validation could take on the forms that we have seen earlier.

So we can use a local validation using username and password.

Or, we can even use third party validation using

technologies like, oauth or oauth 2.0 or open ID.

We'll talk briefly about oauth and oauth 2.0 in the next module.

But, no matter which way the user authenticates, once the user

is authenticated, right after, your server can simply issue a token to the user.

And all subsequent communication between the user and

the server, can be done simply using this token.

JSON Web Token that we will talk about, is one such token-based authentication

scheme, and there server when it creates this token, it will create a signed token.

Using a secret on the server site which only the server knows.

So thereby, even if a third party in towards and between and

tries to manipulate the token, even if it captures the token and

tries to manipulate the token, the token will become invalid.

And so, that way of protecting the user is

easily feasible, all subsequent requests

from the client side should carry the token in the request,

either, as I said, in the header or in the body of the request message.

So when the server receives this token, the server will verify the token,

to ensure that this is a valid token, and then if it is a valid token,

the server will then respond to the incoming request.

As I mentioned, JSON Web Tokens is one such token-based authentication scheme.

JSON Web Token, is a very simple way of encoding

information in a token then pass it to the client site.

JSON Web Token itself is based on standards,

this is based on the IETF RFC 7519.

IETF here, stands for the Internet Engineering Task Force.

The organization that mandates everything about how the internet works,

and deals with the protocols and the policies, related to the internet.

The RFC, stands for the standards document,

in IETF terms, RFC stands for Request for Comments.

And each such standards document carries a number.

7519 in this case refers to the document,

the standard document related to JSON Web Token.

The JSON Web Token itself is a self contained token, it carries all

the information within itself, that is necessary to identify the user.

Not only that, a JSON Web Token can be shared between two applications.

So for example, one application when it authenticates and then gets hold of

a JSON Web Token, can pass that JSON Web Token to and in that application,

that it is willing to authorize to access the server on its behalf.

This sharing of the token is done in a very secure manner,

so don't worry too much about security in there.

This is not in a secure manner,

where by the sharing of the token between one application to another.

Thereby, the authorization is transferred over to a second application, and

the second application can authorize on behalf of the first application,

to communicate with the server.

This is feasible with tokens.

Now of course, the engineer in you will obviously be wondering what exactly is

inside a JSON Web Token, and how is it useful?

A JSON Web Token, as I said, is encoded into a long string and

this string itself can be interpreted as consisting of three parts.

The string itself can, or the encoded string itself contains three parts,

the Header, the Payload, and the Signature.

That carries enough information about how this token is encoded.

The Header itself contains the specific algorithm that is used for

encoding this JSON Web Token, and the type of the token itself.

The algorithm in this case, would be HS256 which is a 256 bit encoding scheme,

that is used for hashing the information inside of the token.

And in this case, this happens to be the JSON Web Token, and so

the type field will be set to JWT.

And so that is the information that is stored in the header of JSON Web Token.

The Payload itself, carries information that helps you to identify the user.

In the exercise that we will do,

the hour payload only carry the ID of the user inside the payload.

No other information is necessary.

This ID can be used on the server side,

to index into the Mongo DB to retrieve the full user information if required.

So, you will see that we'll encoding the ID and

then storing it in the payload of that message.

You can store additional information in the payload of the message if you require.

But the more information that you stored there,

the larger the corresponding JSON Web Token is going to me.

So, try to limit the amount of information that you stored in the payload

of the JSON Web Token.

As we will see in the exercise, we have a node module that enables us

to encode and create a JSON Web Token,

based on the information that we want to put in the payload.

Now, when you create a JSON Web Token, you also supply a signature.

A secret key on the server side which is used for encoding this JSON Web Token,

and that secret is also included in the signature part of the JSON Web Token.

The signature itself is included in such a way that there

is a basics before encoded header and payload,

which is then encoded using the specific secret that is used by the server.

And this encoded in, as I said the HMAC,

that we have referred to in one of the previous lessons and

using the 256 bit hashing, and that is included in the signature.

So, when this JSON Web Token is received on the server side, and

when the server decodes this token, then the server is able to cross check to

make sure that this JSON Web Token has not been tampered by anybody,

while the token is being passed between the client and the server site.

So if you know anything about security, and intruders,

and so on, you understand why it is important to encode the token, and

verify the authenticity of the token on the server site.

As I mentioned, if you need to deal with JSON Web Tokens in your node application.

There is a specific node module called as the jsonwebtoken Node Module.

This node module implements the JSON Web Token related standards, and

it can be included into your node application.

This module itself, provides a method called sign which allows you to sign and

issue the token to the client from the server side.

It also contains a verify method.

Which can be used to verify the authenticity or

to ensure the authenticity of the incoming JSON Web token,

so we will be making use of the JSON Web token module, in our exercise.

Together with the JSON Web Token module,

we also used the Passport-JWT module, node module.

Which provides the jwt based strategies for our passport authentication module.

So this provides a passport strategy for authenticating using JSON Web Token.

So this allows you to authenticate RESTful endpoint using the JWT as the method for

dong the validation, without requiring the server to use sessions.

Now, the JWT passport module,

supports a method of even extracting the JWT token from

the incoming request message, and then even verifying the token on your behalf.

The Passport-JWT module intern, uses the JSON Web Token module for

doing the verification of that JSON Web Token.

The token itself can be carried in the header of the incoming request,

in the header, even in the authentication header of the incoming request,

which is what we will be doing in the exercise.

The token can be also carried in the body of the incoming request, in which case,

we have to extract the token from the body of the incoming request and

then make use of it.

The Passport-JWT module, supports that also if you choose to

use that as way of passing the token back from the client to the server site.

The JSON Web Token, can be also included in the URL query parameters if you so

choose to, and can be extracted from there b Passport-JWT and

used for authentication.

Now, with this quick understanding of JSON Web Tokens and

how they are useful, we will move on to the exercise where we will use

the Passport-JWT module, together with the JSON Web Token module,

and configure our Express Rest API server to use JSON Web Tokens.

[MUSIC]

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