I am developing a Demo WebApp using the MERN stack and using JWT for Authentication.
In the Backend, when a user requests to log in, I am preparing a JWT token by adding the MongoDB ObjectID for that user in the token's payload with necessary timestamps.
On User login, I want to store the User details for that session on Frontend.
I know that I can share all those details via API response & store it using React Context/ Redux. But is it a good practice to create a JWT token from the backend with all the session-specific User details stored on DB (Apart from secure information) into Payload during login & sending the encrypted token in the response? So that, I can decrypt & destructure the user details from the JWT token and store them for that session.
Eager to know the Pros and Cons of the above process keeping best coding practices into consideration.
It seems like you need something like an ID token from OpenID Connect (https://openid.net/). This is a JWT which contains user data used on the frontend to identify user, maybe print their username somewhere, etc. It is a common practice to use it, but you should remember that if you put too much information into that token it will get quite large (which can have an impact on slower connections, or slower computers which will need to decode it, verify signatures, etc.)
Another viable option is to have an endpoint which returns all that information when needed (see the userinfo endpoint in OIDC).
You also have to remember that all that information will be readable to anyone who has access to that JWT, so no personal information should be kept there.
Just a note - I can decrypt & destructure the user details from the JWT token - you probably mean decode here. Decoding is the act of changing the JWT from a base64 encoded string into a JSON object. You can have truly encrypted JWTs (JWE), which guards them from being read by eavesdroppers, but you wouldn't use them in a frontend app. They are also much more complicated to set up and use more CPU.
If I get a JWT and I can decode the payload, how is that secure? Couldn't I just grab the token out of the header, decode and change the user information in the payload, and send it back with the same correct encoded secret?
I know they must be secure, but I just would really like to understand the technologies. What am I missing?
JWTs can be either signed, encrypted or both. If a token is signed, but not encrypted, everyone can read its contents, but when you don't know the private key, you can't change it. Otherwise, the receiver will notice that the signature won't match anymore.
Answer to your comment: I'm not sure if I understand your comment the right way. Just to be sure: do you know and understand digital signatures? I'll just briefly explain one variant (HMAC, which is symmetrical, but there are many others).
Let's assume Alice wants to send a JWT to Bob. They both know some shared secret. Mallory doesn't know that secret, but wants to interfere and change the JWT. To prevent that, Alice calculates Hash(payload + secret) and appends this as signature.
When receiving the message, Bob can also calculate Hash(payload + secret) to check whether the signature matches.
If however, Mallory changes something in the content, she isn't able to calculate the matching signature (which would be Hash(newContent + secret)). She doesn't know the secret and has no way of finding it out.
This means if she changes something, the signature won't match anymore, and Bob will simply not accept the JWT anymore.
Let's suppose, I send another person the message {"id":1} and sign it with Hash(content + secret). (+ is just concatenation here). I use the SHA256 Hash function, and the signature I get is: 330e7b0775561c6e95797d4dd306a150046e239986f0a1373230fda0235bda8c. Now it's your turn: play the role of Mallory and try to sign the message {"id":2}. You can't because you don't know which secret I used. If I suppose that the recipient knows the secret, he CAN calculate the signature of any message and check if it's correct.
You can go to jwt.io, paste your token and read the contents. This is jarring for a lot of people initially.
The short answer is that JWT doesn't concern itself with encryption. It cares about validation. That is to say, it can always get the answer for "Have the contents of this token been manipulated"? This means user manipulation of the JWT token is futile because the server will know and disregard the token. The server adds a signature based on the payload when issuing a token to the client. Later on it verifies the payload and matching signature.
The logical question is what is the motivation for not concerning itself with encrypted contents?
The simplest reason is because it assumes this is a solved problem for the most part. If dealing with a client like the web browser for example, you can store the JWT tokens in a cookie that is secure (is not transmitted via HTTP, only via HTTPS) and httpOnly (can't be read by Javascript) and talks to the server over an encrypted channel (HTTPS). Once you know you have a secure channel between the server and client you can securely exchange JWT or whatever else you want.
This keeps thing simple. A simple implementation makes adoption easier but it also lets each layer do what it does best (let HTTPS handle encryption).
JWT isn't meant to store sensitive data. Once the server receives the JWT token and validates it, it is free to lookup the user ID in its own database for additional information for that user (like permissions, postal address, etc). This keeps JWT small in size and avoids inadvertent information leakage because everyone knows not to keep sensitive data in JWT.
It's not too different from how cookies themselves work. Cookies often contain unencrypted payloads. If you are using HTTPS then everything is good. If you aren't then it's advisable to encrypt sensitive cookies themselves. Not doing so will mean that a man-in-the-middle attack is possible--a proxy server or ISP reads the cookies and then replays them later on pretending to be you. For similar reasons, JWT should always be exchanged over a secure layer like HTTPS.
Let's discuss from the very beginning:
JWT is a very modern, simple and secure approach which extends for Json Web Tokens. Json Web Tokens are a stateless solution for authentication. So there is no need to store any session state on the server, which of course is perfect for restful APIs.
Restful APIs should always be stateless, and the most widely used alternative to authentication with JWTs is to just store the user's log-in state on the server using sessions. But then of course does not follow the principle that says that restful APIs should be stateless and that's why solutions like JWT became popular and effective.
So now let's know how authentication actually works with Json Web Tokens. Assuming we already have a registered user in our database. So the user's client starts by making a post request with the username and the password, the application then checks if the user exists and if the password is correct, then the application will generate a unique Json Web Token for only that user.
The token is created using a secret string that is stored on a server. Next, the server then sends that JWT back to the client which will store it either in a cookie or in local storage.
Just like this, the user is authenticated and basically logged into our application without leaving any state on the server.
So the server does in fact not know which user is actually logged in, but of course, the user knows that he's logged in because he has a valid Json Web Token which is a bit like a passport to access protected parts of the application.
So again, just to make sure you got the idea. A user is logged in as soon as he gets back his unique valid Json Web Token which is not saved anywhere on the server. And so this process is therefore completely stateless.
Then, each time a user wants to access a protected route like his user profile data, for example. He sends his Json Web Token along with a request, so it's a bit like showing his passport to get access to that route.
Once the request hits the server, our app will then verify if the Json Web Token is actually valid and if the user is really who he says he is, well then the requested data will be sent to the client and if not, then there will be an error telling the user that he's not allowed to access that resource.
All this communication must happen over https, so secure encrypted Http in order to prevent that anyone can get access to passwords or Json Web Tokens. Only then we have a really secure system.
So a Json Web Token looks like left part of this screenshot which was taken from the JWT debugger at jwt.io. So essentially, it's an encoding string made up of three parts. The header, the payload and the signature Now the header is just some metadata about the token itself and the payload is the data that we can encode into the token, any data really that we want. So the more data we want to encode here the bigger the JWT. Anyway, these two parts are just plain text that will get encoded, but not encrypted.
So anyone will be able to decode them and to read them, we cannot store any sensitive data in here. But that's not a problem at all because in the third part, so in the signature, is where things really get interesting. The signature is created using the header, the payload, and the secret that is saved on the server.
And this whole process is then called signing the Json Web Token. The signing algorithm takes the header, the payload, and the secret to create a unique signature. So only this data plus the secret can create this signature, all right?
Then together with the header and the payload, these signature forms the JWT,
which then gets sent to the client.
Once the server receives a JWT to grant access to a protected route, it needs to verify it in order to determine if the user really is who he claims to be. In other words, it will verify if no one changed the header and the payload data of the token. So again, this verification step will check if no third party actually altered either the header or the payload of the Json Web Token.
So, how does this verification actually work? Well, it is actually quite straightforward. Once the JWT is received, the verification will take its header and payload, and together with the secret that is still saved on the server, basically create a test signature.
But the original signature that was generated when the JWT was first created is still in the token, right? And that's the key to this verification. Because now all we have to do is to compare the test signature with the original signature.
And if the test signature is the same as the original signature, then it means that the payload and the header have not been modified.
Because if they had been modified, then the test signature would have to be different. Therefore in this case where there has been no alteration of the data, we can then authenticate the user. And of course, if the two signatures
are actually different, well, then it means that someone tampered with the data.
Usually by trying to change the payload. But that third party manipulating the payload does of course not have access to the secret, so they cannot sign the JWT.
So the original signature will never correspond to the manipulated data.
And therefore, the verification will always fail in this case. And that's the key to making this whole system work. It's the magic that makes JWT so simple,
but also extremely powerful.
The contents in a json web token (JWT) are not inherently secure, but there is a built-in feature for verifying token authenticity. A JWT is three hashes separated by periods. The third is the signature. In a public/private key system, the issuer signs the token signature with a private key which can only be verified by its corresponding public key.
It is important to understand the distinction between issuer and verifier. The recipient of the token is responsible for verifying it.
There are two critical steps in using JWT securely in a web application: 1) send them over an encrypted channel, and 2) verify the signature immediately upon receiving it. The asymmetric nature of public key cryptography makes JWT signature verification possible. A public key verifies a JWT was signed by its matching private key. No other combination of keys can do this verification, thus preventing impersonation attempts. Follow these two steps and we can guarantee with mathematical certainty the authenticity of a JWT.
More reading: How does a public key verify a signature?
I would explain this with an example.
Say I borrowed $10 from you, then I gave you an IOU with my signature on it. I will pay you back whenever you or someone else bring this IOU back to me, I will check the signature to make sure that is mine.
I can't make sure you don't show the content of this IOU to anyone or even give it to a third person, all I care is that this IOU is signed by me, when someone shows this IOU to me and ask me to pay it.
The way how JWT works is quite the same, the server can only make sure that the token received was issued by itself.
You need other measures to make it secure, like encryption in transfer with HTTPS, making sure that the local storage storing the token is secured, setting up origins.
Ref - JWT Structure and Security
It is important to note that JWT are used for authorization and not authentication.
So a JWT will be created for you only after you have been authenticated by the server by may be specifying the credentials. Once JWT has been created for all future interactions with server JWT can be used. So JWT tells that server that this user has been authenticated, let him access the particular resource if he has the role.
Information in the payload of the JWT is visible to everyone. There can be a "Man in the Middle" attack and the contents of the JWT can be changed. So we should not pass any sensitive information like passwords in the payload. We can encrypt the payload data if we want to make it more secure. If Payload is tampered with server will recognize it.
So suppose a user has been authenticated and provided with a JWT. Generated JWT has a claim specifying role of Admin. Also the Signature is generated with
This JWT is now tampered with and suppose the
role is changed to Super Admin
Then when the server receives this token it will again generate the signature using the secret key(which only the server has) and the payload. It will not match the signature
in the JWT. So the server will know that the JWT has been tampered with.
Only JWT's privateKey, which is on your server will decrypt the encrypted JWT. Those who know the privateKey will be able to decrypt the encrypted JWT.
Hide the privateKey in a secure location in your server and never tell anyone the privateKey.
I am not a cryptography specialist and hence (I hope) my answer can help somebody who is neither.
There are two possible ways of using cryptography in programming:
Signing / verifying
Encryption / decryption
We use Signing when we want to ensure that data comes from a trusted source.
We use Encryption when we want to protect the data.
Signing / verifying uses asymmetrical algorithms i.e. we sign with one key (private) and the data receiver uses the other (public) key to verify.
A symmetric algorithm uses the same key to encrypt and decrypt data.
The encryption can be done using both symmetric and asymmetric algorithms.
relatively simple article on subject
The above is common knowledge below is my opinion.
When JWT is used for simple client-to-server identification there is no need for signing or asymmetric encryption. JWT can be encrypted with AES which is fast and supersecure. If the server can decrypt it, it means the server is the one who encrypted it.
Summary: non-encrypted JWT is not secure. Symmetric encryption can be used instead of signing in case no third party is involved.
Let's say I have a typical CRUD API for a web application. I need to authorize users by a token, check user roles, etc.
Is there any reason why I should consider JWT over storing a randomly-generated token in a table like tokens(token, refresh_token, expiration_date)?
In my opinion, JWT is adding more complexity here:
Additional code to handle encoding/decoding
Need to store JWT secrets and keys
Token revocation problem
I have to hit a database to check user roles(although I can include them in a payload, there's also other stuff that I should check in my application), so no advantages here. The only benefit I can see here is that I can check token expiration data without hitting a database.
At the same time storing a randomly-generated token in a database is a dead-simple solution.
Am I missing something?
JWTs are often misunderstood. The main benefit they provide is statelessness. If you go to your database to query privileges upon each request anyway, that is pretty much lost, if not from a theoretical but from a practical point of view.
They are typically not stored in http-only cookies, which makes them vulnerable to XSS, but at the same time allows Javascript clients to read the payload (eg. who is logged in, what privileges they have and so on). Not being stored in cookies also allows them to be sent to different origins, which is pretty much the only reason they should not be stored in a http-only cookie (if and only if you understand and accept the risks of this).
JWTs are in no way better or magically more secure than plain old random session tokens - quite the opposite in most cases, especially that it is often overlooked that as opposed to server-side sessions, JWT payload is plaintext. It is protected against tampering by message authentication, but not protected against the user having a look, which sometimes might become an issue.
If you don't need the features above (statelessness, access from javascript), you should just not have the additional complexity of a JWT, you just need a plain old session then.
First thing you need to consider is who will generate the token.
In case of JWT, a valid OAUTH provider will generate the token. The benefits are as follows,
you can validate the legitimacy of the token, which will include checks for following,
a. audience
b. expiry
c. issued at
d. not before date
e. issuer
you can check the issuer based on just the public key which would avoid a network trip to another remote server such as database.
you can inject any payload which can include a userinfo, email, role or any custom attributes.
for a standard OAUTH JWT, you can test using common providers such as 'Okta'. As opposed to your custom generator, where you will have to provide a user a mechanism to retrieve such a token.
as far as the code to check, the JWT is quite straightforward with 3 parts separated by a "period". But there are libraries in java and other languages which can do the parsing for you - com.auth0, specifically jwt and rsa which will let you do the parsing and verification.
your code will be compliant and easily portable to another provider.
I am from a traditional HTML, frontend JS, css background so I am a little suspicious of doing token authentication from the frontend.
So when user logs in, JWT will be generated from the backend and be sent to the client. From then on, I would store it in localStorage or sessionStorage to authenticate them 'at frontend' every time user attempts to access private routes. Coming from the traditional 'always client to server communication' I am wondering if this approach is very secure. (although I do know that the decoding of JWT is exactly the same process whether it happens in the backend or the frontend). So are there any additional security breach I should be considering when routing on the frontend as opposed to routing on the backend?
EDIT**
Also, would my secret not be exposed to everyone if I decode on the frontend?
This approach is secure, and secret won't be exposed to everyone. Back end application usually reads the main uid and the access_token.
It is critical to use TLS/SSL in conjunction with JWT, to prevent man-in-the-middle attacks. In most cases, this will be sufficient to encrypt the JWT payload if it contains sensitive information. However, if we want to add an additional layer of protection, we can encrypt the JWT payload itself using the JSON Web Encryption (JWE) specification.
Of course, if we want to avoid the additional overhead of using JWE, another option is to simply keep sensitive information in our database, and use our token for additional API calls to the server whenever we need to access sensitive data.
I have a Laravel app which I'm trying to convert to NodeJS. In the original app we have an API for which access is protected by random generated tokens - assigned to each user and stored in our DB. We automatically generate this secret token when a user first registers then they use it for as long as they would like to use our services. (We verify subscription details for users using these tokens).
I'm trying to replicate the same on NodeJS but I'm a bit lost about the right authentication strategy to use, as passportJS has JSON Web Tokens (JWT) and 'hash'. They both seem correct but I can't figure out the difference and which would be most appropriate in this case.
If hash is the correct strategy would I have to use JWT to generate the token and assign it to each user? Probably I haven't understood properly the concept of hashes and token for authentications. What are the differences between hashes and token for authentication purposes?
I did some more research and found out that the JWT are not exactly what we were using or what we need for our app. We simply create SHA hashes for each user based on personal details and a secret key. This hash is now created and used in the new application correctly. It was simpler than I thought. And for those wanting to learn a bit more about JWT, this Medium article could help a lot:
https://medium.com/vandium-software/5-easy-steps-to-understanding-json-web-tokens-jwt-1164c0adfcec