So, I have a django project, and have added JWT authentication. The problem is that each time I use TokenObtainPairView with the same credentials I get different access and refresh tokens. Is this the default behavior, as I have not changed anything in the settings? Is there a way to get the previous token unless it has expired?
If you need more info please let me know.
JWTs aren't stored anywhere, that's the entire point of them. So you can never get "the" token again. You will get an equivalent, newly generated token. Since tokens incorporate timestamps/random ids etc, you probably won't ever get the same token twice.
I am using Spring Security OAuth2 and JWT tokens. My question is: How can I revoke a JWT token?
As mentioned here
http://projects.spring.io/spring-security-oauth/docs/oauth2.html, revocation is done by refresh token. But it does not seem to work.
In general the easiest answer would be to say that you cannot revoke a JWT token, but that's simply not true. The honest answer is that the cost of supporting JWT revocation is sufficiently big for not being worth most of the times or plainly reconsider an alternative to JWT.
Having said that, in some scenarios you might need both JWT and immediate token revocation so lets go through what it would take, but first we'll cover some concepts.
JWT (Learn JSON Web Tokens) just specifies a token format, this revocation problem would also apply to any format used in what's usually known as a self-contained or by-value token. I like the latter terminology, because it makes a good contrast with by-reference tokens.
by-value token - associated information, including token lifetime, is contained in the token itself and the information can be verified as originating from a trusted source (digital signatures to the rescue)
by-reference token - associated information is kept on server-side storage that is then obtained using the token value as the key; being server-side storage the associated information is implicitly trusted
Before the JWT Big Bang we already dealt with tokens in our authentication systems; it was common for an application to create a session identifier upon user login that would then be used so that the user did not had to repeat the login process each time. These session identifiers were used as key indexes for server-side storage and if this sounds similar to something you recently read, you're right, this indeed classifies as a by-reference token.
Using the same analogy, understanding revocation for by-reference tokens is trivial; we just delete the server-side storage mapped to that key and the next time the key is provided it will be invalid.
For by-value tokens we just need to implement the opposite. When you request the revocation of the token you store something that allows you to uniquely identify that token so that next time you receive it you can additionally check if it was revoked. If you're already thinking that something like this will not scale, have in mind that you only need to store the data until the time the token would expire and in most cases you could probably just store an hash of the token so it would always be something of a known size.
As a last note and to center this on OAuth 2.0, the revocation of by-value access tokens is currently not standardized. Nonetheless, the OAuth 2.0 Token revocation specifically states that it can still be achieved as long as both the authorization server and resource server agree to a custom way of handling this:
In the former case (self-contained tokens), some (currently non-standardized) backend interaction between the authorization server and the resource server may be used when immediate access token revocation is desired.
If you control both the authorization server and resource server this is very easy to achieve. On the other hand if you delegate the authorization server role to a cloud provider like Auth0 or a third-party component like Spring OAuth 2.0 you most likely need to approach things differently as you'll probably only get what's already standardized.
An interesting reference
This article explain a another way to do that: Blacklist JWT
It contains some interesting pratices and pattern followed by RFC7523
The JWT cann't be revoked.
But here is the a alternative solution called as JWT old for new exchange schema.
Because we can’t invalidate the issued token before expire time, we always use short-time token, such as 30 minute.
When the token expired, we use the old token exchange a new token. The critical point is one old token can exchange one new token only.
In center auth server, we maintain a table like this:
table auth_tokens(
user_id,
jwt_hash,
expire
)
user_id contained in JWT string.
jwt_hash is a hash value of whole JWT string,Such as SHA256.
expire field is optional.
The following is work flow:
User request the login API with username and password, the auth server issue one token, and register the token ( add one row in the table. )
When the token expired, user request the exchange API with the old token. Firstly the auth server validate the old token as normal except expire checking, then create the token hash value, then lookup above table by user id:
If found record and user_id and jwt_hash is match, then issue new token and update the table.
If found record, but user_id and jwt_hash is not match , it means someone has use the token exchanged new token before. The token be hacked, delete records by user_id and response with alert information.
if not found record, user need login again or only input password.
when use changed the password or login out, delete record by user id.
To use token continuously ,both legal user and hacker need exchange new token continuously, but only one can succeed, when one fails, both need to login again at next exchange time.
So if hacker got the token, it can be used for a short time, but can't exchange for a new one if a legal user exchanged new one next time, because the token validity period is short. It is more secure this way.
If there is no hacker, normal user also need exchange new token periodically ,such as every 30 minutes, this is just like login automatically. The extra load is not high and we can adjust expire time for our application.
source: http://www.jianshu.com/p/b11accc40ba7
This doesn't exactly answer you question in regards to the Spring framework, but here's an article that talks about why if you need the ability to revoke JWT's, you might not want to go with JWT's in the first place, and instead use regular, opaque Bearer tokens.
https://www.dinochiesa.net/?p=1388
One way to revoke a JWT is by leveraging a distributed event system that notifies services when refresh tokens have been revoked. The identity provider broadcasts an event when a refresh token is revoked and other backends/services listen for the event. When an event is received the backends/services update a local cache that maintains a set of users whose refresh tokens have been revoked.
This cache is then checked whenever a JWT is verified to determine if the JWT should be revoked or not. This is all based on the duration of JWTs and expiration instant of individual JWTs.
This article, Revoking JWTs, illustrates this concept and has a sample app on Github.
For Googlers:
If you implement pure stateless authentication there is no way to revoke the token as the token itself is the sole source of truth
If you save a list of revoked token IDs on the server and check every request against the list, then it is essentially a variant of stateful authentication
OAuth2 providers like Cognito provides a way to "sign out" a user, however, it only really revokes refresh token, which is usually long-lived and could be used multiple times to generate new access tokens thus has to be revoked; the existing access tokens are still valid until they expire
What about storing the JWT token and referencing it to the user in the database? By extending the Guards/Security Systems in your backend application with an additional DB join after performing the JWT comparison, you would be able to practically 'revoke' it by removing or soft-deleting it from the DB.
In general, the answer about tokens by reference vs. tokens by value has nailed it. For those that stumble upon this space in future.
How to implement revocation on RS side:
TL;DR:
Take a cache or db that is visible to all your backend service instances that are verifying tokens. When a new token arrives for revocation, if it's a valid one, (i.e. verifies against your jwt verification algo), take the exp and jti claims, and save jti to cache until exp is reached. Then expire jti in cache once unixNow becomes > exp.
Then on authorization on other endpoints, you check everytime if a given jti is matching something in this cache, and if yes, you error with 403 saying token revoked. Once it expires, regular Token Expired error kicks in from your verification algo.
P.S. By saving only jti in cache, you make this data useless to anyone since it's just a unique token identifier.
The best solution for JWT revocation, is short exp window, refresh and keeping issued JWT tokens in a shared nearline cache. With Redis for example, this is particularly easy as you can set the cache key as the token itself (or a hash of the token), and specify expiry so that the tokens get automatically evicted.
I found one way of resolving the issue, How to expire already generated existing JWT token using Java?
In this case, we need to use any DB or in-memory where,
Step 1: As soon as the token is generated for the first time for a user, store it in a db with the token and it's "issuedAt()" time.
I stored it in DB in this JSON format,
Ex: {"username" : "username",
"token" : "token",
"issuedAt" : "issuedAt" }
Step 2: Once you get a web service request for the same user with a token to validate, fetch "issuedAt()" timestamp from the token and compare it with stored(DB/in-memory) issued timestamp.
Step 3: If stored issued timestamp is new (using after()/before() method) then return that the token is invalid (in this case we are not actually expiring the token but we are stop giving access on that token).
This is how I resolved the issue.
I am using django-rest-framework-jwt in my backend and calling API's from Angular Project.
When user try to login on multiple Browsers, each time a new token is generated for the user on new browser. And every token is valid.
What I want is that when user is already logged in in one browser and he/she tries to login on second different browser the previous token for first browser should be invalidated.
In a simple word, NO, you can't just avoid generating tokens unless you made a little twist in django-rest-framework-jwt module. But that's not pure jwt anymore.
JWT stands for JSON Web Tokens and it's a mechanism for exchanging data between computer systems that happens to be convenient for generating authorization headers that can be used to implement statless auth in web apps.
SO
stateless means that you don't track user tokens, You just verify them. If token is valid and the payload is valid, then OK. It doesn't care how many tokens are generated and it doesn't care that they are related to one user. The token is created based on timestamp and will be verified compared to lifetime and timestamp of it.
It means that django rest jwt module, will create a token based on current timestamp of system, whenever user request for it.
Remember you can't delete a jwt token. Because it's not stored in database. So if your token is spoofed, that's it. You can't do anything with it, unless life cycle of the token ends and token expire.
If you want to track these tokens and be able to control them and for example don't create redundant tokens for a user as you asked:
consider changing to another token based authentication that stores token in database so you could track it.
change jwt system to what is suitable for you (I did it before). For example add a lookup id in database and check tokens by that bounded to each user. I know it's not jwt anymore, But you can still use some goodies of it. Like don't hit database on not valid jwt tokens and store some payload in it, if verified don't hit database for that info. Like permissions and ...
I am starting to work on an authentication system for an angular 2 Single Page Application using django-rest framework as back-end. I'd also like to have some kind of "remember me" functionality that is going to keep users logged in for a certain amount of time.
From what I have read so far, it seems that the best authentication method for this kind of Angular 2 SPA/REST API is using jwt (json web token). For jwt authentication, I looked at the django-rest-framework-jwt (https://github.com/GetBlimp/django-rest-framework-jwt).
The problem that I see is that the token needs to have a short life span (few minutes to a few hours...) in order to minimize security issues if the token get stolen. The token now needs to be refreshed frequently to avoid the user from being disconnected while using the application. In this case, a "remember me" functionality is posing problem since the token have a short life span.
I thought about a solution involving a second token that would serve as a refresh token. It would be opaque, have a longer life span and would contain information specific to the user (ip address or something like that) so that if it get stolen, the information specific to the user being different would render this refresh token invalid.
So here are my questions:
1- I would like to know if they are existing solutions addressing this problem. As any security/authentication issues, I prefer to rely on well tested solutions to avoid getting my API compromised.
2- Would the refresh token based on specific user infos be a good idea?
3- Any other ideas how I could implement what I want?
For your situation, you really need a way to store issued tokens.
I always use an OAuth2.0 server setup that manages the auth and returns tokens the OAuth setup uses a database to manage everything so it's easy to manage and revoke tokens.
The database schema would be like this http://imgur.com/a/oRbP2 the problem with using just JWT without any management over the issued tokens with long expiration you have that security issue of not being able to revoke easily.
I would advise against including any such thing as a password in the JWT and requiring them to change it what if they use that password everywhere, then they would have to change that everywhere.
Updated from comments
Sessions Authentication use session_id which most the time is stored in a cookie and this is attached to every outgoing request. It is stateful. It is nothing more than a unique identifier that associates a user account that the server has in memory/database. For example, this can course problems when running multiple servers/instances when scaling your infrastructure.
Token Authentication no session is persisted on the server so this means it is stateless. It normally uses the header Authorization: Bearer REPLACE-WITH-TOKEN . This means that this token can be passed to multiple different servers/instances because the authentication is not limited to the server that you initiated the authentication on. This helps with scaling your infrastructure. Tokens can also be passed to other clients.
RESTful API's are stateless so there must not be a session state stored on the server. Instead, it must the handled entirely by the client so that's why token authentication is used.
I had the exact problem when trying to use JWT with an application that needed a lot more than JWT was designed for. OAuth2.0 has a lot more options that I believe are necessary to meet your requirement in the safest manner possible and even features that you may find very useful in the future as your Application may grow and need more features with regards authentication.
I am trying to get my head around secure authentication. Here is the safest method I can think of.
Send an encrypted username + SHA-256ed password to the server and wait for a yes / no response. But the problem with this is a hacker could hack the response to be a yes when it should be a no, giving them unauthorized access to that account.
I am thinking you could work around it by encrypting the response and then, instead of storing it in a Boolean, calling a function that changes state of the application. But because the hacker can make the server say no and yes from his control he can find out the encryption key and still change the result.
That seems kind of insecure, right? What's stopping the hacker from isolating the function that logs you in or the Boolean?
Or am I just being naive and everything really is that insecure? I suppose the only real safe way to do it is to store if the user passed authentication on the authorization server and do a quick Boolean check to see if the user is logged in before every server action.
As Banthar said in his comment, the authorization check should always be performed on the server.
The standard way of implementing this kind of thing is by using a token: the client sends a username and password to the server. If the credentials given by the client succeed authentication, then the server generates a security token, stores it somewhere for later chacks and also sends the token back to the client. For every following request to the server, the client should send the token along with the request parameters, allowing the server to check if the token is valid. The server executes the request only if it can verify that the token is legitimate and authorized, any doubt should result in the server revoking the token.
This method is quite similar to the one you describe in the last part of your post.
The token generated by the server should be a value which cannot be forged: it cannot be a simple integer value incremented for each generated token, since a hacker could easily predict a valid value. It cannot be built using only information available to the client, for the same reason (although it would require more work for a hacker, he could ultimately forge a valid token). Also, on the server, the token should be attached with information allowing the server to easily and uniquely verify the token: a small variation in the connection information should result in the token being revoked. Token values should never be reused (with a token of finite length, there will still be a chance that a token value is reused, so figure out a length which is a good compromise between security and practicability). Finally, the token for a valid session should be regularly updated during the session, to prevent a malicious user steeling the session.
There are many ways to implement this, but the details depend on the security level you are trying to achieve. Using some sort of secret key to generate the token on the server is generally a bad idea, since there is always a chance that the key is leaked. The time when the token is generated may also be predictable. Pseudo-random number generators available to any programming languages have to be properly seeded so that the sequence of numbers cannot be predicted.
Finally, note that no authentication logic ever is completely safe: building more safety in your logic only makes the job harder to a hacker. Think about the incentive for a hacker to break into your system, and devise your logic so that the amount of work for breaking into the system is not worth the resource cost (time, money, specialty hardware...). And do never forget that obscurity does not mean security: let people review your process and comment on it, they may well think about some flaw that you had not seen.