When token based authantication is compared to traditional server authantication, it is said that: traditional method keeps login info in memory on server side, but in token based authantication server keeps nothing. Information about logged in user is stored in token itself.
However, I didn't get one point here. If server doesn't store anything, how does server validate the token? I think it should store the secret key to decrypt the token and then validate.
If so, where is it stored? If not what poin did I miss?
The server issuing the token, digitally signs the token with a private key.
The service consuming the token only needs the public key to validate the token. It can download the public key from the issuing server on startup or first use. After that, it does not need to communicate with the issuing server to validate tokens. If the signature is valid, the service trusts the contents of the token.
For example, look at the "jwt", it uses "ssh" keys
Related
I have a private API, that I want 3rd party clients to authorize without sending sensitive information to the client, like a password. The usual flow in this case is:
We give a secret one time token to a client
Upon activating this token (e.g. calling api with this token)he's able to create an account by providing a password.
Client authorizes with this password and receives a secret token
This secret token is used with every api call.
The issue with this flow is when we're sending him one time token. If someone uses it first, he receives all the data he wanted.
Atm asymmetric encryption is used everywhere, https (ssl) is based on it. I wonder if there's such thing as asymmetric authentification. As I see this flow is:
A client and a server generates 2 magic tokens client_private_token, client_secret_token, server_public_token, server_secret_token.
We save opponents public tokens for example in settings files on both sides.
The server responds with server_public_token
The client uses client_private_token to generate some session_token and send it with every request that requires authorization
The server uses its server_private_token and user_public_token to verify that this session_token is valid.
The flow is very similar to ssl, but instead of encrypting data we just generate magic strings that proof that it's we.
Please don't confuse it with JWT, as JWT is just a payload with some information and server signature with it. To create a JWT user needs to be authorized in the first.
Also if there are such things it would be great to have clients to modern languages like java, js, python etc
How does the server validate the JWT token?
Where is it stored?
How does the token expire after specific days?
On the client side, I store the token and send it to each query. But what's happening on the server side?
It could do with some entry that works
I'm not a JWT expert, so if some of what I write is wrong, I'm very happy to be corrected.
1) When distributing the JWT, the server will sign it using a private key. The private key is top secret, and must be stored securely on the server. This signature can then be verified using a public key, which confirms that this token was indeed signed by the server (using the top secret private key). The public key is not necessarily secret and can be widely distributed to anyone who needs to verify that the token was signed by that server.
2) The JWT does not really need to be stored anywhere on the server, as the server can verify that it's a valid token whenever it receives it. As the server is also likely to generate JWT, some servers will use a cache to store generated and valid JWT to increase performance. So in short, the JWT does not need to be stored by the server.
3) The JWT contains lots of data, including an expiration time (or time when it was created, and duration for how long it's valid). In addition to verifying the token using the public key, the server will discard valid tokens that have expired.
4) Before processing your request, the server will at minimum use the public key to verify that the token is genuine and check the expiration time. If it passes those tests, the server might also do additional checks with the data stored in the JWT before processing your request. These checks might include checking if your user ID has permission to access the data you are trying to access, check if you're located in a country to has access to the data, and so on. It can change wildly from a case to case basis.
It's a little bit of a broad question. I'll try to answer some specific points though.
How does the server validate the JWT token?
JWTs are typically digitally signed.
The token server signs the token using either symmetric or asymmetric cryptography.
The resource server validates the token by checking the signature against the symmetric key or public key.
Where is it stored?
This is up to the client.
In the case of a single page application, the client can store the token in local or session storage.
How does the token expire after specific days?
A JWT always has an expiry time, set in the token when it is created.
And since the token is signed, this time cannot be changed by someone without the key.
The resource server must check the expiry time after validating the signature.
Currently I'm learning about JWT and started with the token based authentication. I don't understand the sentence from the article:
Token based authentication works by ensuring that each request to a
server is accompanied by a signed token which the server verifies for
authenticity and only then responds to the request.
What is signed token? What does it mean to sign a token? I can't find the question on SO.
A signature is something that can be verified.
The main problem you're trying to solve is this: the server creates some arbitrary value, the token, which it gives to the client. The client subsequently gives it back to the server as proof of something (proof that they're authenticated, for instance). Now, how can the server be sure that the token is genuine, and the client didn't just make it up?
That's where the signature comes in. It's part of the token, and the server can verify that it had previously created that signature, and that the signature was created for this particular token. In a nutshell, the signature is a hash of the contents of the token plus a secret only the server possesses; to verify the signature the server repeats the hash of the token's contents and the secret only it has, and if it matches, that means the token's signature must have been created the same way which assures the two desired attributes of authenticity.
For the gnarly details of how a JWT signature is computed specifically, read the specification.
I am using JWT token for rest api's security.
When user is logged in check user's credentials with DB.
If it matched we are encrypting it for further security and then passing it to jwt to create a token
Now in order to match user's token we need to keep password somewhere so that we can match them when user sends any request after logged in
we can do it 2 ways
1. Keep detail in Database and each time rest call is fired check token with token in Database which is too costly for each rest call
2. Preserve secret somewhere in JVM and use it. Here I have tried HttpSession from package
javax.servlet.http.HttpServletRequest
// My key issue code
// Encrypt it
Key key = keyGenerator.generateKey(password);
jwtToken = Jwts.builder()
.setSubject(username)
.setIssuer(uriInfo.getAbsolutePath().toString())
.setIssuedAt(new Date())
.setExpiration(toDate(LocalDateTime.now().plusMinutes(1)))
.signWith(SignatureAlgorithm.HS512, key)
.compact();
// Adding details to session
HttpSession httpSession = currentRequest.getSession();
httpSession.setAttribute("userSecret", password)
This works fine for single Server instance.
But at some point we need to scale up and run multiple instance of server.
How do we handle this case where user may logged in using 1 instance and may serving rest call using another instance using load balancing.
As users secret is available only in first Server's JVM.
You can share the private key, which was used for encrypting the JWT, among the servers. When a servers gets an API call, you can try to decrypt the JWT with the private key. If the decryption is successful, you have a valid a JWT and you can process the request. If the decryption fails, that means it's an invalid JWT. Once a JWT has been created, you don't need to hit the database. That's the primary usage of JWT in my opinion.
I am not sure what you mean by userSecret.
Trying to understand the 2-legged client credentials scheme in OAuth2. Some people state that JWT is great format for Access Token because it is self-contained and resource server doesn't need to verify the token from the authorization server (STS). But how is this done? The only way I see the resource server could itself validate the JWT is by storing a public key on the server, which is used to verify the signature.
When using a JWT as an access token, the Resource Server doesn't need to call out to the Authorization Server to verify it. Indeed the Resource Server will need to store the public key of the Authorization Server to do so. Obtaining that public key is an out-of-band process.
Verification of a JWT consists of checking the signature plus some additional checks on claims embedded in the token e.g. timestamps (iat, exp, nbf) and identifiers (aud).
The advantage of JWT over other forms of signed data/tokens is that JWTS are standardized and flexible wrt. cryptography used by them which makes it possible to use standard libraries to create/verify them instead of having to write custom code.