I am newbie in JSON web token and micro services. I read in an articles that if i share the private, all services can verify user on their own. Then i tried to implement an application to practice.
Basically, I have two services A and B. A is used for authentication. Then, I tried implement a API that required authentication in service B. But when I used a token generated by authentication A in API, 401 status code and "Invalid signature." were returned.
So anyone can explain to me what I did wrong?
"Invalid signature" implies that the secret key that you used to encode the token doesn't match with the secret key you used for decoding it.
Make sure that the secret you are using for encoding and decoding are same.
For more info visit the JWT's site.
First of all the service to service communication only need public key to be shared in case of an asymmetric key pair such as RSA or ECDSA. The public key shared can be used to verify the signature and each service needs to sign JWT using their private key. You have to take care of securing the private key and make public key accessible to other services.
Verifying the user is a completely different use case. The user existence should be checked in database and a password check can be made which is authentication is all about. The JWT can be used to pass the user information along with access right with a signature done by the application using private key so that no one able to generate the same token. NOTICE : Signature is done using private key. In this way you have both authentication and authorisation using JWT.
Related
I'm trying to validate (and read roles from) a JWT Token. Sadly I can't use any adapter or auto configuration due to my overall application architecture.
It's no problem to decode the token like any other JWT Token, but I wonder if there is a library from Keycloak to archive this goal. (For example Just Parse the token to something like a KeycloakJWTToken and verify it by grabbing the secret from Keycloak Server or so)
Any easy-to-use client or so?
I'm using the Jose4J library:
https://bitbucket.org/b_c/jose4j/wiki/Home
Reading the claims inside a JWT token is straightforward:
import org.jose4j.jwt.JwtClaims;
import org.jose4j.jwt.consumer.JwtConsumer;
import org.jose4j.jwt.consumer.JwtConsumerBuilder;
public void parseJWT(String token) throws Exception {
JwtConsumer consumer = new JwtConsumerBuilder()
.setSkipAllValidators()
.setDisableRequireSignature()
.setSkipSignatureVerification()
.build();
JwtClaims claims = consumer.processToClaims(token);
System.out.println("* Parsed token: "+ claims.getRawJson() );
System.out.println("* Expiration date: " + new Date(claims.getExpirationTime().getValueInMillis()) );
}
More examples are available on GitHub:
https://github.com/pvliesdonk/jose4j/blob/master/src/test/java/org/jose4j/examples/ExamplesTest.java
Last remark: you do not need a key nor a secret to parse the JWT, but if needed, you can use the server (public) key to verify the token was signed by the keycloak server you are trusting.
The JWT website is listing all libraries for Token Signing/Verification:
https://jwt.io/#libraries-io
Keycloak access tokens are indeed JWT tokens. So, you can make full use of existing JWT libraries, including for validation as stated in the Keycloak official documentation:
If you need to manually validate access tokens issued by Keycloak you can invoke the Introspection Endpoint. The downside to this approach is that you have to make a network invocation to the Keycloak server. This can be slow and possibily overload the server if you have too many validation requests going on at the same time. Keycloak issued access tokens are JSON Web Tokens (JWT) digitally signed and encoded using JSON Web Signature (JWS). Because they are encoded in this way, this allows you to locally validate access tokens using the public key of the issuing realm. You can either hard code the realm’s public key in your validation code, or lookup and cache the public key using the certificate endpoint with the Key ID (KID) embedded within the JWS. Depending what language you code in, there are a multitude of third party libraries out there that can help you with JWS validation.
Besides, in Java EE, using the Keycloak Java adapter, the roles are typically mapped on the user Principal and i.e. allows isUserInRole(). That's one of the goals.
Also it is possible to cast the Principal from the SecurityContext as a KeycloakPrincipal, then obtain in turn a KeycloakSecurityContext from it. Using the KeycloakSecurityContext you have access to both ID and Access tokens (when applicable) and can read their properties, attributes and claims.
Note that it is also good practice, and simply useful, to use the Keycloak UI to "evaluate" your tokens. For instance, you can see the generated token in the Client Scopes tab (under Evaluate), as well as evaluate your policies and permissions in the Authorization tab of your Client(s) (under Evaluate).
Cf. https://www.keycloak.org/docs/latest/server_admin/#_client_scopes_evaluate
That's probably the best way to debug and test, while setting up your Client(s).
If you select a user in the Evaluate screen, the following example data is generated:
Generated Access Token (...)
Generated ID Token (...)
Generated User Info (...)
All examples are generated for the particular user and issued for the particular client, with the specified value of scope parameter. The examples include all of the claims and role mappings used.
Source: https://www.keycloak.org/docs/latest/server_admin/#generating-example-tokens-and-user-info
I'm receiving a JWT from Microsoft Azure, and I need to verify it on my server. The JWT is signed using RS256, i.e. using asymmetrical private/public key encryption.
I know that various libraries exist that can be used to verify a JWT signature directly from our backend server. But I'm curious if it wouldn't be possible to verify the JWT signature using an online service? Since it's using RS256 and not HS256, only public keys are involved in the verification process, no private keys or other secrets.
It seems like it would be simple to put up a REST service that can take an asymmetrically signed JWT, verify the signature and give back true/false. But when Googling I can't find any such services. Not even from big names in the JWT-world, like Auth0.
Why is that? Is there some security concern with letting another server verify the JWT signature?
I have a backend which exposes a RESTful API which is currently 'free for all' (but uses https).
I now want to add RBAC (role-based access control) and JWT seems the way to go and I read a lot about JWT, but don't see the advantage of using RSA over SHA to sign the token.
Assumption is that the user has authenticated and obtained a key, be it shared or public/private.
Now, it seems to me that in both cases - SHA or RSA HMAC - both parties (client and server) must have the shared key, or their half of the private/public key in the case of RSA. And the server must find that key (in a table or database) based on a claim in the JWT in order to verify the token's signature. Once it has confirmed the purported user in the JWT it will then authorise the request using the configured roles.
So what are the advantages of RSA in that scenario ?
I assume you're talking about RSxxx (e.g. RSA256) and HSxxx (e.g. HS256 (HMAC-SHA256)) algorithms here. The main difference is that HS256 is an symmetric algorithm while RS256 is an asymmetric algorithm. Symmetric algorithms just use one key (or secret) for signing and verifying, whereas asymmetric algorithms use the private key to sign and the public key to verify the token.
If you share the secret used for HS256, everyone knowing the secret could issue or modify and re-sign a token. That would defeat the purpose of the signature if you share the secret with the client. In case of RS256 or any other asymmetric algorithm, only the authentication server knows the private key and anyone who need to verify the token can use the public key to do so. The matching key is usually identified by the KID (Key Id) claim in the header of the token.
But usually, signing and verifying is only done on server side, the client does not need to verify the token and thus does not need to know the key or secret at all. Therefore you can in case of a simple service, when authentication and resource server are the same, still rely on a symmetric algorithms. But once you have one separate authentication server for several resource servers, asymmetric algotrithms should be used.
Thanks for the response, that does help make it clearer.
So basically, for a simple RESTful API, there is no real advantage using RSA over HSA.
Some points that may help others about token-based authentication:
Preamble: the following are all in the context of using SSL.
Firstly, a token is a substitute for username/password credentials: if a client has a token, it is equivalent to having username/password. It took me a while to figure that out. A bit like using a badge at a corporate printer: instead of entering username and password you just place your badge (the token) on the printer and it knows who you are and prints your document.
However, tokens make using an API much simpler because
the client simply adds its token to the http header,
the server only verifies the token,
neither have to deal with authentication flows involving username/pw and managing session cookies.
But the downsides are that
losing the token is like losing the username/password, and
in a complex system involving many components, tokens would have to be shared across all involved backend servers.
Secondly, the client doesn't strictly need to verify the token - it only needs the token - if someone gives you a key to their house or car, you don't typically check the key, you trust the person (maybe sometimes foolishly so) and use it. So a simple random string can serve as a token; the server maintains a simple table correlating tokens to users, no keys involved at all. If a client sends a token that the server doesn't have --> access denied. If it has a matching token --> look up the user that correlates to the token (typically followed by authorisation).
Thirdly, the server typically generates a token either based on trusting the client, or after the client has somehow authenticated, e.g . oauth. Afterwards, the client just sends the token with every request and the server looks it up in its table. However, such server-side tables for random-string tokens may become large and have to be persistent, so either a database or a file is required, and they are typically comparably slow, require maintenance etc, so enter using cryptographic signatures and jwt:
Fourthly, tokens with signature:
the server signs the token and sends it to the client - but the server does not have to store it, also no session cookies as described above
the client stores the token securely and sends it with every subsequent request (just like with a random string token)
the server receives the request, calculates the signature of the jwt, and compares it with the signature of the token sent by the client. Note that there is no file or DB lookup, only computing the signature again and comparing it with the signature sent by the client. If the signatures match then the token must be the same as the one the server issued and hence the jwt header and payload are also the same as issued by the server
the server now interprets the payload, esp. the user (and typically performs authorisation)
So, using jwt means the server does NOT need
a database or file with user names and tokens
to save tokens
to maintain session cookies
It only needs to create and compare a signature. And for that it needs a cryptographic key. This can be a symmetric key for a simple API or an asymmetric key for more complex systems where public keys must be shared.
Hope this helps some other tortured souls who grappled with this topic.
How does the generate-jwt policy work in API Connect? Does it invoke a authorization server in back end to generate the JWT? For example in real life scenarios, we have a authorization server which validates the user credentials and gives back the JWT which is n used in subsequent calls. But here i don't see any authorization server is needed we simply mention the claims the encryption algorithms and it gives back a JWT. Correct me if I am wrong.
Another related question:
I believe there are three possible ways to mention the secret to sign the JWT:
Private/Public key pair (RSA)
JWK
Shared Secret Key
How is the Shared Secret Key implemented in API Connect.
NOTE: I need to invoke a system which is exposed using JWT.
This policy does not invoke any authorization server. It only generates a JWT token, based on the input params that you provide. That authorization process should happen before the JWT generation.
The shared secret key in the policy can be provided in two ways:
a JWK: defining a variable with the JWK information
a Crypto Object: defined in datapower and referenced in the jwt policy
I am studying a bit about JSON Web Token. I understood that header+claims get signed by a secret key and the encoded result gets concatenated to "header.claims.signature" and finally sent back to client.
I have some basic doubts:
Do we need to validate the token at client/consumer (once it receives from server, for sake of authenticity)? Is it a standard at all or not necessary? Any example for reference on this?
If the client needs to validate the token, I guess it has to know the secret key to decrypt/decode. Is there any other way to ask client validate on its own without sharing server's secret key?
If client knows the secret key, I guess it can create its own token too. If such is the case, do the server need to accept such tokens (or is application/business dependent?)
Do we need to validate the token at client/consumer
On client side you usually don't validate the token. Treat it just as an opaque token. Keep it safe and use it when making requests to the server.
If the client needs to validate the token, I guess it has to know the secret key to decrypt/decode.
As mentioned above, the client doesn't need to validate the token.
In any cases in which the authentication server (the instance that authenticates the user and issues the token) and the resource server (the instance that owns a proteceted resource and requires a token for authorization) are not the same, signing and validation of the token is usually done with asymmetric algorithms like RS256 in which the private key is used to sign the token and only known by the authentication server, and the public key is used to verify the signature.
If client knows the secret key, I guess it can create its own token too. If such is the case, do the server need to accept such tokens (or is application/business dependent?)
That's why a client should not know the secret key.
When symmetric key algorithms (e.g. HS256), in which the same key is used to sign and verify a signature are used, you can't allow the client to know the key, as it could be abused to create a fake token. Then JWT would be pointless. For asymmetric keys, there's no risk if the client knows the public key.