I'm implementing "Log In with PayPal" functionality. Should be fairly simple, but unfortunately PayPal lacks documentation (only some basic things are described).
I get authorization_code using "Log In with PayPal" widget. Than I make a request to https://api.sandbox.paypal.com/v1/identity/openidconnect/tokenservice and get JSON with access_token, refresh_token and id_token. I want to get unique user identifier, so I decode id_token, but I'm not able to verify signature of my id_token. Id_token header contains {"alg": "HS256", "typ": "JWT"}.
What secret should I use? Tried my app's secret (same that I use to access tokenservice), but it didn't work (using https://jwt.io/ debugger).
PayPal is not OpenID connect compliant. This answer explains the reasons.
PayPal expose a configuration endpoint - https://www.paypalobjects.com/.well-known/openid-configuration.It only support HS256 and does not support or mention about RS256. This could be due to a proprietary validation for ID token. For example a id token used as a bearer token.
Alternative solution would be to invoke userinfo endpoint as described by document. This endpoint can be invoked using access token and document says it would return the user_id
user_id - identifier for the end-user at the issuer.
Although it seems that user_id found in the userinfo is different from sub that could be extracted from id_token.
How to find public keys if signing algorithm is RS256
ID token is a JWT. As you have found out, it contains a JWS signature which acts as a MAC.
This signature is a signed using a private key. The receiver of the id token can validate the token using the public key. To find the public key, openid conenct specify a discovery document. You can read more about this from the specification
In the discovery document, you get a special endpoint to infer the configuration .well-known/openid-configuration. And one of the must have metadata of the configuration response is jwk_url
jwks_uri
REQUIRED. URL of the OP's JSON Web Key Set [JWK] document. This
contains the signing key(s) the RP uses to validate signatures from
the OP. The JWK Set MAY also contain the Server's encryption key(s),
which are used by RPs to encrypt requests to the Server. When both
signing and encryption keys are made available, a use (Key Use)
parameter value is REQUIRED for all keys in the referenced JWK Set to
indicate each key's intended usage. Although some algorithms allow the
same key to be used for both signatures and encryption, doing so is
NOT RECOMMENDED, as it is less secure. The JWK x5c parameter MAY be
used to provide X.509 representations of keys provided. When used, the
bare key values MUST still be present and MUST match those in the
certificate.
Related
I just realized that the userinfoendpoint doesn't give any useful info about the logged in user.
Now, I saw that you can get an id_token from ADFS tokenendpoint. This id_token is actually a JWT which contains the unique_name.
Now my question is, if it is safe to use this info without signature validation (since we don't have the private key of the HS256 algorithm and validation is as far as I understood, a thing for the issuer not for the client).
• There are two scenarios to your question of whether it is safe to use this info from an ID_token. First, your client, i.e., the application or authorization server will validate the token just like it validates the access token for any tampering. Also, it can validate the issuer to ensure that the correct issuer has sent back the token. Since there are many libraries to validate an ID token, you should use them for ID token validation purposes.
• Also, only confidential client applications should validate an ID token as their token holds a secret while public applications don’t benefit from validating an ID token as there is always a risk of a malicious user who can intercept and edit the keys used for validation of the token.
• As you are speaking of the case when you don’t have the private key to the algorithm used for encrypting the ID token, it must be a confidential client application. Thus, validating the ID token on the lines of access token and confirming the below claims are validated by your token validation library, you can then use the information retrieved from these claims for your purpose. The claims that need to be validated are as follows: -
Timestamps: the iat, nbf, and exp timestamps should all fall before or after the current time, as appropriate.
Audience: the aud claim should match the app ID for your application.
Nonce: the nonce claim in the payload must match the nonce parameter passed into the /authorize endpoint during the initial request.
Please find the below documentation link for more in-depth details on validating the tokens and the inherent process involved in it: -
https://learn.microsoft.com/en-us/azure/active-directory/develop/access-tokens#validating-tokens
No, sadly the userinfo endpoint only gives you a "sub".
You can validate the JWT yourself.
You should always check the signature.
I am very new to jwt and signature validation. I had a very basic query.
I am generating a token from MSAL(AAD).
When I use the token in jwt.io, I can see that it automatically populates the secret key and marks the signature as verified. How does jwt.io know about this?
From generating token point of view, I didn't mention anywhere explicitly to generate the token with any secret.
You don't show the details of your token here (which is ok), but I assume the token has a kid and maybe also a jku in the header.
The kidis the Key Id, and the jku the JSON Web Key Set URL.
Under that URL (you can paste it to your browser to see) you can find a set of JWKs (JSON Web Keys), basically a collection of public keys in a special format. In case of tokens issued by AAD you the JWKS_URI can be found on https://login.microsoftonline.com/common/v2.0/.well-known/openid-configuration.
JWT.io can read this information and find the key with the given kid and verify the token based on that.
This Q/A explains the verification of JWTs issued by AAD in more detail.
When building a Conversational Action with the new Actions SDK or Action Builder, you can define a webhook to handle business logic. This webhook then receives fulfillment requests with the following headers, among others:
Google-Actions-API-Version: "3"
Google-Assistant-Signature: "eyJhbGciOiJSUzI1NiIsImtpZC..."
How should that signature be verified? It's a JWT claim, but the key ID with which it was signed does not exist in the GCP account linked with the Action, and is not mentioned in the new Actions SDK documentation or in the Node.js fulfillment library documentation.
The signature is a JSON Web Token, which is an encoded way of transmitting some assertions that have been signed in a verifiable way. There are libraries that will both decode and verify JWTs. The general steps (some of which you can cache or shortcut) are:
Decode the header to get the kid (key id) and the payload to get the iss (issuer) fields. You'll also want the nbf (not before) and exp (expiration) fields to verify this was set recently and the aud field to verify that it matches your Google Cloud project ID.
Based on the issuer, access the well known openid configuration. Since the issuer is "https://accounts.google.com" you can access this at "https://accounts.google.com/.well-known/openid-configuration"
From the configuration document, you want the jwks_uri field, which is the URL to get the current JWT certificates. For Google, this is probably "https://www.googleapis.com/oauth2/v3/certs"
The certificate document should contain an array of keys. You want a key with the kid that matches the kid from the JWT. Note that these keys change frequently, but as long as you're within the window of the nbf and exp fields from the signature header, the key should exist in the certificate document.
With all this, you can then verify the signature portion of the JWT.
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.
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.