Verify OpenId Connect token generated by Cognito Identity pool

Question

I have a customer, that is using a Cognito Identity Pool in conjunction with a Cognito User Pool.
He is using the Api Method GetOpenId token to generate a JWT token for an unauthenticated user and wants to verify the JWT token in the backend.

https://docs.aws.amazon.com/cognitoidentity/latest/APIReference/API_GetOpenIdToken.html

However this seems to be possible only with tokens generated by the user pool, see:

https://aws.amazon.com/premiumsupport/knowledge-center/decode-verify-cognito-json-token/

Can the same be achieved with token from an identity pool? Where can i find the public keys used to verify the signature of the JWT?

Accepted Answer

I have not tried it myself, but if it is an OIDC compliant token, you should be able to verify it through the official verification process, getting the jwks url in the iss field of the token

Here is how to do it:

* From the token get the **iss** value
* Issue a GET on the URI built from  **iss**+/.well-know/openid-configuration https://cognito-identity.amazonaws.com/.well-known/openid-configuration
* From the JSON returned, get the **jwks_uri** field
* Issue a GET to the URI from the jwks_uri field to get the jwks https://cognito-identity.amazonaws.com/.well-known/jwks_uri
* Use the kid from the id token to select the right entry in the jwks to verify the signature

Verify OpenId Connect token generated by Cognito Identity pool

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