Decoding an AWS Session Token

Question

We are using AWS Cognito Federated Identities to obtain a Session Token from the AWS Security Token Service, then leverage for securing our APIs via API Gateway. This is working well.

But within our web service, we sometimes must obtain the issuer and subject from the JWT token used to derive the Session Token. For this, we are exploring AWSSecurityTokenServiceClient.

But my question is whether it's possible to simply decode the Session Token without invoking the Security Token Service for every API call. Thoughts?

Answer 1

Here is an example of the response provided by AWS Security Token Service, via API Call to Cognito Federated Services:

{"IdentityId":"us-east-2:4628a310-f743-43bb-8808-6123c744c664","Credentials":{"AccessKeyId":"ASIATTD56AWGXWG2GGES","SecretKey":"0TOwO2JMgWQLd6FvVrX5m9UKsDcFfQW3goG3NQ8Z","SessionToken":"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","Expiration":"2019-09-27T18:13:42.000Z"}}

Note the SessionToken is fairly lengthy, but does not decode when pasting into https://jwt.io

Answer 2

This image has a full payload of what you are looking for, session Token and JWT token. I hope this is what you are looking for.

However, please note that only JWT token will be passed in API gateway.

Answer 3

Yes, JWT token can be decoded without Security Token Service for every API call.

Please copy-paste the JWT token https://jwt.io and you can see the details.