Automatically getting AccessToken of authenticated-user in AWS Cognito PostAuthentication trigger event handler lambda

Question

I need to have an AccessToken for a user which has just been authenticated through our web-app via Cognito APIs, and use it inside the code in my custom PostAuthentication trigger event handler lambda function, to update one some user-attributes on the just authenticated user.

How can I get it?

I was hoping that the AccessToken value would already be available to the aforementioned lambda, either in its first [event] or second [context] argument, but it seems not present in there, according to documentation, if I didn't read the wrong one atleast.

Thank you.

Answer 1

No. We can not retrieve the access token in this lambda. (In fact, access token will generate in a later stage).

In order to update user attributes of the authenticated user, you should be able to use AdminUpdateUserAttributes action.

In the event argument of the Post Authentication Lambda , there are two attributes called userName and userPoolId as mentioned in the document . These values needs to be passed in the AdminUpdateUserAttributes action.

Please note that you should provide the permission in Post Authentication Lambda for cognito-idp:AdminUpdateUserAttributes .