How to persist Cognito identity across pages in browser

Question

I am authenticating through Cognito on client side browser using a developer authenticated identity. When my page loads (or is refreshed) I would like my application to remember the Identity for as long as the object is not expired (I think it lasts about an hour). However, I don't know how to retrieve the identity from Cognito without having to go through the developer authentication again.

Here is what the code does on page load:

var cognitoCredentials

$(document).ready(function() { 
    "use strict";

    cognitoParams = {
      IdentityPoolId: 'us-east-1:xxxxxxx'
    };

    cognitoCredentials = new AWS.CognitoIdentityCredentials(cognitoParams);
    AWS.config.credentials = cognitoCredentials;

});

And after logging in through the developer authentication:

cognitoCredentials.params.IdentityId = output.identityId;
cognitoCredentials.params.Logins = {
    'cognito-identity.amazonaws.com': output.token
};
cognitoCredentials.expired = true;

If I have already logged in, and then refresh the page, and try to log in again I get an error that I am trying to get an identity when I already have one Error: Missing credentials in config(…) NotAuthorizedException: Missing credentials in config "Access to Identity 'us-east-1:xxxxxxx' is forbidden."

However, I don't know how to access it. How do I retrieve the credentials so that when the page is refreshed, I can detect the previous identity given by Cognito?

Answer 1

Save at least accessKeyId, secretAccessKey, sessionToken in sessionStorage between pages. You can load these into AWS.config.credentials (after the AWS SDK has been loaded of course). It is much faster than waiting for Cognito to respond. Keep in mind, you'll have to manually refresh them with a token from one of the providers and this is only good until the temporary token expires (~1 hour).

var credKeys = [
    'accessKeyId',
    'secretAccessKey',
    'sessionToken'
];

// After Cognito login
credKeys.forEach(function(key) {
    sessionStorage.setItem(key, AWS.config.credentials[key]);
});

// After AWS SDK load

AWS.config.region = 'us-east-1'; // pick your region

credKeys.forEach(function(key) {
    AWS.config.credentials[key] = sessionStorage.getItem(key);
});

// Now make your AWS calls to S3, DynamoDB, etc