How to persist Cognito identity across pages in browser

The only way to get back to the same identity on page refresh would be to use the same token used to initialize that identity. You may want to refer to this question as the problems are similar (replacing the Facebook token with the OpenId Connect token from the developer authenticated identities flow).

To reiterate what that question says: the credentials in the SDK will not be persisted across pages, so you should cache the token to be reused.

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

I take a slightly different approach, that allows the SDK to refresh the credentials.

In short, I serialize the AssumeRoleWithWebIdentityRequest JSON object to session storage.

Here is an example using Angular, but concept applies in any JS app:

const AWS = require('aws-sdk/global');
import { STS } from 'aws-sdk';

import { environment } from '../../environments/environment';

const WEB_IDENT_CREDS_SS_KEY = 'ic.tmpAwsCreds';

// Handle tmp aws creds across page refreshes
const tmpCreds = sessionStorage.getItem(WEB_IDENT_CREDS_SS_KEY);
if (!!tmpCreds) {
  AWS.config.credentials = new AWS.WebIdentityCredentials(JSON.parse(tmpCreds));
}

@Injectable({
  providedIn: 'root'
})
export class AuthService {

...

  async assumeAwsRoleFromWebIdent(fbUser: firebase.User) {
    const token = await fbUser.getIdToken(false);
    let p: STS.Types.AssumeRoleWithWebIdentityRequest = {
      ...environment.stsAssumeWebIdentConfig,
      //environment.stsAssumeWebIdentConfig contains:
      //DurationSeconds: 3600,
      //RoleArn: 'arn:aws:iam::xxx:role/investmentclub-fbase-trust',
      RoleSessionName: fbUser.uid + '@' + (+new Date()),
      WebIdentityToken: token
    };

    // Store creds across page refresh, duno WTF `new AWS.WebIdentityCredentials(p)` don't have an option for this
    AWS.config.credentials = new AWS.WebIdentityCredentials(p);
    sessionStorage.setItem(WEB_IDENT_CREDS_SS_KEY, JSON.stringify(p));
  }

  removeAwsTempCreds() {
    AWS.config.credentials = {};
    sessionStorage.removeItem(WEB_IDENT_CREDS_SS_KEY);
  }

...

Few things to note:

• Upon login, I store the WebIdentityCredentials parameters as a JSON string in session cache.
• You'll notice I check the browser session cache in global scope, to handle page refreshes (sets creds before they can be used).

A tutorial with complete example can be found on my blog