Pre-request Postman script for Cognito

gistfile1.txt

const echoPostRequest = {
  url: 'https://cognito-idp.eu-central-1.amazonaws.com/',
  method: 'POST',
  header: {
    'Content-Type': 'application/x-amz-json-1.1',
    'X-Amz-Target': 'AWSCognitoIdentityProviderService.InitiateAuth'
  },
  body: {
    mode: 'application/json',
    raw: JSON.stringify(
      {
        "AuthParameters": {
          "USERNAME": pm.environment.get("USERNAME"),
          "PASSWORD": pm.environment.get("PASSWORD")
        },
        "AuthFlow": "USER_PASSWORD_AUTH",
        "ClientId": pm.variables.get('COGNITO_CLIENT_ID')
      })
  }
};

var getToken = true;
if (!pm.environment.get('COGNITO_ACCESS_TOKEN_EXPIRY') || !pm.environment.get('COGNITO_ACCESS_TOKEN')) {
  console.log('Token or expiry date are missing')
} else if (pm.environment.get('COGNITO_ACCESS_TOKEN_EXPIRY') <= (new Date()).getTime()) {
  console.log('Token is expired')
} else {
  getToken = false;
  console.log('Token and expiry date are all good');
}

if (getToken === true) {
  pm.sendRequest(echoPostRequest, function (err, res) {
    console.log(err ? err : res.json());
    if (err === null) {
      console.log('Saving the token')
      var responseJson = res.json();
      pm.environment.set('COGNITO_ACCESS_TOKEN', responseJson.AuthenticationResult.IdToken)

      var expiryDate = new Date();
      expiryDate.setSeconds(expiryDate.getSeconds() + responseJson.AuthenticationResult.ExpiresIn);
      pm.environment.set('COGNITO_ACCESS_TOKEN_EXPIRY', expiryDate.getTime());
    }
  });
}