Is it possible to modify AWS Cognito user attributes in the Lambda triggers

Question

Having a look at the AWS documentation,

https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-identity-pools-working-with-aws-lambda-triggers.html#cognito-user-pools-lambda-trigger-syntax-pre-signup

you have the following paramaters available in the Pre Sign-up Lambda fuction:

"request": {   "userAttributes": {     "string": "string",     .... }, "validationData": {<validation data as key-value (String, String) pairs, from the client>} 

is there a way to modify or add additional userAttributes the the event object?

for example:

// Modify an existing username... event.request.userAttributes.name.ucfirst();  // Add an additional attribute... event.request.userAttributes.nickname = "ANY_NAME";   callback(null, event); 

Answer 1

Yes, there's absolutely a way! You need to use AWS javascript SDK in your Lambda handler:

const AWS = require('aws-sdk'); AWS.config.update({region: 'ap-southeast-1'});  const cognitoidentityserviceprovider =   new AWS.CognitoIdentityServiceProvider({     apiVersion: '2016-04-18'   }); cognitoidentityserviceprovider.adminUpdateUserAttributes(   {     UserAttributes: [       {         Name: 'YOUR_USER_ATTRIBUTE_NAME',         Value: 'YOUR_USER_ATTRIBUTE_VALUE'       }     ],     UserPoolId: event.userPoolId,     Username: event.userName   },   function(err, data) {     ...   } ); 

Make sure to give your Lambda function the right policies (i.e. allows "cognito-idp:AdminUpdateUserAttributes" action) and the user pool has the attribute defined.

Answer 2

There isn't a way to mutate/augment attributes during sign up, but during sign in, you can mutate/augment them with the pre-token generation trigger.