Hello Community,
I'm working on an AWS Lambda function to authenticate users with Amazon Cognito using the USER_PASSWORD_AUTH flow. Despite following the documentation and making sure my setup in the AWS Cognito User Pool is correct, I've encountered several issues, initially with the USER_SRP_AUTH flow and now trying to switch to a simpler USER_PASSWORD_AUTH flow for authentication.
The Lambda function is supposed to receive a username and password, calculate a secret hash using the client secret, and then use these to authenticate against Cognito. However, I've faced errors related to the secret hash not matching and missing required parameters when I was attempting the SRP flow. I've corrected the algorithm from RS256 to sha256 for the secret hash calculation, ensured the username and client credentials are correct, and now I am trying to implement the USER_PASSWORD_AUTH flow to simplify the process.
Here's the gist of my current Lambda function:
const AWS = require('aws-sdk');
const crypto = require('crypto');
// Configuration variables
const clientId = 'YOUR_COGNITO_APP_CLIENT_ID';
const clientSecret = 'YOUR_COGNITO_APP_CLIENT_SECRET';
exports.handler = async (event) => {
const username = event.username; // Assuming these are passed in the event
const password = event.password;
// Calculate secret hash
const secretHash = calculateSecretHash(clientId, clientSecret, username);
// Setup params for initiateAuth call
const params = {
AuthFlow: 'USER_PASSWORD_AUTH',
ClientId: clientId,
AuthParameters: {
USERNAME: username,
PASSWORD: password,
SECRET_HASH: secretHash
},
};
try {
const cognitoIdentityServiceProvider = new AWS.CognitoIdentityServiceProvider();
const data = await cognitoIdentityServiceProvider.initiateAuth(params).promise();
// Handle successful authentication
} catch (err) {
console.error('Authentication error:', err);
// Handle errors
}
};
function calculateSecretHash(clientId, clientSecret, username) {
const hmac = crypto.createHmac('sha256', clientSecret);
hmac.update(username + clientId);
return hmac.digest('base64');
}
I've ensured that my Cognito User Pool and App Client settings are configured to allow USER_PASSWORD_AUTH. However, I've encountered various errors during implementation, from "SecretHash does not match" to "Missing required parameter SRP_A" when attempting the SRP flow.
Questions:
- Are there common pitfalls or overlooked configurations in setting up Lambda for Cognito authentication using USER_PASSWORD_AUTH?
- How can I ensure that the secret hash calculation is always correct and matches what Cognito expects?
- Any suggestions on debugging methods or tools that can help isolate and resolve these authentication issues?
- Any advice, insights, or references to documentation would be greatly appreciated. Thank you in advance for your help!