AWS-Lambda-Function-For-Cognito.js

/* ----------------------------------- preSignUp -------------------------------------------*/

exports.handler = async (event) => {
    
    // Confirm the user
    event.response.autoConfirmUser = true;

    // Set the email as verified if it is in the request
    if (event.request.userAttributes.hasOwnProperty("email")) {
        event.response.autoVerifyEmail = true;
    }

    // Set the phone number as verified if it is in the request
    if (event.request.userAttributes.hasOwnProperty("phone_number")) {
        event.response.autoVerifyPhone = true;
    }
    
    console.log(event);
    
    return event;
};
   

/* ---------------------------------------- defineAuthChallenge ---------------------------*/

exports.handler = async (event) => {
    
    console.log(event.request.session);
    console.log(event)
    
    if(event.request.userNotFound){
        // If user not found true.
        event.response.issueTokens = null;
        event.response.failAuthentication = null;
    } else if (event.request.session && event.request.session.length >= 3 && event.request.session.slice(-1)[0].challengeResult === false) {
        // The user provided a wrong answer 3 times; fail auth
        event.response.issueTokens = false;
        event.response.failAuthentication = true;
    } else if (event.request.session && event.request.session.length && event.request.session.slice(-1)[0].challengeResult === true) {
        // The user provided the right answer; succeed auth
        event.response.issueTokens = true;
        event.response.failAuthentication = false;
    } else {
        // The user did not provide a correct answer yet; present challenge
        event.response.issueTokens = false;
        event.response.failAuthentication = false;
        event.response.challengeName = 'CUSTOM_CHALLENGE';
    }
    
    console.log(event);
    
    return event;
};

/* ------------------------------------ createAuthChallenge ---------------------------------*/

const aws = require('aws-sdk');

// 

exports.handler = async event => {
    
    console.log(event);

    let secretLoginCode = "";
    if (!event.request.session || !event.request.session.length) {

        // This is a new auth session
        // Generate a new secret login code and mail it to the user
        // secretLoginCode = cryp.randomDigits(4).join('');
        secretLoginCode = Math.floor(1000 + Math.random() * 9000);
        if(event.request.userAttributes.email){
            await sendEmail(event.request.userAttributes.email, secretLoginCode);
        }else if(event.request.userAttributes.phone_number){
            await sendSMS(event.request.userAttributes.phone_number, secretLoginCode);
        }

    } else {
        // There's an existing session. Don't generate new digits but
        // re-use the code from the current session. This allows the user to
        // make a mistake when keying in the code and to then retry, rather
        // the needing to e-mail the user an all new code again.    
        const previousChallenge = event.request.session.slice(-1)[0];
        secretLoginCode = previousChallenge.challengeMetadata.match(/CODE-(\d*)/)[1];
    }

    // This is sent back to the client app
    // event.response.publicChallengeParameters = {
    //     email: event.request.userAttributes.email
    // };

    // Add the secret login code to the private challenge parameters
    // so it can be verified by the "Verify Auth Challenge Response" trigger
    event.response.privateChallengeParameters = { 
        secretLoginCode: secretLoginCode
    };

    // Add the secret login code to the session so it is available
    // in a next invocation of the "Create Auth Challenge" trigger
    event.response.challengeMetadata = `CODE-${secretLoginCode}`;
    
    console.log(event);

    return event;
};

async function sendEmail(emailAddress, secretLoginCode) {
    
    // 
    const ses = new aws.SES();
    
    const params = {
        Destination: { 
            ToAddresses: [emailAddress]
        },
        Message: {
            Body: {
                Html: {
                    Charset: 'UTF-8',
                    Data: `<html>
                                <body>
                                    <p>Hey there!</p>
                                    <p>Your <strong>OTP ${secretLoginCode}</strong>.
                                        <br>Don't share with anyone.
                                    </p>
                            </body>
                           </html>`
                },
                Text: {
                    Charset: 'UTF-8',
                    Data: `Your secret login code: ${secretLoginCode}`
                }
            },
            Subject: {
                Charset: 'UTF-8',
                Data: `${secretLoginCode} is your OTP for login`
            }
        },
        Source: 'Name <name@example.com>'
    };
    
    console.log(params);
    
    await ses.sendEmail(params).promise();
}

async function sendSMS(phoneNumber, secretLoginCode){
    
    aws.config.update({ region: "ap-southeast-1" });

    const sns = new aws.SNS();

    await sns.setSMSAttributes({
        attributes: {
          DefaultSMSType: 'Transactional'
        }
      }).promise(); 
      
    var params = {
        Message: secretLoginCode + ' is the OTP for login.',
        PhoneNumber: phoneNumber
    };
    
     console.log(params);
    
    await sns.publish(params).promise(); 
    
}


/* ------------------------------------------ verifyAuthChallenge -------------------------- */

exports.handler = async (event) => {
    
    console.log(event);
    
    const expectedAnswer = event.request.privateChallengeParameters.secretLoginCode; 
    
    if (event.request.challengeAnswer === expectedAnswer) {
        event.response.answerCorrect = true;
    } else {
        event.response.answerCorrect = false;
    }
    
    console.log(event);
    
    return event;
};