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Cognito custom flow sign-in sends a confirm code via email

Hi every one!!!

Emotional conversation between boss and employee

Boss: Do you know about Cognito?
Employee: I know a lot about it so what do you need?
Boss: I need to develop more on the login page about 2fa confirmation codes via email & email only, customers need it urgently.
Employee: I think Cognito has all the support so no need to worry. I talked to my boss about it and assured me that I could do everything.
Boss: Does it take a long time?
Employee: I'm a master at this so it'll be quick.
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So then he discovered the flow login feature only supports mfa with TOTP & SMS

OMGGGGGGG ●█▀█▄ ●█▀█▄ ●█▀█▄ ●█▀█▄

Please read this article it will help you \ʕ •ᴥ•ʔ/


Flow basic
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Cognito create user pool
Create 3 lambda function: 2faDefine.js, 2faCreate.js, 2faVerify.js

Cognito user pool

Note: User pool ID & App client ID

1./ Tab User: create user
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The newly created user has confirmation status is Force change password, now you need to run the script below to update confirmation status from Force change password to Confirmed.

aws cognito-idp admin-set-user-password --user-pool-id {user pool ID} --username {username} --password {password} --permanent 
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2./ Tab Sign-up experience
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Add custom attributes authChallenge, so after saving it will automatically add the prefix custom:, ouput custom:authChallenge.

This custom attribute contains a confirmation code and expiration time information when the end user submits a login.

3./ Tab App integration
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You find App client list, so click Client your app.

This custom attribute custom:authChallenge must have read and write permissions.

Option Authentication flow session duration has a value equal to the expiration time of the confirm-code.


4./ Tab User pool properties
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Add Lambda trigger with trigger type

Custom authentication

Custom authentication

Choose Define auth challenge mapping to lambda function 2faDefine.
Choose Create auth challenge mapping to lambda function 2faCreate.
Choose Verify auth challenge response mapping to lambda function 2faVerify.

Lambda deploy with code
1./ Function 2faDefine

2./ Function 2faCreate

Tab Configuration > General configuration

Change value of the option timeout up 5 minute because nodemailer send email not working.

Tab Configuration > Environment variables

CUSTOM_ATTRIBUTES = custom:authChallenge
USER_POOL_ID = xxxxxxxxx

3./ Function 2faVerify

Tab Configuration > Environment variables

CUSTOM_ATTRIBUTES = custom:authChallenge

Frontend Angular

Form login: when the end user clicks submit, it will call the function onSubmitLogin.
Form confirm code: when the end user enters the confirm-code, it will call the function onCodeCompleted.


If you want to refactor code, make sure the code example works first.
Please comment any issues you encounter and I will try to answer you.

Top comments (2)

lucdticdvn profile image

I feel that this world is wonderful when there are people like you. I am so happy to read these heartfelt shares. Thank you.

trantn profile image

thank you @lucdticdvn