Custom sender Lambda triggers
The Lambda triggers CustomEmailSender and CustomSMSSender support
third-party email and SMS notifications in user pools. You can choose SMS and email
providers to send notifications to users from within your Lambda function code. When Amazon Cognito
sends invitations, MFA codes, confirmation codes, verification codes, and temporary
passwords to users, the events activate your configured Lambda functions. Amazon Cognito sends the
code and temporary passwords (secrets) to your activated Lambda functions. Amazon Cognito encrypts
these secrets with an AWS KMS customer managed key and the AWS Encryption SDK. The AWS Encryption SDK is a
client-side encryption library that helps you to encrypt and decrypt generic data.
Note
To configure your user pools to use these Lambda triggers, you can use the AWS CLI or SDK. These configurations aren't available from Amazon Cognito console.
- CustomEmailSender
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Amazon Cognito invokes this trigger to send email notifications to users.
- CustomSMSSender
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Amazon Cognito invokes this trigger to send SMS notifications to users.
Resources
Amazon Cognito doesn't send users' codes in plaintext in the events that it sends to custom sender triggers. The Lambda functions must decrypt codes in the events. The following concepts are the encryption architecture that your function must use to get codes that it can deliver to users.
- AWS KMS
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AWS KMS is a managed service to create and control AWS KMS keys. These keys encrypt your data. For more information see, What is AWS Key Management Service?.
- KMS key
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A KMS key is a logical representation of a cryptographic key. The KMS key includes metadata, such as the key ID, creation date, description, and key state. The KMS key also contains the key material used to encrypt and decrypt data. For more information see, AWS KMS keys.
- Symmetric KMS key
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A symmetric KMS key is a 256-bit encryption key that doesn't exit AWS KMS unencrypted. To use a symmetric KMS key, you must call AWS KMS. Amazon Cognito uses symmetric keys. The same key encrypts and decrypts. For more information see, Symmetric KMS keys.
