Amazon Cognito Construct Library

--- | Features | Stability | | --- | --- | | CFN Resources | ![Stable](https://img.shields.io/badge/stable-success.svg?style=for-the-badge) | | Higher level constructs for User Pools | ![Stable](https://img.shields.io/badge/stable-success.svg?style=for-the-badge) | | Higher level constructs for Identity Pools | ![Not Implemented](https://img.shields.io/badge/not--implemented-black.svg?style=for-the-badge) | > **CFN Resources:** All classes with the `Cfn` prefix in this module ([CFN Resources](https://docs.aws.amazon.com/cdk/latest/guide/constructs.html#constructs_lib)) are always stable and safe to use. > **Stable:** Higher level constructs in this module that are marked stable will not undergo any breaking changes. They will strictly follow the [Semantic Versioning](https://semver.org/) model. ---

Amazon Cognito provides authentication, authorization, and user management for your web and mobile apps. Your users can sign in directly with a user name and password, or through a third party such as Facebook, Amazon, Google or Apple.

The two main components of Amazon Cognito are user pools and identity pools. User pools are user directories that provide sign-up and sign-in options for your app users. Identity pools enable you to grant your users access to other AWS services.

This module is part of the AWS Cloud Development Kit project.

User Pools

User pools allow creating and managing your own directory of users that can sign up and sign in. They enable easy integration with social identity providers such as Facebook, Google, Amazon, Microsoft Active Directory, etc. through SAML.

Using the CDK, a new user pool can be created as part of the stack using the construct’s constructor. You may specify the userPoolName to give your own identifier to the user pool. If not, CloudFormation will generate a name.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    user_pool_name="myawesomeapp-userpool"
)

The default set up for the user pool is configured such that only administrators will be allowed to create users. Features such as Multi-factor authentication (MFAs) and Lambda Triggers are not configured by default.

Sign Up

Users can either be signed up by the app’s administrators or can sign themselves up. Once a user has signed up, their account needs to be confirmed. Cognito provides several ways to sign users up and confirm their accounts. Learn more about user sign up here.

When a user signs up, email and SMS messages are used to verify their account and contact methods. The following code snippet configures a user pool with properties relevant to these verification messages -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    self_sign_up_enabled=True,
    user_verification=UserVerificationConfig(
        email_subject="Verify your email for our awesome app!",
        email_body="Hello {username}, Thanks for signing up to our awesome app! Your verification code is {####}",
        email_style=cognito.VerificationEmailStyle.CODE,
        sms_message="Hello {username}, Thanks for signing up to our awesome app! Your verification code is {####}"
    )
)

By default, self sign up is disabled. Learn more about email and SMS verification messages here.

Besides users signing themselves up, an administrator of any user pool can sign users up. The user then receives an invitation to join the user pool. The following code snippet configures a user pool with properties relevant to the invitation messages -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    user_invitation=UserInvitationConfig(
        email_subject="Invite to join our awesome app!",
        email_body="Hello {username}, you have been invited to join our awesome app! Your temporary password is {####}",
        sms_message="Your temporary password for our awesome app is {####}"
    )
)

All email subjects, bodies and SMS messages for both invitation and verification support Cognito’s message templating. Learn more about message templates here.

Sign In

Users registering or signing in into your application can do so with multiple identifiers. There are 4 options available:

  • username: Allow signing in using the one time immutable user name that the user chose at the time of sign up.

  • email: Allow signing in using the email address that is associated with the account.

  • phone: Allow signing in using the phone number that is associated with the account.

  • preferredUsername: Allow signing in with an alternate user name that the user can change at any time. However, this is not available if the username option is not chosen.

The following code sets up a user pool so that the user can sign in with either their username or their email address -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    # ...
    sign_in_aliases=SignInAliases(
        username=True,
        email=True
    )
)

User pools can either be configured so that user name is primary sign in form, but also allows for the other three to be used additionally; or it can be configured so that email and/or phone numbers are the only ways a user can register and sign in. Read more about this here.

⚠️ The Cognito service prevents changing the signInAlias property for an existing user pool.

To match with ‘Option 1’ in the above link, with a verified email, signInAliases should be set to { username: true, email: true }. To match with ‘Option 2’ in the above link with both a verified email and phone number, this property should be set to { email: true, phone: true }.

Cognito recommends that email and phone number be automatically verified, if they are one of the sign in methods for the user pool. Read more about that here. The CDK does this by default, when email and/or phone number are specified as part of signInAliases. This can be overridden by specifying the autoVerify property.

The following code snippet sets up only email as a sign in alias, but both email and phone number to be auto-verified.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    # ...
    sign_in_aliases=SignInAliases(username=True, email=True),
    auto_verify=AutoVerifiedAttrs(email=True, phone=True)
)

A user pool can optionally ignore case when evaluating sign-ins. When signInCaseSensitive is false, Cognito will not check the capitalization of the alias when signing in. Default is true.

Attributes

Attributes represent the various properties of each user that’s collected and stored in the user pool. Cognito provides a set of standard attributes that are available for all user pools. Users are allowed to select any of these standard attributes to be required. Users will not be able to sign up to the user pool without providing the required attributes. Besides these, additional attributes can be further defined, and are known as custom attributes.

Learn more on attributes in Cognito’s documentation.

The following code configures a user pool with two standard attributes (name and address) as required and mutable, and adds four custom attributes.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    standard_attributes=StandardAttributes(
        fullname=StandardAttribute(
            required=True,
            mutable=False
        ),
        address=StandardAttribute(
            required=False,
            mutable=True
        )
    ),
    custom_attributes={
        "myappid": cognito.StringAttribute(min_len=5, max_len=15, mutable=False),
        "callingcode": cognito.NumberAttribute(min=1, max=3, mutable=True),
        "is_employee": cognito.BooleanAttribute(mutable=True),
        "joined_on": cognito.DateTimeAttribute()
    }
)

As shown in the code snippet, there are data types that are available for custom attributes. The ‘String’ and ‘Number’ data types allow for further constraints on their length and values, respectively.

Custom attributes cannot be marked as required.

All custom attributes share the property mutable that specifies whether the value of the attribute can be changed. The default value is false.

Security

Cognito sends various messages to its users via SMS, for different actions, ranging from account verification to marketing. In order to send SMS messages, Cognito needs an IAM role that it can assume, with permissions that allow it to send SMS messages.

By default, the CDK looks at all of the specified properties (and their defaults when not explicitly specified) and automatically creates an SMS role, when needed. For example, if MFA second factor by SMS is enabled, the CDK will create a new role. The smsRole property can be used to specify the user supplied role that should be used instead. Additionally, the property enableSmsRole can be used to override the CDK’s default behaviour to either enable or suppress automatic role creation.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
pool_sms_role = iam.Role(self, "userpoolsmsrole",
    assumed_by=iam.ServicePrincipal("foo")
)

cognito.UserPool(self, "myuserpool",
    # ...
    sms_role=pool_sms_role,
    sms_role_external_id="c87467be-4f34-11ea-b77f-2e728ce88125"
)

When the smsRole property is specified, the smsRoleExternalId may also be specified. The value of smsRoleExternalId will be used as the sts:ExternalId when the Cognito service assumes the role. In turn, the role’s assume role policy should be configured to accept this value as the ExternalId. Learn more about ExternalId here.

Multi-factor Authentication (MFA)

User pools can be configured to enable multi-factor authentication (MFA). It can either be turned off, set to optional or made required. Setting MFA to optional means that individual users can choose to enable it. Additionally, the MFA code can be sent either via SMS text message or via a time-based software token. See the documentation on MFA to learn more.

The following code snippet marks MFA for the user pool as required. This means that all users are required to configure an MFA token and use it for sign in. It also allows for the users to use both SMS based MFA, as well, time-based one time password (TOTP).

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    mfa=cognito.Mfa.REQUIRED,
    mfa_second_factor=MfaSecondFactor(
        sms=True,
        otp=True
    )
)

User pools can be configured with policies around a user’s password. This includes the password length and the character sets that they must contain.

Further to this, it can also be configured with the validity of the auto-generated temporary password. A temporary password is generated by the user pool either when an admin signs up a user or when a password reset is requested. The validity of this password dictates how long to give the user to use this password before expiring it.

The following code snippet configures these properties -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    password_policy=PasswordPolicy(
        min_length=12,
        require_lowercase=True,
        require_uppercase=True,
        require_digits=True,
        require_symbols=True,
        temp_password_validity=Duration.days(3)
    )
)

Note that, tempPasswordValidity can be specified only in whole days. Specifying fractional days would throw an error.

Account Recovery Settings

User pools can be configured on which method a user should use when recovering the password for their account. This can either be email and/or SMS. Read more at Recovering User Accounts

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "UserPool",
    # ...
    account_recovery=cognito.AccountRecovery.EMAIL_ONLY
)

The default for account recovery is by phone if available and by email otherwise. A user will not be allowed to reset their password via phone if they are also using it for MFA.

Emails

Cognito sends emails to users in the user pool, when particular actions take place, such as welcome emails, invitation emails, password resets, etc. The address from which these emails are sent can be configured on the user pool. Read more about email settings here.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
cognito.UserPool(self, "myuserpool",
    # ...
    email_settings=EmailSettings(
        from="noreply@myawesomeapp.com",
        reply_to="support@myawesomeapp.com"
    )
)

By default, user pools are configured to use Cognito’s built-in email capability, but it can also be configured to use Amazon SES, however, support for Amazon SES is not available in the CDK yet. If you would like this to be implemented, give this issue a +1. Until then, you can use the cfn layer to configure this.

Lambda Triggers

User pools can be configured such that AWS Lambda functions can be triggered when certain user operations or actions occur, such as, sign up, user confirmation, sign in, etc. They can also be used to add custom authentication challenges, user migrations and custom verification messages. Learn more about triggers at User Pool Workflows with Triggers.

Lambda triggers can either be specified as part of the UserPool initialization, or it can be added later, via methods on the construct, as so -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
auth_challenge_fn = lambda_.Function(self, "authChallengeFn",
    runtime=lambda_.Runtime.NODEJS_10_X,
    handler="index.handler",
    code=lambda_.Code.from_inline("auth challenge")
)

userpool = cognito.UserPool(self, "myuserpool",
    # ...
    lambda_triggers=UserPoolTriggers(
        create_auth_challenge=auth_challenge_fn
    )
)

userpool.add_trigger(cognito.UserPoolOperation.USER_MIGRATION, lambda_.Function(self, "userMigrationFn",
    runtime=lambda_.Runtime.NODEJS_10_X,
    handler="index.handler",
    code=lambda_.Code.from_inline("user migration")
))

The following table lists the set of triggers available, and their corresponding method to add it to the user pool. For more information on the function of these triggers and how to configure them, read User Pool Workflows with Triggers.

Trigger Permissions

The function.attachToRolePolicy() API can be used to add additional IAM permissions to the lambda trigger as necessary.

⚠️ Using the attachToRolePolicy API to provide permissions to your user pool will result in a circular dependency. See aws/aws-cdk#7016. Error message when running cdk synth or cdk deploy:

Circular dependency between resources: [pool056F3F7E, fnPostAuthFnCognitoA630A2B1, …]

To work around the circular dependency issue, use the attachInlinePolicy() API instead, as shown below.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
# provide permissions to describe the user pool scoped to the ARN the user pool
post_auth_fn.role.attach_inline_policy(iam.Policy(self, "userpool-policy",
    statements=[iam.PolicyStatement(
        actions=["cognito-idp:DescribeUserPool"],
        resources=[userpool.user_pool_arn]
    )]
))

Importing User Pools

Any user pool that has been created outside of this stack, can be imported into the CDK app. Importing a user pool allows for it to be used in other parts of the CDK app that reference an IUserPool. However, imported user pools have limited configurability. As a rule of thumb, none of the properties that are part of the ``AWS::Cognito::UserPool` <https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-cognito-userpool.html>`_ CloudFormation resource can be configured.

User pools can be imported either using their id via the UserPool.fromUserPoolId(), or by using their ARN, via the UserPool.fromUserPoolArn() API.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
awesome_pool = cognito.UserPool.from_user_pool_id(self, "awesome-user-pool", "us-east-1_oiuR12Abd")

other_awesome_pool = cognito.UserPool.from_user_pool_arn(self, "other-awesome-user-pool", "arn:aws:cognito-idp:eu-west-1:123456789012:userpool/us-east-1_mtRyYQ14D")

Identity Providers

Users that are part of a user pool can sign in either directly through a user pool, or federate through a third-party identity provider. Once configured, the Cognito backend will take care of integrating with the third-party provider. Read more about Adding User Pool Sign-in Through a Third Party.

The following third-party identity providers are currently supported in the CDK -

The following code configures a user pool to federate with the third party provider, ‘Login with Amazon’. The identity provider needs to be configured with a set of credentials that the Cognito backend can use to federate with the third-party identity provider.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
userpool = cognito.UserPool(self, "Pool")

provider = cognito.UserPoolIdentityProviderAmazon(self, "Amazon",
    client_id="amzn-client-id",
    client_secret="amzn-client-secret",
    user_pool=userpool
)

Attribute mapping allows mapping attributes provided by the third-party identity providers to standard and custom attributes of the user pool. Learn more about Specifying Identity Provider Attribute Mappings for Your User Pool.

The following code shows how different attributes provided by ‘Login With Amazon’ can be mapped to standard and custom user pool attributes.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
userpool = cognito.UserPool(self, "Pool")

cognito.UserPoolIdentityProviderAmazon(self, "Amazon",
    client_id="amzn-client-id",
    client_secret="amzn-client-secret",
    user_pool=userpool,
    attribute_mapping=AttributeMapping(
        email=cognito.ProviderAttribute.AMAZON_EMAIL,
        website=cognito.ProviderAttribute.other("url"), # use other() when an attribute is not pre-defined in the CDK
        custom={
            # custom user pool attributes go here
            "unique_id": cognito.ProviderAttribute.AMAZON_USER_ID
        }
    )
)

App Clients

An app is an entity within a user pool that has permission to call unauthenticated APIs (APIs that do not have an authenticated user), such as APIs to register, sign in, and handle forgotten passwords. To call these APIs, you need an app client ID and an optional client secret. Read Configuring a User Pool App Client to learn more.

The following code creates an app client and retrieves the client id -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
pool = cognito.UserPool(self, "pool")
client = pool.add_client("customer-app-client")
client_id = client.user_pool_client_id

Existing app clients can be imported into the CDK app using the UserPoolClient.fromUserPoolClientId() API. For new and imported user pools, clients can also be created via the UserPoolClient constructor, as so -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
imported_pool = cognito.UserPool.from_user_pool_id(self, "imported-pool", "us-east-1_oiuR12Abd")
cognito.UserPoolClient(self, "customer-app-client",
    user_pool=imported_pool
)

Clients can be configured with authentication flows. Authentication flows allow users on a client to be authenticated with a user pool. Cognito user pools provide several several different types of authentication, such as, SRP (Secure Remote Password) authentication, username-and-password authentication, etc. Learn more about this at UserPool Authentication Flow.

The following code configures a client to use both SRP and username-and-password authentication -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
pool = cognito.UserPool(self, "pool")
pool.add_client("app-client",
    auth_flows=AuthFlow(
        user_password=True,
        user_srp=True
    )
)

Custom authentication protocols can be configured by setting the custom property under authFlow and defining lambda functions for the corresponding user pool triggers. Learn more at Custom Authentication Flow.

In addition to these authentication mechanisms, Cognito user pools also support using OAuth 2.0 framework for authenticating users. User pool clients can be configured with OAuth 2.0 authorization flows and scopes. Learn more about the OAuth 2.0 authorization framework and Cognito user pool’s implementation of OAuth2.0.

The following code configures an app client with the authorization code grant flow and registers the the app’s welcome page as a callback (or redirect) URL. It also configures the access token scope to ‘openid’. All of these concepts can be found in the OAuth 2.0 RFC.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
pool = cognito.UserPool(self, "Pool")
pool.add_client("app-client",
    o_auth=OAuthSettings(
        flows=OAuthFlows(
            authorization_code_grant=True
        ),
        scopes=[cognito.OAuthScope.OPENID],
        callback_urls=["https://my-app-domain.com/welcome"],
        logout_urls=["https://my-app-domain.com/signin"]
    )
)

An app client can be configured to prevent user existence errors. This instructs the Cognito authentication API to return generic authentication failure responses instead of an UserNotFoundException. By default, the flag is not set, which means different things for existing and new stacks. See the documentation for the full details on the behavior of this flag.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
pool = cognito.UserPool(self, "Pool")
pool.add_client("app-client",
    prevent_user_existence_errors=True
)

All identity providers created in the CDK app are automatically registered into the corresponding user pool. All app clients created in the CDK have all of the identity providers enabled by default. The ‘Cognito’ identity provider, that allows users to register and sign in directly with the Cognito user pool, is also enabled by default. Alternatively, the list of supported identity providers for a client can be explicitly specified -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
pool = cognito.UserPool(self, "Pool")
pool.add_client("app-client",
    # ...
    supported_identity_providers=[cognito.UserPoolClientIdentityProvider.AMAZON, cognito.UserPoolClientIdentityProvider.COGNITO
    ]
)

Domains

After setting up an app client, the address for the user pool’s sign-up and sign-in webpages can be configured using domains. There are two ways to set up a domain - either the Amazon Cognito hosted domain can be chosen with an available domain prefix, or a custom domain name can be chosen. The custom domain must be one that is already owned, and whose certificate is registered in AWS Certificate Manager.

The following code sets up a user pool domain in Amazon Cognito hosted domain with the prefix ‘my-awesome-app’, and another domain with the custom domain ‘user.myapp.com’ -

# Example automatically generated. See https://github.com/aws/jsii/issues/826
pool = cognito.UserPool(self, "Pool")

pool.add_domain("CognitoDomain",
    cognito_domain=CognitoDomainOptions(
        domain_prefix="my-awesome-app"
    )
)

certificate_arn = "arn:aws:acm:us-east-1:123456789012:certificate/11-3336f1-44483d-adc7-9cd375c5169d"

domain_cert = certificatemanager.Certificate.from_certificate_arn(self, "domainCert", certificate_arn)
pool.add_domain("CustomDomain",
    custom_domain=CustomDomainOptions(
        domain_name="user.myapp.com",
        certificate=domain_cert
    )
)

Read more about Using the Amazon Cognito Domain and Using Your Own Domain.

The signInUrl() methods returns the fully qualified URL to the login page for the user pool. This page comes from the hosted UI configured with Cognito. Learn more at Hosted UI with the Amazon Cognito Console.

# Example automatically generated. See https://github.com/aws/jsii/issues/826
userpool = cognito.UserPool(self, "UserPool")
client = userpool.add_client("Client",
    # ...
    o_auth=OAuthSettings(
        flows=OAuthFlows(
            implicit_code_grant=True
        ),
        callback_urls=["https://myapp.com/home", "https://myapp.com/users"
        ]
    )
)
domain = userpool.add_domain("Domain")
sign_in_url = domain.sign_in_url(client,
    redirect_uri="https://myapp.com/home"
)

Existing domains can be imported into CDK apps using UserPoolDomain.fromDomainName() API

# Example automatically generated. See https://github.com/aws/jsii/issues/826
my_user_pool_domain = cognito.UserPoolDomain.from_domain_name(self, "my-user-pool-domain", "domain-name")