initiateAuth method

Declares an authentication flow and initiates sign-in for a user in the Amazon Cognito user directory. Amazon Cognito might respond with an additional challenge or an AuthenticationResult that contains the outcome of a successful authentication. You can't sign in a user with a federated IdP with InitiateAuth. For more information, see Authentication.

If you have never used SMS text messages with Amazon Cognito or any other Amazon Web Services service, Amazon Simple Notification Service might place your account in the SMS sandbox. In sandbox mode , you can send messages only to verified phone numbers. After you test your app while in the sandbox environment, you can move out of the sandbox and into production. For more information, see SMS message settings for Amazon Cognito user pools in the Amazon Cognito Developer Guide.

May throw ForbiddenException. May throw InternalErrorException. May throw InvalidEmailRoleAccessPolicyException. May throw InvalidLambdaResponseException. May throw InvalidParameterException. May throw InvalidSmsRoleAccessPolicyException. May throw InvalidSmsRoleTrustRelationshipException. May throw InvalidUserPoolConfigurationException. May throw NotAuthorizedException. May throw OperationNotEnabledException. May throw PasswordResetRequiredException. May throw ResourceNotFoundException. May throw TooManyRequestsException. May throw UnexpectedLambdaException. May throw UnsupportedOperationException. May throw UserLambdaValidationException. May throw UserNotConfirmedException. May throw UserNotFoundException.

Parameter authFlow : The authentication flow that you want to initiate. Each AuthFlow has linked AuthParameters that you must submit. The following are some example flows.

USER_AUTH

The entry point for choice-based authentication with passwords, one-time passwords, and WebAuthn authenticators. Request a preferred authentication type or review available authentication types. From the offered authentication types, select one in a challenge response and then authenticate with that method in an additional challenge response. To activate this setting, your user pool must be in the Essentials tier or higher.

USER_SRP_AUTH

Username-password authentication with the Secure Remote Password (SRP) protocol. For more information, see Use SRP password verification in custom authentication flow.

REFRESH_TOKEN_AUTH and REFRESH_TOKEN

Receive new ID and access tokens when you pass a REFRESH_TOKEN parameter with a valid refresh token as the value. For more information, see Using the refresh token.

CUSTOM_AUTH

Custom authentication with Lambda triggers. For more information, see Custom authentication challenge Lambda triggers.

USER_PASSWORD_AUTH

Client-side username-password authentication with the password sent directly in the request. For more information about client-side and server-side authentication, see SDK authorization models.

ADMIN_USER_PASSWORD_AUTH is a flow type of AdminInitiateAuth and isn't valid for InitiateAuth. ADMIN_NO_SRP_AUTH is a legacy server-side username-password flow and isn't valid for InitiateAuth.

Parameter clientId : The ID of the app client that your user wants to sign in to.

Parameter analyticsMetadata : Information that supports analytics outcomes with Amazon Pinpoint, including the user's endpoint ID. The endpoint ID is a destination for Amazon Pinpoint push notifications, for example a device identifier, email address, or phone number.

Parameter authParameters : The authentication parameters. These are inputs corresponding to the AuthFlow that you're invoking.

The following are some authentication flows and their parameters. Add a SECRET_HASH parameter if your app client has a client secret. Add DEVICE_KEY if you want to bypass multi-factor authentication with a remembered device.

USER_AUTH

• USERNAME (required)
• PREFERRED_CHALLENGE. If you don't provide a value for PREFERRED_CHALLENGE, Amazon Cognito responds with the AvailableChallenges parameter that specifies the available sign-in methods.

USER_SRP_AUTH

• USERNAME (required)
• SRP_A (required)

USER_PASSWORD_AUTH

• USERNAME (required)
• PASSWORD (required)

REFRESH_TOKEN_AUTH/REFRESH_TOKEN

• REFRESH_TOKEN(required)

CUSTOM_AUTH

• USERNAME (required)
• ChallengeName: SRP_A (when doing SRP authentication before custom challenges)
• SRP_A: (An SRP_A value) (when doing SRP authentication before custom challenges)

For more information about SECRET_HASH, see Computing secret hash values. For information about DEVICE_KEY, see Working with user devices in your user pool.

Parameter clientMetadata : A map of custom key-value pairs that you can provide as input for any custom workflows that this action triggers. You create custom workflows by assigning Lambda functions to user pool triggers.

When Amazon Cognito invokes any of these functions, it passes a JSON payload, which the function receives as input. This payload contains a clientMetadata attribute that provides the data that you assigned to the ClientMetadata parameter in your request. In your function code, you can process the clientMetadata value to enhance your workflow for your specific needs.

To review the Lambda trigger types that Amazon Cognito invokes at runtime with API requests, see Connecting API actions to Lambda triggers in the Amazon Cognito Developer Guide.

The ClientMetadata value is passed as input to the functions for only the following triggers:

• Pre signup
• Pre authentication
• User migration

This request also invokes the functions for the following triggers, but doesn't pass ClientMetadata:

• Post authentication
• Custom message
• Pre token generation
• Create auth challenge
• Define auth challenge
• Custom email sender
• Custom SMS sender

Parameter session : The optional session ID from a ConfirmSignUp API request. You can sign in a user directly from the sign-up process with the USER_AUTH authentication flow. When you pass the session ID to InitiateAuth, Amazon Cognito assumes the SMS or email message one-time verification password from ConfirmSignUp as the primary authentication factor. You're not required to submit this code a second time. This option is only valid for users who have confirmed their sign-up and are signing in for the first time within the authentication flow session duration of the session ID.

Parameter userContextData : Contextual data about your user session like the device fingerprint, IP address, or location. Amazon Cognito threat protection evaluates the risk of an authentication event based on the context that your app generates and passes to Amazon Cognito when it makes API requests.

For more information, see Collecting data for threat protection in applications.

Future<InitiateAuthResponse> initiateAuth({
  required AuthFlowType authFlow,
  required String clientId,
  AnalyticsMetadataType? analyticsMetadata,
  Map<String, String>? authParameters,
  Map<String, String>? clientMetadata,
  String? session,
  UserContextDataType? userContextData,
}) async {
  final headers = <String, String>{
    'Content-Type': 'application/x-amz-json-1.1',
    'X-Amz-Target': 'AWSCognitoIdentityProviderService.InitiateAuth'
  };
  final jsonResponse = await _protocol.send(
    method: 'POST',
    requestUri: '/',
    exceptionFnMap: _exceptionFns,
    signed: false,
    // TODO queryParams
    headers: headers,
    payload: {
      'AuthFlow': authFlow.value,
      'ClientId': clientId,
      if (analyticsMetadata != null) 'AnalyticsMetadata': analyticsMetadata,
      if (authParameters != null) 'AuthParameters': authParameters,
      if (clientMetadata != null) 'ClientMetadata': clientMetadata,
      if (session != null) 'Session': session,
      if (userContextData != null) 'UserContextData': userContextData,
    },
  );

  return InitiateAuthResponse.fromJson(jsonResponse.body);
}