initiateAuth method

Future<InitiateAuthResponse> initiateAuth({ required AuthFlowType authFlow, required String clientId, AnalyticsMetadataType? analyticsMetadata, Map<String, String>? authParameters, Map<String, String>? clientMetadata, UserContextDataType? userContextData, })

Initiates the authentication flow.

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

Parameter authFlow : The authentication flow for this call to execute. The API action will depend on this value. For example:

• REFRESH_TOKEN_AUTH will take in a valid refresh token and return new tokens.
• USER_SRP_AUTH will take in USERNAME and SRP_A and return the SRP variables to be used for next challenge execution.
• USER_PASSWORD_AUTH will take in USERNAME and PASSWORD and return the next challenge or tokens.

Valid values include:

• USER_SRP_AUTH: Authentication flow for the Secure Remote Password (SRP) protocol.
• REFRESH_TOKEN_AUTH/REFRESH_TOKEN: Authentication flow for refreshing the access token and ID token by supplying a valid refresh token.
• CUSTOM_AUTH: Custom authentication flow.
• USER_PASSWORD_AUTH: Non-SRP authentication flow; USERNAME and PASSWORD are passed directly. If a user migration Lambda trigger is set, this flow will invoke the user migration Lambda if the USERNAME is not found in the user pool.
• ADMIN_USER_PASSWORD_AUTH: Admin-based user password authentication. This replaces the ADMIN_NO_SRP_AUTH authentication flow. In this flow, Cognito receives the password in the request instead of using the SRP process to verify passwords.

ADMIN_NO_SRP_AUTH is not a valid value.

Parameter clientId : The app client ID.

Parameter analyticsMetadata : The Amazon Pinpoint analytics metadata for collecting metrics for InitiateAuth calls.

Parameter authParameters : The authentication parameters. These are inputs corresponding to the AuthFlow that you are invoking. The required values depend on the value of AuthFlow:

• For USER_SRP_AUTH: USERNAME (required), SRP_A (required), SECRET_HASH (required if the app client is configured with a client secret), DEVICE_KEY.
• For REFRESH_TOKEN_AUTH/REFRESH_TOKEN: REFRESH_TOKEN (required), SECRET_HASH (required if the app client is configured with a client secret), DEVICE_KEY.
• For CUSTOM_AUTH: USERNAME (required), SECRET_HASH (if app client is configured with client secret), DEVICE_KEY. To start the authentication flow with password verification, include ChallengeName: SRP_A and SRP_A: (The SRP_A Value).

Parameter clientMetadata : A map of custom key-value pairs that you can provide as input for certain custom workflows that this action triggers.

You create custom workflows by assigning AWS Lambda functions to user pool triggers. When you use the InitiateAuth API action, Amazon Cognito invokes the AWS Lambda functions that are specified for various triggers. The ClientMetadata value is passed as input to the functions for only the following triggers:

• Pre signup
• Pre authentication
• User migration

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

When you use the InitiateAuth API action, Amazon Cognito also invokes the functions for the following triggers, but it does not provide the ClientMetadata value as input:

• Post authentication
• Custom message
• Pre token generation
• Create auth challenge
• Define auth challenge
• Verify auth challenge

For more information, see Customizing User Pool Workflows with Lambda Triggers in the Amazon Cognito Developer Guide.

Parameter userContextData : Contextual data such as the user's device fingerprint, IP address, or location used for evaluating the risk of an unexpected event by Amazon Cognito advanced security.

Implementation

Future<InitiateAuthResponse> initiateAuth({
  required AuthFlowType authFlow,
  required String clientId,
  AnalyticsMetadataType? analyticsMetadata,
  Map<String, String>? authParameters,
  Map<String, String>? clientMetadata,
  UserContextDataType? userContextData,
}) async {
  ArgumentError.checkNotNull(authFlow, 'authFlow');
  ArgumentError.checkNotNull(clientId, 'clientId');
  _s.validateStringLength(
    'clientId',
    clientId,
    1,
    128,
    isRequired: true,
  );
  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.toValue(),
      'ClientId': clientId,
      if (analyticsMetadata != null) 'AnalyticsMetadata': analyticsMetadata,
      if (authParameters != null) 'AuthParameters': authParameters,
      if (clientMetadata != null) 'ClientMetadata': clientMetadata,
      if (userContextData != null) 'UserContextData': userContextData,
    },
  );

  return InitiateAuthResponse.fromJson(jsonResponse.body);
}