InitiateAuth - Amazon Cognito User Pools
Request SyntaxRequest ParametersResponse SyntaxResponse ElementsErrorsExamplesSee Also

InitiateAuth

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.

Note

Amazon Cognito doesn't evaluate AWS Identity and Access Management (IAM) policies in requests for this API operation. For this operation, you can't use IAM credentials to authorize requests, and you can't grant IAM permissions in policies. For more information about authorization models in Amazon Cognito, see Using the Amazon Cognito user pools API and user pool endpoints.

Note

This action might generate an SMS text message. Starting June 1, 2021, US telecom carriers require you to register an origination phone number before you can send SMS messages to US phone numbers. If you use SMS text messages in Amazon Cognito, you must register a phone number with Amazon Pinpoint. Amazon Cognito uses the registered number automatically. Otherwise, Amazon Cognito users who must receive SMS messages might not be able to sign up, activate their accounts, or sign in.

If you have never used SMS text messages with Amazon Cognito or any other AWS 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.

Request Syntax

{
   "AnalyticsMetadata": { 
      "AnalyticsEndpointId": "string"
   },
   "AuthFlow": "string",
   "AuthParameters": { 
      "string" : "string" 
   },
   "ClientId": "string",
   "ClientMetadata": { 
      "string" : "string" 
   },
   "Session": "string",
   "UserContextData": { 
      "EncodedData": "string",
      "IpAddress": "string"
   }
}

Request Parameters

For information about the parameters that are common to all actions, see Common Parameters.

The request accepts the following data in JSON format.

AnalyticsMetadata

The Amazon Pinpoint analytics metadata that contributes to your metrics for InitiateAuth calls.

Type: AnalyticsMetadataType object

Required: No

AuthFlow

The authentication flow that you want to initiate. Each AuthFlow has linked AuthParameters that you must submit. The following are some example flows and their parameters.

  • USER_AUTH: 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.

  • REFRESH_TOKEN_AUTH: Receive new ID and access tokens when you pass a REFRESH_TOKEN parameter with a valid refresh token as the value.

  • USER_SRP_AUTH: Receive secure remote password (SRP) variables for the next challenge, PASSWORD_VERIFIER, when you pass USERNAME and SRP_A parameters.

  • USER_PASSWORD_AUTH: Receive new tokens or the next challenge, for example SOFTWARE_TOKEN_MFA, when you pass USERNAME and PASSWORD parameters.

All flows

USER_AUTH

The entry point for choice-based authentication with passwords, one-time passwords, and WebAuthn authenticators. 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

Provide a valid refresh token and receive new ID and access tokens. 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

Username-password authentication with the password sent directly in the request. For more information, see Admin authentication flow.

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.

Type: String

Valid Values: USER_SRP_AUTH | REFRESH_TOKEN_AUTH | REFRESH_TOKEN | CUSTOM_AUTH | ADMIN_NO_SRP_AUTH | USER_PASSWORD_AUTH | ADMIN_USER_PASSWORD_AUTH | USER_AUTH

Required: Yes

AuthParameters

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

  • For 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.

  • 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 USER_PASSWORD_AUTH: USERNAME (required), PASSWORD (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).

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.

Type: String to string map

Key Length Constraints: Minimum length of 0. Maximum length of 131072.

Value Length Constraints: Minimum length of 0. Maximum length of 131072.

Required: No

ClientId

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

Type: String

Length Constraints: Minimum length of 1. Maximum length of 128.

Pattern: [\w+]+

Required: Yes

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 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 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 doesn't provide the ClientMetadata value as input:

  • Post authentication

  • Custom message

  • Pre token generation

  • Create auth challenge

  • Define auth challenge

  • Custom email sender

  • Custom SMS sender

For more information, see Using Lambda triggers in the Amazon Cognito Developer Guide.

Note

When you use the ClientMetadata parameter, note that Amazon Cognito won't do the following:

  • Store the ClientMetadata value. This data is available only to AWS Lambda triggers that are assigned to a user pool to support custom workflows. If your user pool configuration doesn't include triggers, the ClientMetadata parameter serves no purpose.

  • Validate the ClientMetadata value.

  • Encrypt the ClientMetadata value. Don't send sensitive information in this parameter.

Type: String to string map

Key Length Constraints: Minimum length of 0. Maximum length of 131072.

Value Length Constraints: Minimum length of 0. Maximum length of 131072.

Required: No

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.

Type: String

Length Constraints: Minimum length of 20. Maximum length of 2048.

Required: No

UserContextData

Contextual data about your user session, such as the device fingerprint, IP address, or location. Amazon Cognito advanced security 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.

Type: UserContextDataType object

Required: No

Response Syntax

{
   "AuthenticationResult": { 
      "AccessToken": "string",
      "ExpiresIn": number,
      "IdToken": "string",
      "NewDeviceMetadata": { 
         "DeviceGroupKey": "string",
         "DeviceKey": "string"
      },
      "RefreshToken": "string",
      "TokenType": "string"
   },
   "AvailableChallenges": [ "string" ],
   "ChallengeName": "string",
   "ChallengeParameters": { 
      "string" : "string" 
   },
   "Session": "string"
}

Response Elements

If the action is successful, the service sends back an HTTP 200 response.

The following data is returned in JSON format by the service.

AuthenticationResult

The result of a successful and complete authentication request. This result is only returned if the user doesn't need to pass another challenge. If they must pass another challenge before they get tokens, Amazon Cognito returns a challenge in ChallengeName, ChallengeParameters, and Session response parameters.

Type: AuthenticationResultType object

AvailableChallenges

This response parameter prompts a user to select one of the available authentication challenges in choice-based authentication. For example, they might be able to continue with passwordless authentication or with a one-time password from an SMS message.

Type: Array of strings

Valid Values: SMS_MFA | EMAIL_OTP | SOFTWARE_TOKEN_MFA | SELECT_MFA_TYPE | MFA_SETUP | PASSWORD_VERIFIER | CUSTOM_CHALLENGE | SELECT_CHALLENGE | DEVICE_SRP_AUTH | DEVICE_PASSWORD_VERIFIER | ADMIN_NO_SRP_AUTH | NEW_PASSWORD_REQUIRED | SMS_OTP | PASSWORD | WEB_AUTHN | PASSWORD_SRP

ChallengeName

The name of an additional authentication challenge that you must respond to. Collect the challenge response from the user and submit it in a RespondToAuthChallenge request. To link this response to the new request, include the Session response parameter in the next request.

Valid values include the following:

Note

All of the following challenges require USERNAME and, when the app client has a client secret, SECRET_HASH in the parameters.

  • WEB_AUTHN: Respond to the challenge with the results of a successful authentication with a passkey, or webauthN, factor. These are typically biometric devices or security keys.

  • PASSWORD: Respond with USER_PASSWORD_AUTH parameters: USERNAME (required), PASSWORD (required), SECRET_HASH (required if the app client is configured with a client secret), DEVICE_KEY.

  • PASSWORD_SRP: Respond with USER_SRP_AUTH parameters: USERNAME (required), SRP_A (required), SECRET_HASH (required if the app client is configured with a client secret), DEVICE_KEY.

  • SELECT_CHALLENGE: Respond to the challenge with USERNAME and an ANSWER that matches one of the challenge types in the AvailableChallenges response parameter.

  • SMS_MFA: Next challenge is to supply an SMS_MFA_CODEthat your user pool delivered in an SMS message.

  • EMAIL_OTP: Next challenge is to supply an EMAIL_OTP_CODE that your user pool delivered in an email message.

  • PASSWORD_VERIFIER: Next challenge is to supply PASSWORD_CLAIM_SIGNATURE, PASSWORD_CLAIM_SECRET_BLOCK, and TIMESTAMP after the client-side SRP calculations.

  • CUSTOM_CHALLENGE: This is returned if your custom authentication flow determines that the user should pass another challenge before tokens are issued.

  • DEVICE_SRP_AUTH: If device tracking was activated on your user pool and the previous challenges were passed, this challenge is returned so that Amazon Cognito can start tracking this device.

  • DEVICE_PASSWORD_VERIFIER: Similar to PASSWORD_VERIFIER, but for devices only.

  • NEW_PASSWORD_REQUIRED: For users who are required to change their passwords after successful first login.

    Respond to this challenge with NEW_PASSWORD and any required attributes that Amazon Cognito returned in the requiredAttributes parameter. You can also set values for attributes that aren't required by your user pool and that your app client can write. For more information, see RespondToAuthChallenge.

    Amazon Cognito only returns this challenge for users who have temporary passwords. Because of this, and because in some cases you can create users who don't have values for required attributes, take care to collect and submit required-attribute values for all users who don't have passwords. You can create a user in the Amazon Cognito console without, for example, a required birthdate attribute. The API response from Amazon Cognito won't prompt you to submit a birthdate for the user if they don't have a password.

    Note

    In a NEW_PASSWORD_REQUIRED challenge response, you can't modify a required attribute that already has a value. In RespondToAuthChallenge, set a value for any keys that Amazon Cognito returned in the requiredAttributes parameter, then use the UpdateUserAttributes API operation to modify the value of any additional attributes.

  • MFA_SETUP: For users who are required to setup an MFA factor before they can sign in. The MFA types activated for the user pool will be listed in the challenge parameters MFAS_CAN_SETUP value.

    To set up software token MFA, use the session returned here from InitiateAuth as an input to AssociateSoftwareToken. Use the session returned by VerifySoftwareToken as an input to RespondToAuthChallenge with challenge name MFA_SETUP to complete sign-in. To set up SMS MFA, an administrator should help the user to add a phone number to their account, and then the user should call InitiateAuth again to restart sign-in.

Type: String

Valid Values: SMS_MFA | EMAIL_OTP | SOFTWARE_TOKEN_MFA | SELECT_MFA_TYPE | MFA_SETUP | PASSWORD_VERIFIER | CUSTOM_CHALLENGE | SELECT_CHALLENGE | DEVICE_SRP_AUTH | DEVICE_PASSWORD_VERIFIER | ADMIN_NO_SRP_AUTH | NEW_PASSWORD_REQUIRED | SMS_OTP | PASSWORD | WEB_AUTHN | PASSWORD_SRP

ChallengeParameters

The required parameters of the ChallengeName challenge. Collect the challenge response from the user and submit it in a RespondToAuthChallenge request. To link this response to the new request, include the Session response parameter in the next request.

All challenges require USERNAME. They also require SECRET_HASH if your app client has a client secret.

Type: String to string map

Key Length Constraints: Minimum length of 0. Maximum length of 131072.

Value Length Constraints: Minimum length of 0. Maximum length of 131072.

Session

The session identifier that links a challenge response to the initial authentication request. If the user must pass another challenge, Amazon Cognito returns a session ID and challenge parameters. Include this session ID in a RespondToAuthChallenge API request.

Type: String

Length Constraints: Minimum length of 20. Maximum length of 2048.

Errors

For information about the errors that are common to all actions, see Common Errors.

ForbiddenException

This exception is thrown when AWS WAF doesn't allow your request based on a web ACL that's associated with your user pool.

HTTP Status Code: 400

InternalErrorException

This exception is thrown when Amazon Cognito encounters an internal error.

HTTP Status Code: 500

InvalidEmailRoleAccessPolicyException

This exception is thrown when Amazon Cognito isn't allowed to use your email identity. HTTP status code: 400.

HTTP Status Code: 400

InvalidLambdaResponseException

This exception is thrown when Amazon Cognito encounters an invalid AWS Lambda response.

HTTP Status Code: 400

InvalidParameterException

This exception is thrown when the Amazon Cognito service encounters an invalid parameter.

HTTP Status Code: 400

InvalidSmsRoleAccessPolicyException

This exception is returned when the role provided for SMS configuration doesn't have permission to publish using Amazon SNS.

HTTP Status Code: 400

InvalidSmsRoleTrustRelationshipException

This exception is thrown when the trust relationship is not valid for the role provided for SMS configuration. This can happen if you don't trust cognito-idp.amazonaws.com or the external ID provided in the role does not match what is provided in the SMS configuration for the user pool.

HTTP Status Code: 400

InvalidUserPoolConfigurationException

This exception is thrown when the user pool configuration is not valid.

HTTP Status Code: 400

NotAuthorizedException

This exception is thrown when a user isn't authorized.

HTTP Status Code: 400

PasswordResetRequiredException

This exception is thrown when a password reset is required.

HTTP Status Code: 400

ResourceNotFoundException

This exception is thrown when the Amazon Cognito service can't find the requested resource.

HTTP Status Code: 400

TooManyRequestsException

This exception is thrown when the user has made too many requests for a given operation.

HTTP Status Code: 400

UnexpectedLambdaException

This exception is thrown when Amazon Cognito encounters an unexpected exception with AWS Lambda.

HTTP Status Code: 400

UserLambdaValidationException

This exception is thrown when the Amazon Cognito service encounters a user validation exception with the AWS Lambda service.

HTTP Status Code: 400

UserNotConfirmedException

This exception is thrown when a user isn't confirmed successfully.

HTTP Status Code: 400

UserNotFoundException

This exception is thrown when a user isn't found.

HTTP Status Code: 400

Examples

Example

The following example starts the user testuser in the passkey authentication flow. The user pool and app client have password, passkey, and OTP options. User verification is set to preferred for the user pool, so the user isn't required to have a passkey with user-verification support.

Sample Request

POST HTTP/1.1
Host: cognito-idp.us-east-1.amazonaws.com
X-Amz-Date: 20230613T200059Z
Accept-Encoding: gzip, deflate, br
X-Amz-Target: AWSCognitoIdentityProviderService.InitiateAuth
User-Agent: <UserAgentString>
Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=<Headers>, Signature=<Signature>
Content-Length: <PayloadSizeBytes>

{
    "AuthFlow": "USER_AUTH",
    "ClientId": "1example23456789",
    "AuthParameters": {
        "USERNAME": "testuser",
        "PREFERRED_CHALLENGE": "WEB_AUTHN"
    }
}

Sample Response

HTTP/1.1 200 OK
Date: Tue, 13 Jun 2023 20:00:59 GMT
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
x-amzn-requestid: a1b2c3d4-e5f6-a1b2-c3d4-EXAMPLE11111
Connection: keep-alive

{
    "AvailableChallenges": [
        "PASSWORD_SRP",
        "PASSWORD",
        "EMAIL_OTP",
        "WEB_AUTHN"
    ],
    "ChallengeName": "WEB_AUTHN",
    "ChallengeParameters": {
        "CREDENTIAL_REQUEST_OPTIONS": "{\"challenge\":\"[challenge string]\",\"timeout\":180000,\"rpId\":\"auth.example.com\",\"allowCredentials\":[{\"type\":\"public-key\",\"id\":\"[key ID]\",\"transports\":[]},{\"type\":\"public-key\",\"id\":\"[key ID]\",\"transports\":[\"internal\"]}],\"userVerification\":\"preferred\"}"
    },
    "Session": "AYABeC1-y8qooiuysEv0uM4wAqQAHQABAAdTZXJ2aWNlABBDb2duaXRvVXNlclBvb2xzAAEAB2F3cy1rbXMAS2Fybjphd3M6a21zOnVzLXd..."
}

Example

The following example requests sign-in for the user testuser in a user pool where they're eligible for sign in with email OTP.

Sample Request

POST HTTP/1.1
Host: cognito-idp.us-east-1.amazonaws.com
X-Amz-Date: 20230613T200059Z
Accept-Encoding: gzip, deflate, br
X-Amz-Target: AWSCognitoIdentityProviderService.InitiateAuth
User-Agent: <UserAgentString>
Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=<Headers>, Signature=<Signature>
Content-Length: <PayloadSizeBytes>

{
    "AuthFlow": "USER_AUTH",
    "ClientId": "1example23456789",
    "AuthParameters": {
        "USERNAME": "testuser",
        "PREFERRED_CHALLENGE": "EMAIL_OTP"
    }
}

Sample Response

HTTP/1.1 200 OK
Date: Tue, 13 Jun 2023 20:00:59 GMT
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
x-amzn-requestid: a1b2c3d4-e5f6-a1b2-c3d4-EXAMPLE11111
Connection: keep-alive

{
    "AvailableChallenges": [
        "PASSWORD_SRP",
        "PASSWORD",
        "EMAIL_OTP",
        "WEB_AUTHN"
    ],
    "ChallengeName": "EMAIL_OTP",
    "ChallengeParameters": {
        "CODE_DELIVERY_DELIVERY_MEDIUM": "EMAIL",
        "CODE_DELIVERY_DESTINATION": "t***@e***"
    },
    "Session": "AYABeC1-y8qooiuysEv0uM4wAqQAHQABAAdTZXJ2aWNlABBDb2duaXRvVXNlclBvb2xzAAEAB2F3cy1rbXMAS2Fybjphd3M6a21zOnVzLXd..."
}

Example

The following example signs in the user mytestuser with analytics data, client metadata, and user context data for advanced security.

Sample Request

POST / HTTP/1.1
Content-Type: application/x-amz-json-1.1
X-Amz-Target: AWSCognitoIdentityProviderService.InitiateAuth
User-Agent: <UserAgentString>
Accept: */*
Host: cognito-idp.us-east-1.amazonaws.com
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Content-Length: <PayloadSizeBytes>
{
    "AuthFlow": "USER_PASSWORD_AUTH",
    "ClientId": "1example23456789",
    "AuthParameters": {
        "USERNAME": "mytestuser",
        "PASSWORD": "This-is-my-test-99!",
        "SECRET_HASH": "oT5ZkS8ctnrhYeeGsGTvOzPhoc/Jd1cO5fueBWFVmp8="
    },
    "AnalyticsMetadata": {
        "AnalyticsEndpointId": "d70b2ba36a8c4dc5a04a0451a31a1e12"
    },
    "UserContextData": {
        "EncodedData": "AmazonCognitoAdvancedSecurityData_object",
        "IpAddress": "192.0.2.1"
    },
    "ClientMetadata": {
        "MyTestKey": "MyTestValue"
    }
}

Sample Response

HTTP/1.1 200 OK
Date: Tue, 13 Jun 2023 20:00:59 GMT
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
x-amzn-requestid: a1b2c3d4-e5f6-a1b2-c3d4-EXAMPLE11111
Connection: keep-alive

{
    "ChallengeName": "SOFTWARE_TOKEN_MFA",
    "ChallengeParameters": {
        "USER_ID_FOR_SRP": "mytestuser",
        "FRIENDLY_DEVICE_NAME": "mytestauthenticator"
    },
    "Session": "AYABeC1-y8qooiuysEv0uM4wAqQAHQABAAdTZXJ2aWNlABBDb2duaXRvVXNlclBvb2xzAAEAB2F3cy1rbXMAS2Fybjphd3M6a21zOnVzLXd..."
}

Example

The following example exchanges a refresh token for access and ID tokens.

Sample Request

POST / HTTP/1.1
Content-Type: application/x-amz-json-1.1
X-Amz-Target: AWSCognitoIdentityProviderService.InitiateAuth
User-Agent: <UserAgentString>
Accept: */*
Host: cognito-idp.us-east-1.amazonaws.com
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Content-Length: 1964                    
                    
{
    "AuthFlow": "REFRESH_TOKEN",
    "ClientId": "1example23456789",
    "AuthParameters": {
        "REFRESH_TOKEN": "eyJ123abcEXAMPLE",
        "SECRET_HASH": "7P85/EXAMPLE"
    }
}

Sample Response

HTTP/1.1 200 OK
Date: Tue, 13 Jun 2023 20:00:59 GMT
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
x-amzn-requestid: a1b2c3d4-e5f6-a1b2-c3d4-EXAMPLE11111
Connection: keep-alive

{
    "AuthenticationResult": {
        "AccessToken": "eyJra456defEXAMPLE",
        "ExpiresIn": 3600,
        "IdToken": "eyJra789ghiEXAMPLE",
        "TokenType": "Bearer"
    },
    "ChallengeParameters": {}
}

See Also

For more information about using this API in one of the language-specific AWS SDKs, see the following: