Working with user devices in your user pool - Amazon Cognito
Setting up remembered devicesGetting a device keySigning in with a deviceViewing, updating and forgetting devices

Working with user devices in your user pool

When you sign in local user pool users with the Amazon Cognito user pools API, you can associate your users’ activity logs from advanced security features with each of their devices and, optionally, allow your users to skip multi-factor authentication (MFA) if they’re on a trusted device. Amazon Cognito includes a device key in the response to any sign-in that doesn’t already include device information. The device key is in the format Region_UUID. With a device key, a Secure Remote Password (SRP) library, and a user pool that permits device authentication, you can prompt users in your app to trust the current device and no longer prompt for an MFA code at sign-in.

Setting up remembered devices

With Amazon Cognito user pools, you can associate each of your users' devices with a unique device identifier: a device key. When you present the device key and perform device authentication at sign-in, you can take advantage of two features.

  1. With advanced security features, you can monitor user activity on specific devices for security and analytics purposes. When users sign in, your app has the option to authenticate each user and their device, adding device information to your their activity logs.

  2. Remembering devices also supports a trusted device authentication flow, where your users can choose to sign in without MFA for the time period appropriate to the security requirements of your app. When you want to re-prompt your user to submit an MFA code, you can change the remembered status of their device.

    Remembered devices can override MFA only in user pools with MFA active.

When your user signs in with a remembered device, you must perform an additional device authentication during their authentication flow. For more information, see Signing in with a device.

Configure your user pool to remember devices in the Sign-in experience tab of your user pool, under Device tracking. When setting up the remembered devices functionality through the Amazon Cognito console, you have three options: Always, User Opt-In, and No.

Don't remember

Your user pool doesn't prompt users to remember devices when they sign in.

Always remember

When your app confirms a user's device, your user pool always remembers the device and doesn't return MFA challenges on future successful device sign-ins.

User opt-in

When your app confirms a user's device, your user pool doesn't automatically suppress MFA challenges. You must prompt your user to choose whether they want to remember the device.

When you choose Always remember or User Opt-In, Amazon Cognito generates a device-identifier key and secret every time a user signs in from an unidentified device. The device key is the initial identifier that your app sends to your user pool when your user performs device authentication.

With each confirmed user device, whether remembered automatically or opted-in, you can use the device-identifier key and secret to authenticate a device on every user sign-in.

You can also configure remembered-device settings for your user pool in a CreateUserPool or UpdateUserPool API request. For more information, see the DeviceConfiguration property.

The Amazon Cognito user pools API has additional operations for remembered devices.

  1. ListDevices and AdminListDevices return a list of the device keys and their metada for a user.

  2. GetDevice and AdminGetDevice return the device key and metadata for a single device.

  3. UpdateDeviceStatus and AdminUpdateDeviceStatus set a user's device as remembered or not remembered.

  4. ForgetDevice and AdminForgetDevice remove a user's confirmed device from their profile.

API operations with names that begin with Admin are for use in server-side apps and must be authorized with IAM credentials. For more information, see Using the Amazon Cognito user pools API and user pool endpoints.

Getting a device key

Any time that your user signs in with the user pools API and doesn’t include a device key in the authentication parameters as DEVICE_KEY, Amazon Cognito returns a new device key in the response. In your public client-side app, place the device key in app storage so that you can include it in future requests. In your confidential server-side app, set a browser cookie or another client-side token with your user’s device key.

Before your user can sign in with their trusted device, your app must confirm the device key and provide additional information. Generate a ConfirmDevice request to Amazon Cognito that confirms your user’s device with the device key, a friendly name, password verifier, and a salt. If you configured your user pool for opt-in device authentication, Amazon Cognito responds to your ConfirmDevice request with a prompt that your user must choose whether to remember the current device. Respond with your user’s selection in an UpdateDeviceStatus request.

When you confirm your user’s device but don’t set it as remembered, Amazon Cognito stores the association but proceeds with non-device sign-in when you provide the device key. Devices can generate logs that are useful for user security and troubleshooting. A confirmed but unremembered device doesn’t take advantage of the sign-in feature, but does take advantage of the security monitoring logs feature. When you activate advanced security features for your app client and encode a device footprint into your request, Amazon Cognito associates user events with the confirmed device.

To get a new device key

  1. Start your user’s sign-in session with an InitiateAuth API request.

  2. Respond to all authentication challenges with RespondToAuthChallenge until you receive JSON web tokens (JWTs) that mark your user’s sign-in session complete.

  3. In your app, record the values that Amazon Cognito returns in NewDeviceMetadata in its RespondToAuthChallenge or InitiateAuth response: DeviceGroupKey and DeviceKey.

  4. Generate a new SRP secret for your user: a salt and a password verifier. This function is available in SDKs that provide SRP libraries.

  5. Prompt your user for a device name, or generate one from your user’s device characteristics.

  6. Provide your user’s access token, device key, device name, and SRP secret in a ConfirmDevice API request. If your user pool is set to Always remember devices, your user’s registration is complete.

  7. If Amazon Cognito responded to ConfirmDevice with "UserConfirmationNecessary": true, prompt your user to choose if they would like to remember the device. If they affirm that they want to remember the device, generate an UpdateDeviceStatus API request with your user’s access token, device key, and "DeviceRememberedStatus": "remembered".

  8. If you have instructed Amazon Cognito to remember the device, the next time they sign in, instead of an MFA challenge, they’re presented with a DEVICE_SRP_AUTH challenge.

Signing in with a device

After you configure a user’s device to be remembered, Amazon Cognito no longer requires them to submit an MFA code when they sign in with the same device key. Device authentication only replaces the MFA-authentication challenge with a device-authentication challenge. You can’t sign users in with device authentication only. Your user must first complete authentication with their password or a custom challenge. The following is the authentication process for a user on a remembered device.

To perform device authentication in a flow that uses Custom authentication challenge Lambda triggers, pass a DEVICE_KEY parameter in your InitiateAuth API request. After your user succeeds all challenges and the CUSTOM_CHALLENGE challenge returns an issueTokens value of true, Amazon Cognito returns one final DEVICE_SRP_AUTH challenge.

To sign in with a device

  1. Retrieve your user’s device key from client storage.

  2. Start your user’s sign-in session with an InitiateAuth API request. Choose an AuthFlow of USER_SRP_AUTH, REFRESH_TOKEN_AUTH, USER_PASSWORD_AUTH, or CUSTOM_AUTH. In AuthParameters, add your user’s device key to the DEVICE_KEY parameter, and include the other required parameters for your selected sign-in flow.

    1. You can also pass DEVICE_KEY in the parameters of a PASSWORD_VERIFIER response to an authentication challenge.

  3. Complete challenge responses until you receive a DEVICE_SRP_AUTH challenge in the response.

  4. In a RespondToAuthChallenge API request, send a ChallengeName of DEVICE_SRP_AUTH and parameters for USERNAME, DEVICE_KEY, and SRP_A.

  5. Amazon Cognito responds with a DEVICE_PASSWORD_VERIFIER challenge. This challenge response includes values for SECRET_BLOCK and SRP_B.

  6. With your SRP library, generate and submit PASSWORD_CLAIM_SIGNATURE, PASSWORD_CLAIM_SECRET_BLOCK, TIMESTAMP, USERNAME, and DEVICE_KEY parameters. Submit these in an additional RespondToAuthChallenge request.

  7. Complete additional challenges until you receive the user’s JWTs.

The following pseudocode demonstrates how to calculate values for your DEVICE_PASSWORD_VERIFIER challenge response.

PASSWORD_CLAIM_SECRET_BLOCK = SECRET_BLOCK
TIMESTAMP = Tue Sep 25 00:09:40 UTC 2018
PASSWORD_CLAIM_SIGNATURE = Base64(SHA256_HMAC(K_USER, DeviceGroupKey + DeviceKey + PASSWORD_CLAIM_SECRET_BLOCK + TIMESTAMP))
K_USER = SHA256_HASH(S_USER)
S_USER = (SRP_B - k * gx)(a + ux)
x = SHA256_HASH(salt + FULL_PASSWORD)
u = SHA256_HASH(SRP_A + SRP_B)
k = SHA256_HASH(N + g)

Viewing, updating and forgetting devices

You can implement the following features in your app with the Amazon Cognito API.

  1. Display information about a user’s current device.

  2. Display a list of all of your user’s devices.

  3. Forget a device.

  4. Update a device remembered state.

The access tokens that authorize the API requests in the following descriptions must include the aws.cognito.signin.user.admin scope. Amazon Cognito adds a claim for this scope to all access tokens that you generate with the Amazon Cognito user pools API. Third-party IdPs must separately manage devices and MFA for their users who authenticate to Amazon Cognito. In the hosted UI, you can request the aws.cognito.signin.user.admin scope, but the hosted UI automatically adds device information to advanced security user logs, and doesn't offer to remember devices.

Display information about a device

You can query information about a user’s device to determine if it is still in current use. For example, you might want to deactivate remembered devices after they haven’t signed in for 90 days.

  • To display your user’s device information in a public-client app, submit your user’s access key and device key in a GetDevice API request.

  • To display your user’s device information in a confidential-client app, sign an AdminGetDevice API request with AWS credentials and submit your user’s username, device key, and user pool.

Display a list of all your user’s devices

You can display a list of all your user’s devices and their properties. For example, you might want to verify that the current device matches a remembered device.

  • In a public-client app, submit your user’s access token in a ListDevices API request.

  • In a confidential-client app, sign an AdminListDevices API request with AWS credentials and submit your user’s username and user pool.

Forget a device

You can delete a user’s device key. You might want to do this when you determine that your user no longer uses a device, or when you detect unusual activity and want to prompt a user to complete MFA again. To register the device again later, you must generate and store a new device key.

  • In a public-client app, submit your user’s device key and access token in ForgetDevice API request.

  • In a confidential-client app, submit your user’s device key and access token in AdminForgetDevice API request.