You can now assign multiple MFA devices in IAM

At Amazon Web Services (AWS), security is our top priority, and configuring multi-factor authentication (MFA) on accounts is an important step in securing your organization.

Now, you can add multiple MFA devices to AWS account root users and AWS Identity and Access Management (IAM) users in your AWS accounts. This helps you to raise the security bar in your accounts and limit access management to highly privileged principals, such as root users. Previously, you could only have one MFA device associated with root users or IAM users, but now you can associate up to eight MFA devices of the currently supported types with root users and IAM users.

In this blog post, we review the current MFA features for IAM, share use cases for multiple MFA devices, and show you how to manage and sign in with the additional MFA devices for better resiliency and flexibility.

Overview of MFA for IAM

First, let’s recap some of the benefits and available MFA configurations for IAM.

The use of MFA is an important security best practice on AWS. With MFA, you have an additional layer of protection to help prevent unauthorized individuals from gaining access to your systems and data. MFA can help protect your AWS environments if a password associated with your root user or IAM user became compromised.

As a security best practice, AWS recommends that you avoid using root users or IAM users to manage access to your accounts. Instead, you should use AWS IAM Identity Center (successor to AWS Single Sign-On) to manage access to your accounts. You should only use root users for tasks that they are required for.

To help meet different customer needs, AWS supports three types of MFA devices for IAM, including FIDO security keys, virtual authenticator applications, and time-based one-time password (TOTP) hardware tokens. You should select the device type that aligns with your security and operational requirements. You can associate different types of MFA devices with an IAM principal.

Use cases for multiple MFA devices

There are several use cases in which associating multiple MFA devices with an IAM principal is beneficial to the security and operational efficiency of your organization, such as the following:

• In the event of a lost, stolen, or inaccessible MFA device, you can use one of the remaining MFA devices to access the account without performing the AWS account recovery procedure. If an MFA device is lost or stolen, it’s best practice to disassociate the lost or stolen device from the root users or IAM users that it’s associated with.
• Geographically dispersed teams, or teams working remotely, can use hardware-based MFA to access AWS, without shipping a single hardware device or coordinating a physical exchange of a single hardware device between team members.
• If the holder of an MFA device isn’t available, you can maintain access to your root users and IAM users by using a different MFA device associated with an IAM principal.
• You can store additional MFA devices in a secure physical location, such as a vault or safe, while retaining physical access to another MFA device for redundancy.

How to manage multiple MFA devices in IAM

You can register up to eight MFA devices, in any combination of the currently supported MFA types, with your root users and IAM users.

To register an MFA device

1. Sign in to the AWS Management Console and do the following:
   • For a root user, choose My Security Credentials.
   • For an IAM user, choose Security credentials.
2. For Multi-factor authentication (MFA), choose Assign MFA device.
3. Select the type of MFA device that you want to use and then choose Next.

With multiple MFA devices, you only need one MFA device to sign in to the console or to create a session through the AWS Command Line Interface (AWS CLI) as that principal.

You don’t need to make permissions changes in order for your organization to start taking advantage of multiple MFA devices. The root users and IAM users in your accounts that manage MFA devices today can use their existing IAM permissions to enable additional MFA devices.

Changes to Cloudtrail log entries

In support of this new feature, the identifier of the MFA device used will now be added to the console sign-in events of the root user and IAM user that use MFA. With these changes to AWS CloudTrail log entries, you can now view both the user and the MFA device used to authenticate to AWS. This provides better traceability and audibility for your accounts.

You can find this information in the MFAIdentifier field in CloudTrail, within additionalEventData. You don’t need to take action for this information to be logged. The following is a sample log from CloudTrail that includes the MFAIdentifier.

"additionalEventData": {
"LoginTo": "https://console.thinkwithwp.com/console/home?state=hashArgs%23&isauthcode=true",
"MobileVersion": "No",
"MFAIdentifier": "arn:aws:iam::111122223333:mfa/root-account-mfa-device",
"MFAUsed": "YES"
}

The identifier of the MFA devices used for AWS CLI sessions with the sts:GetSessionToken action are logged in the requestParameters field.

    "requestParameters": {
"serialNumber": "arn:aws:iam::111122223333:mfa/root-account-mfa-device"
    }

Sign-in experience with multiple MFA devices

In this section, we’ll show you how to sign in to the console as an IAM principal with multiple MFA devices associated with it.

To authenticate as an IAM principal with multiple MFA devices

1. Sign in to the IAM console as an IAM principal.
2. Authenticate with the principal’s password.
3. For Additional verification required, select the type of MFA device that you want to use to continue authenticating, and then choose Next:
   

   Figure 1: MFA device selection when authenticating to the console as an IAM user or root user with different types of MFA devices available

4. You will then be prompted to authenticate with the type of device that you selected.
   

   Figure 2: Prompt to authenticate with a FIDO security key

Conclusion

In this blog post, you learned about the new multiple MFA devices feature in IAM, and how to set up and manage multiple MFA devices in IAM. Associating multiple MFA devices with your root users and IAM users can make it simpler for you to manage access to them. This feature is available now for AWS customers, except for customers operating in AWS GovCloud (US) Regions or in the AWS China Regions. For more information about how to configure multiple MFA devices on your root users and IAM users, see the documentation on MFA in IAM. There is no extra charge to use MFA devices in IAM.

AWS offers a free MFA security key to eligible AWS account owners in the United States. To determine eligibility and order a key, see the ordering portal.

If you have questions, post them in the AWS Identity and Access Management re:Post topic or reach out to AWS Support.

 
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