How to set up MFA on AWS?
In this article, we will see how to enable MFA for a user, and how to enforce MFA for both the console and the command line.
How to setup MFA for an IAM user
Follow the steps:
- Install FreeOTP, Google Authenticator or similar on your phone
- Login to the AWS UI: https://console.aws.amazon.com
- Select the IAM service
- Click on “Users” in the left pane
- Click on the user you want to modify in the middle pane
- Click on the “Security credentials” tab
- Next to the “Assigned MFA device” click on “Manage”
- Select “Virtual MFA device” and click on “Continue”
- Click on “Show QR code” and scan it with your chosen app on your phone
- Your app should show a 6 digit code, enter it in the field “MFA code 1”
- Wait for a little while until the app shows another code
- Enter that 2nd code in the field “MFA code 2”
- Click on “Assign MFA”
How to enforce MFA
This section will detail how to ensure that users must go through MFA before they can do anything in your AWS account.
Create a role
For the sake of example, I will create an IAM role with administrator access. This is the role that users will assume after logging in. This role can be assumed only if the user has MFA enabled and passed the MFA step.
Create a role with the following trust relationship:
To create such a role in the AWS console, follow these steps:
- Navigate to the IAM console
- Click on “Roles” in the left pane
- Click on “Create role”
- For the trusted entity type, select “AWS account”
- Then select “This account”
- Tick the box “Require MFA”
- Click “Next”
- For the policy, select “AdministratorAccess”, or some more restrictive policies if that’s your goal
- Click “Next”
- Give the role a name (eg:
AdminRole) and click “Create role”
Create a policy
The next step is to create a policy to assume the above role. The policy document should look like this:
- In the IAM console, click on “Policies” in the left pane
- Click on “Create policy”
- Enter a JSON policy that looks like the one above (replace the values for your circumstances)
- Click on “Next: Tags”
- Add tags if you want
- Click on “Next: Review”
- Give the policy a name (eg:
AssumeAdminPolicy) and click “Create policy”
Create a user group
The next step is to create a group of users who will be able to assume the role thanks to the policy:
- In the IAM console, click on “User groups” in the left pane
- Click on “Create group”
- Give a name to the groups (eg:
- Add users to the group if you want (you can always do that later)
- Attach the
- Click on “Create group”
You should ensure that users do not get additional permissions from being member of other groups or policies directly attached to them, otherwise that will defeat the purpose of mandating MFA in the first place.
How to login on the AWS console
To login to the AWS console, point your browser to https://console.aws.amazon.com/ and enter the required details. The next screen will ask you for your MFA.
Now you are logged in but you should pretty much be unable to do
anything. Click on your name in the top-right corner and click on
“switch role”. For the “Account” field, enter the same id as the
account you just logged into. For the “Role” field, enter
(or whatever name you chose for the role). You can choose a display
name and colour. Click on “Switch Role”. That’s it!
Next time you log in, when you click on your name in the top-right corner, you will see a section “role history” where you can just click directly on the display name you chose in the previous step.
How to login with the AWS cli
~/.aws/credentials file to add your access key id and
secret access key. It should look like this:
[base] aws_access_key_id = AKIAxxxx aws_secret_access_key = xxxxxxx
Now edit your
~/.aws/config file so it looks like this:
[profile base] region = PREFERRED_REGION output = json mfa_serial = arn:aws:iam::ACCOUNT_NUMBER:mfa/USERNAME [profile main] source_profile = base role_arn = arn:aws:iam::ACCOUNT_NUMBER:role/AdminRole
The next time you run the aws cli, it will ask you for your MFA.