AWS Vault and MFA Setup on my Mac

Recently, I decided to secure my local machine by downloading and using AWS Vault. To my surprise, setting up MFA with Vault required a step or two more that I wasn't expecting. Here are my findings/steps.

First, I used homebrew to install aws-vault.

brew cask install aws-vault

Then I added my profile and followed the instructions which had me provide my Access ID and Secret.

aws-vault add taylor

Then I tried to list out the S3 buckets via:

aws-vault exec taylor -- aws s3 ls

This resulted in the following error.

An error occurred (AccessDenied) when calling the ListBuckets operation: Access Denied

So I opened up my AWS config file in Visual Studio Code.

code ~/.aws/config

Doing so lead me to see that my profile didn't have a mfa_serial variable defined. I found my key in IAM under my own user's Security Credentials tab and added it to the file.

Now, my config file had the following in it:

[profile taylor]
mfa_serial=arn:aws:iam::XXXXXXXXXX:mfa/taylor

And when I performed my s3 listing again, it worked.