Elixir, ex_aws Library, Temporary Security Tokens

During a development effort where I had to use AWS API’s to extract information about our EC2 instances, the network powers-that-be wanted to just grant me temporary AWS credentials. I wanted to use ex_aws since its by far the most popular Elixir library for using AWS’ numerous API’s but I hadn’t used it with temporary security tokens before. It took a while to figure this out so I figured I’d write a short post about what I did.

I got the temporary keys which include a access key, a secret access key, and a security token. I set all these as environment variables for my shell. In my Elixir code I configured ex_aws using the following :

    config :ex_aws,
      debug_requests: true,
      access_key_id: [{:system, "AWS_ACCESS_KEY_ID"}, :instance_role],
      secret_access_key: [{:system, "AWS_SECRET_ACCESS_KEY"}, :instance_role],
      security_token: [{:system, "AWS_SECURITY_TOKEN"}, :instance_role],
      region: "us-east-1"

It seems very straightforward now looking at it but it still took me a while to get this to work.