vk-org / awssume

Awssume

Assume a role, do a thing.

This is a gem for assuming an AWS IAM role and using the returned temporary credentials to do something such as run a deploy script or execute an aws cli command. This gem was created because of the need to assume a role using an instance profile on an EC2 instance and use the resulting credentials to do some work. This functionality doesn't currently exist in some often used community tools.

References: AWS Cli Issue Terraform Issue

Installation

Add this line to your application's Gemfile:

gem 'awssume'

And then execute:

$ bundle

Or install it yourself as:

$ gem install awssume

Usage

This gem has the potential to be used as a library in a project using Ruby. After a few things are implemented(such as a global configuration block) usage instructions for using as a library will be added.

Currently the focus has been to use this gem as a command line tool.

You can configure env vars to authenticate with AWS:

  $ export AWS_ACCESS_KEY_ID=AKIAIOSFODNN7EXAMPLE
  $ export AWS_SECRET_ACCESS_KEY=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
  $ export AWS_DEFAULT_REGION=us-west-2

If AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY aren't set then other authentication options are checked(such as instance profiles). This is functionality provided by the aws-sdk.

  $ AWS_ROLE_ARN=arn::aws::iam::123456789012:role/RoletoAssume \
      awssume <command to execute>

  $ AWS_ROLE_ARN=arn::aws::iam::123456789012:role/RoletoAssume \
      awssume bundle exec rake component:deploy

  $ AWS_ROLE_ARN=arn::aws::iam::123456789012:role/RoletoAssume \
      awssume aws iam list-roles

There are scenarios where you might want to use an external id in a condition on your assume role policy. For such cases, the gem will look for the AWS_ROLE_EXTERNAL_ID variable in your environment. If this variable is set the value will be sent allong in the STS Assume Role request.

  $ AWS_ROLE_ARN=arn::aws::iam::123456789012:role/RoletoAssume \
    AWS_ROLE_EXTERNAL_ID=12345 \
      awssume aws iam list-roles

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/Manheim/awssume.

License

The gem is available as open source under the terms of the MIT License.