aws-google-auth

This command-line tool allows you to acquire AWS temporary (STS) credentials using Google Apps as a federated (Single Sign-On, or SSO) provider.

Setup

You'll first have to set up Google Apps as a SAML identity provider (IdP) for AWS. There are tasks to be performed on both the Google Apps and the Amazon sides; these references should help you with those configurations:

• How to Set Up Federated Single Sign-On to AWS Using Google Apps
• Using Google Apps SAML SSO to do one-click login to AWS

If you need a fairly simple way to assign users to roles in AWS accounts, we have another tool called Google AWS Federator that might help you.

Important Data

You will need to know Google's assigned Identity Provider ID, and the ID that they assign to the SAML service provider.

Once you've set up the SAML SSO relationship between Google and AWS, you can find the SP ID by drilling into the Google Apps console, under Apps > SAML Apps > Settings for AWS SSO -- the URL will include a component that looks like ...#AppDetails:service=123456789012... -- that number is GOOGLE_SP_ID

You can find the GOOGLE_IDP_ID, again from the admin console, via Security > Set up single sign-on (SSO) -- the SSO URL includes a string like https://accounts.google.com/o/saml2/idp?idpid=aBcD01AbC where the last bit (after the =) is the IDP ID.

Installation

You can install quite easily via pip, if you want to have it on your local system:

localhost$ sudo pip install aws-google-auth

If you don't want to have the tool installed on your local system, or if you prefer to isolate changes, there is a Dockerfile provided, which you can build with:

localhost$ cd ..../aws-google-auth && docker build -t aws-google-auth .

Usage

$ aws-google-auth --help
usage: aws-google-auth [-h] [-v] [-u USERNAME] [-I IDP_ID] [-S SP_ID]
                       [-R REGION] [-d DURATION] [-p PROFILE]

Acquire temporary AWS credentials via Google SSO

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         show program's version number and exit

  -u USERNAME, --username USERNAME
                        Google Apps username ($GOOGLE_USERNAME)
  -I IDP_ID, --idp-id IDP_ID
                        Google SSO IDP identifier ($GOOGLE_IDP_ID)
  -S SP_ID, --sp-id SP_ID
                        Google SSO SP identifier ($GOOGLE_SP_ID)
  -R REGION, --region REGION
                        AWS region endpoint ($AWS_DEFAULT_REGION)
  -d DURATION, --duration DURATION
                        Credential duration ($DURATION)
  -p PROFILE, --profile PROFILE
                        AWS profile ($AWS_PROFILE)
  -a ASK_ROLE, --ask-role ASK_ROLE
                        Set true to always pick the role

Native Python

1. Execute aws-google-auth
2. You will be prompted to supply each parameter

Note You can skip prompts by either passing parameters to the command, or setting the specified Environment variables.

Via Docker

1. Set environment variables for GOOGLE_USERNAME, GOOGLE_IDP_ID, and GOOGLE_SP_ID (see above under "Important Data" for how to find the last two; the first one is usually your email address)
2. For Docker: docker run -it -e GOOGLE_USERNAME -e GOOGLE_IDP_ID -e GOOGLE_SP_ID aws-google-auth

You'll be prompted for your password. If you've set up an MFA token for your Google account, you'll also be prompted for the current token value.

If you have more than one role available to you, you'll be prompted to choose the role from a list; otherwise, if your credentials are correct, you'll just see the AWS keys printed on stdout.

Storage of profile credentials

Through the use of AWS profiles, using the -p or --profile flag, the aws-google-auth utility will store the supplied username, IDP and SP details in your ./aws/config files.

When re-authenticating using the same profile, the values will be remembered to speed up the re-authentication process. This enables an approach that enables you to enter your username, IPD and SP values once and then after only need to re-enter your password (and MFA if enabled).

Creating an alias as below can be a quick and easy way to re-authenticate with a simple command shortcut.

alias aws-development='unset AWS_PROFILE; aws-google-auth -p aws-dev; export AWS_PROFILE=aws-dev'

Notes on Authentication

Google supports a number of 2-factor authentication schemes. Each of these results in a slightly different "next" URL, if they're enabled, during do_login

Google controls the preference ordering of these schemes in the case that you have multiple ones defined.

The varying 2-factor schemes and their representative URL fragments handled by this tool are:

Method	URL Fragment
No second factor	(none)
TOTP (eg Google Authenticator or Authy)	.../signin/challenge/totp/2?...
SMS (or voice call)	.../signin/challenge/ipp/2?...
Google Prompt (phone app)	.../signin/challenge/az/2?...
Backup code (printed codes)	... (unknown yet) ...
Security key (eg yubikey)	... (unknown yet) ...

Acknowledgements

This work is inspired by keyme -- their digging into the guts of how Google SAML auth works is what's enabled it.

The attribute management and credential injection into AWS configuration files was heavily borrowed from aws-adfs <https://github.com/venth/aws-adfs>