aws-saml-auth 0.9.1

Installation

The easiest option is to to install with uv

uv tool install aws-saml-auth

or with pip

python3 -m pip install aws-saml-auth

Python 3.12 or newer is required.

Its also possible to use the docker image ekreative/aws-saml-auth.

Setup

You will need to know your SAML Providers SSO URL.

For Google Workspace the url by right clicking copy url from the AWS App that you setup in the Apps menu or from the ‘Test SAML Login’ button in the Apps settings.

You can store the url in an env var or pass it to the –login-url argument.

export ASA_LOGIN_URL="https://accounts.google.com/o/saml2/initsso?idpid=XXX&spid=XXX&forceauthn=false"

If you dont have an AWS SAML App available talk to your Administrator and point them to the Setup AWS SAML and Google Workspace section below.

Credential Process

In you aws config file (~/.aws/config) you can setup a profile to use the credential process

[profile my_profile]
credential_process = aws-saml-auth --credential-process
region = eu-west-1
asa.login_url = https://accounts.google.com/o/saml2/initsso?idpid=some_idp&spid=some_spid&forceauthn=false

If you have multiple roles available you must add the asa.role_arn setting. You can also use this to have multiple profiles with different AWS accounts.

AWS process will trigger the login flow automatically whenever your credentials expire.

Usage

You can run the command aws-saml-auth to authenticate aws-cli. By default it will edit your default credentials. You can export the variable AWS_PROFILE=my_profile and then aws-saml-auth and aws-cli will use this profile.

$ aws-saml-auth -h
usage: aws-saml-auth [-h] [--redirect-server | -L LOGIN_URL] [-R REGION] [-d DURATION | --auto-duration] [-p PROFILE] [-A ACCOUNT] [-q] [--saml-assertion SAML_ASSERTION] [--no-saml-cache] [--print-creds | --credential-process]
                 [--no-resolve-aliases] [--port PORT] [--no-ask-role | -r ROLE_ARN] [-l {debug,info,warn}] [-V]

Acquire temporary AWS credentials via SAML

optional arguments:
  -h, --help            show this help message and exit
  --redirect-server     Run the redirect server on port ($PORT)
  -L LOGIN_URL, --login-url LOGIN_URL
                        SAML Provider login url ($ASA_LOGIN_URL)
  -R REGION, --region REGION
                        AWS region endpoint ($AWS_DEFAULT_REGION)
  -d DURATION, --duration DURATION
                        Credential duration in seconds (defaults to value of $ASA_DURATION, then falls back to 43200)
  --auto-duration       Tries to use the longest allowed duration ($ASA_AUTO_DURATION=1)
  -p PROFILE, --profile PROFILE
                        AWS profile (defaults to value of $AWS_PROFILE, then falls back to 'default')
  -A ACCOUNT, --account ACCOUNT
                        Filter for specific AWS account ($ASA_AWS_ACCOUNT)
  -q, --quiet           Quiet output
  --saml-assertion SAML_ASSERTION
                        Base64 encoded SAML assertion to use
  --no-saml-cache       Do not cache the SAML Assertion ($ASA_NO_SAML_CACHE=1)
  --print-creds         Print Credentials
  --credential-process  Output suitable for aws cli credential_process ($ASA_CREDENTIAL_PROCESS=1)
  --no-resolve-aliases  Do not resolve AWS account aliases. ($ASA_NO_RESOLVE_ALIASES=1)
  --port PORT           Port for the redirect server ($PORT)
  --no-ask-role         Never ask to pick the role ($ASA_NO_ASK_ROLE=1)
  -r ROLE_ARN, --role-arn ROLE_ARN
                        The ARN of the role to assume ($ASA_ROLE_ARN)
  -l {debug,info,warn}, --log {debug,info,warn}
                        Select log level (default: warn)
  -V, --version         show program's version number and exit

Via Docker

1. Set environment variables for anything listed in Usage with ($VARIABLE) after command line option:

   ASA_LOGIN_URL (see above under “Important Data” for how to find these)

   AWS_PROFILE: Optional profile name you want the credentials set for (default is ‘sts’)

   ASA_ROLE_ARN: Optional ARN of the role to assume

2. For Docker: docker run -it -e ASA_LOGIN_URL -e AWS_PROFILE -e ASA_ROLE_ARN -p 4589:4589 -v ~/.aws:/root/.aws ekreative/aws-saml-auth

You will be be shown a URL to visit in your browser

If you have more than one role available to you (and you haven’t set up ASA_ROLE_ARN), you’ll be prompted to choose the role from a list.

Logging in without a browser

Inside a container, or over ssh, there is no browser to open and the browser you do have may not be able to reach 127.0.0.1:4589 where the command is listening. aws-saml-auth always prints the login url, so open it yourself, and it waits for the assertion on two paths at once:

• the browser reaching the login server, as usual

• you pasting it, when the browser cannot

After logging in the redirect server shows a page that sends your browser on to http://127.0.0.1:4589/?SAMLResponse=.... If your browser will not go there, or goes there and cannot connect, that page also shows the assertion in a box to copy. Paste either the assertion or the whole url from the address bar at the prompt.

Browsers increasingly refuse to navigate from a public https page to a private address like 127.0.0.1, so the copy and paste route is the reliable one whenever the command is not on the same machine as the browser.

Publishing the port (docker run -p 4589:4589 ...) lets the browser reach the container directly, and then nothing needs pasting.

The paste prompt needs a terminal, so it is not offered under --credential-process, where the aws cli captures both stdout and stderr and you would never see it. Log in once directly instead, and the aws cli will use the cached token afterwards:

aws-saml-auth --credential-process -p my_profile >/dev/null

Storage of profile credentials

Through the use of AWS profiles, using the -p or --profile flag, the aws-saml-auth utility will store the supplied Login Url 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 provide your Login URL value only once

Setup AWS SAML and Google Workspace

You’ll first have to set up your SAML identity provider (IdP) for AWS. There are tasks to be performed on both the Google Workspace 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.

Note If you want a longer session than the AWS default 3600 seconds (1 hour) duration, you must also modify the IAM Role to permit this. See the AWS documentation for more information.

To enable browser based login, you will need to host the redirect server somewhere with HTTPS enabled, you might use a serverless google cloud run deployment for example:

gcloud run deploy --image gcr.io/my-project/aws-saml-auth --args=--redirect-server --platform managed

Beware for google cloud run you must copy the docker image to your account:

docker pull ekreative/aws-saml-auth
docker tag ekreative/aws-saml-auth gcr.io/my-project/aws-saml-auth
docker push gcr.io/my-project/aws-saml-auth

Then change your SAML provider settings so the ACS URL points to the redirect server.

The redirect server answers the ACS URL post with a page that both sends the browser on to http://127.0.0.1:4589/?SAMLResponse=... and shows the assertion for copying, because a browser may refuse the first. Clients older than 0.9.0 only accept the assertion as a post, so upgrade them alongside the redirect server.

You will also need to change the Trust Relationship of your IAM Role to allow SAML:aud to be the host of your redirect server.

See the example, replacing “https://redirect-server.com/saml” with your own.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Federated": "arn:aws:iam::XXX:saml-provider/XXX"
      },
      "Action": "sts:AssumeRoleWithSAML",
      "Condition": {
        "StringEquals": {
          "SAML:aud": [
            "https://signin.aws.amazon.com/saml",
            "https://redirect-server.com/saml"
          ]
        }
      }
    }
  ]
}

Development

If you want to develop the Aws-saml-auth tool itself, we thank you! The project uses uv, which manages the virtualenv and the locked dependencies for you.

# Create the virtualenv and install everything, including dev dependencies
uv sync

# Run the tool from the checkout
uv run aws-saml-auth --help

# Run the tests
uv run pytest

# Format and lint
uv run ruff format
uv run ruff check

If you use direnv, an .envrc of

watch_file pyproject.toml uv.lock
uv sync
export VIRTUAL_ENV="$PWD/.venv"
PATH_add "$PWD/.venv/bin"

keeps the environment in sync and on your PATH when you enter the directory.

We welcome you to review our code of conduct and contributing documents.

Acknowledgments

This work is inspired by aws-google-auth – this version has changed to use browser login flow only and avoid handling user passwords.