Configuring OpenID Connect in Amazon Web Services

Overview

OpenID Connect (OIDC) allows your GitHub Actions workflows to access resources in Amazon Web Services (AWS), without needing to store the AWS credentials as long-lived GitHub secrets.

This guide explains how to configure AWS to trust GitHub's OIDC as a federated identity, and includes a workflow example for the aws-actions/configure-aws-credentials that uses tokens to authenticate to AWS and access resources.

Prerequisites

• Para aprender los conceptos básicos de cómo GitHub utiliza OpenID Connect (OIDC) y su arquitectura y beneficios, consulta la sección "Acerca del fortalecimiento de seguridad con OpenID Connect".

• Before proceeding, you must plan your security strategy to ensure that access tokens are only allocated in a predictable way. To control how your cloud provider issues access tokens, you must define at least one condition, so that untrusted repositories can’t request access tokens for your cloud resources. For more information, see "Configuring the OIDC trust with the cloud."

Adding the identity provider to AWS

To add the GitHub OIDC provider to IAM, see the AWS documentation.

• For the provider URL: Use https://token.actions.githubusercontent.com
• For the "Audience": Use sts.amazonaws.com if you are using the official action.

Configuring the role and trust policy

To configure the role and trust in IAM, see the AWS documentation for "Assuming a Role" and "Creating a role for web identity or OpenID connect federation".

Edit the trust relationship to add the sub field to the validation conditions. For example:

"Condition": {
  "StringEquals": {
    "token.actions.githubusercontent.com:sub": "repo:octo-org/octo-repo:ref:refs/heads/octo-branch"
  }
}

Updating your GitHub Actions workflow

To update your workflows for OIDC, you will need to make two changes to your YAML:

1. Add permissions settings for the token.
2. Use the aws-actions/configure-aws-credentials action to exchange the OIDC token (JWT) for a cloud access token.

Adding permissions settings

The workflow will require a permissions setting with a defined id-token value. If you only need to fetch an OIDC token for a single job, then this permission can be set within that job. For example:

permissions:
  id-token: write

You may need to specify additional permissions here, depending on your workflow's requirements.

Requesting the access token

The aws-actions/configure-aws-credentials action receives a JWT from the GitHub OIDC provider, and then requests an access token from AWS. For more information, see the AWS documentation.

• <example-bucket-name>: Add the name of your S3 bucket here.
• <role-to-assume>: Replace the example with your AWS role.
• <example-aws-region>: Add the name of your AWS region here.

# Sample workflow to access AWS resources when workflow is tied to branch
# The workflow Creates static website using aws s3
name: AWS example workflow
on:
  push
env:
  BUCKET_NAME : "<example-bucket-name>"
  AWS_REGION : "<example-aws-region>"
# permission can be added at job level or workflow level    
permissions:
      id-token: write
      contents: read    # This is required for actions/checkout@v2
jobs:
  S3PackageUpload:
    runs-on: ubuntu-latest
    steps:
      - name: Git clone the repository
        uses: actions/checkout@v2
      - name: configure aws credentials
        uses: aws-actions/configure-aws-credentials@master
        with:
          role-to-assume: arn:aws:iam::1234567890:role/example-role
          role-session-name: samplerolesession
          aws-region: ${{ env.AWS_REGION }}
      # Upload a file to AWS s3
      - name:  Copy index.html to s3
        run: |
          aws s3 cp ./index.html s3://${{ env.BUCKET_NAME }}/