在 Amazon Web Services 中配置 OpenID Connect

在工作流程中使用 OpenID Connect 向 Amazon Web Services 进行身份验证。

本文内容

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.

Note

Support for custom claims for OIDC is unavailable in AWS.

Prerequisites

  • To learn the basic concepts of how GitHub uses OpenID Connect (OIDC), and its architecture and benefits, see About security hardening with 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 About security hardening with OpenID Connect.

  • If you're following this guide on GHE.com, understand that you must substitute certain values in the following documentation. See About security hardening with OpenID Connect.

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 Configure AWS Credentials for GitHub Actions and Configuring a role for GitHub OIDC identity provider.

Note

AWS Identity and Access Management (IAM) recommends that users evaluate the IAM condition key, token.actions.githubusercontent.com:sub, in the trust policy of any role that trusts GitHub’s OIDC identity provider (IdP). Evaluating this condition key in the role trust policy limits which GitHub actions are able to assume the role.

Edit the trust policy, adding the sub field to the validation conditions. For example:

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

If you use a workflow with an environment, the sub field must reference the environment name: repo:ORG-NAME/REPO-NAME:environment:ENVIRONMENT-NAME. For more information, see About security hardening with OpenID Connect.

Note

When environments are used in workflows or in OIDC policies, we recommend adding protection rules to the environment for additional security. For example, you can configure deployment rules on an environment to restrict which branches and tags can deploy to the environment or access environment secrets. For more information, see Managing environments for deployment.

JSON
"Condition": {
  "StringEquals": {
    "token.actions.githubusercontent.com:aud": "sts.amazonaws.com",
    "token.actions.githubusercontent.com:sub": "repo:octo-org/octo-repo:environment:prod"
  }
}

In the following example, StringLike is used with a wildcard operator (*) to allow any branch, pull request merge branch, or environment from the octo-org/octo-repo organization and repository to assume a role in AWS.

JSON
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Federated": "arn:aws:iam::123456123456:oidc-provider/token.actions.githubusercontent.com"
            },
            "Action": "sts:AssumeRoleWithWebIdentity",
            "Condition": {
                "StringLike": {
                    "token.actions.githubusercontent.com:sub": "repo:octo-org/octo-repo:*"
                },
                "StringEquals": {
                    "token.actions.githubusercontent.com:aud": "sts.amazonaws.com"
                }
            }
        }
    ]
}

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 job or workflow run requires a permissions setting with id-token: write to allow GitHub's OIDC provider to create a JSON Web Token for every run. You won't be able to request the OIDC JWT ID token if the permissions for id-token is not set to write, however this value doesn't imply granting write access to any resources, only being able to fetch and set the OIDC token for an action or step to enable authenticating with a short-lived access token. Any actual trust setting is defined using OIDC claims, for more information see About security hardening with OpenID Connect.

The id-token: write setting allows the JWT to be requested from GitHub's OIDC provider using one of these approaches:

  • Using environment variables on the runner (ACTIONS_ID_TOKEN_REQUEST_URL and ACTIONS_ID_TOKEN_REQUEST_TOKEN).
  • Using getIDToken() from the Actions toolkit.

If you need to fetch an OIDC token for a workflow, then the permission can be set at the workflow level. For example:

YAML
permissions:
  id-token: write # This is required for requesting the JWT
  contents: read  # This is required for actions/checkout

If you only need to fetch an OIDC token for a single job, then this permission can be set within that job. For example:

YAML
permissions:
  id-token: write # This is required for requesting the JWT

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

For reusable workflows that are owned by the same user, organization, or enterprise as the caller workflow, the OIDC token generated in the reusable workflow can be accessed from the caller's context. For reusable workflows outside your enterprise or organization, the permissions setting for id-token should be explicitly set to write at the caller workflow level or in the specific job that calls the reusable workflow. This ensures that the OIDC token generated in the reusable workflow is only allowed to be consumed in the caller workflows when intended.

For more information, see Reusing workflows.

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.

  • BUCKET-NAME: Replace this with the name of your S3 bucket.
  • AWS-REGION: Replace this with the name of your AWS region.
  • ROLE-TO-ASSUME: Replace this with your AWS role. For example, arn:aws:iam::1234567890:role/example-role
YAML
# 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 : "BUCKET-NAME"
  AWS_REGION : "AWS-REGION"
# permission can be added at job level or workflow level
permissions:
  id-token: write   # This is required for requesting the JWT
  contents: read    # This is required for actions/checkout
jobs:
  S3PackageUpload:
    runs-on: ubuntu-latest
    steps:
      - name: Git clone the repository
        uses: actions/checkout@v4
      - name: configure aws credentials
        uses: aws-actions/configure-aws-credentials@e3dd6a429d7300a6a4c196c26e071d42e0343502
        with:
          role-to-assume: ROLE-TO-ASSUME
          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 }}/

Further reading