Cognito Identity Pool Authentication

Use this action to perform authentication with an Amazon Cognito Identity Pool using the GitHub Actions OIDC access token. More details about this use-case can be read here.

This action supports both Enhanched (Simplified) AuthFlow and the Basic (Classic) AuthFlow.

Table of Contents

• Usage
• Standard Input Parameters
• Role Chain Input Parameters
• Output
• Passing Claims (Session Tags)
  • Passing Repository Name
• Usage - Role Chain
• Environment Variables
• Credentials Behaviour
  • Behaviour when Role Chaining
• Custom Role Arn (Enhanced AuthFlow only)
• Use as a Template
• Use with a wrapper
• Contributing

Usage

on:
  workflow_dispatch:
jobs:
  job1:
    runs-on: ubuntu-latest
    permissions:
      id-token: write
    steps:
      - name: "Authenticate using Enhanced AuthFlow"
        uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "enhanced"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          aws-account-id: "111111111111"
          aws-region: "eu-west-1"
          audience: "cognito-identity.amazonaws.com" # Default
          set-in-environment: true

      - name: "Authenticate using Basic AuthFlow"
        uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "basic"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          role-arn: "arn:aws:iam::111111111111:role/GhaCognito"
          aws-account-id: "111111111111"
          aws-region: "eu-west-1"
          audience: "cognito-identity.amazonaws.com" # Default
          set-in-environment: true

      - name: "STS Get Caller Identity"
        run: |
          aws sts get-caller-identity

Standard Input Parameters

• cognito-identity-pool-id and auth-flow are required.
• cognito-identity-provider-name can be used if issuer OIDC claim is customized.
• aws-account-id and aws-region are required, but values can optionally be derived from environment variables, if this behaviour is wanted.
• If providing role-arn and auth-flow is enhanced, then aws-account-id can be extracted from the ARN.
• Input to action via parameters will supersede environment variables for aws-account-id and aws-region.
  • Env Var 1 supersedes Env Var 2.

Basic AuthFlow Parameters

When using auth-flow basic, the following parameters are also available.

Role Chain Input Parameters

Role chaining can optionally be performed after authenticating with Cognito Identity.

• It's not possible to set both set-in-environment and chain-set-in-environment to true. Doing so will fail validation

Output

If performing a role-chain, those credentials are used as output.

Passing Claims (Session Tags)

It's possible to pass one or more claims from the initial role session to the next session when role chaining. This is done by specifying one or more GitHub Actions claims in chain-pass-claims.

[!WARNING] Make sure the role being assumed allows sts:TagSession and that any claims being passed are validated by an sts:AssumeRole permissions policy. If this is not done, it might be possible for an attacker to escalate privileges if they manually make the same calls this action makes, but substitute their own values for the tags when chaining roles.

For example, if chain-pass-claims is job_workflow_ref,repository, then the following condition could be used in the IAM policy on the initial role:

{
  "Sid": "AllowAssumptionIfTagsMatch",
  "Effect": "Allow",
  "Action": "sts:AssumeRole",
  "Resource": "arn:aws:iam::*:role/pattern-matching-the-roles-to-allow-*",
  "Condition": {
    "Null": {
      "aws:TagKeys": "false"
    },
    "ForAllValues:StringEquals": {
      "aws:TagKeys": ["job_workflow_ref", "repository"]
    },
    "StringEquals": {
      "sts:RoleSessionName": "GitHubActions",
      "aws:PrincipalTag/Repository": "${aws:RequestTag/repository}",
      "aws:PrincipalTag/job_workflow_ref": "${aws:RequestTag/job_workflow_ref}"
    }
  }
}

This verifies that all the expected tags are set, and that the values match the ones we got from the GitHub token. The principal at this point is the initial role session, with PrincipalTag tags set by Cognito from the GitHub Actions claims. The aws:RequestTag tags are the tags passed by the caller of AssumeRole - i.e. this action or an attacker.

[!IMPORTANT] The claims job_workflow_ref and environment is not available via an environment variable. Because of this, this action will parse the GitHub Actions access token already available and used in this action to find the value of these claims.

This parsing will only occur if performing role-chaining and if passing the claim job_workflow_ref or environment.

Find step with id "missing_claims" in action.yml to view details.

The following claims can be passed by this action: actor, actor_id, base_ref, event_name, head_ref, job_workflow_ref, ref, ref_type, repository, repository_id, repository_name, repository_owner, repository_owner_id, run_attempt, run_id, run_number, runner_environment, sha, and environment.

Passing Repository Name

repository_name is a special case. GitHub doesn't provide this as a claim, but it's derived from repository claim (which is of the form repository_owner/repository_name) as it is often used in IAM policies. As above, you must validate this claim. You can use a condition like:

{
  "StringEquals": {
     // Validate repository_name
    "aws:PrincipalTag/repository": "${aws:RequestTag/repository_owner}/${aws:RequestTag/repository_name}",
     // Add if wanting to continue using the claim
    "aws:RequestTag/repository": "${aws:PrincipalTag/repository}"
  }
}

to do this. Note that this requires you to also map repository and repository_owner in your Cognito Identity Pool.

Usage - Role Chain

on:
  workflow_dispatch:
    inputs:
      environment:
        required: true
        description: Environment
jobs:
  job1:
    runs-on: ubuntu-latest
    environment: ${{ inputs.environment }}
    permissions:
      contents: read
      id-token: write
    steps:
      - uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "basic"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          aws-region: "eu-west-1"
          aws-account-id: "111111111111"
          role-arn: "arn:aws:iam::111111111111:role/GhaCognito"
          set-as-profile: "pool"
          chain-role-arn: "arn:aws:iam::222222222222:role/github-actions/WorkloadDeploymentDev"
          chain-pass-claims: "actor,ref,sha,repository,run_attempt,run_id,environment"
          chain-set-in-environment: true
      - run: |
          aws sts get-caller-identity
          aws sts get-caller-identity --profile pool

Environment Variables

on:
  workflow_dispatch:
env:
  CK_COGNITO_AWS_ACCOUNT_ID: "${{ vars.CK_COGNITO_AWS_ACCOUNT_ID }}"
  AWS_DEFAULT_REGION: "us-east-1"
  AWS_REGION: "us-west-1" # Overrides AWS_DEFAULT_REGION
jobs:
  job1:
    runs-on: ubuntu-latest
    permissions:
      id-token: write
    steps:
      - name: "Authenticate using Enhanced AuthFlow"
        uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "enhanced"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          aws-region: "eu-west-1" # Overrides AWS_REGION env var

      - name: "STS Get Caller Identity"
        run: |
          aws sts get-caller-identity

Credentials Behaviour

• Credentials are always available as output parameters from the action.
  • The exception is when auth-flow is basic and no role-arn has been provided. Then only the cognito_oidc_access_token is available.
• Set input option set-in-environment to true and standard AWS environment variables will be set.
• Provide a profile name in input option set-as-profile to set credentials as a profile.
• Providing set-in-environment as true, and set-as-profile with a value will both set environment variables and a profile.
• When neither set-in-environment nor set-as-profile is provided, credentials are only available as outputs.

Behaviour when Role Chaining

This is in addition to what is listed above.

• Action output will contain role-chained credentials
• Set input option chain-set-in-environment to true and standard AWS environment variables will be set.
  • It's not possible to set both set-in-environment and chain-set-in-environment to true. Doing so will fail validation before performing any authentication.
• Provide a profile name in input option chain-set-as-profile to set credentials as a profile.
• Providing chain-set-in-environment as true, and chain-set-as-profile with a value will both set environment variables and a profile.
• When neither chain-set-in-environment nor chain-set-as-profile is provided, credentials are only available as outputs.

on:
  workflow_dispatch:

jobs:
  job1:
    runs-on: ubuntu-latest
    permissions:
      id-token: write
    steps:
      - id: aws-credentials
        name: "Credentials as output only"
        uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "enhanced"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          aws-region: "eu-west-1"
          aws-account-id: "111111111111"

      - name: "Credentials in environment"
        uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "enhanced"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          aws-region: "eu-west-1"
          aws-account-id: "111111111111"
          set-in-environment: true

      - name: "Credentials in profile: tf-state"
        uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "enhanced"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          aws-region: "eu-west-1"
          aws-account-id: "111111111111"
          set-as-profile: "tf-state"

      - name: STS Get Caller Identity
        run: |
          aws sts get-caller-identity
          aws sts get-caller-identity --profile tf-state

      - name: "STS Get Caller Identity"
        env:
          AWS_ACCESS_KEY_ID: "${{ steps.aws-credentials.outputs.aws_access_key_id }}"
          AWS_SECRET_ACCESS_KEY: "${{ steps.aws-credentials.outputs.aws_secret_access_key }}"
          AWS_SESSION_TOKEN: "${{ steps.aws-credentials.outputs.aws_session_token }}"
        run: |
          aws sts get-caller-identity

      - id: oidc_token
        name: "Get Cognito OIDC Access Token"
        uses: catnekaise/cognito-idpool-auth@main
        with:
          auth-flow: "basic"
          cognito-identity-pool-id: "eu-west-1:11111111-example"
          aws-region: "eu-west-1"
          aws-account-id: "111111111111"

      - name: "Assume Role"
        env:
          OIDC_TOKEN: "${{ steps.oidc_token.outputs.cognito_identity_oidc_access_token }}"
          AWS_DEFAULT_REGION: "eu-west-1"
        run: |
          awsCredentials=$(aws sts assume-role-with-web-identity \
          --role-session-name "MySessionName" \
          --role-arn "arn:aws:iam::111111111111:role/GhaCognito" \
          --duration-seconds 3600 \
          --web-identity-token "$OIDC_TOKEN")

          awsAccessKeyId=$(echo "$awsCredentials" | jq -r ".Credentials.AccessKeyId")
          awsSecretAccessKey=$(echo "$awsCredentials" | jq -r ".Credentials.SecretAccessKey")
          awsSessionToken=$(echo "$awsCredentials" | jq -r ".Credentials.SessionToken")

          echo "::add-mask::$awsAccessKeyId"
          echo "::add-mask::$awsSecretAccessKey"
          echo "::add-mask::$awsSessionToken"

Custom Role Arn (Enhanced AuthFlow only)

A custom role arn can be provided during authentication. Read more at https://docs.aws.amazon.com/cognito/latest/developerguide/role-based-access-control.html#using-rules-to-assign-roles-to-users.

Input role-arn is the custom role arn when auth-flow is also set to enhanced.

on:
  workflow_dispatch:
jobs:
  job1:
    runs-on: ubuntu-latest
    permissions:
      id-token: write
    steps:
      - name: "Authenticate"
        uses: catnekaise/cognito-idpool-auth@main
        with:
         cognito-identity-pool-id: "eu-west-1:11111111-example"
         auth-flow: "enhanced"
         role-arn: "arn:aws:iam::111111111111:role/GhaCognitoCustom"
         set-in-environment: true
         aws-region: "eu-west-1"
         aws-account-id: "111111111111"

      - name: STS Get Caller Identity
        run: |
          aws sts get-caller-identity

Use as a Template

Copy and paste the existing action.yml in this repository to your own repository and customize it as you see fit.

Use with a wrapper

Use the "wrapper-template" below and pin using of this action to a specific commit.

Optionally set one or more defaults in inputs to reduce amount of repetitive input.

name: Wrapped Cognito Identity Auth
inputs:
  aws-account-id:
    required: false
    # Optionally set defaults in inputs
    default: "111111111111"
    description: "AWS Account ID"
  # Copy remaining inputs from ./action.yml
outputs:
  aws_access_key_id:
    description: "AWS Access Key Id"
    value: ${{ steps.auth.outputs.aws_access_key_id }}
  aws_secret_access_key:
    description: "AWS Secret Access Key"
    value: ${{ steps.auth.outputs.aws_secret_access_key }}
  aws_session_token:
    description: "AWS Session Name"
    value: ${{ steps.auth.outputs.aws_session_token }}
  aws_region:
    description: "AWS Region"
    value: ${{ steps.auth.outputs.aws_region }}
  cognito_identity_oidc_access_token:
    description: "Cognito Identity OIDC Access Token"
    value: ${{ steps.auth.outputs.cognito_identity_oidc_access_token }}
runs:
  using: composite
  steps:
    - id: auth
      uses: catnekaise/cognito-idpool-auth@SHA_HERE
      with: 
        cognito-identity-pool-id: "${{ inputs.cognito-identity-pool-id }}"
        auth-flow: "${{ inputs.auth-flow }}"
        aws-region: "${{ inputs-aws-region }}"
        audience: "${{ inputs.audience }}"
        aws-account-id: "${{ inputs.aws-account-id }}"        
        role-arn: "${{ inputs.role-arn }}"
        role-duration-seconds: "${{ inputs.role-duration-seconds }}"
        role-session-name: "${{ inputs.role-session-name }}"
        set-as-profile: "${{ inputs.set-as-profile }}"
        set-in-environment: "${{ inputs.set-in-environment }}"
        chain-role-arn: "${{ inputs.chain-role-arn }}"
        chain-role-duration-seconds: "${{ inputs.chain-role-duration-seconds }}"
        chain-role-session-name: "${{ inputs.chain-role-session-name }}"
        chain-pass-claims: "${{ inputs.chain-pass-claims }}"
        chain-set-as-profile: "${{ inputs.chain-set-as-profile }}"
        chain-set-in-environment: "${{ inputs.chain-set-in-environment }}"

Contributing

Contributions are welcome. This action can use more testing and reviews of the large amount of shell scripting.