AWS Authentication

To deploy infrastructure on AWS using Terraform, you must authenticate Terraform to your AWS account. This guide covers real-life scenarios for local development, CI/CD pipelines, and multi-account setups, with best practices for security and automation.

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1. Local Development: AWS CLI Credentials

The simplest way to authenticate is to use the AWS CLI. Configure your credentials with:

aws configure

This stores your credentials in ~/.aws/credentials and region in ~/.aws/config:

[default]
aws_access_key_id = AKIA...
aws_secret_access_key = ...
region = eu-west-1

Terraform will automatically use these credentials.

Best Practice: Use named profiles for multiple accounts:

[dev]
aws_access_key_id = ...
aws_secret_access_key = ...
region = us-east-1

[prod]
aws_access_key_id = ...
aws_secret_access_key = ...
region = eu-west-1

Reference a profile in your provider block:

provider "aws" {
  region  = var.aws_region
  profile = var.aws_profile
}

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2. CI/CD Pipelines: Environment Variables

For automation (GitHub Actions, GitLab CI, Azure Pipelines), use environment variables for credentials:

export AWS_ACCESS_KEY_ID=AKIA...
export AWS_SECRET_ACCESS_KEY=...
export AWS_DEFAULT_REGION=us-east-1

GitHub Actions Example:

jobs:
  terraform:
    runs-on: ubuntu-latest
    env:
      AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
      AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
      AWS_DEFAULT_REGION: us-east-1
    steps:
      - uses: actions/checkout@v4
      - uses: hashicorp/setup-terraform@v3
      - run: terraform init
      - run: terraform apply -auto-approve

GitLab CI Example:

variables:
  AWS_ACCESS_KEY_ID: $AWS_ACCESS_KEY_ID
  AWS_SECRET_ACCESS_KEY: $AWS_SECRET_ACCESS_KEY
  AWS_DEFAULT_REGION: us-east-1

stages:
  - apply

apply:
  stage: apply
  image: hashicorp/terraform:1.7.5
  script:
    - terraform init
    - terraform apply -auto-approve

Azure DevOps Example:

steps:
- script: |
    export AWS_ACCESS_KEY_ID=$(AWS_ACCESS_KEY_ID)
    export AWS_SECRET_ACCESS_KEY=$(AWS_SECRET_ACCESS_KEY)
    terraform init
    terraform apply -auto-approve
  env:
    AWS_ACCESS_KEY_ID: $(AWS_ACCESS_KEY_ID)
    AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)

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3. Advanced: Assume Role for Multi-Account/MFA

For organizations using AWS Organizations or requiring MFA, use the assume_role block:

provider "aws" {
  region = var.aws_region
  assume_role {
    role_arn = "arn:aws:iam::123456789012:role/terraform-deployer"
  }
}

Best Practice: Use short-lived credentials and roles for CI/CD, never long-lived root keys.

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4. NixOS: Declarative AWS Credentials

Add credentials as environment variables in your NixOS configuration:

# configuration.nix
{
  environment.variables = {
    AWS_ACCESS_KEY_ID = "...";
    AWS_SECRET_ACCESS_KEY = "...";
    AWS_DEFAULT_REGION = "us-east-1";
  };
}

Or use agenix for encrypted secrets.

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Best Practices

• Use IAM roles and short-lived credentials for automation (never root keys)

• Store secrets in a secure vault (GitHub/Azure/GitLab secrets, HashiCorp Vault, SSM Parameter Store)

• Use named profiles for multi-account setups

• Rotate credentials regularly

• Enable MFA for all users

• Use least privilege IAM policies

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References

• Terraform AWS Provider Auth Docs

• AWS CLI Configuration

• Terraform in GitHub Actions

• Terraform in GitLab CI/CD

• Terraform in Azure DevOps

Tip: For cloud-native, secure, and auditable deployments, always use roles and secret managers instead of hardcoded credentials.

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- [Authenticating Terraform with AWS](pages/terraform/aws/aws_auth_terraform.md)