DevOps Knowledge Hub
DevOps Knowledge Hub

Best Practices for Securely Managing Credentials with the AWS CLI

Learn the definitive best practices for securing your AWS CLI credentials. This guide covers the credential loading order, proper use of configuration files, environment variables, and crucially, how to leverage IAM roles and AWS SSO to eliminate the risk of storing long-lived static access keys. Implement these strategies to achieve robust security in your AWS automation and management workflows.

42 views

Best Practices for Securely Managing Credentials with the AWS CLI

Managing credentials securely is paramount when interacting with Amazon Web Services (AWS) through the Command Line Interface (CLI). Access keys (Access Key ID and Secret Access Key) grant programmatic access to your cloud resources, making their compromise a significant security risk. This article outlines crucial best practices for storing, managing, and utilizing these credentials to minimize exposure and maintain a robust security posture when automating tasks or managing resources via the CLI.

The AWS CLI relies on specific methods to locate credentials. Understanding these methods—from configuration files to environment variables and IAM Roles—is the first step toward securing your environment. We will explore the recommended order of precedence and highlight modern, safer alternatives to hardcoding secrets.

Understanding AWS CLI Credential Loading Order

The AWS CLI resolves credentials using a defined hierarchy. Knowing this order helps you understand where the CLI looks for credentials first and ensures your intended, most secure configuration takes precedence.

The CLI checks for credentials in the following order (from highest priority to lowest):

  1. Command Line Options: Credentials passed directly via flags (--access-key-id and --secret-access-key).
  2. Environment Variables: Credentials set in the current shell session.
  3. Credential Process: The output from a configured credential process (often used by SSO or external tools).
  4. AWS Credential Provider Chain: This chain checks the following in order:
    a. Credentials from an IAM role assigned to the running EC2 instance or ECS task.
    b. Credentials stored in the shared credentials file (~/.aws/credentials).
  5. Configuration File: If no credentials are found, the CLI will stop searching.

Security Tip: Relying on command-line flags is generally discouraged for regular use, as command history (.bash_history) can expose sensitive information.

1. Securing Credentials in Configuration Files (~/.aws/credentials)

By default, the AWS CLI stores credentials in the shared credentials file, typically located at ~/.aws/credentials. While convenient, this file must be protected.

File Protection and Permissions

It is vital to restrict read access to this file. On Linux/macOS systems, set permissions so only the owner can read or write the file:

chmod 600 ~/.aws/credentials

Using Profiles for Segregation

Using distinct profiles allows you to separate credentials for different environments (e.g., development, staging, production) or different accounts. This prevents accidental cross-environment actions.

Example ~/.aws/credentials:

[default]
aws_access_key_id = AKIABCDEFGHIJKLMNO
aws_secret_access_key = xYzdEfGhIjKlMnOpQrStUvWxYz1234567890

[production-user]
aws_access_key_id = AKIA9876543210ZYXWVU
aws_secret_access_key = aBcDeFgHiJkLmNoPqRsTuVwXyZ9876543210

When using a named profile, you must specify it with the --profile flag:

aws s3 ls --profile production-user

2. Leveraging Environment Variables

Environment variables offer a dynamic way to provide credentials to the CLI session without writing them to disk. This is often preferred for temporary access or within scripting environments where disk writing is restricted or undesirable.

Set the following variables in your shell session:

export AWS_ACCESS_KEY_ID="AKIAIOSFODNN7EXAMPLE"
export AWS_SECRET_ACCESS_KEY="wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY"
export AWS_DEFAULT_REGION="us-east-1"

Important Note on Precedence: Credentials set via environment variables always override those found in the ~/.aws/credentials file, as they appear higher in the credential loading chain.

Security Warning: Be cautious when exporting environment variables, especially in shared terminals or scripts that might be logged. Always unset them immediately after use:
bash unset AWS_ACCESS_KEY_ID unset AWS_SECRET_ACCESS_KEY

3. The Most Secure Method: IAM Roles (Instance Profiles/Web Identity)

For workloads running on AWS infrastructure (like EC2 instances, Lambda functions, or ECS tasks), the most secure practice is never to use static credentials. Instead, use IAM Roles.

IAM Roles allow you to assign temporary, automatically rotated security credentials to the resource via the instance metadata service. The AWS CLI automatically detects and uses these credentials without them ever being stored on the disk or in environment variables.

How it Works:

  1. An EC2 instance is launched with an associated IAM Role.
  2. The CLI running on that instance queries the Instance Metadata Service (IMDS) for temporary credentials.
  3. The CLI uses these temporary credentials for all subsequent API calls.

This eliminates the risk associated with long-lived access keys entirely.

4. Utilizing the Credential Process and SSO

Modern credential management increasingly relies on external authentication providers, often integrated via the credential_process configuration.

AWS SSO (Single Sign-On)

AWS SSO provides a unified way to manage access across multiple accounts and roles using existing identity providers (IdPs). The AWS CLI integrates seamlessly with SSO, abstracting the management of temporary session tokens.

To start using SSO, you first execute the login command:

aws sso login --profile <profile-name>

This opens a browser window for authentication. Once successful, the CLI stores the necessary session tokens, often utilizing the credential_process mechanism internally to refresh tokens automatically, meaning you don't handle raw secret keys.

Configuring credential_process

You can configure the CLI to call an external tool (like a vault agent or an SSO helper) to fetch credentials dynamically. This is specified in the configuration file:

Example ~/.aws/config:

[profile my-vault-profile]
region = us-west-2
credential_process = /usr/local/bin/my-vault-cli get-aws-creds --profile my-vault-profile

This method is crucial when integrating with secrets management tools like HashiCorp Vault.

Best Practices Summary and Checklist

To maximize the security of your AWS CLI operations, adhere to these core principles:

  • Principle of Least Privilege: Ensure all IAM users and roles have only the permissions strictly necessary to perform their jobs.
  • Prefer Roles over Keys: Always use IAM Roles (Instance Profiles) when operating within AWS infrastructure.
  • Use SSO: For human interactive use, leverage AWS SSO to manage access to multiple accounts.
  • Never Hardcode Keys: Avoid putting Access Keys directly into scripts, source code, or command history.
  • Protect Credentials File: Restrict filesystem permissions (chmod 600) on ~/.aws/credentials.
  • Rotate Keys Regularly: If static keys must be used, enforce a strict rotation schedule.

By prioritizing dynamic credential acquisition methods like IAM Roles and SSO over static access keys stored on disk, you significantly reduce the attack surface associated with your AWS CLI usage.