Secure Remote Access to EC2 Instances: AWS SSM Session Manager vs EC2 Instance Connect vs EC2 Instance Connect Endpoint

🚀 Overview

AWS provides multiple options for secure, keyless remote access to EC2 instances without requiring SSH keys, public IPs, or bastion hosts. The three main solutions are:

1. AWS Systems Manager Session Manager (SSM Session Manager)
2. EC2 Instance Connect
3. EC2 Instance Connect Endpoint

Each method has distinct advantages, limitations, and use cases. This guide compares them to help you choose the best option for your needs.

🔍 Feature Comparison

Feature	SSM Session Manager	EC2 Instance Connect	EC2 Instance Connect Endpoint
No Public IP Required	✅ Yes	❌ No (only works with public IPs)	✅ Yes
No SSH Key Management	✅ Yes	✅ Yes	✅ Yes
IAM-Based Access Control	✅ Yes	✅ Yes	✅ Yes
Bastion Host Requirement	✅ Not Needed	✅ Not Needed	✅ Not Needed
AWS Console Access	✅ Yes	✅ Yes	✅ Yes
AWS CLI Access	✅ Yes (aws ssm start-session)	✅ Yes (aws ec2-instance-connect ssh)	✅ Yes (aws ec2-instance-connect ssh)
Works with Private Subnets	✅ Yes (VPC Endpoints or NAT required)	❌ No	✅ Yes (via EC2 Instance Connect Endpoint)
Session Logging & Auditing	✅ Yes (CloudWatch/CloudTrail)	❌ No	❌ No
Supports On-Demand Access	✅ Yes	✅ Yes	✅ Yes

🛠 AWS Systems Manager Session Manager

Key Benefits

• No Public IPs Required - Works with instances inside private subnets.
• No SSH Key Management - Uses IAM-based authentication.
• Session Logging & Auditing - Logs user activity in CloudTrail.
• AWS Console & CLI Integration - Accessible via AWS Console or CLI.
• Supports VPC Endpoints - No need for outbound internet access when using PrivateLink.

How It Works

1. Attach an IAM Role with AmazonSSMManagedInstanceCore policy to the instance.
2. Ensure the instance has SSM Agent installed and running.
3. Use aws ssm start-session or AWS Console to connect.
4. AWS handles authentication and communication securely.

🛠 EC2 Instance Connect

Key Benefits

• No SSH Keys Required - AWS injects temporary keys for authentication.
• Simple to Use - Directly accessible from the AWS Console.
• Ideal for Public Instances - Works with EC2 instances that have public IPs.

How It Works

1. Select the EC2 instance in the AWS Console.
2. Click Connect > EC2 Instance Connect.
3. AWS injects a temporary SSH key and logs you in.

Limitations

• Requires Public IP - Cannot connect to instances in private subnets.
• No CLI Support for Private Instances - CLI access only works for instances with public IPs.

🛠 EC2 Instance Connect Endpoint

Key Benefits

• Works with Private Subnets - Enables SSH access without requiring a public IP.
• IAM-Based Access Control - Uses temporary SSH keys.
• No Bastion Hosts Needed - Connects to instances inside a private VPC securely.
• Works with AWS CLI & Console - Provides a seamless connection experience.

How It Works

1. Deploy an EC2 Instance Connect Endpoint in the same subnet as the target instance.
2. Assign a Security Group to control access.
3. Ensure the instance has EC2 Instance Connect Agent installed and running.
4. Use the AWS Console or CLI to initiate a session.

📚 Choosing the Right Solution

Use Case	Recommended Solution
Access private instances	SSM Session Manager or EC2 Instance Connect Endpoint
Access public instances	EC2 Instance Connect
Audit session activity	SSM Session Manager
No outbound internet access	SSM Session Manager with VPC Endpoints
CLI-based access	SSM Session Manager or EC2 Instance Connect Endpoint
One-time or temporary access	EC2 Instance Connect

📚 Terraform Sample Repository

For a working Terraform example demonstrating all three access methods, check out:

👉 GitHub Repository: AWS SSM Session Manager Terraform Demo
👉 GitHub Repository: EC2 Instance Connect Terraform Demo
👉 GitHub Repository: EC2 Instance Connect Endpoint Terraform Demo

🌟 Summary

• SSM Session Manager - Best for managing private EC2 instances without SSH keys or public IPs, with IAM control and session logging.
• EC2 Instance Connect - Best for ad-hoc connections to public EC2 instances, offering simple browser-based SSH access.
• EC2 Instance Connect Endpoint - Best for secure CLI-based SSH access to private EC2 instances without requiring a bastion host.