9 SSH Key Management Best Practices You Need to Know (2024)

In today’s distributed workplace model, privileged remote access to servers and systems is essential to ensure smooth operations. Secure Shell (SSH) keys play a pivotal role in facilitating this access securely. IT teams worldwide use SSH keys daily for remote system administration, support and maintenance, and file transfers. Because SSH keys are so widely used and grant secure root-level access to systems, it is vital to make sure they are appropriately managed and protected.

Since SSH keys can be easily generated and do not expire, they continue to grow exponentially, with enterprises accumulating millions of SSH keys across thousands of servers. Managing such large volumes of SSH keys is a significant challenge for IT teams. When left unmanaged, there is a high risk of attackers stealing or misusing these SSH keys—to gain access to critical resources, such as production servers, firewalls, and databases—and move laterally, undetected. In addition to the security risk, unmanaged SSH keys can lead to policy violations, failed audits, and massive regulatory penalties.

To ensure robust protection of your infrastructure and continuous regulatory compliance, here are the best practices to follow for effective SSH key management:

1. Discovery and Inventory

Scan and discover all SSH keys spread across hybrid and multi-cloud infrastructures – like servers, client devices, cloud instances, and VMs – on an on-demand basis. Create and maintain an accurate and up-to-date inventory of SSH keys, including user and host keys to gain centralized control and simplify management. Automate discovery so you don’t overlook any inactive and rogue keys. Automated discovery also eliminates the manual overhead of searching for SSH keys across complex environments, which is inefficient and often error-prone.

2. Gain Holistic Visibility

As SSH keys are large in number and often generated and configured on an ad-hoc basis, maintaining full visibility of all the keys is critical to reduce key sprawl and prevent key theft or misuse. Establish a centralized view of all SSH keys in the inventory. Map each key’s trust relationship to associated users, hosts, servers, and service accounts. Understanding the key’s trust relationships is critical for ensuring successful key rotations on a periodic basis. Gain insight into the crypto standards, such as key algorithms and bit lengths to detect and invalidate outdated and vulnerable keys. This level of granular visibility helps monitor and manage SSH keys at scale confidently.

3. Monitor Key Usage

With SSH keys granting root access and guarding valuable data, it is important to have insight and complete control over their access privileges. Monitor the configurations, usage, and age of SSH keys continuously. Effective monitoring helps identify and remove inactive or rogue keys. Also, review key authentication logs periodically and set up alerts for unusual or unauthorized access attempts. Timely detection of anomalies can prevent key compromises that can, in turn, cause security breaches.

4. Automate Key Lifecycle Management

Given the massive number of SSH keys that enterprises have today, automation can help significantly lower the overhead and risk of manual key lifecycle management. Fully automate SSH key lifecycle processes, including key requests, roll outs, rotations, and removal. Automation can radically simplify processes, such as deleting unused, unauthorized, and weak keys and regenerating new keys at scale. It also streamlines complex processes, such as key rotation, ensuring timely rotation and preventing key compromises. Leverage IAM and DevOps integrations provided by automation solutions to streamline SSH key creation, configurations, and access provisioning.

5. Enforce Policies and Governance

All keys are not created equal. Some protect access to mission-critical application systems, while others protect access to less-important testing environments. Restrict and control access to systems by enforcing appropriate policies. Group keys based on functionality and map them to required policies. Assign ownership of keys to enforce accountability. Implement role-based access control (RBAC) for managing SSH keys to provide users and groups with conditional access and rest assured that no user has more privileges than they should ideally have. This helps reduce the risk of privilege sprawl and unauthorized access.

Further, set policies around key generation, approved crypto standards, key rotations, and time-bound access. Enforcing these policies helps standardize processes, simplify management and ensure compliance. Conduct regular audits and reviews of SSH key configurations and access permissions. Verify that all keys are accounted for and adhere to the organization’s security policies to ensure compliance with regulatory standards.

6. Generate Strong Keys

When creating SSH keys, choose strong cryptographic standards. Opt for algorithms such as RSA or Ed25519. While RSA typically has larger key sizes (2048 or 4096 bits), Ed25519 has a smaller key size of 256 bits. Nonetheless, both algorithms are considered highly secure and resilient against brute-force attacks. Avoid using algorithms like DSA that are considered vulnerable.

7. Rotate Keys Regularly

Just like passwords, SSH keys should be rotated periodically. Key rotation helps minimize the window of opportunity for attackers to misuse compromised or outdated SSH keys. Key rotation also enables better access control by ensuring that access privileges are regularly reviewed and updated. This helps in revoking access for employees who have left the organization or whose roles have changed, minimizing the risk of insider threats. Define a schedule to replace SSH keys at regular intervals, such as every 60 or 45 days. As mentioned earlier, automate key rotation to ensure the existing SSH keys are replaced with newly generated keys across all shared systems.

8. Limit Shared Private Key Usage

Be cautious of shared private keys. When a single private key is shared between multiple servers, key rotation gets complicated. In such cases, the key pairs must be generated and distributed to all dependent servers to ensure uninterrupted access. As a best practice, avoid using the same SSH key across multiple servers or granting overly broad permissions. Instead, create separate keys for different environments and users to minimize the impact of a compromised key.

9. Use Passphrases:

Implement passphrases for SSH keys. Passphrases encrypt the private key, adding an additional layer of security. This helps prevent malicious actors from deciphering private keys when a user device is lost or stolen. Ensure that users use passphrases that are complex and hard to crack.

As SSH keys, by default, grant privileged access to mission-critical systems, they must be carefully controlled and protected as you would other types of access credentials. Effective SSH key management entailing discovery, inventory, automation, and policy control should become integral to your Identity and Access Management (IAM) Strategy for ensuring security and compliance. By following the above-discussed best practices, you can take control of your SSH keys, mitigate associated risks and vulnerabilities, and maintain the integrity and security of your infrastructure.

To learn more about how AppViewX helps organizations gain visibility and control of SSH keys, contact us today or visit: https://www.appviewx.com/solutions/ssh-access-control/.