SSH (Secure Socket Shell), which is typically called Secure Shell, is a unique network protocol that leverages public-key cryptography to allow authorized users to access a computer remotely or another device through access keys, namely SSH Keys. Since these SSH keys are used to access the sensitive resource and perform highly privileged or critical activities, therefore it very imperative to manage SSH keys as the other sensitive credentials are managed.
In Linux and UNIX, SSH keys are standard and are used frequently, but that doesn’t mean you cannot use them in the windows system; they are also used in Windows systems too.
Keep on reading for a detailed overview of SSH key management that will also cover topics like SSH security and authentication, how SSH keys work, the risk involved and benefits offered. At the same time, you consider with SSH keys, and strategies to improve SSH security and key management.
SSH key Security Authentication
The Secure Shell, and the public-key cryptography (two key usages: one private, and one public) that SSH keys use, is intended to offer a robust, encrypted verification and communication between the remote computer and the user.
SSH Technology runs on the client-server model and offers a perfect way to access remote devices over the networks that are not secured, e.g., internet. Typically, the technology is used by the administrators for several following included functions:
- Remote computers/servers log in for support and maintenance
- Transfer of files from computer to computer
- Execution of commands remotely
- Offer support and updates
In the present times, one of the first Internet remote login protocols is Telnet, and it has been in usage since the 1960s. But, it has mainly been supplanted by SSH, owing to the following enhanced security features protocol.
Benefits of SSH Key Authentication
Usually, IT Teams use SSH keys for automating secure access to servers, evading the need to enter login details manually. The best part is that the SSH network protocol encrypts all traffic emerging between the client and the server while in transit. This implies that anyone who is trying to pry on the traffic, for example, by packet sniffing methods—will not allow access to the unauthenticated users who intend to decrypt transmitted data.
For the brute force attacks, SSH is defiant and aids in having protection against specific attack vectors that are being used to acquire access to remote machines. Encryption provided by the public keys guarantees that passwords are not sent over the network, providing an additional layer of security. And hence, It makes the SSH keys one reliable and excellent way to stay compliant and secure with various regulations, only if you are using the best practice to generate, store, manage, and remove them.
Because of the huge number of SSH keys that are in use or even exist across an enterprise at any time, SSH key management software is significantly able to lower to overhead and risk of manually managing and updating keys.
How to Generate SSH keys?
The one thing that goes forever with SSH keys generation is that they are always generated in pairs— consisting of one ‘public’ and one ‘private’ SSH key. Then, these keys are paired by using robust encryption algorithms, and even if you know the public key, it will make it infeasible to guess or ‘fake’ a private key. Private Keys should be kept a secret by the authorized user who wishes to acquire access to a system, whereas public keys are typically shared freely.
Generally, the SSH keys are generated by the user who is trying to enter the passphrase, or any other information and public and private keys will be made from the phrases of a few words.
How to Access SSH Key?
A remote computer recognizes itself to a user by making the use of its public Key. So, when a user tries to connect with the remote computer, it creates a “challenge’’ obtained from the public key, for which someone who has a paired private key that would correctly decrypt and respond accordingly. The remote computer offers you access when the challenge is answered correctly.
In almost every case, keys generation, public key sharing, challenges issuing, responding to them, and acquiring access are all managed by SSH software that makes the process hugely transparent to the end-user.
What Security & Operational Risk when SSH Key Sprawled?
Fake SSH crucial sprawl put the organization on a vast cyber risk, particularly considering the situation where they can grant a high level of privileged access such as root.
More than 400 IT security professionals were subjected to conduct dimensional research, where over 90% of them reported that respondents lacked a considerable and accurate SSH keys inventory. Besides, 2/3 of the cybersecurity professionals affirmed that they do not rotate their SSH keys actively.
Typically, with 50-200 SSH keys per server, organizations may be growing with more than a million SSH keys. Not to mention that the SSH keys, which are long-forgotten or are dormant, they can provide a secret passage to the hackers to penetrate through the servers. And, in case the hacker has managed to make his way through the server, he would make his move laterally and find more hidden keys.
There exist some privileged credentials, and with them, if the organizations are dependent on manual processes, there are chances to reuse the passphrase across other SSH keys, or the same public SSH key can be used. This implies that only one compromised key is enough to penetrate multiple servers.
6 SSH Key Security Best Practices
With any other security protocols, it is vital to keep the standard strong and include the best practice for SSH network protocols and keys. For government organizations, NISTIR7966 offers guidance regarding all the businesses and auditors in terms of security controls for the implementation of SSH. The NIST recommendation mostly lays emphasis on SSH discovery, usage, rotation, and monitoring.
Even in the most complex environment, the rotation of manual SSH is infeasible. For example, you are able to recognize the accounts that are created to use SSH keys; it enables you to manually scan through authorized keys file in the secretive SSH user folder. But, this doesn’t help you to recognize who has the private key that matches the public key in the data.
Organizations that identify the risks created by SSH crucial sprawl and take practical cybersecurity measures to use a dedicated SSH key management can perform different rotations.
Or, by privileged password management (PPM) solution to produce unique key pairs for every system present and then carry out the process of frequent rotations. Surprisingly, the automated solutions simplifies the process of SSH key generation and rotation, removing the sprawl of SSH key, and make sure that SSH key enables productivity without having to compromise with the security:
To stiffen the security controls for SSH Keys, you can go forward and apply the following six best practices:
- Discover all SSH Keys and Bring under Active Management
If you wish to eliminate the sprawl for an SSH key and want to properly asses SSH security risks, then the first step is to discover and inventory all the SSH keys, and then you can take control of all the keys. Also, it is the perfect moment to determine who should be using the various keys and how they would be used.
2. Ensure SSH Keys Are Associated With a Single Individual
Instead of tying SSH keys to just an account that is typically accessed by multiple users, it is better to tie to an individual. Well, doing so will ensure an effective SSH audit trail and a direct overview.
3. Enforce Minimal Levels of User Rights through PoLP
Principle of least privilege (PoLP) should be applied to enforce minimal levels of user rights such as while you tie SSH keys to coarse areas of remote devices so that users have limited access privileges to the necessary systems. Well, this limits the possible fallout from the exploitation of SSH keys.
4. Stay Attentive to SSH Key Rotation
Implementing meticulous SSH Key rotation enforce users to generate keys regularly and cut the users of the same passphrases across multiple accounts or iterations. These actions help protect the organization from password reuse attacks. In organizations with a large SSH key estate, this can only be feasibly performed via an automated solution.
5. Eliminate Hardcoded SSH Keys
SSH Keys are one of the many types of credentials that can be embedded within code, such as in applications and files. This practice creates dangerous backdoors for malware and hackers to exploit. Embedded keys that use simple or default passphrases may be vulnerable to password-guessing and other attacks. Therefore, an important piece of SSH security is to uncover and eliminate embedded SSH keys and bring them under centralized management.
6. Audit All Privileged Session Activity
Any privileged session started via an SSH Key authentication (or other means) should be recorded and audited to meet both cybersecurity and regulatory needs. Privileged session management activities can entail capturing keystrokes and screens (allowing for live view and playback). Ideally, you also layer on the ability to control (pauses or terminate) privileged sessions in real-time to maintain strong oversight and a short leash over-privileged activity.