Introduction to Securing SSH with FIDO2 and Physical Security Keys
Securing SSH connections is crucial for preventing unauthorized access to Linux systems. Recently, there has been an increase in attacks targeting SSH, including CVE-2022-42010, which allows attackers to bypass authentication using a malicious SSH server. To mitigate such risks, using FIDO2 and physical security keys can significantly enhance the security of SSH connections. In this blog post, we will explore how to secure SSH with FIDO2 and physical security keys on Fedora.
Understanding FIDO2 and Physical Security Keys
FIDO2 is an open standard for authentication that uses public key cryptography and a physical security key to verify user identities. Physical security keys, such as YubiKeys, are small devices that store cryptographic keys and provide an additional layer of security when authenticating to systems. By using FIDO2 and physical security keys, users can ensure that even if their passwords are compromised, attackers will not be able to access their systems without the physical security key.
Configuring FIDO2 on Fedora
To configure FIDO2 on Fedora, you will need to install the required packages and configure the system to use the physical security key. The following steps outline the process:
- Install the required packages:
sudo dnf install libfido2 pam-u2f - Plug in your physical security key and verify that it is recognized by the system:
lsusb | grep -i yubi - Configure PAM to use the physical security key:
sudo pam-u2f-auth -u <username> -p /dev/null -t u2f -a pam
sudo authselect select sssd with-fido2 --force
- Update the SSH configuration to use FIDO2:
sudo echo "AuthenticationMethods publickey,fido2" >> /etc/ssh/sshd_config
sudo systemctl restart sshd
Enrolling FIDO2 Devices
To enroll a FIDO2 device, you will need to use the pamu2f-tool command. The following steps outline the process:
- Initialize the FIDO2 device:
sudo pamu2f-tool -u <username> -t u2f -a pam - Create a new credential:
sudo pamu2f-tool -u <username> -t u2f -c -a pam - Register the credential with the system:
sudo pamu2f-tool -u <username> -t u2f -r -a pam
MITRE ATT&CK Techniques and Recent CVEs
According to the MITRE ATT&CK framework, using FIDO2 and physical security keys can help mitigate several techniques used by attackers, including:
- T1110: Brute Force
- T1111: Credentials in Files
- T1550: Use Alternate Authentication Material
Recent CVEs, such as CVE-2022-42010, highlight the importance of securing SSH connections. By using FIDO2 and physical security keys, users can ensure that even if their passwords are compromised, attackers will not be able to access their systems without the physical security key.
Conclusion
Securing SSH connections with FIDO2 and physical security keys is an effective way to prevent unauthorized access to Linux systems. By following the steps outlined in this blog post, users can configure FIDO2 on Fedora and enroll their physical security keys to enhance the security of their systems. As highlighted by recent CVEs and MITRE ATT&CK techniques, using FIDO2 and physical security keys can help mitigate several techniques used by attackers.