The Photon operating system must implement only approved ciphers to protect the integrity of remote access sessions.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
high	V-258835	SRG-OS-000250-GPOS-00093	PHTN-40-000079	SV-258835r991554_rule	2024-07-11	2

Description
Without cryptographic integrity protections, information can be altered by unauthorized users without detection. Remote access (e.g., RDP) is access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

Description

Without cryptographic integrity protections, information can be altered by unauthorized users without detection. Remote access (e.g., RDP) is access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

ℹ️ Check
At the command line, run the following command to verify the running configuration of sshd: # sshd -T\|&grep -i Ciphers Expected result: ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr If the output matches the ciphers in the expected result or a subset thereof, this is not a finding. If the ciphers in the output contain any ciphers not listed in the expected result, this is a finding.

ℹ️ Check

At the command line, run the following command to verify the running configuration of sshd: # sshd -T|&grep -i Ciphers Expected result: ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr If the output matches the ciphers in the expected result or a subset thereof, this is not a finding. If the ciphers in the output contain any ciphers not listed in the expected result, this is a finding.

✔️ Fix
Navigate to and open: /etc/ssh/sshd_config Ensure the "Ciphers" line is uncommented and set to the following: Ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr At the command line, run the following command: # systemctl restart sshd.service