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WN25-SH-000050 Windows Server 2025 OpenSSH must force a frequent session key renegotiation for SSH connections to the server.

DISA STIG library V1R4
All changes in this version
first version loaded CAT II

Maps to AC-17(2), SC-8, SC-8(1) via CCI-000068, CCI-002418, CCI-002421

Title

Windows Server 2025 OpenSSH must force a frequent session key renegotiation for SSH connections to the server.

Control

If OpenSSH is not installed on the system, this requirement is NA. Verify the OpenSSH server is configured to force frequent session key renegotiation with the following command: C:\ > Get-Content "$env:ProgramData\ssh\sshd_config" | Select-String -Pattern '^\s*RekeyLimit' RekeyLimit 1G 1h If "RekeyLimit" does not have a maximum data amount and maximum time defined, is missing, or is commented out, this is a finding.

Discussion

Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read or altered. This requirement applies to both internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification. Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa. Session key regeneration limits the chances of a session key becoming compromised. Satisfies: SRG-OS-000423-GPOS-00187, SRG-OS-000033-GPOS-00014, SRG-OS-000424-GPOS-00189

Related controls

CCI-000068, CCI-002418, CCI-002421

Fix

To configure the system, add or modify the following line in the "$env:ProgramData/ssh/sshd_config" file. An example configuration line is: RekeyLimit 1G 1h Restart the OpenSSH service for the settings to take effect.