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IBM z/OS must implement DoD-approved encryption to protect the confidentiality of remote access sessions.


Overview

Finding ID Version Rule ID IA Controls Severity
V-223538 ACF2-OS-000020 SV-223538r533198_rule High
Description
Without cryptographic integrity protections, information can be altered by unauthorized users without detection.
STIG Date
IBM z/OS ACF2 Security Technical Implementation Guide 2022-06-22

Details

Check Text ( C-25211r504669_chk )
Locate the SSH daemon configuration file, which may be found in /etc/ssh/ directory.

Alternately:

From UNIX System Services ISPF Shell navigate to ribbon select tools.

Select option 1 - Work with Processes.

If SSH Daemon is not active, this is not a finding.

Examine SSH daemon configuration file.
sshd_config

If there are no "Ciphers" line or the ciphers list contains any cipher not starting with "3des" or "aes", this is a finding.

If the MACs line is not configured to "hmac-sha1" or greater, this is a finding.

Examine the z/OS-specific sshd server system-wide configuration.

zos_sshd_config

If any of the following is untrue, this is a finding.

FIPSMODE=YES
CiphersSource=ICSF
MACsSource=ICSF
Fix Text (F-25199r504670_fix)
Edit the SSH daemon configuration and remove any ciphers not starting with "3des" or "aes". If necessary, add a "Ciphers" line using FIPS 140-2 compliant algorithms.

Configure for message authentication to MACs "hmac-sha1" or greater.

Edit the z/OS-specific sshd server system-wide configuration file configuration as follows:
FIPSMODE=YES
CiphersSource=ICSF
MACsSource=ICSF