IBM z/OS SSH daemon must be configured to use a FIPS 140-2 compliant cryptographic algorithm.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-223589	ACF2-SH-000050	SV-223589r918616_rule		High

Description
Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session. Remote access is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Encryption provides a means to secure the remote connection to prevent unauthorized access to the data traversing the remote access connection (e.g., RDP), thereby providing a degree of confidentiality. The encryption strength of a mechanism is selected based on the security categorization of the information. Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000120-GPOS-00061

Description

Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session. Remote access is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Encryption provides a means to secure the remote connection to prevent unauthorized access to the data traversing the remote access connection (e.g., RDP), thereby providing a degree of confidentiality. The encryption strength of a mechanism is selected based on the security categorization of the information. Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000120-GPOS-00061

STIG	Date
IBM z/OS ACF2 Security Technical Implementation Guide	2023-09-19

Details

Check Text ( C-25262r504740_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 lines 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

Check Text ( C-25262r504740_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 lines 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-25250r504741_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