cis-ubuntu2004-v300-5-1-19

DevOps & Security

Ensure sshd PermitEmptyPasswords is disabled

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_20.04_LTS_Benchmark_v3.0.0/cis-ubuntu2004-v300-5-1-19/SKILL.md

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Ensure sshd PermitEmptyPasswords is disabled (Automated)

Profile Applicability

Level 1 - Server
Level 1 - Workstation

Description

The PermitEmptyPasswords parameter specifies if the SSH server allows login to accounts with empty password strings.

Rationale

Disallowing remote shell access to accounts that have an empty password reduces the probability of unauthorized access to the system.

Audit Procedure

Command Line

Run the following command to verify PermitEmptyPasswords is set to no:

# sshd -T | grep permitemptypasswords

permitemptypasswords no

IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block. Example additional audit needed for a match block for the user sshuser:

# sshd -T -C user=sshuser | grep permitemptypasswords

Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain)

Expected Result

permitemptypasswords no

Remediation

Command Line

Edit /etc/ssh/sshd_config and set the PermitEmptyPasswords parameter to no above any Include and Match entries as follows:

PermitEmptyPasswords no

Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location.

Default Value

PermitEmptyPasswords no

References

SSHD_CONFIG(5)
NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5

CIS Controls

v8 - 5.2 Use Unique Passwords Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a 14-character password for accounts not using MFA.

v7 - 4.4 Use Unique Passwords Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that system.

MITRE ATT&CK Mappings: T1021 | TA0008 | M1042