cis-ubuntu2004-v300-6-2-3-7

DevOps & Security

Ensure rsyslog is not configured to receive logs from a remote client

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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-v300-6-2-3-7/SKILL.md

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6.2.3.7 Ensure rsyslog is not configured to receive logs from a remote client (Automated)

Profile

Level 1 - Server
Level 1 - Workstation

Description

rsyslog supports the ability to receive messages from remote hosts, thus acting as a log server. Clients should not receive data from other hosts.

Rationale

If a client is configured to also receive data, thus turning it into a server, the client system is acting outside its operational boundary.

Audit Procedure

Command Line

Unless the system's primary function is to serve as a logfile server, run the following script to review the rsyslog configuration and verify that the system is not configured to accept incoming logs.

advanced format:

# grep -P -- '^\h*module\(load="imtcp"\)|^\h*input\(type="imtcp" port="514"\)' /etc/rsyslog.conf /etc/rsyslog.d/*.conf
# grep -P -- '^\h*module\(load="imudp"\)|^\h*input\(type="imudp" port="514"\)' /etc/rsyslog.conf /etc/rsyslog.d/*.conf

No output expected.

obsolete legacy format:

# grep  -P -- '(^\$ModLoad imtcp|^\$InputTCPServerRun)' /etc/rsyslog.conf /etc/rsyslog.d/*.conf
# grep  -P -- '(^\$ModLoad imudp|^\$UDPServerRun)' /etc/rsyslog.conf /etc/rsyslog.d/*.conf

Expected Result

No output expected for any of the above commands.

Remediation

Command Line

Unless the system's primary function is to serve as a logfile server, modify the files returned by the Audit Procedure and remove the specific lines highlighted by the audit. Verify none of the following entries are present in the rsyslog configuration.

advanced format:

# module(load="imtcp")
# input(type="imtcp" port="514")
# module(load="imudp")
# input(type="imudp" port="514")

Note: obsolete legacy - previously known as the legacy format. This format is obsolete and should not be used when writing new configurations. It was aimed at small additions to the original sysklogd format and has been replaced due to its limitations.

Reload the service:

# systemctl reload-or-restart rsyslog

Default Value

Not configured to receive remote logs by default.

References

NIST SP 800-53 Rev. 5: AU-2, AU-7, AU-12, CM-6
https://www.rsyslog.com/doc/index.html
https://www.rsyslog.com/doc/configuration/conf_formats.html

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software
v7	9.2 Ensure Only Approved Ports, Protocols and Services Are Running

MITRE ATT&CK Mappings

Techniques / Sub-techniques	Tactics	Mitigations
T1070, T1070.002, T1562, T1562.006	TA0005, TA0040	M1029