cyberstrikeus CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.18
Description
The LoginGraceTime parameter specifies the time allowed for successful authentication to the SSH server. The longer the Grace period is the more open unauthenticated connections can exist. Like other session controls in this session the Grace Period should be limited to appropriate organizational limits to ensure the service is available for needed access.
Rationale
Setting the LoginGraceTime parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. It will also limit the number of concurrent unauthenticated connections. While the recommended setting is 60 seconds (1 Minute), set the number based on site policy.
Audit Procedure
Command Line
Run the following command and verify that output LoginGraceTime is between 1 and 60 seconds or 1m:
sshd -T -C user=root -C host="$(hostname)" -C addr="$(grep $(hostname) /etc/hosts | awk '{print $1}')" | grep logingracetime
Expected Result
logingracetime 60
Run the following command and verify the output:
grep -Ei '^\s*LoginGraceTime\s+(0|6[1-9]|[7-9][0-9]|[1-9][0-9][0-9]+|[^1]m)' /etc/ssh/sshd_config
Nothing should be returned.
Remediation
Command Line
Edit the /etc/ssh/sshd_config file to set the parameter as follows:
LoginGraceTime 60
Default Value
LoginGraceTime 2m
References
- SSHD_CONFIG(5)
CIS Controls
Version 7
5.1 Establish Secure Configurations - Maintain documented, standard security configuration standards for all authorized operating systems and software.
Profile Applicability
- Level 1 - Server
- Level 1 - Workstation
Assessment Status
Automated