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cis-ubuntu1604-v200-5-3-4

DevOps & Security
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Ensure SSH Protocol is set to 2

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_16.04_LTS_Benchmark_v2.0.0/cis-ubuntu1604-v200-5-3-4/SKILL.md

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CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.4

Description

SSH supports two different and incompatible protocols: SSH1 and SSH2. SSH1 was the original protocol and was subject to security issues. SSH2 is more advanced and secure.

Rationale

SSH v1 suffers from insecurities that do not affect SSH v2.

Audit Procedure

Command Line

Run the following command and verify that output matches:

sshd -T -C user=root -C host="$(hostname)" -C addr="$(grep $(hostname) /etc/hosts | awk '{print $1}')" | grep '^\s*protocol'

Expected Result

protocol 2

Run the following command and verify the output:

grep -Ei '^\s*Protocol\s+[^2].*
#x27; /etc/ssh/sshd_config

Nothing should be returned.

Remediation

Command Line

Edit the /etc/ssh/sshd_config file to set the parameter as follows:

Protocol 2

Default Value

Protocol 2

References

  1. SSHD_CONFIG(5)

CIS Controls

Version 7

9.2 Ensure Only Approved Ports, Protocols and Services Are Running - Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system.

Profile Applicability

  • Level 1 - Server
  • Level 1 - Workstation

Assessment Status

Automated