cis-ubuntu1804-v220-4-3-2

DevOps & Security

Ensure sudo commands use pty

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_18.04_LTS_Benchmark_v2.2.0/cis-ubuntu1804-v220-4-3-2/SKILL.md

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CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 4.3.2

Profile Applicability

Level 1 - Server
Level 1 - Workstation

Description

sudo can be configured to run only from a pseudo terminal (pseudo-pty).

Rationale

Attackers can run a malicious program using sudo which forks a background process that remains on the user's terminal device even after the main program has finished executing. This can be used to intercept user input including passwords. By configuring sudo to use a pseudo terminal, this attack is no longer possible.

Audit Procedure

Command Line

Run the following command to verify that sudo uses a pseudo terminal:

grep -rPi '^\h*Defaults\h+([^#\n\r]+,)?use_pty(,\h*\h+\h*)*\h*(#.*)?#x27; /etc/sudoers /etc/sudoers.d/

Expected Result

Defaults use_pty

Remediation

Command Line

Edit the file /etc/sudoers or a file in /etc/sudoers.d/ with visudo and add the following line:

Defaults use_pty

References

NIST SP 800-53 Rev. 5: AC-6(1)

CIS Controls

v8 - 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts.

v7 - 4.3 Ensure the Use of Dedicated Administrative Accounts.

Profile Applicability

Level 1 - Server
Level 1 - Workstation

Assessment Status

Automated