4.3.2 Ensure sudo commands use pty

Information

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

Attackers can run a malicious program using sudo which would fork a background process that remains even when the main program has finished executing.

Solution

Edit the file /etc/sudoers with visudo or a file in /etc/sudoers.d/ with visudo -f <

PATH_TO_FILE

> and add the following line:

Defaults use_pty

Note:

- sudo will read each file in /etc/sudoers.d skipping file names that end in ~ or contain a character to avoid causing problems with package manager or editor temporary/backup files.
- Files are parsed in sorted lexical order. That is, /etc/sudoers.d/01_first will be parsed before /etc/sudoers.d/10_second
- Be aware that because the sorting is lexical, not numeric, /etc/sudoers.d/1_whoops would be loaded after /etc/sudoers.d/10_second
- Using a consistent number of leading zeroes in the file names can be used to avoid such problems.

Impact:

WARNING: Editing the sudo configuration incorrectly can cause sudo to stop functioning. Always use visudo to modify sudo configuration files.

See Also

https://workbench.cisecurity.org/benchmarks/15964