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Showing SKILL.md
| name | cis-ubuntu1804-v220-6-1-13 |
| description | Ensure permissions on /etc/shells are configured |
| category | cis-iam |
| version | 2.2.0 |
| author | cyberstrike-official |
| tags | ["cis","ubuntu","linux","ubuntu-18.04","file-permissions"] |
| cis_id | 6.1.13 |
| cis_benchmark | CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 |
| tech_stack | ["ubuntu","linux"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | {} |
/etc/shells is a text file which contains the full pathnames of valid login shells. This file is consulted by chsh and available to be queried by other programs.
It is critical to ensure that the /etc/shells file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions.
Run the following command to verify /etc/shells is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root:
# stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shells
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Run the following commands to remove excess permissions, set owner, and set group on /etc/shells:
# chmod u-x,go-wx /etc/shells
# chown root:root /etc/shells
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)