| name | CIS Ubuntu 14.04 LTS - 6.1.1 Audit system file permissions |
| description | Audit system file permissions using dpkg --verify to detect unauthorized changes |
| category | cis-os-hardening |
| version | 2.1.0 |
| author | cyberstrike-official |
| tags | ["cis","ubuntu","ubuntu-14.04","level-2","not-scored","file-permissions"] |
| cis_id | 6.1.1 |
| cis_benchmark | CIS Ubuntu Linux 14.04 LTS Benchmark v2.1.0 |
| tech_stack | ["ubuntu","linux"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | low |
6.1.1 Audit system file permissions (Not Scored)
Profile Applicability
- Level 2 - Server
- Level 2 - Workstation
Description
The Debian package manager has a number of useful options. One of these, the --verify option, can be used to verify that system packages are correctly installed. The --verify option can be used to verify a particular package or to verify all system packages. If no output is returned, the package is installed correctly. The following table describes the meaning of output from the verify option:
| Code | Meaning |
|---|
| S | File size differs. |
| M | File mode differs (includes permissions and file type). |
| 5 | The MD5 checksum differs. |
| D | The major and minor version numbers differ on a device file. |
| L | A mismatch occurs in a link. |
| U | The file ownership differs. |
| G | The file group owner differs. |
| T | The file time (mtime) differs. |
The dpkg -S command can be used to determine which package a particular file belongs to. For example the following commands determines which package the /bin/bash file belongs to:
bash: /bin/bash
To verify the settings for the package that controls the /bin/bash file, run the following:
??5?????? c /etc/bash.bashrc
Rationale
It is important to confirm that packaged system files and directories are maintained with the permissions they were intended to have from the OS vendor.
Audit Procedure
Run the following to review all installed packages. Note that this may be very time consuming and may be best scheduled via the cron utility. It is recommended that the output of this command be redirected to a file that can be reviewed later.
dpkg --verify > <filename>
Expected Result
Review the output file for any discrepancies. No unexpected permission changes should be present.
Remediation
