cis-ubuntu1604-v200-6-2-7

DevOps & Security

Ensure users' dot files are not group or world writable

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Prompt to paste

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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-v200-6-2-7/SKILL.md

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First, summarize what it does, its dependencies, license status if identifiable, and any risks. Show the exact files you propose to add under .agents/skills/cis-ubuntu1604-v200-6-2-7/. Do not write files or run scripts until I approve.

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CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 6.2.7

Profile

Level: 1 - Server
Level: 1 - Workstation
Assessment Status: Automated

Description

While the system administrator can establish secure permissions for users' "dot" files, the users can easily override these.

Rationale

Group or world-writable user configuration files may enable malicious users to steal or modify other users' data or to gain another user's system privileges.

Audit Procedure

Command Line

Run the following script and verify no results are returned:

#!/bin/bash
awk -F: '($1!~/(halt|sync|shutdown)/ && $7!~/^(\/usr)?\/sbin\/nologin(\/)?\$/
&& $7!~/(\/usr)?\/bin\/false(\/)?\$/) { print $1 " " $6 }' /etc/passwd | while
read -r user dir; do
  if [ -d "$dir" ]; then
    for file in "$dir"/.*; do
      if [ ! -h "$file" ] && [ -f "$file" ]; then
        fileperm=$(stat -L -c "%A" "$file")
        if [ "$(echo "$fileperm" | cut -c6)" != "-" ] || [ "$(echo
"$fileperm" | cut -c9)" != "-" ]; then
          echo "User: \"$user\" file: \"$file\" has permissions:
\"$fileperm\""
        fi
      fi
    done
  fi
done

Expected Result

No output should be returned.

Remediation

Command Line

Making global modifications to users' files without alerting the user community can result in unexpected outages and unhappy users. Therefore, it is recommended that a monitoring policy be established to report user dot file permissions and determine the action to be taken in accordance with site policy.

The following script will remove excessive permissions on dot files within interactive users' home directories.

#!/bin/bash
awk -F: '($1!~/(halt|sync|shutdown)/ && $7!~/^(\/usr)?\/sbin\/nologin(\/)?\$/
&& $7!~/(\/usr)?\/bin\/false(\/)?\$/) { print $1 " " $6 }' | while read -r
user dir; do
  if [ -d "$dir" ]; then
    for file in "$dir"/.*; do
      if [ ! -h "$file" ] && [ -f "$file" ]; then
        fileperm=$(stat -L -c "%A" "$file")
        if [ "$(echo "$fileperm" | cut -c6)" != "-" ] || [ "$(echo
"$fileperm" | cut -c9)" != "-" ]; then
          chmod go-w "$file"
        fi
      fi
    done
  fi
done

Default Value

N/A

References

N/A

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v7	14.6 Protect Information through Access Control ListsProtect all information stored on systems with file system, network share, claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities.