cyberstrikeus CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 6.2.6
Profile
- Level: 1 - Server
- Level: 1 - Workstation
- Assessment Status: Automated
Description
While the system administrator can establish secure permissions for users' home directories, the users can easily override these.
Rationale
Group or world-writable user home directories 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
echo "User: \"$user\" home directory: \"$dir\" doesn't exist"
else
dirperm=$(stat -L -c "%A" "$dir")
if [ "$(echo "$dirperm" | cut -c6)" != "-" ] || [ "$(echo "$dirperm" |
cut -c8)" != "-" ] || [ "$(echo "$dirperm" | cut -c9)" != "-" ] || [ "$(echo
"$dirperm" | cut -c10)" != "-" ]; then
echo "User: \"$user\" home directory: \"$dir\" has permissions:
\"$(stat -L -c "%a" "$dir")\""
fi
fi
done
Expected Result
No output should be returned.
Remediation
Command Line
Making global modifications to user home directories 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 file permissions and determine the action to be taken in accordance with site policy.
The following script can be used to remove permissions in excess of 750 from users' home directories:
#!/bin/bash
awk -F: '($1!~/(halt|sync|shutdown)/ && $7!~/^(\/usr)?\/sbin\/nologin(\/)?\$/
&& $7!~/(\/usr)?\/bin\/false(\/)?\$/) {print $6}' /etc/passwd | while read -r
dir; do
if [ -d "$dir" ]; then
dirperm=$(stat -L -c "%A" "$dir")
if [ "$(echo "$dirperm" | cut -c6)" != "-" ] || [ "$(echo "$dirperm" |
cut -c8)" != "-" ] || [ "$(echo "$dirperm" | cut -c9)" != "-" ] || [ "$(echo
"$dirperm" | cut -c10)" != "-" ]; then
chmod g-w,o-rwx "$dir"
fi
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. |