All public directories must be owned by root to prevent unauthorized and unintended information transferred via shared system resources.

From Canonical Ubuntu 16.04 LTS Security Technical Implementation Guide

Part of SRG-OS-000138-GPOS-00069

Associated with: CCI-001090

SV-90191r1_rule All public directories must be owned by root to prevent unauthorized and unintended information transferred via shared system resources.

Vulnerability discussion

Preventing unauthorized information transfers mitigates the risk of information, including encrypted representations of information, produced by the actions of prior users/roles (or the actions of processes acting on behalf of prior users/roles) from being available to any current users/roles (or current processes) that obtain access to shared system resources (e.g., registers, main memory, hard disks) after those resources have been released back to information systems. The control of information in shared resources is also commonly referred to as object reuse and residual information protection.This requirement generally applies to the design of an information technology product, but it can also apply to the configuration of particular information system components that are, or use, such products. This can be verified by acceptance/validation processes in DoD or other government agencies.There may be shared resources with configurable protections (e.g., files in storage) that may be assessed on specific information system components.

Check content

Verify that all public directories are owned by root to prevent unauthorized and unintended information transferred via shared system resources. Check to see that all public directories have the public sticky bit set by running the following command: # sudo find / -type d -perm -0002 -exec ls -lLd {} \; drwxrwxrwxt 7 root root 4096 Jul 26 11:19 /tmp If any of the returned directories are not owned by root, this is a finding.

Fix text

Configure all public directories to be owned by root to prevent unauthorized and unintended information transferred via shared system resources. Set the owner of all public directories as root using the command, replace "[Public Directory]" with any directory path not owned by root: # sudo chown root [Public Directory]

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