Cis Ubuntu1604 V200 1 5 2

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - 1.5.2

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

Address space layout randomization (ASLR) is an exploit mitigation technique which randomly arranges the address space of key data areas of a process.

Rationale

Randomly placing virtual memory regions will make it difficult to write memory page exploits as the memory placement will be consistently shifting.

Audit Procedure

Command Line

Run the following commands and verify output matches:

sysctl kernel.randomize_va_space

Expected output: kernel.randomize_va_space = 2

grep -Es "^\s*kernel\.randomize_va_space\s*=\s*([0-1]|[3-9]|[1-9][0-9]+)" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /run/sysctl.d/*.conf

Nothing should be returned.

Expected Result

kernel.randomize_va_space should be set to 2. No overriding configurations should exist in sysctl configuration files.

Remediation

Command Line

Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file ending in .conf:

kernel.randomize_va_space = 2

Run the following script to comment out entries that override the default setting of kernel.randomize_va_space:

#!/usr/bin/bash

for file in /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /run/sysctl.d/*.conf; do
   if [ -f "$file" ]; then
      grep -Esq "^\s*kernel\.randomize_va_space\s*=\s*([0-1]|[3-9]|[1-9][0-9]+)" "$file" && sed -ri 's/^\s*kernel\.randomize_va_space\s*=\s*([0-1]|[3-9]|[1-9][0-9]+)/# &/gi' "$file"
   fi
done

Run the following command to set the active kernel parameter:

sysctl -w kernel.randomize_va_space=2

Additional Information

Configuration files are read from directories in /etc/, /run/, /usr/local/lib/, and /lib/, in order of precedence. Files must have the ".conf" extension. Files in /etc/ override files with the same name in /run/, /usr/local/lib/, and /lib/. Files in /run/ override files with the same name under /usr/.

Default Value

kernel.randomize_va_space = 2

References

1. http://manpages.ubuntu.com/manpages/focal/man5/sysctl.d.5.html

CIS Controls

Assessment Status

Automated