Disable Postfix Network Listening

An XCCDF Rule

Description

Edit the file /etc/postfix/main.cf to ensure that only the following inet_interfaces line appears:

inet_interfaces =

Rationale

This ensures postfix accepts mail messages (such as cron job reports) from the local system only, and not from the network, which protects it from network attack.

ID: xccdf_org.ssgproject.content_rule_postfix_network_listening_disabled
Severity: Medium
References: BP28(R48)

11 14 3 9

BAI10.01 BAI10.02 BAI10.03 BAI10.05 DSS05.02 DSS05.05 DSS06.06

CCI-000382

4.3.3.5.1 4.3.3.5.2 4.3.3.5.3 4.3.3.5.4 4.3.3.5.5 4.3.3.5.6 4.3.3.5.7 4.3.3.5.8 4.3.3.6.1 4.3.3.6.2 4.3.3.6.3 4.3.3.6.4 4.3.3.6.5 4.3.3.6.6 4.3.3.6.7 4.3.3.6.8 4.3.3.6.9 4.3.3.7.1 4.3.3.7.2 4.3.3.7.3 4.3.3.7.4 4.3.4.3.2 4.3.4.3.3

SR 1.1 SR 1.10 SR 1.11 SR 1.12 SR 1.13 SR 1.2 SR 1.3 SR 1.4 SR 1.5 SR 1.6 SR 1.7 SR 1.8 SR 1.9 SR 2.1 SR 2.2 SR 2.3 SR 2.4 SR 2.5 SR 2.6 SR 2.7 SR 7.6

A.12.1.2 A.12.5.1 A.12.6.2 A.14.2.2 A.14.2.3 A.14.2.4 A.9.1.2

CM-6(a) CM-7(a) CM-7(b)

PR.IP-1 PR.PT-3

2.2.15

1.4.2
Updated: about 1 year ago

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ] && { dpkg-query --show --showformat='${db:Status-Status}\n' 'postfix' 2>/dev/null | grep -q installed; }; then

var_postfix_inet_interfaces='<xccdf-1.2:sub xmlns:xccdf-1.2="http://checklists.nist.gov/xccdf/1.2" idref="xccdf_org.ssgproject.content_value_var_postfix_inet_interfaces" use="legacy"/>'

if [ -e "/etc/postfix/main.cf" ] ; then
    
    LC_ALL=C sed -i "/^\s*inet_interfaces\s\+=\s\+/Id" "/etc/postfix/main.cf"
else
    touch "/etc/postfix/main.cf"
fi
# make sure file has newline at the end
sed -i -e '$a\' "/etc/postfix/main.cf"

cp "/etc/postfix/main.cf" "/etc/postfix/main.cf.bak"
# Insert at the end of the file
printf '%s\n' "inet_interfaces=$var_postfix_inet_interfaces" >> "/etc/postfix/main.cf"
# Clean up after ourselves.
rm "/etc/postfix/main.cf.bak"

systemctl restart postfix

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Disable Postfix Network Listening

Description

Rationale

Remediation - Shell Script