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Description
To specify password maximum age for new accounts,
edit the file /etc/login.defs
and add or correct the following line:
A value of 180 days is sufficient for many environments.
The DoD requirement is 60.
The profile requirement is 365.
Rationale
Any password, no matter how complex, can eventually be cracked. Therefore, passwords
need to be changed periodically. If the operating system does not limit the lifetime
of passwords and force users to change their passwords, there is the risk that the
operating system passwords could be compromised.
Setting the password maximum age ensures users are required to
periodically change their passwords. Requiring shorter password lifetimes
increases the risk of users writing down the password in a convenient
location subject to physical compromise.
Shell script
The following script can be run on the host to remediate the issue.
#!/bin/bash
# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'login' 2>/dev/null | grep -q installed; then
var_accounts_maximum_age_login_defs='365'
# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^PASS_MAX_DAYS")
# shellcheck disable=SC2059
printf -v formatted_output "%s %s" "$stripped_key" "$var_accounts_maximum_age_login_defs"
# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^PASS_MAX_DAYS\\>" "/etc/login.defs"; then
escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
LC_ALL=C sed -i --follow-symlinks "s/^PASS_MAX_DAYS\\>.*/$escaped_formatted_output/gi" "/etc/login.defs"
else
if [[ -s "/etc/login.defs" ]] && [[ -n "$(tail -c 1 -- "/etc/login.defs" || true)" ]]; then
LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/login.defs"
fi
printf '%s\n' "$formatted_output" >> "/etc/login.defs"
fi
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
