SV-219166r958388: The Ubuntu operating system must be configured so that three consecutive invalid logon attempts by a user automatically locks the account until released by an administrator. | Canonical Ubuntu 18.04 LTS STIG SCAP Benchmark

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Assessment Title

Rule Text

The Ubuntu operating system must be configured so that three consecutive invalid logon attempts by a user automatically locks the account until released by an administrator.

Description

Discussion Text

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-force attacks, is reduced. Limits are imposed by locking the account. Satisfies: SRG-OS-000329-GPOS-00128

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-000044Not mappedCCI-002238SV-109663V-100559

References

DPMS Target Canonical Ubuntu 18.04 LTS DISA DPMS Target Canonical Ubuntu 18.04 LTS 4055

Checks

DISA STIG (Manual Reference)

Verify that the Ubuntu operating system utilizes the "pam_faillock" module with the following command:
$ grep faillock /etc/pam.d/common-auth 

auth     [default=die]  pam_faillock.so authfail
auth     sufficient     pam_faillock.so authsucc

If the pam_faillock.so module is not present in the "/etc/pam.d/common-auth" file, this is a finding.

Verify the pam_faillock module is configured to use the following options:
$ sudo egrep 'silent|audit|deny|fail_interval| unlock_time' /etc/security/faillock.conf

audit
silent
deny = 3
fail_interval = 900
unlock_time = 0

If the "silent" keyword is missing or commented out, this is a finding.
If the "audit" keyword is missing or commented out, this is a finding.
If the "deny" keyword is missing, commented out, or set to a value greater than 3, this is a finding.
If the "fail_interval" keyword is missing, commented out, or set to a value greater than 900, this is a finding.
If the "unlock_time" keyword is missing, commented out, or is not set to 0, this is a finding.

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

#!/bin/bash
# Reconstructed from oval:mil.disa.stig.ubuntu1804:def:116
# The Ubuntu operating system must be configured so that three consecutive invalid logon attempts by a user automatically locks the account until released by an administrator.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# pam_faillock.so module authfail is present in /etc/pam.d/common-auth file
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  grep -Pq '^\s*auth\s+\[default=die\]\s+pam_faillock\.so\s+authfail\s*$' '/etc/pam.d/common-auth' &>/dev/null
}
# pam_faillock.so module authsucc is present in /etc/pam.d/common-auth file
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  grep -Pq '^\s*auth\s+sufficient\s+pam_faillock\.so\s+authsucc\s*$' '/etc/pam.d/common-auth' &>/dev/null
}
# pam_faillock.so is used with audit
# textfilecontent54_object (textfilecontent54_test)
test_3() {
  grep -Pq '^\s*audit\s*$' '/etc/security/faillock.conf' &>/dev/null
}
# pam_faillock.so is used with silent
# textfilecontent54_object (textfilecontent54_test)
test_4() {
  grep -Pq '^\s*silent\s*$' '/etc/security/faillock.conf' &>/dev/null
}
# pam_faillock.so is used with deny set to 3 or less
# textfilecontent54_object (textfilecontent54_test)
test_5() {
  [ "$(sed -En 's/^\s*deny\s*=\s*([0-9])+\s*$/\1/p' '/etc/security/faillock.conf')" -le 3 ]
}
# pam_faillock.so is used with fail_interval set to 900 or less
# textfilecontent54_object (textfilecontent54_test)
test_6() {
  [ "$(sed -En 's/^\s*fail_interval\s*=\s*([0-9]+)+\s*$/\1/p' '/etc/security/faillock.conf')" -le 900 ]
}
# pam_faillock.so is used with unlock_time set to 0
# textfilecontent54_object (textfilecontent54_test)
test_7() {
  [ "$(sed -En 's/^\s*unlock_time\s*=\s*([0-9])+\s*$/\1/p' '/etc/security/faillock.conf')" -eq 0 ]
}

if ( test_1 && test_2 && test_3 && test_4 && test_5 && test_6 && test_7 ); then
  echo "PASS"
else
  echo "FAIL"
fi

Assessment Script Powered by AISandbox-executed

A standalone Shell script to assess this control automatically. Review before running it in your environment.

Syntax-checked and actually executed in an isolated sandbox (not the real system this checks) — confirmed to run without errors.

#!/bin/sh
# oval:mil.disa.stig.ubuntu1804:def:116

if grep -q '^\\s*auth\\s+\\[default=die\\]\\s+pam_faillock\\.so\\s+authfail\\s*$' /etc/pam.d/common-auth && \
   grep -q '^\\s*auth\\s+sufficient\\s+pam_faillock\\.so\\s+authsucc\\s*$' /etc/pam.d/common-auth && \
   grep -q '^\\s*audit\\s*$' /etc/security/faillock.conf && \
   grep -q '^\\s*silent\\s*$' /etc/security/faillock.conf && \
   grep -q '^\\s*deny\\s*=\\s*[0-9]+\\s*$' /etc/security/faillock.conf | awk -F'=' '{print $2}' | grep -q '^[0-3]$' && \
   grep -q '^\\s*fail_interval\\s*=\\s*[0-9]+\\s*$' /etc/security/faillock.conf | awk -F'=' '{print $2}' | grep -q '^[0-9]\{1,3\}$' | grep -q '^[0-8][0-9][0-9]$' ; then
   echo "PASS"
   exit 0
else
   echo "FAIL"
   exit 1
fi

Remediation

Configure the Ubuntu operating system to utilize the "pam_faillock" module. 

Edit the /etc/pam.d/common-auth file. 

Add the following lines below the "auth" definition for pam_unix.so:
auth     [default=die]  pam_faillock.so authfail
auth     sufficient     pam_faillock.so authsucc

Configure the "pam_faillock" module to use the following options:

Edit the /etc/security/faillock.conf file and add/update the following keywords and values:
audit
silent
deny = 3
fail_interval = 900
unlock_time = 0