Guide to the Secure Configuration of Red Hat Enterprise Linux 7

with profile ANSSI DAT-NT28 (minimal)
Draft profile for ANSSI compliance at the minimal level. ANSSI stands for Agence nationale de la sécurité des systèmes d'information. Based on https://www.ssi.gouv.fr/.

This guide presents a catalog of security-relevant configuration settings for Red Hat Enterprise Linux 7. It is a rendering of content structured in the eXtensible Configuration Checklist Description Format (XCCDF) in order to support security automation. The SCAP content is is available in the scap-security-guide package which is developed at https://www.open-scap.org/security-policies/scap-security-guide.

Providing system administrators with such guidance informs them how to securely configure systems under their control in a variety of network roles. Policy makers and baseline creators can use this catalog of settings, with its associated references to higher-level security control catalogs, in order to assist them in security baseline creation. This guide is a catalog, not a checklist, and satisfaction of every item is not likely to be possible or sensible in many operational scenarios. However, the XCCDF format enables granular selection and adjustment of settings, and their association with OVAL and OCIL content provides an automated checking capability. Transformations of this document, and its associated automated checking content, are capable of providing baselines that meet a diverse set of policy objectives. Some example XCCDF Profiles, which are selections of items that form checklists and can be used as baselines, are available with this guide. They can be processed, in an automated fashion, with tools that support the Security Content Automation Protocol (SCAP). The DISA STIG for Red Hat Enterprise Linux 7, which provides required settings for US Department of Defense systems, is one example of a baseline created from this guidance.

This benchmark is a direct port of a SCAP Security Guide benchmark developed for Red Hat Enterprise Linux. It has been modified through an automated process to remove specific dependencies on Red Hat Enterprise Linux and to function with CentOS. The result is a generally useful SCAP Security Guide benchmark with the following caveats:

  • CentOS is not an exact copy of Red Hat Enterprise Linux. There may be configuration differences that produce false positives and/or false negatives. If this occurs please file a bug report.
  • CentOS has its own build system, compiler options, patchsets, and is a community supported, non-commercial operating system. CentOS does not inherit certifications or evaluations from Red Hat Enterprise Linux. As such, some configuration rules (such as those requiring FIPS 140-2 encryption) will continue to fail on CentOS.

Members of the CentOS community are invited to participate in OpenSCAP and SCAP Security Guide development. Bug reports and patches can be sent to GitHub: https://github.com/OpenSCAP/scap-security-guide. The mailing list is at https://fedorahosted.org/mailman/listinfo/scap-security-guide.

Do not attempt to implement any of the settings in this guide without first testing them in a non-operational environment. The creators of this guidance assume no responsibility whatsoever for its use by other parties, and makes no guarantees, expressed or implied, about its quality, reliability, or any other characteristic.
Profile TitleANSSI DAT-NT28 (minimal)
Profile IDxccdf_org.ssgproject.content_profile_anssi_nt28_minimal

Revision History

Current version: 0.1.38

  • draft (as of 2018-03-05)

Platforms

  • cpe:/o:redhat:enterprise_linux:7
  • cpe:/o:centos:centos:7
  • cpe:/o:redhat:enterprise_linux:7::client
  • cpe:/o:redhat:enterprise_linux:7::computenode

Table of Contents

  1. System Settings
    1. Installing and Maintaining Software
    2. File Permissions and Masks
    3. Configure Syslog

Checklist

contains 8 rules

System Settings   [ref]group

Contains rules that check correct system settings.

contains 8 rules

Installing and Maintaining Software   [ref]group

The following sections contain information on security-relevant choices during the initial operating system installation process and the setup of software updates.

contains 2 rules

Sudo   [ref]group

Sudo, which stands for "su 'do'", provides the ability to delegate authority to certain users, groups of users, or system administrators. When configured for system users and/or groups, Sudo can allow a user or group to execute privileged commands that normally only root is allowed to execute.

For more information on Sudo and addition Sudo configuration options, see https://www.sudo.ws

contains 2 rules

Ensure Users Re-Authenticate for Privilege Escalation - sudo NOPASSWD   [ref]rule

The sudo NOPASSWD tag, when specified, allows a user to execute commands using sudo without having to authenticate. This should be disabled by making sure that the NOPASSWD tag does not exist in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/.

Rationale:

Without re-authentication, users may access resources or perform tasks for which they do not have authorization.

When operating systems provide the capability to escalate a functional capability, it is critical that the user re-authenticate.

Severity:  medium

References:  SV-86571r1_rule

Ensure Users Re-Authenticate for Privilege Escalation - sudo !authenticate   [ref]rule

The sudo !authenticate option, when specified, allows a user to execute commands using sudo without having to authenticate. This should be disabled by making sure that the !authenticate option does not exist in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/.

Rationale:

Without re-authentication, users may access resources or perform tasks for which they do not have authorization.

When operating systems provide the capability to escalate a functional capability, it is critical that the user re-authenticate.

Severity:  medium

References:  SV-86573r2_rule

File Permissions and Masks   [ref]group

Traditional Unix security relies heavily on file and directory permissions to prevent unauthorized users from reading or modifying files to which they should not have access.

Several of the commands in this section search filesystems for files or directories with certain characteristics, and are intended to be run on every local partition on a given system. When the variable PART appears in one of the commands below, it means that the command is intended to be run repeatedly, with the name of each local partition substituted for PART in turn.

The following command prints a list of all xfs partitions on the local system, which is the default filesystem for Red Hat Enterprise Linux 7 installations:

$ mount -t xfs | awk '{print $3}'
For any systems that use a different local filesystem type, modify this command as appropriate.

contains 4 rules

Verify Permissions on Important Files and Directories   [ref]group

Permissions for many files on a system must be set restrictively to ensure sensitive information is properly protected. This section discusses important permission restrictions which can be verified to ensure that no harmful discrepancies have arisen.

contains 4 rules
contains 4 rules

Verify Permissions on shadow File   [ref]rule

To properly set the permissions of /etc/shadow, run the command:

$ sudo chmod 0000 /etc/shadow

Rationale:

The /etc/shadow file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.

Severity:  medium

References:  AC-6, Req-8.7.c, 5.5.2.2, 6.1.3

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:configure
chmod 0000 /etc/shadow
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:configure
- name: Ensure permission 0000 on /etc/shadow
  file:
    path="{{item}}"
    mode=0000
  with_items:
    - /etc/shadow
  tags:
    - file_permissions_etc_shadow
    - medium_severity
    - configure_strategy
    - low_complexity
    - low_disruption
    - CCE-27100-7
    - NIST-800-53-AC-6
    - PCI-DSS-Req-8.7.c
    - CJIS-5.5.2.2

Verify Permissions on group File   [ref]rule

To properly set the permissions of /etc/group, run the command:

$ sudo chmod 644 /etc/group

Rationale:

The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

Severity:  medium

References:  AC-6, Req-8.7.c, 5.5.2.2, 6.1.4

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:configure

chmod 0644 /etc/group
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:configure

- name: Find /etc/group file(s)
  find:
    paths: "{{ '/etc/group' | dirname }}"
    patterns: "{{ '/etc/group' | basename }}"
  register: files_found
  tags:
    - file_permissions_etc_group
    - medium_severity
    - configure_strategy
    - low_complexity
    - low_disruption
    - CCE-26949-8
    - NIST-800-53-AC-6
    - PCI-DSS-Req-8.7.c
    - CJIS-5.5.2.2

- name: Set permissions
  file:
    path: "{{ item.path }}"
    mode: 0644
  with_items:
    - "{{ files_found.files }}"
  tags:
    - file_permissions_etc_group
    - medium_severity
    - configure_strategy
    - low_complexity
    - low_disruption
    - CCE-26949-8
    - NIST-800-53-AC-6
    - PCI-DSS-Req-8.7.c
    - CJIS-5.5.2.2

Verify Permissions on gshadow File   [ref]rule

To properly set the permissions of /etc/gshadow, run the command:

$ sudo chmod 0000 /etc/gshadow

Rationale:

The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security.

Severity:  medium

References:  AC-6, 6.1.5

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:configure

chmod 0000 /etc/gshadow
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:configure

- name: Find /etc/gshadow file(s)
  find:
    paths: "{{ '/etc/gshadow' | dirname }}"
    patterns: "{{ '/etc/gshadow' | basename }}"
  register: files_found
  tags:
    - file_permissions_etc_gshadow
    - medium_severity
    - configure_strategy
    - low_complexity
    - low_disruption
    - CCE-27162-7
    - NIST-800-53-AC-6

- name: Set permissions
  file:
    path: "{{ item.path }}"
    mode: 0000
  with_items:
    - "{{ files_found.files }}"
  tags:
    - file_permissions_etc_gshadow
    - medium_severity
    - configure_strategy
    - low_complexity
    - low_disruption
    - CCE-27162-7
    - NIST-800-53-AC-6

Verify Permissions on passwd File   [ref]rule

To properly set the permissions of /etc/passwd, run the command:

$ sudo chmod 0644 /etc/passwd

Rationale:

If the /etc/passwd file is writable by a group-owner or the world the risk of its compromise is increased. The file contains the list of accounts on the system and associated information, and protection of this file is critical for system security.

Severity:  medium

References:  AC-6, Req-8.7.c, 5.5.2.2, 6.1.2

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:configure

chmod 0644 /etc/passwd
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:configure

- name: Find /etc/passwd file(s)
  find:
    paths: "{{ '/etc/passwd' | dirname }}"
    patterns: "{{ '/etc/passwd' | basename }}"
  register: files_found
  tags:
    - file_permissions_etc_passwd
    - medium_severity
    - configure_strategy
    - low_complexity
    - low_disruption
    - CCE-26887-0
    - NIST-800-53-AC-6
    - PCI-DSS-Req-8.7.c
    - CJIS-5.5.2.2

- name: Set permissions
  file:
    path: "{{ item.path }}"
    mode: 0644
  with_items:
    - "{{ files_found.files }}"
  tags:
    - file_permissions_etc_passwd
    - medium_severity
    - configure_strategy
    - low_complexity
    - low_disruption
    - CCE-26887-0
    - NIST-800-53-AC-6
    - PCI-DSS-Req-8.7.c
    - CJIS-5.5.2.2

Configure Syslog   [ref]group

The syslog service has been the default Unix logging mechanism for many years. It has a number of downsides, including inconsistent log format, lack of authentication for received messages, and lack of authentication, encryption, or reliable transport for messages sent over a network. However, due to its long history, syslog is a de facto standard which is supported by almost all Unix applications.

In Red Hat Enterprise Linux 7, rsyslog has replaced ksyslogd as the syslog daemon of choice, and it includes some additional security features such as reliable, connection-oriented (i.e. TCP) transmission of logs, the option to log to database formats, and the encryption of log data en route to a central logging server. This section discusses how to configure rsyslog for best effect, and how to use tools provided with the system to maintain and monitor logs.

contains 2 rules

Ensure rsyslog is Installed   [ref]rule

Rsyslog is installed by default. The rsyslog package can be installed with the following command:

$ sudo yum install rsyslog

Rationale:

The rsyslog package provides the rsyslog daemon, which provides system logging services.

Severity:  medium

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:enable
# Function to install or uninstall packages on RHEL and Fedora systems.
#
# Example Call(s):
#
#     package_command install aide
#     package_command remove telnet-server
#
function package_command {

# Load function arguments into local variables
local package_operation=$1
local package=$2

# Check sanity of the input
if [ $# -ne "2" ]
then
  echo "Usage: package_command 'install/uninstall' 'rpm_package_name"
  echo "Aborting."
  exit 1
fi

# If dnf is installed, use dnf; otherwise, use yum
if [ -f "/usr/bin/dnf" ] ; then
  install_util="/usr/bin/dnf"
else
  install_util="/usr/bin/yum"
fi

if [ "$package_operation" != 'remove' ] ; then
  # If the rpm is not installed, install the rpm
  if ! /bin/rpm -q --quiet $package; then
    $install_util -y $package_operation $package
  fi
else
  # If the rpm is installed, uninstall the rpm
  if /bin/rpm -q --quiet $package; then
    $install_util -y $package_operation $package
  fi
fi

}

package_command install rsyslog
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable
- name: Ensure rsyslog is installed
  package:
    name="{{item}}"
    state=present
  with_items:
    - rsyslog
  tags:
    - package_rsyslog_installed
    - medium_severity
    - enable_strategy
    - low_complexity
    - low_disruption
    - CCE-80187-8
    - NIST-800-53-AU-9(2)

Remediation Puppet snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable
include install_rsyslog

class install_rsyslog {
  package { 'rsyslog':
    ensure => 'installed',
  }
}
Remediation Anaconda snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable

package --add=rsyslog

Enable rsyslog Service   [ref]rule

The rsyslog service provides syslog-style logging by default on Red Hat Enterprise Linux 7. The rsyslog service can be enabled with the following command:

$ sudo systemctl enable rsyslog.service

Rationale:

The rsyslog service must be running in order to provide logging services, which are essential to system administration.

Severity:  medium

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:enable
# Function to enable/disable and start/stop services on RHEL and Fedora systems.
#
# Example Call(s):
#
#     service_command enable bluetooth
#     service_command disable bluetooth.service
#
#     Using xinetd:
#     service_command disable rsh.socket xinetd=rsh
#
function service_command {

# Load function arguments into local variables
local service_state=$1
local service=$2
local xinetd=$(echo $3 | cut -d'=' -f2)

# Check sanity of the input
if [ $# -lt "2" ]
then
  echo "Usage: service_command 'enable/disable' 'service_name.service'"
  echo
  echo "To enable or disable xinetd services add \'xinetd=service_name\'"
  echo "as the last argument"  
  echo "Aborting."
  exit 1
fi

# If systemctl is installed, use systemctl command; otherwise, use the service/chkconfig commands
if [ -f "/usr/bin/systemctl" ] ; then
  service_util="/usr/bin/systemctl"
else
  service_util="/sbin/service"
  chkconfig_util="/sbin/chkconfig"
fi

# If disable is not specified in arg1, set variables to enable services.
# Otherwise, variables are to be set to disable services.
if [ "$service_state" != 'disable' ] ; then
  service_state="enable"
  service_operation="start"
  chkconfig_state="on"
else
  service_state="disable"
  service_operation="stop"
  chkconfig_state="off"
fi

# If chkconfig_util is not empty, use chkconfig/service commands.
if ! [ "x$chkconfig_util" = x ] ; then
  $service_util $service $service_operation
  $chkconfig_util --level 0123456 $service $chkconfig_state
else
  $service_util $service_operation $service
  $service_util $service_state $service
fi

# Test if local variable xinetd is empty using non-bashism.
# If empty, then xinetd is not being used.
if ! [ "x$xinetd" = x ] ; then
  grep -qi disable /etc/xinetd.d/$xinetd && \

  if ! [ "$service_operation" != 'disable' ] ; then
    sed -i "s/disable.*/disable         = no/gI" /etc/xinetd.d/$xinetd
  else
    sed -i "s/disable.*/disable         = yes/gI" /etc/xinetd.d/$xinetd
  fi
fi

}

service_command enable rsyslog
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable
- name: Enable service rsyslog
  service:
    name="{{item}}"
    enabled="yes"
    state="started"
  with_items:
    - rsyslog
  tags:
    - service_rsyslog_enabled
    - medium_severity
    - enable_strategy
    - low_complexity
    - low_disruption
    - CCE-80188-6
    - NIST-800-53-AU-4(1)
    - NIST-800-53-AU-12

Red Hat and Red Hat Enterprise Linux are either registered trademarks or trademarks of Red Hat, Inc. in the United States and other countries. All other names are registered trademarks or trademarks of their respective companies.