by Michael S. Ritzenhoff

Lynis Vorschläge unter Debian lösen

Preview-Image: Lynis Vorschläge lösen
Photo by Stephen Dawson on Unsplash

Das eigene Debian/Linux-System kontrollieren und absichern.

Lynis

Auditierung, Systemhärtung, Konformitätstests

Ein Sicherheitstool für Systeme mit Linux-, MacOS- oder Unix-basierten Betriebssystemen. Es führt einen umfangreichen Health Scan Ihrer Systeme durch, um die Systemhärtung und Compliance-Tests zu unterstützen.

//cisofy.com/lynis/

 

Installation per

apt install lynis

oder auf demmanuellen Weg:

wget -O - https://packages.cisofy.com/keys/cisofy-software-public.key | sudo apt-key add -

apt install apt-transport-https

echo "deb https://packages.cisofy.com/community/lynis/deb/ stable main" | sudo tee /etc/apt/sources.list.d/cisofy-lynis.list
deb https://packages.cisofy.com/community/lynis/deb/ stable main

apt install lynis

Das eigene System testen

lynis audit system

 

Nach Einrichtung des Desktops die erste Analyse

 

  Great, no warnings

  Suggestions (31)
  Lynis security scan details:

  Hardening index : 74 [##############      ]
  Tests performed : 238

Test mit Lynis v2.7.5, ohne Plugins ( Download )

-

GRUB password

  * Set a password on GRUB bootloader to prevent altering boot configuration (e.g. boot in single user mode without password) [BOOT-5122] 
      https://cisofy.com/lynis/controls/BOOT-5122/

[ x ] Wird ignoriert wenn nicht gewünscht wird, auf einem Laptop als Desktop, jedes mal nach einem Reboot ein Passwort einzugeben.

 

 

Nach vielen Einstellungen zusätzlich aufgetaucht...

locate

  * The database required for 'locate' could not be found. Run 'updatedb' or 'locate.updatedb' to create this file. [FILE-6410] 
      https://cisofy.com/lynis/controls/FILE-6410/

Ausführen von:

updatedb

 

password strengh

  * Install a PAM module for password strength testing like pam_cracklib or pam_passwdqc [AUTH-9262] 
      https://cisofy.com/lynis/controls/AUTH-9262/

Nachinstallation:

apt install libpam-cracklib

 

password age

  * Configure minimum password age in /etc/login.defs [AUTH-9286] 
      https://cisofy.com/lynis/controls/AUTH-9286/
  * Configure maximum password age in /etc/login.defs [AUTH-9286] 
      https://cisofy.com/lynis/controls/AUTH-9286/

Editiere:

nano /etc/login.defs
#PASS_MAX_DAYS 99999
PASS_MAX_DAYS 365
#PASS_MIN_DAYS 0
PASS_MIN_DAYS 365
PASS_WARN_AGE 14

Überprüfe den eigenen Account mit:

chage -l <USERNAME>

Setze Maximale Anzahl der Tage zwischen Passwortänderungen

chage -M 365 <USERNAME>

Setze Anzahl der Tage, an denen vor Passwortablauf gewarnt wird

chage -W 14 <USERNAME>

 

unmask

  * Default umask in /etc/login.defs could be more strict like 027 [AUTH-9328] 
      https://cisofy.com/lynis/controls/AUTH-9328/

Editiere:

nano /etc/login.defs

... runter scrollen bis zu:

#
# Login configuration initializations:
#
...
...
...
#
ERASECHAR       0177
KILLCHAR        025
#UMASK          022
UMASK           027

 

firewire

  * Disable drivers like firewire storage when not used, to prevent unauthorized storage or data theft [STRG-1846] 
      https://cisofy.com/lynis/controls/STRG-1846/

Blacklist FireWire

echo "blacklist firewire-core" >> /etc/modprobe.d/firewire.conf

 

debsums

  * Install debsums utility for the verification of packages with known good database. [PKGS-7370]
      https://cisofy.com/lynis/controls/PKGS-7370/

Nachinstallation:

apt install debsums

 

unattended-upgrade

  * Consider using a tool to automatically apply upgrades [PKGS-7420]
      https://cisofy.com/lynis/controls/PKGS-7420/

Nachinstallation:

apt install unattended-upgrade

 

ARP

  * Consider running ARP monitoring software (arpwatch,arpon) [NETW-3032]
      https://cisofy.com/lynis/controls/NETW-3032/

Nachinstallation:

apt install arpwatch

[ x ] noch offen

iptables

  * Check iptables rules to see which rules are currently not used [FIRE-4513] 
      https://cisofy.com/lynis/controls/FIRE-4513/

[ x ] noch offen

SSH

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : AllowTcpForwarding (YES --> NO)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : ClientAliveCountMax (3 --> 2)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : Compression (YES --> NO)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : LogLevel (INFO --> VERBOSE)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : MaxAuthTries (6 --> 3)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : MaxSessions (10 --> 2)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : Port (22 --> )
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : TCPKeepAlive (YES --> NO)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : X11Forwarding (YES --> NO)
      https://cisofy.com/lynis/controls/SSH-7408/

  * Consider hardening SSH configuration [SSH-7408] 
    - Details  : AllowAgentForwarding (YES --> NO)
      https://cisofy.com/lynis/controls/SSH-7408/

Separater Post für: SSH Konfiguration

 

 

  * Check what deleted files are still in use and why. [LOGG-2190] 
      https://cisofy.com/lynis/controls/LOGG-2190/

[ x ] noch offen

Banner

  * Add a legal banner to /etc/issue, to warn unauthorized users [BANN-7126] 
      https://cisofy.com/lynis/controls/BANN-7126/
  * Add legal banner to /etc/issue.net, to warn unauthorized users [BANN-7130] https://cisofy.com/lynis/controls/BANN-7130/

editiere ...

nano /etc/ssh/sshd_config

Banner aktivieren/freigeben

# no default banner path
#Banner none
Banner /etc/issue

editiere:

nano /etc/issue

Inhalt per Default:

Debian GNU/Linux 10 \n \l

... einfach beigrfügt:

********************************************************************
*                                                                  *
* This system is for the use of authorized users only.  Usage of   *
* this system may be monitored and recorded by system personnel.   *
*                                                                  *
* Anyone using this system expressly consents to such monitoring   *
* and is advised that if such monitoring reveals possible          *
* evidence of criminal activity, system personnel may provide the  *
* evidence from such monitoring to law enforcement officials.      *
*                                                                  *
********************************************************************

editiere:

nano /etc/issue.net

Inhalt per Default:

Debian GNU/Linux 10

... einfach beigrfügt:

********************************************************************
*                                                                  *
* This system is for the use of authorized users only.  Usage of   *
* this system may be monitored and recorded by system personnel.   *
*                                                                  *
* Anyone using this system expressly consents to such monitoring   *
* and is advised that if such monitoring reveals possible          *
* evidence of criminal activity, system personnel may provide the  *
* evidence from such monitoring to law enforcement officials.      *
*                                                                  *
********************************************************************

//wiki.centos.org/TipsAndTricks/BannerFiles

 

ACC

  * Enable process accounting [ACCT-9622] 
      https://cisofy.com/lynis/controls/ACCT-9622/

Nachinstallation:

apt install acc

 

sysstat

  * Enable sysstat to collect accounting (disabled) [ACCT-9626] 
      https://cisofy.com/lynis/controls/ACCT-9626/

editiere:

nano /etc/default/sysstat
#ENABLED="false"
ENABLED="true"

Optional:

nano /etc/cron.d/sysstat

Change the collection interval from every 10 minutes.

5-55/10 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1

e.g. to every 2 minutes if needed

*/2 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1

sysstat starten

systemctl enable sysstat

sysstat neustarten

service sysstat restart

oder

/etc/init.d/sysstat restart

 

auditd

  * Enable auditd to collect audit information [ACCT-9628] 
      https://cisofy.com/lynis/controls/ACCT-9628/

Separater Post für: Installation des Audit daemon

 

ntpq

  * Check ntpq peers output for unreliable ntp peers and correct/replace them [TIME-3120] 
      https://cisofy.com/lynis/controls/TIME-3120/

[ x ] noch offen

 

certificates

  * Check available certificates for expiration [CRYP-7902] 
      https://cisofy.com/lynis/controls/CRYP-7902/

[ x ] noch offen

 

ansible

  * Determine if automation tools are present for system management [TOOL-5002] 
      https://cisofy.com/lynis/controls/TOOL-5002/

Nachinstallation:

apt install ansible

 

sysctl

  * One or more sysctl values differ from the scan profile and could be tweaked [KRNL-6000] 
    - Solution : Change sysctl value or disable test (skip-test=KRNL-6000:<sysctl-key>)
      https://cisofy.com/lynis/controls/KRNL-6000/

editiere:

nano /etc/sysctl.conf
# Uncomment the next line to enable TCP/IP SYN cookies
# See http://lwn.net/Articles/277146/
# Note: This may impact IPv6 TCP sessions too
#net.ipv4.tcp_syncookies=1
net.ipv4.tcp_syncookies=1

# Uncomment the next line to enable packet forwarding for IPv4
#net.ipv4.ip_forward=1
net.ipv4.ip_forward=1

# Uncomment the next line to enable packet forwarding for IPv6
# Enabling this option disables Stateless Address Autoconfiguration
# based on Router Advertisements for this host
#net.ipv6.conf.all.forwarding=1
net.ipv6.conf.all.forwarding=1

neu laden per

sysctl -p

[ x ] noch offen

 

compilers

  * Harden compilers like restricting access to root user only [HRDN-7222]
      https://cisofy.com/lynis/controls/HRDN-7222/

[ x ] noch offen

 

Apache

  * Install Apache mod_evasive to guard webserver against DoS/brute force attempts [HTTP-6640]
      //cisofy.com/lynis/controls/HTTP-6640/
  • apt install libapache2-mod-evasive
  • a2enmod mod-evasive
  • apachectl -M | grep evasive

 

  * Install Apache modsecurity to guard webserver against web application attacks [HTTP-6643]
      //cisofy.com/lynis/controls/HTTP-6643/
  • apt install libapache2-mod-security2
  • /etc/init.d/apache2 restart
  • apt-cache show libapache2-mod-security2

Configure ModSecurity

cp /etc/modsecurity/modsecurity.conf-recommended /etc/modsecurity/modsecurity.conf

 

# Start

  Lynis security scan details:
  Hardening index : 74 [##############      ]
  Tests performed : 238

 

  • Nach der Installation von:
    • libpam-cracklib
    • debsums
    • unattended-upgrade
    • arpwatch ( noch nicht abschließend gelöst )
    • ansible
    • auditd
    • acc
  • und der Ausführung/Einstellungen für:
    • SSH
    • UNMASK
    • Banner
    • sysstat ( noch nicht abschließend gelöst )
    • sysctl
    • firewire
    • updatedb
  Suggestions (8):
  Hardening index : 88 [#################   ]
  Tests performed : 245

Um sich den Report als Datei ausgeben zu lassen:

lynis audit system >> /home/<USERNAE>/<FOLDER>/lynis-results.txt

 

 

THX to some of many readed sources:

Details
Kategorie: Debian
Zugriffe: 87
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