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--- tech:notes_securite_os_gnu_linux_hardening [2025/03/24 15:06] – créée - modification externe 127.0.0.1
+++ tech:notes_securite_os_gnu_linux_hardening [2026/06/29 14:23] (Version actuelle) – Jean-Baptiste
@@ Ligne 1: / Ligne 1: @@
+<!DOCTYPE markdown>
+{{tag>Brouillon Sécurité Debian}}
+# Notes sécurité OS GNU/Linux hardening
+Voir :
+* [[Notes sécurité OS GNU_Linux hardening - partitions - noexec]]
+* https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
+* https://www.ssi.gouv.fr/uploads/2016/01/linux_configuration-fr-v1.2.pdf
+* https://static.open-scap.org/ssg-guides/ssg-rhel8-guide-cis.html
+* https://forum.tufin.com/support/kc/latest/Content/Suite/TufinOS_BenchmarkCIS.htm
+* https://www.server-world.info/en/note?os=Debian_7.0&p=password
+* https://github.com/openstack/ansible-hardening
+* https://www.security-session.cz/2012/Martin_Cmelik-Hardening_Linux_Securix.pdf
+* https://medium.com/thedevopsguy/wanna-harden-your-ubuntu-image-c9511f41a863
+* https://github.com/florianutz/Debian9-CIS
+* [Guide to the Secure Configuration of Red Hat Enterprise Linux 8 - ANSSI-BP-028](https://static.open-scap.org/ssg-guides/ssg-rhel8-guide-anssi_bp28_minimal.html)
+Voir aussi :
+* CIS (Center for Internet Security)
+* https://www.cisa.gov/
+* https://www.cert.ssi.gouv.fr
+## Vulnérabilités connues
+~~~bash
+apt-get install debsecan
+debsecan
+~~~
+## Mise à jour automatique
+~~~bash
+apt-get install unattended-upgrades
+~~~
+## Scan intégrité fichiers
+### Find
+Recherche de fichier SUID (4000) et SGID (2000)
+~~~bash
+find / -type f \( -perm -4000 -o -perm -2000 \)         \
+        -not \(                                         \
+        -wholename "/proc/*"                            \
+        -o -wholename "/var/lib/docker/aufs/*"          \
+        -o -wholename /usr/bin/chage                    \
+        -o -wholename /usr/bin/newgrp                   \
+        -o -wholename /usr/bin/passwd                   \
+        -o -wholename /usr/bin/gpasswd                  \
+        -o -wholename /usr/bin/expiry                   \
+        -o -wholename /bin/su                           \
+        -o -wholename /bin/mount                        \
+        -o -wholename /bin/ping6                        \
+        -o -wholename /bin/ping                         \
+        -o -wholename /bin/umount                       \
+        -o -wholename /sbin/unix_chkpwd                 \
+        -o -wholename /usr/bin/pumount                  \
+        -o -wholename /usr/bin/pmount                   \
+        -o -wholename /usr/bin/sudo                     \
+        -o -wholename /usr/bin/crontab                  \
+        -o -wholename /usr/bin/mlocate                  \
+        -o -wholename /sbin/mount.cifs                  \
+        -o -wholename /bin/fusermount                   \
+        -o -wholename /bin/ntfs-3g                      \
+        -o -wholename /usr/lib/dbus-1.0/dbus-daemon-launch-helper \
+        -o -wholename /usr/bin/at                       \
+        -o -wholename /usr/lib/eject/dmcrypt-get-device \
+        -o -wholename /usr/lib/utempter/utempter        \
+        \)
+        #-o -wholename /usr/bin/wall                    \
+        #-o -wholename /usr/bin/chsh                    \
+        #-o -wholename /usr/bin/ssh-agent               \
+        #-o -wholename /usr/lib/openssh/ssh-keysign     \
+        #-o -wholename /usr/bin/bsd-write               \
+        #-o -wholename /usr/bin/udevil                  \
+        #-o -wholename /usr/bin/chfn                    \
+        #-o -wholename /usr/bin/dotlockfile             \
+        #-o -wholename /usr/sbin/exim4                  \
+        #-o -wholename /usr/bin/beep                    \
+~~~
+Supression du bit SUID
+~~~bash
+chmod u-s /usr/bin/chsh
+chmod u-s /usr/bin/chfn
+chmod u-s /usr/lib/openssh/ssh-keysign
+chmod u-s /usr/sbin/exim4
+~~~
+Supression du bit SGID
+~~~bash
+chmod g-s /usr/bin/dotlockfile
+chmod g-s /usr/bin/ssh-agent
+chmod g-s /usr/bin/wall
+~~~
+Worldreadable
+~~~bash
+find / \( -type d -o -type f \)  -not \( -wholename "/proc/*" -o -wholename "/dev/*" -o -wholename "/var/lib/docker/aufs/*" \) -perm /o=w -not -perm /o=t -ls
+~~~
+## Comptes
+~~~bash
+perl -a -F':' -ne '$HOMEUSER=$F[5] ; $CHAINE="$HOMEUSER/.ssh/authorized_keys\n" ; $CHAINE=~s|//|/| ; print $CHAINE unless /false$/ or /nologin$/' /etc/passwd
+~~~
+## sysctl
+Voir https://www.it-connect.fr/details-durcissement-sysctl-systeme-linux/
+Interdire strace
+~~~bash
+echo 3 > /proc/sys/kernel/yama/ptrace_scope
+~~~
+## Mot de passe
+Lenteur à la connexion
+man 3 crypt
+`/etc/shadow`
+~~~
+plop1:$6$rounds=656000$P7gp1PPaN9bdjMt/$M2xJFWCpmlTS8CkYCHOnjI1TqfhIabgkJhp4HNvHHsI3NkXYJ2vZ.OVSNpOtee3sXJQcCdcZhezlQfrHZm3fE1:18369:0:99999:7:::
+plop1:$6$LCJMGXiumcpyY7nP$8t/u6oewRH.GHk94QKmN/1pZyMFCIwG4Y/JzUF/qKSVU9/U.BhG1Vm6fpYIuUaZuIJq5b6omuGJVpD9XxFisM.:18369:0:99999:7:::
+~~~
+https://askubuntu.com/questions/894404/how-to-increase-the-number-of-hashing-rounds-for-etc-shadow
+`/etc/pam.d/common-password`
+~~~
+#password       [success=1 default=ignore]      pam_unix.so obscure sha512
+password        [success=1 default=ignore]      pam_unix.so obscure sha512 rounds=656000
+~~~
+Voir `SHA_CRYPT_MIN_ROUNDS`
+~~~bash
+man pam_unix
+sudo chpasswd -s 10000 000 -c SHA512 <<< username:password; history -c
+~~~
+`/etc/pam.d/common-password`
+~~~
+password        [success=1 default=ignore]      pam_unix.so obscure sha512 rounds=656000
+~~~
+~~~
+auth required pam_tally2.so onerr=fail deny=3 unlock_time=900 root_unlock_time=900 file=/var/log/tallylog
+pam_tally2 --file /var/log/tallylog --reset --user root
+pam_faildelay.so
+faillock --user aaronkilik --reset
+faillock --user aaronkilik
+fail --reset	#clears all authentication failure records
+~~~
+~~~bash
+chown root:root /boot/grub2/grub.cfg
+chmod og-rwx /boot/grub2/grub.cfg
+~~~
+Set the following restrict parameters in /etc/ntp.conf ** or use /etc/systemd/timesyncd.conf (for Debian) **
+`/etc/ntp.conf`
+~~~
+restrict default kod nomodify notrap nopeer noquery
+restrict -6 default kod nomodify notrap nopeer noquery
+~~~
+Set the following restrict parameters in /etc/ntp.conf
+`/etc/ntp.conf`
+~~~
+restrict default kod nomodify notrap nopeer noquery
+restrict -6 default kod nomodify notrap nopeer noquery
+~~~
+`/etc/ntp.conf`
+~~~
+Also, make sure /etc/ntp.conf has an NTP server specified
+server <ntp-server>
+~~~
+Set the `net.ipv4.ip_forward` parameter to 0 in /etc/sysctl.conf
+Modify active kernel parameters to match:
+~~~bash
+/sbin/sysctl -w net.ipv4.ip_forward=0
+/sbin/sysctl -w net.ipv4.route.flush=1
+~~~
+~~~bash
+chown root:root /etc/cron.d
+chmod og-rwx /etc/cron.d
+~~~
+~~~bash
+rm /etc/at.deny
+touch /etc/at.allow
+chown root:root /etc/at.allow
+chmod og-rwx /etc/at.allow
+~~~
+Edit the /etc/bashrc and /etc/profile.d/cis.sh files (and the appropriate files for any other shell supported on your system) and add the ** or use PAM **
+following the UMASK parameter as shown
+~~~
+umask 027
+~~~
+Pas de version dans les fichiers suivants
+* /etc/motd
+* /etc/issue
+* /etc/issue.net
+## Service SystemD
+`/lib/systemd/system/wsl-pro.service`
+~~~ini
+[Unit]
+Description=Bridge to Ubuntu Pro agent on Windows
+ConditionVirtualization=wsl
+[Service]
+Type=notify
+ExecStart=/usr/libexec/wsl-pro-service -vv
+Restart=always
+RestartSec=2s
+# Some daemon restrictions
+LockPersonality=yes
+MemoryDenyWriteExecute=yes
+NoNewPrivileges=true
+PrivateDevices=yes
+PrivateMounts=yes
+PrivateTmp=yes
+ProtectClock=yes
+ProtectControlGroups=yes
+ProtectHostname=yes
+ProtectKernelLogs=yes
+ProtectKernelModules=yes
+ProtectKernelTunables=yes
+RestrictNamespaces=yes
+RestrictRealtime=yes
+RestrictSUIDSGID=yes
+SystemCallArchitectures=native
+# Only permit system calls used by common system services, excluding any special purpose calls
+SystemCallFilter=@system-service
+[Install]
+WantedBy=multi-user.target
+~~~
+## Autre
+~~~bash
+apt-get install auditd
+~~~
+Partition dédiée pour
+* /var/log
+* /var/log/audit/