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diff --git a/linux/hardening.html b/linux/hardening.html new file mode 100644 index 0000000..0fd13e3 --- /dev/null +++ b/linux/hardening.html @@ -0,0 +1,188 @@ +<!DOCTYPE html> +<html dir="ltr" lang="en"> + <head> + <meta charset='utf-8'> + <title>2.6. Hardening</title> + </head> + <body> + + <a href="index.html">GNU/Linux Index</a> + + <h1>2.6. Hardening</h1> + + <h2>2.6.0.2 System security</h2> + + <dl> + <dt>File systems</dt> + <dd>Check <a href="install.html#fstab">fstab</a> and current mount options. Mount filesystems in read only, only strict necessary in rw.</dd> + <dt>Sys</dt> + <dd>Check kernel settings with <a href="sysctl.html">sysctl</a>.</dd> + <dd>kernel.yama.ptrace_scope breaks gdb, strace, perf trace and reptyr.</dd> + <dt>Iptables</dt> + <dd>Check if <a href="network.html#iptables">iptables</a> rules are loaded and are correctly logging.(firewald works as API to iptables).</dd> + <dt>Apparmor</dt> + <dd>Check if <a href="apparmor.html">apparmor</a> is active and enforcing policies.</dd> + <dt>Samhain</dt> + <dd>Check if <a href="samhain.html">samhain</a> is running.</dd> + <dt>Toolchain</dt> + <dd>Build ports using hardened <a href="toolchain.html">toolchain</a> settings.</dd> + </dl> + + + <pre> + $ sudo prt-get depinst checksec + </pre> + + <h2>2.6.0.1 System configuration</h2> + + <h3>1.1 - Users groups, passwords and sudo.</h3> + + <p>Check "normal" users groups, make sure they are not admin or wheel group; ps -U root -u root u, ps axl | awk '$7 != 0 && $10 !~ "Z"', process permission; ps -o gid,rdig,supgid -p "$pid"</p> + + <p>Maintain, secure with hash, and enforce secure passwords with pam-cracklib.</p> + + + <h3>1.2 - Linux PAM</h3> + + <p>Cat /etc/pam.d/system-auth. Check pam modules, test on virtual machine, user can lockout during tests. Check files (processes); getfacl filename.</p> + + <p>Check files (processes) set uid and set gid;</p> + + <pre> + # find / -perm 4000 >> /root/setuid_files + # find / -perm 2000 >> /root/setguid_files + </pre> + + <p>To setuid (4744);</p> + + <pre> + # chmod u+s filename + </pre> + + <p>To remove (0664) from su and Xorg (user must be part of input and video for xorg to run);</p> + + <pre> + # chmod u-s /usr/bin/su + # chmod u-s /usr/bin/X + </pre> + + <p>To set gid (2744)</p> + <pre> + # chmod g+s filename + </pre> + <p>To remove (0774);</p> + <pre> + # chmod g-s filename + </pre> + + <p>Find world writable files;</p> + + <pre> + # find /dir -xdev -type d \( -perm -0002 -a ! -perm -1000 \) -print + </pre> + + <p>No owner files;</p> + + <pre> + # find /dir -xdev \( -nouser -o -nogroup \) -print + </pre> + + <h3>1.3. Capabilities</h3> + + <p>Check capabilities;</p> + <pre> + # getcap filename + </pre> + + <dd>1.9 - Limit number of processes.</dd> + <dd>1.10 - Lock user after 3 failed loggins.</dd> + <dd>1.8 - Block host ip based on iptable and services + abuse.</dd> + </dl> + + <h3>1.4 Sudo</h3> + + <p>Check sudo, sudoers and sudo replay.</p> + + <p>Don't run editor as root, instead run sudoedit filename or sudo --edit filename. Editor can be set as a environment variable;</p> + + <pre> + $ export SUDO_EDITOR=vim + </pre> + + <p>Set rvim as default on sudo config;</p> + + <pre> + # visudo + + Defaults editor=/usr/bin/rvim + </pre> + + <p>Once sudo is correctly configured, disable root login;</p> + + <pre> + # passwd --lock root + </pre> + + <h3>1.5 Auditd</h3> + + <pre> + $ prt-get depinst audit + </pre> + + <p>Example audit when file /etc/passwd get modified;</p> + + <pre> + $ auditctl -w /etc/passwd -p wa -k passwd_changes + </pre> + + <p>Audit when a module get's loaded;</p> + + <pre> + # auditctl -w /sbin/insmod -p x -k module_insertion + </pre> + + <h3>1.6 Network</h3> + + <p>Find listening services with command;</p> + + <pre> + # ss -tulpn + # nmap -sT -O localhost + # nmap -sT -O machine.example.org + </pre> + + <h2>2.6.0.2 Lynis</h2> + + <pre> + $ sudo prt-get depinst lynis + </pre> + + <p>Lynis gives a view of system overall configuration, + without changing default profile it runs irrelevant tests. + Create a lynis profile by coping default one and run lynis;</p> + + <pre> + $ sudo cp /etc/lynis/default.prf /etc/lynis/custom.prf + $ sudo lynis configure settings color=yes + $ sudo lynis show settings + $ sudo lynis show profile + </pre> + + <pre> + $ lynis audit system > lynis_report + $ mv /tmp/lynis.log . + $ mv /tmp/lynis-report.dat . + </pre> + + <p>Add unnecessary tests to profile to have less noise.</p> + + <a href="index.html">GNU/Linux Index</a> + <p>This is part of the LeetIO System Documentation. + Copyright (C) 2021 + LeetIO Team. + See the file <a href="../fdl-1.3-standalone.html">Gnu Free Documentation License</a> + for copying conditions.</p> + + </body> +</html> |