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<title>2.6. Hardening</title>
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<a href="index.html">Core OS 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">Core OS Index</a>
<p>This is part of the Tribu System Documentation.
Copyright (C) 2020
Tribu Team.
See the file <a href="../fdl-1.3-standalone.html">Gnu Free Documentation License</a>
for copying conditions.</p>
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