View source for FreeBSD:Hardening

{{DISPLAYTITLE:FreeBSD Post-Install Hardening}}
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Now that you have a solid baseline FreeBSD installation lets move on to configuring and hardening your system. In this article I will be covering setting up ports, installing some base software, setting up a user environment, and fixing some basic security concerns. The test system I will be using for this and all articles following this is from the [[FreeBSD:Install|FreeBSD Installation]] article. I personally will not be using a ZFS-based test system merely because using ZFS inside of VirtualBox is a bit redundant.

Again for this and all my other articles I am assuming you have a basic understanding of the shell and the computer in general (See Also: [[:Category:FreeBSD]]). Assuming you have the FreeBSD machine installed, booted up and logged in as root, let us begin.

==Compiler Settings==
Both located in {{Mono|/etc/}} the primary purpose of {{Mono|make.conf}} is to control the compilation of the FreeBSD sources, documentation, and ported applications; where as the only purpose of {{Mono|src.conf}} is to control the compilation of the FreeBSD source code.<ref>{{Cite web||url=http://forums.freebsd.org/showthread.php?t=3416#4|title=FreeBSD Forums|publisher=Anyone use /etc/make.conf ?}}</ref> Note that changing these documents is completely optional and is not required. However after years of using FreeBSD myself I have found that these few settings will simplify and quicken a lot of things on the system, mainly if you are someone who compiles everything from source. If you are not this type of person maybe you can skip this section, I would still recommend looking it over at the very least. Some things will still be applicable, jails for example need special attention toward to {{Mono|src.conf}}.

===make.conf===
I will be going at this file piece by piece as it is a fairly large file and to paste it all at once I feel would be a bit daunting. I will be explaining each section in sufficient detail as I go along. Please note that I am obviously assuming you have at least a basic knowledge of editing files in {{ManPage|man=vi|section=1}} as this is the default editor on FreeBSD. If you do not feel comfortable using {{ManPage|man=vi|section=1}}, you can always use the {{ManPage|man=cat|section=1}} method of creating files which was used in the installation articles (example shown below).

{{Code|<nowiki>cat >> /etc/make.conf << _EOF_</nowiki>}}
{{Output|<nowiki><i>&lt;file contents&gt;</i>
_EOF_</nowiki>}}

Lets begin with CVSup and SVN configuration.

{{Note|PORTSSUPFILE{{=}}           /root/ports-supfile<br />SUP{{=}}                    /usr/bin/csup<br />SUP_UPDATE{{=}}             YES<br />SUPFLAGS{{=}}               -L 2<br />SVN_UPDATE{{=}}             YES}}

These options are used to implement usage of {{Mono|make update}} inside of {{Mono|/usr/ports/}} in order to update the ports tree. {{Mono|SUP_UPDATE}} turns the option on, while {{Mono|SUP}} and {{Mono|SUPFLAGS}} are used to control which CVSup program to use and what arguments to pass to it. {{Mono|PORTSSUPFILE}} will need to be set to the location of your ports supfile that you copied previously from the installed examples. Finally {{Mono|SVN_UPDATE}} is used to enable the use of {{Mono|make update}} inside of {{Mono|/usr/src/}} for updating your source tree.

{{Note|## KERNEL/WORLD<br />CPUTYPE?{{=}}               native<br />CFLAGS{{=}}                 -O3 -pipe -funroll-loops -ffast-math -fno-strict-aliasing<br />COPTFLAGS{{=}}              -O2 -pipe -funroll-loops -ffast-math -fno-strict-aliasing<br />INSTALL_NODEBUG{{=}}        YES<br />KERNCONF{{=}}               CHLOE<br />.if ${.CURDIR:M*/usr/src/*} {{!}}{{!}} ${.CURDIR:M*/usr/obj/*}<br />MAKEOPTS+{{=}}              -j8<br />.endif}}

For use with ports and buildworld {{Mono|CFLAGS}} are used for passing settings when compiling C code. {{Mono|-O3}} uses the largest number or practical optimizations (level 3), in the process of doing so however it sacrifices binary size for speed. {{Mono|-pipe}} causes code to be piped between processes during compilation rather than using temporary files, this has obvious I/O advantages. {{Mono|-funroll-loops}} causes iterating loops with a known number of iterations to be unrolled into faster executions. {{Mono|-ffast-math}} breaks IEEE/ANSI strict math rules; one way it does this is by assuming that the square root of numbers are non-negative. This shouldn't be used if you're compiling code that relies on the exact implementation of IEEE or ANSI rules for math functions. Unless you're writing your own code that does exactly this you shouldn't have any problems.

The {{Mono|COPTFLAGS}} option is for passing settings when compiling the kernel specifically. Dropping down to an optimization level of 2 as level 3 is known to break kernels (Note: {{Mono|-O}} is the only one that is officially supported). All the other settings being passed are the same as in use with {{Mono|CFLAGS}}.

{{Note|## DOCUMENTATION<br />DOC_LANG{{=}}               en_US.ISO8859-1}}

This is used to make sure all of the documentation that is compiled on the system is in the correct language/encoding.

{{Note|## PERFORMANCE<br />BUILD_OPTIMIZED{{=}}        YES<br />BUILD_STATIC{{=}}           YES<br />NO_PROFILE{{=}}             YES<br />OPTIMIZED_CFLAGS{{=}}       YES<br />WITH_CPUFLAGS{{=}}          YES<br />WITH_MMX{{=}}               YES<br />WITH_OPTIMIZED_CFLAGS{{=}}  YES<br />WITH_SSE{{=}}               YES<br />WITH_THREADS{{=}}           YES<br />WITHOUT_DEBUG{{=}}          YES}}

This is a set of default ports knobs that will decrease compilation time, yet have no effect on how ports operate and function. Most of these have to do with enabling CPU-related settings.

{{Note|WITHOUT_X11{{=}}            YES}}

This settings can optionally be added to the list of settings above if you are building a server that will not be running Xorg.

{{Note|## PORTS<br />.if !empty(.CURDIR:M*/usr/ports/*)<br />WRKDIRPREFIX{{=}}           ${PORTSDIR}/obj<br />NOPORTDATA{{=}}             YES<br />NOPORTDOCS{{=}}             YES<br />#NOPORTEXAMPLES{{=}}         YES<br />FORCE_MAKE_JOBS{{=}}        YES<br />MAKE_JOBS_NUMBER{{=}}       8<br />#UNSAFE_PORTS{{=}}           this/port<br />#UNSAFE_PORTS+{{=}}          that/port<br />.for port in ${UNSAFE_PORTS}<br />DISABLE_MAKE_JOBS{{=}}      YES<br />.endfor<br /><br />WITH_ACPI{{=}}              YES<br />WITH_LINUX{{=}}             YES<br />WITHOUT_GSSAPI{{=}}         YES<br />WITHOUT_IPV6{{=}}           YES<br />WITHOUT_JAVA{{=}}           YES<br />WITHOUT_KERBEROS{{=}}       YES<br />WITHOUT_NAS{{=}}            YES<br />WITHOUT_NLS{{=}}            YES<br /># Xorg<br />WITH_ASPELL{{=}}            YES<br />WITH_GTK2{{=}}              YES<br />WITH_IMLIB2{{=}}            YES<br />WITH_MPLAYER{{=}}           YES<br />WITH_NVIDIA_GL{{=}}         YES<br />WITH_UTF8{{=}}              YES<br />WITH_XFT{{=}}               YES<br />WITHOUT_ARTS{{=}}           YES<br />WITHOUT_ESOUND{{=}}         YES<br />WITHOUT_GCONF{{=}}          YES<br />WITHOUT_GNOME{{=}}          YES<br />WITHOUT_GNOMEVFS{{=}}       YES<br />WITHOUT_GNOMEVFS2{{=}}      YES<br />WITHOUT_GSTREAMER{{=}}      YES<br />WITHOUT_GTK1{{=}}           YES<br />WITHOUT_GTKSPELL{{=}}       YES<br />WITHOUT_HAL{{=}}            YES<br />WITHOUT_ISPELL{{=}}         YES<br />WITHOUT_KDE{{=}}            YES<br />WITHOUT_NAUTILUS{{=}}       YES<br />WITHOUT_QT{{=}}             YES<br />WITHOUT_XINE{{=}}           YES<br />WITHOUT_XMMS{{=}}           YES<br />.endif}}

These are all wrapped up in an if statement as to only apply to ports. To start, setting {{Mono|WRKDIRPREFIX}} will change the working directory used to extract/compile ports from. {{Mono|NOPORTDATA}}, {{Mono|NOPORTDOCS}}, and {{Mono|NOPORTEXAMPLES}} are the three settings for turning off the installation of additional data and examples in {{Mono|/usr/local/share}} and the installation of documentation in {{Mono|/usr/local/doc}}. {{Mono|FORCE_MAKE_JOBS}} turns on multithreaded compiling of ports while {{Mono|MAKE_JOBS_NUMBER}} controls how many to run in parallel. Typically you will want to set this to a number that is double the amount of CPU cores you have. Then directly below this commented out is the example of how to add ports to the list that do not compile with multithreaded compilation turned on. Then accordingly the for statement and {{Mono|DISABLE_MAKE_JOBS}} will turn off multithreading for said ports. Finally I have a list of typical ports knobs I use with all of my systems (these are completely optional, and the Xorg ones can easily be left out on servers).

{{Note|## USER<br />.if !empty(.CURDIR:M*/usr/ports/*)<br />WITH_OPENSSH_CHROOT{{=}}          YES<br />WITHOUT_HUGE_STACK_SIZE{{=}}      YES<br />WITHOUT_PERL_64BITINT{{=}}        YES<br />PERL_MALLOC{{=}}          YES<br />.endif<br /><br />BROWSER{{=}}                      firefox<br />WITH_BROWSER{{=}}                 firefox<br />OVERRIDE_LINUX_BASE_PORT{{=}}     f10<br />OVERRIDE_LINUX_NONBASE_PORTS{{=}} f10<br />PYTHON_VERSION{{=}}               2.7<br />PYTHON_DEFAULT_VERSION{{=}}       python2.7}}

Lastly we have the user ports knobs, this is where you should add in your custom ports knobs (either per port or in general for the whole ports tree). Next I have set my default web browser to firefox, the linux emulator port default to f10, and then python has been set to use version 2.7.

===src.conf===
The {{Mono|/etc/src.conf}} contains settings that apply when building the FreeBSD source tree, similar to ports knobs these settings effect what does or doesn't get built into the source tree. It is a good idea to take a look at the manual page for {{ManPage|man=src.conf|section=5}}, as configuring this file is very system specific. These are somewhat generic options but you should review each and every one just to make sure your system isn't different in some way to make you need said option.

{{Note|WITH_BIND_LIBS{{=}}         YES<br />WITH_EXAMPLES{{=}}          YES<br />WITHOUT_ATM{{=}}            YES<br />WITHOUT_CALENDAR{{=}}       YES<br />#WITHOUT_CLANG{{=}}          YES<br />WITHOUT_GCOV{{=}}           YES<br />#WITHOUT_GDB{{=}}            YES<br />WITHOUT_HTML{{=}}           YES<br />WITHOUT_I4B{{=}}            YES<br />WITHOUT_IPFILTER{{=}}       YES<br />WITHOUT_IPX{{=}}            YES<br />WITHOUT_IPX_SUPPORT{{=}}    YES<br />WITHOUT_NCP{{=}}            YES<br />WITHOUT_NLS{{=}}            YES<br />WITHOUT_NLS_CATALOGS{{=}}   YES<br />WITHOUT_PROFILE{{=}}        YES<br />WITHOUT_RCMDS{{=}}          YES<br />WITHOUT_SHAREDOCS{{=}}      YES<br /><br />## SERVICES<br />WITHOUT_BIND_DNSSEC{{=}}    YES<br />WITHOUT_BIND_ETC{{=}}       YES<br />WITHOUT_BIND_MTREE{{=}}     YES<br />WITHOUT_BIND_NAMED{{=}}     YES<br />WITHOUT_GSSAPI{{=}}         YES<br />WITHOUT_KERBEROS{{=}}       YES<br />WITHOUT_OPENSSH{{=}}        YES<br />WITHOUT_SENDMAIL{{=}}       YES<br /><br />## HARDWARE<br />WITHOUT_BLUETOOTH{{=}}      YES<br />WITHOUT_LPR{{=}}            YES<br />WITHOUT_WIRELESS{{=}}       YES<br /><br />## ZFS<br />#LOADER_ZFS_SUPPORT{{=}}     YES<br />WITHOUT_CDDL{{=}}           YES}}

Couple things to keep in mind. If you are running ZFS you need to comment out {{Mono|WITHOUT_CDDL}} and uncomment {{Mono|LOADER_ZFS_SUPPORT}}. If you use a wireless network card instead of a wired one and/or bluetooth, uncomment out {{Mono|WITHOUT_WIRELESS}} and/or {{Mono|WITHOUT_BLUETOOTH}}. Otherwise review over these and make sure they don't conflict with your system or what you are trying to do with it.

==Ports Tree==
The FreeBSD Ports and Packages Collection (ports) offers a simple way for users and administrators to install applications. As there are a few basic system applications we will be needing to install lets get ports up to date. To do so we will be using {{ManPage|man=csup|section=1}} and an example supfile left from installation.

{{Code|mkdir ~/csup/}}

{{Code|cp /usr/share/examples/cvsup/ports-supfile ~/csup/}}

{{Code|csup -L 2 -h cvsup10.us.freebsd.org ~/csup/ports-supfile}}

This will take a moment or two depending on the speed of your connection to the internet and the CVSup server you chose.<ref>{{Cite web||url=http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/cvsup.html#CVSUP-MIRRORS|title=CVSup Sites}}</ref> Once the ports collection is installed the next step is to setup some ports, kernel and world build options.

===Required Ports===
Now time to build some ports to assist us in hardening our system. First obviously you should download your text editor of choice, personally I like to use GNU nano but you can use whatever you like. Sudo (su "do") allows a system administrator to delegate authority to give certain users (or groups of users) the ability to run some (or all) commands as root or another user while providing an audit trail of the commands and their arguments. Subversion (or svn) is a software versioning and a revision control system distributed under the Apache license, this will be used to keep the source tree up-to-date.

{{Code|cd /usr/ports/editors/nano ; make install clean}}

{{Code|cd /usr/ports/security/sudo ; make install clean BATCH{{=}}"YES"}}

{{Code|cd /usr/ports/devel/subversion ; make install clean}}

==(Temp) Creation Notes==
03. Install the default editor, sudo and subversion.

    bsd# cd /usr/ports/editors/nano; make install clean;
    bsd# cd /usr/ports/security/sudo; make install clean;
    bsd# cd /usr/ports/devel/subversion; make install clean;
    bsd# setenv EDITOR nano

04. Change the way passwords are stored to blowfish, fetch login.conf, run the database
    rebuiler, then reset the root password.
   
    bsd# cd /etc
    bsd# fetch http://privatebox.org/bsd/etc/auth.conf
    bsd# fetch http://privatebox.org/bsd/etc/login.conf
    bsd# cap_mkdb /etc/login.conf
    bsd# passwd
   
    To double check that these changes work you should open up the /etc/master.passwd
    file and make sure the root password starts with "$2a"

05. Clean out the default user files directory

    bsd# cd /usr/share/skel/; rm dot.rhosts;
    bsd# fetch http://privatebox.org/bsd/home/dot.cshrc
    bsd# fetch http://privatebox.org/bsd/home/dot.login
    bsd# fetch http://privatebox.org/bsd/home/dot.login_conf
    bsd# fetch http://privatebox.org/bsd/home/dot.mail_aliases
    bsd# fetch http://privatebox.org/bsd/home/dot.profile
	bsd# cp dot.cshrc ~/.cshrc; cp dot.login ~/.login; cp dot.login_conf ~/.login_conf; 
	bsd# cp dot.mail_aliases ~/.mail_aliases; cp dot.profile ~/.profile;
    bsd# cd; rm .k5login;
    bsd# touch /etc/COPYRIGHT
    bsd# chmod g+rwx /usr/src /usr/obj

06. Add a users group, then modify the default adduser settings, remove the toor user
    account and add yourself a shell user that you will now always ssh from (instead
    of root).

    bsd# pw groupadd users
    bsd# adduser -C
       Uid (Leave empty for default):
       Login group []: users
       Enter additional groups []:
       Login class [default]: users
       Shell (sh csh tcsh nologin) [sh]: tcsh
       Home directory [/home/]:
       Home directory permissions (Leave empty for default): 0700
       Use password-based authentication? [yes]:
       Use an empty password? (yes/no) [no]:
       Use a random password? (yes/no) [no]:
       Lock out the account after creation? [no]:
       Pass Type  : yes
       Class      : users
       Groups     : users
       Home       : /home/
       Home Mode	: 0700
       Shell      : /bin/tcsh
       Locked     : no
       OK? (yes/no): yes
       Re-edit the default configuration? (yes/no): no
       Goodbye!
    bsd# pw userdel toor
    bsd# adduser
       Username   : k
       Password   : *****
       Full Name  : *****
       Uid        : 420
       Class      : root
       Groups     : wheel
       Home       : /home/k
       Home Mode	: 0700
       Shell      : /bin/tcsh
       Locked     : no
       OK? (yes/no): yes
       adduser: INFO: Successfully added (k) to the user database.
       Add another user? (yes/no): no
       Goodbye!

07. Update the doc and source tree from SVN, then copy over the kernel configuration
    file and then check it into the RCS.

    bsd# cd /usr/src/
    bsd# svn checkout svn://svn.freebsd.org/base/stable/8 /usr/src
    bsd# cd /usr/src/sys/i386/conf
    	(This would be /usr/src/sys/amd64/conf on an amd64 system)
    bsd# fetch http://privatebox.org/bsd/home/HUB
    bsd# ci -u HUB

08. Time to upgrade FreeBSD to its most current version, we will benchmark also.

    bsd# cd /usr/src
    bsd# buildworld

    This step will take ~30m-1h.

    bsd# buildkernel
    bsd# sudo make installkernel
    bsd# sudo reboot

    This is the hope and pray that you did everything right stage... When the box
    comes back up login via ssh and su to root. Then start up mergemaster preperation
    and then finally installworld and run mergemaster again (rule of thumb for running
    mergemaster, if your RCS'd it don't overwrite it). Then reboot the machine yet
    again.

    bsd# cd /usr/src
    bsd# mmp

    bsd# sudo make installworld
    bsd# mm
    bsd# sudo reboot

09. Install openssh_portable to replace standard ssh, then replace the sshd_config file
    and restart sshd

    bsd# cd /usr/ports/security/openssh-portable; sudo make install clean;
    bsd# cd /etc/ssh
    bsd# sudo fetch http://privatebox.org/bsd/etc/ssh/sshd_config
    bsd# sudo fetch http://privatebox.org/bsd/etc/ssh/sshd_banner
    bsd# sudo /usr/local/etc/rc.d/openssh onestart

	NOTE: Please at this time make sure you can login to ssh, if you can not, then
	      you need to review the steps and retrace what you did.

10. SSH back into the box and su to root. Then, retrieve all new modified system
    files into your /etc folder. Then check them all into the RCS.

    bsd# cd /etc
    bsd# fetch http://privatebox.org/bsd/etc/rc.conf
    bsd# fetch http://privatebox.org/bsd/etc/crontab
    bsd# fetch http://privatebox.org/bsd/etc/hosts
    bsd# fetch http://privatebox.org/bsd/etc/hosts.allow
    bsd# fetch http://privatebox.org/bsd/etc/newsyslog.conf
    bsd# fetch http://privatebox.org/bsd/etc/periodic.conf
    bsd# fetch http://privatebox.org/bsd/etc/sysctl.conf
    bsd# fetch http://privatebox.org/bsd/etc/syslog.conf
    
11. Install portupgrade/portaudit and audit already installed ports.

    bsd# cd /usr/ports/ports-mgmt/portaudit
    bsd# sudo make install clean
    bsd# cd ../portupgrade && sudo make install clean
    bsd# cd ../pkg_cutleaves && sudo make install clean
    bsd# sudo portaudit -Fda

12. Make /tmp the only temp.

    bsd# mv /var/tmp/* /tmp; rm -rf /var/tmp; ln -s /tmp /var/tmp

    (NOTE: If you recieve the message "Operation not permitted" on any of the
    files when you try to move/remove them you need to "chflags noschg
    <file/dir>")

13. Restrict access to crontab to root and your shell user account only. Then
    set proper permissions on the file. Then enable accounting.

    bsd# echo 'root' > /var/cron/allow; echo 'k' >> /var/cron/allow;
    bsd# chmod 0600 /var/cron/allow

14. Run the secure_me.sh file to set proper permissions to all system files.

    bsd# cd; mkdir scripts; cd scripts;
    bsd# fetch http://privatebox.org/bsd/other/secure_me.sh; chmod +x secure_me.sh;
    bsd# ./secure_me.sh

==Notes==
<references/>

[[Category:FreeBSD]]