Copyright © 2001, 2002, 2003, 2004 Joost van Baal
| Revision History | ||
|---|---|---|
| Revision 20040804 | $Date: 2004/10/15 08:17:14 $ | |
| $Id: manual.dbx,v 1.26 2004/10/15 08:17:14 joostvb Exp $ | ||
systraq Is a small set of simple scripts monitoring your system, and warning you when system files change.
systraq Daily sends you an email listing the state of your system. Furthermore, if critical files have changed, you'll get an email within a shorter notice. It consists of few very small shell scripts. It's written for Debian GNU/Linux, but very likely runs on any Unix like operating system. (Examples and default configuration will likely be somewhat Debian centered, 'though.)
It can help you keeping your system secure. However, make sure you really want to do the monitoring this script offers: it might not comply with your site's privacy policy. Getting informed when users' config file change might be too intrusive.
I have some *BSD boxes, which regularly mail me stuff like:
checking setuid files and devices:
checking for uids of 0:
root 0
toor 0
checking for passwordless accounts:
hille.mdcc.cx login failures:
Oct 11 11:31:52 hille login: 1 LOGIN FAILURE ON ttyv0
Oct 11 11:31:52 hille login: 1 LOGIN FAILURE ON ttyv0, .^[^[^[[MS
hille.mdcc.cx refused connections:
Disk status:
Filesystem 1K-blocks Used Avail Capacity Mounted on
/dev/ad0s1a 39647 27927 8549 77% /
/dev/ad0s1f 1016303 857921 77078 92% /usr
/dev/ad0s1g 7026508 6219148 245240 96% /usr/home
/dev/ad0s1e 19815 6712 11518 37% /var
procfs 4 4 0 100% /proc
Network interface status:
Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll
lp0* 1500 <Link#1> 0 0 0 0 0
ed0 1500 <Link#2> 00:00:e8:6b:a9:3b 651828 1177 4029190 4 36522
======
/etc/sshd_config diffs (OLD < > NEW)
======
1c1,11
< # $OpenBSD: mailer.conf,v 1.3 2000/04/06 18:24:19 millert Exp $
---
> # This is ssh server systemwide configuration file.
>
> Port 22
> #Protocol 2,1
On OpenBSD boxes, the shellscripts /etc/daily, /etc/weekly and /etc/monthly
kick off the process to generate these status mails. The shellscript
/etc/security is called, as well as the mtree(8)
command.
I very much like this system, taking care of the automatic monitoring of my system. I run GNU/Linux also, these boxes lacked such a system (tripwire is too heavyweigth for my demands.) This system seemed not very portable to GNU/Linux, unfortunately. (Which is another way of stating: I'm too lazy to port the complete system.)
Jeremy Weatherford wrote FileTraq for his Red Hat Linux box. This small tool could be regarded as a first estimate to what I wanted. Jeremy runs it as root, I believe. I want to avoid that as much as possible. I do want to monitor files like /etc/shadow, but I do not want to get the diff emailed when these change. I do want to get a notice if such a file changes. Christoph Lameter's debsums is a tool, for monitoring files installed from Debian packages, which has functionality like this. On Debian systems, there's checksecurity(8) in the cron package, which monitors permissions on device files.
So, I mixed ideas of the BSD 'daily run output' style emails with FileTraq and some other tools. That's systraq.
You might need the GNU version of utilities like cut and ls: I've only tested sytraq on a GNU/Linux system. The systraq tool works nice with the Debian debsums package; however, systraq is useful too on systems lacking this package.
You need Jeremy Weatherford's FileTraq. However, beware! Jeremy no longer seems to maintain FileTraq. You'll need an up to date version; the Debian package filetraq >= 0.2-10 by Sergio Talens-Oliag is fine (to be sure Debian bug #251010 is fixed). If you are on a Debian system, you know how to get this. If you are on another system, you can get the Debian filetraq version from the master ftp site or from any other mirror. Be sure to at least get the files filetraq_0.2.orig.tar.gz and filetraq_0.2-10.diff.gz (or a later version). You can apply the diff with any patch.
Run
$ ./configure
$ make
# make install
This will install st_snapshot and
systraq in /usr/local/bin/. Furthermore, it will install
documentation in /usr/local/share/doc/systraq/. Configuration
files will get installed in /usr/local/etc/systraq/.
Create a dedicated systraq user account. E.g.
# adduser --system --home /usr/local/var/lib/systraq --disabled-password systraq
This user will read worldreadable files, and write files under /usr/local/var/state/systraq/. Cronjobs will get
run as this user, you might want to create a
~systraq/.forward (or whatever your MTA uses), to get
these job's output in your mailbox.
Example configuration files are distributed with this manual. (On Debian systems, the examples could be used as reasonable defaults, except for the filetraq.conf file, which needs to be generated for your particular system.) All configuration files are line oriented, lines with a leading # are ignored. We give some descriptions here.
The files listed in /usr/local/etc/systraq/filetraq.conf will be checked by filetraq for changes in content every half hour. Diff's will be emailed to the administrator. The files snapshot_pub.stat and snapshot_root.stat should be listed here, as well as systraq.md5sums (all these files reside in /usr/local/var/state/systraq/). It is advisable to also list every worldreadable file under /etc/ (and possibly /usr/local/etc/) here. You also might like to list each user's ~/.ssh/authorized_keys and ~/.ssh/authorized_keys2 file here.
All files listed in filetraq.conf should exist on your system, and should be worldreadable. (You can monitor non-world readable files in /etc/ by adding them to snapshot_root.list).
You could create filetraq.conf using this Makefile:
filetraq.main.conf:
echo '# $@: automatically generated' > $@
( find /etc -perm -a+r -type f | sort ; \
ls -1 /home/*/.ssh/a* ) | sort >> $@
filetraq.conf: filetraq.main.conf filetraq.tail.conf
echo '# $@: generated from $<' | \
cat - filetraq.main.conf filetraq.tail.conf > $@
where filetraq.tail.conf is
#
/usr/local/etc/systraq/snapshot_pub.list
/usr/local/etc/systraq/snapshot_pub.homelist
/usr/local/etc/systraq/snapshot_root.list
/usr/local/etc/systraq/snapshot_root.homelist
/usr/local/etc/systraq/filetraq.conf
#
/usr/local/var/state/systraq/snapshot_pub.stat
/usr/local/var/state/systraq/snapshot_root.stat
/usr/local/var/state/systraq/systraq.md5sums
#
; that might get something useful, as a starter.
If you don't like filetraq's default diff style, but, like me, prefer unified diff, do
# rm -f /etc/default/filetraq
# ln -s /usr/local/etc/systraq/filetraq.default /etc/default/filetraq
Daily, st_snapshot will check all files as listed in its configuration files, aka listfiles. These listfiles are /usr/local/etc/systraq/snapshot_{pub,root}.list and /usr/local/etc/systraq/snapshot_{pub,root}.homelist. These files are installed when running make install.
snapshot_pub.list Should contain all world readable files for which we want to monitor existence, ownership, permissions and changes in content. It should contain /usr/local/var/state/systraq/systraq.md5sums too. snapshot_root.list should contain all files which are not world readable, we wanna monitor. snapshot_{pub,root}.homelist should contain files we expect to find in homedirectories of users. All users homedirectories are scanned for files listed in these two listfiles. Think of files like shell startup scripts and stuff in ~/.ssh/ and ~/.rhosts. You might want to add .gnupg/revoke.asc and .gnupg/secring.gpg too.
If a file listed in a listfile is a directory, all files residing in this directory, or any subdirectory thereof, gets counted in. Shell wildcards are allowed in the listfiles.
Inspect all files listed in the listfiles, and decide wether their content is ok for your securitypolicy. Especially, the authorized_keys files need inspection. Once you're happy with their contents, create the /usr/local/var/state/systraq/ directory, and make sure the systraq user can write to it. Then, run st_snapshot manually:
# su -s /bin/sh systraq
$ st_snapshot pub > /usr/local/var/state/systraq/snapshot_pub.stat
and, as root:
# st_snapshot root > /usr/local/var/state/systraq/snapshot_root.stat
Inspect the permissions as listed in the output files, and decide wether you're
happy with them. Check if all files listed should really be on your system.
(One could argue about wether one should have ~/.netrc,
~/.rhosts, ~/.ssh/identity,
~/.shosts, /etc/exports,
/etc/*hosts.equiv . Of course, this depends on your
planned use of the system.) If you're not happy, fix the permissions and
ownerships. You might like to take a look at the
OpenBSD /etc/security script to get inspiration.
Make sure you trust all binary files, which are not in Debian packages (e.g. stuff in /usr/local/bin/), as they are on your system now. (You could e.g. reinstall them from trusted sources.) Once you feel safe, generate a file containing md5sums of these files. You can generate this by running e.g., as user systraq,
$ md5sum `find /usr/local/sbin/ /usr/local/bin/ /usr/local/lib/ \
/usr/local/share/ -type f | sort` > \
/usr/local/var/state/systraq/systraq.md5sums
Make sure you trust all files in your filetraq.conf file, and create the directory /usr/local/var/state/systraq/filetraq/. Then run, as user systraq,
$ filetraq /usr/local/etc/systraq/filetraq.conf \
/usr/local/var/state/systraq/filetraq
to create the first filetraq backup.
The systraq-version/etc/systraq file is installed as /usr/local/etc/cron.d/systraq. Activate it, by doing
# ln -s /usr/local/etc/cron.d/systraq /etc/cron.d/systraq
This makes sure filetraq gets run every half hour,
systraq gets run daily, and the systraq status files get
updated by running st_snapshot each hour.
When a user is added to the system: update filetraq.conf with this user's authorized_keys (or ~/.ssh/authorized_keys2).
filetraq.conf needs maintenance also once files listed there have been removed by system upgrades, or once files have been added to e.g. /etc/.
In case Debian packages are installed with missing /var/lib/dpkg/info/*.md5sums file, things break. Consult the examples section in the debsums manpage, for a hint on how to deal with these broken packages. Alternatively, one can do:
debsums -s > /tmp/sums 2>&1
grep 'no md5sums for' /tmp/sums | awk '{print $5}' > /tmp/pkgs
check the contents of /tmp/pkgs.
apt-get update
apt-get --reinstall install `cat /tmp/pkgs`
debsums --silent --generate=missing,keep `cat /tmp/pkgs`
apt-get clean
When installing or upgrade stuff in /usr/local, be sure to update /usr/local/var/state/systraq/systraq.md5sums with the correct md5sums.
We list all files used by the systraq system, along with a short description of their role.
Files used
homedir of systraq user.
stores systraq status files, should be writable by systraq user.
stdout of st_snapshot, listing permissions, ownership and md5sums of some files, both publicly readable, as well as non-world readable.
configuration file for filetraq, listing files to get monitored.
configutation files for st_snapshot, listing both publicly readable, as well as non-world readable files to get monitored, as well as files to be found in homedirectories.
md5sums of binary files not in Debian packages, verified by running systraq.
systraq runs various system commands, to inspect the state of the system: what is it doing now, what has it been doing recently, are we running to hardware limitations. It inspect some files in users' homedirectories, as well as some system files, for frequently seen flaws. E.g. unsafe umask setting in shell startup scripts, or unsafe PATH in these scripts. It runs debsums, to check md5sums as stated in packaging files with the sums of the actual files running the system. It runs md5sum to check md5sums as locally maintained in /usr/local/var/state/systraq/systraq.md5sums.
The st_snapshot command comes with its own manpage, distributed with this manual.
Systraq is maintained using CVS on topaz.conuropsis.org. If you have access, you should be able to do:
$ CVSROOT=:ext:topaz.conuropsis.org:/var/cvs cvs co ad1810.com/packages/systraq $ less ad1810.com/packages/systraq/bootstrapIf you don't have CVS write access, you can check http://mdcc.cx/~joostvb/packages/systraq/ for a reasonable fresh copy of the CVS.
There is a st_snapshot manpage. You can mail me at
<joostvb-systraq-20041015@mdcc.cx>.
I believe diffmon does about the same as this tool.
FAM (File Alteration Monitor) could be used by systraq (instead of cron): it is for a particular process to "subscribe" to changes to a file / directory. FAM then implements the system-dependent best way to do that (e.g. dnotify on modern Linux) and, if more than one process is interested in the same file, centralises the polling (if polling is necessary), so that less resources are taken in total.
Aide and Osiris are big packages for use in sites where demands are high.