Posts Tagged ‘Standards’

A Brief Introduction to auditd

2013-01-18 by scottpack. 6 comments

The auditd subsystem is an access monitoring and accounting for Linux developed and maintained by RedHat. It was designed to integrate pretty tightly with the kernel and watch for interesting system calls. Additionally, likely because of this level of integration and detailed logging, it is used as the logger for SELinux.

All in all, it is a pretty fantastic tool for monitoring what’s happening on your system. Since it operates at the kernel level this gives us a hook into any system operation we want. We have the option to write a log any time a particular system call happens, whether that be unlink or getpid. We can monitor access to any file, all network traffic, really anything we want. The level of detail is pretty phenomenal and, since it operates at such a low level, the granularity of information is incredibly useful.

The biggest downfall is actually a result of the design that makes it so handy. This is itself a logging system and as a result does not use syslog. The good thing here is that it doesn’t have to rely on anything external to operate, so a typo in your (syslog|rsyslog|syslog-ng).conf file won’t result in losing your system audit logs. As a result you’ll have to manage all the audit logging using the auditd suite of tools. This means any kind of log collection, organization, or archiving may not work with these files, including remote logging. As an aside, auditd does have provisions for remote logging, however they are not as trivial as we’ve come to expect from syslog.

Thanks to the level of integration that it provides your auditd configurations can be quite complex, but I’ve found that there are primarily only two options you need to know.

  1. -a exit,always -S <syscall>
  2. -w <filename>

The first of these generates a log whenever the listed syslog exits, and whenever the listed file is modified. Seems pretty easy right? It certainly can be, but it does require some investigation into what system calls interest you, particularly if you’re not familiar with OS programming or POSIX. Fortunately for us there are some standards that give us some guidance on what to look out for. Let’s take, for example, the Center for Internet Security Red Hat Enterprise Linux 6 Benchmark. The relevant section is “5.2 Configure System Account (auditd)” starting on page 99. There is a large number of interesting examples listed, but for our purposes we’ll whittle those down to a more minimal and assume your /etc/audit/audit.rules looks like this.

# This file contains the auditctl rules that are loaded
# whenever the audit daemon is started via the initscripts.
# The rules are simply the parameters that would be passed
# to auditctl.
# First rule - delete all
-D

# Increase the buffers to survive stress events. # Make this bigger for busy systems -b 1024 -a always,exit -S adjtimex -S settimeofday -S stime -k time-change -a always,exit -S clock_settime -k time-change -a always,exit -S sethostname -S setdomainname -k system-locale -w /etc/group -p wa -k identity -w /etc/passwd -p wa -k identity -w /etc/shadow -p wa -k identity -w /etc/sudoers -p wa -k identity -w /var/run/utmp -p wa -k session -w /var/log/wtmp -p wa -k session -w /var/log/btmp -p wa -k session -w /etc/selinux/ -p wa -k MAC-policy # Disable adding any additional rules - note that adding new rules will require a reboot -e 2

Based on our earlier discussion we should be able to see that we generate a log message every time any of the following system calls exit: adjtimex, settimeofday, stime, clock_settime, sethostname, setdomainname. This will let us know whenever the time gets changed or if the host or domain name of the system get changed.

We’re also watching a few files. The first four (group, passwd, shadow, sudo) will let us know whenever users get added, modified, or privileges changed. The next three files (utmp, wtmp, btmp) store the current login state of each user, login/logout history, and failed login attempts respectively. So monitoring these will let us know any time an account is used, or failed login attempt, or more specifically whenever these files get changed which will include malicious covering of tracks. Lastly, we’re watching the directory ‘/etc/selinux/’. Directories are a special case in that this will cause the system to recursively monitor the files in that directory. There is a special caveat that you cannot watch ‘/’.

When watching files we also added the option ‘-p wa’. This tells auditd to only watch for (w)rites or (a)ttribute changes. It should be noted that for write (and read for that matter) we aren’t actually logging on those system calls. Instead we’re logging on ‘open’ if the appropriate flags are set.

It should also be said that the logs are also rather…complete. As an example I added the system call rule for sethostname to a Fedora 17 system, with audit version 2.2.1. This is the resultant log from running “hostname audit-test.home.private” as root.

type=SYSCALL msg=audit(1358306046.744:260): arch=c000003e syscall=170 success=yes exit=0 a0=2025010 a1=17 a2=7 a3=18 items=0 ppid=23922 pid=26742 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts4 ses=16 comm="hostname" exe="/usr/bin/hostname" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key="system-locale"
There are gobs of fields listed, however the ones that interest me the most are the various field names containing the letters “id”, “exe” and that ugly string of numbers in the first parens. The first bit, 1358306046.744, is the timestamp of the event in epoch time. The exe field contains the full path tot he binary that was executed. Useful, since we know what was run, but it does not contain the full command line including arguments. Not ideal.

Next we see that the command was run by root, since the euid is 0. Interestingly, the field auid (called audit uid) contains 1000, which is the uid of my regular user account on that host. The auid field actually contains the user id of the original logged in user for this login session. This means, that even though I used “su -” to gain a root shell the auditing subsystem still knows who I am. Using su to gain a root shell has always been the bane of account auditing, but the auditd system records information to usefully identify a user. It does not forgive the lack of command line options, but certainly makes me feel better about it.

These examples, while handy, are also only the tip of the iceberg. One would be hard pressed to find a way to get more detailed audit logging than is available here. To help make our way down the rabbit hole of auditd let’s turn this into a series. We’ll collect ideas for use cases and work up an audit config to meet the requirements, much like what I ended up doing on this security.stackexchange.com answer.

If this sounds like fun let me know in the comments and I’ll work up a way to collect the information. Until then…Happy Auditing!

There will be future auditd posts, so check back regularly on the auditd tag.

 

QotW #16: When businesses don’t protect your data…

2012-01-27 by roryalsop. 1 comments

This week’s blog post was inspired by camokatu‘s question on what to do when a Utility company doesn’t hash passwords in their database.

It seems the utility company couldn’t understand the benefit of hashing the passwords. Wizzard0 listed some reasons why they might not want to implement protection – added complexity, implementation and test costs, changes in procedures etc. and this is often the key battle. If a company doesn’t see this as a risk they want to remediate, nothing will get done. And to be fair, this is the way business risk should be managed, however here it appears that the company just hasn’t understood the risks or isn’t aware of them.

Obviously the consequences of this can range from minimal to disastrous, so most of the answers concentrate on consequences which could negatively impact the customer, and the main one of these is where the database includes financial information such as accounts, banking details or credit card details.

The key point, raised by Iszi, is that if personally identifiable information is held, it must be protected in most jurisdictions (under data protection acts), and if credit card details are held, the Payment Card Industry Data Security Standard (PCI-DSS) requires it to be protected. (For further background information check out the answers to this question on industry best practices). These regulations tend to be enforced by fining companies, and the PCI can remove a company’s ability to use credit card payments if they fail to meet PCI-DSS.

Does the company realise they can be fined or lose credit card payments? Maybe they do but have decided that is an acceptable risk, but I’d be tempted to say in this case that they just don’t appear to get it.

So when they don’t get it, don’t care, or won’t respond in a way that protects you, the customer, what are your next steps?

from tdammers – responsible disclosure :

Contact the company, offer to keep the vulnerability quiet for a limited amount of time, giving them an opportunity to fix it.

In the meantime, make sure you’re not using the compromised password anywhere else, make sure you don’t have any valuable information stored on their systems, and if you can afford to, cancel your account.

from userunknown -

contact their marketing team and explain what a PR disaster it would be if the media learnt about it (no, I’m not suggesting blackmail…:-)

from drjimbob - 3 excellent suggestions:

Submit it to plaintext offenders?

Switch to another utility company?

Lobby your local politicians to pass legislation that companies that do not use secure hashes (e.g., bcrypt or at very least salted hash) on their password data are liable for identity theft damages from any compromise of their systems?

But in addition to those thoughts, which at best will still require time before the company does anything, follow this guidance repeated in almost every question on password security and listed here by Iszi -

Use long and complex passwords for all websites & applications, and do not re-use passwords across any websites & applications. Additionally, limit the information you give these websites & applications to only that which is absolutely necessary for them to serve their purpose

QotW #13: Standards for server security, besides PCI-DSS?

2011-11-11 by roryalsop. 0 comments

The Question of the week this week was asked by nealmcb in response to the ever wider list of standards which apply in different industries. The Financial Services industry has a well defined set of standards including the Payment Card Industry Data Security Standard (PCI-DSS) which focuses specifically on credit card data and primary account numbers, but neal’s core question is this:

Are there standards and related server certifications that are more suitable for e.g. web sites that hold a variety of sensitive personal information that is not financial (e.g. social networking sites), or government or military sites, or sites that run private or public elections?

This question hasn’t inspired a large number of answers, which is surprising, as complying with security standards is becoming an ever more important part of running a business.

The answers which have been provided are useful, however, with links to standards provided by the following:

From Gabe:

Of these, the CIS standards are being used more and more in industry as they provide a simple baseline which should be altered to fit circumstances but is a relatively good starting point out of the box.

Jeff Ferland provided a longer list:

And as I tend to be pretty heavily involved with the ISF, I included a link to the Standard of Good Practice which is publicly available and is exactly what it sounds like: rational good practice in security.

From all these (and many more) it can be seen that there is a wide range of standards which all have a different focus on security- which supports this.josh‘s comment:

As is often noted in questions and answers on this site, the solution depends on what you are protecting and who you are protecting it from. Even similar industries under different jurisdictions may need different protections. Thus I think it makes sense for specific industries and organizations to produce their own standards.

A quick look at questions tagged Compliance shows discussion on Data Protection Act, HIPAA, FDA, SEC guidelines, RBI and more.

If you are in charge of IT or Information Security, Audit or Risk, it is essential that you know which standards are appropriate to you, which ones are mandatory, which are optional, which may be required by a business partner etc., and to be honest it can be a bit of a minefield.

The good thing is – this is one of the areas where the Stack Exchange model works really well. If you ask the question “Is this setup PCI compliant” there are enough practitioners, QSA’s and experienced individuals on the site that an answer should be very straightforward. Of course, you would still need a QSA to accredit, but as a step towards understanding what you need to do, Security.StackExchange.com proves its worth.