Ctf4 Instructions

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Capture the Flag Exercise:
Web Application to Root Via Insecure Configuration
March 10, 2009
by Justin C. Klein Keane
Originally developed for:
University of Pennsylvania, School of Arts and Sciences, Information Security and
Unix Systems group

Table of Contents
Getting Started........................................................................................................2
Conventions Used in this Document.................................................................4
Purpose.............................................................................................................4
Omissions.........................................................................................................4
NOTA BENE.......................................................................................................4
Step 1 – Reconnaissance .........................................................................................5
Scanning with NMAP.........................................................................................6
Step 2 - Discovery ................................................................................................10
Manual Banner Grabbing................................................................................11
Step 3 – Verify........................................................................................................13
Scanning using HTTPrint.................................................................................14
Step 4 – Vulnerability scan.....................................................................................15
Vulnerability Scanning with Nessus................................................................16
Vulnerability Scanning with Nikto...................................................................21
Step 5 – Manual discovery.....................................................................................23
Manual Discovery...........................................................................................24
Step 6 – Gain admin site access............................................................................28
SQL Injection..................................................................................................29
Input Manipulation using Firefox Tamper Data...............................................34
Coaxing Out Error Messages...........................................................................37
Step 7 – Find XSS...................................................................................................40
Step 8 – File include vulnerability...........................................................................42
Step 9 – Crack account passwords.........................................................................47
Exposing and Cracking Apache Passwords.....................................................48
Step 10 – Steal the SSH private key.......................................................................53
Other Unscripted Attack Vectors:...........................................................................61

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About the Project
The LAMPSecurity project is an effort to produce training and benchmarking tools
that can be used to educate information security professionals and test products.
Please note there are other capture the flag exercises (not just the latest
one). Check the SourceForge site to find other exercises available
(http://sourceforge.net/projects/lampsecurity/files/CaptureTheFlag/).
These exercises can be used for training purposes by following this
documentation. Alternatively you may wish to test new tools, using the CTF
virtual machines as targets. This is especially helpful in evaluating the
effectiveness of vulnerability discovery or penetration testing tools.
This documentation may be somewhat out of date with respect to tools used to
compromise the virtual machine. The advent of BackTrack (http://www.backtracklinux.org/) has somewhat obviated the need for an attack image. Downloading
the latest BackTrack linux image should provide all the necessary tools for
completing the exercise.
The username and password for the image can be found in this
documentation. However, the point of the exercise is to discover the root
username and password, so they are not provided up front. If you must have the
credentials to access the virtual image please read the end of the documented
compromise steps.

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Getting Started
The contents of this exercise assume that you are using the LAMPSecurity VMware
image. This is a CentOS based Linux virtual machine preloaded with many of the
attack tools necessary to do a security evaluation or penetration test of a remote
machine. You'll need VMware's free player in order to run the image. You can
download the testing image and the target image from
https://sourceforge.net/projects/lampsecurity. You can download the VMware
player from http://www.vmware.com/download/player.
Once you have the downloaded the target image (LAMPSecCTF.zip) you can unzip
the target using compression software like 7-zip (http://www.7-zip.org). This
should inflate the zip to a single directory called 'CTF4'. Go ahead and start the
virtual machine therein by firing up VMWare Player, clicking the 'Open' icon and
selecting 'CTF4.vmx' from within the CTF4 folder:

Give the virtual machine a few minutes to boot. Once the target is up and
running the first challenge is to determine the IP address of the target. The
easiest way to do this is to look at your VMWare devices on your host computer.
On a windows system you can do this by typing:
C:\> ipconfig /all
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This should reveal the subnets for which VMWare is running. Typically you're
looking for the subnet of the Vmnet8 device.
In the following screenshot you can see the subnet of the VMWare machine is
likely on Vmnet8, or 192.168.229.0/24. We'll use this information to locate the
target later on in the exercise.

Next you'll want to download and inflate the testing image. This is the image that
contains all the discovery and penetration testing tools that you need to complete
the exercise. Download the LAMPSec.zip file and inflate it, it contains one
directory called LAMPSec. Open up VMWare player and then open up the
LAMPSec.vmx file. This will start up the test platform. Once this platform is
booted up you should log in.
The LAMPSec image has one user named 'lampsec'. The password for this user
and the root user is 'lampsec'.
Note that due to licensing restrictions the LAMPSec image doesn't come with
Nessus pre-installed. You can download Nessus from within the LAMPSec image
by using the Firefox web browser, going to http://www.nessus.org, and
downloading the latest version of Nessus for Linux. The latest version as of this
writing is Nessus 3.2.1 for Linux, which is available as an RPM download (Nessus3.2.1-es5.i386.rpm). To install this rpm open a terminal window (Applications →
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Accessories → Terminal) and navigate to the downloaded RPM (likely on the
desktop) using:
$ cd ~/Desktop
$ sudo rpm -ivh Nessus-3.2.1-es5.i386.rpm

Conventions Used in this Document
Arrows are used to indicate progression between menus in a program. For
instance, if you are being instructed to click on the File menu in a program, then
select the Properties option this is denoted using:
File → Properties
All command line instructions are listed in courier fixed font. These will often
include the prompt preceeding the command, such as:
$ ls -lah
It is not necessary to type the '$' as part of the command, it is merely listed for
completeness.

Purpose
This exercise is intended to be an educational experience. In particular it is
designed to demonstrate how misconfiguration and vulnerabilities can be
“chained” together to lead to a complete compromise. There is no system on the
target that is immediately exploitable to become root, but there are problems that
can be exploited in tandem to compromise the root account.

Omissions
This document describes one possible path to the root account. This is by no
means the only way to compromise the target image. Many other paths are
available to become the root user, but for the sake of brevity, and to allow further
exploration, other routes have not been enumerated. Check the final section to
see hints for other ways to attack the target.

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NOTA BENE
Many of the screenshots in this document refer to a target at 192.168.0.6. The
target IP will in fact vary from installation to installation, so be sure to use the IP
address of the target you discover, rather than the one printed in this
documentation!
Also note that although the virtual machine images in this project are being
released GPL open source, I am retaining copyright over the text of this
document. This means you can't reproduce or resell this document without
express written consent of the author. Please be respectful of the many hours
devoted to deriving this work and the fact that it's being freely distributed.

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Step 1 – Reconnaissance
Find the target and discover what services are available on the remote machine
using NMAP.

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Scanning with NMAP
NMAP (the Network MAPper http://nmap.org) can be used to quickly scan large
ranges of IP addresses. NMAP uses a number of techniques to discover ports that
are open on remote machines. Open ports generally indicate available services
that an attacker can interact with, so they are of particular interest to us. Firewall
rules on the target may limit port access, however, so there may be services that
are unavailable from the outside. NMAP will inspect the machine and let us know
what services are available.
NMAP can also analyze TCP/IP fingerprints of remote machines and determine
operating systems and versions running on those machines. Different operating
systems implement networking in subtly different ways and NMAP uses this
information to compare responses to a large database of known OS fingerprints.
NMAP has a graphical interface, but the command line version is often preferable
and is just as full featured. In order to open a command prompt, access the
Terminal program under the Applications menu → System → Terminal, or using the
quick launch icon in the tool bar at the top of the LAMPSec VMware image.
The first thing we should do is run an NMAP scan against the entire target IP
address range (192.168.229.2-192.168.229.254) and discover machines. We
should also take note of our own machine in this range just so we don't attack the
test bed. To do this type:
$ /sbin/ifconfig eth0
And note the IP address. For this example we'll assume it's 192.168.229.135.
Next let's scan the entire subnet with NMAP. To do this we'll use the -F flag, for a
fast scan and we'll specify all the machines on the subnet except for the gateway,
broadcast, and our machine. Open a command prompt and run NMAP by typing:
$ nmap -F 192.168.229.2-134 192.168.229.136-254
This will perform a fast scan of the subnet omitting 192.168.229.1 (the gateway),
192.168.229.255 (the broadcast) and 192.168.229.135 (the local testbed
machine).

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The NMAP scan takes some time but it should find the target:

The scan finds the target in just over a minute and a half. The scan also indicates
that several well known services are running, notably:
port 22
port 35
email
port 80

ssh – a secure shell, used for remote access
smtp – simple mail transport protocol, used for sending and receiving
http – hyper text transport protocol, used for serving web pages

We're ingoring the closed port 631, that's an artiface of VMWare.
Now that we've found the target machine, let's try and do some discovery. This
involves doing a targeted scan and grabbing information we can use to identify
versions of services and the operating system (OS). We can use NMAP to do this,
or we can do banner grabs manually. In this exercise we'll try both methods. In
order to do OS detection we have to listen to packet responses from the target
machine, an operation which requires root permissions. Let's first become root.
In your terminal window type:
$ su

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Enter the password and notice that the prompt character changes from a '$'
symbol to a '#' symbol, indicated that you are now operating as the root user.
Next try NMAP using the command:
# nmap -sV -O -PN 192.168.229.134
the -sV flags will do service version detection, the -O flag will do operating system
fingerprinting, and the -PN flag tells NMAP to skip ICMP pinging the host before
scanning (since we already know the host is up). ICMP pings are used by NMAP to
determine if IP addresses are used, but many devices block ICMP traffic, so it is
worthwhile to use this operation if you suspect a machine may occupy an address
space, but isn't responding to NMAP.
NMAP may take some time to perform this operation, you may want to skip ahead
to the next section “Manual Banner Grabbing” before coming back to view the
results You can open a new tab in the console window with Shift+Ctrl+T (or under
the File menu) .
Once NMAP completes the operating system and version detection, a process that
may take 15 minutes, it will present results in a formatted output. Be sure to read
all of the output to get a better sense of how NMAP came to it's reported
conclusions.
NMAP operating system and version detection output:

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You'll notice that the MAC address of the target is clearly identified as VMWare.
MAC addresses are configurable, and you can easily change this value in VMWare
to make the target look more realistic.
You can also see that NMAP has determined that the target is running Linux, likely
with a 2.6 version kernel. NMAP also discovered that OpenSSH 4.3 is running on
port 22, Sendmail 8.13.5 is running on port 25, and Apache 2.2.0 is running on
port 80. Apache was also able to determine that Apache is reporting that it is
running on the Fedora Linux distribution.
Note that NMAP shows port 631 is in a closed state. This is an artifice of the
Vmware image, and should be ignored for the purposes of this exercise.

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Step 2 - Discovery
Determine the versions of services and operating system running on the target.

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Manual Banner Grabbing
We can go through and perform “banner grabbing” manually using utility
programs like telnet. To do this we simply telnet to the open port and see how the
service responds. Based on our NMAP scan we know that ports 22, 25, and 80 are
open. Let's start with port 22. Telnet to this port using:
$ telnet 192.168.229.134 22

You'll notice that the service responds with the type of service it is, along with the
version (OpenSSH 4.3). You want to take note of this type of information because
it can provide clues about the machine and could also indicate possible
vulnerabilities. Sometimes it is useful to Google the service name and number
plus the word “vulnerability” to see if there are known issues with the service.
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We can continue this exercise, looking at port 25 and port 80. Port 25 should
reveal that the host is running Sendmail version 8.13.5. You'll notice something
odd when you telnet to port 80 though, the server won't respond right away. Try
typing in “GET index.htm” and see what happens:

You can see that the server doesn't respond in an expected manner, but it does
reveal the service and version running (Apache 2.2.0) as well as the hostname
(ctf4.sas.upenn.edu) and the operating system (Fedora) which is a lot of
information!

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Step 3 – Verify
Verify version information using alternative tools.

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Scanning using HTTPrint
We suspect that we're dealing with an Apache server, but let's go ahead and
verify this information using HTTPrint. HTTPrint is a web server fingerprinting
program that operates in much the same way as NMAP's OS fingerprinting. It is
highly accurate and can determine if server banners are telling the truth about
the service (banners can be changed manually so are not necessarily reliable). To
run HTTPrint open a terminal window and navigate to it using:
$ cd ~/bin/httprint_301
You can then run the program using:
$ ./httprint -h 192.168.0.6 -P0 -s signatures.txt
HTTPrint will generate a lot of output as it ranks the likelihood of each service in
it's database matching the target. The important part to look at is the 'Score' and
'Confidence' rankings in the beginning of the output:

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Step 4 – Vulnerability scan
Run a comprehensive vulnerability scan of the target.

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Vulnerability Scanning with Nessus
Vulnerability scanning involves looking at the actual services running and
performing an audit for problems. One industry standard vulnerability scanner is
Nessus, which is available free for download. Nessus will test the services
installed and look for problems, generating a handy report of it's findings. Nessus
has a graphical front end, so you can start it by looking under the Applications
menu for the NessusClient entry.
Nessus runs in a client/server model. The server is already running silently in the
background, but you have to connect the GUI to it so it can scan. Go ahead and
click the “Connect...” button in the bottom left hand corner of Nessus:

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Note that the cached credentials for Nessus may not be right. If you get an error
click the 'Edit' button in the 'Connection Manager' window then replace the login
and password with “lampsec”:

* Note the screenshot is wrong – use the login “lampsec”

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Once connected click the '+' symbol under the left hand 'Nework(s) to scan:'
pane. Select the 'Single host' option in the 'Edit Target' window and type in our
host IP address:

* Note the screenshot is wrong, use the “Host name” value of your discovered
host!

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Click 'Save' then select the 'Default scan policy' in the right hand 'Select a scan
policy:' window and click the 'Scan Now' button at the bottom of the Nessus client.

* Note the screenshot is wrong – use the “Network(s) to scan” value of your
discovered host!
This will begin the scan, which may take some time to complete. The report can
be exported to an HTML file for later viewing. You can expand the left hand tree
under the IP address of the target to view results of the vulnerability scan. The
results are color coded so you can easily pick out which vulnerabilities are the
most dangerous.

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Nessus scan results:

Take some time to read through the results of the scan – you may find some very
interesting information.

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Vulnerability Scanning with Nikto
Nessus is very good at scanning targets to look for vulnerabilities across multiple
services. There are, however, specialized vulnerability scanners tailored for
specific services. Nikto is a popular, open source web application vulnerability
scanner written in Perl. Nikto is extremely good at identifying problems in web
applications. Nikto is a command line program, so we can start it up using:
$ cd ~/bin/nikto
$ ./nikto.pl -host 192.168.229.134
Once Nikto is started it will audit the target web server and applications it finds on
that server. Be sure to pay careful attention to the results, Nikto will often find
very useful information:

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Nikto will find many of the same things that Nessus will, but it will also identify
some unique attributes of the target. One thing to note is that Nikto has
identified that PHP 5.1.2 is powering the web server.
Nikto has also tried to identify specific open source packages that are installed on
the target, you'll notice that Nikto identified Webalizer might be installed and
points out a potential Cross Site Scripting (XSS) vulnerability in versions of that
software.
Nikto also identifies certain scripts that could indicate vulnerabilities that have
not been identified. For instance Nikto points out that /mail/src/read_body.php has
been identified as part of automated scans – indicating it might have a
vulnerability.

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Step 5 – Manual discovery
Perform some manual recovery and exploration of the target system. Map the
target web application(s).

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Manual Discovery
Although tools like Nessus and Nikto are great for identifying potential
vulnerabilities, manually browsing a web application is one of the best ways to
identify problems. One issue with manually surfing around a target, however, is
that information isn't really captured in any systematic way. In order to facilitate
better retention of data, as well as providing a platform to revisit web requests
and potentially tamper with them, attackers often use a local proxy to intercept
requests to a target. In this part of the attack we'll use Paros, which is a Java
based proxy program that has a lot of functionality. You can start up Paros from
the Applications menu → Attack → Paros. If that doesn't work you can try starting
Paros from the command line using:
$ cd ~/bin/paros
$ ./startserver.sh
Once Paros is running we'll start up our web browser (Firefox) and configure it to
use a local proxy. In Firefox select Edit → Preferences, then select the 'Advanced'
icon at the top, then select the 'Network' tab, and click the 'Settings' button.

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In the 'Connection Settings' window, select 'Manual proxy configuration' then fill in
127.0.0.1 for the 'HTTP Proxy' and 8080 for the 'Port':

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Next click 'OK' and your settings will be saved.

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Now browse to the target website 'http://192.168.229.134' you'll notice that Paros
records the call, including the request from the browser and the response:

Take some time to browse around the target website. Be sure to check into the
interesting sites found by Nikto and Nessus. A good place to start looking for
vulnerable targets is the robots.txt file. Robots.txt is a standard file that directs
the activity of web spiders. Webmasters often place the locations of sensitive
applications or directories into the robots.txt file to keep them out of search
engine caches, but this provides a roadmap for attackers to juicy targets.

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Looking at the robots.txt for the target at http://192.168.229.134/robots.txt we
see it lists:
Disallow:
Disallow:
Disallow:
Disallow:
Disallow:

/mail/
/restricted/
/conf/
/sql/
/admin/

It's worth our time to browse to these directories to see what they contain. Take a
moment to browse to each of these URL's and take note of what is installed there.
Can you determine if there is an open source software package installed at that
location? Which directories appear to be password protected. Do you notice any
directories that provide listings of their contents (or indexes)? All of this is useful
information to an attacker, who can use this intelligence to plot an attack path or
find weaknesses in web applications.

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Step 6 – Gain admin site access
Gain access to the /admin portion of the site. Post a new blog posting.

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SQL Injection
We've easily identified the existence of an administrative portion of the target at
http://192.168.229.134/admin. The login form is clearly meant to keep intruders
out. Let's try and log into the form using a classic attack technique that leverages
SQL injection. SQL injection is an attempt to mangle SQL queries written by a
developer by injecting new code. An example of this would be if a developer
wrote the following code:

The developer clearly intends for PHP to parse the SQL statement so it looks
something like:
select * from users where username='name' and pass='password';
However, if an attacker can take control of the value of the variable $username
and $password variables and cause them to contain the value:
' or 1='1
Then as that value is inserted into the above SQL statement, the resulting query
becomes:
select * from users where username='' or 1='1' and pass='' or 1='1'
This SQL statement is open ended enough that it will always return true, and
depending on how the developer has coded the rest of the PHP login function
might allow the attacker to log in as the administrative user. Let's go ahead and
try this route on the admin login page. Enter:
' or 1='1
into both the username and password fields:

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You'll notice that this doesn't work, and we get a “Login failed!” message. This is
a great failure message, as it doesn't indicate if we got the username wrong, the
password wrong, or the query resulted in an error.
Not to be discouraged though, let's take a look at the source of this page. In
Firefox you can press Ctrl+U or use the menus under View → Page Source. If you
look at the source you'll see that there's a piece of JavaScript in the form that is
changing the values we're inserting before submitting them. It looks like this
script is replacing any character that isn't a letter or a number. This is stripping
the spaces and single quotes out of our values, and defeating our attack. Many
developers will use this type of client side validation to limit inputs attackers can
pass.

Fortunately for use, we can bypass this script entirely! If you look back at Paros
you can see our form submission, which has clearly been altered. In the Paros
window take note of the values in our POST request. Look in the pane to the
lower right of Paros to see these values. You'll notice that they don't include any
characters other than alphanumeric ones (no single quotes or spaces). This is a
result of the JavaScript filtering our input.

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Note the values in Paros:

The values that were submitted via POST were 'username=or11&password=or11'
which is clearly not what we intended. Let's use Paros to sidestep this annoying
JavaScript. Expand the bottom window by dragging the divider up. You can barely
see the contents of this pane above the 'History', 'Spider', 'Alerts', and 'Output'
tabs in the screen shot above. Once this bottom pane is expanded in Paros we
can see all our GET and POST requests.

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Once you can view these requests select the POST request at the end of the list,
right click on it, and select 'Resend':

This will open up a new window.

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In the resulting 'Resend' window let's go ahead and change the values of our
POST to the ones we intended, then click the 'Send' button.

You'll notice if you glance down the HTML in the 'Response' tab that we got the
same error. Looks like we can't log in using this tactic.

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Input Manipulation using Firefox Tamper Data
Let's try exploring the same process using an alternative tool. If we go back to
our web browser we can try to bypass the authentication and log into the site
using the Firefox Tamper Data plugin. This plugin allows us to modify browser
requests and form posts on the fly. Start up Tamper Data in Firefox under the
'Tools' menu → Tamper Data. This will bring up the Tamper Data window. Click on
the 'Start Tamper' menu and then go back to the the login form, fill in “test” and
“test” for the username and password and click the 'Log in' button. You'll notice
this brings up the Tamper Data plugin which asks if you want to tamper the data,
click the 'Tamper' button to continue:

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Next, in the Tamper Popup, change the username and password values from
“test” to “' or 1='1” and click “OK”

You'll notice this request fails as well. Looks like we'll have to try another tack. It
could be that our SQL injection is failing because the query isn't written the way
we expect. If we could get the web server to tell us what the query is we'd be in
much better shape. Often times developers will leave error messages in
applications and report when things go wrong. By examining error messages we
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may be able to glean more information about the database back end and queries
being used.

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Coaxing Out Error Messages
One common technique used for attacking dynamic websites is deliberately
inducing errors to view error statements. Error statements often contain a wealth
of information that is helpful to developers, and malicious attackers, but usually is
meaningless to ordinary users. Let's try resubmitting the form using:
' test
as the username and no password. You'll need Tamper Data to do this as the
JavaScript will replace the single quote value otherwise. Passing this value in we
get a handy error message:

This error message enumerates the SQL statement being used, including the table
and columns we're dealing with. Now we can see why our previous requests were
failing. Given the values we were passing in, the resulting SQL statement must
have been:
select user_id from user where user_name = '' or 1='1'
AND user_pass = md5('' or 1='1')
The error message also shows that passwords seem to be stored in an md5
format. In order to bypass the SQL check we need to mangle the query so it looks
like:
select user_id from user where user_name = '' or 1='1'
AND user_pass = md5('') or 1=1 #')
The '#” symbol indicate a comment in MySQL and that part of the statement will
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be ignored. In order to accomplish this we need to use the username:
' or 1='1
and the password:
') or 1=1 #
Go ahead and user Tamper Data to submit these values and you'll see that you've
bypassed the authentication!

You can go ahead and post a fake blog post using the 'Post blog' link just to verify!
Another interesting thing to note is how the authentication is accomplished. If
you look at the cookies that are set in your browser after a successful login using
the Web Developer plugin you'll notice something interesting. If you select the
'Cookies' menu bar then 'View Cookie Information' you'll see that the
authentication set two cookie values. One is the 'logged_in' cookie, which seems
to be set to some sort of timestamp. The other is the 'user_id' cookie. We can
manipulate this cookie value by clicking the 'Edit Cookie' link.

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Try posting a blog, then setting the cookie to another value and posting another
blog. Notice how your user_id changes the value of the poster's name on the blog
page at http://192.168.229.134/index.html?page=blog&title=Blog.

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Step 7 – Find XSS
Find any one of the number of Cross Site Scripting (XSS) vulnerabilities in the site.

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Cross site scripting vulnerabilities are unfortunately fairly ubiquitous across the
internet. These vulnerabilities allow attackers to manipulate page displays. By
themselves they're fairly harmless, but if an attacker can trick a victim into
visiting a page with crafted output they can redirect the user or expose them to
other attack vectors. If an attacker can find a URL that can be used to display
malicious content then they can send that URL to site users, who will trust it, and
attack them. Looking at the URL's for the target site we see a common theme
which may indicate XSS vulnerabilities:
http://192.168.229.134/index.html?title=Home Page
http://192.168.229.134 /index.html?page=blog&title=Blog
http://192.168.229.134 /index.html?page=research&title=Research
http://192.168.229.134 /index.html?page=contact&title=Contact
Let's try changing the “title” variable in the URL. Notice what happens when you
browse to the website:
http://192.168.229.134 /index.html?title=Hello World!!!
You'll notice a subtle change in the display, the title of the page actually contains
your text. If you view the page source you'll see that your title has been injected
into the display.

While this seems innocuous, try entering the URL:
http://192.168.229.134 /?
title=
You'll see that the user is redirected! This could be used to set up a phishing
scam site. Especially if the attacker URL encodes the “title” so that it's more
difficult to pick out the actual value. Since the attacker can use JavaScript they
could even use any number of JavaScript encoding functions.

http://www.MadIrish.net

Step 8 – File include vulnerability
Find the file include vulnerability in the site.

http://www.MadIrish.net
File inclusion vulnerabilities are problems in web applications where attackers can
cause unintended pages to be displayed through a web application. File inclusion
is a time saving method whereby developers can reuse content. For instance,
developers often write a “header” snippit and include it on every single page.
This cuts down on retyping and allows changes to be made in one place and affect
the site universally. Spotting file inclusion is difficult from the outside, but
attackers can look for some common clues. Reviewing the web application at
http://192.168.229.134 you'll notice some common conventions in the URL's
presented in the top navigation bar, which are:
http://192.168.229.134
http://192.168.229.134
http://192.168.229.134
http://192.168.229.134

/index.html?title=Home Page
/index.html?page=blog&title=Blog
/index.html?page=research&title=Research
/index.html?page=contact&title=Contact

it looks as though pages might be included based on the “page” directive. Let's
poke around and see if we can figure out where they might be included.
One good tool for enumerating remote web application is OWASP's DirBuster,
which brute forces URL's. Go ahead and start DirBuster from Applications →
Attack → DirBuster. Type in the URL http://192.168. 229.134 and click the 'Browse'
button and select /home/lampsec/bin/DirBuster-0.12/directory-list-2.3-medium.txt.

http://www.MadIrish.net

Once DirBuster is set up click the 'Start' button and let it run. You'll notice
DirBuster finds quite a few interesting hits. DirBuster will also list response codes
for pages it finds. Note that 302 are redirects and 500 are generally server errors
or access denied messages. Scrolling through the list you'll see that DirBuster
identifies '/inc/header.php' as a valid file. Let's go ahead and browse to the
following URL:
http://192.168.229.134 /inc
You'll notice that directory listing is turned on! You'll also notice that once
DirBuster finishes running it finds the directory 'pages'. Browsing to this directory:
http://192.168.229.134 /pages/
reveals a directory listing that seems to correspond to the URL's we first
discovered:

http://www.MadIrish.net

http://www.MadIrish.net
Let's put these two pieces of information together and see if we can arbitrarily
include the header twice. Let's assume that the PHP is looking in the /pages
directory for a certain page, but we want to include the header file in the /inc
directory. Try the following URL:
http://192.168.229.134 /?page=../inc/header

You'll notice the header gets included twice! It looks like there is a file include
vulnerability in the site. We'll use this vulnerability to expose sensitive data in the
next step.

http://www.MadIrish.net

Step 9 – Crack account passwords
Find the .htpasswd file in the /restricted directory and crack the passwords. Use
one of the cracked passwords to log into the target machine.

http://www.MadIrish.net

Exposing and Cracking Apache Passwords
Apache has a nice way to protect directories by requiring a username and a
password to be used to access them. Unfortunately, the password hashing
Apache uses isn't very strong and if we can get a hold of the .htpasswd file we
might be able to crack one of the passwords. Guessing passwords, or brute
forcing, usually takes one of two forms. We can try a password guessing attack
against an authentication service on the remote machine (like SSH) or, if we can
grab password hashes, we can try to crack them on our local machine. The
second method is preferable because it is faster and stealthier. In order to gain
an Apache password hash out of the .htpasswd file we can't download it directly.
If you try to access the file at:
http://192.168.229.134 /restricted/.htpasswd
You'll get an access denied (forbidden) error. However, if we use the file include
vulnerability we discovered before we can insert this file into the page output and
view it. Let's first try:
http://192.168.229.134 /?page=../restricted/.htpasswd
You'll notice nothing seems to happen. The reason for this is that PHP developers
will commonly try to defeat this attack by forcing only PHP pages to be included.
They do this using code of the form:

So when we request the .htpasswd, what PHP is actually trying to include is
.htpasswd.php, which doesn't exist.

http://www.MadIrish.net
Fortunately for us, PHP is written in C, and C demarcates strings using the null
byte. This means that if we append a null byte to the end of our URL request
(%00 in ASCII URL encoding) the include statement will terminate the filename at
our null byte, failing to append the “.php” file extension. Try the following URL:
http://192.168.229.134 /?page=../restricted/.htpasswd%00
which reveals the contents of the .htpasswd:

If you view the source of this page the contents will be more nicely formatted.

http://www.MadIrish.net
Now that we have the contents of the .htpasswd file it's time to crack them. Copy
the usernames and passwords into a text file using the notepad icon in the
application bar at the top of the LAMPSec image. Copy the included .htpasswd
accounts and passwords into gedit and save the file as htpasswd (no preceding
period) in /home/lampsec/bin/john-1.7.0.2/run.

Now that we have the hashes locally, let's run John the Ripper, a password
cracking program on them. John the Ripper is extremely fast, but it's power is
largely limited by the word list you provide it. You could download a much better
wordlist than the one provided on the LAMPSec image, but the DirBuster wordlists
will work fine for our purposes. To run John the Ripper first change into the correct
directory then fire it up like so:

http://www.MadIrish.net
$ cd ~/bin/john-1.7.0.1/run
$ ./john –wordlist=../../DirBuster-0.12/directory-list-2.3-small.txt
htpasswd

http://www.MadIrish.net
John should run through this list extremely fast and guess at least one password:

Now that we've got a password let's try and log in to see if the password actually
works. Let's try and log into the target using:
$ ssh sorzek@192.168.229.134
When prompted for a password enter our cracked password 'pacman' and you
should get a command prompt that looks like:
[sorzek@ctf4 ~]$
Indicating that you've successfully logged into the remote host! It seems that
Sally Orzek is using the same password for her .htaccess account and her actual
machine account. Go ahead and confirm your new identity using the 'whoami'
command:
[sorzek@ctf4 ~]$ whoami
You may also want to see where you are on the target by printing the current
working direcotry:
[sorzek@ctf4 ~]$ pwd

http://www.MadIrish.net

Step 10 – Steal the SSH private key
Log into and explore the system. Steal an SSH private key and log in as another
user with higher privileges (like an admin).

http://www.MadIrish.net
Now that you've got a local system account there are quite a few more avenues to
exploit the system. It is possible that there are programs or systems installed on
the machine that are vulnerable to local compromises that haven't been patched.
Many systems consider local vulnerabilities to be less of a threat since attackers
must first have a local account to exploit them. However, as we're beginning to
see, any one weakness might be used to exploit another weakness and so on.
Let's begin poking around the target system to see what we can find. We might
fist want to look through the command history for this account. BASH, the
command line we're using, saves a history so you can use the up arrow to repeat
previously issued commands. These commands are saved in .bash_history. We
can view this file using:
$ cat ~/.bash_history
We might also want to see if anyone else is logged into the machine. Attackers
will commonly do this to see if an administrator is logged in who might notice
unusual activity. You can check who all is logged in using the 'w' command like
so:
$ w
Assuming the coast is clear let's see what other users are on the system. There
are two quick ways we might do this, one is to list the /home directory, the other
is to view the password file. You can do either one using:
$ ls /home
or
$ cat /etc/passwd
We may want to read any mail for the sorzek account. We could do this logging
into the webmail interface at http://192.168.0.6/mail, or by perusing her mail
spool using:
$ less /var/spool/mail/sorzek
You can quit less by pressing 'Esc' then ':q', that is the colon character, then q,
and pressing enter.
Let's poke around the /home directory for a moment. First list the contents of the
directory:

http://www.MadIrish.net
$ ls /home
Now let's see if we can poke into any of the other users' home directories.
Looking at the /etc/group file, which lists all the groups on the system, with:
$ cat /etc/group

http://www.MadIrish.net
You'll see there's an admins group, with dstevens and achen as members. These
two accounts likely have more privileges on the machine than the account we've
already compromised. Let's look into the achen home directory with:
$ls -lah /home/achen
You should be able to view the entire contents of the home directory. Ideally
machines should not be configured to allow one user to browse another user's
home directory. By leaving the machine in this configuration attackers that
compromise one account can browse around other accounts, looking for material
like emails, private documents, or other data that could be sensitive or provide
clues about the passwords to other accounts.
Of particular note in the /home/achen directory is the .ssh directory. This directory
is used to hold keys that might be useful for logging into other machines, or even
into this one! SSH can be configured to use 'public key authentication' which
allows users to log into machines using keys rather than passwords. Often, SSH
keys are built with no password for convenience, but this provides an excellent
route to log into a machine if you can steal the 'private key' portion of the SSH
keypair. Let's see if we can find any private keys in achen's home directoty.
Check the directory contents with:
$ ls -lah /home/achen/.ssh
It looks like we can peek into this folder, and what's worse, there appears to be a
private key listed here! Let's view the private key using:
$ cat /home/achen/.ssh/achen_priv.ppk
Because we can view the private key we can steal it. Private keys are nothing
more than text files.

http://www.MadIrish.net
Copy and paste that data out of your command window and into a gedit text file
like we did before with the .htpasswd contents. The file should look something
like:
PuTTY-User-Key-File-2: ssh-rsa
Encryption: none
Comment: rsa-key-20090309
Public-Lines: 4
AAAAB3NzaC1yc2EAAAABJQAAAIB9HrXHbV0tQkPRiM2zG8/1tIgCD2gA3GwsjopS
N+k9OVHLe7OW6+ZRLXNHVP1FJ6BBVcZDV+CxpgAQj8lsIhiyskjbNzs85k7+8aVb
/JTq8KBnikbXLY2YgPVkkgZ1U9zPKzabSCjARrAxDOx1XEFfZ69T2ZyHP1MwfXGi
MTJgxQ==
Private-Lines: 8
AAAAgDzegfJQ4Ticxwv9XSazlZogeYR2MpiilX11xsA24CufWDl6cwsmp2XDFXyl
4v8MW8zB8b/lj+e4imjsAR/ZPHHlGRyGDyUSrJTusp1arl9UNzZgWnOz2kzvyTMP
R5DazAply2MYcvccGrhx7AXbjOsJZRcyh3gDnF0fu718jdTlAAAAQQD1JRPJe/MR
xOSX3D1ZdMUaSwsIopexRcG5GGZX9LNPMs1eyrEigmIkNQ6viwBI766ase/+79Xw
8seUasmkEkCDAAAAQQCCqQzL9X2f7nZvIRQTZGHiHMIQ6lGnBxwwTaN+N4oKBpcX
nyysSEW+C1Hk/EyXIc2rdLQrsqxjZhtEPdMNGQcXAAAAQQD0btOMDZFaO3DyWzIX
e7KATkMX3ISCajhE+kypXijoFmNOmJqLd956co6kDjFchCnUpMfWqWXP/pcj0/A5
y8vH
Private-MAC: 0b95165eb462c2f0857f1defa082eb5979d9ea69
Unfortunately this key is in the format of a PuTTY private key. PuTTY is a Windows
based GUI used for SSH and SFTP. Because this private key is designed for PuTTY
we can't use it natively on our Linux LAMPSec machine. We'll have to convert the
key to the Linux format before we can try using it. In order to format this key we
need to use the Windows based PuTTY Key Generation tool.
Fortunately the LAMPSec image has WINE, a Windows emulator installed on it. We
can use WINE to install and run Windows programs on our Linux based LAMPSec
machine. This is especially handy if we want to run security programs that are
only available on Windows.
We'll need to install PuTTY in order to convert the key to a Linux format so we can
use it. In order to install the program, we'll first need to download it using the
wget command like so:
$ wget http://the.earth.li/~sgtatham/putty/latest/x86/putty-0.60installer.exe

http://www.MadIrish.net
Once the program downloads run the installer using:
$ wine putty-0.60-installer.exe
Once installed you can use PuTTY. Let's use the PuTTY Key Generator to get the
Linux format for Andrew Chen's private key. Open up PuTTY from the Applications
menu → Wine → Programs → PuTTY → PuTTYgen. Once the program is open click
the 'Load' button and load up Andrew Chen's private key from the filesystem:

Next, click the 'Conversions' menu → Export OpenSSH key. Save the exported key
as achen_priv.key in /home/lampsec . Next we have to change the permissions on
the key:
$ chmod 0700 /home/lampsec/achen_priv.key
And finally we can try to log into the target site as achen:
© Copyright Justin C. Klein Keane
63

http://www.MadIrish.net
$ ssh -i /home/lampsec/achen_priv.key achen@192.168.229.134

http://www.MadIrish.net
You'll notice that no password is required! This key pair was generated with a
blank passphrase, and especially dangerous configuration from a security
perspective. Now you're logged in as Andrew Chen, one of the machine
administrators!

Let's see if Andrew Chen has any greater privileges than the last account we
compromised. Try the following command, which uses the sudo command to
carry out a command as root with the 'su', or switch user command, which when
issued without a username argument means “switch to the root account”:
$ sudo su
Notice your command prompt changed to a pound symbol, that indicates that
you're root! This is a result of a listing in the sudoers file that indicates that the
achen account doesn't need to enter a password to issue commands as root. This
is often utilized as a convenience, but obviously is a fairly big security risk. You
can verify that you're actually the root user with the 'whoami' command:
# whoami
You could also grab the root password by viewing Andrew Chen's .bash history file
using:
$ cat /home/achen/.bash_history
You'll see the root password listed in amongst the other commands. This sort of
thing is sadly fairly common when admins type fast and don't verify commands
they're issuing.

http://www.MadIrish.net

Other Unscripted Attack Vectors:
1. Enumerate the users on the system using the EXPN and VRFY commands
via telnetting to port 25
2. Get the MySQL root password from the file in the /conf directory
3. Log into MySQL from a local user account, view the users table, dump it and
try cracking the passwords using MD5 rainbow tables
(http://lampsecurity.org/node/17).
4. Uncover the user passwords via SQL injection using SQLmap (installed in
/usr/bin/sqlmap)
5. Upload the c99 shell to the target website
6. The older 2.6.15 Linux kernel may be vulnerable to any number or local root
exploits.

Source Exif Data:

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Author                          : Justin Klein Keane
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Create Date                     : 2012:11:21 09:50:09-05:00

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