Every IT department faces the challenge of having to apply limited resources (headcount, technology, 3rd party assessments) against a plethora of potential security risks. Choosing wisely is often the difference between an effective security strategy and an ineffective one. With that in mind and a number of possible assessment approaches available, what benefits can be gained from an internal penetration test?
One thing you learn when you start a career in pentesting is:
Never assume anything.
In my experience hacks aren’t always elegant and elaborate. Sometimes something simple and effective is your avenue of penetration. Which brings us to today’s topic: directory bruteforcing.
Directory bruteforcing is a favorite of mine. I can’t tell you how many times a directory listing has broken open a pentest for me. Whether it be that all elusive web admin panel, or a directory listing containing a database with passwords, there’s almost always something hiding beneath that tidy little web server.
Before we start bashing away, and let’s be honest here that’s what we’re doing, we have to mention that this kind of enumeration can get you blacklisted. In fact if your scope doesn’t have you whitelisted for the engagement, we recommend you scan low and slow to get a feel for the targets response. It never hurts to have a backup IP (or a few) to scan from as well. Dealing with customer blacklisting is a pain.
Today, we’re showcasing python based Wfuzz by Edge-Security and Java based Dirbuster maintained by the OWASP project. Both are excellent directory and file brute forcing tools that come complete with lists of common (and sometimes not so common) directories or files. Both support recursion, multi-threading, and output to useful file formats. They are also great about inherent false positive detection and support proxies… excellent. We use Wfuzz on our *nix boxes and Dirbuster from Windows. We interchange lists frequently.
We hate to regurgitate verbatim but Wfuzz actually gives pretty good usage and feature documentation that can be seen on their website here.
“Wfuzz is a tool designed for bruteforcing Web Applications, it can be used for finding resources not linked (directories, servlets, scripts, etc), bruteforce GET and POST parameters for checking different kind of injections (SQL, XSS, LDAP,etc), bruteforce Forms parameters (User/Password), Fuzzing,etc.”
# wfuzz.py -c -z file -f wordlists/commons.txt --hc 404 --html http://www.mypentesttarget.com/FUZZ 2> results.html
This does a basic directory bruteforce against http://mypentesttarget.com/ throwing http GETs to the web server matching every line in the wordlists/commons.txt file. It strips out the 404 not found responses and sends the output to an HTML file for later usage.
Wfuzz is actually a far more robust tool allowing you to fuzz web parameters to identify SQL injection, XSS, and bruteforce usernames and passwords. The lists for these injection strings are included with wfuzz. We will showcase Wfuzz in more detail in a future write-up.
Dirbuster is very similar. It uses a pretty java GUI that allows you to specify number of threads and tune the amount of threads on the fly (which is actually really handy). It also supports pausing which is useful. Another great feature it offers is selective recursion. If Dirbuster finds a directory it will automagically queue it for recursive scanning, but if we want to skip that directory we can un-check the tick box next to it and change this on the fly. The GUI itself is pretty self explanatory and you can see basic usage in the video.
So what are we looking for?
Some of our favorites are:
- Jboss admin panels
- Backend web administration (think VPN, firewall, and website management logins)
- OWA servers
- Frontpage Config Files
- Citrix Portals
- Directories with databases
- Webcam portals
- Development/stage versions of software/sites
- Default PHP Config files
- 401 credential protected directories
- Directories containing documents we can mine for metadata
- Scripts we can fiddle with (list below)
For file types we wanna look for things like scripts we might be able to manipulate, log files, etc:
- .log, .phtml, .php, .php3, .php4, .php5, .inc, .asp, .aspx, .pl, .pm, .cgi, .lib, .jsp, .jspx, .jsw, .jsv, .jspf, .cfm, .cfml, .cfc, .dbm, .mdb
Even resources that give you 403 Forbidden responses are valuable in identifying the web server’s structure and the apps that run on it.
Earlier we said that we interchange lists. Here’s why. Below are the sizes, in words, of the lists supplied with Wfuzz and Dirbuster (as well as another favorite tool of ours Grendel Scan). The whopping difference here is Dirbuster’s lists are huge comparatively. The reason for this is that Dirbuster uses a large number of numeric only resource requests. Dirbuster also seems to really take the word “bruteforce” to heart requesting less than technical directory names. We’d love to say “Use X list over Y list” but we really can’t. We have garnered valuable findings from all these lists. If you aren’t under the blacklisting/shunning gun per-se you can cat these into a “masterdirs” file and then sort and uniq it. Just be aware that these lists are unordered on purpose to be optimized, if we have the time to complete the full list then it doesn’t matter, but if you have a short testing time frame it will.
|Wfuzz||common 947||medium 1660||big 3037|
|Dirbuster||small 81643||medium 207631||big 1185252|
|Grendel Scan||Small 100||Medium 300||Large 500||XL 819|
In our video we show the basic usage of both tools.
If you’re working with a scope that limits tools you can install, or you want to comb over some could-be false positives from a tools output you can do this by using a bash script (be easy on our Bash foo!)
# cat dircurl.sh
if [[ $# -ne 2 ]]; then echo "usage: $0 directorylist www.target.com" exit fi
for i in $(cat $1) do echo -ne "directory: " echo -ne $i echo -ne "t" echo -ne "count: " echo -ne `curl $2/$i 2> /dev/null | wc -l` echo done
This does a Curl request to each line in the supplied “directorylist” to the “target.com” and then does a wordcount (wc -l) on it. Look at the output, what is the most common response?
# bash dircurl.sh scanneroutput www.securityaegis.com
directory: sitemap count: 266 directory: archives count: 266 directory: wp-admin count: 7 directory: links count: 0 directory: login count: 266 directory: articles count: 266 directory: support count: 266 directory: keygen count: 266 directory: article count: 266 directory: help count: 266 directory: events count: 266 directory: archive count: 266 directory: register count: 266 directory: en count: 266 directory: forum count: 266 directory: wp-includes count: 7 directory: software count: 266 directory: downloads count: 266 directory: security count: 0 directory: category count: 266 directory: content count: 266 directory: main count: 266 directory: press count: 266 directory: media count: 266 directory: templates count: 266 directory: services count: 266 directory: icons count: 266 directory: wp-content count: 7 directory: resources count: 0 directory: info count: 0 directory: overnment count: 266 directory: corrections count: 266 directory: ajax count: 266 directory: icom_includes count: 266 directory: rules count: 266 directory: tr count: 266 directory: server count: 266 directory: mirrors count: 266 directory: government count: 266 directory: corrections count: 266
Looks like my error page (or in some cases my redirects) have about 266 newlines. Lets pipe that into grep -v 266, removing all lines containing 266:
# bash dircurl.sh scanneroutput www.securityaegis.com |grep -v 266
directory: wp-admin count: 7 directory: links count: 0 directory: wp-includes count: 7 directory: security count: 0 directory: wp-content count: 7 directory: resources count: 0 directory: info count: 0
This gives us a good place to start poking.
Thanks go to David, Paul, and Nate from the Redspin Team, and of course Mike Kelly (Laz3r) for his contributions on the video =)