Archive for May, 2013

Sometimes (don’t ask me why) when you are hacking some terminal server it happens that an administrator has disabled regedit.exe and reg.exe, but forgot about visual basic script (vbs). I know, I know everyone is all busy with powershell, but trust me sometimes vbs is the right script for the job. So I hacked together a quick script to view the registry which you can find on my github:

It should be pretty self-explanatory, but just in case here is some example usage:

C:\>cscript regview.vbs
Microsoft (R) Windows Script Host Version 5.8
Copyright (C) Microsoft Corporation. All rights reserved.

[] help

help - displays this help
cd  - change to that key
back - go to parent/previous key
ls - list current subkeys
lsv - list current key values
use - root key number to use
        3 - HKEY_USERS

[] use
key number: 1
[HKEY_CURRENT_USER\] cd software\vmware, inc.
[HKEY_CURRENT_USER\software\vmware, inc.] ls
VMware Tools
[HKEY_CURRENT_USER\software\vmware, inc.] cd vmware tools
[HKEY_CURRENT_USER\software\vmware, inc.\vmware tools] lsv
[HKEY_CURRENT_USER\software\vmware, inc.\vmware tools] ls
Hgfs Usability
[HKEY_CURRENT_USER\software\vmware, inc.\vmware tools] cd hgfs usability
[HKEY_CURRENT_USER\software\vmware, inc.\vmware tools\hgfs usability] lsv
Entry Name: mappedDriveLetter
        Data Type: String
        Value: z
[HKEY_CURRENT_USER\software\vmware, inc.\vmware tools\hgfs usability] back
[HKEY_CURRENT_USER\software\vmware, inc.\vmware tools] back
[HKEY_CURRENT_USER\software\vmware, inc.] exit

I know it lacks a search function, I’ll see if I get around to implement it any time soon. A script to change values is a whole other story though and something I don’t really need that often. If you encounter bugs, do fix them :)

Verifying Nmap scans

Posted: May 7, 2013 in general, security
Tags: , , , ,

So the other day while talking with Slurpgeit the following issue came up:

During a scan nmap reported 1000 ports filtered for the host, but wireshark told us otherwise a RST was received for a few ports but with a delay of ~18 seconds

Hmm that’s interesting, so that means that if wireshark hadn’t been monitored during the scan, the closed ports would have been missed or even worse what if open ports had been missed? The RTT to the host however were within normal ranges, also a simple ping worked fine without any delay whatsoever. Which brings us to an ancient saying about hacking:

Never trust your tools completely, always verify your results! Then verify them again and finally check that they are correct.

Since this is (assumed) something that doesn’t occur that often, you most probably want to automate the verification step. Unless you love looking at scrolling packets in your wireshark window. We can do it actively (real time sniffing) or passively (pcap) after the scans are done. I choose to implement the latter, the passive and after-the-facts verification. Reason being that all you most probably want is to check if something has gone wrong, if not just continue hacking your target. So let’s setup a lab environment to reproduce this issue and then let’s write a script for it using scapy.

I chose to just create two virtual machines within the same subnet, one being the attacker and one being the victim. To delay the traffic on the victim side I used netem since I didn’t manage to do it with iptables. I delayed one port with the following lines I found on the interwebs:

sudo tc qdisc add dev eth0 root handle 1: prio
sudo tc qdisc add dev eth0 parent 1:1 handle 2: netem delay 5s
sudo tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip sport 22 0xffff flowid 1:1

This will effectively delay all outgoing packets from port 22 with 5 seconds, which is more then enough to make nmap think it’s a filtered port. Fun fact: while playing with netem, if you apply the delay to all packets then nmap won’t even begin to scan the host, since according to it’s arp scan the host is down. Let’s fire up nmap and take a look at the output:

Finding sub domains using DNS is common practice, for example fierce does a pretty nice job. Additionally fierce presents a nice overview of the possible ranges that belong to your target. For some odd reason I also like to find sub domains using search engines, even though this will deliver results that are far from exhaustive. In the past I wrote a perl script to do this, but since I’m becoming a fan of python I decided to rewrite it in python. For example using python-requests and beautifulsoup it only takes like ~10 lines to scrape the sub domains from a search engine page:

def getgoogleresults(maindomain,searchparams):
    regexword = r'(http://|https://){0,1}(.*)' + maindomain.replace('.','\.')
        content = requests.get(googlesearchengine,params=searchparams).content
        print >> sys.stderr, 'Skipping this search engine'
    soup = BeautifulSoup(content)
    links = soup.find_all('cite')
    extract = re.compile(regexword)
    for i in links:
        match = extract.match(i.text)
        if match:
            res = + maindomain
            if res not in subdomains:

This script doesn’t parse all the result pages from the search engines. Actually it only parses the first page. This is because I wanted to keep it simple for the moment being and it helps to not get blocked that quickly. To compensate for the lack of crawling the results, the script uses multiple search engines and negates the results from one engine onto another.  For example it performs queries like:

site:somedomain.tld -site:subdomain1.somedomain.tld

As said it compensates somewhat for the lack of crawling the results pages but it will surely fail to find all sub domains indexed on the search engines. This is how it looks like:

Which is exactly the moment when I realised I’d also would like the ip addresses that belong to the found domains. I wrote a separate script for that which uses the adns python bindings. This is how it looks like: |

If you wonder why I wrote a new script that uses adns:

real 0m46.962s
user 0m0.904s
sys 0m0.180s

That’s the time it took to resolve 2280 hosts including a couple of 3 second delays to not hog the DNS server. Also for tasks like this (brute forcing sub domains with DNS) bash is your friend:

for i in `cat hosts.txt`;do echo $i”” >> hacktalkdomains.txt;done hacktalkdomains.txt | grep -vi resverror

I copied the two scripts to my /usr/local/bin directory to be able to use them from anywhere on the cli. You can find them over here: