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Packet Forgery

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In the past few days, coincidentally I’ve been thrown into situations where packet forgery has been required. So I thought it’ll be a great moment to enumerate some good options that network or security professionals have. The basis for most of these tools lies in libnet and libpcap which are some of the most wonderfully functional libraries out there.

  • Packetforge-ng – On the wireless side this utility allows you to capture wireless packets and create legitimate packets with a pre-determined payload that can then be replayed using tools such as aireplay-ng
  • Scapy – This is a python based tool and can be extended to write custom Python scripts to custom create packets. This library has great functions to form packets layer-by-layer and other functions such as fuzz() that allow fuzzing of packets out of the box. The greatest utility comes by the use of python language to create custom tools. Imagine creating custom thick clients just by using simple python scripts. The capabilities with this library are endless!
  • TCPReplay – Just convert your pcaps into traffic by replaying them. An excellent tool but be careful if you’ve sniffed some ARP packets. You could end up corrupting the ARP table entries (unless that’s exactly what your intentions is 😉
  • file2air – An excellent tool by Joshua Wright to replay packet contents.
  • Packit – A really easy to use and functional linux based packet injection tool.
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Setting up a Windows 7 Kernel Development Environment

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If you are writing some Ring0 (or privileged mode code), say something like device drivers in Windows you’d probably be better served with a separate development machine and a deployment machine. This helps you to write poor code and still not lose hair because your development machine blue screens! 🙂

My setup was using a Windows 8.1 development machine and a Hyper-V based Windows 7 machine for debugging. You will need to execute different tasks on the “guest” (Hyper-V based Windows 7 virtual machine) and some other tasks on the development machine.  I followed many of the things from the MSDN blog post here

On your guest machine you would want to setup a named pipe and setup debug settings. To do that this is what you need to do:

Setup a virtual com port in the Hyper-V Settings (File -> Settings) , this port will be used to communicate from the host machine to the guest to communicate the Kernel debugging commands.
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Now make sure that your target guest machine is configured to “listen” those commands.  Inside the guest VM, start a command shell (cmd.exe -> Run as Administrator).

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Configure the bcdedit commands so that the machine can now be debugged.  Right after the 2nd command, reboot your Virtual Machine.

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With the VM now configured to listen the debug commands via the COM1 port, and the debug mode on in the bootup settings, now start the WinDbg x64 on the host (using “Run as administrator”; you need administrative privileges for communication via Serial port).  In your kernel debugger on the host or the development machine (I’m assuming that these are both on the same physical hardware here).  Click on File -> Kernel Debug and you should see the following screen in the WinDbg window:

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Hit Ctrl+Break or Debug -> Break and you will see something like this:

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Just remember that when you break in the debugger, your guest in Hyper-V should become “unresponsive”.  The only thing is that it is not really unresponsive, its just being debugged.  Just to make sure, that you have the symbols package that is quite useful for debugging run the following command:

!process 0 0

If you see something like the following screen show up:

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The following error means that the symbols are not defined.  Symbols help the debugger give more information about the commands that you are going to execute in the debugger.

**** NT ACTIVE PROCESS DUMP ****
NT symbols are incorrect, please fix symbols

To fix this, use the following commands:

kd> .sympath SRV*c:\symcache*http://msdl.microsoft.com/download/symbols
kd> .symfix
kd> .symfix c:\symcache
kd> !sym noisy
kd> .reload /o

Then again try the command: !process 0 0 and see if you get a good response.  A good response looks like the following:

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With this you should be good to go! Happy debugging and writing cool Ring0 code.

 

 

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Projects…interjects!

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Come end of semester and the project deadlines start impending! The situation I am in is one of great thrill and rush! For the CS558L I’m doing this project in which I have to implement an automated worm fingerprinting mechanism but not only that combining it with ITrace I want to make Worm attacks and DDoS attacks a thing of past!
The scheme in plain English is to detect automatically if your network is being attacked by looking at the traffic and if so communicate this information to whoever you are forwarding this packet to! The ICMP messages that will be forwarded will carry information about who sent this traffic and other such information (including the signature of attack traffic). The receiver with all this information could gather the source of attacks. If all the routers followed this scheme then we will be able to reconstruct the entire path of the attack so the entry point of the attack could also be sealed….(hopefully leading to a Worm and DDoS attack-free internet)!!!
Really hopeful…aren’t I??? 😉
But again this technique has the same single flaw as the other techniques in that it needs co-operation between ISPs.
I am currently coding this scheme in the Linux Kernel 2.6.11.7 and this is my first tryst with linux kernel programming…let’s see what future holds for me!

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Lotus Notes and South Indian Names (error: Name too long)

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If you are a South Indian, have a long name, use lotus notes and want to send encrypted e-mail using Internet Certificates…you may just be out of luck! Why?
Lotus Notes 6 does not support importing of PKCS#12 (.pfx) certificates which have the CN (Customer name), OU (Organization unit), O (Organization), CA (Certificatio Authority) fields together more than 255 characters. Many of my south Indian friends in fact have names that are 40 characters themselves! Alongwith the O, OU and the CA taken together this could easily exceed more than 255 characters. On encountering such a situation, Lotus Notes also gives a friendly error message which my friends may not find quite amusing at that point “Name too long”. Once you encounter this error, you cannot proceed with the import. To work around this see if you can reduce the characters in OU and O fields because your e-mail ID has to match the one in Lotus.
I also found a useless response from IBM to get rid of this problem. Their response was pretty much “learn to deal with it! we won’t correct our stupid software”.
Justin’s written a pretty useful how to on importing S/MIME certificates into Lotus notes.

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GtkImage.c: line 572 java error on Kubuntu

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I installed KUbuntu “Breezy Badger” on my new Laptop (Dell Inspiron 700m) but none of my java based tools seemed to be working.

The errors I was getting were as follows:


** ERROR **: file ../../../src/libjava/jni/gtk-peer/gnu_java_awt_peer_gtk_GtkImage.c: line 572 (createRawData): assertion failed: (data_fid != 0)

aborting…


The trick is to use the Sun JVM and not the gcj (GNU Java Compiler). Apparently in Debian threads (on which KUbuntu is based) has this error in gcj-4.0. They promise that it will be fixed in version gcj-4.1 (which comes with gcc-4.1).

So follow these steps to get burp / paros etc working:
1. Goto java.sun.com and install the latest jvm for linux. Choose an appropriate location, mine was installed on /opt/jdk1.5.0_06/.
2. rm /usr/bin/java /usr/bin/javac /usr/bin/javah. (you remove symbolic links in /usr/bin which point the version of java to /etc/alternatives).
3. Create new symbolic links

# cd /usr/bin
# ln -s /opt/jdk1.5.0_06/bin/javac javac
# ln -s /opt/jdk1.5.0_06/bin/javah javah
# ln -s /opt/jdk1.5.0_06/bin/java java

Now you should be good to go!

-Rajat.

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The Next Hope

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This was my first hope conference (The Next HOPE Conference)despite being in New York City for more than half a decade. Always it seemed that work would send me out of town just before the con. However, this time around I had the good fortune of being in the city during the conference.
There were a few good talks some of which were not so technical but kindled the questions for privacy fanatics.
The talks I attended included Alessio Pennasilico’s talk about DDoS attack on Bakeca.it, Modern Crimeware and Tools talk by Alexander Heid, Steven Rambam’s talk on Privacy is Dead, Blaze Mouse Cheswick et. al’s talk which was abstract but awesome. I did attend a few more talks and it was fun. All in all a great conference.

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Nessus 4.2.0 : Web Interface

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Interestingly enough, I found last week that the new Nessus 4.2.0 works by default as a web interface. Gone are the days of using the NessusClient and connecting to TCP port 1241 and using it to connect to the nessusd. Connecting to local TCP port 8834 (https://localhost:8834) brings you to a web interface that you can use to connect to the new Nessus daemon. The nesssusd listener does not even listen on port 1241 by default.
I’ll shortly get used to it but I know the transition would be slow for me …. after it takes getting used to when you completely change the architecture after maintaining it for at least a good 7 years or so!