Quick & Dirty PXE Boot

sudo apt-get install tftpd-hpa
$ cat /etc/default/tftpd-hpa
# /etc/default/tftpd-hpa

TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/var/lib/tftpboot"
TFTP_ADDRESS="[::]:69"
TFTP_OPTIONS="--secure"

sudo -i
cd /var/lib/tftpboot
wget http://archive.ubuntu.com/ubuntu/dists/trusty-updates/main/installer-amd64/current/images/netboot/netboot.tar.gz
tar xvzf netboot.tar.gz

Notes on HP 1020 printer setup with Google Cloud print.

Notes on HP 1020 printer setup with Google Cloud print. This is a very scattered post and long TODO item.

Installed the printer with this guide.
http://tkjacobsen.wordpress.com/2008/12/15/hp-laserjet-1020-on-fedora-10/

https://support.google.com/a/answer/2906017?hl=en
python generate_cloudprint_config.py

Confused a bit about the instructions so I added a symlink called "Service State" that points to the config.
ls /etc/google-cloud-print/ -l
total 4
-rw-r--r-- 1 root root 736 Jan 25 19:22 dj-server.conf
lrwxrwxrwx 1 root root  14 Jan 25 19:24 Service State -> dj-server.conf

I've been abusing /etc/rc.d/rc.local for a lot of my startup scripts.  This server setup has been a more get it working kind of approach.  Note the --user-data-dir flag reference the directory I created with the config not the exact config file.

vi /etc/rc.d/rc.local
su - djhedges -c '/usr/bin/screen -dmt cloud-print -S cloud-print /opt/google/chrome/chrome --type=service --enable-cloud-print-proxy --no-service-autorun --noerrdialogs --user-data-dir=/etc/google-cloud-print/  --enable-logging=stderr --v=1 --enable-logging --v=1'

From there I can share the printer from some sort of printer setting I found linked with my Google account.

Cisco WPA

My wireless on my router quit working for a while.  I think it was power cycled and something from the config wasn't written to flash.  I spent hours trying to reconfigure it, how hard could setting up WPA be?  The examples I found online showed the following and even my old configs had something similar.

interface Dot11Radio0
 no ip address
 !
 encryption vlan 2 mode ciphers tkip
 !
 ssid dj-ap
    vlan 2
    max-associations 1
    authentication open mac-address 00:00:00:00:00:00
    authentication key-management wpa
    guest-mode
    wpa-psk ascii 7 password_hash

This for some reason was the missing piece.  If I recall correctly as soon as I added the world-mode line everything started working.  It goes under the Dot11 interface but I always overlooked it because of indentation from the ssid bit above.

 world-mode dot11d country US both
 speed basic-1.0 basic-2.0 basic-5.5 6.0 9.0 basic-11.0 12.0 18.0 24.0 36.0 48.0
 station-role root

Separate network SSID instead of bridging it with the ethernet ports like I used to.   I plan to add a guest SSID and prevent their traffic from talking to my network.

interface Dot11Radio0.2
 encapsulation dot1Q 2
 ip address 172.16.2.1 255.255.255.0
 ip nat inside
 ip virtual-reassembly

Hiding Data in Ping Packets

Fun little idea I started playing around with. I wanted to send data using ping packets ICMP packets are seemed as harmless and it would be hard to distinguish legitimate pings and pings containing encrypted data.

• Populate a Protocol Buffer
• Serialize the Protocol Buffer to a String
• Pad the data if necessary and encrypt with Blowfish
• Create a ICMP packet with a random salt + the encrypted data.
• Sniff for ICMP packets and reverse all the above steps.

Inspired a bit by Loki.

http://www.phrack.org/issues.html?id=6&issue=49

Some of things I learned and want to do if I find the time.

• I learned that block ciphers need to pad data.
• Ping replies contain the same data as the request. It makes sense now but I was initially planning to change the data in the reply.
• I'm concerned I'm still not doing things properly. Example theres nothing to stop anybody from replaying a packet. Maybe I could add a timestamp to the protocol buffer and ignore packets that are a minute old or something. I'd liked to figure out how fwknop works.

Source

https://github.com/djhedges/scripts/blob/master/via/via.py

Cracking WPA keys with GPUs

I first read the article and I thought wow thats a lot faster. Then I started doing some math and realized it's still not practical.

http://arstechnica.com/security/news/2008/10/company-puts-nvida-gpus-to-work-cracking-wireless-security.ars

They benchmarked a 8800GTX at 2,500 guesses per second. It's distributed software up to 256 GPUS.
2,500 x 256 = 640,000 a second

How many possibilities can a WPA pass phrase be? (I think my math is right)
Upper & Lower case possible characters. 26*2 = 52
Possible special characters like $@!%, at least what I counted on my laptop. 32
52+32 = 84
63 possible characters in a WPA psk.
A!/(A-N)! = 84!/(84-63)! = 6.486942682e+106
I took that really big number and divided it by (640,000 * 60 * 60 * 24 * 365)
3214056297949842159116168158203114584942029386406415805023892166920391523704839025459200000000 years to find all the possibilities
http://wiki.answers.com/Q/What_is_the_equation_to_determine_number_of_possible_lock_combinations

I did the same math and found how long it would take to generate all the possible combinations. It's amazing how much stronger a pass phrase becomes by adding another character.
1-5 characters would take 96 minutes
1-6 characters would take 5.2 days
1-7 characters would take 412 days
1-8 character would take 87 years

Site I've always used to generate keys.
http://www.kurtm.net/wpa-pskgen/

All in all I guess as long as you have a decent password your ok.

Ubuntu Install CD Buffer I/O Errors on Device sr0

sr0 is actually the cd-rom device and it turns out the disc was bad. I didn't check the md5 when I burned it and was just tossing it around my desk so I might have scratched it.

PC hanging @ Verifying DMI Pool Data

Changing the boot from hard drive to cd-rom fixed it. I think it was because I stopped a Ubuntu install while I was setting up an encrypted partition.