Felix Rusu from lowpowerlab.com has created an amazing library for the Arduino/ATMega platform to use cheap RFM69 wireless modules for wireless transmissions between nodes. For a list of all the features, see his readme: https://github.com/LowPowerLab/RFM69. His Moteino platform and library are perfect for roll-your-own home automation systems, which is just what I am doing!
However, in my mind the library was lacking one critical piece – being able to prevent wireless replay attacks. Using Felix’s library, RFM69 transmissions can be encrypted in hardware, but the receiving node had no way of verifying that the incoming transmission was from a legitimate node and should be processed. If an attacker captured a sensitive packet as it flew through the air, such as one to open your garage door, they could replay it at a time of their choosing and trick your home automation system into opening the door.
TomWS on the lowpowerlab forum and I did some brain storming and he proposed modifications to the base RFM69 library to virtualize some functions, allowing them to be overloaded to create ‘extensions’. Using his modification, I wrote a transmission session key extension.
More after the break…
Continue reading Session Key support for Arduino with RFM69 wireless module →
There are numerous python libraries out there for the 16 port MCP23017 GPIO expander chip that works with the Raspberry Pi, so why yet another one? None of the ones I could find actually implement interrupts via the chip Polling is not ideal for my home monitoring setup. I was already monitoring via interrupts and the onboard GPIO pins using the awesome RPIO module and wanted to continue using interrupts with the expansion chip. So I built my own module, leveraging Adafruit’s I2C library for the nitty gritty backend interface.
- Simple digital input and output via all pins
- Input interrupts
- Interrupt port mirroring is configurable – either INTA and INTB can trigger independently for their respective GPIO port banks, or both INTA and INTB can trigger at the same time regardless of what GPIO pin causes the interrupt
- Configurable interrupt polarity – INT could pull the pin high or push it low
- Each GPIO pin can be configured for interrupts independently to either compare against the previous value or against a default pin value
- A utility method cleanupInterrupts that can be called periodically to clear the interrupt if it somehow gets stuck on
You can find the library on my BitBucket.
Stick around after the break for a breakdown of how to use it.
Continue reading MCP23017 GPIO Expander python 3 Library – With Interrupts! →
WARNING: if you do this wrong or don’t understand the concepts, you risk losing your data. Be sure you know your way around linux and what you’re getting into before attempting!
To me, encryption of data at rest is just as important as encryption of data in transit. You never know if someone is going to break into your house and steal your computer. With so much personal information like financial data and pictures stored on the computer, it could be a major mess to recover from theft of your computer. (Of course, always keep an off-site backup for the really important stuff!)
I chose to migrate from the Solaris based OpenIndiana to Ubuntu. I had grown to love ZFS on OpenIndiana and didn’t want to lose its features. Luckily ZFS on Linux is now ready for prime-time! Unfortunately, ZFS on Linux is a few versions behind the official Oracle ZFS just like all other third part implementations of ZFS and does not support native encryption through the filesystem.
Continue reading ZFS on Linux with LUKS encrypted disks →
SSL’s primary function on the Internet is to facilitate encryption and trust that allows a web browser to validate the authenticity of a web site. However, SSL works the other way around too – client SSL certificates can be used to authenticate a client to the web server. Think SSH public/private key pairs, if that is familiar to you. In this blog post I will outline the steps to create a certificate authority certificate, sign a server certificate and install it in Apache, and create a client cert in a format used by web browsers.
Continue reading SSL Client Authentication Step By Step →
There are a variety of extremely cheep USB wifi dongles available on ebay that work wonderfully… once you get them working. I picked one up for $4 for my Raspberry Pi and had trouble getting it to work under Raspbian. Here’s what you need to do for the current Ralink USB adapters out there.
Continue reading Get the Ralink 28xx USB Dongle Running on Raspbian 7 (Raspberry Pi) →
At last! The third and final part of our git series has arrived. The first two parts of the series get you started with git and interacting with your project. They are available here:
Git part 1: Intro to git, setup a git server on CentOS and create a new project
Git part 2: Interacting with your project
In the final chapter of this series, we’ll explore a few of the more advanced features.
Continue reading Git part 3: Branching, merging and resolving conflicts →
Sometimes in a coding project there will be files or directories that should not be included in a git repository. Common examples are temporary folders, log files, or files containing passwords/keys that should be regenerated by each installation of the software and kept secret. Fortunately, it is very easy to ignore these files when committing the git project.
Continue reading Git Quick Tip – Ignoring a file →
I use VMware’s ESXi in my home lab environment. If you’re a technologist that is always messing with operating systems and applications, it is really the only way to go. But along with running any systems comes maintaining good backups!
There are numerous VMware backup products on the market. The problem is they all cost money. For me and other people who just play with this stuff for fun, that is not desirable. At all.
Continue reading Automated ESXi Backup Without Dependencies! →
EDIT: This post was originally written for Kali 1.0 in 2013. It was not tested on any later version.
I started this post with Backtrack, but since Kali Linux came out yesterday, I figured I would update the instructions to use the latest and greatest!
Thug is a low-interaction honeyclient put out by The Honeynet Project. The purpose of a honeyclient is to emulate a web browser when viewing malicious websites without actually visiting the page in a vulnerable browser. It can then follow redirects, pull down malware, and emulate browser plugins to pull down any of the malicious code trying to be served up to victims. You can read more about Thug here and here.
Continue reading Install Thug on Kali Linux →
Backing up Gmail has been on my list of things to do ever since Google accidentally deleted a whole bunch of accounts. My inbox containts a lot of important information and if it were to be lost, it would be a major pain. I finally got around to backing it all up.
Continue reading Script Gmail backup with getmail on linux →