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The Detection of Promiscuous Network Cards February 9, 2018

Back in 2010 I finally finished University. For me, University for some reason wasn’t a choice, but a last resort. After struggling to get through my GCSEs with a head cold, and then fumbling through college (or sixth form as it seems to be called now in the UK) I had a choice to make. I could either try to find a job, or go onto Job Seekers Allowance (JSA).

I got into Teesside University through the clearing process, and just as I had struggled to get into college by having to re-sit my GCSE Maths, I got onto the ladder of University with a Higher National Diploma (HND) in Computing, Software Development. When I finally got around to finishing it, some 4 years later than intended, I was determined to get a degree, only to be told by the University lecturers that they felt I wasn’t a capable C Programmer, even though the undergraduate degree module and course was aimed at people with no prior knowledge.

After Teesside University lost and re-found my grades, I got into another University where I rode the programming and networking train through my Bachelor of Science degree through to Masters of Science.

Sometimes you shouldn’t listen to lecturers, and often the path isn’t easy.

So in 2010 I was meant to publish my dissertation in an article in a journal. If I’m honest with myself, I had anxiety issues, and sometimes I still do. I never published the article and I was pretty burnt out from University. Suffering mostly from what I now recognise as ‘imposter syndrome’. My work was also downgraded because I didn’t discuss the mathematics behind my findings so well, you can perhaps see why I struggled and I blamed myself for that.

Here I’ve been looking through my old hard drives and files, and lo’ and behold I find my 2010 MSc Dissertation, “The Detection of Promiscuous Network Cards”.

You’ll likely have used similar techniques to this in tools such as Nessus, however perhaps not to this extent. There are some good findings in this report, and some details omitted, such as the discovery that the behaviour of promiscuous mode network adapters are changed if you’re running a VMWare Virtual Machine – I still have the stats and evidence of that one somewhere. I was advised not to release that information into my dissertation at the time, VMWare wouldn’t have been happy, apparently.

If you’re interested in some coding (it’s in there too), Z-Statistics of network packets, and also comparisons between Microsoft Windows, Linux and OSX and identifying them on an enterprise network, then you’re in for a treat.

Please do enjoy, finally ‘published’, my report on the Detection of Promiscuous Network Cards.

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Running Debian on the Atmel SAMA5D3 Board April 24, 2014

So when I wanted to build a version of Linux for the SAMA5D3 board that wasn’t Yocto or a demonstration image, then I started to struggle to find solutions.

Then I happened upon Robert Nelson’s guide on EEWiki. However, I found that it was not as straightforward as I had hoped. A few instructions were confusing and out of order with one another.

Here I present the steps I took to have Debian working on the SAMA5D3, some are the same, others are importantly different. I also have a .IMG of the SD Card I created available.

I set this up using a laptop with Debian Linux installed; I imagine it doesn’t matter which version of Linux you have; you could probably use Cygwin on windows.

You will need:

  • An SD card (I tend to work with at least a Class 6, 8gByte)
  • An Atmel SAMA5D3 board
  • A computer with Linux (unless you’re able to translate the steps to Windows, feel free) with an internet connection
  • A Serial debug cable
  • Open up a terminal, create a directory to work in and run the following commands to grab Linaro, the ARM cross compiler:

    wget -c https://releases.linaro.org/14.03/components/toolchain/binaries/gcc-linaro-arm-linux-gnueabihf-4.8-2014.03_linux.tar.xz
    tar xf gcc-linaro-arm-linux-gnueabihf-4.8-2014.03_linux.tar.xz
    export CC=`pwd`/gcc-linaro-arm-linux-gnueabihf-4.8-2014.03_linux/bin/arm-linux-gnueabihf-

    Then test the version of gcc:

    ${CC}gcc --version

    Which should output something like this:

    arm-linux-gnueabihf-gcc (crosstool-NG linaro-1.13.1-4.8-2014.03 - Linaro GCC 2014.03) 4.8.3 20140303 (prerelease)
    Copyright (C) 2013 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions. There is NO

    Now we need to grab U-Boot and patch it for the SAMA5D3, you will need to have GIT installed on your distribution of Linux:

    git clone git://git.denx.de/u-boot.git
    cd u-boot/
    git checkout v2014.04 -b tmp
    wget -c https://raw.github.com/eewiki/u-boot-patches/master/v2014.04/0001-sama5d3_xplained-uEnv.txt-bootz-n-fixes.patch
    patch -p1 < 0001-sama5d3_xplained-uEnv.txt-bootz-n-fixes.patch make ARCH=arm CROSS_COMPILE=${CC} distclean make ARCH=arm CROSS_COMPILE=${CC} sama5d3_xplained_mmc_config make ARCH=arm CROSS_COMPILE=${CC}

    Now time to build a kernel for the board!

    git clone https://github.com/RobertCNelson/armv7_devel.git
    cd armv7_devel/

    As of the time of writing the current mainline kernel was v3.14:

    git checkout origin/v3.14.x-sama5-armv7 -b tmp

    After the kernel has compiled, you’re presented with a menu config screen where you can include or build additional modules. For example, you can incorporate GSPCA webcam support.

    Now, we want to acquire the root system files for Debian, which are handily available:

    wget -c https://rcn-ee.net/deb/minfs/wheezy/debian-7.4-minimal-armhf-2014-04-01.tar.xz
    tar x -f debian-7.4-minimal-armhf-2014-04-01.tar.xz

    Then insert your SDCard, either using a USB SDCard reader or one on your computer if you have one. I had to use a USB SDCard reader. In Linux we can type “dmesg” at a terminal to give us the /dev/ information for the device we’ve plugged in (for example mine’s /dev/sdb), in the following examples, we use mmcblk0, so just replace it for your relevant device id.

    In the following steps we will erase the SDCard and set it up with the relevant partitions:

    export DISK=/dev/mmcblk0
    sudo dd if=/dev/zero of=${DISK} bs=1M count=16

    sudo sfdisk --in-order --Linux --unit M ${DISK} < <-__EOF__ 1,48,0xE,* ,,,- __EOF__
    If the linux system you're using identifies the device as something similar to mmcblk0 then to format and mount, execute:

    sudo mkfs.vfat -F 16 ${DISK}p1 -n boot
    sudo mkfs.ext4 ${DISK}p2 -L rootfs

    sudo mkdir -p /media/boot/
    sudo mkdir -p /media/rootfs/

    sudo mount ${DISK}p1 /media/boot/
    sudo mount ${DISK}p2 /media/rootfs/

    Else if the device identifies itself as something similar to sdb then to format and mount, execute:

    sudo mkfs.vfat -F 16 ${DISK}1 -n boot
    sudo mkfs.ext4 ${DISK}2 -L rootfs

    sudo mkdir -p /media/boot/
    sudo mkdir -p /media/rootfs/

    sudo mount ${DISK}1 /media/boot/
    sudo mount ${DISK}2 /media/rootfs/

    Note: You may not need to mount the partitions as new(ish/er) distributions tend to automatically mount partitions upon detection/insertion/creation.

    Create a text file using your editor of choice (for the record I prefer vi …) called uEnv.txt and put in it the following, the sama board uses the ‘mmc’ naming convention:

    optargs=quiet init=/lib/systemd/systemd
    mmcroot=/dev/mmcblk0p2 ro
    mmcrootfstype=ext4 rootwait fixrtc

    Now we’ll extract and copy across all of the necessary files, the locations should all be relative to the initial directory we’ve been working in and you created, they should all be executed as root/sudo:

    sudo cp -v ./u-boot/spl/u-boot-spl.bin /media/boot/BOOT.BIN
    sudo cp -v ./u-boot/u-boot.img /media/boot/

    sudo cp -v ./uEnv.txt /media/boot/

    sudo tar -xvp --same-owner --numeric-owner -f ./debian-0.4-minimal-armhf-2014-04-01/armhf-rootfs-debian-wheezy.tar -C /media/rootfs

    sudo cp -v ./armv7_devel/deploy/3.14.0-sama5-armv7-r9.zImage /media/boot/zImage

    sudo mkdir -p /media/boot/dtbs/
    sudo tar xvo -f 3.14.0-sama5-armv7-r9-dtbs.tar.gz -C /media/boot/dtbs

    sudo tar xv -f 3.14.0-sama5-armv7-r9-modules.tar.gz -C /media/rootfs

    And to setup the partition mounting (if you don’t like vi, replace with nano, emacs or whatever your preferred editor is):

    sudo vi /media/rootfs/etc/fstab

    Insert into it (in vi, press ‘i’ on your keyboard, then type it in, or copy/paste it into your terminal window):

    /dev/mmcblk0p2 / auto errors=remount-ro 0 1
    /dev/mmcblk0p1 /boot/uboot auto defaults 0 2

    Close and save the file (in vi, press ESC then type in :x and hit enter, which saves and quits).

    Then setup the network interfaces:

    sudo vi /media/rootfs/etc/network/interfaces

    With the following at the end of the file (you can use your cursor keys to navigate vi until you get to where you want to insert):

    allow-hotplug eth0
    iface eth0 inet dhcp

    allow-hotplug eth1
    iface eth1 inet dhcp

    And setup our serial line:

    sudo vi /media/rootfs/etc/inittab

    With the following at the end of the file:

    T0:23:respawn:/sbin/getty -L ttyS0 115200 vt102

    Now we want to unmount our SD Card, so close down any windows/open files that’re on the card and run the following from a terminal:

    sudo umount /media/boot
    sudo umount /media/rootfs

    Our SD Card should be setup! The only thing to do now, is remove the jumper at JP5 on the SAMA5D3 to ensure it’ll boot from the SD Card, connect a serial cable to the debug header J23 so we can see what it’s doing, with the settings in minicom/Putty/your terminal editor of choice:

    Baud: 115200
    Data Bits: 8
    Stop Bits: 1
    Parity: None
    Flow Control: None

    Then connect the USB cable to power the board, then press the reset button for good measure and watch it boot up!

    Login details:

    User: root
    Pass: root

    User: debian
    Pass: temppwd

    When I created this image from scratch initially I encountered a number of problems. The main part is that the SD Card needs to be setup as root, with the files copied over as root. This is because of the permission level required to read the SD Card when the SAMA5D3 board loads up.

    The other problem I encountered was the settings for uEnv were confusing me on the eewiki guide.

    Something that might trip up anyone following this guide word for word in future is if the kernel version increases, this will need to be altered in the filenames in the guide above. Failing that, the SD Card img I have prepared should help:

    Debian-SAMA5D3-140409.zip (543mB)
    Debian-SAMA5D3-140409.md5 (211b)

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