c0d3 :: j0rg3

A collection of tips, tricks and snips. A proud Blosxom weblog. All code. No cruft.

Sat, 18 Feb 2017

The making of a Docker: Part II - Wickr: with bonus analysis

Recently, I read a rather excited attention-catching piece about how Wickr is the super-secure version of Slack. Attention caught in part because I feel like Wickr has been around for a while. I’d not seen anyone raving about its security in places where I normally interact with those who are highly informed about such subjects.

Good is that it seems the folk at Wickr did a fine job of making sure valuable data aren’t left behind.
The bad: closed-source, not subject to independent review; crazy marketin’-fancy-talk without a thorough description of how it does what is claimed.
Any time I’m looking at a product or service that boasts security, I sort of expect to see a threat model.

[ Update: At the time I was working on this project, the folk at Wickr were, evidently, opening their source. That’s spectacular news! Check it out on Github. ]

This began as an exercise to provide another piece of security-ish software in a Docker container. Anyone who has used a live distro (e.g., Kali, TAILS) with any regularity knows the ritual of installing favorite tools at each boot, data stores on removable media.

For me, there is tremendous appeal in reducing that to something like:
git clone https://georgeglarson/wickr
cd docker-wickr
./install.sh
wickr

Let’s dig in!

Having created a number of Docker containers my workflow is to queue up the base OS and go through the steps needed to get the software running while keeping careful notes. In this case, I had originally tried to install Wickr on a current copy of Kali. It was already known that Wickr, based off of Ubuntu 14.04, needed an older unicode library. So we begin with Ubuntu 14.04.

Grab a copy of Wickr and see what’s required:
dpkg -I wickr-me_2.6.0_amd64.deb

new debian package, version 2.0.
size 78890218 bytes: control archive=4813 bytes.
558 bytes, 14 lines control
558 bytes, 14 lines control64
10808 bytes, 140 lines md5sums
Package: wickr-me
Architecture: amd64
Section: net
Priority: optional
Version: 2.6.0-4
Replaces: wickr
Conflicts: wickr
Depends: libsqlcipher0, libuuid1, libicu52, libavutil52|libavutil54, libc6, libssl1.0.0, libx264-142, libglib2.0-0, libpulse0, libxrender1, libgl1-mesa-glx
Recommends: libnotify-bin, gstreamer-plugins0.10-good, gstreamer-plugins0.10-bad, gstreamer-plugins0.10-ugly
Maintainer: Wickr Inc.
Installed-Size: 200000
Description: Secure Internet Chat and Media Exchange agent
Wickr is a secure communications client

Okay. The CLI should do most of the work for us, giving a formatted list of dependencies.
dpkg -I wickr-me_2.6.0_amd64.deb | grep -E "^ Depends: | Recommends: " | sed -e "s/ Depends: //" -e "s/ Recommends: //" -e "s/,//g" -e "s/ / \\\ \n/g"

libsqlcipher0 \
libuuid1 \
libicu52 \
libavutil54 \
libc6 \
libssl1.0.0 \
libx264-142 \
libglib2.0-0 \
libpulse0 \
libxrender1 \
libgl1-mesa-glx
libnotify-bin \
gstreamer-plugins0.10-good \
gstreamer-plugins0.10-bad \
gstreamer-plugins0.10-ugly \

Attempting to get those with apt-get reports that it cannot find the gstreamer bits.

Let’s find:
apt-cache search gstreamer | grep -i plugin | grep -E "good|bad|ugly"

gstreamer0.10-plugins-good - GStreamer plugins from the "good" set
...
gstreamer0.10-plugins-bad - GStreamer plugins from the "bad" set
...
gstreamer0.10-plugins-ugly - GStreamer plugins from the "ugly" set

So, there’s the format we need to get the gstreamer dependencies. We know that we’ll also want SSH and wget. That should be enough for our Dockerfile.

We’ll pull down Wickr:
wget https://dls.wickr.com/Downloads/wickr-me_2.6.0_amd64.deb

Then install:
dpkg -i wickr-me_2.6.0_amd64.deb

Okay! We are, in theory, ready to run Wickr. We’re about to see we aren’t yet there — but these sorts of problems are pretty commonplace.
wickr-me

wickr-me: error while loading shared libraries: libxslt.so.1: cannot open shared object file: No such file or directory

Huh! We need libxslt. Let’s fix that: apt-get install libxslt1-dev

Now we can run it.
wickr-me

This application failed to start because it could not find or load the Qt platform plugin "xcb".

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, xcb.

Reinstalling the application may fix this problem.
Aborted (core dumped)

One more: apt-get install xcb

Okay. That really was the last one. Now we have a complete list of dependencies for our Dockerfile:
RUN apt-get update && apt-get install -y \
gstreamer0.10-plugins-good \
gstreamer0.10-plugins-bad \
gstreamer0.10-plugins-ugly \
libsqlcipher0 \
libuuid1 \
libicu52 \
libavutil52 \
libc6 \
libssl1.0.0 \
libx264-142 \
libglib2.0-0 \
libpulse0 \
libxrender1 \
libxslt1-dev \
libgl1-mesa-glx \
libnotify-bin \
ssh \
wget \
xcb \
&& apt-get clean \

We now have Wickr in a Docker container and, because we are the curious sort, need to peek into what’s happening.

A natural first step is to set Wireshark atop Wickr. At a glance, seems to be communicating with a single IP address (204.232.166.114) via HTTPS.

Unsurprsingly, the client communicates to the server whenever a message is sent. Further it appears to poll the same address periodically asking for new messages. We see that the address resolves to Rackspace in San Antonio, TX.

We can easily establish the link between this IP address, Rackspace and the application.

Well, that’s enough. Right?

Good!

Wait.

What?

We’re still a little curious.

Aren’t we?

I mean, what’s the big question here? What happens if there’s a man in the middle? Persons so eagerly connect to any free WIFI, it is clearly a plausible scenario. Well… One way to find out!

Here’s what we learned. Server-side, the application is written in PHP. The IP address is resolved by the URI ‘secex.info’.

When we send, it calls ‘postMessage.php’:

When we receive, ‘downloadMessage.php’:

And it calls ‘newMessageCheck.php’ to, y’know, check for new messages.

Other analyses have forensically examined artefacts left behind; there are published descriptions of the encryption methods used for the local database connection. We didn’t go into more aggressive efforts such as disassembly because we are too lazy for that jazz!

My opinion, we didn’t learn anything wildly unexpected. Overall, Wickr seems an okay solution for convenient encrypted messaging. That’s always the trade: convenience vs. security. Least we ended with a Docker container for the software!

Github | Docker


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Permalink: 20170218.making.a.docker.wickr

Fri, 17 Feb 2017

The making of a Docker: Part I - Bitmessage GUI with SSH X forwarding

Lately, I’ve been doing a lot of work from a laptop running Kali. Engaged in pursuit of a new job, I’m brushing up on some old tools and skills, exploring some bits that have changed.

My primary desktop rig is currently running Arch because I love the fine grain control and the aggressive releases. Over the years, I’ve Gentoo’d and Slacked, Crunchbanged, BSD’d, Solarised, et cet. And I’ve a fondness for all of them, especially the security-minded focus of OpenBSD. But, these days we’re usually on Arch or Kali. Initially, I went with Black Arch on the laptop but I felt the things and ways I was fixing things were too specific to my situation to be good material for posts.

Anyway, I wanted to get Bitmessage running, corresponding to another post I have in drafts. On Kali, it wasn’t going well so I put it on the Arch box and just ran it over the network. A reasonable solution if you’re in my house but also the sort of solution that will keep a hacker up at night.

If you’re lucky, there’s someone maintaining a package for the piece of software that you want to run. However, that’s often not the case.

If I correctly recall, to “fix” the problem with Bitmessage on Kali would’ve required the manual installation an older version of libraries that were already present. Those libraries should, in fact, be all ebony and ivory, living together in harmony. However, I just didn’t love the idea of that solution. I wanted to find an approach that would be useful on a broader scale.

Enter containerization/virtualization!

Wanting the lightest solution, I quickly went to Docker and realized something. I have not before built a Docker container for a GUI application. And Bitmessage’s CLI/daemon mode doesn’t provide the fluid UX that I wanted. Well, the easy way to get a GUI out of a Docker container is to forward DISPLAY as an evironment variable (i.e., docker run -e DISPLAY=$DISPLAY). Splendid!

Except that it doesn’t work on current Kali which is using QT4. There’s a when graphical apps are run as root and though it is fixed in QT5, we are using current Kali. And that means we are, by default, uid 0 and QT4.

I saw a bunch of workarounds that seemed to have spotty (at best) rates of success including seting QT’s graphics system to Native and giving Xorg over to root. They, mostly, seemed to be cargo cult solutions.

What made the most sense to my (generally questionable) mind was to use X forwarding. Since I had already been running Bitmessage over X forwarding from my Arch box, I knew it should work just the same.

To be completely truthful, the first pass I took at this was with Vagrant mostly because it’s SO easy. Bring up your Vagrant Box and then:
vagrant ssh -- -X
Viola!

Having proof of concept, I wanted a Docker container. The reason for this is practical. Vagrant, while completely awesome, has substantially more overhead than Docker by virtualizing the kernel. We don’t want a separate kernel running for each application. Therefore Docker is the better choice for this project.

Also, we want this whole thing to be seemless. We want to run the command bitmessage and it should fire up with minimal awkwardness and hopefully no extra steps. That is we do not want to run the Docker container then SSH into it and execute Bitmessage as individual steps. Even though that’s going to be how we begin.

The Bitmessage wiki accurately describes how to install the software so we’ll focus on the SSH setup. Though when we build the Dockerfile we will need to add SSH to the list from the wiki.

We’re going to want the container to start so that the SSH daemon is ready. Until then we can’t SSH (with X forwarding) into the container. Then we’ll want to use SSH to kick off the Bitmessage application, drawing the graphical interface using our host system’s X11.

We’re going to take advantage of Docker’s -v --volume option which allows us to specify a directory on our host system to be mounted inside our container. Using this feature, we’ll generate our SSH keys on the host and make them automatically available inside the container. We’ll tuck the keys inside the directory that Bitmessage uses for storing its configuration and data. That way Bitmessage’s configuration and stored messages can be persistent between runs — and all of your pieces are kept in a single place.

When we generate the container /etc/ssh/sshd_config is configured to allow root login without password only (i.e., using keys). So here’s how we’ll get this done:
mkdir -p ~/.config/PyBitmessage/keys #Ensure that our data directories exist
cd ~/.config/PyBitmessage/keys
ssh-keygen -b 4096 -P "" -C $"$(whoami)@$(hostname)-$(date -I)" -f docker-bitmessage-keys #Generate our SSH keys
ln -fs docker-bitmessage-keys.pub authorized_keys #for container to see pubkey

Build our container (sources available at Github and Docker) and we’ll make the script to handle Bitmessage to our preferences. #!/bin/bash
# filename: bitmessage
set -euxo pipefail

# open Docker container:
# port 8444 available, sharing local directories for SSH and Bitmessage data
# detatched, interactive, pseudo-tty (-dit)
# record container ID in $DID (Docker ID)
DID=$(docker run -p 8444:8444 -v ~/.config/PyBitmessage/:/root/.config/PyBitmessage -v ~/.config/PyBitmessage/keys/:/root/.ssh/ -dit j0rg3/bitmessage-gui bash)

# find IP address of new container, record in $DIP (Docker IP)
DIP=$(docker inspect $DID | grep IPAddress | cut -d '"' -f 4)

# pause for one second to allow container's SSHD to come online
sleep 1

# SSH into container and execute Bitmessage
ssh -oStrictHostKeyChecking=no -oUserKnownHostsFile=/dev/null -oIdentityFile=~/.config/PyBitmessage/keys/docker-bitmessage-keys -X $DIP ./PyBitmessage/src/bitmessagemain.py

# close container if Bitmessage is closed
docker kill $DID

Okay, let’s make it executable: chmod +x bitmessage

Put a link to it where it can be picked up system-wide: ln -fs ~/docker-bitmessage/bitmessage /usr/local/bin/bitmessage

There we have it! We now have a functional Bitmessage inside a Docker container. \o/

In a future post we’ll look at using eCryptfs to further protect our Bitmessage data stores.

  Project files: Github and Docker


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Permalink: 20170217.making.a.docker.bitmessage