c0d3 :: j0rg3

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

Sat, 04 Mar 2017

Official(ish) deep dark onion code::j0rg3 mirror

Recently I decided that I wanted my blog to be available inside of the Deep, Dark Onion (Tor).

First time around, I set up a proxy that I modified to access only the clear web version of the blog and to avail that inside Tor as a ‘hidden service’.

My blog is hosted on equipment provided by the kind folk at insomnia247.nl and I found that, within a week or so, the address of my proxy was blocked. It’s safe for us to assume that it was simply because of the outrageous popularity it received inside Tor.

By “safe for us to assume” I mean that it is highly probable that no significant harm would come from making that assumption. It would not be a correct assumption, though.

What’s more true is that within Tor things are pretty durn anonymous. Your logs will show Tor traffic coming from 127.0.0.1 only. This is a great situation for parties that would like to scan sites repeatedly looking for vulnerabilities — because you can’t block them. They can scan your site over and over and over. And the more features you have (e.g., comments, searches, any form of user input), the more attack vectors are plausible.

So why not scan endlessly? They do. Every minute of every hour.

Since insomnia247 is a provider of free shells, it is incredibly reasonable that they don’t want to take the hit for that volume of traffic. They’re providing this service to untold numbers of other users, blogs and projects.

For that reason, I decided to set up a dedicated mirror.

Works like this: my blog lives here. I have a machine at home which uses rsync to make a local copy of this blog. Immediately thereafter it rsyncs any newly gotten data up to the mirror in onionland.

After consideration, I realized that this was also a better choice just in case there is something exploitable in my blog. Instead of even risking the possibility that an attacker could get access to insomnia247, they can only get to my completely disposable VPS which has hardly anything on it except this blog and a few scripts to which I’ve already opened the source code.

I’ve not finished combing through but I’ve taken efforts to ensure it doesn’t link back to clear web. To be clear, there’s nothing inherently wrong with that. Tor users will only appear as the IP address of their exit node and should still remain anonymous. To me, it’s just onion etiquette. You let the end-user decide when they want to step outside.

To that end, the Tor mirror does not have the buttons to share to Facebook, Twitter, LinkedIn, Google Plus.

That being said, if you’re a lurker of those Internet back-alleys then you can find the mirror at: http://aacnshdurq6ihmcs.onion

Happy hacking, friends!


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Permalink: 20170304.deep.dark.onion

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

Mon, 02 Jan 2017

Securing a new server

Happy new year! New year means new servers, right?

That provides its own set of interesting circumstances!

The server we’re investigating in this scenario was chosen for being a dedicated box in a country that has quite tight privacy laws. And it was a great deal offered on LEB.

So herein is the fascinating bit. The rig took a few days for the provider to set up and, upon completion, the password for SSHing into the root account was emailed out. (o_0)

In very security-minded considerations, that means that there was a window of opportunity for bad guys to work on guessing the password before its owner even tuned in. That window remains open until the server is better secured. Luckily, there was a nice interface for reinstalling the OS permitting its purchaser to select a password.

My preferred approach was to script the basic lock-down so that we can reinstall the base OS and immediately start closing gaps.


In order:

  • Set up SSH keys (scripted)
  • Disable password usage for root (scripted)
  • Install and configure IPset (scripted. details in next post)
  • Install and configure fail2ban
  • Install and configure PortSentry

  • In this post, we’re focused on the first two steps.


    The tasks to be handled are:

  • Generate keys
  • Configure local SSH to use key
  • Transmit key to target server
  • Disable usage of password for ‘root’ account

  • We’ll use ssh-keygen to generate a key — and stick with RSA for ease. If you’d prefer ECC then you’re probably reading the wrong blog but feel encouraged to contact me privately.

    The code:

    #!/bin/bash
    #configure variables
    remote_host="myserver.com"
    remote_user="j0rg3"
    remote_pass="thisisaratheraquitecomplicatedpasswordbatterystaple" # https://xkcd.com/936/
    local_user=`whoami`
    local_host=`hostname`
    local_date=`date -I`
    local_filename=~/.ssh/id_rsa@$remote_host

    #generate key without passphrase
    ssh-keygen -b 4096 -P "" -C $local_user@local_host-$local_date -f $local_filename

    #add reference to generated key to local configuration
    printf '%s\n' "Host $remote_host" "IdentityFile $local_filename" >> ~/.ssh/config

    #copy key to remote host
    sshpass -p $remote_pass ssh-copy-id $remote_user@$remote_host

    #disable password for root on remote
    ssh $remote_user@$remote_host "cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak && sed -i '0,/RE/s/PermitRootLogin yes/PermitRootLogin no/' /etc/ssh/sshd_config"

    We just run this script soon as the OS is reinstalled and we’re substantially safer. As a Deb8 install, quickly pulling down fail2ban and PortSentry makes things quite a lot tighter.

    In another post, we’ll visit the 2017 version of making a DIY script to batten the hatches using a variety of publicly provided blocklists.

    Download here:
        ssh_quick_fix.sh


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    Permalink: 20170102.securing.a.new.server