c0d3 :: j0rg3

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

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

    Mon, 17 Feb 2014

    Installing INN’s Project Largo in a Docker containter

    Prereqruisites: Docker, Git, SSHFS.

    Today we’re going to look at using Docker to create a WordPress installation with the Project Largo parent theme and a child theme stub for us to play with.

    Hart Hoover has established an image for getting a WordPress installation up and running using Docker. For whatever reason, it didn’t work for me out-of-box but we’re going to use his work to get started.

    Let’s make a place to work and move into that directory:
    cd ~
    mkdir project.largo.wordpress.docker
    cd project.largo.wordpress.docker

    We’ll clone the Docker/Wordpress project. For me, it couldn’t untar the latest WordPress. So we’ll download it outside the container, untar it and modify the Dockerfile to simply pull in a copy:
    git clone https://github.com/hhoover/docker-wordpress.git
    cd docker-wordpress/
    ME=$(whoami)
    wget http://wordpress.org/latest.tar.gz
    tar xvf latest.tar.gz
    sed -i 's/ADD http:\/\/wordpress.org\/latest.tar.gz \/wordpress.tar.gz/ADD \.\/wordpress \/wordpress/' Dockerfile
    sed -i '/RUN tar xvzf \/wordpress\.tar\.gz/d' Dockerfile

    Then, build the project which may take some time.
    sudo docker build -t $ME/wordpress .

    If you’ve not the images ready for Docker, the process should begin with something like:
    Step 0 : FROM boxcar/raring
    Pulling repository boxcar/raring
    32737f8072d0: Downloading [> ] 2.228 MB/149.7 MB 12m29s

    And end something like:
    Step 20 : CMD ["/bin/bash", "/start.sh"]
    ---> Running in db53e215e2fc
    ---> 3f3f6489c700
    Successfully built 3f3f6489c700

    Once the project is built, we will start it and forward ports from the container to the host system, so that the Docker container’s site can be accessed through port 8000 of the host system. So, if you want to see it from the computer that you’ve installed it on, you could go to ‘HTTP://127.0.0.1:8000’. Alternatively, if your host system is already running a webserver, we could use SSHFS to mount the container’s files within the web-space of the host system.

    In this example, however, we’ll just forward the ports and mount the project locally (using SSHFS) so we can easily edit the files perhaps using a graphical IDE such as NetBeans or Eclipse.

    Okay, time to start our Docker image and find its IP address (so we can mount its files):
    DID=$(docker run -p 8000:80 -d $ME/wordpress)
    DIP=$(docker inspect $DID | grep IPAddress | cut -d '"' -f 4)
    docker logs $DID| grep 'ssh user password:' --color

    Copy the SSH password and we will make a local directory to access the WordPress installation of our containter.
    cd ~
    mkdir largo.mount.from.docker.container
    sshfs user@$DIP:/var/www $HOME/largo.mount.from.docker.container
    cd largo.mount.from.docker.container
    PROJECT=$(pwd -P)

    Now, we can visit the WordPress installation and finish setting up. From the host machine, it should be ‘HTTP://127.0.0.1:8000’. There you can configure Title, Username, Password, et cet. and finish installing WordPress.

    Now, let’s get us some Largo! Since this is a test project, we’ll sacrifice security to make things easy. Our Docker WordPress site isn’t ready for us to easily install the Largo parent theme, so we’ll make the web directory writable by everybody. Generally, this is not a practice I would condone. It’s okay while we’re experimenting but permissions are very important on live systems!

    Lastly, we’ll download and install Largo and the Largo child theme stub.
    ssh user@$DIP 'sudo chmod -R 777 /var/www'
    wget https://github.com/INN/Largo/archive/master.zip -O $PROJECT/wp-content/themes/largo.zip
    unzip $PROJECT/wp-content/themes/largo.zip -d $PROJECT/wp-content/themes/
    mv $PROJECT/wp-content/themes/Largo-master $PROJECT/wp-content/themes/largo
    wget http://largoproject.wpengine.netdna-cdn.com/wp-content/uploads/2012/08/largo-child.zip -O $PROJECT/wp-content/themes/largo-child.zip
    unzip $PROJECT/wp-content/themes/largo-child.zip -d $PROJECT/wp-content/themes
    rm -rf $PROJECT/wp-content/themes/__MACOSX/

    We are now ready to customize our Project Largo child theme!


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    Permalink: 20140217.project.largo.docker

    Wed, 15 May 2013

    Git: an untracked mess?

    There may be times when you find your Git repository burdened with scads of untracked files left aside while twiddling, testing bug patches, or what-have-youse.

    For the especially scatter-brained among us, these things can go unchecked until a day when the useful bits of a git status scroll off the screen due to utterly unimportant stuff. Well, hopefully unimportant.

    But we’d better not just cleave away everything that we haven’t checked in. You wonder:
    What if there’s something important in one of those files?

    You are so right!

    Let’s fix this!

    Firstly, we want a solution that’s reproducible. Only want to invent this wheel once, right?

    Let’s begin with the play-by-play:

    Git, we want a list of what isn’t tracked: git ls-files -o --exclude-standard -z

    We’ll back these files up in our home directory (~), using CPIO but we don’t want a poorly-named directory or finding anything will become its own obstacle. So we’ll take use the current date (date +%Y-%m-%d), directory (pwd) and branch we’re using (git branch) and we’ll twist all of it into a meaningful, but appropriate, directory name using sed. git ls-files -o --exclude-standard -z | cpio -pmdu ~/untracked-git-backup-`date +%Y-%m-%d`.`pwd | sed 's,^\(.*/\)\?\([^/]*\),\2,'`.`git branch | grep "*" | sed "s/* //"`/

    Then Tell Git to remove the untracked files and directories: git clean -d -f

    Ahhhh… Much better. Is there anything left out? Perhaps. What if we decide that moving these files away was a mistake? The kind of mistake that breaks something. If we realize right away, it’s easily-enough undone. But what if we break something and don’t notice for a week or two? It’d probably be best if we had an automated script to put things back the way they were. Let’s do that.

    Simple enough. We’ll just take the opposite commands and echo them into a script to be used in case of emergency.

    Create the restore script (restore.sh), to excuse faulty memory: echo "(cd ~/untracked-git-backup-`date +%Y-%m-%d`.`pwd | sed 's,^\(.*/\)\?\([^/]*\),\2,'`.`git branch | grep "*" | sed "s/* //"`/; find . -type f \( ! -iname 'restore.sh' \) | cpio -pdm `pwd`)" > ~/untracked-git-backup-`date +%Y-%m-%d`.`pwd | sed 's,^\(.*/\)\?\([^/]*\),\2,'`.`git branch | grep "*" | sed "s/* //"`/restore.sh

    Make the restore script executable: chmod u+x ~/untracked-git-backup-`date +%Y-%m-%d`.`pwd | sed 's,^\(.*/\)\?\([^/]*\),\2,'`.`git branch | grep "*" | sed "s/* //"`/restore.sh

    Lastly, the magic, compressed into one line that will stop if any command does not report success: a='untracked-git-backup-'`date +%Y-%m-%d`.`pwd | sed 's,^\(.*/\)\?\([^/]*\),\2,'`.`git branch | grep "*" | sed "s/* //"`; git ls-files -o --exclude-standard -z | cpio -pmdu ~/$a/ && git clean -d -f && echo "(cd ~/$a/; find . -type f \( ! -iname 'restore.sh' \) | cpio -pdm `pwd`)" > ~/$a/restore.sh && chmod +x ~/$a/restore.sh; unset a


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    Permalink: 20130515.git.untracked.mess