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


    Tags: , , , ,
    Permalink: 20170102.securing.a.new.server

    Sat, 25 Jan 2014

    Network-aware Synergy client

    My primary machines are *nix or BSD variants, though I certainly have some Windows-based rigs also. Today we’re going to share some love with Windows 7 and PowerShell.

    One of my favorite utilities is Synergy. If you’re not already familiar it allows to you seamlessly move from the desktop of one computer to another with the same keyboard and mouse. It even supports the clipboard so you might copy text from a GNU/Linux box and paste it in a Windows’ window. Possibly, they have finished adding drag and drop to the newer versions. I am not sure because I run a relatively old version that is supported by all of the machines that I use regularly.

    What’s the problem, then? The problem was that I was starting my Synergy client by hand. Even more disturbing, I was manually typing the IP address at work and at home, twice or more per weekday. This behavior became automated by my brain and continued for months unnoticed. But this is no kind of life for a geek such as myself, what with all this superfluous clicking and tapping!

    Today, we set things right!

    In my situation, the networks that I use happen to assign IP addresses from different subnets. If you’ve not the convenience of that situation then you might need to add something to the script. Parsing an ipconfig/ifconfig command, you could possibly use something like the Default Gateway or the Connection-specific DNS Suffix. Alternatively, you could check for the presence of some network share, a file on server or anything that would allow you to uniquely identify the surroundings.

    As I imagined it, I wanted the script to accomplish the following things

    • see if Synergy is running (possibly from the last location), if so ask if we need to kill it and restart so we can identify a new server
    • attempt to locate where we are and connect to the correct Synergy server
    • if the location is not identified, ask whether to start the Synergy client

    This is how I accomplished that task:

    # [void] simply supresses the noise made loading 'System.Reflection.Assembly'
    [void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")

    # Define Synergy server IP addresses
    $synergyServerWork = "192.168.111.11"
    $synergyServerHome = "192.168.222.22"

    # Define partial IP addresses that will indicate which server to use
    $synergyWorkSubnets = "192.168.111", "192.168.115"
    $synergyHomeSubnets = "192.168.222", "192.168.225"

    # Path to Synergy Client (synergyc)
    $synergyClientProgram = "C:\Program Files\Synergy\synergyc.exe"

    # Path to Syngery launcher, for when we cannot identify the network
    $synergyLauncherProgram = "C:\Program Files\Synergy\launcher.exe"

    # Remove path and file extension to give us the process name
    $processName = $synergyClientProgram.Substring( ($synergyClientProgram.lastindexof("\") + 1), ($synergyClientProgram.length - ($synergyClientProgram.lastindexof("\") + 5) ))

    # Grab current IP address
    $currentIPaddress = ((ipconfig | findstr [0-9].\.)[0]).Split()[-1]

    # Find the subnet of current IP address
    $location = $currentIPaddress.Substring(0,$currentIPaddress.lastindexof("."))


    function BalloonTip ($message)
    {
    # Pop-up message from System Tray
    $objNotifyIcon = New-Object System.Windows.Forms.NotifyIcon
    $objNotifyIcon.Icon = [System.Drawing.Icon]::ExtractAssociatedIcon($synergyClientProgram)
    $objNotifyIcon.BalloonTipText = $message
    $objNotifyIcon.Visible = $True
    $objNotifyIcon.ShowBalloonTip(15000)
    }


    #main

    # If Synergy client is already running, do we need to restart it?
    $running = Get-Process $processName -ErrorAction SilentlyContinue
    if ($running) {
    $answer = [System.Windows.Forms.MessageBox]::Show("Synergy is running.`nClose and start again?", "OHNOES", 4)
    if ($answer -eq "YES") {
    Stop-Process -name $processName
    }
    Else {
    exit
    }
    }

    # Do we recognize the current network?
    if ($synergyWorkSubnets -contains $location) {
    BalloonTip "IP: $($currentIPaddress)`nServer: $($synergyServerWork)`nConnecting to Synergy server at work."
    & $synergyClientProgram $synergyServerWork
    exit
    }
    ElseIf ($synergyHomeSubnets -contains $location) {
    BalloonTip "IP: $($currentIPaddress)`nServer: $($synergyServerHome)`nConnecting to Synergy server at home."
    & $synergyClientProgram $synergyServerHome
    exit
    }
    Else {
    $answer = [System.Windows.Forms.MessageBox]::Show("Network not recognized by IP address: {0}`n`nLaunch Synergy?" -f $unrecognized, "OHNOES", 4)
    if ($answer -eq "YES") {
    & $synergyLauncherProgram
    }
    }

    Then I saved the script in "C:\Program Files\SynergyStart\", created a shortcut and used the Change Icon button to make the same as Synergy’s and made the Target:
    C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -WindowStyle Hidden & 'C:\Program Files\SynergyStart\synergy.ps1'

    Lastly, I copied the shortcut into the directory of things that run when the system starts up:
    %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup

    Now, Synergy connects to the needed server at home and work. If it can’t figure out where it is, it asks if it should run it at all.

    As they say, a millisecond saved is a millisecond earned.

    This post was very nearly published without a Linux equivalent. Nearly.

    Same trick for bash/zsh: #!/bin/zsh

    # Define Synergy server IP addresses
    synergyServerWork="192.168.111.11"
    synergyServerHome="192.168.222.22"

    # Define partial IP addresses that will indicate which server to use
    synergyWorkSubnets=("192.168.111" "192.168.115")
    synergyHomeSubnets=("192.168.222" "192.168.225")

    # Path to Synergy Client (synergyc)
    synergyClientProgram="/usr/bin/synergyc"

    # Path to QuickSyngery, for when we cannot identify the network
    synergyLauncherProgram="/usr/bin/quicksynergy"

    # Remove path and file extension to give us the process name
    processName=`basename $synergyClientProgram`

    # Grab current IP address, assumes '192' is in use. (e.g., 192.168.1.1)
    currentIPaddress=`ip addr show | grep 192 | awk "{print $2}" | sed 's/inet //;s/\/.*//;s/ //g'`

    # Find the subnet of current IP address
    location=`echo $currentIPaddress | cut -d '.' -f 1,2,3`

    for i in "${synergyWorkSubnets[@]}"
    do
    if [ "${i}" = "${location}" ]
    then
    break
    fi
    done

    #main

    # If Synergy client is already running, do we need to restart it?
    running=`ps ax | grep -v grep | grep $processName`
    if [ $running ]
    then
    if `zenity --question --ok-label="Yes" --cancel-label="No" --text="Synergy is running.\nClose and start again?"`
    then
    pkill $processName
    else
    exit
    fi
    fi

    # Do we recognize the current network?
    for i in "${synergyWorkSubnets[@]}"
    do
    if [ "${i}" = "${location}" ]
    then
    notify-send "IP:$currentIPaddress Server:$synergyServerWork [WORK]"
    $synergyClientProgram $synergyServerWork
    exit
    fi
    done

    for i in "${synergyHomeSubnets[@]}"
    do
    if [ "${i}" = "${location}" ]
    then
    notify-send "IP:$currentIPaddress Server:$synergyServerWork [HOME]"
    $synergyClientProgram $synergyServerHome
    exit
    fi
    done

    if `zenity --question --ok-label="Yes" --cancel-label="No" --text="Network not recognized by IP address: $currentIPaddress\nLaunch Synergy?"`
    then
    $synergyLauncherProgram
    fi

    To get it to run automatically, you might choose to call the script from /etc/init.d/rc.local.

    Download here:
      PowerShell:
        synergy.ps1
      GNU/Linux:
        synergy.sh


    Tags: , ,
    Permalink: 20140125.network_aware_synergy_client

    Sun, 09 Jun 2013

    ixquick link maker

    In an effort to promote practical privacy measures, when I send people links to search engines, I choose ixquick. However, my personal settings submit my search terms via POST data rather than GET, meaning that the search terms aren’t in the URL.

    Recently, I’ve found myself hand-crafting links for people and then I paste the link into a new tab, to make sure I didn’t fat-finger anything. Not a problem per se, but the technique leaves room for a bit more efficiency. So I’ve taken the ‘A Search Box on Your Website’ tool offered by ixquick and slightly modified the code it offers, to use GET variables, in a new tab where I can then copy the URL and provide the link to others.

    You can test, or use, it here — I may add it (or a variant that just provides you the link) to the navigation bar above. First, though, I’m going to mention the need to the outstanding minds at ixquick because it would make a LOT more sense on their page than on mine.


    Tags: ,
    Permalink: 20130609.ixquick.search

    Thu, 30 May 2013

    Making ixquick your default search engine

    In this writer’s opinion, it is vitally important that we take reasonable measures now to help insure anonymity, lest we create a situation where privacy no longer exists, and the simple want of, becomes suspicious.

    Here’s how to configure your browser to automatically use a search engine that respects your privacy.

    Chrome:

    1. Click Settings.
    2. Click “Set pages” in the “On startup” section.
    3. Enter https://ixquick.com/eng/ in the “Add a new page” text field.
    4. Click OK.
    5. Click “Manage search engines…”
    6. At the bottom of the “Search Engines” dialog, click in the “Add a new search engine” field.
    7. Enter
      ixquick
      ixquick.com
      https://ixquick.com/do/search?lui=english&language=english&cat=web&query=%s
    8. Click “Make Default”.
    9. Click “Done”.

    Firefox:

    1. Click the Tools Menu.
    2. Click Options.
    3. Click the General tab.
    4. In “When Firefox Starts” dropdown, select “Show my home page”.
    5. Enter https://ixquick.com/eng/ in the “Home Page” text field.
    6. Click one of the English options here.
    7. Check box for “Start using it right away.”
    8. Click “Add”.

    Opera:

    1. Click “Manage Search Engines
    2. Click “Add”
    3. Enter
      Name: ixquick
      Keyword: x
      Address: https://ixquick.com/do/search?lui=english&language=english&cat=web&query=%s
    4. Check “Use as default search engine”
    5. Click “OK”

    Internet Explorer:

        _     ___  _ __        ___   _ _____ ___ 
       | |   / _ \| |\ \      / / | | |_   _|__ \
       | |  | | | | | \ \ /\ / /| | | | | |   / /
       | |__| |_| | |__\ V  V / | |_| | | |  |_| 
       |_____\___/|_____\_/\_/   \___/  |_|  (_) 
      
      
      (This is not a good strategy for privacy.)

    Congratulations!

    \o/

    You are now one step closer to not having every motion on the Internet recorded.

    This is a relatively small measure, though. You can improve your resistance to prying eyes (e.g., browser fingerprinting) by using the Torbrowser Bundle, or even better, Tails, and routing your web usage through Tor, i2p, or FreeNet.

    If you would like more on subjects like anonymyzing, privacy and security then drop me a line via email or Bitmessage me: BM-2D9tDkYEJSTnEkGDKf7xYA5rUj2ihETxVR


    Tags: , , , , , , , , , , , , , ,
    Permalink: 20130530.hey.you.get.offa.my.data