c0d3 :: j0rg3

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

Tue, 07 Mar 2017

Privacy Part II: VPN/IPVanish - Install IPVanish on Kali Linux

Okay, so you’re running Whonix, Tails or, at least, TorBrowser.

What’s next? You may wish to consider using a VPN. In simple terms, it’s somewhat similar to what Tor offers. That is: you connect to the VPN and your connection passes through them such that the site that you are visiting will see the VPN’s IP address rather than yours. Of course, that means that you can chain them.

That is: (You)->VPN->Tor->Exit node->Web site

The reason that you might feel compelled to take this step is that a party which is able to see your traffic into and out of Tor could still identify you. The thinking is that the parties who wish to interfere with your privacy could be compelled to run Tor bridges, relays and exit nodes. If traffic from your IP address could be matched to requests coming from the Tor exit node then you could, effectively, be identified.

Some people hold that using a VPN to access Tor does not improve your anonymousness. I am not among them. In particular, you will find that IPVanish offers VPN service for under $7 per month and is popular among users of the Tor network. Which means that in addition to the fact that IPVanish is not logging your traffic, there’s an excellent chance that other users are going from IPVanish into Tor, helping to reduce the uniqueness of your traffic.

By the way, I’d suggest poking around the web a little bit. While their prices are already great you can find some even deeper discounts: https://signup.ipvanish.com/?aff=vpnfan-promo

IPVanish’s site offers instructions for installing the VPN in Ubuntu so we’re going to take a look at using IPVanish in Kali — including an interesting and unanticipated snag (and, of course, how to fix it).

Let’s grab the OpenVPN configuration:
wget http://www.ipvanish.com/software/configs/ca.ipvanish.com.crt; wget http://www.ipvanish.com/software/configs/ipvanish-US-New-York-nyc-a01.ovpn

We will need the OpenVPN package for Gnome:
apt install network-manager-openvpn-gnome

Click on the tray in the upper right corner, then the wrench/screwdriver icon:

Select the ‘Network’ folder icon:

We’re choosing ‘Wired’ (even though we’re using wlan0 interface):

We’re setting up a VPN, of course:

Import from file:

Choose the configuration file that we downloaded previously:

Enter ‘User name’ and ‘Password’:

We are connected!

Verified at IPVanish’s site: https://www.ipvanish.com/checkIP.php

And this is where I had anticipated the installation instructions would end.

I just wanted to check a few more things. And I would love to tell you that it was simply my thoroughness and unbridled CLI-fu that led to discover that I was still making ipv6 connections outside of the VPN. Seems that it wasn’t noticed by the test at IPVanish because they deal only in ipv4. I was able to prove my ipv6 address and geolocation by using: http://whatismyipaddress.com/

Further, we can establish that the test at IPVanish is not ipv6-compatible with a quick test.

The easy fix here is to disable ipv6 locally. It is plausible that this could cause unintended consequences and, to be thorough, it would be best to handle your VPN at the firewall. Having support for OpenVPN, you’ll be able to get this running with a huge variety of routing/firewall solutions. You can grab any number of tiny computers and build a professional-quality firewall solution with something like pfSense. Maybe we’ll take a look at getting that configured in a future post.

But, for now, let’s shut down ipv6 in a way that doesn’t involve any grandiose hand-waving magic (i.e., unexplained commands which probably should work) and then test to get confidence in our results.

Let’s use sysctl to find our ipv6 kernel bits and turn them off. Then we’ll load our configuration changes. As a safety, it wouldn’t be a bad idea to look in /etc/sysctl.conf to verify that there aren’t any ipv6 configs in there.

We’ll back up our config file then turn off everything ipv6 by listing everything with the words ‘ipv6’ and ‘disable’:
cp /etc/sysctl.conf /etc/$(date +%Y-%m-%d.%H-%M-%S).sysctl.conf.bak && \
sysctl -a | grep -i ipv6 | grep disable | sed 's/0/1/g' >> /etc/sysctl.conf && \
sysctl -p

To explain what we’re doing:
List all kernel flags; show uonly those containing the string ‘ipv6’; of those that remain, show only those that contain the string ‘disable’:
sysctl -a | grep -i ipv6 | grep disable
Replace the 0 values with 1, to turn ON the disabling, by piping output to:
sed 's/0/1/g'
That all gets stuck on the end of ‘sysctl.conf’ by redirecting stdout to append to the end of that file:
>> /etc/sysctl.conf
Then we reload with:
sysctl -p

Then as a final sanity-check we’ll make sure we can’t find any ipv6 packets sneaking about:
tcpdump -t -n -i wlan0 -s 256 -vv ip6

At this point, assuming our tcpdump doesn’t show any traffic, we should be ipv6-free with all of our ipv4 traffic shipped-off nicely through IPVanish!


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Permalink: 20170307.privacy.vpn.ipvanish

Sun, 13 Jul 2014

Simple Protection with iptables, ipset and Blacklists

Seems I’ve always just a few more things going on than I can comfortably handle. One of those is an innocent little server holding the beginnings of a new project.

If you expose a server to the Internet, very quickly your ports are getting scanned and tested. If you’ve an SSH server, there are going to be attempts to login as ‘root’ which is why it is ubiquitously advised that you disable root login. Also why many advise against allowing passwords at all.

We could talk for days about improvements; it’s usually not difficult to introduce some form of two-factor authentication (2FA) for sensitive points of entry such as SSH. You can install monitoring software like Logwatch which can summarize important points from your logs, such as: who has logged via SSH, how many times root was used, etc.

DenyHosts and Fail2ban are very great ways to secure things, according to your needs.

DenyHosts works primarily with SSH and asks very little from you in way of configuration, especially if you’re using a package manager to install a version that is configured for the distribution on which you’re working. If you’re installing from source you may need to find where are your SSH logs (e.g., /var/log/secure, /var/log/auth.log). It’s extremely easy to set up DenyHosts to synchronize so that you’re automatically blocking widely-known offenders whether or not they’re after your server.

In contrast, Fail2ban is going to take more work to get set up. However, it is extremely configurable and works with any log file you point it toward which means that it can watch anything (e.g., FTP, web traffic, mail traffic). You define your own jails which means you can ban problematic IP addresses according to preference. Ban bad HTTP attempts from HTTP only or stick their noses in the virtual corner and don’t accept any traffic from them until they’ve served their time-out by completely disallowing their traffic. You can even use Fail2ban to scan its own logs, so repeating offenders can be locked out for longer.

Today we’re going to assume that you’ve a new server that shouldn’t be seeing any traffic except from you and any others involved in the project. In that case, you probably want to block traffic pretty aggressively. If you’ve physical access to the server (or the ability to work with staff at the datacenter) then it’s better to err in the direction of accidentally blocking good guys than trying to be overly fault-tolerant.

The server we’re working on today is a Debian Wheezy system. It has become a common misconception that Ubuntu and Debian are, intents and purposes, interchangeable. They’re similar in many respects and Ubuntu is great preparation for using Debian but they are not the same. The differences, I think, won’t matter for this exercise but I am unsure because this was written using Wheezy.

Several minutes after bringing my new server online, I started seeing noise in the logs. I was still getting set up and really didn’t want to stop and take protective measures but there’s no point in securing a server after its been compromised. The default Fail2ban configuration was too forgiving for my use. It was scanning for 10 minutes and banning for 10 minutes. Since only a few people should be accessing this server, there’s no reason for anyone to be trying a different password every 15 minutes (for hours).

I found a ‘close-enough’ script and modified it. Here, we’ll deal with a simplified version.

First, lets create a name for these ne’er-do-wells in iptables:
iptables -N bad_traffic

For this one, we’ll use Perl. We’ll look at our Apache log files to find people sniffing ‘round and we’ll block their traffic. Specifically, we’re going to check Apache’s ‘error.log’ for the phrases ‘File does not exist’ and ‘client denied by server configuration’ and block people causing those errors. This would be excessive for servers intended to serve the general populace. For a personal project, it works just fine as a ‘DO NOT DISTURB’ sign.


#!/usr/bin/env perl
use strict;
use POSIX qw(strftime);

my $log = ($ARGV[0] ? $ARGV[0] : "/var/log/apache2/error.log");
my $chain = ($ARGV[1] ? $ARGV[1] : "bad_traffic");

my @bad = `grep -iE 'File does not exist|client denied by server configuration' $log |cut -f8 -d" " | sed 's/]//' | sort -u`;
my @ablk = `/sbin/iptables -S $chain|grep DROP|awk '{print $4}'|cut -d"/" -f1`;

foreach my $ip (@bad) {
if (!grep $_ eq $ip, @ablk) {
chomp $ip;
`/sbin/iptables -A $chain -s $ip -j DROP`;
print strftime("%b %d %T",localtime(time))." badht: blocked bad HTTP traffic from: $ip\n";
}
}

That gives us some great, utterly unforgiving, blockage. Looking at the IP addresses attempting to pry, I noticed that most of them were on at least one of the popular block-lists.

So let’s make use of some of those block-lists! I found a program intended to apply those lists locally but, of course, it didn’t work for me. Here’s a similar program; this one will use ipset for managing the block-list though only minor changes would be needed to use iptables as above:

#!/bin/bash
IP_TMP=ip.tmp
IP_BLACKLIST_TMP=ip-blacklist.tmp

IP_BLACKLIST=ip-blacklist.conf

WIZ_LISTS="chinese nigerian russian lacnic exploited-servers"

BLACKLISTS=(
"http://danger.rulez.sk/projects/bruteforceblocker/blist.php" # BruteForceBlocker IP List
"http://rules.emergingthreats.net/blockrules/compromised-ips.txt" # Emerging Threats - Compromised IPs
"http://www.spamhaus.org/drop/drop.txt" # Spamhaus Don't Route Or Peer List (DROP)
"http://www.spamhaus.org/drop/edrop.txt" # Spamhaus Don't Route Or Peer List (DROP) Extended
"http://cinsscore.com/list/ci-badguys.txt" # C.I. Army Malicious IP List
"http://www.openbl.org/lists/base.txt" # OpenBL.org 90 day List
"http://www.autoshun.org/files/shunlist.csv" # Autoshun Shun List
"http://lists.blocklist.de/lists/all.txt" # blocklist.de attackers
)

for address in "${BLACKLISTS[@]}"
do
echo -e "\nFetching $address\n"
curl "$address" >> $IP_TMP
done

for list in $WIZ_LISTS
do
wget "http://www.wizcrafts.net/$list-iptables-blocklist.html" -O - >> $IP_TMP
done

wget 'http://wget-mirrors.uceprotect.net/rbldnsd-all/dnsbl-3.uceprotect.net.gz' -O - | gunzip | tee -a $IP_TMP

grep -o '^[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}[/][0-9]\{1,3\}' $IP_TMP | tee -a $IP_BLACKLIST_TMP
grep -o '^[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}[^/]' $IP_TMP | tee -a $IP_BLACKLIST_TMP

sed -i 's/\t//g' $IP_BLACKLIST_TMP
sort -u $IP_BLACKLIST_TMP | tee $IP_BLACKLIST

rm $IP_TMP
rm $IP_BLACKLIST_TMP

wc -l $IP_BLACKLIST

if hash ipset 2>/dev/null
then
ipset flush bloxlist
while IFS= read -r ip
do
ipset add bloxlist $ip
done < $IP_BLACKLIST
else
echo -e '\nipset not found\n'
echo -e "\nYour bloxlist file is: $IP_BLACKLIST\n"
fi


Download here:
    bad_traffic.pl
    bloxlist.sh


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Permalink: 20140713.simple.protection.with.iptables.ipset.and.blacklilsts

Wed, 08 May 2013

Deleting backup files left behind by Vim

It’s generally a great idea to have Vim keep backups. Once in awhile, they can really save your bacon.

The other side of that coin, though, is that they can get left behind here and there, eventually causing aggravation.

Here’s a snippet to find and eliminate those files from the current directory down:

find ./ -name '*~' -exec rm '{}' \; -print -or -name ".*~" -exec rm {} \; -print
This uses find from the current directory down (./) to execute an rm statement on all files with an extension ending in tilde (~)
Alternatively, you could just store your backups elsewhere. In Vim, use :help backupdir for more information.


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Permalink: 20130508.delete.vim.backups

Tue, 07 May 2013

Welcome, traveler.

Thanks for visiting my little spot on the web. This is a Blosxom ‘blog which, for those who don’t know, is a CGI written in Perl using the file-system (rather than a database).

To the CLI-addicted, this is an awesome little product. Accepting, of course, that you’re going to get under the hood if you’re going to make it the product you want. After some modules and hacking, I’m pleased with the result.

My posts are just text files, meaning I start a new one like: vim ~posts/`date +%Y%m%d`.brief.subject.txt

Note: the back-ticks (`) tell the system that you want to execute the command between ticks, and dynamically insert its output into the command. In this case, the command date with these parameters:
  1. (+) we’re going to specify a format
  2. (%Y) four-digit year
  3. (%m) two-digit month
  4. (%d) two-digit day
That means the command above will use Vim to edit a text file named ‘20130507.brief.subject.txt’ in the directory I have assigned to the hash of ‘posts’. (using hash this way is a function of Zsh that I’ll cover in another post)

In my CLI-oriented ‘blog, I can sprinkle in my own HTML or use common notation like wrapping a word in underscores to have it underlined, forward-slashes for italics and asterisks for bold.

Toss in a line that identifies tags and, since Perl is the beast of Regex, we pick up the tags and make them links, meta-tags, etc.

Things here are likely to change a lot at first, while I twiddle with CSS and hack away at making a Blosxom that perfectly fits my tastes — so don’t be too alarmed if you visit and things look a tad wonky. It just means that I’m tinkering.

Once the saw-horses have been tucked away, I’m going to take the various notes I’ve made during my years in IT and write them out, in a very simple breakdown, aimed at sharing these with people who know little about how to negotiate the command line. The assumption here is that you have an interest in *nix/BSD. If you’ve that and the CLI is not a major part of your computing experience, it probably will be at some point. If you’re working on systems remotely, graphical interfaces often just impede you.

Once you’ve started working on remote machines, the rest is inevitable. You can either remember how to do everything two ways, through a graphical interface and CLI — or just start using the CLI for everything.

So let’s take a little journey through the kinds of things that make me love the CLI.


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Permalink: 20130507.greetings