Category Archives: Tutorial/Howto

Blog posts within this category are always step-by-step tutorials with detailed configurations and many screenshots. Therefore, they are easy to understand.

How to use DANE/TLSA

Authentication, Certificate, DNS/DNSSEC, TLS, Tutorial/Howto, , , , , , , , , ,

DNS-based Authentication of Named Entities (DANE) is a great feature that uses the advantages of a DNSSEC signed zone in order to tell the client which TLS certificate he has to expect when connecting to a secure destination over HTTPS or SMTPS. Via a secure channel (DNSSEC) the client can request the public key of the server. This means, that a Man-in-the-Middle attack (MITM) with a spoofed certificate would be exposed directly, i.e., is not possible anymore. Furthermore, the trust to certificate authorities (CAs) is not needed anymore.

In this blog post, I will show how to use DANE and its DNS records within an authoritative DNS server to provide enhanced security features for the public.

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DNSSEC Signing w/ BIND

Crypto, DNS/DNSSEC, Linux, Tutorial/Howto, , , , , , , , ,

To solve the chicken-or-egg problem for DNSSEC from the other side, let’s use an authoritative DNS server (BIND) for signing DNS zones. This tutorial describes how to generate the keys and configure the “Berkeley Internet Name Domain” (BIND) server to automatically sign zones. I am not explaining any details of DNSSEC, but only the configuration and verification steps for a concrete BIND server.

It is really easy to tell BIND to do the inline signing. With this option enabled, the admin can still configure the database for his zone files without any relation to DNSSEC. Everything with signing and maintaining is fully done by BIND without any user interaction. Great.

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DNSSEC Validation with Unbound on a Raspberry

DNS/DNSSEC, Raspberry Pi, Tutorial/Howto, , , , ,

To overcome the chicken-or-egg problem for DNSSEC (“I don’t need a DNSSEC validating resolver if there are no signed zones”), let’s install the DNS server Unbound on a Raspberry Pi for home usage. Up until then, domain names are DNSSEC validated. I am listing the commands to install Unbound on a Raspberry Pi as well as some further commands to test and troubleshoot it. Finally, I am showing a few Wireshark screenshots from a sample iterative DNS capture. Here we go:

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BIND DNSSEC Validation

DNS/DNSSEC, Tutorial/Howto, ,

If you are searching for a DNSSEC validating DNS server, you can use BIND to do that. In fact, with a current version of BIND, e.g. version 9.10, the dnssec-validation is enabled by default. If you are already using BIND as a recursive or forwarding/caching server, you’re almost done. If not, this is a very basic installation guide for BIND with DNSSEC validation enabled and some notes on how to test it.

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Basic BIND Installation

DNS/DNSSEC, Linux, Tutorial/Howto, , , , , , , , ,

This is a basic tutorial on how to install BIND, the Berkeley Internet Name Domain server, on a Ubuntu server to run it as an authoritative DNS server. It differs from other tutorials because I am using three servers (one as a hidden primary and two secondaries as the publicly accessible ones), as well as some security such as denying recursive lookups and public zone transfers, as well as using TSIG for authenticating internal zone transfers. That is, this post is not an absolute beginner’s guide.

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Using NetFlow with nProbe for ntopng

Monitoring, Network, Tutorial/Howto, , , , , , , ,

This blog post is about using NetFlow for sending network traffic statistics to an nProbe collector which forwards the flows to the network analyzer ntopng. It refers to my blog post about installing ntopng on a Linux machine. I am sending the NetFlow packets from a Palo Alto Networks firewall.

My current ntopng installation uses a dedicated monitoring ethernet port (mirror port) in order to “see” everything that happens in that net. This has the major disadvantage that it only gets packets from directly connected layer 2 networks and vlans. NetFlow on the other hand can be used to send traffic statistics from different locations to a NetFlow flow collector, in this case to the tool nProbe. This single flow collector can receive flows from different subnets and routers/firewalls and even VPN tunnel interfaces, etc. However, it turned out that the “real-time” functionalities of NetFlow are limited since it only refreshes flows every few seconds/bytes, but does not give a real-time look at the network. It should be used only for statistics but not for real-time troubleshooting.

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ntopng Installation

Linux, Monitoring, Network, Tutorial/Howto, , , , , , ,

Some time ago I published a post introducing ntopng as an out-of-the-box network monitoring tool. I am running it on a Knoppix live Linux notebook with two network cards. However, I have a few customers that wanted a persistent installation of ntopng in their  environment. So this is a step-by-step tutorial on how to install ntopng on a Ubuntu server with at least two NICs.

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Tufin SecureTrack: Adding Devices

Tufin, Tutorial/Howto, , , , , , , , ,

Since a few weeks I am using Tufin SecureTrack in my lab. A product which analyzes firewall policies about their usage and their changes by administrators (and much more). Therefore, the first step is to connect the firewalls to SecureTrack in two directions: SSH from SecureTrack to the device to analyze the configuration, as well as Syslog from the device to SecureTrack to real-time monitor the policy usage.

This blog post shows the adding of the following firewalls into Tufin: Cisco ASA, Fortinet FortiGate, Juniper ScreenOS, and Palo Alto PA.

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FortiGate 2-Factor Authentication via SMS

Authentication, Fortinet, Password, Tutorial/Howto, , , ,

Two-factor authentication is quite common these days. That’s good. Many service providers offer a second authentication before entering their systems. Beside hardware tokens or code generator apps, the traditional SMS on a mobile phone can be used for the second factor.

The FortiGate firewalls from Fortinet have the SMS option built-in. No feature license is required for that. Great. The only thing needed is an email-to-SMS provider for sending the text messages. The configuration process on the FortiGate is quite simple, however, both the GUI as well as the CLI are needed for that job. (Oh Fortinet, why aren’t you improving your GUI?)

Here is a step-by-step configuration tutorial for the two-factor authentication via SMS from a FortiGate firewall. My test case was the web-based SSL VPN portal.

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Juniper ScreenOS: DHCPv6 Prefix Delegation

DHCP/DHCPv6, IPv6, Juniper Networks, Routing, Tutorial/Howto, , , , , , , ,

The Juniper ScreenOS firewall is one of the seldom firewalls that implements DHCPv6 Prefix Delegation (DHCPv6-PD). It therefore fits for testing my dual stack ISP connection from Deutsche Telekom, Germany. (Refer to this post for details about this dual stack procedure.)

It was *really* hard to get the correct configuration in place. I was not able to do this by myself at all. Also Google did not help that much. Finally, I opened a case by Juniper to help me finding the configuration error. After four weeks of the opened case, I was told which command was wrong. Now it’s working. ;) Here we go.

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Policy Based Forwarding on a Palo Alto with different Virtual Routers

Palo Alto Networks, Routing, Tutorial/Howto, , , , ,

This guide is a little bit different to my other Policy Based Forwarding blog post because it uses different virtual routers for both ISP connections. This is quite common to have a distinct default route for both providers. So, in order to route certain traffic, e.g., http/https, to another ISP connection, policy based forwarding is used.

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Policy-Based Routing on ScreenOS with different Virtual Routers

Juniper Networks, Routing, Tutorial/Howto, , , , , ,

I already puslished a blog post concerning policy-based routing on a Juniper firewall within the same virtual router (VR). For some reasons, I was not able to configure PBR correctly when using multiple VRs. Now it works. ;) So, here are the required steps:

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Roundcube Installation Guide

Linux, Tutorial/Howto, , , , , , , , , ,

Roundcube is an email webclient which is easy and intuitive to use. I am using it for my private mails, connecting via IMAP and SMTP to my hoster. One of the great advantages is the “flag” option which is synchronized via IMAP to my Apple devices.

Following is a step-by-step installation guide for Roundcube plus an update scenario. It is a kind of “memo for myself”, but hopefully, others can use it as well.

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