My website is down. Now what? Part 5 – SSL/HTTPS Issues

This is part of a series on diagnosing your website outage issues. This is part five; links to the other parts are here.

In Part 1 of this series we covered the overview of what could have broken to cause your website to go down. In Part 2, we started working through those possible issues by diagnosing DNS issues. In Part 3 we diagnosed routing issues. In Part 4 we looked at how to diagnose problems with any architectural layers such as firewalls. Now that we know all that is good, we need to look at what is going on with the web host itself. If your site runs over HTTPS, there are a myriad of issues that broken certificates or broken code can cause and that is the subject of this article.

This is not an article on what SSL is or how it works, but some basic terms and knowledge are necessary to understand the content of this article so I will lay them out.

Although secure web sessions are referred to as ‘SSL’ and certificates that provide this security are called ‘SSL Certificates’ the more correct term is TLS. The Transport Layer Security (TLS) standard replaced the Secure Sockets Layer (SSL) standard. But to avoid confusion I will use SSL since it is in more common use even though this guy will kill me.

SSL certificates are the mechanism by which secure Hyper Text Transport Protocol (HTTP) sessions are created. Those secure HTTP sessions are referred to as HTTPS (note the ‘S’ denoting Secure). Therefore, the proper way to think of this is that traffic between your website and your visitor is encrypted when they connect to your web server using https:// links and that encryption is implemented by means of the SSL certificate installed on your host.

Lastly before we jump in, it’s important to understand what SSL certificates actually do. They have two jobs:

  1. Encrypt the traffic between your website visitor and your website so that it cannot be read if it is intercepted by bad guys. Intercepting traffic is easier than you probably think but if the requests are encrypted, bad guy only gets a bunch of encrypted blobs.
  2. Provide non-repudiation to your browser meaning that it assures your browser that it is connecting to the website it asked for. Imagine if you told your browser to connect to your bank, but it connected to some other bad site and you entered your username and password into that bad site. SSL non-repudiation prevents that. I wrote an article on the others things SSL certificates do for the Sucuri blog here if you’d like more information on that.

So, knowing the two main jobs SSL does, what can go wrong on your SSL-enabled site? Here are some of the most common:

Continue reading “My website is down. Now what? Part 5 – SSL/HTTPS Issues”

My website is down. Now what? Part 4 – Layers

This is part of a series on diagnosing your website outage issues. This is part four; links to the other parts are here.

In Part 1 of this series we covered the overview of what could have broken to cause your website to go down. In Part 2, we started working through those possible issues by diagnosing DNS issues. In Part 3 we diagnosed routing issues. Now that we know your domain’s DNS is good, the routes are good, we’re going to start looking at any layers you may have in your architecture.

Image showing a turnstile inside a door but there is so much room around the turnstile that you can just walk through it without using it.The term “layers’ refers to things like firewalls or Content Distribution Networks (CDN) that may be present in your architecture. If you don’t use these things, you can skip to the next section which I will link to here when it is ready.

A typical website architecture looks like this:

website visitor -> web hosting server

There are no layers involved in this architecture. Your visitor simply hits your website directly. That works just fine and represents probably 80% of the use cases out there, but an increasing number of website owners are starting to employ firewalls and CDNs to secure and speed up their sites. If you employ a firewall such as The Mighty Sucuri CloudProxy, your architecture changes to look like this:

website visitor -> Sucuri CloudProxy -> web hosting server

If you harken back to Part 2 where we discussed routing, then you will recognize that this change in architecture introduces another point of failure for your website. How do you test those parts to ensure they are functioning? There are a few options.

Continue reading “My website is down. Now what? Part 4 – Layers”

My website is down. Now what? Part 3 – Routing

This is part of a series on diagnosing your website outage issues. This is part three; links to the other parts are here.

In Part 1 of this series we covered the overview of what could have broken to cause your website to go down. In Part 2, we started working through those possible issues by diagnosing DNS issues. Now that we know your domain’s DNS is good, we’re going to start looking at the routing. In other words, now that we know where your domain is (DNS), are there any roads to get there (routing)?

Many people misunderstand how the web works. I blame the media and well-meaning explainers for suggesting and continuing to propagate the notion that we “log on” or “visit” websites. The problem with these terms is that they naturally call to mind the concept of “going” to a website which is the exact opposite of how web surfing works. Instead of your browser being some sort of vehicle that goes to websites, it is a static piece of software that sits on your computer and issues demands for websites to come to it. Websites come to you, you do not go to them.

Internet routing imageWhen you click a link or type in a domain name, your browser issues a request across the Internet to that domain’s web server and says “give me that page”. Well behaved web hosts comply and the content your browser requested is downloaded to your computer and your web browser then renders it nicely so you can see and interact with it. In order for this to happen, there has to be a pathway on the Internet that can transfer your web browser’s request to the web server and transfer the response (content) from the web server back to your web browser. Those pathways are called routes and a big part of website troubleshooting involves diagnosing routing issues.

Continue reading “My website is down. Now what? Part 3 – Routing”

Series: My website is down. Now what?

Panic button imageThis is a multi-part series about how to keep your cool when your website is down and be part of the solution instead of a seething mass of non-helpfulness.

This tutorial assumes the reader has some basic knowledge of how websites function as I believe it is unforgivable to be wholly and wilfully ignorant of the workings of things we buy. However, I maintain a quick primer here on the various moving parts of websites and their ecosystem should you need a quick refresher.

  1. Part 1: Overview
  2. Part 2: DNS Issues
  3. Part 3: Routing
  4. Part 4: Layers (firewalls, etc.)
  5. Part 5: SSL/TLS and HTTPS problems.

My website is down. Now what? Part 2 – DNS Issues

This is part of a series on diagnosing your website outage issues. This is part two; links to the other parts are here.

In Part 1 of this series I covered the fact that your web browser needs to know the IP address of your website which is done via a process called domain name resolution. This happens under the covers and is facilitated by your domain’s name servers which are part of the Domain Name System. This domain name to IP address resolution is absolutely fundamental to the functioning of the web and if there are issues with your domain’s DNS records, or your local computer’s DNS, you won’t be visiting your website today.

How to identify a DNS problem

Computers have local DNS caches and even networks sometimes cache DNS records. When those caches exist, your computer’s query for an IP address will never hit your actual name servers. That means if those caches are wrong, your computer will have no idea how to access your site. So, how do you test this out?

The first piece of information you need is the IP address that your website is supposed to point to. For most of us, that is the IP address your web hosting service provided to you when you signed up. If you have other layers (as described in Part 1 of this series) then the IP address would have been provided to you by that service provider. If you’ve lost that information, then you can open a support ticket with that provider and ask them what IP address your domain should be pointed to. Armed with that information, you can then compare that to the IP address your computer thinks your domain is at.

The easiest way to check what IP address your computer associates with your domain is to run a simple ping command. You can do this from the command prompt of any Windows, Linux or Mac computer like so:

Your output may look slightly different but the first line-ish will show you the IP address that your computer thinks your domain is at. In my case, this is 192.124.249.6 which is correct. I know that my DNS records are supposed to point to that IP address as that is my firewall IP address.

If my output contained some other IP address like so:

That’s a big red flag.

Continue reading “My website is down. Now what? Part 2 – DNS Issues”

My website is down. Now what? Part 1 – Overview

This is part of a series on diagnosing your website outage issues. This is part one; links to the other parts are here.

Website down! Aoooogah! Aoooogah!

ERR_NAME_NOT_RESOLVED
Google Chrome showing a DNS error “ERR_NAME_NOT_RESOLVED”
We’ve all had that feeling – you go to your website and it’s not there. It’s down. There may or may not be an error message giving you some clue what happened and now you’ve got to figure out what to do.

First thing’s first – focus on figuring out where the break is. Don’t revert immediately into victim mode and start opening angry support tickets at every person who has ever touched your website in an all-consuming witch hunt. It’s your site, take control.

Understand your architecture

Everyone who owns a website has their stuff set up differently. Domains are purchased from somewhere, sometimes years ago; a web hosting service hosts your website somewhere; some company handles your name servers (Domain Name Service) and you may have other steps along the way such as a Content Distribution Network (CDN) or firewall. Only you know all this stuff, so bring that information to the table.

Understand the problem

“Down” is not a useful description of a website’s condition. If your website is not displaying, it’s useful to be more specific.

Does your web browser just show a blank white page with nothing on it? Is there an error message somewhere on the page that explains what has happened? Does your website load partially, but have some missing elements? Define what “down” means because the particular symptoms you’re seeing will lead to better investigations into the root cause.

Continue reading “My website is down. Now what? Part 1 – Overview”

OpenSSH v7 and DSA key support. AKA “Permission denied (publickey)”

sshI have a little personal server farm with a handful of hosts that run things like my websites, a BBS and my VPN server. I recently upgraded my desktop to Kubuntu 16.04 and suddenly my SSH key was no longer working. I started seeing this when I tried to log in:

I began troubleshooting to determine what was wrong with my key. I had just upgraded my workstation, after all, I could have restored the wrong keys from my backup. That is when I discovered that I was able to log in to some of my servers, just not all of them. That puzzled me because I knew I had not touched the servers and I thought that they all used the same key. What could cause my key to work on some servers, but not others? It had to be a client-side issue but I didn’t know what.

I have a continuity plan to access my servers if anything like this should happen so I implemented it and it allowed me to look in the auth.log. I saw these messages in the server logs:

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