iOS 11 drops 32-bit app support – do we care?

In the upcoming months and until a short while after Apple’s inevitable autumn event where they’ll publicly release their new operating systems, computer magazines and news sites will try to create headlines about how Apple is killing off tens or hundreds of thousands of apps. What’s true and what’s not about this?

Well, yes: iOS 11 kills the support for 32-bit apps. Any such apps on your iPhone or iPad will stop working the day you upgrade to the upcoming operating system. I had a discussion with a friend the other day, regarding Apple’s decision to drop 32-bit OS and app support. He didn’t really like that decision, but I would like to put it in perspective with this beautiful table:

What I’m trying to indicate is that we have two conflicting ways of approaching the problem of legacy software:
One way would be to try to avoid rocking the boat, keeping backwards compatibility even at cost. The good thing about this is what we see in the Windows ecosystem: As long as the computer’s CPU is capable of running in emulation mode for the bitness required1, software just keeps on working. Particularly in business applications, not breaking backwards compatibility may be worth significant sums of money.
The bad thing is a lack of incentive on the part of software manufacturers to update their programs. A “Change is Bad” attitude easily develops when changes are few and far between: people don’t get enough practice in performing change in a safe way, and change management and reliability suffers as a result.

The other way to approach legacy software is to enforce changes for users who want to stay up-to-date. This is the approach Apple has chosen in many areas, for good and for bad. Since they control both their software and their hardware platforms, Apple are in a very good position to simply stop supporting old ways of doing things, and provided they wait a reasonable amount of time this shouldn’t cause a lot of problems. As evident of my table earlier in this post, the last iPhone unable to run a 64-bit environment will turn 5 this year. Considering the evolution of mobile hardware, I’d say anybody who still uses their iPhone 5 has gotten pretty decent mileage out of them – remember that every new software update up until this fall will have worked on that device.

But suppose you actually are heavily invested in some older app; how can you know whether it supports 64-bit iOS versions?
Look at the Version history field in the App Store. If an app was first published in January 2015 or later, or if it was last updated later than June 1 2015, it had to be able to run in a 64-bit environment.

There’s no stopping the wheels of time – iOS and Apple hardware will move on. I could recommend freezing a device, not upgrading it beyond a certain OS version. I won’t, because I consider that a terrible idea, at least for any device connected to the Internet, and for any device used for production work.

Luckily, we won’t see another bitness update in the foreseeable future. The two latest ones were exciting enough.


1 An x86 compatible CPU can by design not run 16-, 32-, and 64-bit code simultaneously, but can switch between 32/16 and 64/32 modes after a hard reset.

SFTP revelations

I got myself into a situation where I had to copy some files from my computer to a server that presented sftp but not scp. Since I’ve never needed to use the sftp protocol from a cli-only machine, I haven’t really thought about how it works in non-interactive mode. Batch mode allows you to create a batch file of sftp commands to execute on the server, but what if you just want to do a single operation?

Pipes to the rescue:

Putting a dash after the -b option causes the command to take batch input from stdin. Piping text to the command, then, means that text is swallowed by the sftp client. Nice and simple.

Securing an Internet accessible server – Part 3

This post is part of a series. Part 1, Part 2.

In the last part I briefly mentioned load balancers and proxies. After thinking about it for a while, I realized I see no reason not to run one, since it simplifies things a bit when setting up secure web services. In this part, we will be setting up a HAProxy server which won’t actually load balance anything, but which will act as a kind of extensible gatekeeper for our web services. In addition, the HAProxy instance will act as the TLS termination point for secure traffic between clients on the Internet and services hosted on our server(s).

This article is written from the perspective of running HAProxy on a separate virtual machine. That’s just for my own convenience, though. If you’re running pfSense for a firewall, you already have HAProxy as a module. It is also possible to run HAProxy directly on your web server, just logically putting it in front of whatever web server software you’re running.

Let’s get started. This post will be a rather long one.

Continue reading “Securing an Internet accessible server – Part 3”

WordPress behind HAProxy with TLS termination

My current project has been to set up a publicly accessible web server with a decent level of security. It has been an interesting exercise in applying “old” knowledge and gathering some new.

This weekend I finished this project for now. The current setup is as follows:
Behind my firewall, where I NAT port 80 and 443 for http and https traffic, I have set up a HAProxy instance. This allows me to do some interesting magic with incoming traffic.

In addition to the traffic manipulation, I also use the HAProxy server for contacting Let’s Encrypt to renew my TLS certificates, and for terminating TLS traffic. The latter has two reasons: a) I’m frankly too lazy to automate installing updated certificates on the web server, and b) I’m running the entire solution on so limited hardware that I’m a little bit worried about putting too much of a strain on it should there ever be a bit more traffic on the machine.

The web server is an Nginx running this very WordPress instance.

Let’s Encrypt configuration

I took the best parts from two different solutions to automate the relatively frequent certificate renewals that Let’s Encrypt enforces. I began by installing the HAProxy ACME Domain Validation Lua Plugin into HAProxy, which ensures that there’s a valid listener to show that I own my domain when I trigger the letsencrypt client program. The beauty of running this through HAProxy is that the process requires no downtime.

For the configuration of the letsencrypt client, I basically stole the scripts from Martijn Braam’s blog BrixIT, just adapting them to the fact that there was a listener provided through the Lua script. The benefit from doing it this way is that the BrixIT method is considerably more flexible than the Lua script when one expects HAProxy to use more than one certificate.

Example config:


The last line also shows how to redirect regular http traffic to a https listener.


TLS termination configuration

The problem with terminating TLS traffic before the web server, is that any good web application should be able to recognize that the client is coming from an insecure connection. Luckily, we can use HAProxy to tell WordPress that the connection was good up until the load balancer and to trust it the rest of the way. Be aware that this is an extremely bad idea if there is any way to reach the web server other than via your HAProxy:



As a final touch, I copied the brute force sandboxing scheme straight from this blog post by Baptiste Assmann over at


The paravirtual SCSI controller and the blue screen of death

For driver reasons, the default disk controller in VMware guests is an emulated LSI card. However, once you install VMware Tools in Windows (and immediately after installing the OS in most modern Linux distributions), it’s possible to slightly lower the overhead for disk operations by switching to the paravirtual SCSI controller (“pvscsi”).

I’m all for lower overhead, so my server templates are already converted to use the more efficient controller, but I still have quite a lot of older Windows servers that still run the LSI controller, so I’ve made it a habit to switch controllers when I have them down for manual maintenance. There is a perfectly good way of switching Windows system drives to a pvscsi controller in VMware, and it’s well documented, so up until a couple of days ago, I’ve never encountered any issues.

Continue reading “The paravirtual SCSI controller and the blue screen of death”

Securing an Internet accessible server – Part 2

In part 1 we made it significantly harder to gain access to our server once it is opened up to the Internet – but we’re not quite ready for that yet. In this post we’re exploring a firewall in Ubuntu, ufw, which stands for “uncomplicated firewall”, and we’ll set up some additional hardening using Fail2Ban to protect ourselves from some common repeated attacks.

Continue reading “Securing an Internet accessible server – Part 2”

Securing an Internet accessible server – Part 1

This article is part of a series. Part 2.

Let’s look at a simple scenario, and see how common tools in the Linux and BSD world can help us:

We want to be able to remote control a server from wherever in the world, but we really don’t want others to be able to log on to it.

In the real world, this is common enough. Understandably, though, anyone who even has a slight understanding of the risks involved will be somewhat nervous about creating a potential hole in the barricades protecting their network. With a little knowledge, we can achieve the relevant access while minimizing the risks.

In this first part, we’re configuring the Secure Shell for asymmetric key logon rather than the generally speaking less secure username/password combination we’re used to.

Continue reading “Securing an Internet accessible server – Part 1”