Monthly Archives: July 2021

The Power of Sample Code

.NET, Architecture, C#, Functional

What is wrong with OOP?

In the culture wars between “Object Oriented Programming” and Functional Programming, you will find proponents of OOP that argue that we are doing fine – why should we change? and proponents of FP that lists a litany of inherent problems with what we are doing today and point to the ways FP solves them. After I once was at an Object Bootcamp with Fred George I believe the two main schools of thought are both wrong. All the problems listed by the FP peeps are correct, but they are not inherent in OOP, actually OOP addresses a few of them, but we are as an industry not doing OOP.

I may feel Fred George is the Messiah, but he is not alone in his views. Greg Young has similar concerns.

Inheritance is not the Big Deal

I am old enough to remember Borland C++ ads from the 90s. It focused a lot on inheritance, and reuse through inheritance became the USP for object oriented languages.

As soon as you have written some code though, you realise inheritance is the worst, as it creates undue coupling, making changes very hard to implement.

When Borland made those ads about how Porsche Turbo inherited the Carrera but implemented a big fat rear wing, they had begun their foray into C++ because it offered a way to handle the substantial boilerplate involved in writing a program in Windows. It was relatively straightforward to implement the basics and create a usable abstraction on top of the raw Windows API that made the developer experience much more pleasant.

As visual designers became a thing, they wanted a way to map properties with code, so that UI components (those things implemented as objects we mentioned above) could be manipulated by a developer in design mode. “Property” setters, basically syntactic sugar disguising normal functions, allowed the UI designers to read settings from the object, and replace them with what the developer types in. With this work, Borland and Microsoft were working to catch up with InterfaceBuilder from NeXT Computer (the same thing that lives on today in the Apple MacOS/iOS SDK) that had bolted a different type system on top of C and called it Objective C – but that had a world leading visual designer at the time. Anyway, I think they were in a hurry and didn’t think things through.

Approaches to deal with big programs

In a large codebase, the big problem is achieving low coupling but high cohesion. This means, you want all the code that belongs together to live together but you don’t want to have to make changes in seemingly unrelated code to modify a piece of functionality.

In large problems of old, you could call any subroutine from anywhere else, and many resources were shared, meaning between the time you set a value in a variable and you read from it, some piece of code in between could have modified the value, and you would not be automatically able to know where this access is made and how to prevent it.

In FP, we use modules for scoping, meaning you group functions into modules to aid readability, but the key concept, the Big Idea is immutability. After a value is created, it exists globally, but since they are read-only once created, the drawbacks of global state go away. There is no way to change something that somebody else relies on. You can transform it into a new thing that you need, but the original value hangs around until it’s no longer needed. It is harder to accidentally break other code with changes you are making

The Big Idea in Object oriented development is Encapsulation. You put the data with the code and manipulate abstractions. This means that if you get your abstractions right, you can change or replace these abstractions without needing to make sweeping changes in the codebase.

The original concept of object orientation relied on independent small sub programs that communicated by message passing, implicitly imagining like an “in tray” of messages that the object could process at its own pace and then send a response when the work was completed. However – objects were in C++, Java and C# was implemented as special dynamically allocated structs to which you made function calls, i e they became decidedly more synchronous than they were in Smalltalk or Simula. You would recognise Erlang Processes and Actors as looking more like OG objects. You also see that what made objects useful were that they shared properties we today associate with the term micro services, but on a smaller scale.

So what’s the problem, and what’s up with the title of this blog post?

Java, and C# arguably even more so, took the Big Idea and tossed it out the window. Property Get/Property Set to support novelties like graphical designers and visual components are a clear violation of encapsulation. Why are we letting objects access data that lives in other objects? The need to do that is a huge red flag that your model is incorrect. Both the bible, i.e. Refactoring, by Fowler and the actual Bible condemn this, this feature envy.

But why did these properties survive the nineties and live on into modern day? Why have they made things worse with auto properties?

Sample code

When you learn a new language, or to code in general, the main threshold is getting to the point where you write idiomatic code in that language. I e you use familiar phrases. You indent the code in a certain way, you name things according to a certain standard and you use familiar ways to do things like open a database connection, make a HTTP request et c, that a seasoned programmer would be familiar with. Unfortunately- in C# at least, these antipatterns are canon at this point, so to write properly encapsulated code would maybe cause a casual reviewer to ask WTF and be sceptical.

What is canon comes from the publicly available body of work that a beginner can reasonably access. Meaning, effectively Microsoft sets the bar when they announce features, document them and create samples.

There are some issues here. If you look at a large piece of sample code, you may notice how difficult it is to identify the key concept being demoed as the logging code or error handling bulk up the code in a way that is distracting, so brevity must be allowed to remain a priority, clearly.

At the edges where the code starts interacting with network and storage, this type of organisation isn’t inherently despicable either, so a blanket ban is perhaps not the way forward either.

How do we make it clear to new OO devs that when they fill that empty Models folder their project template creates for them with code they would be better off thinking OO proper?

By that I mean making classes that are extremely small, use value objects, prefer private fields, avoid properties et cetera. My suspicion is that any attempt at conveying this programming style through the medium of sample code in templates or documentation is doomed. The bulk of code necessary to not only prove the concept but to in fact make it part of the vernacular would require a large number of people making quite a lot of good code public do that new learners can assimilate the knowledge.

I think good OO code is scarce. Getting the abstractions right is just too hard, you will have compromises in various places, and all the tools tempt you with ways to stray from the narrow path of righteousness, but with modern refactoring tools you should be able to address some of the issues amd continually strive to make the code better.

Incidentally, with properly sized objects you can unit test without cheating (using internal helper methods, or by using mocks), so there is scope to brighten up the tests as well.

Automation and security

Architecture, DevOps

There is a recent spate of sophisticated attacks on software delivery mechanisms where cyber criminals have had massive success in breaching one organisation to get automatic access to hundreds of thousands of other organisations through the update mechanism the breaches organisation provides.

Must consider security at design time

I think it needs reiterating that security needs to be built in by default, from the beginning. I haven’t gone back to check properly, but I know I went back and deleted an old blog post because it had some dubious security practice in it. My new policy is, I would rather omit some part of a process than show a dodgy sample. There are so many blog posts you find if you search for “login form asp.net” that don’t even hash passwords. And rather than point beginners to the built-in password hashing algorithms that are available in .NET, and the two lines of code you have to write, they leave some beginners thinking it’s all right, just this once and breed this basic idea that security is optional. Something you test for afterwards if you are building something “important” and not something you think about all the time.

The thing is, we developers have tools that help us do complicated things – like break bits of code out from other bits of code automatically or rename specific constructs by a certain name, including surrounding text comments, without also incorrectly renaming unrelated constructs that share name.

It turns out cyber criminals too have plenty of automation that helps them spend very little effort breaking in to companies, and exploit this access in a number of different ways.

There is maybe no “why”

This has a couple of implications. First off, attackers are probably not looking for you per se. You may be a nobody, you will still be exposed to automated attacks that test your network for known vulnerabilities and apply automated suites of exploits to see what happens. This means that even if you don’t do anything that conceivably could have value to an attacker, you will still be probed.

The second thing is, to prevent data loss you need to make every step the attacker has to take a hardship. Don’t advertise what software versions your public facing servers are running, don’t let service accounts have access to things beyond what they need, do divide networks into segments so that – for example – one machine with ransomware cannot directly infect your entire network.

Defend in depth

Change any business processes that require people to open e-mail attachments as part of their job. Offer services that help people do their job in a more convenient way that is also more secure. You cannot berate people for attempting to do their job. I mean, you can but it is not helpful.

Move backups off site and offline of course, for many reasons. But, do remember that having to recover a massive storage system from a backup can still be an extinction level event for a business even if you do have a working reliable off site backup solution. If you lose a large SAN you may be offline for days, and people will not be able to work, you may need to bring sites offline while storage recovers. When you procure a sophisticated storage solution, do not forget to design a recovery strategy ahead of time for how to rebuild a massive spinning rust storage array from absolute zero while new data is continuously generated. It is a non-trivial design challenge that probably needs tailoring to how your business operates. The point is, avoiding the situation where you need to actually restore your entire storage from tapes is always best.

Next level

Despite the intro, I have so far only mentioned things that any company needs to think about. There are of course organisations that are actually targeted. Financial institutions, large e-retailers or software supply chain companies run a greater risk of being manually targeted by evildoers.

Updates

Designing a secure process for delivering software updates is not trivial, I am not in any position to give direct advice beyond suggesting that if you are intending to do that, to consider from the beginning how to track vulnerabilities but also how to effectively remove versions that have been flagged as actively harmful, and how to support your users if they have deployed something dodgy. If that day comes, you need to at least be able to help your users. It will still be awful, but if you treat your users right, you might still make it.

Humans

Your people will be exploited. Every company that has an army of customer service representatives will need to make a trade-off between customer convenience and security. Attacks on customer service reps are very common. If you have high-value clients, people will use you to get to your clients’ money. There is nothing to say here, other than obviously you will be working with relevant authorities and regulatory bodies, as well as fine tune your authentication process so that you ask for confirmation information that is not readily available to an attacker.

Insiders

I don’t have any numbers on this, so I am unsure how big of a problem this is, but it is mentioned often in security. Basically, humans can be exploited in a different way. Employees can be coerced through intimidation, blackmail or bribery to act maliciously on behalf of an attacker. My suspicion is that this is less common than employers think, and that times when an employee was stressed or distracted and fell for a phishing e-mail, the employer would think “that is too obvious of a phish, this guy must have been in on it”.

It makes me think of that one time when a systemic failure on multiple levels meant that a cleaner accidentally started a commuter train that ran from the depot the length of the commuter railway Saltsjöbanan – at maximum speed – eventually crashing through the buffers and into a building at the terminus. In addition to her injuries, she suffered the headlines “train stolen and crashed” until the investigation revealed the shocking institutional failings that had made this accident possible. I can’t remember all of them but there were things from the practices in how cleaners accessed the trains, how safety controls were disabled as a matter of course, how trains were stabled, the fact that points were left set so that a runaway train would actually leave the depot. A shambles. Yet the first reaction from the employer was to blame the cleaner.

Anyway, to return to the matter at hand – yes, although I cannot speculate on the prevalence it is a risk. Presumably, if you hire right and look after your people you can get them to come to you if they have messed up and gotten themselves into a compromised situations where they are being blackmailed or if somebody is leaning on them. Breeding a strong culture of fear can be counterproductive here – i.e. let people think that you will help them rather than fire them and litigate as long as they voluntarily come forward. If you are working in a regulated industry, things are complicated further by law enforcement in various jurisdictions.

The Powershell and the Glory

.NET

In which I add a custom prompt by making a hack in the PowerShell profile.

As I have mentioned in previous posts, I use Oh My Posh to set the theme in Powershell. While working with Pulumi to create deployment stacks, I thought I could use a way to see which stack is the current one, i.e. to effectively have the output of pulumi stack --show-name appear in the prompt automatically.

Back in the old world, the agnoster theme was the prettiest. In my terminal at least, it looked quite a lot worse after upgrading to Oh-My-Posh 3, so I did exactly what they say in the documentation, I used Get-PoshThemes to look at all of them, exported the one I liked best into a json file and went to work.

Command

The naïve implementation would be to add a new segment in the prompt, using the segment type seemed to be “command”, which does what it says on the tin, it allows you to call a command and display the output, like it works in Bash.

        {
          "type": "command",
          "style": "powerline",
          "foreground": "#000000",
          "background": "#ffff00",
          "properties": {
            "shell": "powershell",
            "command": "pulumi stack --show-name"
          }
        },

They do warn you that there will be performance implications, and – yes- on my 16 core desktop it still takes forever to start a process in PowerShell, so that didn’t seem to be a workable way forward. The suggested approach is to “abuse environment variables”, so… let’s?

Environment variable

I have previously made hacks to set window titles in cmder to work around iffy built-in support for showing the path as the tab name. The idea was to replace the built-in “cd” alias with a PowerShell function that also does dodgy stuff on the side apart from changing directory. In this case I would test if a pulumi.yaml file exists in the new directory, and in that case set the variable PULUMI_STACK to the output of pulumi stack --show-name, or set the variable to empty.

# --- other stuff
function Change-Directory() {
    param(
        [string]
        $directory
    )
    Set-Location $directory
    $env:PULUMI_STACK = ""
    if (Test-Path "pulumi.yaml") {
        $env:PULUMI_STACK = & pulumi stack --show-name
    }
}
# --- other stuff
Set-Alias -name cd -Value Change-Directory -Option AllScope

I of course don’t want to globally change this variable, I explicitly only care about the current terminal session, so hence I’m not trying to update the registry or anything like that. To read this variable and show a prompt, we then modify the theme json file to leverage the envvar block and to contain the following: 

{
    "type": "envvar",
    "style": "powerline",
    "foreground": "#000000",
    "background": "#ffff00",
    "properties": {
       "var_name": "PULUMI_STACK"
    }
},

After this work, the prompt is much faster, beyond acceptable, maybe even pleasant.