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On Infrastructure as Code and Bit Rot

The architecture of the infrastructure-as-code (IaC) tooling you use will determine the level to which your IaC definitions are exposed to bit rot.

This is a maxim I have arrived at after working with multiple IaC tool sets, both professionally and personally, over the last few years. In this blog post, I will explain how I arrived at this maxim by describing three architectural patterns for IaC tools, each with differing levels of risk for bit rot.

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AWS CLIv2 on OpenBSD

The AWS CLI is a tool set that lets you manage your AWS resources. The CLI comes in two versions which, at the time of this writing, are developed concurrently: version 1 and version 2.

Internally, the AWS CLIv1 and v2 are quite different. Version 2 pulls in AWS libraries--libraries which are used across the AWS SDK ecosystem--rather than reinventing the wheel when it comes to common tasks, such as talking to Amazon S3. Running AWS CLIv2 on your operating system of choice requires building and installing these common AWS libraries.

I contributed changes to s2n-tls, aws-lc, the Python runtime, some build tooling, and various other libraries. As a result, the AWS CLIv2 now builds and runs on OpenBSD.

To make installation simple, I've created an OpenBSD port for CLIv2 and its dependencies. Instructions for installing the port are below.

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Software Is Everywhere

"Software is eating the world." Have truer words ever been spoken other than these words by Marc Andreessen?

I've recently been immersed in a number of home automation projects (lights, heating/cooling, presence detection, and more). I was reflecting on what made all of these automations possible: the drastic increase in the amount of software present in the home. As I was reflecting on this, I realized how different my house is in this respect compared to the house I grew up in.

Now, I'm not saying I'm old. More like, the rate of digitization in the world around us has happened at such a pace that even in my short lifetime, the changes have been deep and wide.

This blog post is a tour of things in my house that are software operated that were not software operated in the house I grew up in. For my purposes here, I define "software operated" as any device that has software or firmware that is upgradable either by me or through an over-the-air process that the device or its cloud service initiates. I'm leaving out "obvious" items like laptops, tablets, and mobile phones.

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Amazon EC2 Credential Exfiltration: How It Happens and How to Mitigate It

An introduction to Amazon EC2 credentials

When you assign an Identity and Access Management (IAM) role to an Amazon Elastic Compute Cloud (EC2) instance, the short-term credentials for the role are made available via a web service known as the Instance Metadata Service (IMDS). The IMDS provides an HTTP endpoint for retrieving instance metadata such as the instance IP address, AWS Region the instance is running in, the Amazon Machine Image used to launch the instance, and the access key, secret access key, and session token associated with the instance's IAM role. The AWS documentation describes how to retrieve instance role credentials from IMDS. If you've seen or used the or http://fd00:ec2::254 endpoints, then you've seen/used IMDS.

Retrieval of instance role credentials from IMDS is the mechanism by which the AWS CLI and SDKs learn the credentials belonging to the instance's IAM role without you having to configure anything on the instance. Quoting the IAM documentation:

The AWS SDKs, AWS CLI, and Tools for Windows PowerShell automatically get the credentials from the EC2 Instance Metadata Service (IMDS) and use them.

This is great! It means you can start using the AWS CLI, SDKs, or Tools Continue reading

Roomba Stuck at ‘Verify password’

You have:

  1. A Roomba vacuum. (I was working with an i-series when I wrote this. Maybe this applies to other models as well.)
  2. A firewall or router between your Roomba and your mobile device. (Maybe the two are on different wifi networks as would be the case if you have a network set aside for IoT devices.)
  3. An iRobot app that gets stuck at Verify password when setting up the Roomba.

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How I Migrated from MediaWiki to Notion

I've written before about how I use MediaWiki for taking notes and as one of my study tools. This has worked well for many years. But a problem started to develop: while I wrote my technical notes in MediaWiki, I wrote my day-to-day notes (books I want to read, notes from podcasts I listen to, and even my weekly planner) in Notion. This meant I had to use different apps for reading/writing in each tool, remember two different markup languages, and couldn't (cleanly) link pieces of content between the two. The final straw was realizing how much more effort I had to expend to maintain my MediaWiki instance; I just didn't have the time or will to keep up with new releases not to mention maintain the server itself.

For these reasons, I decided to move all of my MediaWiki content to Notion and unify all of my notes. But this revealed a new problem: there was no tooling to automate this. So I created my own. Here's how it works.

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Monitoring a Multi-Inverter SolarEdge System

Monitoring a Multi-Inverter SolarEdge System

A friend of mine recently had a solar panel system installed on his acreage. Besides being interesting because of the renewable/green aspect of the project, the system itself—from SolarEdge—is actually highly digital.

  • A mobile app is used for commissioning the system.
  • SolarEdge operates a cloud service which collects telemetry from the system and reports various performance metrics in a user-friendly dashboard.
  • The inverters can connect to the IP network and provide a means to collect telemetry from them directly.

The last point interested me the most because any time a device exposes its data or a control connection, it means there’s an opportunity to integrate it with other software. In this case, I wanted to create my own dashboard to display (near) real-time performance data for the system.

Whereas other blogs and articles on this topic describe how to monitor a single inverter system, this post will describe how I built a performance dashboard for a multi-inverter system.

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Operating Sonos Speakers in a Multi-VLAN Network

In a throwback to the problems I dealt with using AirPlay across VLANs, I recently jumped through similar hoops for Sonos speakers. There are many forum and blog posts out there that describe (or attempt to describe) how to make this work, however all of the ones I read suffered from one or both of these problems:

  1. Their instructions had errors (eg, reversing the upstream and downstream interfaces when talking about multicast).
  2. They don't have a digram of traffic flow! Every network engineer knows that a diagram is a must when trying to understand how two systems are talking to each other.

This post will dive deep on what's happening on the wire when a Sonos controller (eg, your mobile phone running the Sonos app) tries to talk with the players (the speakers) on the network. The focus will be how to make this process work when those two devices are in different VLANs.

What you read below works successfully with Sonos Beam, Sonos Sub, and Sonos Move using the Sonos S1 app.

AWS Cloud Development Kit: Now I Get It

The AWS Cloud Development Kit (CDK) is an "open source software development framework to define your cloud application resources using familiar programming languages". When CDK launched in 2019, I remember reading the announcement and thinking, "Ok, AWS wants their own Terraform-esque tool. No surprise given how popular Terraform is." Months later, my friend and colleague Matt M. was telling me how he was using CDK in a project he was working on and how crazy cool it was.

I finally decided to give CDK a go for one of my projects. Here is what I discovered.

How to Implement the Principle of Least Privilege With CloudFormation StackSets

This article was originally posted on the Amazon Web Services Security Blog.

AWS CloudFormation is a service that lets you create a collection of related Amazon Web Services and third-party resources and provision them in an orderly and predictable fashion. A typical access control pattern is to delegate permissions for users to interact with CloudFormation and remove or limit their permissions to provision resources directly. You can grant the AWS CloudFormation service permission to create resources by creating a role that the user passes to CloudFormation when a stack or stack set is created. This can be used to ensure that only pre-authorized services and resources are provisioned in your AWS account. In this post, I show you how to conform to the principle of least privilege while still allowing users to use CloudFormation to create the resources they need.

My List of Unusual Things in DNS

This is a running list of unusual data found in the Domain Name System.

Typically, DNS stores name-to-IP (for example, -> and IP-to-name mappings (i.e., the inverse). But, the DNS is arguably the biggest, most distributed key/value store on the planet, making it a great place to stash all kinds of simple data.

How I Installed Tasmota Firmware on a Treatlife Switch

For years now I've had a light switch that can be programmed to turn itself on/off on a schedule. The switch is programmed with the date, time, time zone, and lat/long and then you can create a schedule such as, "turn the lights on at sun set". It works pretty well except when 1/ daylight savings time starts or stops (the schedule doesn't adjust itself) or 2/ the power goes out (bye, bye all programming).

This slight annoyance coupled with my desire for a project I could geek out on lead me to look into software-controllable light switches.

In this post I'll explain how I flashed the open source Tasmota firmware onto the Treatlife 3-way wall switch which in the end allowed me to control the lights via a home automation controller.

Converting From AWS SAM to CloudFormation

AWS Serverless Application Model (SAM) is a framework for building serverless applications on AWS. One of the components of SAM is a template specification. SAM templates would look and feel familiar to anyone who has used AWS CloudFormation to define their infrastructure as code, however they are not completely interchangeable. There are multiple reasons why you might want to convert from SAM to native CloudFormation:

  • You want to deploy the app using CloudFormation StackSets. SAM uses the AWS::Serverless transform in its templates and transforms are not supported by stack sets.
  • You want to deploy the app as part of an AWS Landing Zone (ALZ) account baseline. ALZ uses stack sets as the mechanism to deploy baseline resources and so suffers from the same constraint as the point above.
  • Your operating system of choice isn't documented in the SAM installation instructions and you're uncertain how to install from source or doubtful it will work at all (I'm looking at fellow OpenBSD and FreeBSD users here).

This post will show you how to take an existing SAM application and convert it to a CloudFormation template (CFT). As a CFT, the challenges listed above can be avoided.

Building a Scalable Document Pre-Processing Pipeline

This article was originally posted on the Amazon Web Services Architecture blog.

In a recent customer engagement, Quantiphi, Inc., a member of the Amazon Web Services Partner Network, built a solution capable of pre-processing tens of millions of PDF documents before sending them for inference by a machine learning (ML) model. While the customer's use case--and hence the ML model--was very specific to their needs, the pipeline that does the pre-processing of documents is reusable for a wide array of document processing workloads. This post will walk you through the pre-processing pipeline architecture.

AWS VPC Traffic Mirroring Walkthrough

I was recently playing around with the Traffic Mirroring feature in AWS. As a network geek, this is right up my alley because as some colleagues and I used to say, "the wire never lies!". Being able to pick packets off the wire for detailed inspection has saved the day many a time. Until Traffic Mirroring came along, it wasn't possible to do that in an Amazon VPC. Below are my notes and considerations for using this feature.

Replicating Elastic File System With AWS DataSync

I recently used AWS DataSync as part of a lab I was building. These are my notes for using DataSync to replicate an Amazon Elastic File System (EFS) share from one region to another.

AWS DataSync is a managed service that enables replication of data between AWS services and from on-prem to AWS. It automates the scheduling of transfer activities, validates copied data, and uses a purpose-built network protocol and multi-threaded architecture to achieve very high efficiency on the wire.

The use case I needed to tackle was replicating an Amazon EFS share in one region to an EFS share in a different region (a one-way replication). (DataSync can also connect to Amazon S3 and Amazon FSx for Windows File Server)

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