Following applying the 2020-05 Cumulative Update for Windows Server 2016 (1607), a PFSense 2.4.5 Hyper-V virtual machine on this host OS suddenly became very unstable.
The machine appears to experience high load averages immediately following boot, with a large percentage of the vCPU usage (>99%) being shown as “system” in top.
Additionally, sometimes it is seen that the pfctl process is also using close to 100% of a CPU. The system is unresponsive, or intermittently responsive throughout this time — both in terms of the console, the web UI, and packet forwarding that the machine should be doing.
After a few minutes, Hyper-V appears to restart the guest OS. This isn’t a PFSense kernel panic and no dump is made by PFSense.
I spun up a new VM of the unstable daily snapshot of PFSense, a Generation 2 UEFI-based VM. This completely eliminated these problems for us in this new VM — it works fine, routes just fine for what we’re doing and is responsive.
I don’t have a solution — I just want to throw this issue out there in case others have experienced it, in case we might work together to figure out what’s going on here.
I recently opened an old version of my DfontSplitter C# project in Visual Studio 2019. I expected a process would need to be gone through to upgrade the project from its source version (VS2008 I believe) before it could be opened in Visual Studio 2019. Such a process did happen and it completed without errors.
A little later, I noticed something odd. A folder had appeared at the root of my C: drive with the name xyDQ7sfb+k4aZLT8oSso4yqXRQ=.
Inside, a sqlite3 folder and the usual artifacts that you’d associate with a SQLite database.
At this point of my initial investigation, I hadn’t yet connected my opening of this Visual Studio project with this folder. It looked highly suspicious — a name that apparently was encoded and random.
It contained tables including names like SolutionData2, ProjectData2, StringInfo2. Some investigation of the contents of these led me to this recent VS2008 project I’d opened.
I still felt it looked malicious though — was this something injecting itself into Visual Studio projects I was building?
Tracking down the source(?)
Some web searching later, I’d discovered a part of Roslyn, the C# compiler, which had references to these _SpellChecker_ entries I’d seen in SolutionData2 and the suggestion that this is dumped to persistent storage.
Catching it in the act
So, I deleted the folder from the C drive and replicated the process. I opened the same project again, but this time running Sysinternals Process Monitor in the background, filtering Path for sqlite or this folder name.
We can see calls to CreateFile (which creates a handle to a file — this is usually ‘opening’ the file rather than ‘creating’ it) with the result PATH NOT FOUND. Then, another call to CreateFile (highlighted) that actually creates the directory.
From there, it’s clear that this process, ServiceHub.RoslynCodeAnalysisService32.exe, is responsible for this database and its timing correlated exactly with me upgrading this project from VS2008 to VS2019.
But… what is this? Why?
I posted some Visual Studio Feedback about my observations, although this issue was closed as applying to sqlite, not Visual Studio. I understand that this isn’t high priority, but I disagree with the assessment that the use of SQLite in this case makes it SQLite’s fault!
So I remain curious. Do some code analysis on the solution, sure. But why store results in the root of the C drive? How is the encoded folder’s name decided? Why does this whole thing feel suspicious rather than behaviour I’d expect from an IDE?
And… it’s gone
As of Visual Studio 16.5.3, this appears to be fixed — the same filesystem behaviour by RoslynCodeAnalysisService32 is now prefixed with %LOCALAPPDATA%\Microsoft\VisualStudio\Roslyn\Cache\RemoteWorkspace. I guess it was indeed a bug — an oversight in actually setting the full path to this database properly.
I recently had some success installing OpenWRT 19.07.2 on my TP-Link WA801ND v5 wireless access point, which I was happy to do since the stock firmware was untouched since 2017.
I’ve documented the process in a video. This isn’t a tutorial with absolutely everything covered — I don’t want to encourage people to brick their devices, so you’ll need competence and proficiency with configuring your network settings in your operating system, and running a TFTP server.
It’s all, obviously, at your own risk. Stay safe and don’t brick your only access point!
I’ve been playing with some Raspberry Pi Zero W machines for a few projects. They are inexpensive, with a form factor that makes for all sorts of interesting possibilities.
They are also a pain to initially provision, because you need adapter cables for mini-HDMI and micro-USB to get a monitor and keyboard connected.
With some help from this post from Linuxconfig.org, here’s what I’ve been doing to get the Pi Zero W up and running, on the network and ready for SSH access without having to plug anything in except power and the SD card!
Mount the image
$ fdisk -l *raspbian.img
The initial FAT /boot partition lies at 8192 sectors in. A sector is 512 bytes. So, now we’ll mount the /boot partition using the loop pseudo-device.
Let’s go into our new boot subfolder where the image’s first partition is now mounted.
All we need to do to enable SSH is create an empty file called ssh.
$ cd boot
$ sudo touch ssh
To configure WiFi, we’ll need to drop a wpa-supplicant.conf file in this folder. Upon first boot, Raspbian moves this into the correct config location and the Pi will be able to talk to our network out of the box.
Create a file called wpa-supplicant.conf with these contents:
You’ll need to replace the placeholders with your network name and password, and possibly change country too.
Unmount the image
$ cd ..
$ umount boot
Write the image
Insert the target SD card and verify which device it is using fdisk.
Take great care to ensure that the command below is run with the correct device as the target, or you’ll overwrite a hard drive on your local system.
$ sudo fdisk -l
Disk /dev/sdb ...
Model: Card Reader
I am confident that sdb is correct, because I see from fdisk that the model is Card Reader.
$ sudo dd if=*raspbian.img of=/dev/sdb
Remember that once you’ve booted, you’ve just spun up a Raspberry Pi on your network with the default username of pi and the default password of raspberry. Check your router or network logs for the assigned DHCP address of the new Pi, log in promptly over SSH and change that password!
There is great potential in using open source and free software licensing to support and encourage the ethical use of technology — and indeed to deter its use in violating human rights and provide some legal mechanisms to challenge this when it happens.
But it’s also an extremely complex and difficult issue, as there are always a great number of implications, and they’re not always easy to anticipate.
This is an area I watch with keen interest, and I was interested to read Matthew Garrett posing some interesting questions around how a clause relating to taking away another’s ability to exercise their rights under the licence might work. The idea is taking the moral goal of preventing harm being done to others by means of the software and expressing that goal in terms of prohibiting actions that would prevent others from exercising their rights under the same licence.
This work may not be used in any way that impairs any individual’s ability to exercise the permissions granted by this license, whether or not they have received a copy of the covered work
To be clear, I don’t think this is a good license – it has a bunch of unfortunate consequences like it being impossible to use covered code in self-defence if doing so would impair your attacker’s ability to use the software. I’m not advocating this as a solution to anything. But I am interested in seeing whether the perception of the argument changes when we refocus it on user freedom as opposed to an independent ethical goal.
The idea is that you have Socky listen on target ports, and any connection attempts that come in to those target ports will fire a user notification at the top right of your screen (that’s the job of SockyNotifier — to show those notifications).
Note: that this is not particularly serious or practical, but I wanted a project that let me work directly with the Core Foundation APIs in C, and this seemed a good opportunity.
It’s a lightweight application designed to run in the background, detecting if the computer is idle (based on keyboard or mouse movement) and presenting a timed warning that the computer will be locked. It then locks the computer if it is still idle once the grace period expires.
It is functional, but its real world usability isn’t there yet — it’s not going to be usable in practice if it isn’t aware of things like playing back video, presentations and other states that are not idle, but don’t involve user input for longer periods of time. It isn’t aware of those things at the time of writing!
However, it has been an enjoyable and informative further exploration of working with the Win32 API directly.
I found myself drawn to working in C/Win32 for this application and its predecessor — the result here is less than 50 KiB in size and uses about 1.4 MiB of RAM (Private Bytes). Any similar application you would create in .NET, for example, would be an order of magnitude more demanding in terms of resources, just because of the nature of the framework.
Here’s an explanation of how it works:
It accepts two command line arguments — the number of seconds before displaying the warning window and the number of grace period seconds while that window is open.
It measures the number of GetTickCount64 ticks taken for a SetTimer with 1000 ms to be fired. This is used to calculate idle periods and grace periods in terms of ticks.
It sets up two SetWindowsHookEx hooks — one for keyboard activity and one for the mouse. These yield execution some of the time to avoid performance issues from the frequency with which they are called. These update our last interaction tick number to indicate the computer is in use.
Every ten seconds, a SetTimer-based timer calls a function which evaluates if we’ve reached the idle condition. If so, the warning dialogue is displayed.
The warning dialogue counts down the grace period with the progress bar and another SetTimer callback. Upon expiry, LockWorkStation is called to lock the computer.
The WM_WTSSESSION_CHANGE window event is listened for — we take notice of WTS_SESSION_LOCK and UNLOCK events to ensure that we don’t try to detect idle conditions if the screen is already locked, and that when unlocked, any previous idle period is reset.
Learning about how Windows operates at a lower-level — windows, window messages and some of the more primitive operations has been illuminating! This is the perfect bi(y)te-sized project to help me move forward with learning about this!
I recently completed my rewrite of DfontSplitter for Mac, my tool for converting Mac-formatted Dfont, Font Suitcase and TTC font files into TTF files.
This new version is written in Swift, targets macOS Mojave (10.14) and later and meets all the requirements that soon will be required of Mac software (code signing, notarisation/delivery via Mac App Store).
The “T with chisel” DfontSplitter icon is licensed under the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. The icon includes a modified version of “Chisel wood 24mm” by Isabelle Grosjean, which is also licensed as such.
Keeping an eye on failed logins and the user accounts that are being targeted is an important part of being responsible for an Office 365/Azure Active Directory tenant.
If you can afford the higher-level O365/Azure AD plans, there are great tools built in to the Azure Portal that allow useful intelligence into your security posture.
For The Rest of Us(tm), we sometimes need to be a little creative to gather the information needed. For on-premises Active Directory Federation Services (ADFS) servers, I put together a simple, quick and, perhaps slightly hacky script to extract the usernames from recent failed login events from the Windows Event Log and dump them, along with the rest of the Windows Event, to a CSV file for later analysis.
This specifically searches event logs from the past 12 hours (43200000 milliseconds in the $query).
Installing the Remote System Administration Tools on a Windows 10 1903 system that uses System Center Configuration Manager to receive Windows updates seems to be challenging. The process of pulling the RSAT bits down from Windows Update in my experience was not succeeding – perhaps because the SCCM WSUS instance did not have them.
The CBS.log showed:
CBS Exec: Failed to download FOD from WU, retry onece. [HRESULT = 0x800f0954 - CBS_E_INVALID_WINDOWS_UPDATE_COUNT_WSUS]
Some solutions online seemed to suggest temporarily switching the Windows Update source in the registry to Windows Update (online) rather than WSUS, but editing the registry this way and upsetting the software update system seemed… unwise.
I ended up doing it a different way: downloading the Features on Demand DVD ISO from the Volume Licensing Service Center (in my case, SW_DVD9_NTRL_Win_10_1903_64Bit_MultiLang_FOD_1_X22-01658.ISO), mounting the ISO and using this modified version of Martin Bengtsson’s script to install the components from that ISO without contacting Windows Update.