Two days ago I set up a new virtual machine for applications that require isolated security. When I put my computer into Connected Standby mode, I noticed SoC fan didn’t stop. To verify whether it was OS inconsistency or persistent issue, I manually initiated a system restart. However, it froze at login screen then. Nothing responded, including Ctrl + Alt + Delete key sequence. Attempting to force shutdown and start the computer almost didn’t improve the situation. After about ten attempts I managed to enter my desktop. There was no clue in event viewer: everything went well then suddenly the system froze.
I remembered that an alternative OS loader entry was configured to bypass Hypervisor launch at startup. I selected this entry to see whether it was related to Hyper-V. Test results indicated the freeze issue was strongly related to Hyper-V.
I tried to remember what I did before virtual machine configuration. I removed a virtual switch bridged to Surface Ethernet Adapter on my Surface Dock, then added a virtual switch bridged to VMware NAT adapter (which works better with Wireless network). Then I checked adapters in Network and Sharing Center, the old virtual switch didn’t get removed at all – and the “Remove” menu entry was unavailable. At last, I removed this adapter from Device Manager, and the issue was resolved.
This issue is likely related to OS inconsistency. When Hyper-V infrastructure attempts to initialize (bring up) all enabled network adapters including these Hyper-V virtual switches, the “removed” adapter is brought up, then enters failure state due to inconsistency in configuration. Because host operating system is a virtual machine on Hyper-V (with privileges), the host OS didn’t even get a chance to record what happened at that point.
The good thing is that I fixed it by myself; The bad thing is I missed an opportunity to report this bug and let Microsoft fix it.
Previously my openconnect server deployment plan utilizes PAM authentication (via Kerberos/Active Directory) as the primary authentication method. It works but it’s complicated (password every time). I just enabled certificate authentication today and it worked fine.
Things to note
Enable certificate authentication as an alternative authentication method (up to you, but some guys in our domain don’t use certificate-capable device)
Use “Smartcard Logon” certificate template with subject information in “Common Name” style
Set OID 184.108.40.206 as user identifier in openconnect server configuration
Provision root CA, CRL and OCSP (CRL and OCSP are optional but essential as part of the best-practice)
I provisioned the same certificate in my Yubikey PIV and TPM-based virtual smartcard, but neither works for AnyConnect client. Certificate in user certificate store is fine.
A short update: The recent MSDN subscription migration kills my migrated account alias too. After contacting Microsoft support, I removed legacy alias from my account, create a new Microsoft Account using my legacy alias and restored my access to the new Visual Studio Subscription portal. In the same way, I removed legacy Microsoft Account in my Azure AD, linked two separated Microsoft Accounts(legacy and new alias) and resolved my issue accessing Visual Studio Team Services.
Such inconsistency always happens, and usually remove & add will be the universal solution in most cases.
After using legacy alias for almost 7 years, I decided to replace my Microsoft Account alias with a new Outlook.com email address due to increasing security concern of Netease Mail (my previous email service provider). Though I changed alternative recovery email to my domain email after several major security incidents, it looks weird to have an @163.com email alias linked to my Microsoft account.
Okay, I changed my alias the day before yesterday. It works. I didn’t delete the old one because I want to maintain some sort of backward compatibility. It works across my personal devices without any pain.
Annoying things came afterward days later.
Let’s talk about SSO/Federated Logon
Before talking about terrible things after switching to the new alias, let’s talk about Federated Logon. Technically speaking, Federated login is an authentication workflow based on trust relationships. Suppose Identity Provider A and Application B have successfully established two-way trust relationship by service provision. When a new user login attempt occurs, B redirects authentication challenges to Identity Provider A, with necessary metadata, like secure token ID, timestamp, nonce and finally something that validates the request, for example, digital signature, even token encryption. Since Application B has its own approach to understand Identity Provider A’s payload(so does B), the communication will be secured.
When Identity Provider A completes user authentication challenges(password, client certificate, fingerprint, etc.), it signs (encrypts maybe) authenticated user claims (user ID, user name and something else) and posts to B. The workflow image of WS-Federation below represents such workflow. OAuth and OpenID Connect have similar workflow with slight differences(multiple modes to retrieve user claims).
Microsoft Azure, Visual Studio Team Services and most Microsoft services use OpenID Connect. Believe it or not, you use Federated Logon and SSO every day.
Microsoft Account and Azure AD Account
They are two separated systems though they have something in common. Each Microsoft Account has a CID, a unique identifier in Microsoft Account system. All Microsoft Consumer services use CID to recognize your identity. For example, your Outlook.com email account is identified using your CID.
Azure AD Account handles it differently. Each Azure Active Directory have a tenant ID to identify AAD in AAD system. Each AAD contains objects: users, groups, computers, trust relationships….and more. Each AAD user has a unique alias in a specific AAD tenant. So the coexistence of 2ea6c0b4-cc49-42b8-9f1b-3f4aa653c719\imbushuo and b5093785-af31-4819-bf75-728d4474769c\imbushuo is possible.
Microsoft Accounts can be linked into Azure AD too: during the linking procedure, a new external user from Microsoft Account will be created in an AAD tenant, so you may have 2ea6c0b4-cc49-42b8-9f1b-3f4aa653c719\email@example.com. When Bill wants to access resources in his tenant’s AAD, he will type firstname.lastname@example.org in AAD Federation Service(Work and school account), a single sign on portal for Azure AD. Later, AAD FS will redirects the authentication challenges to Microsoft Account login portal. If Bill is authenticated in Microsoft Account login portal, he will be redirected back to AAD FS, with claims provided by Microsoft Account. Finally, AAD FS will tell the application that the user is Bill.
My blog uses such login mechanism too. See my management portal to get some idea about this if you don’t understand.
But…there’s no CID in Azure AD
But there’s something just works like CID: user alias. Another mapping! Microsoft Account will be mapped to Azure AD account, then the application will use the Azure AD account identity. After changing my alias in Microsoft Account, my Azure AD user alias remains the same. So I can login into my blog management portal with the same identity:
Do you remember that federation logon can carry multiple attributes at one time? So here’s the problem. My team’s source control service, Visual Studio Team Services, seems to use email address (which changes after rotating my primary Microsoft Account alias) to identity user. After logging in with my organization account, I found that my email address didn’t change after the rotation. To make the whole thing worse, I am the account creator, hence I cannot remove my Microsoft Account in VSTS to address the issue.
In short, the primary alias rotation didn’t change my user alias in Azure AD, but applications’ behavior vary based on how they deal with user claims.
This step is absolutely easy on Ubuntu/Debian and other officially supported distributions. If you are using Archlinux, go to AUR for .NET Core runtime.
Step 2: Prepare files.
In local Visual Studio or other development environment, publish project to a folder. (dotnet build -c Release)
Step 3: Setting services
I wrote a simple systemd service for my application:
Description=A certain ASP.NET Core application
ExecStart=/usr/bin/dotnet /opt/imbushuo/somepath/App.dll --server.urls=http://localhost:5050
Step 4: Setting up reverse proxy
Refer to your frontend server documentation for details.
If you are using per-environment configuration file, make sure the configuration starts with capital letter, like appsettings.Production.json . Otherwise, the Startup class will not load the settings file.
If you want to run multiple applications, make sure add configuration class in Program class and apply it. Then, pass server.urls parameter with address and port, like what I wrote above.
The following Program.cs has been modified to enable parameter support. Feel free to copy it:
public class Program
public static void Main(string args)
var configuration = new ConfigurationBuilder()
var host = new WebHostBuilder()
Since I set up Active Directory & Azure Active Directory for my workgroup and myself, I decided to switch to SSO for my web services. I chose Auth0 as the WordPress Identity Middleware as it is pretty flexible. However, the log out function, doesn’t work properly on federated logons. It will just call auth0 to sign out instead of signing out of all IdPs.
Luckily, fixing that is pretty easy. Located to lib/WP_Auth0_LoginManager.php and find the logout function:
If you don’t see federated after logout, fix it. They have fixed it on GitHub, but I don’t know why they don’t push it to WordPress release.
I purchased a Qualcomm DragonBoard 410c for some specific purpose (generally, for fun). All DragonBoard 410c ship with Android, but I want Windows IoT and UEFI so I flashed it.
Well, you can boot Windows RT 8.1 on it, as long as you got critical HAL extensions. But the most important one, USB controller, is not available on DragonBoard 410c. It utilizes USB Role Switch, which is officially supported in Windows 10, not in Windows 8.1. I posted how to boot Windows RT 8.1 installation disk on XDA Developers forum, if you are interested in that, please search it.
Note: USB will not be a problem for DragonBoard 800 because Snapdragon 800 has more than one USB channel, while Snapdragon 410 has only one USB channel.
I think there’s something weird with the internal EFI shell. It seems that all GOP operations will let the firmware hang, however, you can run EFI applications with GOP in the internal EBL(yet another lightweight EFI shell). What’s more, if you boot any Windows OS releases from EFI shell, it will crash during HAL initialization. Such situation doesn’t exist on any Qualcomm-based Windows Phones (MSM8960), so I believe it is a bug specific to 410c’s firmware.
All ACPI-related files, including boot logo, is stored in a small hidden FAT16 partition called PLAT. You can replace files – but I haven’t tested customized ACPI DSDT table. Maybe we can let USB controller work by removing device URS0 and expose device USB0 to root.
GRUB-EFI (ARMHF) works on Qemu emulator, but it will hang on 410c’s firmware. I haven’t got a USB UART cable yet, so I didn’t know what happened.