The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Difficult programming concepts explained in tweets

Posted by jpluimers on 2021/10/20

Highlights from the thread [] Tomasz Łakomy on Twitter: “What’s the most difficult programming concept you can explain in a tweet?”

Finally a cheat (as it has an image), but great illustration:

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Posted in Development, SocialMedia, Software Development, Twitter | Leave a Comment »

Filippo Valsorda on Twitter: “ , the SSH server that knows who you are … Try it out! $ ssh”

Posted by jpluimers on 2021/10/20

[] Filippo Valsorda on Twitter: “ , the SSH server that knows who you are, got some newly refreshed intel! Try it out! $ ssh

The server itself has some HTML with information too redirecting to [WayBack] ssh (source code is at [WayBack] GitHub – FiloSottile/ A ssh server that knows who you are. $ ssh

It’s a cool open source server written in Golang, that gets all your public ssh keys (ssh automatically transmits those) and tries to map them back to a GitHub account.

In addition it shows you some potential vulnerabilities of your ssh client.

Note that in October 2020, it was temporarily down, but it will be up again: [] Filippo Valsorda 💉💉 on Twitter: “Yeah I’m planning to but I can’t give you an ETA I’m afraid. A few weeks, maybe?… “

Thread comments

Some interesting comments in the thread:

Related: [WayBack] Auditing GitHub users’ SSH key quality

Stop presenting public keys

[WayBack] GitHub – FiloSottile/ A ssh server that knows who you are. $ ssh How do I stop passing public keys

How do I stop it?

If this behavior is problematic for you, you can tell ssh not to present your public keys to the server by default.

Add these lines at the end of your ~/.ssh/config (after other “Host” directives)

Host *
    PubkeyAuthentication no
    IdentitiesOnly yes

And then specify what keys should be used for each host

    PubkeyAuthentication yes
    IdentityFile ~/.ssh/id_rsa
    # IdentitiesOnly yes # Enable ssh-agent (PKCS11 etc.) keys

If you want you can use different keys so that they can’t be linked together

    PubkeyAuthentication yes
    IdentityFile ~/.ssh/github_id_rsa


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Posted in *nix, *nix-tools, Communications Development, Development, Go (golang), Internet protocol suite, Power User, Software Development, SSH, ssh/sshd, TCP | Leave a Comment »

The hard part of a crypto specification: make it safe and misuse resistant.

Posted by jpluimers on 2021/10/19

Great quote from a while back:

[WayBack] Filippo Valsorda on Twitter: “Here’s a secret: it’s not that hard to put together a crypto specification. What’s hard is to make it safe and misuse resistant. What needs to be “battle tested” is the security devex, not the narrow happy path, and blaming the developer when it breaks is not battle testing.”

From the same thread:


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Posted in Development, Power User, Security, Software Development | Leave a Comment »

VMware ESXi has 2 bootbanks; with some luck the second contains your old ESXi version

Posted by jpluimers on 2021/10/19

Just in case I ever need this again:

  • [Wayback] VMware Knowledge Base: Reverting to a previous version of ESXi (1033604)
    1. In the console screen of the ESXi host, press Ctrl+Alt+F2 to see the Direct Console User Interface (DCUI) screen.
    2. Press F12 to view the shutdown options for the ESXi host.
    3. Press F11 to reboot.
    4. When the Hypervisor progress bar starts loading, press Shift+R. You will see the warning:
      Current hypervisor will permanently be replaced
      with build: X.X.X-XXXXXX. Are you sure? [y/n]
    5. Press Y to roll back the build.
    6. Press Enter to boot.
  • [Wayback] Downgrade ESXi 6.5 from update 3 to update 2 – VMware Technology Network VMTN; when out of luck:
    • This is not my case.As I mentioned, I don’t have altbootbank with update 2. This is because after update 3, I also installed the latest patch.So both bootbanks now have update 3.Is there any other option for me. Can I just install update 2 again so it will overwrite everything? Or it is impossible?
    • Backup ESXi configurations and reinstall it without overwriting VMFS.

Via: [Wayback/] downgrade esxi 6.5 u3 to u2 – Google Search


Posted in ESXi6, ESXi6.5, ESXi6.7, ESXi7, Power User, Virtualization, VMware, VMware ESXi | Leave a Comment »

EProgrammerNotFound exception in Delphi? – Stack Overflow

Posted by jpluimers on 2021/10/19

From a long while my answer to [WayBack] EProgrammerNotFound exception in Delphi? – Stack Overflow (I added the WayBack links)

It was introduced in Delphi 2009, still present in Delphi 2010, and [WayBack] recently got some [WayBackmore attention on the [WayBackinternet.

I think it is an easter egg, similar to [WayBack] “EBCAK” (Error Between Chair and Keyboard), and the [WayBack] skipping of Delphi version number 13.

[WayBack] EProgrammerNotFound

  • is declared in the Win32 branch of the SysUtils unit, but not used anywhere in the RTL or VCL
  • is not present in Delphi Prism
  • was introduced in Delphi 2009, so not present in VCL.NET
  • has currently (version 3.5) nothing similar in the .NET framework (not sure why, these guys [WayBack] do have humour)

I don’t think EProgrammerNotFound is actually meant to be used at all, but since it is there, people will jokingly use it (similar like putting a stray “const False = True; True = not False;” in someone elses sourcecode).

On green bits and red bits (which I highly associate with the “green wobbly bit”:


Posted in Delphi, Development, Software Development | Leave a Comment »

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