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

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Archive for October 20th, 2021

Difficult programming concepts explained in tweets

Posted by jpluimers on 2021/10/20

Highlights from the thread [Archive.is] 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: “whoami.filippo.io , the SSH server that knows who you are … Try it out! $ ssh http://whoami.filippo.io”

Posted by jpluimers on 2021/10/20

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

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

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: [Archive.is] 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/whoami.filippo.io: A ssh server that knows who you are. $ ssh whoami.filippo.io: 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

Host example.com
    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

Host github.com
    PubkeyAuthentication yes
    IdentityFile ~/.ssh/github_id_rsa

–jeroen

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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 »

 
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