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

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Archive for the ‘Internet protocol suite’ Category

Happy birthday UDP!

Posted by jpluimers on 2020/08/20

Today it’s the 40th birthday of UDP. Or more precise: 40 years after [WayBackRFC 768 – User Datagram Protocol got submitted.

It is still used a lot today, so be sure to read more background on [WayBackUser Datagram Protocol – Wikipedia.

And of course on a birthday, it is nice to have few good jokes. So here we go:

[WayBack“I would tell you a joke about UDP, but you probably wouldn’t get it.” | Hacker News

[WayBack] I would tell you a joke about UDP, but you probably wouldn’t get it. So here’s a TCP joke | reddit.

[Archive.is]:

  • UDP packet bar walks into
  • The best thing about UDP jokes is that I don’t care if you get it. #sysadmin #networking #IT

You can generate more yourself: udpjoke.py

–jeroen

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Posted in Communications Development, Development, History, Internet protocol suite, UDP | Leave a Comment »

Remote access to the Embarcadero License Center via SSH tunnel – twm’s blog

Posted by jpluimers on 2020/08/10

Thomas basically did all the research on the forwarding needed for ELC (formerly Belise/Elise), then showed the PuTTY equivalent to ssh user@remote -L5567:192.168.1.200:5567:

[WayBackRemote access to the Embarcadero License Center via SSH tunnel – twm’s blog

Via: [WayBack] Once you have set up an Embarcadero License Center (ELC) for your company (with network named user or concurrent licenses) you will need network access … – Thomas Mueller (dummzeuch) – Google+

Related: [WayBack] Introducing the Embarcadero License Center – ELC

–jeroen

 

Posted in *nix, Communications Development, Delphi, Development, Internet protocol suite, Licensing, Power User, Software Development, SSH, ssh/sshd | Leave a Comment »

ssh_config section order is important: the first setting obtained from a Host/Match section applies

Posted by jpluimers on 2020/06/12

Often, configuration files work like this:

  • global settings are at the top
  • detailed settings are further on, overwriting global settings

Not for ssh_config though, so I was right writing I should read more on it in Good read for starting to intermediate ssh users is “SSH Essentials: Working with SSH Servers, Clients, and Keys | DigitalOcean” and pointers to more advanced reading material.

So here is how ssh_config does it as per man page at [WayBack] ssh_config(5) – OpenBSD manual pages and [WayBack] ssh_config — OpenSSH SSH client configuration files at Linux.org:

     For each parameter, the first obtained value will be used.  The configuration files contain sections separated
     by “Host” specifications, and that section is only applied for hosts that match one of the patterns given in the
     specification.  The matched host name is the one given on the command line.

     Since the first obtained value for each parameter is used, more host-specific declarations should be given near
     the beginning of the file, and general defaults at the end.

This means a section Host * needs to come at the end.

I got that wrong and it took me the better half of a morning to figure out the cause of a connection problem ending in this:

debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred publickey
debug3: authmethod_lookup publickey
debug3: remaining preferred:
debug1: No more authentication methods to try.

Somehow, the identity file was never used to try public key authentication at all because of the ssh_config order in ~/.ssh/config.

I’m not the only one confused, as during the search for the cause with “remaining preferred” “No more authentication methods to try.”:

Maybe now I should step up from manually editing the ssh_config file and use [WayBack] GitHub – moul/advanced-ssh-config: make your ssh client smarter to generate it for me.

–jeroen

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

Authssh from Windows

Posted by jpluimers on 2020/05/22

Running autossh from Windows is still on my list, so here are a few links:

–jeroen

Posted in Communications Development, Development, Internet protocol suite, Power User, SSH, TCP, Windows | Leave a Comment »

On my list of things to try: GitHub – arthepsy/ssh-audit; SSH server auditing

Posted by jpluimers on 2020/05/18

This looks like an ssh equivalent to testssl.sh: [WayBack] GitHub – arthepsy/ssh-audit: SSH server auditing (banner, key exchange, encryption, mac, compression, compatibility, security, etc).

It is on my list of things to try, so I’ve put a watch on the repository changes.

–jeroen

Read the rest of this entry »

Posted in Communications Development, Development, Encryption, Internet protocol suite, Power User, Security, SSH, TCP | Leave a Comment »

 
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