darkoperator / darkoperator/Posh-SSH

New-SSHSession not working against certain ciphers

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Description

Hi,

I've inherited and environment of ESXi hosts where thy are running a special list of ciphers in sshd_config of each ESXi host.
The list is below

KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256

HostKeyAlgorithms ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,rsa-sha2-256,rsa-sha2-512

I cannot establish SSH connection using new-sshsession from posh-ssh 2.3.0, PS 5.1 and Windows 2019 server.
As soon as I comment out these lines I am able to connect. Is there anything that can be done for POSH-SSH to support the algo's above?

Thanks,
ionut

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start at the New-SSHSession entry point and reproduce the failure against an ESXi host using the listed KexAlgorithms and HostKeyAlgorithms under PowerShell 5.1 and Posh-SSH 2.3.0. Capture the connection error and inspect how SSH algorithm negotiation is handled. Done means New-SSHSession connects successfully with this configuration and the behavior is covered by a regression check if the repository provides one.

Written by the indexing model from the issue text.

Assessment

Tech stack
powershell
Domain
networking, security
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
32/100

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