Azure DevOps Server Error: Unable to negotiate with <x.x.x.x> port 22: no matching host key type found. Their offer: ssh-rsa

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Tafadzwa Chakavarika
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Introduction

This KB article applies to Terraform Enterprise (TFE) v202309-1 when connected to Azure DevOps Server 2020 and 2019.

Problem

After upgrading TFE to v202309-1, which has consolidated services enabled by default, workspaces that are connected to Azure DevOps Server may fail with this error

Failed to ingress slug: Failed to clone: Failed to reach repo using proxy: Failed on ls-remote: exit status 128
Output: Unable to negotiate with <x.x.x.x> port 22: no matching host key type found. Their offer: ssh-rsa
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

Cause

This issue is caused during SSH negotiation as consolidated services uses a newer version of OpenSSH than what may be configured on the Azure DevOps Server. Specifically the SHA-1 hash algorithm has been disabled by default in newer OpenSSH implementations as it is cryptographically broken. Refer here for more details.

Solutions

  1. Microsoft recently released some patches to align with industry wide changes, refer to 2020 patch and 2019 patch for the details.
    • Installing the patch will resolve the issue and Azure DevOps should connect to TFE.
  2. If there are some restrictions on installing the patch, the workaround is to disable the consolidated services by following below instructions, refer here as well.
    • Disable the consolidated_services_enabled setting.

replicatedctl app-config set consolidated_services_enabled --value 0

    • Restart Terraform Enterprise

- replicatedctl app stop

- Wait for the application to stop, check with replicatedctl app status until "State" transitions to "stopped"

- replicatedctl app start

            NOTE: Disabling consolidated services will only be possible until v202401-1, refer to the                              release notes here.

       3. If you are using Terraform Enterprise FDO Docker installation the workaround is     

    • Create this file in your TFE host(s) and change the permission settings
echo 'PubKeyAcceptedAlgorithms=+ssh-rsa' | sudo tee /etc/ssh/tfe_allow_rsa
chmod 644 /etc/ssh/tfe_allow_rsa
    • Edit your compose.yaml file and add a volume type bind. Save and redeploy your container with docker compose
volumes:
...
  - type: bind
    source: /etc/ssh/tfe_allow_rsa
    target: /etc/ssh/ssh_config.d/tfe_allow_rsa

       4. No workaround exists at the moment for Terraform Enterprise FDO on Kubernetes.

Additional Information

 

 

 

 

 

 

 

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