To fix the “no matching host key type found” error in SSH, you need to modify your SSH client configuration to accept the host key types offered by the SSH server.
This error typically occurs when your SSH client does not support or is not configured to accept the host key types provided by the server.
Example error
Unable to negotiate with X.X.X.X port 22. no matching host key type found. Their offer: rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519.
Here’s a general approach to resolving this issue:
Table of Contents
Temporarily Allow Key Type in Command
Specify the host key algorithms directly in your SSH command:
ssh -o HostkeyAlgorithms=+ssh-rsa,ssh-dss user@hostname
Or you can add these options to the SSH client configuration file.
Modify SSH Client Configuration file
To resolve SSH host key type errors, modify the SSH client configuration:
- Edit the SSH client configuration file. Use ~/.ssh/config for a specific user or /etc/ssh/ssh_config for system-wide settings.
- Add or modify the line with HostkeyAlgorithms followed by the required host key type. For example, HostkeyAlgorithms ssh-rsa.
- Save the file and retry the SSH connection to implement the changes.
Troubleshooting Steps
Identify Supported Key Types
List the key types your client supports using ssh -Q key
You can do this by running the following command in your terminal:
ssh -Q key
This will display a list of supported key types, such as ssh-rsa, ecdsa-sha2-nistp256, ssh-ed25519, etc.
Identify Server-Offered Key Types
Look at the error message you received (e.g., “no matching host key type found. Their offer: ssh-rsa,ssh-dss”). It should list the key types the server is offering.
Compare the Lists
Compare the key types from your client’s list with those offered by the server. Identify any matching key types. If there’s a match, ensure your SSH configuration is set to use one of these common key types.
Following these steps can help you modify your SSH client to accommodate the server’s host key types, resolving the error while considering security implications.
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