Ssh Frustrations

Support
1

Have a very, very old SCO UnixWare 7.1.4 VM that I’m trying to ssh into from AlmaLinux 9.4. When I try a simple: ssh user@ipnum I get:
Bad server host key: Invalid key length

Interestingly, cygwin reports:
Unable to negotiate with ipnum port 22: no matching key exchange method found. Their offer: diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1

I’ve been able to get cygwin working with the command:
ssh -o KexAlgorithms=+diffie-hellman-group1-sha1 -o HostKeyAlgorithms=+ssh-rsa -o PubkeyAcceptedAlgorithms=+ssh-rsa user@ipnum

Naturally, that doesn’t work from AlmaLinux.

Using odd AlmaLinux options I can get: no matching host key type found. Their offer: ssh-rsa,ssh-dss

Curious how the offer is different between AlmaLinux and cygwin.

Still need to figure out the correct chants and incantations for AlmaLinux. When using one or more “-v” options, I don’t really get much more information than what cygwin reports. Update-crypto-policies is set to LEGACY

Any clues as to what I’m missing? I’d like to get it working from the command line before I try to update any config file.

Thanks

2

The server has (RSA) host key that does not have enough bits. See SSH is failing to RHEL 9 using 1024-bit RSA keys - Red Hat Customer Portal

3

Unfortunately, that RHEL article is completely useless, doesn’t work, and is severe overkill.

After spending countless hours more on this, here is the solution:
ssh -o HostKeyAlgorithms=+ssh-rsa,ssh-dss -o PubkeyAcceptedAlgorithms=+ssh-rsa,ssh-dss -o RSAMinSize=1024 user_name@ip_number

Don’t have to make any configuration changes to anything. Easiest to put the options in user’s .ssh/config file