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SSH Support in C-Kermit for Windows

C-Kermit for Windows now includes limited built-in SSH support based on libssh1. The code is currently very new and likely still has bugs - if you find one please report it!

To get started, type help ssh at the kermit prompt but note that not all commands are implemented yet!

For convenience C-Kermit currently looks for the known_hosts file as well as your public and private keys in %USERPROFILE%\.ssh. This directory is also used by the version of OpenSSH bundled with Windows 10+ so if you were previously using that your keys and known hosts should be picked up automatically by C-Kermit.

Known Issues

  • When connecting to modern linux hosts with the linux terminal type, you'll likely need to set your remote charset to utf8. You can do this with: 
    set term type linux
set term remote utf8
    For convenience, you can create a file called k95custom.ini in the same directory as k95g.exe and place these commands there so that they're run automatically every time you start C-Kermit.
  • If you find your session disconnecting when left idle, try enabling the heartbeat feature with the set ssh heartbeat-interval command.
  • The keyboard interactive authentication method doesn't seem to work so it's disabled by default for now. See the Supported Authentication Methods section for more details.
  • Connecting through proxy servers is not currently supported

Supported Commands

Only the following commands are implemented at this time. More will come in the future. Commands not listed below either do nothing or return an error at this time.

SSH [OPEN] host [port]
   host: hostname or IP to connect to
   port: port name or number to connect on.
   /COMMAND:command
	   Command to execute instead of your default shell
   /USER:user
	   Defaults to \v(userid)
   /PASSWORD:pass
   /VERSION:{1,2}
	   Just reports an error if version is 1 (SSH-1 not supported)
   /SUBSYSTEM:name
	   Implemented though doesn't appear to be working at the moment
SSH KEY 
  CREATE [ /BITS:bits /PASSPHRASE:passphrase /TYPE:{ DSS, ECDSA, ED25519, RSA } ] filename
    Creates an SSH key pair
  CHANGE-PASSPHRASE [ /NEW-PASSPHRASE:passphrase /OLD-PASSPHRASE:passphrase ] filename
    Change the passphrase for an existing key
  DISPLAY [ /FORMAT:{FINGERPRINT,OPENSSH,SSH.COM} ] filename
    Display the SSH key fingerprint or public key.
SET SSH			
   COMPRESSION {ON,OFF}
   HEARTBEAT-INTERVAL interval
       Off by default, set this to some interval in seconds to prevent idle timeouts
   STRICT-HOST-KEY-CHECK {ASK, ON, OFF}
   USE-OPENSSH-CONFIG {ON,OFF}
   V2 AUTHENTICATION {GSSAPI, KEYBOARD-INTERACTIVE, PASSWORD, PUBKEY }
	   The following values are implemented: KEYBOARD-INTERACTIVE, PASSWORD, PUBKEY
	       (GSSAPI is processed but GSSAPI Auth isn't implemented yet)
   V2 CIPHERS {3des-cbc, aes128-cbc, aes192-cbc, aes256-cbc, chachae20-poly1305, 
        [email protected], [email protected], aes256-ctr, aes192-ctr, 
        aes128-ctr}
   V2 GLOBAL-KNOWN-HOSTS-FILE filename
   V2 HOSTKEY-ALGORITHMS {ssh-ed25519, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, 
        ecdsa-sha2-nistp521, ssh-rsa, rsa-sha2-512, rsa-sha2-256,ssh-ds}
   V2 KEY-EXCHANGE-METHODS {...}
   V2 USER-KNOWN-HOSTS-FILE filename
   VERBOSE level
	   Report Errors - Verbosity Level. Range 0-7. Value stored in ssh_vrb
   SSH VERSION {2, AUTOMATIC}
	   Just reports an error if version is 1 (SSH-1 not supported)
SHOW SSH
    Shows ssh settings

Supported Authentication Methods

At this time password and public key authentication are implemented and work.

Keyboard interactive authentication is also implemented but didn't work when tested against OpenSSH 8.4p1 Debian-5deb11u1. If you want to try it out anyway, you can enable only keyboard interactive authentication by entering set ssh v2 auth keyb at the kermit prompt before starting your session.

If you want to enable keyboard interactive authentication alongside password and public key, enter set ssh v2 auth keyb pass pub instead.

Footnotes

  1. https://libssh.org ↩