[isabelle-dev] NEWS: Isabelle/Scala SSH connections use OpenSSH executables

Makarius makarius at sketis.net
Thu Sep 15 11:59:13 CEST 2022

*** System ***

* Isabelle/Scala SSH connections now use regular OpenSSH executables
from the local system: ssh, scp, sftp; the old ssh-java component has
been discontinued. This has various practical consequences:

   - Authentication and configuration works accurately via the official
     .ssh/known_hosts and .ssh/config files.

   - Host connections are usually shared (via multiplexed channels), to
     reduce the overhead for multiple commands. This also works for SSH
     connections for rsync (e.g. "isabelle sync"). Windows/Cygwin does
     not support multiplexing: the functionality should be the same, but
     slower, with a new connection for each command.

   - Multiple hops via "bastion hosts" can be easily configured in
     .ssh/config via ProxyJump declarations. The former Isabelle/Scala
     parameters for proxy_host etc. have been discontinued: minor

This refers to Isabelle/361cfb8e3648.

The change is motivated by a recent update of the OpenSSH server in Cygwin, 
which locked out the ssh-java/jsch client for unknown reasons. Since jsch is 
somewhat old and hardly maintained, I sat down to study the man pages for ssh 
and ssh_config carefully. The result is formalized src/Pure/General/ssh.scala

Now we can have Windows heaps for the release ...


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