Add SFTP support to agent

[adamkissvcc]

Please describe what you need help with:

Hello,
I'm using containerssh in kubernetes. Is it possible to use sshd in the container for handling sftp? (instead of sftp-server). I'm following up on #240, and I would like to use it's ChrootDirectory feature, but I can't get it working.

Have you read the troubleshooting guide?

Knowing this information helps us avoid unnecessary questions.

What have you tried to resolve this problem?

I tried setting

subsystems:
        sftp: /sftp.sh

where sftp.sh calls exec /usr/sbin/sshd -D, but i guess it's not that simple, I don't fully understand how sftp works with containerssh.

[ghost]

@adamkissvcc we can do this by including an SFTP protocol decoder in the ContainerSSH agent. This will, however, take some doing, so it may take a while.