Fixed a bug (open on the upstream fork), also rewote config.

Fixed a bug that caused sessions to get overwritten and some of them
would seem to freeze, the whole thing relied on undefined behavior.
This bug was a static variable that copied sessions all around globally.

Rewrote the config to support a few more options (the PasswordType is coming soon)
and explained how the new authorized_users files work.

Public key authentication now has the same number of retires that
password authentication has (this aligns with how OpenSSH does it)
and the number of retries can now be configured in the configuration.

src/main/resources/config.yml

@@ -1,22 +1,35 @@
 # The IP addresses(s) the SSH server will listen on. Use a comma separated list for multiple addresses.
 # Leave as "all" for all addresses.
-listenAddress: all
-# The port the SSH server will listen on.
-port: 22
+ListenAddress: all
+# The port the SSH server will listen on. Note that anything above 1024 will require you to run
+# the whole minecraft server with elevated privileges, this is not recommended and you should
+# use iptables to route packets from a lower port.
+Port: 1025
 
 # Operational mode. Don't touch if you don't know what you're doing. Can be either DEFAULT or RPC
-mode: DEFAULT
+Mode: DEFAULT
 
 # Enable built-in SFTP server or not. You'll be able to connect and upload/download files via SFTP protocol.
 # Might be useful for testing purposes as well , i. e. docker containers.
-enableSFTP: true
+EnableSFTP: true
+
+# Number of times a person can fail to use an SSH key or enter a password
+# before it terminates the connection.
+LoginRetries: 3
 
 # By default, only public key authentication is enabled. This is the most secure mode.
-# To authorize a user to log in with public key authentication, install their public
-# PEM certificate in the authorized_users directory. Name the key file with user's user
-# name (no file extension).
+# To authorize a user to login with their public key, install their key using the
+# OpenSSH authorized_keys file format in the authorized_users directory. Name the key
+# file with the user's username and no extension. Note: If you want to let a user have
+# many keys, you can append the keys to their file in authorized_users.
 
 # For less secure username and password based authentication, complete the sections below.
-credentials:
+
+# Type of hashing to use for the passwords below.
+# Options are: PLAIN (insecure), bcrypt, pbkdf, sha256
+PasswordType: bcrypt
+
+# Associate each username with a password hash (or the password if the PasswordType is set to PLAIN)
+Credentials:
 #    user1: password1
 #    user2: password2