Initial commit of barebones SSH server.

.gitignore

@@ -85,7 +85,7 @@ ipython_config.py
 # pyenv
 #   For a library or package, you might want to ignore these files since the code is
 #   intended to run in multiple environments; otherwise, check them in:
-# .python-version
+.python-version
 
 # pipenv
 #   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
@@ -160,3 +160,8 @@ cython_debug/
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 #.idea/
+
+# SSH Keys
+ssh_host_key
+*.key 
+*.pub

ssh_server.py

@@ -0,0 +1,60 @@
+# To run this program, the file ``ssh_host_key`` must exist with an SSH
+# private key in it to use as a server host key. An SSH host certificate
+# can optionally be provided in the file ``ssh_host_key-cert.pub``.
+
+import asyncio, asyncssh, crypt, sys
+from typing import Optional
+
+passwords = {'guest': '',                 # guest account with no password
+             'user123': 'qV2iEadIGV2rw'   # password of 'secretpw'
+            }
+
+async def handle_client(process: asyncssh.SSHServerProcess) -> None:
+    process.stdout.write('Welcome to my SSH server, %s!\n' %
+                         process.get_extra_info('username'))
+    
+    try:
+        async for line in process.stdin:
+            line = line.rstrip('\n')
+            if line:
+                process.stdout.write('You entered: %s\n' % line)
+    except asyncssh.BreakReceived:
+        pass
+
+    process.exit(0)
+
+class MySSHServer(asyncssh.SSHServer):
+    def connection_made(self, conn: asyncssh.SSHServerConnection) -> None:
+        print('SSH connection received from %s.' %
+                  conn.get_extra_info('peername')[0])
+
+    def connection_lost(self, exc: Optional[Exception]) -> None:
+        if exc:
+            print('SSH connection error: ' + str(exc), file=sys.stderr)
+        else:
+            print('SSH connection closed.')
+
+    def begin_auth(self, username: str) -> bool:
+        # If the user's password is the empty string, no auth is required
+        return passwords.get(username) != ''
+
+    def password_auth_supported(self) -> bool:
+        return True
+
+    def validate_password(self, username: str, password: str) -> bool:
+        pw = passwords.get(username, '*')
+        return crypt.crypt(password, pw) == pw
+
+async def start_server() -> None:
+    await asyncssh.create_server(MySSHServer, '', 8022,
+                                 server_host_keys=['ssh_host_key'],
+                                 process_factory=handle_client)
+
+loop = asyncio.get_event_loop()
+
+try:
+    loop.run_until_complete(start_server())
+except (OSError, asyncssh.Error) as exc:
+    sys.exit('Error starting server: ' + str(exc))
+
+loop.run_forever()