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from binascii import hexlify
import logging
import os
import select
import time
import threading
import sys
from argparse import Namespace
from socket import socket
from typing import (
Optional,
Text,
Type,
Tuple,
List,
Union
)
from colored import stylize, attr, fg # type: ignore
from paramiko import DSSKey, RSAKey, ECDSAKey, Ed25519Key, PKey
from paramiko.ssh_exception import SSHException
from sshpubkeys import SSHKey # type: ignore
from typeguard import typechecked
from ssh_proxy_server.multisocket import (
create_server_sock,
has_dual_stack,
MultipleSocketsListener
)
from ssh_proxy_server.session import Session
from ssh_proxy_server.forwarders.ssh import SSHBaseForwarder, SSHForwarder
from ssh_proxy_server.forwarders.scp import SCPBaseForwarder, SCPForwarder
from ssh_proxy_server.forwarders.sftp import SFTPHandlerBasePlugin, SFTPHandlerPlugin
from ssh_proxy_server.interfaces.sftp import BaseSFTPServerInterface, SFTPProxyServerInterface
from ssh_proxy_server.forwarders.tunnel import ClientTunnelForwarder, ServerTunnelForwarder
from ssh_proxy_server.authentication import Authenticator, AuthenticatorPassThrough
from ssh_proxy_server.interfaces.server import BaseServerInterface, ServerInterface
from ssh_proxy_server.exceptions import KeyGenerationError
class SSHProxyServer:
SELECT_TIMEOUT = 0.5
@typechecked
def __init__(
self,
listen_port: int,
*,
key_file: Optional[Text] = None,
key_algorithm: Text = 'rsa',
key_length: int = 2048,
ssh_interface: Type[SSHBaseForwarder] = SSHForwarder,
scp_interface: Type[SCPBaseForwarder] = SCPForwarder,
sftp_interface: Type[BaseSFTPServerInterface] = SFTPProxyServerInterface,
sftp_handler: Type[SFTPHandlerBasePlugin] = SFTPHandlerPlugin,
server_tunnel_interface: Type[ServerTunnelForwarder] = ServerTunnelForwarder,
client_tunnel_interface: Type[ClientTunnelForwarder] = ClientTunnelForwarder,
authentication_interface: Type[BaseServerInterface] = ServerInterface,
authenticator: Type[Authenticator] = AuthenticatorPassThrough,
transparent: bool = False,
session_class: Type[Session] = Session,
args: Optional[Namespace] = None
) -> None:
self.args = args
self._threads: List[threading.Thread] = []
self._hostkey: Optional[PKey] = None
self.listen_port = listen_port
self.listen_address = '0.0.0.0' # nosec
self.listen_address_v6 = '::'
self.running = False
self.key_file: Optional[Text] = key_file
self.key_algorithm: Text = key_algorithm
self.key_length: int = key_length
self.ssh_interface: Type[SSHBaseForwarder] = ssh_interface
self.scp_interface: Type[SCPBaseForwarder] = scp_interface
self.sftp_handler: Type[SFTPHandlerBasePlugin] = sftp_handler
self.sftp_interface: Type[BaseSFTPServerInterface] = self.sftp_handler.get_interface() or sftp_interface
self.server_tunnel_interface: Type[ServerTunnelForwarder] = server_tunnel_interface
self.client_tunnel_interface: Type[ClientTunnelForwarder] = client_tunnel_interface
# Server Interface
self.authentication_interface: Type[BaseServerInterface] = authentication_interface
self.authenticator: Type[Authenticator] = authenticator
self.transparent: bool = transparent
self.session_class: Type[Session] = session_class
try:
self.generate_host_key()
except KeyGenerationError:
sys.exit(1)
@typechecked
def generate_host_key(self) -> None:
key_algorithm_class: Optional[Type[PKey]] = None
key_algorithm_bits = None
if self.key_algorithm == 'dss':
key_algorithm_class = DSSKey
key_algorithm_bits = self.key_length
elif self.key_algorithm == 'rsa':
key_algorithm_class = RSAKey
key_algorithm_bits = self.key_length
elif self.key_algorithm == 'ecdsa':
key_algorithm_class = ECDSAKey
elif self.key_algorithm == 'ed25519':
key_algorithm_class = Ed25519Key
if not self.key_file:
logging.error("ed25519 requires a key file, please use also use --host-key parameter")
sys.exit(1)
else:
raise ValueError(f"host key algorithm '{self.key_algorithm}' not supported!")
if not self.key_file:
try:
self._hostkey = key_algorithm_class.generate(bits=key_algorithm_bits) # type: ignore
except ValueError as err:
logging.error(str(err))
raise KeyGenerationError()
else:
if not os.path.isfile(self.key_file):
raise FileNotFoundError(f"host key '{self.key_file}' file does not exist")
for pkey_class in (RSAKey, DSSKey, ECDSAKey, Ed25519Key):
try:
key = self._key_from_filepath(
self.key_file, pkey_class, None
)
self._hostkey = key
break
except SSHException:
pass
else:
logging.error('host key format not supported!')
raise KeyGenerationError()
ssh_pub_key = SSHKey(f"{self._hostkey.get_name()} {self._hostkey.get_base64()}")
ssh_pub_key.parse()
logging.info((
f"{'loaded' if self.key_file else 'generated temporary'} {key_algorithm_class.__name__} key with {self._hostkey.get_bits()} bit length and fingerprints:\n"
f" {stylize(ssh_pub_key.hash_md5(), fg('light_blue') + attr('bold'))}\n"
f" {stylize(ssh_pub_key.hash_sha256(),fg('light_blue') + attr('bold'))}"
))
@typechecked
def _key_from_filepath(self, filename: Text, klass: Type[PKey], password: Optional[Text]) -> PKey:
"""
Attempt to derive a `.PKey` from given string path ``filename``:
- If ``filename`` appears to be a cert, the matching private key is
loaded.
- Otherwise, the filename is assumed to be a private key, and the
matching public cert will be loaded if it exists.
"""
cert_suffix = "-cert.pub"
# Assume privkey, not cert, by default
if filename.endswith(cert_suffix):
key_path = filename[: -len(cert_suffix)]
cert_path = filename
else:
key_path = filename
cert_path = filename + cert_suffix
# Blindly try the key path; if no private key, nothing will work.
key = klass.from_private_key_file(key_path, password)
# TODO: change this to 'Loading' instead of 'Trying' sometime; probably
# when #387 is released, since this is a critical log message users are
# likely testing/filtering for (bah.)
hexlify(key.get_fingerprint())
# Attempt to load cert if it exists.
if os.path.isfile(cert_path):
key.load_certificate(cert_path)
return key
@property
def host_key(self) -> Optional[PKey]:
if not self._hostkey:
self.generate_host_key()
return self._hostkey
@staticmethod
@typechecked
def _clean_environment() -> None:
for env_var in [
'SSH_ASKPASS',
'SSH_AUTH_SOCK',
'SSH_CLIENT',
'SSH_CONNECTION',
'SSH_ORIGINAL_COMMAND',
'SSH_TTY'
]:
try:
del os.environ[env_var]
logging.debug(f"removed {env_var} from environment")
except KeyError:
pass
@typechecked
def start(self) -> None:
self._clean_environment()
sock: Optional[Union[socket, MultipleSocketsListener]] = None
sock = create_server_sock(
(self.listen_address, self.listen_port),
transparent=self.transparent
)
if not has_dual_stack(sock):
sock.close()
sock = MultipleSocketsListener(
[
(self.listen_address, self.listen_port),
(self.listen_address_v6, self.listen_port)
],
transparent=self.transparent
)
if sock is None:
logging.error("error creating socket!")
return
logging.info(f'listen interfaces {self.listen_address} and {self.listen_address_v6} on port {self.listen_port}')
self.running = True
try:
while self.running:
readable = select.select([sock], [], [], self.SELECT_TIMEOUT)[0]
if len(readable) == 1 and readable[0] is sock:
client, addr = sock.accept()
remoteaddr = client.getsockname()
logging.debug(f'incoming connection from {str(addr)} to {remoteaddr}')
thread = threading.Thread(target=self.create_session, args=(client, addr, remoteaddr))
thread.start()
self._threads.append(thread)
except KeyboardInterrupt:
sys.stdout.write('\b\b\r')
sys.stdout.flush()
self.running = False
finally:
logging.info("[red]:exclamation: Shutting down server ...", extra={"markup": True})
sock.close()
for thread in self._threads[:]:
thread.join()
@typechecked
def create_session(
self,
client: socket,
addr: Union[Tuple[Text, int], Tuple[Text, int, int, int]],
remoteaddr: Union[Tuple[Text, int], Tuple[Text, int, int, int]]
) -> None:
try:
with self.session_class(self, client, addr, self.authenticator, remoteaddr) as session:
if session.start():
while session.running:
time.sleep(0.1)
if session.ssh_requested and self.ssh_interface:
session.ssh_requested = False
self.ssh_interface(session).forward()
elif session.scp_requested and self.scp_interface:
session.scp_requested = False
scp_interface = self.scp_interface(session)
thread = threading.Thread(target=scp_interface.forward)
thread.start()
else:
logging.warning("(%s) session not started", session)
self._threads.remove(threading.current_thread())
except Exception:
logging.exception("error handling session creation")