# Copyright 2012 Vaibhav Bajpai # Copyright 2009 Shikhar Bhushan # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import base64 import getpass import os import re import six import sys import socket import threading from binascii import hexlify try: import selectors except ImportError: import selectors2 as selectors from ncclient.capabilities import Capabilities from ncclient.logging_ import SessionLoggerAdapter import paramiko from ncclient.transport.errors import AuthenticationError, SessionCloseError, SSHError, SSHUnknownHostError, NetconfFramingError from ncclient.transport.session import Session from ncclient.transport.session import NetconfBase from ncclient.transport.parser import DefaultXMLParser from ncclient.transport.parser import SAXFilterXMLNotFoundError import logging logger = logging.getLogger("ncclient.transport.ssh") PORT_NETCONF_DEFAULT = 830 BUF_SIZE = 4096 # v1.0: RFC 4742 MSG_DELIM = b"]]>]]>" # v1.1: RFC 6242 END_DELIM = b'\n##\n' TICK = 0.1 # # Define delimiters for chunks and messages for netconf 1.1 chunk enoding. # When matched: # # * result.group(0) will contain whole matched string # * result.group(1) will contain the digit string for a chunk # * result.group(2) will be defined if '##' found # RE_NC11_DELIM = re.compile(br'\n(?:#([0-9]+)|(##))\n') def default_unknown_host_cb(host, fingerprint): """An unknown host callback returns `True` if it finds the key acceptable, and `False` if not. This default callback always returns `False`, which would lead to :meth:`connect` raising a :exc:`SSHUnknownHost` exception. Supply another valid callback if you need to verify the host key programmatically. *host* is the hostname that needs to be verified *fingerprint* is a hex string representing the host key fingerprint, colon-delimited e.g. `"4b:69:6c:72:6f:79:20:77:61:73:20:68:65:72:65:21"` """ return False def _colonify(fp): fp = fp.decode('UTF-8') finga = fp[:2] for idx in range(2, len(fp), 2): finga += ":" + fp[idx:idx+2] return finga if sys.version < '3': from six import StringIO else: from io import BytesIO as StringIO class SSHSession(Session): "Implements a :rfc:`4742` NETCONF session over SSH." def __init__(self, device_handler): capabilities = Capabilities(device_handler.get_capabilities()) Session.__init__(self, capabilities) self._host = None self._host_keys = paramiko.HostKeys() self._transport = None self._connected = False self._channel = None self._channel_id = None self._channel_name = None self._buffer = StringIO() self._device_handler = device_handler self._message_list = [] self._closing = threading.Event() self.parser = DefaultXMLParser(self) # SAX or DOM parser self.logger = SessionLoggerAdapter(logger, {'session': self}) def _dispatch_message(self, raw): # Provide basic response message self.logger.info("Received message from host") # Provide complete response from host at debug log level self.logger.debug("Received:\n%s", raw) return super(SSHSession, self)._dispatch_message(raw) def _parse(self): "Messages ae delimited by MSG_DELIM. The buffer could have grown by a maximum of BUF_SIZE bytes everytime this method is called. Retains state across method calls and if a byte has been read it will not be considered again." return self.parser._parse10() def load_known_hosts(self, filename=None): """Load host keys from an openssh :file:`known_hosts`-style file. Can be called multiple times. If *filename* is not specified, looks in the default locations i.e. :file:`~/.ssh/known_hosts` and :file:`~/ssh/known_hosts` for Windows. """ if filename is None: filename = os.path.expanduser('~/.ssh/known_hosts') try: self._host_keys.load(filename) except IOError: # for windows filename = os.path.expanduser('~/ssh/known_hosts') try: self._host_keys.load(filename) except IOError: pass else: self._host_keys.load(filename) def close(self): self._closing.set() if self._transport.is_active(): self._transport.close() # Wait for the transport thread to close. while self.is_alive() and (self is not threading.current_thread()): self.join(10) if self._channel: self._channel.close() self._channel = None self._connected = False # REMEMBER to update transport.rst if sig. changes, since it is hardcoded there def connect( self, host, port = PORT_NETCONF_DEFAULT, timeout = None, unknown_host_cb = default_unknown_host_cb, username = None, password = None, key_filename = None, allow_agent = True, hostkey_verify = True, hostkey_b64 = None, look_for_keys = True, ssh_config = None, sock_fd = None, bind_addr = None, sock = None, keepalive = None, environment = None): """Connect via SSH and initialize the NETCONF session. First attempts the publickey authentication method and then password authentication. To disable attempting publickey authentication altogether, call with *allow_agent* and *look_for_keys* as `False`. *host* is the hostname or IP address to connect to *port* is by default 830 (PORT_NETCONF_DEFAULT), but some devices use the default SSH port of 22 so this may need to be specified *timeout* is an optional timeout for socket connect *unknown_host_cb* is called when the server host key is not recognized. It takes two arguments, the hostname and the fingerprint (see the signature of :func:`default_unknown_host_cb`) *username* is the username to use for SSH authentication *password* is the password used if using password authentication, or the passphrase to use for unlocking keys that require it *key_filename* is a filename where a the private key to be used can be found *allow_agent* enables querying SSH agent (if found) for keys *hostkey_verify* enables hostkey verification from ~/.ssh/known_hosts *hostkey_b64* only connect when server presents a public hostkey matching this (obtain from server /etc/ssh/ssh_host_*pub or ssh-keyscan) *look_for_keys* enables looking in the usual locations for ssh keys (e.g. :file:`~/.ssh/id_*`) *ssh_config* enables parsing of an OpenSSH configuration file, if set to its path, e.g. :file:`~/.ssh/config` or to True (in this case, use :file:`~/.ssh/config`). *sock_fd* is an already open socket which shall be used for this connection. Useful for NETCONF outbound ssh. Use host=None together with a valid sock_fd number *bind_addr* is a (local) source IP address to use, must be reachable from the remote device. *sock* is an already open Python socket to be used for this connection. *keepalive* Turn on/off keepalive packets (default is off). If this is set, after interval seconds without sending any data over the connection, a "keepalive" packet will be sent (and ignored by the remote host). This can be useful to keep connections alive over a NAT. *environment* a dictionary containing the name and respective values to set """ if not (host or sock_fd or sock): raise SSHError("Missing host, socket or socket fd") self._host = host # Optionally, parse .ssh/config config = {} if ssh_config is True: ssh_config = "~/.ssh/config" if sys.platform != "win32" else "~/ssh/config" if ssh_config is not None: config = paramiko.SSHConfig() with open(os.path.expanduser(ssh_config)) as ssh_config_file_obj: config.parse(ssh_config_file_obj) # Save default Paramiko SSH port so it can be reverted paramiko_default_ssh_port = paramiko.config.SSH_PORT # Change the default SSH port to the port specified by the user so expand_variables # replaces %p with the passed in port rather than 22 (the defauld paramiko.config.SSH_PORT) paramiko.config.SSH_PORT = port config = config.lookup(host) # paramiko.config.SSHconfig::expand_variables is called by lookup so we can set the SSH port # back to the default paramiko.config.SSH_PORT = paramiko_default_ssh_port host = config.get("hostname", host) if username is None: username = config.get("user") if key_filename is None: key_filename = config.get("identityfile") if hostkey_verify: userknownhostsfile = config.get("userknownhostsfile") if userknownhostsfile: self.load_known_hosts(os.path.expanduser(userknownhostsfile)) if timeout is None: timeout = config.get("connecttimeout") if timeout: timeout = int(timeout) if username is None: username = getpass.getuser() if sock_fd is None and sock is None: proxycommand = config.get("proxycommand") if proxycommand: self.logger.debug("Configuring Proxy. %s", proxycommand) if not isinstance(proxycommand, six.string_types): proxycommand = [os.path.expanduser(elem) for elem in proxycommand] else: proxycommand = os.path.expanduser(proxycommand) sock = paramiko.proxy.ProxyCommand(proxycommand) else: for res in socket.getaddrinfo(host, port, socket.AF_UNSPEC, socket.SOCK_STREAM): af, socktype, proto, canonname, sa = res try: sock = socket.socket(af, socktype, proto) sock.settimeout(timeout) except socket.error: continue try: if bind_addr: sock.bind((bind_addr, 0)) sock.connect(sa) except socket.error: sock.close() continue break else: raise SSHError("Could not open socket to %s:%s" % (host, port)) elif sock is None: if sys.version_info[0] < 3: s = socket.fromfd(int(sock_fd), socket.AF_INET, socket.SOCK_STREAM) sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, _sock=s) else: sock = socket.fromfd(int(sock_fd), socket.AF_INET, socket.SOCK_STREAM) sock.settimeout(timeout) self._transport = paramiko.Transport(sock) self._transport.set_log_channel(logger.name) if config.get("compression") == 'yes': self._transport.use_compression() if hostkey_b64: # If we need to connect with a specific hostkey, negotiate for only its type hostkey_obj = None for key_cls in [paramiko.DSSKey, paramiko.Ed25519Key, paramiko.RSAKey, paramiko.ECDSAKey]: try: hostkey_obj = key_cls(data=base64.b64decode(hostkey_b64)) except paramiko.SSHException: # Not a key of this type - try the next pass if not hostkey_obj: # We've tried all known host key types and haven't found a suitable one to use - bail raise SSHError("Couldn't find suitable paramiko key class for host key %s" % hostkey_b64) self._transport._preferred_keys = [hostkey_obj.get_name()] elif self._host_keys: # Else set preferred host keys to those we possess for the host # (avoids situation where known_hosts contains a valid key for the host, but that key type is not selected during negotiation) known_host_keys_for_this_host = self._host_keys.lookup(host) or {} host_port = '[%s]:%s' % (host, port) known_host_keys_for_this_host.update(self._host_keys.lookup(host_port) or {}) if known_host_keys_for_this_host: self._transport._preferred_keys = list(known_host_keys_for_this_host) # Connect try: self._transport.start_client() except paramiko.SSHException as e: raise SSHError('Negotiation failed: %s' % e) server_key_obj = self._transport.get_remote_server_key() fingerprint = _colonify(hexlify(server_key_obj.get_fingerprint())) if hostkey_verify: is_known_host = False # For looking up entries for nonstandard (22) ssh ports in known_hosts # we enclose host in brackets and append port number known_hosts_lookups = [host, '[%s]:%s' % (host, port)] if hostkey_b64: # If hostkey specified, remote host /must/ use that hostkey if(hostkey_obj.get_name() == server_key_obj.get_name() and hostkey_obj.asbytes() == server_key_obj.asbytes()): is_known_host = True else: # Check known_hosts is_known_host = any(self._host_keys.check(lookup, server_key_obj) for lookup in known_hosts_lookups) if not is_known_host and not unknown_host_cb(host, fingerprint): raise SSHUnknownHostError(known_hosts_lookups[0], fingerprint) # Authenticating with our private key/identity if key_filename is None: key_filenames = [] elif isinstance(key_filename, (str, bytes)): key_filenames = [key_filename] else: key_filenames = key_filename self._auth(username, password, key_filenames, allow_agent, look_for_keys) self._connected = True # there was no error authenticating self._closing.clear() if keepalive: self._transport.set_keepalive(keepalive) # TODO: leopoul: Review, test, and if needed rewrite this part subsystem_names = self._device_handler.get_ssh_subsystem_names() for subname in subsystem_names: self._channel = self._transport.open_session() self._channel_id = self._channel.get_id() channel_name = "%s-subsystem-%s" % (subname, str(self._channel_id)) self._channel.set_name(channel_name) if environment: try: self._channel.update_environment(environment) except paramiko.SSHException as e: self.logger.info("%s (environment update rejected)", e) handle_exception = self._device_handler.handle_connection_exceptions(self) # Ignore the exception, since we continue to try the different # subsystem names until we find one that can connect. # have to handle exception for each vendor here if not handle_exception: continue try: self._channel.invoke_subsystem(subname) except paramiko.SSHException as e: self.logger.info("%s (subsystem request rejected)", e) handle_exception = self._device_handler.handle_connection_exceptions(self) # Ignore the exception, since we continue to try the different # subsystem names until we find one that can connect. # have to handle exception for each vendor here if not handle_exception: continue self._channel_name = self._channel.get_name() self._post_connect() # for further upcoming RPC responses, vendor can chose their # choice of parser. Say DOM or SAX self.parser = self._device_handler.get_xml_parser(self) return raise SSHError("Could not open connection, possibly due to unacceptable" " SSH subsystem name.") def _auth(self, username, password, key_filenames, allow_agent, look_for_keys): saved_exception = None for key_filename in key_filenames: for cls in (paramiko.RSAKey, paramiko.DSSKey, paramiko.ECDSAKey, paramiko.Ed25519Key): try: key = cls.from_private_key_file(key_filename, password) self.logger.debug("Trying key %s from %s", hexlify(key.get_fingerprint()), key_filename) self._transport.auth_publickey(username, key) return except Exception as e: saved_exception = e self.logger.debug(e) if allow_agent: for key in paramiko.Agent().get_keys(): try: self.logger.debug("Trying SSH agent key %s", hexlify(key.get_fingerprint())) self._transport.auth_publickey(username, key) return except Exception as e: saved_exception = e self.logger.debug(e) keyfiles = [] if look_for_keys: rsa_key = os.path.expanduser("~/.ssh/id_rsa") dsa_key = os.path.expanduser("~/.ssh/id_dsa") ecdsa_key = os.path.expanduser("~/.ssh/id_ecdsa") if os.path.isfile(rsa_key): keyfiles.append((paramiko.RSAKey, rsa_key)) if os.path.isfile(dsa_key): keyfiles.append((paramiko.DSSKey, dsa_key)) if os.path.isfile(ecdsa_key): keyfiles.append((paramiko.ECDSAKey, ecdsa_key)) # look in ~/ssh/ for windows users: rsa_key = os.path.expanduser("~/ssh/id_rsa") dsa_key = os.path.expanduser("~/ssh/id_dsa") ecdsa_key = os.path.expanduser("~/ssh/id_ecdsa") if os.path.isfile(rsa_key): keyfiles.append((paramiko.RSAKey, rsa_key)) if os.path.isfile(dsa_key): keyfiles.append((paramiko.DSSKey, dsa_key)) if os.path.isfile(ecdsa_key): keyfiles.append((paramiko.ECDSAKey, ecdsa_key)) for cls, filename in keyfiles: try: key = cls.from_private_key_file(filename, password) self.logger.debug("Trying discovered key %s in %s", hexlify(key.get_fingerprint()), filename) self._transport.auth_publickey(username, key) return except Exception as e: saved_exception = e self.logger.debug(e) if password is not None: try: self._transport.auth_password(username, password) return except Exception as e: saved_exception = e self.logger.debug(e) if saved_exception is not None: # need pep-3134 to do this right raise AuthenticationError(repr(saved_exception)) raise AuthenticationError("No authentication methods available") def run(self): chan = self._channel q = self._q def start_delim(data_len): return b'\n#%i\n' % (data_len) try: s = selectors.DefaultSelector() s.register(chan, selectors.EVENT_READ) self.logger.debug('selector type = %s', s.__class__.__name__) while True: # Will wakeup evey TICK seconds to check if something # to send, more quickly if something to read (due to # select returning chan in readable list). events = s.select(timeout=TICK) if events: data = chan.recv(BUF_SIZE) if data: try: self.parser.parse(data) except SAXFilterXMLNotFoundError: self.logger.debug('switching from sax to dom parsing') self.parser = DefaultXMLParser(self) self.parser.parse(data) elif self._closing.is_set(): # End of session, expected break else: # End of session, unexpected raise SessionCloseError(self._buffer.getvalue()) if not q.empty() and chan.send_ready(): self.logger.debug("Sending message") data = q.get().encode() if self._base == NetconfBase.BASE_11: data = b"%s%s%s" % (start_delim(len(data)), data, END_DELIM) else: data = b"%s%s" % (data, MSG_DELIM) self.logger.info("Sending:\n%s", data) while data: n = chan.send(data) if n <= 0: raise SessionCloseError(self._buffer.getvalue(), data) data = data[n:] except Exception as e: self.logger.debug("Broke out of main loop, error=%r", e) self._dispatch_error(e) self.close() @property def host(self): """Host this session is connected to, or None if not connected.""" if hasattr(self, '_host'): return self._host return None @property def transport(self): "Underlying `paramiko.Transport `_ object. This makes it possible to call methods like :meth:`~paramiko.Transport.set_keepalive` on it." return self._transport