#!/usr/bin/python # Copyright (C) 2003-2004 Robey Pointer # # This file is part of paramiko. # # Paramiko is free software; you can redistribute it and/or modify it under the # terms of the GNU Lesser General Public License as published by the Free # Software Foundation; either version 2.1 of the License, or (at your option) # any later version. # # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR # A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more # details. # # You should have received a copy of the GNU Lesser General Public License # along with Paramiko; if not, write to the Free Software Foundation, Inc., # 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. """ L{BaseTransport} handles the core SSH2 protocol. """ import sys, os, string, threading, socket, struct, time from common import * from ssh_exception import SSHException from message import Message from channel import Channel import util from rsakey import RSAKey from dsskey import DSSKey from kex_group1 import KexGroup1 from kex_gex import KexGex from primes import ModulusPack # these come from PyCrypt # http://www.amk.ca/python/writing/pycrypt/ # i believe this on the standards track. # PyCrypt compiled for Win32 can be downloaded from the HashTar homepage: # http://nitace.bsd.uchicago.edu:8080/hashtar from Crypto.Cipher import Blowfish, AES, DES3 from Crypto.Hash import SHA, MD5, HMAC # for thread cleanup _active_threads = [] def _join_lingering_threads(): for thr in _active_threads: thr.active = False import atexit atexit.register(_join_lingering_threads) class BaseTransport (threading.Thread): """ Handles protocol negotiation, key exchange, encryption, and the creation of channels across an SSH session. Basically everything but authentication is done here. """ _PROTO_ID = '2.0' _CLIENT_ID = 'pyssh_1.1' preferred_ciphers = [ 'aes128-cbc', 'blowfish-cbc', 'aes256-cbc', '3des-cbc' ] preferred_macs = [ 'hmac-sha1', 'hmac-md5', 'hmac-sha1-96', 'hmac-md5-96' ] preferred_keys = [ 'ssh-rsa', 'ssh-dss' ] preferred_kex = [ 'diffie-hellman-group1-sha1', 'diffie-hellman-group-exchange-sha1' ] _cipher_info = { 'blowfish-cbc': { 'class': Blowfish, 'mode': Blowfish.MODE_CBC, 'block-size': 8, 'key-size': 16 }, 'aes128-cbc': { 'class': AES, 'mode': AES.MODE_CBC, 'block-size': 16, 'key-size': 16 }, 'aes256-cbc': { 'class': AES, 'mode': AES.MODE_CBC, 'block-size': 16, 'key-size': 32 }, '3des-cbc': { 'class': DES3, 'mode': DES3.MODE_CBC, 'block-size': 8, 'key-size': 24 }, } _mac_info = { 'hmac-sha1': { 'class': SHA, 'size': 20 }, 'hmac-sha1-96': { 'class': SHA, 'size': 12 }, 'hmac-md5': { 'class': MD5, 'size': 16 }, 'hmac-md5-96': { 'class': MD5, 'size': 12 }, } _kex_info = { 'diffie-hellman-group1-sha1': KexGroup1, 'diffie-hellman-group-exchange-sha1': KexGex, } REKEY_PACKETS = pow(2, 30) REKEY_BYTES = pow(2, 30) OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED, OPEN_FAILED_CONNECT_FAILED, OPEN_FAILED_UNKNOWN_CHANNEL_TYPE, \ OPEN_FAILED_RESOURCE_SHORTAGE = range(1, 5) _modulus_pack = None def __init__(self, sock): """ Create a new SSH session over an existing socket, or socket-like object. This only creates the Transport object; it doesn't begin the SSH session yet. Use L{connect} or L{start_client} to begin a client session, or L{start_server} to begin a server session. If the object is not actually a socket, it must have the following methods: - C{send(string)}: Writes from 1 to C{len(string)} bytes, and returns an int representing the number of bytes written. Returns 0 or raises C{EOFError} if the stream has been closed. - C{recv(int)}: Reads from 1 to C{int} bytes and returns them as a string. Returns 0 or raises C{EOFError} if the stream has been closed. For ease of use, you may also pass in an address (as a tuple) or a host string as the C{sock} argument. (A host string is a hostname with an optional port (separated by C{":"}) which will be converted into a tuple of C{(hostname, port)}.) A socket will be connected to this address and used for communication. Exceptions from the C{socket} call may be thrown in this case. @param sock: a socket or socket-like object to create the session over. @type sock: socket """ if type(sock) is str: # convert "host:port" into (host, port) hl = sock.split(':', 1) if len(hl) == 1: sock = (hl[0], 22) else: sock = (hl[0], int(hl[1])) if type(sock) is tuple: # connect to the given (host, port) hostname, port = sock sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.connect((hostname, port)) # okay, normal socket-ish flow here... threading.Thread.__init__(self, target=self._run) self.randpool = randpool self.sock = sock # Python < 2.3 doesn't have the settimeout method - RogerB try: # we set the timeout so we can check self.active periodically to # see if we should bail. socket.timeout exception is never # propagated. self.sock.settimeout(0.1) except AttributeError: pass # negotiated crypto parameters self.local_version = 'SSH-' + self._PROTO_ID + '-' + self._CLIENT_ID self.remote_version = '' self.block_size_out = self.block_size_in = 8 self.local_mac_len = self.remote_mac_len = 0 self.engine_in = self.engine_out = None self.local_cipher = self.remote_cipher = '' self.sequence_number_in = self.sequence_number_out = 0L self.local_kex_init = self.remote_kex_init = None self.session_id = None # /negotiated crypto parameters self.expected_packet = 0 self.active = False self.initial_kex_done = False self.write_lock = threading.RLock() # lock around outbound writes (packet computation) self.lock = threading.Lock() # synchronization (always higher level than write_lock) self.channels = { } # (id -> Channel) self.channel_events = { } # (id -> Event) self.channel_counter = 1 self.logger = logging.getLogger('paramiko.transport') self.window_size = 65536 self.max_packet_size = 32768 self.ultra_debug = False self.saved_exception = None self.clear_to_send = threading.Event() # used for noticing when to re-key: self.received_bytes = 0 self.received_packets = 0 self.received_packets_overflow = 0 self.sent_bytes = 0 self.sent_packets = 0 # user-defined event callbacks: self.completion_event = None # keepalives: self.keepalive_interval = 0 self.keepalive_last = time.time() # server mode: self.server_mode = 0 self.server_object = None self.server_key_dict = { } self.server_accepts = [ ] self.server_accept_cv = threading.Condition(self.lock) def __repr__(self): """ Returns a string representation of this object, for debugging. @rtype: string """ if not self.active: return '' out = '} or L{auth_publickey }. @note: L{connect} is a simpler method for connecting as a client. @note: After calling this method (or L{start_server} or L{connect}), you should no longer directly read from or write to the original socket object. @param event: an event to trigger when negotiation is complete. @type event: threading.Event """ self.completion_event = event self.start() def start_server(self, event=None, server=None): """ Negotiate a new SSH2 session as a server. This is the first step after creating a new L{Transport} and setting up your server host key(s). A separate thread is created for protocol negotiation, so this method returns immediately. When negotiation is done (successful or not), the given C{Event} will be triggered. On failure, L{is_active} will return C{False}. After a successful negotiation, the client will need to authenticate. Override the methods L{get_allowed_auths }, L{check_auth_none }, L{check_auth_password }, and L{check_auth_publickey } in the given C{server} object to control the authentication process. After a successful authentication, the client should request to open a channel. Override L{check_channel_request } in the given C{server} object to allow channels to be opened. @note: After calling this method (or L{start_client} or L{connect}), you should no longer directly read from or write to the original socket object. @param event: an event to trigger when negotiation is complete. @type event: threading.Event @param server: an object used to perform authentication and create L{Channel}s. @type server: L{server.ServerInterface} """ if server is None: server = ServerInterface() self.server_mode = 1 self.server_object = server self.completion_event = event self.start() def add_server_key(self, key): """ Add a host key to the list of keys used for server mode. When behaving as a server, the host key is used to sign certain packets during the SSH2 negotiation, so that the client can trust that we are who we say we are. Because this is used for signing, the key must contain private key info, not just the public half. @param key: the host key to add, usually an L{RSAKey } or L{DSSKey }. @type key: L{PKey } """ self.server_key_dict[key.get_name()] = key def get_server_key(self): """ Return the active host key, in server mode. After negotiating with the client, this method will return the negotiated host key. If only one type of host key was set with L{add_server_key}, that's the only key that will ever be returned. But in cases where you have set more than one type of host key (for example, an RSA key and a DSS key), the key type will be negotiated by the client, and this method will return the key of the type agreed on. If the host key has not been negotiated yet, C{None} is returned. In client mode, the behavior is undefined. @return: host key of the type negotiated by the client, or C{None}. @rtype: L{PKey } """ try: return self.server_key_dict[self.host_key_type] except KeyError: return None def load_server_moduli(filename=None): """ I{(optional)} Load a file of prime moduli for use in doing group-exchange key negotiation in server mode. It's a rather obscure option and can be safely ignored. In server mode, the remote client may request "group-exchange" key negotiation, which asks the server to send a random prime number that fits certain criteria. These primes are pretty difficult to compute, so they can't be generated on demand. But many systems contain a file of suitable primes (usually named something like C{/etc/ssh/moduli}). If you call C{load_server_moduli} and it returns C{True}, then this file of primes has been loaded and we will support "group-exchange" in server mode. Otherwise server mode will just claim that it doesn't support that method of key negotiation. @param filename: optional path to the moduli file, if you happen to know that it's not in a standard location. @type filename: string @return: True if a moduli file was successfully loaded; False otherwise. @rtype: bool @since: doduo @note: This has no effect when used in client mode. """ BaseTransport._modulus_pack = ModulusPack(randpool) # places to look for the openssh "moduli" file file_list = [ '/etc/ssh/moduli', '/usr/local/etc/moduli' ] if filename is not None: file_list.insert(0, filename) for fn in file_list: try: BaseTransport._modulus_pack.read_file(fn) return True except IOError: pass # none succeeded BaseTransport._modulus_pack = None return False load_server_moduli = staticmethod(load_server_moduli) def close(self): """ Close this session, and any open channels that are tied to it. """ self.active = False self.engine_in = self.engine_out = None self.sequence_number_in = self.sequence_number_out = 0L for chan in self.channels.values(): chan._unlink() def get_remote_server_key(self): """ Return the host key of the server (in client mode). @note: Previously this call returned a tuple of (key type, key string). You can get the same effect by calling L{PKey.get_name } for the key type, and C{str(key)} for the key string. @raise SSHException: if no session is currently active. @return: public key of the remote server. @rtype: L{PKey } """ if (not self.active) or (not self.initial_kex_done): raise SSHException('No existing session') return self.host_key def is_active(self): """ Return true if this session is active (open). @return: True if the session is still active (open); False if the session is closed. @rtype: bool """ return self.active def open_session(self): """ Request a new channel to the server, of type C{"session"}. This is just an alias for C{open_channel('session')}. @return: a new L{Channel} on success, or C{None} if the request is rejected or the session ends prematurely. @rtype: L{Channel} """ return self.open_channel('session') def open_channel(self, kind, dest_addr=None, src_addr=None): """ Request a new channel to the server. L{Channel}s are socket-like objects used for the actual transfer of data across the session. You may only request a channel after negotiating encryption (using L{connect} or L{start_client} and authenticating. @param kind: the kind of channel requested (usually C{"session"}, C{"forwarded-tcpip"} or C{"direct-tcpip"}). @type kind: str @param dest_addr: the destination address of this port forwarding, if C{kind} is C{"forwarded-tcpip"} or C{"direct-tcpip"} (ignored for other channel types). @type dest_addr: (str, int) @param src_addr: the source address of this port forwarding, if C{kind} is C{"forwarded-tcpip"} or C{"direct-tcpip"}. @type src_addr: (str, int) @return: a new L{Channel} on success, or C{None} if the request is rejected or the session ends prematurely. @rtype: L{Channel} """ chan = None try: self.lock.acquire() chanid = self.channel_counter self.channel_counter += 1 m = Message() m.add_byte(chr(MSG_CHANNEL_OPEN)) m.add_string(kind) m.add_int(chanid) m.add_int(self.window_size) m.add_int(self.max_packet_size) if (kind == 'forwarded-tcpip') or (kind == 'direct-tcpip'): m.add_string(dest_addr[0]) m.add_int(dest_addr[1]) m.add_string(src_addr[0]) m.add_int(src_addr[1]) self.channels[chanid] = chan = Channel(chanid) self.channel_events[chanid] = event = threading.Event() chan._set_transport(self) chan._set_window(self.window_size, self.max_packet_size) self._send_user_message(m) finally: self.lock.release() while 1: event.wait(0.1); if not self.active: return None if event.isSet(): break try: self.lock.acquire() if not self.channels.has_key(chanid): chan = None finally: self.lock.release() return chan def send_ignore(self, bytes=None): """ Send a junk packet across the encrypted link. This is sometimes used to add "noise" to a connection to confuse would-be attackers. It can also be used as a keep-alive for long lived connections traversing firewalls. @param bytes: the number of random bytes to send in the payload of the ignored packet -- defaults to a random number from 10 to 41. @type bytes: int @since: fearow """ m = Message() m.add_byte(chr(MSG_IGNORE)) if bytes is None: bytes = (ord(randpool.get_bytes(1)) % 32) + 10 m.add_bytes(randpool.get_bytes(bytes)) self._send_user_message(m) def renegotiate_keys(self): """ Force this session to switch to new keys. Normally this is done automatically after the session hits a certain number of packets or bytes sent or received, but this method gives you the option of forcing new keys whenever you want. Negotiating new keys causes a pause in traffic both ways as the two sides swap keys and do computations. This method returns when the session has switched to new keys, or the session has died mid-negotiation. @return: True if the renegotiation was successful, and the link is using new keys; False if the session dropped during renegotiation. @rtype: bool """ self.completion_event = threading.Event() self._send_kex_init() while 1: self.completion_event.wait(0.1); if not self.active: return False if self.completion_event.isSet(): break return True def set_keepalive(self, interval): """ Turn on/off keepalive packets (default is off). If this is set, after C{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, for example. @param interval: seconds to wait before sending a keepalive packet (or 0 to disable keepalives). @type interval: int @since: fearow """ self.keepalive_interval = interval def global_request(self, kind, data=None, wait=True): """ Make a global request to the remote host. These are normally extensions to the SSH2 protocol. @param kind: name of the request. @type kind: string @param data: an optional tuple containing additional data to attach to the request. @type data: tuple @param wait: C{True} if this method should not return until a response is received; C{False} otherwise. @type wait: bool @return: a L{Message} containing possible additional data if the request was successful (or an empty L{Message} if C{wait} was C{False}); C{None} if the request was denied. @rtype: L{Message} @since: fearow """ if wait: self.completion_event = threading.Event() m = Message() m.add_byte(chr(MSG_GLOBAL_REQUEST)) m.add_string(kind) m.add_boolean(wait) if data is not None: for item in data: m.add(item) self._log(DEBUG, 'Sending global request "%s"' % kind) self._send_user_message(m) if not wait: return True while True: self.completion_event.wait(0.1) if not self.active: return False if self.completion_event.isSet(): break return self.global_response def check_global_request(self, kind, msg): """ I{(subclass override)} Handle a global request of the given C{kind}. This method is called in server mode and client mode, whenever the remote host makes a global request. If there are any arguments to the request, they will be in C{msg}. There aren't any useful global requests defined, aside from port forwarding, so usually this type of request is an extension to the protocol. If the request was successful and you would like to return contextual data to the remote host, return a tuple. Items in the tuple will be sent back with the successful result. (Note that the items in the tuple can only be strings, ints, longs, or bools.) The default implementation always returns C{False}, indicating that it does not support any global requests. @param kind: the kind of global request being made. @type kind: string @param msg: any extra arguments to the request. @type msg: L{Message} @return: C{True} or a tuple of data if the request was granted; C{False} otherwise. @rtype: bool """ return False def accept(self, timeout=None): try: self.lock.acquire() if len(self.server_accepts) > 0: chan = self.server_accepts.pop(0) else: self.server_accept_cv.wait(timeout) if len(self.server_accepts) > 0: chan = self.server_accepts.pop(0) else: # timeout chan = None finally: self.lock.release() return chan def connect(self, hostkeytype=None, hostkey=None, username='', password=None, pkey=None): """ Negotiate an SSH2 session, and optionally verify the server's host key and authenticate using a password or private key. This is a shortcut for L{start_client}, L{get_remote_server_key}, and L{Transport.auth_password} or L{Transport.auth_publickey}. Use those methods if you want more control. You can use this method immediately after creating a Transport to negotiate encryption with a server. If it fails, an exception will be thrown. On success, the method will return cleanly, and an encrypted session exists. You may immediately call L{open_channel} or L{open_session} to get a L{Channel} object, which is used for data transfer. @note: If you fail to supply a password or private key, this method may succeed, but a subsequent L{open_channel} or L{open_session} call may fail because you haven't authenticated yet. @param hostkeytype: the type of host key expected from the server (usually C{"ssh-rsa"} or C{"ssh-dss"}), or C{None} if you don't want to do host key verification. @type hostkeytype: string @param hostkey: the host key expected from the server, or C{None} if you don't want to do host key verification. @type hostkey: string @param username: the username to authenticate as. @type username: string @param password: a password to use for authentication, if you want to use password authentication; otherwise C{None}. @type password: string @param pkey: a private key to use for authentication, if you want to use private key authentication; otherwise C{None}. @type pkey: L{PKey} @raise SSHException: if the SSH2 negotiation fails, the host key supplied by the server is incorrect, or authentication fails. @since: doduo """ if hostkeytype is not None: self.preferred_keys = [ hostkeytype ] event = threading.Event() self.start_client(event) while 1: event.wait(0.1) if not self.active: e = self.saved_exception self.saved_exception = None if e is not None: raise e raise SSHException('Negotiation failed.') if event.isSet(): break # check host key if we were given one if (hostkeytype is not None) and (hostkey is not None): key = self.get_remote_server_key() if (key.get_name() != hostkeytype) or (str(key) != hostkey): self._log(DEBUG, 'Bad host key from server') self._log(DEBUG, 'Expected: %s: %s' % (hostkeytype, repr(hostkey))) self._log(DEBUG, 'Got : %s: %s' % (key.get_name(), repr(str(key)))) raise SSHException('Bad host key from server') self._log(DEBUG, 'Host key verified (%s)' % hostkeytype) if (pkey is not None) or (password is not None): event.clear() if password is not None: self._log(DEBUG, 'Attempting password auth...') self.auth_password(username, password, event) else: self._log(DEBUG, 'Attempting pkey auth...') self.auth_publickey(username, pkey, event) while 1: event.wait(0.1) if not self.active: e = self.saved_exception self.saved_exception = None if e is not None: raise e raise SSHException('Authentication failed.') if event.isSet(): break if not self.is_authenticated(): raise SSHException('Authentication failed.') return ### internals... def _log(self, level, msg): if type(msg) == type([]): for m in msg: self.logger.log(level, m) else: self.logger.log(level, msg) def _get_modulus_pack(self): "used by KexGex to find primes for group exchange" return self._modulus_pack def _unlink_channel(self, chanid): "used by a Channel to remove itself from the active channel list" try: self.lock.acquire() if self.channels.has_key(chanid): del self.channels[chanid] finally: self.lock.release() def _check_keepalive(self): if (not self.keepalive_interval) or (not self.initial_kex_done): return now = time.time() if now > self.keepalive_last + self.keepalive_interval: self.global_request('keepalive@lag.net', wait=False) def _py22_read_all(self, n): out = '' while n > 0: r, w, e = select.select([self.sock], [], [], 0.1) if self.sock not in r: if not self.active: raise EOFError() self._check_keepalive() else: x = self.sock.recv(n) if len(x) == 0: raise EOFError() out += x n -= len(x) return out def _read_all(self, n): if PY22: return self._py22_read_all(n) out = '' while n > 0: try: x = self.sock.recv(n) if len(x) == 0: raise EOFError() out += x n -= len(x) except socket.timeout: if not self.active: raise EOFError() self._check_keepalive() return out def _write_all(self, out): self.keepalive_last = time.time() while len(out) > 0: try: n = self.sock.send(out) except: # could be: (32, 'Broken pipe') n = -1 if n < 0: raise EOFError() if n == len(out): return out = out[n:] return def _build_packet(self, payload): # pad up at least 4 bytes, to nearest block-size (usually 8) bsize = self.block_size_out padding = 3 + bsize - ((len(payload) + 8) % bsize) packet = struct.pack('>I', len(payload) + padding + 1) packet += chr(padding) packet += payload packet += randpool.get_bytes(padding) return packet def _send_message(self, data): # FIXME: should we check for rekeying here too? # encrypt this sucka data = str(data) self._log(DEBUG, 'Write packet $%x, length %d' % (ord(data[0]), len(data))) packet = self._build_packet(data) if self.ultra_debug: self._log(DEBUG, util.format_binary(packet, 'OUT: ')) if self.engine_out != None: out = self.engine_out.encrypt(packet) else: out = packet # + mac try: self.write_lock.acquire() if self.engine_out != None: payload = struct.pack('>I', self.sequence_number_out) + packet out += HMAC.HMAC(self.mac_key_out, payload, self.local_mac_engine).digest()[:self.local_mac_len] self.sequence_number_out += 1L self.sequence_number_out %= 0x100000000L self._write_all(out) self.sent_bytes += len(out) self.sent_packets += 1 if ((self.sent_packets >= self.REKEY_PACKETS) or (self.sent_bytes >= self.REKEY_BYTES)) \ and (self.local_kex_init is None): # only ask once for rekeying self._log(DEBUG, 'Rekeying (hit %d packets, %d bytes sent)' % (self.sent_packets, self.sent_bytes)) self.received_packets_overflow = 0 self._send_kex_init() finally: self.write_lock.release() def _send_user_message(self, data): """ send a message, but block if we're in key negotiation. this is used for user-initiated requests. """ while 1: self.clear_to_send.wait(0.1) if not self.active: self._log(DEBUG, 'Dropping user packet because connection is dead.') return if self.clear_to_send.isSet(): break self._send_message(data) def _read_message(self): "only one thread will ever be in this function" header = self._read_all(self.block_size_in) if self.engine_in != None: header = self.engine_in.decrypt(header) if self.ultra_debug: self._log(DEBUG, util.format_binary(header, 'IN: ')); packet_size = struct.unpack('>I', header[:4])[0] # leftover contains decrypted bytes from the first block (after the length field) leftover = header[4:] if (packet_size - len(leftover)) % self.block_size_in != 0: raise SSHException('Invalid packet blocking') buffer = self._read_all(packet_size + self.remote_mac_len - len(leftover)) packet = buffer[:packet_size - len(leftover)] post_packet = buffer[packet_size - len(leftover):] if self.engine_in != None: packet = self.engine_in.decrypt(packet) if self.ultra_debug: self._log(DEBUG, util.format_binary(packet, 'IN: ')); packet = leftover + packet if self.remote_mac_len > 0: mac = post_packet[:self.remote_mac_len] mac_payload = struct.pack('>II', self.sequence_number_in, packet_size) + packet my_mac = HMAC.HMAC(self.mac_key_in, mac_payload, self.remote_mac_engine).digest()[:self.remote_mac_len] if my_mac != mac: raise SSHException('Mismatched MAC') padding = ord(packet[0]) payload = packet[1:packet_size - padding + 1] randpool.add_event(packet[packet_size - padding + 1]) if self.ultra_debug: self._log(DEBUG, 'Got payload (%d bytes, %d padding)' % (packet_size, padding)) msg = Message(payload[1:]) msg.seqno = self.sequence_number_in self.sequence_number_in = (self.sequence_number_in + 1) & 0xffffffffL # check for rekey self.received_bytes += packet_size + self.remote_mac_len + 4 self.received_packets += 1 if self.local_kex_init is not None: # we've asked to rekey -- give them 20 packets to comply before # dropping the connection self.received_packets_overflow += 1 if self.received_packets_overflow >= 20: raise SSHException('Remote transport is ignoring rekey requests') elif (self.received_packets >= self.REKEY_PACKETS) or \ (self.received_bytes >= self.REKEY_BYTES): # only ask once for rekeying self._log(DEBUG, 'Rekeying (hit %d packets, %d bytes received)' % (self.received_packets, self.received_bytes)) self.received_packets_overflow = 0 self._send_kex_init() cmd = ord(payload[0]) self._log(DEBUG, 'Read packet $%x, length %d' % (cmd, len(payload))) return cmd, msg def _set_K_H(self, k, h): "used by a kex object to set the K (root key) and H (exchange hash)" self.K = k self.H = h if self.session_id == None: self.session_id = h def _expect_packet(self, type): "used by a kex object to register the next packet type it expects to see" self.expected_packet = type def _key_from_blob(self, keytype, keyblob): if keytype == 'ssh-rsa': return RSAKey(Message(keyblob)) elif keytype == 'ssh-dss': return DSSKey(Message(keyblob)) else: return None def _verify_key(self, host_key, sig): key = self._key_from_blob(self.host_key_type, host_key) if (key == None) or not key.valid: raise SSHException('Unknown host key type') if not key.verify_ssh_sig(self.H, Message(sig)): raise SSHException('Signature verification (%s) failed. Boo. Robey should debug this.' % self.host_key_type) self.host_key = key def _compute_key(self, id, nbytes): "id is 'A' - 'F' for the various keys used by ssh" m = Message() m.add_mpint(self.K) m.add_bytes(self.H) m.add_byte(id) m.add_bytes(self.session_id) out = sofar = SHA.new(str(m)).digest() while len(out) < nbytes: m = Message() m.add_mpint(self.K) m.add_bytes(self.H) m.add_bytes(sofar) hash = SHA.new(str(m)).digest() out += hash sofar += hash return out[:nbytes] def _get_cipher(self, name, key, iv): if not self._cipher_info.has_key(name): raise SSHException('Unknown client cipher ' + name) return self._cipher_info[name]['class'].new(key, self._cipher_info[name]['mode'], iv) def _run(self): self.active = True _active_threads.append(self) try: # SSH-1.99-OpenSSH_2.9p2 self._write_all(self.local_version + '\r\n') self._check_banner() self._send_kex_init() self.expected_packet = MSG_KEXINIT while self.active: ptype, m = self._read_message() if ptype == MSG_IGNORE: continue elif ptype == MSG_DISCONNECT: self._parse_disconnect(m) self.active = False break elif ptype == MSG_DEBUG: self._parse_debug(m) continue if self.expected_packet != 0: if ptype != self.expected_packet: raise SSHException('Expecting packet %d, got %d' % (self.expected_packet, ptype)) self.expected_packet = 0 if (ptype >= 30) and (ptype <= 39): self.kex_engine.parse_next(ptype, m) continue if self._handler_table.has_key(ptype): self._handler_table[ptype](self, m) elif self._channel_handler_table.has_key(ptype): chanid = m.get_int() if self.channels.has_key(chanid): self._channel_handler_table[ptype](self.channels[chanid], m) else: self._log(WARNING, 'Oops, unhandled type %d' % ptype) msg = Message() msg.add_byte(chr(MSG_UNIMPLEMENTED)) msg.add_int(m.seqno) self._send_message(msg) except SSHException, e: self._log(ERROR, 'Exception: ' + str(e)) self._log(ERROR, util.tb_strings()) self.saved_exception = e except EOFError, e: self._log(DEBUG, 'EOF in transport thread') #self._log(DEBUG, util.tb_strings()) self.saved_exception = e except Exception, e: self._log(ERROR, 'Unknown exception: ' + str(e)) self._log(ERROR, util.tb_strings()) self.saved_exception = e _active_threads.remove(self) for chan in self.channels.values(): chan._unlink() if self.active: self.active = False if self.completion_event != None: self.completion_event.set() if self.auth_event != None: self.auth_event.set() for event in self.channel_events.values(): event.set() self.sock.close() ### protocol stages def _negotiate_keys(self, m): # throws SSHException on anything unusual self.clear_to_send.clear() if self.local_kex_init == None: # remote side wants to renegotiate self._send_kex_init() self._parse_kex_init(m) self.kex_engine.start_kex() def _check_banner(self): # this is slow, but we only have to do it once for i in range(5): buffer = '' while not '\n' in buffer: buffer += self._read_all(1) buffer = buffer[:-1] if (len(buffer) > 0) and (buffer[-1] == '\r'): buffer = buffer[:-1] if buffer[:4] == 'SSH-': break self._log(DEBUG, 'Banner: ' + buffer) if buffer[:4] != 'SSH-': raise SSHException('Indecipherable protocol version "' + buffer + '"') # save this server version string for later self.remote_version = buffer # pull off any attached comment comment = '' i = string.find(buffer, ' ') if i >= 0: comment = buffer[i+1:] buffer = buffer[:i] # parse out version string and make sure it matches segs = buffer.split('-', 2) if len(segs) < 3: raise SSHException('Invalid SSH banner') version = segs[1] client = segs[2] if version != '1.99' and version != '2.0': raise SSHException('Incompatible version (%s instead of 2.0)' % (version,)) self._log(INFO, 'Connected (version %s, client %s)' % (version, client)) def _send_kex_init(self): """ announce to the other side that we'd like to negotiate keys, and what kind of key negotiation we support. """ self.clear_to_send.clear() if self.server_mode: if (self._modulus_pack is None) and ('diffie-hellman-group-exchange-sha1' in self.preferred_kex): # can't do group-exchange if we don't have a pack of potential primes self.preferred_kex.remove('diffie-hellman-group-exchange-sha1') available_server_keys = filter(self.server_key_dict.keys().__contains__, self.preferred_keys) else: available_server_keys = self.preferred_keys m = Message() m.add_byte(chr(MSG_KEXINIT)) m.add_bytes(randpool.get_bytes(16)) m.add(','.join(self.preferred_kex)) m.add(','.join(available_server_keys)) m.add(','.join(self.preferred_ciphers)) m.add(','.join(self.preferred_ciphers)) m.add(','.join(self.preferred_macs)) m.add(','.join(self.preferred_macs)) m.add('none') m.add('none') m.add('') m.add('') m.add_boolean(0) m.add_int(0) # save a copy for later (needed to compute a hash) self.local_kex_init = str(m) self._send_message(m) def _parse_kex_init(self, m): # reset counters of when to re-key, since we are now re-keying self.received_bytes = 0 self.received_packets = 0 self.received_packets_overflow = 0 self.sent_bytes = 0 self.sent_packets = 0 cookie = m.get_bytes(16) kex_algo_list = m.get_list() server_key_algo_list = m.get_list() client_encrypt_algo_list = m.get_list() server_encrypt_algo_list = m.get_list() client_mac_algo_list = m.get_list() server_mac_algo_list = m.get_list() client_compress_algo_list = m.get_list() server_compress_algo_list = m.get_list() client_lang_list = m.get_list() server_lang_list = m.get_list() kex_follows = m.get_boolean() unused = m.get_int() # no compression support (yet?) if (not('none' in client_compress_algo_list) or not('none' in server_compress_algo_list)): raise SSHException('Incompatible ssh peer.') # as a server, we pick the first item in the client's list that we support. # as a client, we pick the first item in our list that the server supports. if self.server_mode: agreed_kex = filter(self.preferred_kex.__contains__, kex_algo_list) else: agreed_kex = filter(kex_algo_list.__contains__, self.preferred_kex) if len(agreed_kex) == 0: raise SSHException('Incompatible ssh peer (no acceptable kex algorithm)') self.kex_engine = self._kex_info[agreed_kex[0]](self) if self.server_mode: available_server_keys = filter(self.server_key_dict.keys().__contains__, self.preferred_keys) agreed_keys = filter(available_server_keys.__contains__, server_key_algo_list) else: agreed_keys = filter(server_key_algo_list.__contains__, self.preferred_keys) if len(agreed_keys) == 0: raise SSHException('Incompatible ssh peer (no acceptable host key)') self.host_key_type = agreed_keys[0] if self.server_mode and (self.get_server_key() is None): raise SSHException('Incompatible ssh peer (can\'t match requested host key type)') if self.server_mode: agreed_local_ciphers = filter(self.preferred_ciphers.__contains__, server_encrypt_algo_list) agreed_remote_ciphers = filter(self.preferred_ciphers.__contains__, client_encrypt_algo_list) else: agreed_local_ciphers = filter(client_encrypt_algo_list.__contains__, self.preferred_ciphers) agreed_remote_ciphers = filter(server_encrypt_algo_list.__contains__, self.preferred_ciphers) if (len(agreed_local_ciphers) == 0) or (len(agreed_remote_ciphers) == 0): raise SSHException('Incompatible ssh server (no acceptable ciphers)') self.local_cipher = agreed_local_ciphers[0] self.remote_cipher = agreed_remote_ciphers[0] self._log(DEBUG, 'Ciphers agreed: local=%s, remote=%s' % (self.local_cipher, self.remote_cipher)) if self.server_mode: agreed_remote_macs = filter(self.preferred_macs.__contains__, client_mac_algo_list) agreed_local_macs = filter(self.preferred_macs.__contains__, server_mac_algo_list) else: agreed_local_macs = filter(client_mac_algo_list.__contains__, self.preferred_macs) agreed_remote_macs = filter(server_mac_algo_list.__contains__, self.preferred_macs) if (len(agreed_local_macs) == 0) or (len(agreed_remote_macs) == 0): raise SSHException('Incompatible ssh server (no acceptable macs)') self.local_mac = agreed_local_macs[0] self.remote_mac = agreed_remote_macs[0] self._log(DEBUG, 'kex algos:' + str(kex_algo_list) + ' server key:' + str(server_key_algo_list) + \ ' client encrypt:' + str(client_encrypt_algo_list) + \ ' server encrypt:' + str(server_encrypt_algo_list) + \ ' client mac:' + str(client_mac_algo_list) + \ ' server mac:' + str(server_mac_algo_list) + \ ' client compress:' + str(client_compress_algo_list) + \ ' server compress:' + str(server_compress_algo_list) + \ ' client lang:' + str(client_lang_list) + \ ' server lang:' + str(server_lang_list) + \ ' kex follows?' + str(kex_follows)) self._log(DEBUG, 'using kex %s; server key type %s; cipher: local %s, remote %s; mac: local %s, remote %s' % (agreed_kex[0], self.host_key_type, self.local_cipher, self.remote_cipher, self.local_mac, self.remote_mac)) # save for computing hash later... # now wait! openssh has a bug (and others might too) where there are # actually some extra bytes (one NUL byte in openssh's case) added to # the end of the packet but not parsed. turns out we need to throw # away those bytes because they aren't part of the hash. self.remote_kex_init = chr(MSG_KEXINIT) + m.get_so_far() def _activate_inbound(self): "switch on newly negotiated encryption parameters for inbound traffic" self.block_size_in = self._cipher_info[self.remote_cipher]['block-size'] if self.server_mode: IV_in = self._compute_key('A', self.block_size_in) key_in = self._compute_key('C', self._cipher_info[self.remote_cipher]['key-size']) else: IV_in = self._compute_key('B', self.block_size_in) key_in = self._compute_key('D', self._cipher_info[self.remote_cipher]['key-size']) self.engine_in = self._get_cipher(self.remote_cipher, key_in, IV_in) self.remote_mac_len = self._mac_info[self.remote_mac]['size'] self.remote_mac_engine = self._mac_info[self.remote_mac]['class'] # initial mac keys are done in the hash's natural size (not the potentially truncated # transmission size) if self.server_mode: self.mac_key_in = self._compute_key('E', self.remote_mac_engine.digest_size) else: self.mac_key_in = self._compute_key('F', self.remote_mac_engine.digest_size) def _activate_outbound(self): "switch on newly negotiated encryption parameters for outbound traffic" m = Message() m.add_byte(chr(MSG_NEWKEYS)) self._send_message(m) self.block_size_out = self._cipher_info[self.local_cipher]['block-size'] if self.server_mode: IV_out = self._compute_key('B', self.block_size_out) key_out = self._compute_key('D', self._cipher_info[self.local_cipher]['key-size']) else: IV_out = self._compute_key('A', self.block_size_out) key_out = self._compute_key('C', self._cipher_info[self.local_cipher]['key-size']) self.engine_out = self._get_cipher(self.local_cipher, key_out, IV_out) self.local_mac_len = self._mac_info[self.local_mac]['size'] self.local_mac_engine = self._mac_info[self.local_mac]['class'] # initial mac keys are done in the hash's natural size (not the potentially truncated # transmission size) if self.server_mode: self.mac_key_out = self._compute_key('F', self.local_mac_engine.digest_size) else: self.mac_key_out = self._compute_key('E', self.local_mac_engine.digest_size) # we always expect to receive NEWKEYS now self.expected_packet = MSG_NEWKEYS def _parse_newkeys(self, m): self._log(DEBUG, 'Switch to new keys ...') self._activate_inbound() # can also free a bunch of stuff here self.local_kex_init = self.remote_kex_init = None self.e = self.f = self.K = self.x = None if not self.initial_kex_done: # this was the first key exchange self.initial_kex_done = True # send an event? if self.completion_event != None: self.completion_event.set() # it's now okay to send data again (if this was a re-key) self.clear_to_send.set() return def _parse_disconnect(self, m): code = m.get_int() desc = m.get_string() self._log(INFO, 'Disconnect (code %d): %s' % (code, desc)) def _parse_global_request(self, m): kind = m.get_string() self._log(DEBUG, 'Received global request "%s"' % kind) want_reply = m.get_boolean() ok = self.check_global_request(kind, m) extra = () if type(ok) is tuple: extra = ok ok = True if want_reply: msg = Message() if ok: msg.add_byte(chr(MSG_REQUEST_SUCCESS)) for item in extra: msg.add(item) else: msg.add_byte(chr(MSG_REQUEST_FAILURE)) self._send_message(msg) def _parse_request_success(self, m): self._log(DEBUG, 'Global request successful.') self.global_response = m if self.completion_event is not None: self.completion_event.set() def _parse_request_failure(self, m): self._log(DEBUG, 'Global request denied.') self.global_response = None if self.completion_event is not None: self.completion_event.set() def _parse_channel_open_success(self, m): chanid = m.get_int() server_chanid = m.get_int() server_window_size = m.get_int() server_max_packet_size = m.get_int() if not self.channels.has_key(chanid): self._log(WARNING, 'Success for unrequested channel! [??]') return try: self.lock.acquire() chan = self.channels[chanid] chan._set_remote_channel(server_chanid, server_window_size, server_max_packet_size) self._log(INFO, 'Secsh channel %d opened.' % chanid) if self.channel_events.has_key(chanid): self.channel_events[chanid].set() del self.channel_events[chanid] finally: self.lock.release() return def _parse_channel_open_failure(self, m): chanid = m.get_int() reason = m.get_int() reason_str = m.get_string() lang = m.get_string() if _CONNECTION_FAILED_CODE.has_key(reason): reason_text = _CONNECTION_FAILED_CODE[reason] else: reason_text = '(unknown code)' self._log(INFO, 'Secsh channel %d open FAILED: %s: %s' % (chanid, reason_str, reason_text)) try: self.lock.aquire() if self.channels.has_key(chanid): del self.channels[chanid] if self.channel_events.has_key(chanid): self.channel_events[chanid].set() del self.channel_events[chanid] finally: self.lock.release() return def _parse_channel_open(self, m): kind = m.get_string() chanid = m.get_int() initial_window_size = m.get_int() max_packet_size = m.get_int() reject = False if not self.server_mode: self._log(DEBUG, 'Rejecting "%s" channel request from server.' % kind) reject = True reason = self.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED else: try: self.lock.acquire() my_chanid = self.channel_counter self.channel_counter += 1 finally: self.lock.release() chan = self.server_object.check_channel_request(kind, my_chanid) if (chan is None) or (type(chan) is int): self._log(DEBUG, 'Rejecting "%s" channel request from client.' % kind) reject = True if type(chan) is int: reason = chan else: reason = self.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED if reject: msg = Message() msg.add_byte(chr(MSG_CHANNEL_OPEN_FAILURE)) msg.add_int(chanid) msg.add_int(reason) msg.add_string('') msg.add_string('en') self._send_message(msg) return try: self.lock.acquire() self.channels[my_chanid] = chan chan._set_transport(self) chan._set_window(self.window_size, self.max_packet_size) chan._set_remote_channel(chanid, initial_window_size, max_packet_size) finally: self.lock.release() m = Message() m.add_byte(chr(MSG_CHANNEL_OPEN_SUCCESS)) m.add_int(chanid) m.add_int(my_chanid) m.add_int(self.window_size) m.add_int(self.max_packet_size) self._send_message(m) self._log(INFO, 'Secsh channel %d opened.' % my_chanid) try: self.lock.acquire() self.server_accepts.append(chan) self.server_accept_cv.notify() finally: self.lock.release() def _parse_debug(self, m): always_display = m.get_boolean() msg = m.get_string() lang = m.get_string() self._log(DEBUG, 'Debug msg: ' + util.safe_string(msg)) _handler_table = { MSG_NEWKEYS: _parse_newkeys, MSG_GLOBAL_REQUEST: _parse_global_request, MSG_REQUEST_SUCCESS: _parse_request_success, MSG_REQUEST_FAILURE: _parse_request_failure, MSG_CHANNEL_OPEN_SUCCESS: _parse_channel_open_success, MSG_CHANNEL_OPEN_FAILURE: _parse_channel_open_failure, MSG_CHANNEL_OPEN: _parse_channel_open, MSG_KEXINIT: _negotiate_keys, } _channel_handler_table = { MSG_CHANNEL_SUCCESS: Channel._request_success, MSG_CHANNEL_FAILURE: Channel._request_failed, MSG_CHANNEL_DATA: Channel._feed, MSG_CHANNEL_WINDOW_ADJUST: Channel._window_adjust, MSG_CHANNEL_REQUEST: Channel._handle_request, MSG_CHANNEL_EOF: Channel._handle_eof, MSG_CHANNEL_CLOSE: Channel._handle_close, } from server import ServerInterface