Current File : //usr/lib/python3/dist-packages/paramiko/transport.py
# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
#
# 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 distributed 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.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
Core protocol implementation
"""
from __future__ import print_function
import os
import socket
import sys
import threading
import time
import weakref
from hashlib import md5, sha1, sha256, sha512
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.ciphers import algorithms, Cipher, modes
import paramiko
from paramiko import util
from paramiko.auth_handler import AuthHandler
from paramiko.ssh_gss import GSSAuth
from paramiko.channel import Channel
from paramiko.common import (
xffffffff,
cMSG_CHANNEL_OPEN,
cMSG_IGNORE,
cMSG_GLOBAL_REQUEST,
DEBUG,
MSG_KEXINIT,
MSG_IGNORE,
MSG_DISCONNECT,
MSG_DEBUG,
ERROR,
WARNING,
cMSG_UNIMPLEMENTED,
INFO,
cMSG_KEXINIT,
cMSG_NEWKEYS,
MSG_NEWKEYS,
cMSG_REQUEST_SUCCESS,
cMSG_REQUEST_FAILURE,
CONNECTION_FAILED_CODE,
OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED,
OPEN_SUCCEEDED,
cMSG_CHANNEL_OPEN_FAILURE,
cMSG_CHANNEL_OPEN_SUCCESS,
MSG_GLOBAL_REQUEST,
MSG_REQUEST_SUCCESS,
MSG_REQUEST_FAILURE,
MSG_CHANNEL_OPEN_SUCCESS,
MSG_CHANNEL_OPEN_FAILURE,
MSG_CHANNEL_OPEN,
MSG_CHANNEL_SUCCESS,
MSG_CHANNEL_FAILURE,
MSG_CHANNEL_DATA,
MSG_CHANNEL_EXTENDED_DATA,
MSG_CHANNEL_WINDOW_ADJUST,
MSG_CHANNEL_REQUEST,
MSG_CHANNEL_EOF,
MSG_CHANNEL_CLOSE,
MIN_WINDOW_SIZE,
MIN_PACKET_SIZE,
MAX_WINDOW_SIZE,
DEFAULT_WINDOW_SIZE,
DEFAULT_MAX_PACKET_SIZE,
HIGHEST_USERAUTH_MESSAGE_ID,
MSG_UNIMPLEMENTED,
MSG_NAMES,
MSG_EXT_INFO,
cMSG_EXT_INFO,
)
from paramiko.compress import ZlibCompressor, ZlibDecompressor
from paramiko.dsskey import DSSKey
from paramiko.ed25519key import Ed25519Key
from paramiko.kex_curve25519 import KexCurve25519
from paramiko.kex_gex import KexGex, KexGexSHA256
from paramiko.kex_group1 import KexGroup1
from paramiko.kex_group14 import KexGroup14, KexGroup14SHA256
from paramiko.kex_group16 import KexGroup16SHA512
from paramiko.kex_ecdh_nist import KexNistp256, KexNistp384, KexNistp521
from paramiko.kex_gss import KexGSSGex, KexGSSGroup1, KexGSSGroup14
from paramiko.message import Message
from paramiko.packet import Packetizer, NeedRekeyException
from paramiko.primes import ModulusPack
from paramiko.py3compat import string_types, long, byte_ord, b, input, PY2
from paramiko.rsakey import RSAKey
from paramiko.ecdsakey import ECDSAKey
from paramiko.server import ServerInterface
from paramiko.sftp_client import SFTPClient
from paramiko.ssh_exception import (
SSHException,
BadAuthenticationType,
ChannelException,
IncompatiblePeer,
MessageOrderError,
ProxyCommandFailure,
)
from paramiko.util import retry_on_signal, ClosingContextManager, clamp_value
# for thread cleanup
_active_threads = []
def _join_lingering_threads():
for thr in _active_threads:
thr.stop_thread()
import atexit
atexit.register(_join_lingering_threads)
class Transport(threading.Thread, ClosingContextManager):
"""
An SSH Transport attaches to a stream (usually a socket), negotiates an
encrypted session, authenticates, and then creates stream tunnels, called
`channels <.Channel>`, across the session. Multiple channels can be
multiplexed across a single session (and often are, in the case of port
forwardings).
Instances of this class may be used as context managers.
"""
_ENCRYPT = object()
_DECRYPT = object()
_PROTO_ID = "2.0"
_CLIENT_ID = "paramiko_{}".format(paramiko.__version__)
# These tuples of algorithm identifiers are in preference order; do not
# reorder without reason!
# NOTE: if you need to modify these, we suggest leveraging the
# `disabled_algorithms` constructor argument (also available in SSHClient)
# instead of monkeypatching or subclassing.
_preferred_ciphers = (
"aes128-ctr",
"aes192-ctr",
"aes256-ctr",
"aes128-cbc",
"aes192-cbc",
"aes256-cbc",
"3des-cbc",
)
_preferred_macs = (
"hmac-sha2-256",
"hmac-sha2-512",
"hmac-sha2-256-etm@openssh.com",
"hmac-sha2-512-etm@openssh.com",
"hmac-sha1",
"hmac-md5",
"hmac-sha1-96",
"hmac-md5-96",
)
# ~= HostKeyAlgorithms in OpenSSH land
_preferred_keys = (
"ssh-ed25519",
"ecdsa-sha2-nistp256",
"ecdsa-sha2-nistp384",
"ecdsa-sha2-nistp521",
"rsa-sha2-512",
"rsa-sha2-256",
"ssh-rsa",
"ssh-dss",
)
# ~= PubKeyAcceptedAlgorithms
_preferred_pubkeys = (
"ssh-ed25519",
"ecdsa-sha2-nistp256",
"ecdsa-sha2-nistp384",
"ecdsa-sha2-nistp521",
"rsa-sha2-512",
"rsa-sha2-256",
"ssh-rsa",
"ssh-dss",
)
_preferred_kex = (
"ecdh-sha2-nistp256",
"ecdh-sha2-nistp384",
"ecdh-sha2-nistp521",
"diffie-hellman-group16-sha512",
"diffie-hellman-group-exchange-sha256",
"diffie-hellman-group14-sha256",
"diffie-hellman-group-exchange-sha1",
"diffie-hellman-group14-sha1",
"diffie-hellman-group1-sha1",
)
if KexCurve25519.is_available():
_preferred_kex = ("curve25519-sha256@libssh.org",) + _preferred_kex
_preferred_gsskex = (
"gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==",
"gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==",
"gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==",
)
_preferred_compression = ("none",)
_cipher_info = {
"aes128-ctr": {
"class": algorithms.AES,
"mode": modes.CTR,
"block-size": 16,
"key-size": 16,
},
"aes192-ctr": {
"class": algorithms.AES,
"mode": modes.CTR,
"block-size": 16,
"key-size": 24,
},
"aes256-ctr": {
"class": algorithms.AES,
"mode": modes.CTR,
"block-size": 16,
"key-size": 32,
},
"aes128-cbc": {
"class": algorithms.AES,
"mode": modes.CBC,
"block-size": 16,
"key-size": 16,
},
"aes192-cbc": {
"class": algorithms.AES,
"mode": modes.CBC,
"block-size": 16,
"key-size": 24,
},
"aes256-cbc": {
"class": algorithms.AES,
"mode": modes.CBC,
"block-size": 16,
"key-size": 32,
},
"3des-cbc": {
"class": algorithms.TripleDES,
"mode": modes.CBC,
"block-size": 8,
"key-size": 24,
},
}
_mac_info = {
"hmac-sha1": {"class": sha1, "size": 20},
"hmac-sha1-96": {"class": sha1, "size": 12},
"hmac-sha2-256": {"class": sha256, "size": 32},
"hmac-sha2-256-etm@openssh.com": {"class": sha256, "size": 32},
"hmac-sha2-512": {"class": sha512, "size": 64},
"hmac-sha2-512-etm@openssh.com": {"class": sha512, "size": 64},
"hmac-md5": {"class": md5, "size": 16},
"hmac-md5-96": {"class": md5, "size": 12},
}
_key_info = {
# TODO: at some point we will want to drop this as it's no longer
# considered secure due to using SHA-1 for signatures. OpenSSH 8.8 no
# longer supports it. Question becomes at what point do we want to
# prevent users with older setups from using this?
"ssh-rsa": RSAKey,
"ssh-rsa-cert-v01@openssh.com": RSAKey,
"rsa-sha2-256": RSAKey,
"rsa-sha2-256-cert-v01@openssh.com": RSAKey,
"rsa-sha2-512": RSAKey,
"rsa-sha2-512-cert-v01@openssh.com": RSAKey,
"ssh-dss": DSSKey,
"ssh-dss-cert-v01@openssh.com": DSSKey,
"ecdsa-sha2-nistp256": ECDSAKey,
"ecdsa-sha2-nistp256-cert-v01@openssh.com": ECDSAKey,
"ecdsa-sha2-nistp384": ECDSAKey,
"ecdsa-sha2-nistp384-cert-v01@openssh.com": ECDSAKey,
"ecdsa-sha2-nistp521": ECDSAKey,
"ecdsa-sha2-nistp521-cert-v01@openssh.com": ECDSAKey,
"ssh-ed25519": Ed25519Key,
"ssh-ed25519-cert-v01@openssh.com": Ed25519Key,
}
_kex_info = {
"diffie-hellman-group1-sha1": KexGroup1,
"diffie-hellman-group14-sha1": KexGroup14,
"diffie-hellman-group-exchange-sha1": KexGex,
"diffie-hellman-group-exchange-sha256": KexGexSHA256,
"diffie-hellman-group14-sha256": KexGroup14SHA256,
"diffie-hellman-group16-sha512": KexGroup16SHA512,
"gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==": KexGSSGroup1,
"gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==": KexGSSGroup14,
"gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==": KexGSSGex,
"ecdh-sha2-nistp256": KexNistp256,
"ecdh-sha2-nistp384": KexNistp384,
"ecdh-sha2-nistp521": KexNistp521,
}
if KexCurve25519.is_available():
_kex_info["curve25519-sha256@libssh.org"] = KexCurve25519
_compression_info = {
# zlib@openssh.com is just zlib, but only turned on after a successful
# authentication. openssh servers may only offer this type because
# they've had troubles with security holes in zlib in the past.
"zlib@openssh.com": (ZlibCompressor, ZlibDecompressor),
"zlib": (ZlibCompressor, ZlibDecompressor),
"none": (None, None),
}
_modulus_pack = None
_active_check_timeout = 0.1
def __init__(
self,
sock,
default_window_size=DEFAULT_WINDOW_SIZE,
default_max_packet_size=DEFAULT_MAX_PACKET_SIZE,
gss_kex=False,
gss_deleg_creds=True,
disabled_algorithms=None,
server_sig_algs=True,
strict_kex=True,
packetizer_class=None,
):
"""
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 `connect` or `start_client` to begin a client
session, or `start_server` to begin a server session.
If the object is not actually a socket, it must have the following
methods:
- ``send(str)``: Writes from 1 to ``len(str)`` bytes, and returns an
int representing the number of bytes written. Returns
0 or raises ``EOFError`` if the stream has been closed.
- ``recv(int)``: Reads from 1 to ``int`` bytes and returns them as a
string. Returns 0 or raises ``EOFError`` if the stream has been
closed.
- ``close()``: Closes the socket.
- ``settimeout(n)``: Sets a (float) timeout on I/O operations.
For ease of use, you may also pass in an address (as a tuple) or a host
string as the ``sock`` argument. (A host string is a hostname with an
optional port (separated by ``":"``) which will be converted into a
tuple of ``(hostname, port)``.) A socket will be connected to this
address and used for communication. Exceptions from the ``socket``
call may be thrown in this case.
.. note::
Modifying the the window and packet sizes might have adverse
effects on your channels created from this transport. The default
values are the same as in the OpenSSH code base and have been
battle tested.
:param socket sock:
a socket or socket-like object to create the session over.
:param int default_window_size:
sets the default window size on the transport. (defaults to
2097152)
:param int default_max_packet_size:
sets the default max packet size on the transport. (defaults to
32768)
:param bool gss_kex:
Whether to enable GSSAPI key exchange when GSSAPI is in play.
Default: ``False``.
:param bool gss_deleg_creds:
Whether to enable GSSAPI credential delegation when GSSAPI is in
play. Default: ``True``.
:param dict disabled_algorithms:
If given, must be a dictionary mapping algorithm type to an
iterable of algorithm identifiers, which will be disabled for the
lifetime of the transport.
Keys should match the last word in the class' builtin algorithm
tuple attributes, such as ``"ciphers"`` to disable names within
``_preferred_ciphers``; or ``"kex"`` to disable something defined
inside ``_preferred_kex``. Values should exactly match members of
the matching attribute.
For example, if you need to disable
``diffie-hellman-group16-sha512`` key exchange (perhaps because
your code talks to a server which implements it differently from
Paramiko), specify ``disabled_algorithms={"kex":
["diffie-hellman-group16-sha512"]}``.
:param bool server_sig_algs:
Whether to send an extra message to compatible clients, in server
mode, with a list of supported pubkey algorithms. Default:
``True``.
:param bool strict_kex:
Whether to advertise (and implement, if client also advertises
support for) a "strict kex" mode for safer handshaking. Default:
``True``.
:param packetizer_class:
Which class to use for instantiating the internal packet handler.
Default: ``None`` (i.e.: use `Packetizer` as normal).
.. versionchanged:: 1.15
Added the ``default_window_size`` and ``default_max_packet_size``
arguments.
.. versionchanged:: 1.15
Added the ``gss_kex`` and ``gss_deleg_creds`` kwargs.
.. versionchanged:: 2.6
Added the ``disabled_algorithms`` kwarg.
.. versionchanged:: 2.9
Added the ``server_sig_algs`` kwarg.
.. versionchanged:: 3.4
Added the ``strict_kex`` kwarg.
.. versionchanged:: 3.4
Added the ``packetizer_class`` kwarg.
"""
self.active = False
self.hostname = None
self.server_extensions = {}
self.advertise_strict_kex = strict_kex
self.agreed_on_strict_kex = False
if isinstance(sock, string_types):
# convert "host:port" into (host, port)
hl = sock.split(":", 1)
self.hostname = hl[0]
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
self.hostname = hostname
reason = "No suitable address family"
addrinfos = socket.getaddrinfo(
hostname, port, socket.AF_UNSPEC, socket.SOCK_STREAM
)
for family, socktype, proto, canonname, sockaddr in addrinfos:
if socktype == socket.SOCK_STREAM:
af = family
# addr = sockaddr
sock = socket.socket(af, socket.SOCK_STREAM)
try:
retry_on_signal(lambda: sock.connect((hostname, port)))
except socket.error as e:
reason = str(e)
else:
break
else:
raise SSHException(
"Unable to connect to {}: {}".format(hostname, reason)
)
# okay, normal socket-ish flow here...
threading.Thread.__init__(self)
self.daemon = True
self.sock = sock
# 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(self._active_check_timeout)
# negotiated crypto parameters
self.packetizer = (packetizer_class or Packetizer)(sock)
self.local_version = "SSH-" + self._PROTO_ID + "-" + self._CLIENT_ID
self.remote_version = ""
self.local_cipher = self.remote_cipher = ""
self.local_kex_init = self.remote_kex_init = None
self.local_mac = self.remote_mac = None
self.local_compression = self.remote_compression = None
self.session_id = None
self.host_key_type = None
self.host_key = None
# GSS-API / SSPI Key Exchange
self.use_gss_kex = gss_kex
# This will be set to True if GSS-API Key Exchange was performed
self.gss_kex_used = False
self.kexgss_ctxt = None
self.gss_host = None
if self.use_gss_kex:
self.kexgss_ctxt = GSSAuth("gssapi-keyex", gss_deleg_creds)
self._preferred_kex = self._preferred_gsskex + self._preferred_kex
# state used during negotiation
self.kex_engine = None
self.H = None
self.K = None
self.initial_kex_done = False
self.in_kex = False
self.authenticated = False
self._expected_packet = tuple()
# synchronization (always higher level than write_lock)
self.lock = threading.Lock()
# tracking open channels
self._channels = ChannelMap()
self.channel_events = {} # (id -> Event)
self.channels_seen = {} # (id -> True)
self._channel_counter = 0
self.default_max_packet_size = default_max_packet_size
self.default_window_size = default_window_size
self._forward_agent_handler = None
self._x11_handler = None
self._tcp_handler = None
self.saved_exception = None
self.clear_to_send = threading.Event()
self.clear_to_send_lock = threading.Lock()
self.clear_to_send_timeout = 30.0
self.log_name = "paramiko.transport"
self.logger = util.get_logger(self.log_name)
self.packetizer.set_log(self.logger)
self.auth_handler = None
# response Message from an arbitrary global request
self.global_response = None
# user-defined event callbacks
self.completion_event = None
# how long (seconds) to wait for the SSH banner
self.banner_timeout = 15
# how long (seconds) to wait for the handshake to finish after SSH
# banner sent.
self.handshake_timeout = 15
# how long (seconds) to wait for the auth response.
self.auth_timeout = 30
self.disabled_algorithms = disabled_algorithms or {}
self.server_sig_algs = server_sig_algs
# server mode:
self.server_mode = False
self.server_object = None
self.server_key_dict = {}
self.server_accepts = []
self.server_accept_cv = threading.Condition(self.lock)
self.subsystem_table = {}
# Handler table, now set at init time for easier per-instance
# manipulation and subclass twiddling.
self._handler_table = {
MSG_EXT_INFO: self._parse_ext_info,
MSG_NEWKEYS: self._parse_newkeys,
MSG_GLOBAL_REQUEST: self._parse_global_request,
MSG_REQUEST_SUCCESS: self._parse_request_success,
MSG_REQUEST_FAILURE: self._parse_request_failure,
MSG_CHANNEL_OPEN_SUCCESS: self._parse_channel_open_success,
MSG_CHANNEL_OPEN_FAILURE: self._parse_channel_open_failure,
MSG_CHANNEL_OPEN: self._parse_channel_open,
MSG_KEXINIT: self._negotiate_keys,
}
def _filter_algorithm(self, type_):
default = getattr(self, "_preferred_{}".format(type_))
return tuple(
x
for x in default
if x not in self.disabled_algorithms.get(type_, [])
)
@property
def preferred_ciphers(self):
return self._filter_algorithm("ciphers")
@property
def preferred_macs(self):
return self._filter_algorithm("macs")
@property
def preferred_keys(self):
# Interleave cert variants here; resistant to various background
# overwriting of _preferred_keys, and necessary as hostkeys can't use
# the logic pubkey auth does re: injecting/checking for certs at
# runtime
filtered = self._filter_algorithm("keys")
return tuple(
filtered
+ tuple("{}-cert-v01@openssh.com".format(x) for x in filtered)
)
@property
def preferred_pubkeys(self):
return self._filter_algorithm("pubkeys")
@property
def preferred_kex(self):
return self._filter_algorithm("kex")
@property
def preferred_compression(self):
return self._filter_algorithm("compression")
def __repr__(self):
"""
Returns a string representation of this object, for debugging.
"""
id_ = hex(long(id(self)) & xffffffff)
out = "<paramiko.Transport at {}".format(id_)
if not self.active:
out += " (unconnected)"
else:
if self.local_cipher != "":
out += " (cipher {}, {:d} bits)".format(
self.local_cipher,
self._cipher_info[self.local_cipher]["key-size"] * 8,
)
if self.is_authenticated():
out += " (active; {} open channel(s))".format(
len(self._channels)
)
elif self.initial_kex_done:
out += " (connected; awaiting auth)"
else:
out += " (connecting)"
out += ">"
return out
def atfork(self):
"""
Terminate this Transport without closing the session. On posix
systems, if a Transport is open during process forking, both parent
and child will share the underlying socket, but only one process can
use the connection (without corrupting the session). Use this method
to clean up a Transport object without disrupting the other process.
.. versionadded:: 1.5.3
"""
self.sock.close()
self.close()
def get_security_options(self):
"""
Return a `.SecurityOptions` object which can be used to tweak the
encryption algorithms this transport will permit (for encryption,
digest/hash operations, public keys, and key exchanges) and the order
of preference for them.
"""
return SecurityOptions(self)
def set_gss_host(self, gss_host, trust_dns=True, gssapi_requested=True):
"""
Normalize/canonicalize ``self.gss_host`` depending on various factors.
:param str gss_host:
The explicitly requested GSS-oriented hostname to connect to (i.e.
what the host's name is in the Kerberos database.) Defaults to
``self.hostname`` (which will be the 'real' target hostname and/or
host portion of given socket object.)
:param bool trust_dns:
Indicates whether or not DNS is trusted; if true, DNS will be used
to canonicalize the GSS hostname (which again will either be
``gss_host`` or the transport's default hostname.)
(Defaults to True due to backwards compatibility.)
:param bool gssapi_requested:
Whether GSSAPI key exchange or authentication was even requested.
If not, this is a no-op and nothing happens
(and ``self.gss_host`` is not set.)
(Defaults to True due to backwards compatibility.)
:returns: ``None``.
"""
# No GSSAPI in play == nothing to do
if not gssapi_requested:
return
# Obtain the correct host first - did user request a GSS-specific name
# to use that is distinct from the actual SSH target hostname?
if gss_host is None:
gss_host = self.hostname
# Finally, canonicalize via DNS if DNS is trusted.
if trust_dns and gss_host is not None:
gss_host = socket.getfqdn(gss_host)
# And set attribute for reference later.
self.gss_host = gss_host
def start_client(self, event=None, timeout=None):
"""
Negotiate a new SSH2 session as a client. This is the first step after
creating a new `.Transport`. A separate thread is created for protocol
negotiation.
If an event is passed in, this method returns immediately. When
negotiation is done (successful or not), the given ``Event`` will
be triggered. On failure, `is_active` will return ``False``.
(Since 1.4) If ``event`` is ``None``, this method will not return until
negotiation is done. On success, the method returns normally.
Otherwise an SSHException is raised.
After a successful negotiation, you will usually want to authenticate,
calling `auth_password <Transport.auth_password>` or
`auth_publickey <Transport.auth_publickey>`.
.. note:: `connect` is a simpler method for connecting as a client.
.. note::
After calling this method (or `start_server` or `connect`), you
should no longer directly read from or write to the original socket
object.
:param .threading.Event event:
an event to trigger when negotiation is complete (optional)
:param float timeout:
a timeout, in seconds, for SSH2 session negotiation (optional)
:raises:
`.SSHException` -- if negotiation fails (and no ``event`` was
passed in)
"""
self.active = True
if event is not None:
# async, return immediately and let the app poll for completion
self.completion_event = event
self.start()
return
# synchronous, wait for a result
self.completion_event = event = threading.Event()
self.start()
max_time = time.time() + timeout if timeout is not None else None
while True:
event.wait(0.1)
if not self.active:
e = self.get_exception()
if e is not None:
raise e
raise SSHException("Negotiation failed.")
if event.is_set() or (
timeout is not None and time.time() >= max_time
):
break
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 `.Transport` and setting up your server host key(s). A
separate thread is created for protocol negotiation.
If an event is passed in, this method returns immediately. When
negotiation is done (successful or not), the given ``Event`` will
be triggered. On failure, `is_active` will return ``False``.
(Since 1.4) If ``event`` is ``None``, this method will not return until
negotiation is done. On success, the method returns normally.
Otherwise an SSHException is raised.
After a successful negotiation, the client will need to authenticate.
Override the methods `get_allowed_auths
<.ServerInterface.get_allowed_auths>`, `check_auth_none
<.ServerInterface.check_auth_none>`, `check_auth_password
<.ServerInterface.check_auth_password>`, and `check_auth_publickey
<.ServerInterface.check_auth_publickey>` in the given ``server`` object
to control the authentication process.
After a successful authentication, the client should request to open a
channel. Override `check_channel_request
<.ServerInterface.check_channel_request>` in the given ``server``
object to allow channels to be opened.
.. note::
After calling this method (or `start_client` or `connect`), you
should no longer directly read from or write to the original socket
object.
:param .threading.Event event:
an event to trigger when negotiation is complete.
:param .ServerInterface server:
an object used to perform authentication and create `channels
<.Channel>`
:raises:
`.SSHException` -- if negotiation fails (and no ``event`` was
passed in)
"""
if server is None:
server = ServerInterface()
self.server_mode = True
self.server_object = server
self.active = True
if event is not None:
# async, return immediately and let the app poll for completion
self.completion_event = event
self.start()
return
# synchronous, wait for a result
self.completion_event = event = threading.Event()
self.start()
while True:
event.wait(0.1)
if not self.active:
e = self.get_exception()
if e is not None:
raise e
raise SSHException("Negotiation failed.")
if event.is_set():
break
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. Only one key of each type (RSA or
DSS) is kept.
:param .PKey key:
the host key to add, usually an `.RSAKey` or `.DSSKey`.
"""
self.server_key_dict[key.get_name()] = key
# Handle SHA-2 extensions for RSA by ensuring that lookups into
# self.server_key_dict will yield this key for any of the algorithm
# names.
if isinstance(key, RSAKey):
self.server_key_dict["rsa-sha2-256"] = key
self.server_key_dict["rsa-sha2-512"] = 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 `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, ``None`` is returned. In client mode, the behavior is undefined.
:return:
host key (`.PKey`) of the type negotiated by the client, or
``None``.
"""
try:
return self.server_key_dict[self.host_key_type]
except KeyError:
pass
return None
@staticmethod
def load_server_moduli(filename=None):
"""
(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 ``/etc/ssh/moduli``).
If you call `load_server_moduli` and it returns ``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 str filename:
optional path to the moduli file, if you happen to know that it's
not in a standard location.
:return:
True if a moduli file was successfully loaded; False otherwise.
.. note:: This has no effect when used in client mode.
"""
Transport._modulus_pack = ModulusPack()
# 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:
Transport._modulus_pack.read_file(fn)
return True
except IOError:
pass
# none succeeded
Transport._modulus_pack = None
return False
def close(self):
"""
Close this session, and any open channels that are tied to it.
"""
if not self.active:
return
self.stop_thread()
for chan in list(self._channels.values()):
chan._unlink()
self.sock.close()
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 `.PKey.get_name`
for the key type, and ``str(key)`` for the key string.
:raises: `.SSHException` -- if no session is currently active.
:return: public key (`.PKey`) of the remote server
"""
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
"""
return self.active
def open_session(
self, window_size=None, max_packet_size=None, timeout=None
):
"""
Request a new channel to the server, of type ``"session"``. This is
just an alias for calling `open_channel` with an argument of
``"session"``.
.. note:: Modifying the the window and packet sizes might have adverse
effects on the session created. The default values are the same
as in the OpenSSH code base and have been battle tested.
:param int window_size:
optional window size for this session.
:param int max_packet_size:
optional max packet size for this session.
:return: a new `.Channel`
:raises:
`.SSHException` -- if the request is rejected or the session ends
prematurely
.. versionchanged:: 1.13.4/1.14.3/1.15.3
Added the ``timeout`` argument.
.. versionchanged:: 1.15
Added the ``window_size`` and ``max_packet_size`` arguments.
"""
return self.open_channel(
"session",
window_size=window_size,
max_packet_size=max_packet_size,
timeout=timeout,
)
def open_x11_channel(self, src_addr=None):
"""
Request a new channel to the client, of type ``"x11"``. This
is just an alias for ``open_channel('x11', src_addr=src_addr)``.
:param tuple src_addr:
the source address (``(str, int)``) of the x11 server (port is the
x11 port, ie. 6010)
:return: a new `.Channel`
:raises:
`.SSHException` -- if the request is rejected or the session ends
prematurely
"""
return self.open_channel("x11", src_addr=src_addr)
def open_forward_agent_channel(self):
"""
Request a new channel to the client, of type
``"auth-agent@openssh.com"``.
This is just an alias for ``open_channel('auth-agent@openssh.com')``.
:return: a new `.Channel`
:raises: `.SSHException` --
if the request is rejected or the session ends prematurely
"""
return self.open_channel("auth-agent@openssh.com")
def open_forwarded_tcpip_channel(self, src_addr, dest_addr):
"""
Request a new channel back to the client, of type ``forwarded-tcpip``.
This is used after a client has requested port forwarding, for sending
incoming connections back to the client.
:param src_addr: originator's address
:param dest_addr: local (server) connected address
"""
return self.open_channel("forwarded-tcpip", dest_addr, src_addr)
def open_channel(
self,
kind,
dest_addr=None,
src_addr=None,
window_size=None,
max_packet_size=None,
timeout=None,
):
"""
Request a new channel to the server. `Channels <.Channel>` are
socket-like objects used for the actual transfer of data across the
session. You may only request a channel after negotiating encryption
(using `connect` or `start_client`) and authenticating.
.. note:: Modifying the the window and packet sizes might have adverse
effects on the channel created. The default values are the same
as in the OpenSSH code base and have been battle tested.
:param str kind:
the kind of channel requested (usually ``"session"``,
``"forwarded-tcpip"``, ``"direct-tcpip"``, or ``"x11"``)
:param tuple dest_addr:
the destination address (address + port tuple) of this port
forwarding, if ``kind`` is ``"forwarded-tcpip"`` or
``"direct-tcpip"`` (ignored for other channel types)
:param src_addr: the source address of this port forwarding, if
``kind`` is ``"forwarded-tcpip"``, ``"direct-tcpip"``, or ``"x11"``
:param int window_size:
optional window size for this session.
:param int max_packet_size:
optional max packet size for this session.
:param float timeout:
optional timeout opening a channel, default 3600s (1h)
:return: a new `.Channel` on success
:raises:
`.SSHException` -- if the request is rejected, the session ends
prematurely or there is a timeout openning a channel
.. versionchanged:: 1.15
Added the ``window_size`` and ``max_packet_size`` arguments.
"""
if not self.active:
raise SSHException("SSH session not active")
timeout = 3600 if timeout is None else timeout
self.lock.acquire()
try:
window_size = self._sanitize_window_size(window_size)
max_packet_size = self._sanitize_packet_size(max_packet_size)
chanid = self._next_channel()
m = Message()
m.add_byte(cMSG_CHANNEL_OPEN)
m.add_string(kind)
m.add_int(chanid)
m.add_int(window_size)
m.add_int(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])
elif kind == "x11":
m.add_string(src_addr[0])
m.add_int(src_addr[1])
chan = Channel(chanid)
self._channels.put(chanid, chan)
self.channel_events[chanid] = event = threading.Event()
self.channels_seen[chanid] = True
chan._set_transport(self)
chan._set_window(window_size, max_packet_size)
finally:
self.lock.release()
self._send_user_message(m)
start_ts = time.time()
while True:
event.wait(0.1)
if not self.active:
e = self.get_exception()
if e is None:
e = SSHException("Unable to open channel.")
raise e
if event.is_set():
break
elif start_ts + timeout < time.time():
raise SSHException("Timeout opening channel.")
chan = self._channels.get(chanid)
if chan is not None:
return chan
e = self.get_exception()
if e is None:
e = SSHException("Unable to open channel.")
raise e
def request_port_forward(self, address, port, handler=None):
"""
Ask the server to forward TCP connections from a listening port on
the server, across this SSH session.
If a handler is given, that handler is called from a different thread
whenever a forwarded connection arrives. The handler parameters are::
handler(
channel,
(origin_addr, origin_port),
(server_addr, server_port),
)
where ``server_addr`` and ``server_port`` are the address and port that
the server was listening on.
If no handler is set, the default behavior is to send new incoming
forwarded connections into the accept queue, to be picked up via
`accept`.
:param str address: the address to bind when forwarding
:param int port:
the port to forward, or 0 to ask the server to allocate any port
:param callable handler:
optional handler for incoming forwarded connections, of the form
``func(Channel, (str, int), (str, int))``.
:return: the port number (`int`) allocated by the server
:raises:
`.SSHException` -- if the server refused the TCP forward request
"""
if not self.active:
raise SSHException("SSH session not active")
port = int(port)
response = self.global_request(
"tcpip-forward", (address, port), wait=True
)
if response is None:
raise SSHException("TCP forwarding request denied")
if port == 0:
port = response.get_int()
if handler is None:
def default_handler(channel, src_addr, dest_addr_port):
# src_addr, src_port = src_addr_port
# dest_addr, dest_port = dest_addr_port
self._queue_incoming_channel(channel)
handler = default_handler
self._tcp_handler = handler
return port
def cancel_port_forward(self, address, port):
"""
Ask the server to cancel a previous port-forwarding request. No more
connections to the given address & port will be forwarded across this
ssh connection.
:param str address: the address to stop forwarding
:param int port: the port to stop forwarding
"""
if not self.active:
return
self._tcp_handler = None
self.global_request("cancel-tcpip-forward", (address, port), wait=True)
def open_sftp_client(self):
"""
Create an SFTP client channel from an open transport. On success, an
SFTP session will be opened with the remote host, and a new
`.SFTPClient` object will be returned.
:return:
a new `.SFTPClient` referring to an sftp session (channel) across
this transport
"""
return SFTPClient.from_transport(self)
def send_ignore(self, byte_count=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 int byte_count:
the number of random bytes to send in the payload of the ignored
packet -- defaults to a random number from 10 to 41.
"""
m = Message()
m.add_byte(cMSG_IGNORE)
if byte_count is None:
byte_count = (byte_ord(os.urandom(1)) % 32) + 10
m.add_bytes(os.urandom(byte_count))
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.
:raises:
`.SSHException` -- if the key renegotiation failed (which causes
the session to end)
"""
self.completion_event = threading.Event()
self._send_kex_init()
while True:
self.completion_event.wait(0.1)
if not self.active:
e = self.get_exception()
if e is not None:
raise e
raise SSHException("Negotiation failed.")
if self.completion_event.is_set():
break
return
def set_keepalive(self, interval):
"""
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, for example.
:param int interval:
seconds to wait before sending a keepalive packet (or
0 to disable keepalives).
"""
def _request(x=weakref.proxy(self)):
return x.global_request("keepalive@lag.net", wait=False)
self.packetizer.set_keepalive(interval, _request)
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 str kind: name of the request.
:param tuple data:
an optional tuple containing additional data to attach to the
request.
:param bool wait:
``True`` if this method should not return until a response is
received; ``False`` otherwise.
:return:
a `.Message` containing possible additional data if the request was
successful (or an empty `.Message` if ``wait`` was ``False``);
``None`` if the request was denied.
"""
if wait:
self.completion_event = threading.Event()
m = Message()
m.add_byte(cMSG_GLOBAL_REQUEST)
m.add_string(kind)
m.add_boolean(wait)
if data is not None:
m.add(*data)
self._log(DEBUG, 'Sending global request "{}"'.format(kind))
self._send_user_message(m)
if not wait:
return None
while True:
self.completion_event.wait(0.1)
if not self.active:
return None
if self.completion_event.is_set():
break
return self.global_response
def accept(self, timeout=None):
"""
Return the next channel opened by the client over this transport, in
server mode. If no channel is opened before the given timeout,
``None`` is returned.
:param int timeout:
seconds to wait for a channel, or ``None`` to wait forever
:return: a new `.Channel` opened by the client
"""
self.lock.acquire()
try:
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,
hostkey=None,
username="",
password=None,
pkey=None,
gss_host=None,
gss_auth=False,
gss_kex=False,
gss_deleg_creds=True,
gss_trust_dns=True,
):
"""
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 `start_client`, `get_remote_server_key`, and
`Transport.auth_password` or `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 `open_channel` or
`open_session` to get a `.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 `open_channel` or `open_session` call may
fail because you haven't authenticated yet.
:param .PKey hostkey:
the host key expected from the server, or ``None`` if you don't
want to do host key verification.
:param str username: the username to authenticate as.
:param str password:
a password to use for authentication, if you want to use password
authentication; otherwise ``None``.
:param .PKey pkey:
a private key to use for authentication, if you want to use private
key authentication; otherwise ``None``.
:param str gss_host:
The target's name in the kerberos database. Default: hostname
:param bool gss_auth:
``True`` if you want to use GSS-API authentication.
:param bool gss_kex:
Perform GSS-API Key Exchange and user authentication.
:param bool gss_deleg_creds:
Whether to delegate GSS-API client credentials.
:param gss_trust_dns:
Indicates whether or not the DNS is trusted to securely
canonicalize the name of the host being connected to (default
``True``).
:raises: `.SSHException` -- if the SSH2 negotiation fails, the host key
supplied by the server is incorrect, or authentication fails.
.. versionchanged:: 2.3
Added the ``gss_trust_dns`` argument.
"""
if hostkey is not None:
# TODO: a more robust implementation would be to ask each key class
# for its nameS plural, and just use that.
# TODO: that could be used in a bunch of other spots too
if isinstance(hostkey, RSAKey):
self._preferred_keys = [
"rsa-sha2-512",
"rsa-sha2-256",
"ssh-rsa",
]
else:
self._preferred_keys = [hostkey.get_name()]
self.set_gss_host(
gss_host=gss_host,
trust_dns=gss_trust_dns,
gssapi_requested=gss_kex or gss_auth,
)
self.start_client()
# check host key if we were given one
# If GSS-API Key Exchange was performed, we are not required to check
# the host key.
if (hostkey is not None) and not gss_kex:
key = self.get_remote_server_key()
if (
key.get_name() != hostkey.get_name()
or key.asbytes() != hostkey.asbytes()
):
self._log(DEBUG, "Bad host key from server")
self._log(
DEBUG,
"Expected: {}: {}".format(
hostkey.get_name(), repr(hostkey.asbytes())
),
)
self._log(
DEBUG,
"Got : {}: {}".format(
key.get_name(), repr(key.asbytes())
),
)
raise SSHException("Bad host key from server")
self._log(
DEBUG, "Host key verified ({})".format(hostkey.get_name())
)
if (pkey is not None) or (password is not None) or gss_auth or gss_kex:
if gss_auth:
self._log(
DEBUG, "Attempting GSS-API auth... (gssapi-with-mic)"
) # noqa
self.auth_gssapi_with_mic(
username, self.gss_host, gss_deleg_creds
)
elif gss_kex:
self._log(DEBUG, "Attempting GSS-API auth... (gssapi-keyex)")
self.auth_gssapi_keyex(username)
elif pkey is not None:
self._log(DEBUG, "Attempting public-key auth...")
self.auth_publickey(username, pkey)
else:
self._log(DEBUG, "Attempting password auth...")
self.auth_password(username, password)
return
def get_exception(self):
"""
Return any exception that happened during the last server request.
This can be used to fetch more specific error information after using
calls like `start_client`. The exception (if any) is cleared after
this call.
:return:
an exception, or ``None`` if there is no stored exception.
.. versionadded:: 1.1
"""
self.lock.acquire()
try:
e = self.saved_exception
self.saved_exception = None
return e
finally:
self.lock.release()
def set_subsystem_handler(self, name, handler, *larg, **kwarg):
"""
Set the handler class for a subsystem in server mode. If a request
for this subsystem is made on an open ssh channel later, this handler
will be constructed and called -- see `.SubsystemHandler` for more
detailed documentation.
Any extra parameters (including keyword arguments) are saved and
passed to the `.SubsystemHandler` constructor later.
:param str name: name of the subsystem.
:param handler:
subclass of `.SubsystemHandler` that handles this subsystem.
"""
try:
self.lock.acquire()
self.subsystem_table[name] = (handler, larg, kwarg)
finally:
self.lock.release()
def is_authenticated(self):
"""
Return true if this session is active and authenticated.
:return:
True if the session is still open and has been authenticated
successfully; False if authentication failed and/or the session is
closed.
"""
return (
self.active
and self.auth_handler is not None
and self.auth_handler.is_authenticated()
)
def get_username(self):
"""
Return the username this connection is authenticated for. If the
session is not authenticated (or authentication failed), this method
returns ``None``.
:return: username that was authenticated (a `str`), or ``None``.
"""
if not self.active or (self.auth_handler is None):
return None
return self.auth_handler.get_username()
def get_banner(self):
"""
Return the banner supplied by the server upon connect. If no banner is
supplied, this method returns ``None``.
:returns: server supplied banner (`str`), or ``None``.
.. versionadded:: 1.13
"""
if not self.active or (self.auth_handler is None):
return None
return self.auth_handler.banner
def auth_none(self, username):
"""
Try to authenticate to the server using no authentication at all.
This will almost always fail. It may be useful for determining the
list of authentication types supported by the server, by catching the
`.BadAuthenticationType` exception raised.
:param str username: the username to authenticate as
:return:
list of auth types permissible for the next stage of
authentication (normally empty)
:raises:
`.BadAuthenticationType` -- if "none" authentication isn't allowed
by the server for this user
:raises:
`.SSHException` -- if the authentication failed due to a network
error
.. versionadded:: 1.5
"""
if (not self.active) or (not self.initial_kex_done):
raise SSHException("No existing session")
my_event = threading.Event()
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_none(username, my_event)
return self.auth_handler.wait_for_response(my_event)
def auth_password(self, username, password, event=None, fallback=True):
"""
Authenticate to the server using a password. The username and password
are sent over an encrypted link.
If an ``event`` is passed in, this method will return immediately, and
the event will be triggered once authentication succeeds or fails. On
success, `is_authenticated` will return ``True``. On failure, you may
use `get_exception` to get more detailed error information.
Since 1.1, if no event is passed, this method will block until the
authentication succeeds or fails. On failure, an exception is raised.
Otherwise, the method simply returns.
Since 1.5, if no event is passed and ``fallback`` is ``True`` (the
default), if the server doesn't support plain password authentication
but does support so-called "keyboard-interactive" mode, an attempt
will be made to authenticate using this interactive mode. If it fails,
the normal exception will be thrown as if the attempt had never been
made. This is useful for some recent Gentoo and Debian distributions,
which turn off plain password authentication in a misguided belief
that interactive authentication is "more secure". (It's not.)
If the server requires multi-step authentication (which is very rare),
this method will return a list of auth types permissible for the next
step. Otherwise, in the normal case, an empty list is returned.
:param str username: the username to authenticate as
:param basestring password: the password to authenticate with
:param .threading.Event event:
an event to trigger when the authentication attempt is complete
(whether it was successful or not)
:param bool fallback:
``True`` if an attempt at an automated "interactive" password auth
should be made if the server doesn't support normal password auth
:return:
list of auth types permissible for the next stage of
authentication (normally empty)
:raises:
`.BadAuthenticationType` -- if password authentication isn't
allowed by the server for this user (and no event was passed in)
:raises:
`.AuthenticationException` -- if the authentication failed (and no
event was passed in)
:raises: `.SSHException` -- if there was a network error
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to send the password unless we're on a secure
# link
raise SSHException("No existing session")
if event is None:
my_event = threading.Event()
else:
my_event = event
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_password(username, password, my_event)
if event is not None:
# caller wants to wait for event themselves
return []
try:
return self.auth_handler.wait_for_response(my_event)
except BadAuthenticationType as e:
# if password auth isn't allowed, but keyboard-interactive *is*,
# try to fudge it
if not fallback or ("keyboard-interactive" not in e.allowed_types):
raise
try:
def handler(title, instructions, fields):
if len(fields) > 1:
raise SSHException("Fallback authentication failed.")
if len(fields) == 0:
# for some reason, at least on os x, a 2nd request will
# be made with zero fields requested. maybe it's just
# to try to fake out automated scripting of the exact
# type we're doing here. *shrug* :)
return []
return [password]
return self.auth_interactive(username, handler)
except SSHException:
# attempt failed; just raise the original exception
raise e
def auth_publickey(self, username, key, event=None):
"""
Authenticate to the server using a private key. The key is used to
sign data from the server, so it must include the private part.
If an ``event`` is passed in, this method will return immediately, and
the event will be triggered once authentication succeeds or fails. On
success, `is_authenticated` will return ``True``. On failure, you may
use `get_exception` to get more detailed error information.
Since 1.1, if no event is passed, this method will block until the
authentication succeeds or fails. On failure, an exception is raised.
Otherwise, the method simply returns.
If the server requires multi-step authentication (which is very rare),
this method will return a list of auth types permissible for the next
step. Otherwise, in the normal case, an empty list is returned.
:param str username: the username to authenticate as
:param .PKey key: the private key to authenticate with
:param .threading.Event event:
an event to trigger when the authentication attempt is complete
(whether it was successful or not)
:return:
list of auth types permissible for the next stage of
authentication (normally empty)
:raises:
`.BadAuthenticationType` -- if public-key authentication isn't
allowed by the server for this user (and no event was passed in)
:raises:
`.AuthenticationException` -- if the authentication failed (and no
event was passed in)
:raises: `.SSHException` -- if there was a network error
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to authenticate unless we're on a secure link
raise SSHException("No existing session")
if event is None:
my_event = threading.Event()
else:
my_event = event
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_publickey(username, key, my_event)
if event is not None:
# caller wants to wait for event themselves
return []
return self.auth_handler.wait_for_response(my_event)
def auth_interactive(self, username, handler, submethods=""):
"""
Authenticate to the server interactively. A handler is used to answer
arbitrary questions from the server. On many servers, this is just a
dumb wrapper around PAM.
This method will block until the authentication succeeds or fails,
peroidically calling the handler asynchronously to get answers to
authentication questions. The handler may be called more than once
if the server continues to ask questions.
The handler is expected to be a callable that will handle calls of the
form: ``handler(title, instructions, prompt_list)``. The ``title`` is
meant to be a dialog-window title, and the ``instructions`` are user
instructions (both are strings). ``prompt_list`` will be a list of
prompts, each prompt being a tuple of ``(str, bool)``. The string is
the prompt and the boolean indicates whether the user text should be
echoed.
A sample call would thus be:
``handler('title', 'instructions', [('Password:', False)])``.
The handler should return a list or tuple of answers to the server's
questions.
If the server requires multi-step authentication (which is very rare),
this method will return a list of auth types permissible for the next
step. Otherwise, in the normal case, an empty list is returned.
:param str username: the username to authenticate as
:param callable handler: a handler for responding to server questions
:param str submethods: a string list of desired submethods (optional)
:return:
list of auth types permissible for the next stage of
authentication (normally empty).
:raises: `.BadAuthenticationType` -- if public-key authentication isn't
allowed by the server for this user
:raises: `.AuthenticationException` -- if the authentication failed
:raises: `.SSHException` -- if there was a network error
.. versionadded:: 1.5
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to authenticate unless we're on a secure link
raise SSHException("No existing session")
my_event = threading.Event()
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_interactive(
username, handler, my_event, submethods
)
return self.auth_handler.wait_for_response(my_event)
def auth_interactive_dumb(self, username, handler=None, submethods=""):
"""
Autenticate to the server interactively but dumber.
Just print the prompt and / or instructions to stdout and send back
the response. This is good for situations where partial auth is
achieved by key and then the user has to enter a 2fac token.
"""
if not handler:
def handler(title, instructions, prompt_list):
answers = []
if title:
print(title.strip())
if instructions:
print(instructions.strip())
for prompt, show_input in prompt_list:
print(prompt.strip(), end=" ")
answers.append(input())
return answers
return self.auth_interactive(username, handler, submethods)
def auth_gssapi_with_mic(self, username, gss_host, gss_deleg_creds):
"""
Authenticate to the Server using GSS-API / SSPI.
:param str username: The username to authenticate as
:param str gss_host: The target host
:param bool gss_deleg_creds: Delegate credentials or not
:return: list of auth types permissible for the next stage of
authentication (normally empty)
:raises: `.BadAuthenticationType` -- if gssapi-with-mic isn't
allowed by the server (and no event was passed in)
:raises:
`.AuthenticationException` -- if the authentication failed (and no
event was passed in)
:raises: `.SSHException` -- if there was a network error
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to authenticate unless we're on a secure link
raise SSHException("No existing session")
my_event = threading.Event()
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_gssapi_with_mic(
username, gss_host, gss_deleg_creds, my_event
)
return self.auth_handler.wait_for_response(my_event)
def auth_gssapi_keyex(self, username):
"""
Authenticate to the server with GSS-API/SSPI if GSS-API kex is in use.
:param str username: The username to authenticate as.
:returns:
a list of auth types permissible for the next stage of
authentication (normally empty)
:raises: `.BadAuthenticationType` --
if GSS-API Key Exchange was not performed (and no event was passed
in)
:raises: `.AuthenticationException` --
if the authentication failed (and no event was passed in)
:raises: `.SSHException` -- if there was a network error
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to authenticate unless we're on a secure link
raise SSHException("No existing session")
my_event = threading.Event()
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_gssapi_keyex(username, my_event)
return self.auth_handler.wait_for_response(my_event)
def set_log_channel(self, name):
"""
Set the channel for this transport's logging. The default is
``"paramiko.transport"`` but it can be set to anything you want. (See
the `.logging` module for more info.) SSH Channels will log to a
sub-channel of the one specified.
:param str name: new channel name for logging
.. versionadded:: 1.1
"""
self.log_name = name
self.logger = util.get_logger(name)
self.packetizer.set_log(self.logger)
def get_log_channel(self):
"""
Return the channel name used for this transport's logging.
:return: channel name as a `str`
.. versionadded:: 1.2
"""
return self.log_name
def set_hexdump(self, hexdump):
"""
Turn on/off logging a hex dump of protocol traffic at DEBUG level in
the logs. Normally you would want this off (which is the default),
but if you are debugging something, it may be useful.
:param bool hexdump:
``True`` to log protocol traffix (in hex) to the log; ``False``
otherwise.
"""
self.packetizer.set_hexdump(hexdump)
def get_hexdump(self):
"""
Return ``True`` if the transport is currently logging hex dumps of
protocol traffic.
:return: ``True`` if hex dumps are being logged, else ``False``.
.. versionadded:: 1.4
"""
return self.packetizer.get_hexdump()
def use_compression(self, compress=True):
"""
Turn on/off compression. This will only have an affect before starting
the transport (ie before calling `connect`, etc). By default,
compression is off since it negatively affects interactive sessions.
:param bool compress:
``True`` to ask the remote client/server to compress traffic;
``False`` to refuse compression
.. versionadded:: 1.5.2
"""
if compress:
self._preferred_compression = ("zlib@openssh.com", "zlib", "none")
else:
self._preferred_compression = ("none",)
def getpeername(self):
"""
Return the address of the remote side of this Transport, if possible.
This is effectively a wrapper around ``getpeername`` on the underlying
socket. If the socket-like object has no ``getpeername`` method, then
``("unknown", 0)`` is returned.
:return:
the address of the remote host, if known, as a ``(str, int)``
tuple.
"""
gp = getattr(self.sock, "getpeername", None)
if gp is None:
return "unknown", 0
return gp()
def stop_thread(self):
self.active = False
self.packetizer.close()
if PY2:
# Original join logic; #520 doesn't appear commonly present under
# Python 2.
while self.is_alive() and self is not threading.current_thread():
self.join(10)
else:
# Keep trying to join() our main thread, quickly, until:
# * We join()ed successfully (self.is_alive() == False)
# * Or it looks like we've hit issue #520 (socket.recv hitting some
# race condition preventing it from timing out correctly), wherein
# our socket and packetizer are both closed (but where we'd
# otherwise be sitting forever on that recv()).
while (
self.is_alive()
and self is not threading.current_thread()
and not self.sock._closed
and not self.packetizer.closed
):
self.join(0.1)
# internals...
def _log(self, level, msg, *args):
if issubclass(type(msg), list):
for m in msg:
self.logger.log(level, m)
else:
self.logger.log(level, msg, *args)
def _get_modulus_pack(self):
"""used by KexGex to find primes for group exchange"""
return self._modulus_pack
def _next_channel(self):
"""you are holding the lock"""
chanid = self._channel_counter
while self._channels.get(chanid) is not None:
self._channel_counter = (self._channel_counter + 1) & 0xffffff
chanid = self._channel_counter
self._channel_counter = (self._channel_counter + 1) & 0xffffff
return chanid
def _unlink_channel(self, chanid):
"""used by a Channel to remove itself from the active channel list"""
self._channels.delete(chanid)
def _send_message(self, data):
self.packetizer.send_message(data)
def _send_user_message(self, data):
"""
send a message, but block if we're in key negotiation. this is used
for user-initiated requests.
"""
start = time.time()
while True:
self.clear_to_send.wait(0.1)
if not self.active:
self._log(
DEBUG, "Dropping user packet because connection is dead."
) # noqa
return
self.clear_to_send_lock.acquire()
if self.clear_to_send.is_set():
break
self.clear_to_send_lock.release()
if time.time() > start + self.clear_to_send_timeout:
raise SSHException(
"Key-exchange timed out waiting for key negotiation"
) # noqa
try:
self._send_message(data)
finally:
self.clear_to_send_lock.release()
def _set_K_H(self, k, h):
"""
Used by a kex obj to set the K (root key) and H (exchange hash).
"""
self.K = k
self.H = h
if self.session_id is None:
self.session_id = h
def _expect_packet(self, *ptypes):
"""
Used by a kex obj to register the next packet type it expects to see.
"""
self._expected_packet = tuple(ptypes)
def _verify_key(self, host_key, sig):
key = self._key_info[self.host_key_type](Message(host_key))
if key is None:
raise SSHException("Unknown host key type")
if not key.verify_ssh_sig(self.H, Message(sig)):
raise SSHException(
"Signature verification ({}) failed.".format(
self.host_key_type
)
) # noqa
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(b(id))
m.add_bytes(self.session_id)
# Fallback to SHA1 for kex engines that fail to specify a hex
# algorithm, or for e.g. transport tests that don't run kexinit.
hash_algo = getattr(self.kex_engine, "hash_algo", None)
hash_select_msg = "kex engine {} specified hash_algo {!r}".format(
self.kex_engine.__class__.__name__, hash_algo
)
if hash_algo is None:
hash_algo = sha1
hash_select_msg += ", falling back to sha1"
if not hasattr(self, "_logged_hash_selection"):
self._log(DEBUG, hash_select_msg)
setattr(self, "_logged_hash_selection", True)
out = sofar = hash_algo(m.asbytes()).digest()
while len(out) < nbytes:
m = Message()
m.add_mpint(self.K)
m.add_bytes(self.H)
m.add_bytes(sofar)
digest = hash_algo(m.asbytes()).digest()
out += digest
sofar += digest
return out[:nbytes]
def _get_cipher(self, name, key, iv, operation):
if name not in self._cipher_info:
raise SSHException("Unknown client cipher " + name)
else:
cipher = Cipher(
self._cipher_info[name]["class"](key),
self._cipher_info[name]["mode"](iv),
backend=default_backend(),
)
if operation is self._ENCRYPT:
return cipher.encryptor()
else:
return cipher.decryptor()
def _set_forward_agent_handler(self, handler):
if handler is None:
def default_handler(channel):
self._queue_incoming_channel(channel)
self._forward_agent_handler = default_handler
else:
self._forward_agent_handler = handler
def _set_x11_handler(self, handler):
# only called if a channel has turned on x11 forwarding
if handler is None:
# by default, use the same mechanism as accept()
def default_handler(channel, src_addr_port):
self._queue_incoming_channel(channel)
self._x11_handler = default_handler
else:
self._x11_handler = handler
def _queue_incoming_channel(self, channel):
self.lock.acquire()
try:
self.server_accepts.append(channel)
self.server_accept_cv.notify()
finally:
self.lock.release()
def _sanitize_window_size(self, window_size):
if window_size is None:
window_size = self.default_window_size
return clamp_value(MIN_WINDOW_SIZE, window_size, MAX_WINDOW_SIZE)
def _sanitize_packet_size(self, max_packet_size):
if max_packet_size is None:
max_packet_size = self.default_max_packet_size
return clamp_value(MIN_PACKET_SIZE, max_packet_size, MAX_WINDOW_SIZE)
def _ensure_authed(self, ptype, message):
"""
Checks message type against current auth state.
If server mode, and auth has not succeeded, and the message is of a
post-auth type (channel open or global request) an appropriate error
response Message is crafted and returned to caller for sending.
Otherwise (client mode, authed, or pre-auth message) returns None.
"""
if (
not self.server_mode
or ptype <= HIGHEST_USERAUTH_MESSAGE_ID
or self.is_authenticated()
):
return None
# WELP. We must be dealing with someone trying to do non-auth things
# without being authed. Tell them off, based on message class.
reply = Message()
# Global requests have no details, just failure.
if ptype == MSG_GLOBAL_REQUEST:
reply.add_byte(cMSG_REQUEST_FAILURE)
# Channel opens let us reject w/ a specific type + message.
elif ptype == MSG_CHANNEL_OPEN:
kind = message.get_text() # noqa
chanid = message.get_int()
reply.add_byte(cMSG_CHANNEL_OPEN_FAILURE)
reply.add_int(chanid)
reply.add_int(OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED)
reply.add_string("")
reply.add_string("en")
# NOTE: Post-open channel messages do not need checking; the above will
# reject attemps to open channels, meaning that even if a malicious
# user tries to send a MSG_CHANNEL_REQUEST, it will simply fall under
# the logic that handles unknown channel IDs (as the channel list will
# be empty.)
return reply
def _enforce_strict_kex(self, ptype):
"""
Conditionally raise `MessageOrderError` during strict initial kex.
This method should only be called inside code that handles non-KEXINIT
messages; it does not interrogate ``ptype`` besides using it to log
more accurately.
"""
if self.agreed_on_strict_kex and not self.initial_kex_done:
name = MSG_NAMES.get(ptype, f"msg {ptype}")
raise MessageOrderError(
f"In strict-kex mode, but was sent {name!r}!"
)
def run(self):
# (use the exposed "run" method, because if we specify a thread target
# of a private method, threading.Thread will keep a reference to it
# indefinitely, creating a GC cycle and not letting Transport ever be
# GC'd. it's a bug in Thread.)
# Hold reference to 'sys' so we can test sys.modules to detect
# interpreter shutdown.
self.sys = sys
# active=True occurs before the thread is launched, to avoid a race
_active_threads.append(self)
tid = hex(long(id(self)) & xffffffff)
if self.server_mode:
self._log(DEBUG, "starting thread (server mode): {}".format(tid))
else:
self._log(DEBUG, "starting thread (client mode): {}".format(tid))
try:
try:
self.packetizer.write_all(b(self.local_version + "\r\n"))
self._log(
DEBUG,
"Local version/idstring: {}".format(self.local_version),
) # noqa
self._check_banner()
# The above is actually very much part of the handshake, but
# sometimes the banner can be read but the machine is not
# responding, for example when the remote ssh daemon is loaded
# in to memory but we can not read from the disk/spawn a new
# shell.
# Make sure we can specify a timeout for the initial handshake.
# Re-use the banner timeout for now.
self.packetizer.start_handshake(self.handshake_timeout)
self._send_kex_init()
self._expect_packet(MSG_KEXINIT)
while self.active:
if self.packetizer.need_rekey() and not self.in_kex:
self._send_kex_init()
try:
ptype, m = self.packetizer.read_message()
except NeedRekeyException:
continue
if ptype == MSG_IGNORE:
self._enforce_strict_kex(ptype)
continue
elif ptype == MSG_DISCONNECT:
self._parse_disconnect(m)
break
elif ptype == MSG_DEBUG:
self._enforce_strict_kex(ptype)
self._parse_debug(m)
continue
if len(self._expected_packet) > 0:
if ptype not in self._expected_packet:
exc_class = SSHException
if self.agreed_on_strict_kex:
exc_class = MessageOrderError
raise exc_class(
"Expecting packet from {!r}, got {:d}".format(
self._expected_packet, ptype
)
) # noqa
self._expected_packet = tuple()
if (ptype >= 30) and (ptype <= 41):
self.kex_engine.parse_next(ptype, m)
continue
if ptype in self._handler_table:
error_msg = self._ensure_authed(ptype, m)
if error_msg:
self._send_message(error_msg)
else:
self._handler_table[ptype](m)
elif ptype in self._channel_handler_table:
chanid = m.get_int()
chan = self._channels.get(chanid)
if chan is not None:
self._channel_handler_table[ptype](chan, m)
elif chanid in self.channels_seen:
self._log(
DEBUG,
"Ignoring message for dead channel {:d}".format( # noqa
chanid
),
)
else:
self._log(
ERROR,
"Channel request for unknown channel {:d}".format( # noqa
chanid
),
)
break
elif (
self.auth_handler is not None
and ptype in self.auth_handler._handler_table
):
handler = self.auth_handler._handler_table[ptype]
handler(self.auth_handler, m)
if len(self._expected_packet) > 0:
continue
else:
# Respond with "I don't implement this particular
# message type" message (unless the message type was
# itself literally MSG_UNIMPLEMENTED, in which case, we
# just shut up to avoid causing a useless loop).
name = MSG_NAMES[ptype]
warning = "Oops, unhandled type {} ({!r})".format(
ptype, name
)
self._log(WARNING, warning)
if ptype != MSG_UNIMPLEMENTED:
msg = Message()
msg.add_byte(cMSG_UNIMPLEMENTED)
msg.add_int(m.seqno)
self._send_message(msg)
self.packetizer.complete_handshake()
except SSHException as e:
self._log(
ERROR,
"Exception ({}): {}".format(
"server" if self.server_mode else "client", e
),
)
self._log(ERROR, util.tb_strings())
self.saved_exception = e
except EOFError as e:
self._log(DEBUG, "EOF in transport thread")
self.saved_exception = e
except socket.error as e:
if type(e.args) is tuple:
if e.args:
emsg = "{} ({:d})".format(e.args[1], e.args[0])
else: # empty tuple, e.g. socket.timeout
emsg = str(e) or repr(e)
else:
emsg = e.args
self._log(ERROR, "Socket exception: " + emsg)
self.saved_exception = e
except Exception as 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 list(self._channels.values()):
chan._unlink()
if self.active:
self.active = False
self.packetizer.close()
if self.completion_event is not None:
self.completion_event.set()
if self.auth_handler is not None:
self.auth_handler.abort()
for event in self.channel_events.values():
event.set()
try:
self.lock.acquire()
self.server_accept_cv.notify()
finally:
self.lock.release()
self.sock.close()
except:
# Don't raise spurious 'NoneType has no attribute X' errors when we
# wake up during interpreter shutdown. Or rather -- raise
# everything *if* sys.modules (used as a convenient sentinel)
# appears to still exist.
if self.sys.modules is not None:
raise
def _log_agreement(self, which, local, remote):
# Log useful, non-duplicative line re: an agreed-upon algorithm.
# Old code implied algorithms could be asymmetrical (different for
# inbound vs outbound) so we preserve that possibility.
msg = "{}: ".format(which)
if local == remote:
msg += local
else:
msg += "local={}, remote={}".format(local, remote)
self._log(DEBUG, msg)
# protocol stages
def _negotiate_keys(self, m):
# throws SSHException on anything unusual
self.clear_to_send_lock.acquire()
try:
self.clear_to_send.clear()
finally:
self.clear_to_send_lock.release()
if self.local_kex_init is 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(100):
# give them 15 seconds for the first line, then just 2 seconds
# each additional line. (some sites have very high latency.)
if i == 0:
timeout = self.banner_timeout
else:
timeout = 2
try:
buf = self.packetizer.readline(timeout)
except ProxyCommandFailure:
raise
except Exception as e:
raise SSHException(
"Error reading SSH protocol banner" + str(e)
)
if buf[:4] == "SSH-":
break
self._log(DEBUG, "Banner: " + buf)
if buf[:4] != "SSH-":
raise SSHException('Indecipherable protocol version "' + buf + '"')
# save this server version string for later
self.remote_version = buf
self._log(DEBUG, "Remote version/idstring: {}".format(buf))
# pull off any attached comment
# NOTE: comment used to be stored in a variable and then...never used.
# since 2003. ca 877cd974b8182d26fa76d566072917ea67b64e67
i = buf.find(" ")
if i >= 0:
buf = buf[:i]
# parse out version string and make sure it matches
segs = buf.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":
msg = "Incompatible version ({} instead of 2.0)"
raise IncompatiblePeer(msg.format(version))
msg = "Connected (version {}, client {})".format(version, client)
self._log(INFO, msg)
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_lock.acquire()
try:
self.clear_to_send.clear()
finally:
self.clear_to_send_lock.release()
self.gss_kex_used = False
self.in_kex = True
kex_algos = list(self.preferred_kex)
if self.server_mode:
mp_required_prefix = "diffie-hellman-group-exchange-sha"
kex_mp = [k for k in kex_algos if k.startswith(mp_required_prefix)]
if (self._modulus_pack is None) and (len(kex_mp) > 0):
# can't do group-exchange if we don't have a pack of potential
# primes
pkex = [
k
for k in self.get_security_options().kex
if not k.startswith(mp_required_prefix)
]
self.get_security_options().kex = pkex
available_server_keys = list(
filter(
list(self.server_key_dict.keys()).__contains__,
# TODO: ensure tests will catch if somebody streamlines
# this by mistake - case is the admittedly silly one where
# the only calls to add_server_key() contain keys which
# were filtered out of the below via disabled_algorithms.
# If this is streamlined, we would then be allowing the
# disabled algorithm(s) for hostkey use
# TODO: honestly this prob just wants to get thrown out
# when we make kex configuration more straightforward
self.preferred_keys,
)
)
else:
available_server_keys = self.preferred_keys
# Signal support for MSG_EXT_INFO so server will send it to us.
# NOTE: doing this here handily means we don't even consider this
# value when agreeing on real kex algo to use (which is a common
# pitfall when adding this apparently).
kex_algos.append("ext-info-c")
# Similar to ext-info, but used in both server modes, so done outside
# of above if/else.
if self.advertise_strict_kex:
which = "s" if self.server_mode else "c"
kex_algos.append(f"kex-strict-{which}-v00@openssh.com")
m = Message()
m.add_byte(cMSG_KEXINIT)
m.add_bytes(os.urandom(16))
m.add_list(kex_algos)
m.add_list(available_server_keys)
m.add_list(self.preferred_ciphers)
m.add_list(self.preferred_ciphers)
m.add_list(self.preferred_macs)
m.add_list(self.preferred_macs)
m.add_list(self.preferred_compression)
m.add_list(self.preferred_compression)
m.add_string(bytes())
m.add_string(bytes())
m.add_boolean(False)
m.add_int(0)
# save a copy for later (needed to compute a hash)
self.local_kex_init = self._latest_kex_init = m.asbytes()
self._send_message(m)
def _really_parse_kex_init(self, m, ignore_first_byte=False):
parsed = {}
if ignore_first_byte:
m.get_byte()
m.get_bytes(16) # cookie, discarded
parsed["kex_algo_list"] = m.get_list()
parsed["server_key_algo_list"] = m.get_list()
parsed["client_encrypt_algo_list"] = m.get_list()
parsed["server_encrypt_algo_list"] = m.get_list()
parsed["client_mac_algo_list"] = m.get_list()
parsed["server_mac_algo_list"] = m.get_list()
parsed["client_compress_algo_list"] = m.get_list()
parsed["server_compress_algo_list"] = m.get_list()
parsed["client_lang_list"] = m.get_list()
parsed["server_lang_list"] = m.get_list()
parsed["kex_follows"] = m.get_boolean()
m.get_int() # unused
return parsed
def _get_latest_kex_init(self):
return self._really_parse_kex_init(
Message(self._latest_kex_init),
ignore_first_byte=True,
)
def _parse_kex_init(self, m):
parsed = self._really_parse_kex_init(m)
kex_algo_list = parsed["kex_algo_list"]
server_key_algo_list = parsed["server_key_algo_list"]
client_encrypt_algo_list = parsed["client_encrypt_algo_list"]
server_encrypt_algo_list = parsed["server_encrypt_algo_list"]
client_mac_algo_list = parsed["client_mac_algo_list"]
server_mac_algo_list = parsed["server_mac_algo_list"]
client_compress_algo_list = parsed["client_compress_algo_list"]
server_compress_algo_list = parsed["server_compress_algo_list"]
client_lang_list = parsed["client_lang_list"]
server_lang_list = parsed["server_lang_list"]
kex_follows = parsed["kex_follows"]
self._log(DEBUG, "=== Key exchange possibilities ===")
for prefix, value in (
("kex algos", kex_algo_list),
("server key", server_key_algo_list),
# TODO: shouldn't these two lines say "cipher" to match usual
# terminology (including elsewhere in paramiko!)?
("client encrypt", client_encrypt_algo_list),
("server encrypt", server_encrypt_algo_list),
("client mac", client_mac_algo_list),
("server mac", server_mac_algo_list),
("client compress", client_compress_algo_list),
("server compress", server_compress_algo_list),
("client lang", client_lang_list),
("server lang", server_lang_list),
):
if value == [""]:
value = ["<none>"]
value = ", ".join(value)
self._log(DEBUG, "{}: {}".format(prefix, value))
self._log(DEBUG, "kex follows: {}".format(kex_follows))
self._log(DEBUG, "=== Key exchange agreements ===")
# Record, and strip out, ext-info and/or strict-kex non-algorithms
self._remote_ext_info = None
self._remote_strict_kex = None
to_pop = []
for i, algo in enumerate(kex_algo_list):
if algo.startswith("ext-info-"):
self._remote_ext_info = algo
to_pop.insert(0, i)
elif algo.startswith("kex-strict-"):
# NOTE: this is what we are expecting from the /remote/ end.
which = "c" if self.server_mode else "s"
expected = f"kex-strict-{which}-v00@openssh.com"
# Set strict mode if agreed.
self.agreed_on_strict_kex = (
algo == expected and self.advertise_strict_kex
)
self._log(
DEBUG, f"Strict kex mode: {self.agreed_on_strict_kex}"
)
to_pop.insert(0, i)
for i in to_pop:
kex_algo_list.pop(i)
# CVE mitigation: expect zeroed-out seqno anytime we are performing kex
# init phase, if strict mode was negotiated.
if (
self.agreed_on_strict_kex
and not self.initial_kex_done
and m.seqno != 0
):
raise MessageOrderError(
"In strict-kex mode, but KEXINIT was not the first packet!"
)
# 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 = list(
filter(self.preferred_kex.__contains__, kex_algo_list)
)
else:
agreed_kex = list(
filter(kex_algo_list.__contains__, self.preferred_kex)
)
if len(agreed_kex) == 0:
# TODO: do an auth-overhaul style aggregate exception here?
# TODO: would let us streamline log output & show all failures up
# front
raise IncompatiblePeer(
"Incompatible ssh peer (no acceptable kex algorithm)"
) # noqa
self.kex_engine = self._kex_info[agreed_kex[0]](self)
self._log(DEBUG, "Kex: {}".format(agreed_kex[0]))
if self.server_mode:
available_server_keys = list(
filter(
list(self.server_key_dict.keys()).__contains__,
self.preferred_keys,
)
)
agreed_keys = list(
filter(
available_server_keys.__contains__, server_key_algo_list
)
)
else:
agreed_keys = list(
filter(server_key_algo_list.__contains__, self.preferred_keys)
)
if len(agreed_keys) == 0:
raise IncompatiblePeer(
"Incompatible ssh peer (no acceptable host key)"
) # noqa
self.host_key_type = agreed_keys[0]
if self.server_mode and (self.get_server_key() is None):
raise IncompatiblePeer(
"Incompatible ssh peer (can't match requested host key type)"
) # noqa
self._log_agreement("HostKey", agreed_keys[0], agreed_keys[0])
if self.server_mode:
agreed_local_ciphers = list(
filter(
self.preferred_ciphers.__contains__,
server_encrypt_algo_list,
)
)
agreed_remote_ciphers = list(
filter(
self.preferred_ciphers.__contains__,
client_encrypt_algo_list,
)
)
else:
agreed_local_ciphers = list(
filter(
client_encrypt_algo_list.__contains__,
self.preferred_ciphers,
)
)
agreed_remote_ciphers = list(
filter(
server_encrypt_algo_list.__contains__,
self.preferred_ciphers,
)
)
if len(agreed_local_ciphers) == 0 or len(agreed_remote_ciphers) == 0:
raise IncompatiblePeer(
"Incompatible ssh server (no acceptable ciphers)"
) # noqa
self.local_cipher = agreed_local_ciphers[0]
self.remote_cipher = agreed_remote_ciphers[0]
self._log_agreement(
"Cipher", local=self.local_cipher, remote=self.remote_cipher
)
if self.server_mode:
agreed_remote_macs = list(
filter(self.preferred_macs.__contains__, client_mac_algo_list)
)
agreed_local_macs = list(
filter(self.preferred_macs.__contains__, server_mac_algo_list)
)
else:
agreed_local_macs = list(
filter(client_mac_algo_list.__contains__, self.preferred_macs)
)
agreed_remote_macs = list(
filter(server_mac_algo_list.__contains__, self.preferred_macs)
)
if (len(agreed_local_macs) == 0) or (len(agreed_remote_macs) == 0):
raise IncompatiblePeer(
"Incompatible ssh server (no acceptable macs)"
)
self.local_mac = agreed_local_macs[0]
self.remote_mac = agreed_remote_macs[0]
self._log_agreement(
"MAC", local=self.local_mac, remote=self.remote_mac
)
if self.server_mode:
agreed_remote_compression = list(
filter(
self.preferred_compression.__contains__,
client_compress_algo_list,
)
)
agreed_local_compression = list(
filter(
self.preferred_compression.__contains__,
server_compress_algo_list,
)
)
else:
agreed_local_compression = list(
filter(
client_compress_algo_list.__contains__,
self.preferred_compression,
)
)
agreed_remote_compression = list(
filter(
server_compress_algo_list.__contains__,
self.preferred_compression,
)
)
if (
len(agreed_local_compression) == 0
or len(agreed_remote_compression) == 0
):
msg = "Incompatible ssh server (no acceptable compression)"
msg += " {!r} {!r} {!r}"
raise IncompatiblePeer(
msg.format(
agreed_local_compression,
agreed_remote_compression,
self.preferred_compression,
)
)
self.local_compression = agreed_local_compression[0]
self.remote_compression = agreed_remote_compression[0]
self._log_agreement(
"Compression",
local=self.local_compression,
remote=self.remote_compression,
)
self._log(DEBUG, "=== End of kex handshake ===")
# 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 = cMSG_KEXINIT + m.get_so_far()
def _activate_inbound(self):
"""switch on newly negotiated encryption parameters for
inbound traffic"""
block_size = self._cipher_info[self.remote_cipher]["block-size"]
if self.server_mode:
IV_in = self._compute_key("A", block_size)
key_in = self._compute_key(
"C", self._cipher_info[self.remote_cipher]["key-size"]
)
else:
IV_in = self._compute_key("B", block_size)
key_in = self._compute_key(
"D", self._cipher_info[self.remote_cipher]["key-size"]
)
engine = self._get_cipher(
self.remote_cipher, key_in, IV_in, self._DECRYPT
)
etm = "etm@openssh.com" in self.remote_mac
mac_size = self._mac_info[self.remote_mac]["size"]
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:
mac_key = self._compute_key("E", mac_engine().digest_size)
else:
mac_key = self._compute_key("F", mac_engine().digest_size)
self.packetizer.set_inbound_cipher(
engine, block_size, mac_engine, mac_size, mac_key, etm=etm
)
compress_in = self._compression_info[self.remote_compression][1]
if compress_in is not None and (
self.remote_compression != "zlib@openssh.com" or self.authenticated
):
self._log(DEBUG, "Switching on inbound compression ...")
self.packetizer.set_inbound_compressor(compress_in())
# Reset inbound sequence number if strict mode.
if self.agreed_on_strict_kex:
self._log(
DEBUG,
"Resetting inbound seqno after NEWKEYS due to strict mode",
)
self.packetizer.reset_seqno_in()
def _activate_outbound(self):
"""switch on newly negotiated encryption parameters for
outbound traffic"""
m = Message()
m.add_byte(cMSG_NEWKEYS)
self._send_message(m)
# Reset outbound sequence number if strict mode.
if self.agreed_on_strict_kex:
self._log(
DEBUG,
"Resetting outbound seqno after NEWKEYS due to strict mode",
)
self.packetizer.reset_seqno_out()
block_size = self._cipher_info[self.local_cipher]["block-size"]
if self.server_mode:
IV_out = self._compute_key("B", block_size)
key_out = self._compute_key(
"D", self._cipher_info[self.local_cipher]["key-size"]
)
else:
IV_out = self._compute_key("A", block_size)
key_out = self._compute_key(
"C", self._cipher_info[self.local_cipher]["key-size"]
)
engine = self._get_cipher(
self.local_cipher, key_out, IV_out, self._ENCRYPT
)
etm = "etm@openssh.com" in self.local_mac
mac_size = self._mac_info[self.local_mac]["size"]
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:
mac_key = self._compute_key("F", mac_engine().digest_size)
else:
mac_key = self._compute_key("E", mac_engine().digest_size)
sdctr = self.local_cipher.endswith("-ctr")
self.packetizer.set_outbound_cipher(
engine, block_size, mac_engine, mac_size, mac_key, sdctr, etm=etm
)
compress_out = self._compression_info[self.local_compression][0]
if compress_out is not None and (
self.local_compression != "zlib@openssh.com" or self.authenticated
):
self._log(DEBUG, "Switching on outbound compression ...")
self.packetizer.set_outbound_compressor(compress_out())
if not self.packetizer.need_rekey():
self.in_kex = False
# If client indicated extension support, send that packet immediately
if (
self.server_mode
and self.server_sig_algs
and self._remote_ext_info == "ext-info-c"
):
extensions = {"server-sig-algs": ",".join(self.preferred_pubkeys)}
m = Message()
m.add_byte(cMSG_EXT_INFO)
m.add_int(len(extensions))
for name, value in sorted(extensions.items()):
m.add_string(name)
m.add_string(value)
self._send_message(m)
# we always expect to receive NEWKEYS now
self._expect_packet(MSG_NEWKEYS)
def _auth_trigger(self):
self.authenticated = True
# delayed initiation of compression
if self.local_compression == "zlib@openssh.com":
compress_out = self._compression_info[self.local_compression][0]
self._log(DEBUG, "Switching on outbound compression ...")
self.packetizer.set_outbound_compressor(compress_out())
if self.remote_compression == "zlib@openssh.com":
compress_in = self._compression_info[self.remote_compression][1]
self._log(DEBUG, "Switching on inbound compression ...")
self.packetizer.set_inbound_compressor(compress_in())
def _parse_ext_info(self, msg):
# Packet is a count followed by that many key-string to possibly-bytes
# pairs.
extensions = {}
for _ in range(msg.get_int()):
name = msg.get_text()
value = msg.get_string()
extensions[name] = value
self._log(DEBUG, "Got EXT_INFO: {}".format(extensions))
# NOTE: this should work ok in cases where a server sends /two/ such
# messages; the RFC explicitly states a 2nd one should overwrite the
# 1st.
self.server_extensions = extensions
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.K = None
self.kex_engine = None
if self.server_mode and (self.auth_handler is None):
# create auth handler for server mode
self.auth_handler = AuthHandler(self)
if not self.initial_kex_done:
# this was the first key exchange
# (also signal to packetizer as it sometimes wants to know this
# staus as well, eg when seqnos rollover)
self.initial_kex_done = self.packetizer._initial_kex_done = True
# send an event?
if self.completion_event is not None:
self.completion_event.set()
# it's now okay to send data again (if this was a re-key)
if not self.packetizer.need_rekey():
self.in_kex = False
self.clear_to_send_lock.acquire()
try:
self.clear_to_send.set()
finally:
self.clear_to_send_lock.release()
return
def _parse_disconnect(self, m):
code = m.get_int()
desc = m.get_text()
self._log(INFO, "Disconnect (code {:d}): {}".format(code, desc))
def _parse_global_request(self, m):
kind = m.get_text()
self._log(DEBUG, 'Received global request "{}"'.format(kind))
want_reply = m.get_boolean()
if not self.server_mode:
self._log(
DEBUG,
'Rejecting "{}" global request from server.'.format(kind),
)
ok = False
elif kind == "tcpip-forward":
address = m.get_text()
port = m.get_int()
ok = self.server_object.check_port_forward_request(address, port)
if ok:
ok = (ok,)
elif kind == "cancel-tcpip-forward":
address = m.get_text()
port = m.get_int()
self.server_object.cancel_port_forward_request(address, port)
ok = True
else:
ok = self.server_object.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(cMSG_REQUEST_SUCCESS)
msg.add(*extra)
else:
msg.add_byte(cMSG_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()
chan = self._channels.get(chanid)
if chan is None:
self._log(WARNING, "Success for unrequested channel! [??]")
return
self.lock.acquire()
try:
chan._set_remote_channel(
server_chanid, server_window_size, server_max_packet_size
)
self._log(DEBUG, "Secsh channel {:d} opened.".format(chanid))
if chanid in self.channel_events:
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_text()
m.get_text() # ignored language
reason_text = CONNECTION_FAILED_CODE.get(reason, "(unknown code)")
self._log(
ERROR,
"Secsh channel {:d} open FAILED: {}: {}".format(
chanid, reason_str, reason_text
),
)
self.lock.acquire()
try:
self.saved_exception = ChannelException(reason, reason_text)
if chanid in self.channel_events:
self._channels.delete(chanid)
if chanid in self.channel_events:
self.channel_events[chanid].set()
del self.channel_events[chanid]
finally:
self.lock.release()
return
def _parse_channel_open(self, m):
kind = m.get_text()
chanid = m.get_int()
initial_window_size = m.get_int()
max_packet_size = m.get_int()
reject = False
if (
kind == "auth-agent@openssh.com"
and self._forward_agent_handler is not None
):
self._log(DEBUG, "Incoming forward agent connection")
self.lock.acquire()
try:
my_chanid = self._next_channel()
finally:
self.lock.release()
elif (kind == "x11") and (self._x11_handler is not None):
origin_addr = m.get_text()
origin_port = m.get_int()
self._log(
DEBUG,
"Incoming x11 connection from {}:{:d}".format(
origin_addr, origin_port
),
)
self.lock.acquire()
try:
my_chanid = self._next_channel()
finally:
self.lock.release()
elif (kind == "forwarded-tcpip") and (self._tcp_handler is not None):
server_addr = m.get_text()
server_port = m.get_int()
origin_addr = m.get_text()
origin_port = m.get_int()
self._log(
DEBUG,
"Incoming tcp forwarded connection from {}:{:d}".format(
origin_addr, origin_port
),
)
self.lock.acquire()
try:
my_chanid = self._next_channel()
finally:
self.lock.release()
elif not self.server_mode:
self._log(
DEBUG,
'Rejecting "{}" channel request from server.'.format(kind),
)
reject = True
reason = OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
else:
self.lock.acquire()
try:
my_chanid = self._next_channel()
finally:
self.lock.release()
if kind == "direct-tcpip":
# handle direct-tcpip requests coming from the client
dest_addr = m.get_text()
dest_port = m.get_int()
origin_addr = m.get_text()
origin_port = m.get_int()
reason = self.server_object.check_channel_direct_tcpip_request(
my_chanid,
(origin_addr, origin_port),
(dest_addr, dest_port),
)
else:
reason = self.server_object.check_channel_request(
kind, my_chanid
)
if reason != OPEN_SUCCEEDED:
self._log(
DEBUG,
'Rejecting "{}" channel request from client.'.format(kind),
)
reject = True
if reject:
msg = Message()
msg.add_byte(cMSG_CHANNEL_OPEN_FAILURE)
msg.add_int(chanid)
msg.add_int(reason)
msg.add_string("")
msg.add_string("en")
self._send_message(msg)
return
chan = Channel(my_chanid)
self.lock.acquire()
try:
self._channels.put(my_chanid, chan)
self.channels_seen[my_chanid] = True
chan._set_transport(self)
chan._set_window(
self.default_window_size, self.default_max_packet_size
)
chan._set_remote_channel(
chanid, initial_window_size, max_packet_size
)
finally:
self.lock.release()
m = Message()
m.add_byte(cMSG_CHANNEL_OPEN_SUCCESS)
m.add_int(chanid)
m.add_int(my_chanid)
m.add_int(self.default_window_size)
m.add_int(self.default_max_packet_size)
self._send_message(m)
self._log(
DEBUG, "Secsh channel {:d} ({}) opened.".format(my_chanid, kind)
)
if kind == "auth-agent@openssh.com":
self._forward_agent_handler(chan)
elif kind == "x11":
self._x11_handler(chan, (origin_addr, origin_port))
elif kind == "forwarded-tcpip":
chan.origin_addr = (origin_addr, origin_port)
self._tcp_handler(
chan, (origin_addr, origin_port), (server_addr, server_port)
)
else:
self._queue_incoming_channel(chan)
def _parse_debug(self, m):
m.get_boolean() # always_display
msg = m.get_string()
m.get_string() # language
self._log(DEBUG, "Debug msg: {}".format(util.safe_string(msg)))
def _get_subsystem_handler(self, name):
try:
self.lock.acquire()
if name not in self.subsystem_table:
return None, [], {}
return self.subsystem_table[name]
finally:
self.lock.release()
_channel_handler_table = {
MSG_CHANNEL_SUCCESS: Channel._request_success,
MSG_CHANNEL_FAILURE: Channel._request_failed,
MSG_CHANNEL_DATA: Channel._feed,
MSG_CHANNEL_EXTENDED_DATA: Channel._feed_extended,
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,
}
# TODO 3.0: drop this, we barely use it ourselves, it badly replicates the
# Transport-internal algorithm management, AND does so in a way which doesn't
# honor newer things like disabled_algorithms!
class SecurityOptions(object):
"""
Simple object containing the security preferences of an ssh transport.
These are tuples of acceptable ciphers, digests, key types, and key
exchange algorithms, listed in order of preference.
Changing the contents and/or order of these fields affects the underlying
`.Transport` (but only if you change them before starting the session).
If you try to add an algorithm that paramiko doesn't recognize,
``ValueError`` will be raised. If you try to assign something besides a
tuple to one of the fields, ``TypeError`` will be raised.
"""
__slots__ = "_transport"
def __init__(self, transport):
self._transport = transport
def __repr__(self):
"""
Returns a string representation of this object, for debugging.
"""
return "<paramiko.SecurityOptions for {!r}>".format(self._transport)
def _set(self, name, orig, x):
if type(x) is list:
x = tuple(x)
if type(x) is not tuple:
raise TypeError("expected tuple or list")
possible = list(getattr(self._transport, orig).keys())
forbidden = [n for n in x if n not in possible]
if len(forbidden) > 0:
raise ValueError("unknown cipher")
setattr(self._transport, name, x)
@property
def ciphers(self):
"""Symmetric encryption ciphers"""
return self._transport._preferred_ciphers
@ciphers.setter
def ciphers(self, x):
self._set("_preferred_ciphers", "_cipher_info", x)
@property
def digests(self):
"""Digest (one-way hash) algorithms"""
return self._transport._preferred_macs
@digests.setter
def digests(self, x):
self._set("_preferred_macs", "_mac_info", x)
@property
def key_types(self):
"""Public-key algorithms"""
return self._transport._preferred_keys
@key_types.setter
def key_types(self, x):
self._set("_preferred_keys", "_key_info", x)
@property
def kex(self):
"""Key exchange algorithms"""
return self._transport._preferred_kex
@kex.setter
def kex(self, x):
self._set("_preferred_kex", "_kex_info", x)
@property
def compression(self):
"""Compression algorithms"""
return self._transport._preferred_compression
@compression.setter
def compression(self, x):
self._set("_preferred_compression", "_compression_info", x)
class ChannelMap(object):
def __init__(self):
# (id -> Channel)
self._map = weakref.WeakValueDictionary()
self._lock = threading.Lock()
def put(self, chanid, chan):
self._lock.acquire()
try:
self._map[chanid] = chan
finally:
self._lock.release()
def get(self, chanid):
self._lock.acquire()
try:
return self._map.get(chanid, None)
finally:
self._lock.release()
def delete(self, chanid):
self._lock.acquire()
try:
try:
del self._map[chanid]
except KeyError:
pass
finally:
self._lock.release()
def values(self):
self._lock.acquire()
try:
return list(self._map.values())
finally:
self._lock.release()
def __len__(self):
self._lock.acquire()
try:
return len(self._map)
finally:
self._lock.release()
Mini Shell