Exscript/protocols/ssh2.py
#
# Copyright (C) 2010-2017 Samuel Abels
# The MIT License (MIT)
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""
SSH version 2 support, based on paramiko.
"""
from __future__ import absolute_import, unicode_literals
from builtins import str
import sys
import os
import time
import select
import socket
import paramiko
try:
import Cryptodome as Crypto
except ImportError:
import Crypto
from binascii import hexlify
from paramiko import util
from paramiko.ssh_exception import SSHException, AuthenticationException, \
BadHostKeyException, BadAuthenticationType
from ..util.tty import get_terminal_size
from ..util.crypt import otp
from ..key import PrivateKey
from .protocol import Protocol, _skey_re
from .exception import ProtocolException, LoginFailure, TimeoutException, \
DriverReplacedException, ExpectCancelledException
# Workaround for paramiko error; avoids a warning message.
util.log_to_file(os.devnull)
# Register supported key types.
keymap = {'rsa': paramiko.RSAKey, 'dss': paramiko.DSSKey}
for key in keymap:
PrivateKey.keytypes.add(key)
auth_types = {'publickey': ('_paramiko_auth_agent', '_paramiko_auth_autokey'),
'keyboard-interactive': ('_paramiko_auth_interactive',),
'password': ('_paramiko_auth_password',)}
class SSH2(Protocol):
"""
The secure shell protocol version 2 adapter, based on Paramiko.
"""
KEEPALIVE_INTERVAL = 2.5 * 60 # Two and a half minutes
def __init__(self, **kwargs):
Protocol.__init__(self, **kwargs)
self.sock = None
self.client = None
self.shell = None
self.cancel = False
# Since each protocol may be created in it's own thread, we must
# re-initialize the random number generator to make sure that
# child threads have no way of guessing the numbers of the parent.
# If we don't, PyCrypto generates an error message for security
# reasons.
try:
Crypto.Random.atfork()
except AttributeError:
# pycrypto versions that have no "Random" module also do not
# detect the missing atfork() call, so they do not raise.
pass
# Paramiko client stuff.
self._system_host_keys = paramiko.HostKeys()
self._host_keys = paramiko.HostKeys()
self._host_keys_filename = None
if self.verify_fingerprint:
self._missing_host_key = self._reject_host_key
else:
self._missing_host_key = self._add_host_key
def _reject_host_key(self, key):
name = key.get_name()
fp = hexlify(key.get_fingerprint())
msg = 'Rejecting %s host key for %s: %s' % (name, self.host, fp)
self._dbg(1, msg)
def _add_host_key(self, key):
name = key.get_name()
fp = hexlify(key.get_fingerprint())
msg = 'Adding %s host key for %s: %s' % (name, self.host, fp)
self._dbg(1, msg)
self._host_keys.add(self.host, name, key)
if self._host_keys_filename is not None:
self._save_host_keys()
def _save_host_keys(self):
with open(self._host_keys_filename, 'w') as file:
file.write('# SSH host keys collected by Exscript\n')
for hostname, keys in list(self._host_keys.items()):
for keytype, key in list(keys.items()):
line = ' '.join((hostname, keytype, key.get_base64()))
file.write(line + '\n')
def _load_system_host_keys(self, filename=None):
"""
Load host keys from a system (read-only) file. Host keys read with
this method will not be saved back by :class:`save_host_keys`.
This method can be called multiple times. Each new set of host keys
will be merged with the existing set (new replacing old if there are
conflicts).
If C{filename} is left as ``None``, an attempt will be made to read
keys from the user's local "known hosts" file, as used by OpenSSH,
and no exception will be raised if the file can't be read. This is
probably only useful on posix.
:param filename: the filename to read, or ``None``
:type filename: str
@raise IOError: if a filename was provided and the file could not be
read
"""
if filename is None:
# try the user's .ssh key file, and mask exceptions
filename = os.path.expanduser('~/.ssh/known_hosts')
try:
self._system_host_keys.load(filename)
except IOError:
pass
return
self._system_host_keys.load(filename)
def _paramiko_connect(self):
# Find supported address families.
addrinfo = socket.getaddrinfo(self.host, self.port)
for family, socktype, proto, canonname, sockaddr in addrinfo:
af = family
addr = sockaddr
if socktype == socket.SOCK_STREAM:
break
# Open a socket.
self.sock = socket.socket(af, socket.SOCK_STREAM)
try:
self.sock.settimeout(self.connect_timeout or None)
except:
pass
self.sock.connect(addr)
# Init the paramiko protocol.
t = paramiko.Transport(self.sock)
t.banner_timeout = self.banner_timeout
t.start_client()
# Check system host keys.
server_key = t.get_remote_server_key()
keytype = server_key.get_name()
our_server_key = self._system_host_keys.get(
self.host, {}).get(keytype, None)
if our_server_key is None:
our_server_key = self._host_keys.get(
self.host, {}).get(keytype, None)
if our_server_key is None:
self._missing_host_key(server_key)
# if the callback returns, assume the key is ok
our_server_key = server_key
if server_key != our_server_key:
raise BadHostKeyException(self.host, server_key, our_server_key)
t.set_keepalive(self.KEEPALIVE_INTERVAL)
return t
def _paramiko_auth_none(self, username, password=None):
self.client.auth_none(username)
def _paramiko_auth_interactive(self, username, password=None):
if password is None:
return
def handler(title, instructions, prompt_list):
if not prompt_list:
return []
response = []
for prompt, visible in prompt_list:
match = _skey_re.search(prompt)
if match is not None:
skey_password = otp(password,
match.group(2),
int(match.group(1)))
response.append(skey_password)
continue
for regex in self.get_password_prompt():
match = regex.search(prompt)
if match is not None:
response.append(password)
break
return response
self.client.auth_interactive(username, handler)
def _paramiko_auth_password(self, username, password):
self.client.auth_password(username, password or '')
def _paramiko_auth_agent(self, username, password=None):
keys = paramiko.Agent().get_keys()
if not keys:
raise AuthenticationException('auth agent found no keys')
saved_exception = AuthenticationException(
'Failed to authenticate with given username')
for key in keys:
try:
fp = hexlify(key.get_fingerprint())
self._dbg(1, 'Trying SSH agent key %s' % fp)
self.client.auth_publickey(username, key)
return
except SSHException as e:
saved_exception = e
raise saved_exception
def _paramiko_auth_key(self, username, keys, password):
if password is None:
password = ''
saved_exception = AuthenticationException(
'Failed to authenticate with given username and password/key')
for pkey_class, filename in keys:
try:
key = pkey_class.from_private_key_file(filename, password)
fp = hexlify(key.get_fingerprint())
self._dbg(1, 'Trying key %s in %s' % (fp, filename))
self.client.auth_publickey(username, key)
return
except SSHException as e:
saved_exception = e
except IOError as e:
saved_exception = e
raise saved_exception
def _paramiko_auth_autokey(self, username, password):
keyfiles = []
for cls, file in ((paramiko.RSAKey, '~/.ssh/id_rsa'), # Unix
(paramiko.DSSKey, '~/.ssh/id_dsa'), # Unix
(paramiko.RSAKey, '~/ssh/id_rsa'), # Windows
(paramiko.DSSKey, '~/ssh/id_dsa')): # Windows
file = os.path.expanduser(file)
if os.path.isfile(file):
keyfiles.append((cls, file))
self._paramiko_auth_key(username, keyfiles, password)
def _get_auth_methods(self, allowed_types):
auth_methods = []
for method in allowed_types:
if method not in auth_types:
self._dbg(1, 'Unsupported auth method %s' % repr(method))
continue
for type_name in auth_types[method]:
auth_methods.append(getattr(self, type_name))
return auth_methods
def _paramiko_auth(self, username, password):
# Try authentication using auth_none. This should (almost) always fail,
# but provides us with info about allowed authentication types.
try:
self.client.auth_none(username)
except BadAuthenticationType as err:
self._dbg(1, 'auth_none failed, supported: %s' % err.allowed_types)
auth_methods = self._get_auth_methods(err.allowed_types)
else:
return
# Finally try all supported login methods.
errors = []
for method in auth_methods:
# Some OSes (e.g. JunOS ERX OS, Huawei) do not accept further login
# attempts after failing one. So in this hack, we
# re-connect after each attempt...
if self.get_driver().reconnect_between_auth_methods or not self.client.active:
self.close(force=True)
self.client = self._paramiko_connect()
self._dbg(1, 'Authenticating with %s' % method.__name__)
try:
method(username, password)
return
except BadHostKeyException as e:
msg = '%s: Bad host key: %s' % (method.__name__, str(e))
self._dbg(1, msg)
errors.append(msg)
except AuthenticationException as e:
msg = 'Authentication with %s failed' % method.__name__
msg += ': ' + str(e)
self._dbg(1, msg)
errors.append(msg)
except SSHException as e:
msg = '%s: SSHException: %s' % (method.__name__, str(e))
self._dbg(1, msg)
errors.append(msg)
raise LoginFailure('Login failed: ' + '; '.join(errors))
def _paramiko_shell(self):
rows, cols = get_terminal_size()
try:
self.shell = self.client.open_session()
self.shell.get_pty(self.termtype, cols, rows)
self.shell.invoke_shell()
except SSHException as e:
self._dbg(1, 'Failed to open shell.')
raise LoginFailure('Failed to open shell: ' + str(e))
def _connect_hook(self, hostname, port):
self.host = hostname
self.port = port or 22
self.client = self._paramiko_connect()
self._load_system_host_keys()
return True
def _protocol_authenticate(self, user, password):
self._paramiko_auth(user, password)
self._paramiko_shell()
def _protocol_authenticate_by_key(self, user, key):
# Allow multiple key files.
key_file = key.get_filename()
# Python3 does not support unicode and base string
if sys.version_info >= (3,0):
_str_types = (str)
else:
_str_types = (str, unicode, basestring)
if key_file is None:
key_file = []
elif isinstance(key_file, (str, _str_types)):
key_file = [key_file]
# Try each key.
keys = []
for file in key_file:
keys.append((keymap[key.get_type()], file))
self._dbg(1, 'authenticating using _paramiko_auth_key().')
self._paramiko_auth_key(user, keys, key.get_password())
self._paramiko_shell()
def get_banner(self):
if not self.client:
return None
return self.client.get_banner()
def get_remote_version(self):
if not self.client:
return None
return self.client.remote_version
def send(self, data):
self._dbg(4, 'Sending %s' % repr(data))
self.shell.sendall(data)
def _wait_for_data(self):
end = time.time() + self.timeout
while True:
readable, writeable, excp = select.select([self.shell], [], [], 1)
if readable:
return True
if time.time() > end:
return False
def _fill_buffer(self):
# Wait for a response of the device.
if not self._wait_for_data():
error = 'Timeout while waiting for response from device'
raise TimeoutException(error)
# Read the response.
data = self.shell.recv(200)
if not data:
return False
data = data.decode(self.encoding)
self._receive_cb(data, False)
self.buffer.append(data)
return True
def _domatch(self, prompt, flush):
self._dbg(1, "Expecting a prompt")
self._dbg(2, "Expected pattern: " +
repr([repr(p.pattern) for p in prompt]))
search_window_size = 150
while not self.cancel:
# Check whether what's buffered matches the prompt.
driver = self.get_driver()
search_window = self.buffer.tail(search_window_size)
search_window, incomplete_tail = driver.clean_response_for_re_match(
search_window)
match = None
for n, regex in enumerate(prompt):
match = regex.search(search_window)
if match is not None:
break
if not match:
if not self._fill_buffer():
error = 'EOF while waiting for response from device'
raise ProtocolException(error)
continue
end = self.buffer.size() - len(search_window) + match.start()
if flush:
self.response = self.buffer.pop(end)
self.buffer.pop(match.end() - match.start())
else:
self.response = self.buffer.head(end)
return n, match
# Ending up here, self.cancel_expect() was called.
self.cancel = False
if self.driver_replaced:
self.driver_replaced = False
raise DriverReplacedException()
raise ExpectCancelledException()
def cancel_expect(self):
self.cancel = True
def _set_terminal_size(self, rows, cols):
self.shell.resize_pty(cols, rows)
def interact(self, key_handlers=None, handle_window_size=True):
return self._open_shell(self.shell, key_handlers, handle_window_size)
def close(self, force=False):
if self.shell is None:
super(SSH2, self).close()
return
if not force:
self._fill_buffer()
self.shell.close()
self.shell = None
self.client.close()
self.client = None
self.sock.close()
self.sock = None
self.buffer.clear()
super(SSH2, self).close()