/usr/lib/python2.7/dist-packages/x2go/checkhosts.py is in python-x2go 0.5.0.1-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# Copyright (C) 2010-2014 by Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
#
# Python X2Go is free software; you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# Python X2Go 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program; if not, write to the
# Free Software Foundation, Inc.,
# 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
"""\
Providing mechanisms to C{X2GoControlSession*} backends for checking host validity.
"""
__NAME__ = 'x2gocheckhosts-pylib'
# modules
import paramiko
import binascii
# Python X2Go modules
import sshproxy
import log
import x2go_exceptions
import random
import string
class X2GoMissingHostKeyPolicy(paramiko.MissingHostKeyPolicy):
"""\
Skeleton class for Python X2Go's missing host key policies.
"""
def __init__(self, caller=None, session_instance=None, fake_hostname=None):
"""\
@param caller: calling instance
@type caller: C{class}
@param session_instance: an X2Go session instance
@type session_instance: L{X2GoSession} instance
"""
self.caller = caller
self.session_instance = session_instance
self.fake_hostname = fake_hostname
def get_client(self):
"""\
Retrieve the Paramiko SSH/Client.
@return: the associated X2Go control session instance.
@rtype: C{X2GoControlSession*} instance
"""
return self.client
def get_hostname(self):
"""\
Retrieve the server hostname:port expression of the server to be validated.
@return: hostname:port
@rtype: C{str}
"""
return self.fake_hostname or self.hostname
def get_hostname_name(self):
"""\
Retrieve the server hostname string of the server to be validated.
@return: hostname
@rtype: C{str}
"""
if ":" in self.get_hostname():
return self.get_hostname().split(':')[0].lstrip('[').rstrip(']')
else:
return self.get_hostname().lstrip('[').rstrip(']')
def get_hostname_port(self):
"""\
Retrieve the server port of the server to be validated.
@return: port
@rtype: C{str}
"""
if ":" in self.get_hostname():
return int(self.get_hostname().split(':')[1])
else:
return 22
def get_key(self):
"""\
Retrieve the host key of the server to be validated.
@return: host key
@rtype: Paramiko/SSH key instance
"""
return self.key
def get_key_name(self):
"""\
Retrieve the host key name of the server to be validated.
@return: host key name (RSA, DSA, ECDSA...)
@rtype: C{str}
"""
return self.key.get_name().upper()
def get_key_fingerprint(self):
"""\
Retrieve the host key fingerprint of the server to be validated.
@return: host key fingerprint
@rtype: C{str}
"""
return binascii.hexlify(self.key.get_fingerprint())
def get_key_fingerprint_with_colons(self):
"""\
Retrieve the (colonized) host key fingerprint of the server
to be validated.
@return: host key fingerprint (with colons)
@rtype: C{str}
"""
_fingerprint = self.get_key_fingerprint()
_colon_fingerprint = ''
idx = 0
for char in _fingerprint:
idx += 1
_colon_fingerprint += char
if idx % 2 == 0:
_colon_fingerprint += ':'
return _colon_fingerprint.rstrip(':')
class X2GoAutoAddPolicy(X2GoMissingHostKeyPolicy):
def missing_host_key(self, client, hostname, key):
self.client = client
self.hostname = hostname
self.key = key
if self.session_instance and self.session_instance.control_session.unique_hostkey_aliases:
self.client._host_keys.add(self.session_instance.get_profile_id(), self.key.get_name(), self.key)
else:
self.client._host_keys.add(self.get_hostname(), self.key.get_name(), self.key)
if self.client._host_keys_filename is not None:
self.client.save_host_keys(self.client._host_keys_filename)
self.client._log(paramiko.common.DEBUG, 'Adding %s host key for %s: %s' %
(self.key.get_name(), self.get_hostname(), binascii.hexlify(self.key.get_fingerprint())))
class X2GoInteractiveAddPolicy(X2GoMissingHostKeyPolicy):
"""\
Policy for making host key information available to Python X2Go after a
Paramiko/SSH connect has been attempted. This class needs information
about the associated L{X2GoSession} instance.
Once called, the L{missing_host_key} method of this class will try to call
L{X2GoSession.HOOK_check_host_dialog()}. This hook method---if not re-defined
in your application---will then try to call the L{X2GoClient.HOOK_check_host_dialog()},
which then will return C{True} by default if not customized in your application.
To accept host key checks, make sure to either customize the
L{X2GoClient.HOOK_check_host_dialog()} method or the L{X2GoSession.HOOK_check_host_dialog()}
method and hook some interactive user dialog to either of them.
"""
def missing_host_key(self, client, hostname, key):
"""\
Handle a missing host key situation. This method calls
Once called, the L{missing_host_key} method will try to call
L{X2GoSession.HOOK_check_host_dialog()}. This hook method---if not re-defined
in your application---will then try to call the L{X2GoClient.HOOK_check_host_dialog()},
which then will return C{True} by default if not customized in your application.
To accept host key checks, make sure to either customize the
L{X2GoClient.HOOK_check_host_dialog()} method or the L{X2GoSession.HOOK_check_host_dialog()}
method and hook some interactive user dialog to either of them.
@param client: SSH client (C{X2GoControlSession*}) instance
@type client: C{X2GoControlSession*} instance
@param hostname: remote hostname
@type hostname: C{str}
@param key: host key to validate
@type key: Paramiko/SSH key instance
@raise X2GoHostKeyException: if the X2Go server host key is not in the C{known_hosts} file
@raise X2GoSSHProxyHostKeyException: if the SSH proxy host key is not in the C{known_hosts} file
@raise SSHException: if this instance does not know its {self.session_instance}
"""
self.client = client
self.hostname = hostname
if (self.hostname.find(']') == -1) and (self.hostname.find(':') == -1):
# if hostname is an IPv4 quadruple with standard SSH port...
self.hostname = '[%s]:22' % self.hostname
self.key = key
self.client._log(paramiko.common.DEBUG, 'Interactively Checking %s host key for %s: %s' %
(self.key.get_name(), self.get_hostname(), binascii.hexlify(self.key.get_fingerprint())))
if self.session_instance:
if self.fake_hostname is not None:
server_key = client.get_transport().get_remote_server_key()
keytype = server_key.get_name()
our_server_key = client._system_host_keys.get(self.fake_hostname, {}).get(keytype, None)
if our_server_key is None:
if self.session_instance.control_session.unique_hostkey_aliases:
our_server_key = client._host_keys.get(self.session_instance.get_profile_id(), {}).get(keytype, None)
if our_server_key is not None:
self.session_instance.logger('SSH host key verification for SSH-proxied host %s with %s fingerprint ,,%s\'\' succeeded. This host is known by the X2Go session profile ID of profile ,,%s\'\'.' % (self.fake_hostname, self.get_key_name(), self.get_key_fingerprint_with_colons(), self.session_instance.profile_name), loglevel=log.loglevel_NOTICE)
return
else:
our_server_key = client._host_keys.get(self.fake_hostname, {}).get(keytype, None)
if our_server_key is not None:
self.session_instance.logger('SSH host key verification for SSH-proxied host %s with %s fingerprint ,,%s\'\' succeeded. This host is known by the address it has behind the SSH proxy host.' % (self.fake_hostname, self.get_key_name(), self.get_key_fingerprint_with_colons()), loglevel=log.loglevel_NOTICE)
return
self.session_instance.logger('SSH host key verification for host %s with %s fingerprint ,,%s\'\' initiated. We are seeing this X2Go server for the first time.' % (self.get_hostname(), self.get_key_name(), self.get_key_fingerprint_with_colons()), loglevel=log.loglevel_NOTICE)
_valid = self.session_instance.HOOK_check_host_dialog(self.get_hostname_name(),
port=self.get_hostname_port(),
fingerprint=self.get_key_fingerprint_with_colons(),
fingerprint_type=self.get_key_name(),
)
if _valid:
if self.session_instance.control_session.unique_hostkey_aliases and type(self.caller) not in (sshproxy.X2GoSSHProxy, ):
paramiko.AutoAddPolicy().missing_host_key(client, self.session_instance.get_profile_id(), key)
else:
paramiko.AutoAddPolicy().missing_host_key(client, self.get_hostname(), key)
else:
if type(self.caller) in (sshproxy.X2GoSSHProxy, ):
raise x2go_exceptions.X2GoSSHProxyHostKeyException('Invalid host %s is not authorized for access. Add the host to Paramiko/SSH\'s known_hosts file.' % self.get_hostname())
else:
raise x2go_exceptions.X2GoHostKeyException('Invalid host %s is not authorized for access. Add the host to Paramiko/SSH\'s known_hosts file.' % self.get_hostname())
else:
raise x2go_exceptions.SSHException('Policy has collected host key information on %s for further introspection' % self.get_hostname())
def check_ssh_host_key(x2go_sshclient_instance, hostname, port=22):
"""\
Perform a Paramiko/SSH host key check by connecting to the host and
validating the results (i.e. by validating raised exceptions during the
connect process).
@param x2go_sshclient_instance: a Paramiko/SSH client instance to be used for testing host key validity.
@type x2go_sshclient_instance: C{X2GoControlSession*} instance
@param hostname: hostname of server to validate
@type hostname: C{str}
@param port: port of server to validate
@type port: C{int}
@return: returns a tuple with the following components (<host_ok>, <hostname>, <port>, <fingerprint>, <fingerprint_type>)
@rtype: C{tuple}
@raise SSHException: if an SSH exception occurred, that we did not provocate in L{X2GoInteractiveAddPolicy.missing_host_key()}
"""
_hostname = hostname
_port = port
_fingerprint = 'NO-FINGERPRINT'
_fingerprint_type = 'SOME-KEY-TYPE'
_check_policy = X2GoInteractiveAddPolicy()
x2go_sshclient_instance.set_missing_host_key_policy(_check_policy)
host_ok = False
try:
paramiko.SSHClient.connect(x2go_sshclient_instance, hostname=hostname, port=port, username='foo', password="".join([random.choice(string.letters+string.digits) for x in range(1, 20)]))
except x2go_exceptions.AuthenticationException:
host_ok = True
x2go_sshclient_instance.logger('SSH host key verification for host [%s]:%s succeeded. Host is already known to the client\'s Paramiko/SSH sub-system.' % (_hostname, _port), loglevel=log.loglevel_NOTICE)
except x2go_exceptions.SSHException, e:
msg = str(e)
if msg.startswith('Policy has collected host key information on '):
_hostname = _check_policy.get_hostname().split(':')[0].lstrip('[').rstrip(']')
_port = _check_policy.get_hostname().split(':')[1]
_fingerprint = _check_policy.get_key_fingerprint_with_colons()
_fingerprint_type = _check_policy.get_key_name()
else:
raise(e)
x2go_sshclient_instance.set_missing_host_key_policy(paramiko.RejectPolicy())
except:
# let any other error be handled by subsequent algorithms
pass
return (host_ok, _hostname, _port, _fingerprint, _fingerprint_type)
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