FM / paramiko

/opt/imh-python/lib/python3.9/site-packages/paramiko/

/opt/imh-python/lib/python3.9/site-packages/paramiko

Name	Size	Mode	Actions
__pycache__/	-	0755	rm
agent.py	15877	0644	edit dl rm
auth_handler.py	42964	0644	edit dl rm
auth_handler.py.orig	43006	0644	edit dl rm
auth_strategy.py	11437	0644	edit dl rm
ber.py	4369	0644	edit dl rm
buffered_pipe.py	7225	0644	edit dl rm
channel.py	49222	0644	edit dl rm
client.py	34492	0644	edit dl rm
common.py	7756	0644	edit dl rm
compress.py	1282	0644	edit dl rm
config.py	27362	0644	edit dl rm
dsskey.py	8248	0644	edit dl rm
ecdsakey.py	11653	0644	edit dl rm
ed25519key.py	7457	0644	edit dl rm
file.py	19063	0644	edit dl rm
hostkeys.py	13208	0644	edit dl rm
kex_curve25519.py	4436	0644	edit dl rm
kex_ecdh_nist.py	5012	0644	edit dl rm
kex_gex.py	10320	0644	edit dl rm
kex_group1.py	5740	0644	edit dl rm
kex_group14.py	1833	0644	edit dl rm
kex_group16.py	2288	0644	edit dl rm
kex_gss.py	24562	0644	edit dl rm
message.py	9349	0644	edit dl rm
packet.py	24314	0644	edit dl rm
pipe.py	3902	0644	edit dl rm
pkey.py	36851	0644	edit dl rm
primes.py	5107	0644	edit dl rm
proxy.py	4648	0644	edit dl rm
rsakey.py	7546	0644	edit dl rm
server.py	30457	0644	edit dl rm
sftp.py	6471	0644	edit dl rm
sftp_attr.py	8258	0644	edit dl rm
sftp_client.py	35855	0644	edit dl rm
sftp_file.py	21820	0644	edit dl rm
sftp_handle.py	7424	0644	edit dl rm
sftp_server.py	19492	0644	edit dl rm
sftp_si.py	12544	0644	edit dl rm
ssh_exception.py	7494	0644	edit dl rm
ssh_gss.py	28887	0644	edit dl rm
transport.py	135632	0644	edit dl rm
util.py	9550	0644	edit dl rm
win_openssh.py	1918	0644	edit dl rm
win_pageant.py	4177	0644	edit dl rm
_version.py	80	0644	edit dl rm
_winapi.py	11204	0644	edit dl rm
__init__.py	4446	0644	edit dl rm

Edit: /opt/imh-python/lib/python3.9/site-packages/paramiko/ssh_gss.py (28887B)

# Copyright (C) 2013-2014 science + computing ag
# Author: Sebastian Deiss <sebastian.deiss@t-online.de>
#
#
# 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.

"""
This module provides GSS-API / SSPI  authentication as defined in :rfc:`4462`.

.. note:: Credential delegation is not supported in server mode.

.. seealso:: :doc:`/api/kex_gss`

.. versionadded:: 1.15
"""

import struct
import os
import sys

#: A boolean constraint that indicates if GSS-API / SSPI is available.
GSS_AUTH_AVAILABLE = True

#: A tuple of the exception types used by the underlying GSSAPI implementation.
GSS_EXCEPTIONS = ()

#: :var str _API: Constraint for the used API
_API = None

try:
    import gssapi

if hasattr(gssapi, "__title__") and gssapi.__title__ == "python-gssapi":
        # old, unmaintained python-gssapi package
        _API = "MIT"  # keep this for compatibility
        GSS_EXCEPTIONS = (gssapi.GSSException,)
    else:
        _API = "PYTHON-GSSAPI-NEW"
        GSS_EXCEPTIONS = (
            gssapi.exceptions.GeneralError,
            gssapi.raw.misc.GSSError,
        )
except (ImportError, OSError):
    try:
        import pywintypes
        import sspicon
        import sspi

_API = "SSPI"
        GSS_EXCEPTIONS = (pywintypes.error,)
    except ImportError:
        GSS_AUTH_AVAILABLE = False
        _API = None

from paramiko.common import MSG_USERAUTH_REQUEST
from paramiko.ssh_exception import SSHException
from paramiko._version import __version_info__

def GSSAuth(auth_method, gss_deleg_creds=True):
    """
    Provide SSH2 GSS-API / SSPI authentication.

:param str auth_method: The name of the SSH authentication mechanism
                            (gssapi-with-mic or gss-keyex)
    :param bool gss_deleg_creds: Delegate client credentials or not.
                                 We delegate credentials by default.
    :return: Either an `._SSH_GSSAPI_OLD` or `._SSH_GSSAPI_NEW` (Unix)
             object or an `_SSH_SSPI` (Windows) object
    :rtype: object

:raises: ``ImportError`` -- If no GSS-API / SSPI module could be imported.

:see: `RFC 4462 <http://www.ietf.org/rfc/rfc4462.txt>`_
    :note: Check for the available API and return either an `._SSH_GSSAPI_OLD`
           (MIT GSSAPI using python-gssapi package) object, an
           `._SSH_GSSAPI_NEW` (MIT GSSAPI using gssapi package) object
           or an `._SSH_SSPI` (MS SSPI) object.
           If there is no supported API available,
           ``None`` will be returned.
    """
    if _API == "MIT":
        return _SSH_GSSAPI_OLD(auth_method, gss_deleg_creds)
    elif _API == "PYTHON-GSSAPI-NEW":
        return _SSH_GSSAPI_NEW(auth_method, gss_deleg_creds)
    elif _API == "SSPI" and os.name == "nt":
        return _SSH_SSPI(auth_method, gss_deleg_creds)
    else:
        raise ImportError("Unable to import a GSS-API / SSPI module!")

class _SSH_GSSAuth:
    """
    Contains the shared variables and methods of `._SSH_GSSAPI_OLD`,
    `._SSH_GSSAPI_NEW` and `._SSH_SSPI`.
    """

def __init__(self, auth_method, gss_deleg_creds):
        """
        :param str auth_method: The name of the SSH authentication mechanism
                                (gssapi-with-mic or gss-keyex)
        :param bool gss_deleg_creds: Delegate client credentials or not
        """
        self._auth_method = auth_method
        self._gss_deleg_creds = gss_deleg_creds
        self._gss_host = None
        self._username = None
        self._session_id = None
        self._service = "ssh-connection"
        """
        OpenSSH supports Kerberos V5 mechanism only for GSS-API authentication,
        so we also support the krb5 mechanism only.
        """
        self._krb5_mech = "1.2.840.113554.1.2.2"

# client mode
        self._gss_ctxt = None
        self._gss_ctxt_status = False

# server mode
        self._gss_srv_ctxt = None
        self._gss_srv_ctxt_status = False
        self.cc_file = None

def set_service(self, service):
        """
        This is just a setter to use a non default service.
        I added this method, because RFC 4462 doesn't specify "ssh-connection"
        as the only service value.

:param str service: The desired SSH service
        """
        if service.find("ssh-"):
            self._service = service

def set_username(self, username):
        """
        Setter for C{username}. If GSS-API Key Exchange is performed, the
        username is not set by C{ssh_init_sec_context}.

:param str username: The name of the user who attempts to login
        """
        self._username = username

def ssh_gss_oids(self, mode="client"):
        """
        This method returns a single OID, because we only support the
        Kerberos V5 mechanism.

:param str mode: Client for client mode and server for server mode
        :return: A byte sequence containing the number of supported
                 OIDs, the length of the OID and the actual OID encoded with
                 DER
        :note: In server mode we just return the OID length and the DER encoded
               OID.
        """
        from pyasn1.type.univ import ObjectIdentifier
        from pyasn1.codec.der import encoder

OIDs = self._make_uint32(1)
        krb5_OID = encoder.encode(ObjectIdentifier(self._krb5_mech))
        OID_len = self._make_uint32(len(krb5_OID))
        if mode == "server":
            return OID_len + krb5_OID
        return OIDs + OID_len + krb5_OID

def ssh_check_mech(self, desired_mech):
        """
        Check if the given OID is the Kerberos V5 OID (server mode).

:param str desired_mech: The desired GSS-API mechanism of the client
        :return: ``True`` if the given OID is supported, otherwise C{False}
        """
        from pyasn1.codec.der import decoder

mech, __ = decoder.decode(desired_mech)
        if mech.__str__() != self._krb5_mech:
            return False
        return True

# Internals
    # -------------------------------------------------------------------------
    def _make_uint32(self, integer):
        """
        Create a 32 bit unsigned integer (The byte sequence of an integer).

:param int integer: The integer value to convert
        :return: The byte sequence of an 32 bit integer
        """
        return struct.pack("!I", integer)

def _ssh_build_mic(self, session_id, username, service, auth_method):
        """
        Create the SSH2 MIC filed for gssapi-with-mic.

:param str session_id: The SSH session ID
        :param str username: The name of the user who attempts to login
        :param str service: The requested SSH service
        :param str auth_method: The requested SSH authentication mechanism
        :return: The MIC as defined in RFC 4462. The contents of the
                 MIC field are:
                 string    session_identifier,
                 byte      SSH_MSG_USERAUTH_REQUEST,
                 string    user-name,
                 string    service (ssh-connection),
                 string    authentication-method
                           (gssapi-with-mic or gssapi-keyex)
        """
        mic = self._make_uint32(len(session_id))
        mic += session_id
        mic += struct.pack("B", MSG_USERAUTH_REQUEST)
        mic += self._make_uint32(len(username))
        mic += username.encode()
        mic += self._make_uint32(len(service))
        mic += service.encode()
        mic += self._make_uint32(len(auth_method))
        mic += auth_method.encode()
        return mic

class _SSH_GSSAPI_OLD(_SSH_GSSAuth):
    """
    Implementation of the GSS-API MIT Kerberos Authentication for SSH2,
    using the older (unmaintained) python-gssapi package.

:see: `.GSSAuth`
    """

if self._gss_deleg_creds:
            self._gss_flags = (
                gssapi.C_PROT_READY_FLAG,
                gssapi.C_INTEG_FLAG,
                gssapi.C_MUTUAL_FLAG,
                gssapi.C_DELEG_FLAG,
            )
        else:
            self._gss_flags = (
                gssapi.C_PROT_READY_FLAG,
                gssapi.C_INTEG_FLAG,
                gssapi.C_MUTUAL_FLAG,
            )

def ssh_init_sec_context(
        self, target, desired_mech=None, username=None, recv_token=None
    ):
        """
        Initialize a GSS-API context.

:param str username: The name of the user who attempts to login
        :param str target: The hostname of the target to connect to
        :param str desired_mech: The negotiated GSS-API mechanism
                                 ("pseudo negotiated" mechanism, because we
                                 support just the krb5 mechanism :-))
        :param str recv_token: The GSS-API token received from the Server
        :raises:
            `.SSHException` -- Is raised if the desired mechanism of the client
            is not supported
        :return: A ``String`` if the GSS-API has returned a token or
            ``None`` if no token was returned
        """
        from pyasn1.codec.der import decoder

self._username = username
        self._gss_host = target
        targ_name = gssapi.Name(
            "host@" + self._gss_host, gssapi.C_NT_HOSTBASED_SERVICE
        )
        ctx = gssapi.Context()
        ctx.flags = self._gss_flags
        if desired_mech is None:
            krb5_mech = gssapi.OID.mech_from_string(self._krb5_mech)
        else:
            mech, __ = decoder.decode(desired_mech)
            if mech.__str__() != self._krb5_mech:
                raise SSHException("Unsupported mechanism OID.")
            else:
                krb5_mech = gssapi.OID.mech_from_string(self._krb5_mech)
        token = None
        try:
            if recv_token is None:
                self._gss_ctxt = gssapi.InitContext(
                    peer_name=targ_name,
                    mech_type=krb5_mech,
                    req_flags=ctx.flags,
                )
                token = self._gss_ctxt.step(token)
            else:
                token = self._gss_ctxt.step(recv_token)
        except gssapi.GSSException:
            message = "{} Target: {}".format(sys.exc_info()[1], self._gss_host)
            raise gssapi.GSSException(message)
        self._gss_ctxt_status = self._gss_ctxt.established
        return token

def ssh_get_mic(self, session_id, gss_kex=False):
        """
        Create the MIC token for a SSH2 message.

:param str session_id: The SSH session ID
        :param bool gss_kex: Generate the MIC for GSS-API Key Exchange or not
        :return: gssapi-with-mic:
                 Returns the MIC token from GSS-API for the message we created
                 with ``_ssh_build_mic``.
                 gssapi-keyex:
                 Returns the MIC token from GSS-API with the SSH session ID as
                 message.
        """
        self._session_id = session_id
        if not gss_kex:
            mic_field = self._ssh_build_mic(
                self._session_id,
                self._username,
                self._service,
                self._auth_method,
            )
            mic_token = self._gss_ctxt.get_mic(mic_field)
        else:
            # for key exchange with gssapi-keyex
            mic_token = self._gss_srv_ctxt.get_mic(self._session_id)
        return mic_token

def ssh_accept_sec_context(self, hostname, recv_token, username=None):
        """
        Accept a GSS-API context (server mode).

:param str hostname: The servers hostname
        :param str username: The name of the user who attempts to login
        :param str recv_token: The GSS-API Token received from the server,
                               if it's not the initial call.
        :return: A ``String`` if the GSS-API has returned a token or ``None``
                if no token was returned
        """
        # hostname and username are not required for GSSAPI, but for SSPI
        self._gss_host = hostname
        self._username = username
        if self._gss_srv_ctxt is None:
            self._gss_srv_ctxt = gssapi.AcceptContext()
        token = self._gss_srv_ctxt.step(recv_token)
        self._gss_srv_ctxt_status = self._gss_srv_ctxt.established
        return token

def ssh_check_mic(self, mic_token, session_id, username=None):
        """
        Verify the MIC token for a SSH2 message.

:param str mic_token: The MIC token received from the client
        :param str session_id: The SSH session ID
        :param str username: The name of the user who attempts to login
        :return: None if the MIC check was successful
        :raises: ``gssapi.GSSException`` -- if the MIC check failed
        """
        self._session_id = session_id
        self._username = username
        if self._username is not None:
            # server mode
            mic_field = self._ssh_build_mic(
                self._session_id,
                self._username,
                self._service,
                self._auth_method,
            )
            self._gss_srv_ctxt.verify_mic(mic_field, mic_token)
        else:
            # for key exchange with gssapi-keyex
            # client mode
            self._gss_ctxt.verify_mic(self._session_id, mic_token)

@property
    def credentials_delegated(self):
        """
        Checks if credentials are delegated (server mode).

:return: ``True`` if credentials are delegated, otherwise ``False``
        """
        if self._gss_srv_ctxt.delegated_cred is not None:
            return True
        return False

def save_client_creds(self, client_token):
        """
        Save the Client token in a file. This is used by the SSH server
        to store the client credentials if credentials are delegated
        (server mode).

:param str client_token: The GSS-API token received form the client
        :raises:
            ``NotImplementedError`` -- Credential delegation is currently not
            supported in server mode
        """
        raise NotImplementedError

if __version_info__ < (2, 5):
    # provide the old name for strict backward compatibility
    _SSH_GSSAPI = _SSH_GSSAPI_OLD

class _SSH_GSSAPI_NEW(_SSH_GSSAuth):
    """
    Implementation of the GSS-API MIT Kerberos Authentication for SSH2,
    using the newer, currently maintained gssapi package.

:see: `.GSSAuth`
    """

if self._gss_deleg_creds:
            self._gss_flags = (
                gssapi.RequirementFlag.protection_ready,
                gssapi.RequirementFlag.integrity,
                gssapi.RequirementFlag.mutual_authentication,
                gssapi.RequirementFlag.delegate_to_peer,
            )
        else:
            self._gss_flags = (
                gssapi.RequirementFlag.protection_ready,
                gssapi.RequirementFlag.integrity,
                gssapi.RequirementFlag.mutual_authentication,
            )

def ssh_init_sec_context(
        self, target, desired_mech=None, username=None, recv_token=None
    ):
        """
        Initialize a GSS-API context.

:param str username: The name of the user who attempts to login
        :param str target: The hostname of the target to connect to
        :param str desired_mech: The negotiated GSS-API mechanism
                                 ("pseudo negotiated" mechanism, because we
                                 support just the krb5 mechanism :-))
        :param str recv_token: The GSS-API token received from the Server
        :raises: `.SSHException` -- Is raised if the desired mechanism of the
                 client is not supported
        :raises: ``gssapi.exceptions.GSSError`` if there is an error signaled
                                                by the GSS-API implementation
        :return: A ``String`` if the GSS-API has returned a token or ``None``
                 if no token was returned
        """
        from pyasn1.codec.der import decoder

self._username = username
        self._gss_host = target
        targ_name = gssapi.Name(
            "host@" + self._gss_host,
            name_type=gssapi.NameType.hostbased_service,
        )
        if desired_mech is not None:
            mech, __ = decoder.decode(desired_mech)
            if mech.__str__() != self._krb5_mech:
                raise SSHException("Unsupported mechanism OID.")
        krb5_mech = gssapi.MechType.kerberos
        token = None
        if recv_token is None:
            self._gss_ctxt = gssapi.SecurityContext(
                name=targ_name,
                flags=self._gss_flags,
                mech=krb5_mech,
                usage="initiate",
            )
            token = self._gss_ctxt.step(token)
        else:
            token = self._gss_ctxt.step(recv_token)
        self._gss_ctxt_status = self._gss_ctxt.complete
        return token

def ssh_get_mic(self, session_id, gss_kex=False):
        """
        Create the MIC token for a SSH2 message.

:param str session_id: The SSH session ID
        :param bool gss_kex: Generate the MIC for GSS-API Key Exchange or not
        :return: gssapi-with-mic:
                 Returns the MIC token from GSS-API for the message we created
                 with ``_ssh_build_mic``.
                 gssapi-keyex:
                 Returns the MIC token from GSS-API with the SSH session ID as
                 message.
        :rtype: str
        """
        self._session_id = session_id
        if not gss_kex:
            mic_field = self._ssh_build_mic(
                self._session_id,
                self._username,
                self._service,
                self._auth_method,
            )
            mic_token = self._gss_ctxt.get_signature(mic_field)
        else:
            # for key exchange with gssapi-keyex
            mic_token = self._gss_srv_ctxt.get_signature(self._session_id)
        return mic_token

def ssh_accept_sec_context(self, hostname, recv_token, username=None):
        """
        Accept a GSS-API context (server mode).

:param str hostname: The servers hostname
        :param str username: The name of the user who attempts to login
        :param str recv_token: The GSS-API Token received from the server,
                               if it's not the initial call.
        :return: A ``String`` if the GSS-API has returned a token or ``None``
                if no token was returned
        """
        # hostname and username are not required for GSSAPI, but for SSPI
        self._gss_host = hostname
        self._username = username
        if self._gss_srv_ctxt is None:
            self._gss_srv_ctxt = gssapi.SecurityContext(usage="accept")
        token = self._gss_srv_ctxt.step(recv_token)
        self._gss_srv_ctxt_status = self._gss_srv_ctxt.complete
        return token

def ssh_check_mic(self, mic_token, session_id, username=None):
        """
        Verify the MIC token for a SSH2 message.

:param str mic_token: The MIC token received from the client
        :param str session_id: The SSH session ID
        :param str username: The name of the user who attempts to login
        :return: None if the MIC check was successful
        :raises: ``gssapi.exceptions.GSSError`` -- if the MIC check failed
        """
        self._session_id = session_id
        self._username = username
        if self._username is not None:
            # server mode
            mic_field = self._ssh_build_mic(
                self._session_id,
                self._username,
                self._service,
                self._auth_method,
            )
            self._gss_srv_ctxt.verify_signature(mic_field, mic_token)
        else:
            # for key exchange with gssapi-keyex
            # client mode
            self._gss_ctxt.verify_signature(self._session_id, mic_token)

@property
    def credentials_delegated(self):
        """
        Checks if credentials are delegated (server mode).

:return: ``True`` if credentials are delegated, otherwise ``False``
        :rtype: bool
        """
        if self._gss_srv_ctxt.delegated_creds is not None:
            return True
        return False

:param str client_token: The GSS-API token received form the client
        :raises: ``NotImplementedError`` -- Credential delegation is currently
                 not supported in server mode
        """
        raise NotImplementedError

class _SSH_SSPI(_SSH_GSSAuth):
    """
    Implementation of the Microsoft SSPI Kerberos Authentication for SSH2.

:see: `.GSSAuth`
    """

if self._gss_deleg_creds:
            self._gss_flags = (
                sspicon.ISC_REQ_INTEGRITY
                | sspicon.ISC_REQ_MUTUAL_AUTH
                | sspicon.ISC_REQ_DELEGATE
            )
        else:
            self._gss_flags = (
                sspicon.ISC_REQ_INTEGRITY | sspicon.ISC_REQ_MUTUAL_AUTH
            )

def ssh_init_sec_context(
        self, target, desired_mech=None, username=None, recv_token=None
    ):
        """
        Initialize a SSPI context.

:param str username: The name of the user who attempts to login
        :param str target: The FQDN of the target to connect to
        :param str desired_mech: The negotiated SSPI mechanism
                                 ("pseudo negotiated" mechanism, because we
                                 support just the krb5 mechanism :-))
        :param recv_token: The SSPI token received from the Server
        :raises:
            `.SSHException` -- Is raised if the desired mechanism of the client
            is not supported
        :return: A ``String`` if the SSPI has returned a token or ``None`` if
                 no token was returned
        """
        from pyasn1.codec.der import decoder

self._username = username
        self._gss_host = target
        error = 0
        targ_name = "host/" + self._gss_host
        if desired_mech is not None:
            mech, __ = decoder.decode(desired_mech)
            if mech.__str__() != self._krb5_mech:
                raise SSHException("Unsupported mechanism OID.")
        try:
            if recv_token is None:
                self._gss_ctxt = sspi.ClientAuth(
                    "Kerberos", scflags=self._gss_flags, targetspn=targ_name
                )
            error, token = self._gss_ctxt.authorize(recv_token)
            token = token[0].Buffer
        except pywintypes.error as e:
            e.strerror += ", Target: {}".format(self._gss_host)
            raise

if error == 0:
            """
            if the status is GSS_COMPLETE (error = 0) the context is fully
            established an we can set _gss_ctxt_status to True.
            """
            self._gss_ctxt_status = True
            token = None
            """
            You won't get another token if the context is fully established,
            so i set token to None instead of ""
            """
        return token

def ssh_get_mic(self, session_id, gss_kex=False):
        """
        Create the MIC token for a SSH2 message.

:param str session_id: The SSH session ID
        :param bool gss_kex: Generate the MIC for Key Exchange with SSPI or not
        :return: gssapi-with-mic:
                 Returns the MIC token from SSPI for the message we created
                 with ``_ssh_build_mic``.
                 gssapi-keyex:
                 Returns the MIC token from SSPI with the SSH session ID as
                 message.
        """
        self._session_id = session_id
        if not gss_kex:
            mic_field = self._ssh_build_mic(
                self._session_id,
                self._username,
                self._service,
                self._auth_method,
            )
            mic_token = self._gss_ctxt.sign(mic_field)
        else:
            # for key exchange with gssapi-keyex
            mic_token = self._gss_srv_ctxt.sign(self._session_id)
        return mic_token

def ssh_accept_sec_context(self, hostname, username, recv_token):
        """
        Accept a SSPI context (server mode).

:param str hostname: The servers FQDN
        :param str username: The name of the user who attempts to login
        :param str recv_token: The SSPI Token received from the server,
                               if it's not the initial call.
        :return: A ``String`` if the SSPI has returned a token or ``None`` if
                 no token was returned
        """
        self._gss_host = hostname
        self._username = username
        targ_name = "host/" + self._gss_host
        self._gss_srv_ctxt = sspi.ServerAuth("Kerberos", spn=targ_name)
        error, token = self._gss_srv_ctxt.authorize(recv_token)
        token = token[0].Buffer
        if error == 0:
            self._gss_srv_ctxt_status = True
            token = None
        return token

def ssh_check_mic(self, mic_token, session_id, username=None):
        """
        Verify the MIC token for a SSH2 message.

:param str mic_token: The MIC token received from the client
        :param str session_id: The SSH session ID
        :param str username: The name of the user who attempts to login
        :return: None if the MIC check was successful
        :raises: ``sspi.error`` -- if the MIC check failed
        """
        self._session_id = session_id
        self._username = username
        if username is not None:
            # server mode
            mic_field = self._ssh_build_mic(
                self._session_id,
                self._username,
                self._service,
                self._auth_method,
            )
            # Verifies data and its signature.  If verification fails, an
            # sspi.error will be raised.
            self._gss_srv_ctxt.verify(mic_field, mic_token)
        else:
            # for key exchange with gssapi-keyex
            # client mode
            # Verifies data and its signature.  If verification fails, an
            # sspi.error will be raised.
            self._gss_ctxt.verify(self._session_id, mic_token)

@property
    def credentials_delegated(self):
        """
        Checks if credentials are delegated (server mode).

:return: ``True`` if credentials are delegated, otherwise ``False``
        """
        return self._gss_flags & sspicon.ISC_REQ_DELEGATE and (
            self._gss_srv_ctxt_status or self._gss_flags
        )

def save_client_creds(self, client_token):
        """
        Save the Client token in a file. This is used by the SSH server
        to store the client credentails if credentials are delegated
        (server mode).

:param str client_token: The SSPI token received form the client
        :raises:
            ``NotImplementedError`` -- Credential delegation is currently not
            supported in server mode
        """
        raise NotImplementedError

cmd: