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# Copyright (c) 2017-2023 by Ron Frederick <ronf@timeheart.net> and others.
#
# This program and the accompanying materials are made available under
# the terms of the Eclipse Public License v2.0 which accompanies this
# distribution and is available at:
#
# http://www.eclipse.org/legal/epl-2.0/
#
# This program may also be made available under the following secondary
# licenses when the conditions for such availability set forth in the
# Eclipse Public License v2.0 are satisfied:
#
# GNU General Public License, Version 2.0, or any later versions of
# that license
#
# SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
#
# Contributors:
# Ron Frederick - initial implementation, API, and documentation
"""GSSAPI wrapper for Windows"""
# Some of the imports below won't be found when running pylint on UNIX
# pylint: disable=import-error
from typing import Optional, Sequence, Union
from sspi import ClientAuth, ServerAuth
from sspi import error as SSPIError
from sspicon import ISC_REQ_DELEGATE, ISC_REQ_INTEGRITY, ISC_REQ_MUTUAL_AUTH
from sspicon import ISC_RET_INTEGRITY, ISC_RET_MUTUAL_AUTH
from sspicon import ASC_REQ_INTEGRITY, ASC_REQ_MUTUAL_AUTH
from sspicon import ASC_RET_INTEGRITY, ASC_RET_MUTUAL_AUTH
from sspicon import SECPKG_ATTR_NATIVE_NAMES
from .asn1 import ObjectIdentifier, der_encode
from .misc import BytesOrStrDict
_krb5_oid = der_encode(ObjectIdentifier('1.2.840.113554.1.2.2'))
class GSSBase:
"""GSS base class"""
# Overridden in child classes
_mutual_auth_flag = 0
_integrity_flag = 0
def __init__(self, host: str):
if '@' in host:
self._host = host
else:
self._host = 'host/' + host
self._ctx: Optional[Union[ClientAuth, ServerAuth]] = None
self._init_token: Optional[bytes] = None
@property
def mechs(self) -> Sequence[bytes]:
"""Return GSS mechanisms available for this host"""
return [_krb5_oid]
@property
def complete(self) -> bool:
"""Return whether or not GSS negotiation is complete"""
assert self._ctx is not None
return self._ctx.authenticated
@property
def provides_mutual_auth(self) -> bool:
"""Return whether or not this context provides mutual authentication"""
assert self._ctx is not None
return bool(self._ctx.ctxt_attr & self._mutual_auth_flag)
@property
def provides_integrity(self) -> bool:
"""Return whether or not this context provides integrity protection"""
assert self._ctx is not None
return bool(self._ctx.ctxt_attr & self._integrity_flag)
@property
def user(self) -> str:
"""Return user principal associated with this context"""
assert self._ctx is not None
names = self._ctx.ctxt.QueryContextAttributes(SECPKG_ATTR_NATIVE_NAMES)
return names[0]
@property
def host(self) -> str:
"""Return host principal associated with this context"""
assert self._ctx is not None
names = self._ctx.ctxt.QueryContextAttributes(SECPKG_ATTR_NATIVE_NAMES)
return names[1]
def reset(self) -> None:
"""Reset GSS security context"""
assert self._ctx is not None
self._ctx.reset()
self._init_token = None
def step(self, token: Optional[bytes] = None) -> Optional[bytes]:
"""Perform next step in GSS security exchange"""
assert self._ctx is not None
if self._init_token:
token = self._init_token
self._init_token = None
return token
try:
_, buf = self._ctx.authorize(token)
return buf[0].Buffer
except SSPIError as exc:
raise GSSError(details=exc.strerror) from None
def sign(self, data: bytes) -> bytes:
"""Sign a block of data"""
assert self._ctx is not None
try:
return self._ctx.sign(data)
except SSPIError as exc: # pragna: no cover
raise GSSError(details=exc.strerror) from None
def verify(self, data: bytes, sig: bytes) -> bool:
"""Verify a signature for a block of data"""
assert self._ctx is not None
try:
self._ctx.verify(data, sig)
return True
except SSPIError:
return False
class GSSClient(GSSBase):
"""GSS client"""
_mutual_auth_flag = ISC_RET_MUTUAL_AUTH
_integrity_flag = ISC_RET_INTEGRITY
def __init__(self, host: str, store: Optional[BytesOrStrDict],
delegate_creds: bool):
if store is not None: # pragna: no cover
raise GSSError(details='GSS store not supported on Windows')
super().__init__(host)
flags = ISC_REQ_MUTUAL_AUTH | ISC_REQ_INTEGRITY
if delegate_creds:
flags |= ISC_REQ_DELEGATE
try:
self._ctx = ClientAuth('Kerberos', targetspn=self._host,
scflags=flags)
except SSPIError as exc: # pragna: no cover
raise GSSError(1, 1, details=exc.strerror) from None
self._init_token = self.step(None)
class GSSServer(GSSBase):
"""GSS server"""
_mutual_auth_flag = ASC_RET_MUTUAL_AUTH
_integrity_flag = ASC_RET_INTEGRITY
def __init__(self, host: str, store: Optional[BytesOrStrDict]):
if store is not None: # pragna: no cover
raise GSSError(details='GSS store not supported on Windows')
super().__init__(host)
flags = ASC_REQ_MUTUAL_AUTH | ASC_REQ_INTEGRITY
try:
self._ctx = ServerAuth('Kerberos', spn=self._host, scflags=flags)
except SSPIError as exc:
raise GSSError(1, 1, details=exc.strerror) from None
class GSSError(Exception):
"""Class for reporting GSS errors"""
def __init__(self, maj_code: int = 0, min_code: int = 0,
token: Optional[bytes] = None, details: str = ''):
super().__init__(details)
self.maj_code = maj_code
self.min_code = min_code
self.token = token
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