227 lines
9.4 KiB
Python
227 lines
9.4 KiB
Python
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"""
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Helper classes for SSPI authentication via the win32security module.
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SSPI authentication involves a token-exchange "dance", the exact details
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of which depends on the authentication provider used. There are also
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a number of complex flags and constants that need to be used - in most
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cases, there are reasonable defaults.
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These classes attempt to hide these details from you until you really need
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to know. They are not designed to handle all cases, just the common ones.
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If you need finer control than offered here, just use the win32security
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functions directly.
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"""
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# Based on Roger Upole's sspi demos.
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# $Id$
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import win32security, sspicon
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error = win32security.error
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class _BaseAuth(object):
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def __init__(self):
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self.reset()
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def reset(self):
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"""Reset everything to an unauthorized state"""
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self.ctxt = None
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self.authenticated = False
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# The next seq_num for an encrypt/sign operation
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self.next_seq_num = 0
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def _get_next_seq_num(self):
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"""Get the next sequence number for a transmission. Default
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implementation is to increment a counter
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"""
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ret = self.next_seq_num
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self.next_seq_num = self.next_seq_num + 1
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return ret
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def encrypt(self, data):
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"""Encrypt a string, returning a tuple of (encrypted_data, encryption_data).
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These can be passed to decrypt to get back the original string.
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"""
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pkg_size_info=self.ctxt.QueryContextAttributes(sspicon.SECPKG_ATTR_SIZES)
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trailersize=pkg_size_info['SecurityTrailer']
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encbuf=win32security.PySecBufferDescType()
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encbuf.append(win32security.PySecBufferType(len(data), sspicon.SECBUFFER_DATA))
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encbuf.append(win32security.PySecBufferType(trailersize, sspicon.SECBUFFER_TOKEN))
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encbuf[0].Buffer=data
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self.ctxt.EncryptMessage(0,encbuf,self._get_next_seq_num())
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return encbuf[0].Buffer, encbuf[1].Buffer
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def decrypt(self, data, trailer):
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"""Decrypt a previously encrypted string, returning the orignal data"""
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encbuf=win32security.PySecBufferDescType()
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encbuf.append(win32security.PySecBufferType(len(data), sspicon.SECBUFFER_DATA))
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encbuf.append(win32security.PySecBufferType(len(trailer), sspicon.SECBUFFER_TOKEN))
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encbuf[0].Buffer=data
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encbuf[1].Buffer=trailer
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self.ctxt.DecryptMessage(encbuf,self._get_next_seq_num())
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return encbuf[0].Buffer
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def sign(self, data):
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"""sign a string suitable for transmission, returning the signature.
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Passing the data and signature to verify will determine if the data
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is unchanged.
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"""
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pkg_size_info=self.ctxt.QueryContextAttributes(sspicon.SECPKG_ATTR_SIZES)
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sigsize=pkg_size_info['MaxSignature']
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sigbuf=win32security.PySecBufferDescType()
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sigbuf.append(win32security.PySecBufferType(len(data), sspicon.SECBUFFER_DATA))
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sigbuf.append(win32security.PySecBufferType(sigsize, sspicon.SECBUFFER_TOKEN))
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sigbuf[0].Buffer=data
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self.ctxt.MakeSignature(0,sigbuf,self._get_next_seq_num())
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return sigbuf[1].Buffer
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def verify(self, data, sig):
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"""Verifies data and its signature. If verification fails, an sspi.error
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will be raised.
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"""
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sigbuf=win32security.PySecBufferDescType()
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sigbuf.append(win32security.PySecBufferType(len(data), sspicon.SECBUFFER_DATA))
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sigbuf.append(win32security.PySecBufferType(len(sig), sspicon.SECBUFFER_TOKEN))
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sigbuf[0].Buffer=data
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sigbuf[1].Buffer=sig
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self.ctxt.VerifySignature(sigbuf,self._get_next_seq_num())
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class ClientAuth(_BaseAuth):
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"""Manages the client side of an SSPI authentication handshake
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"""
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def __init__(self,
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pkg_name, # Name of the package to used.
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client_name = None, # User for whom credentials are used.
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auth_info = None, # or a tuple of (username, domain, password)
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targetspn = None, # Target security context provider name.
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scflags=None, # security context flags
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datarep=sspicon.SECURITY_NETWORK_DREP):
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if scflags is None:
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scflags = sspicon.ISC_REQ_INTEGRITY|sspicon.ISC_REQ_SEQUENCE_DETECT|\
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sspicon.ISC_REQ_REPLAY_DETECT|sspicon.ISC_REQ_CONFIDENTIALITY
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self.scflags=scflags
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self.datarep=datarep
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self.targetspn=targetspn
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self.pkg_info=win32security.QuerySecurityPackageInfo(pkg_name)
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self.credentials, \
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self.credentials_expiry=win32security.AcquireCredentialsHandle(
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client_name, self.pkg_info['Name'],
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sspicon.SECPKG_CRED_OUTBOUND,
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None, auth_info)
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_BaseAuth.__init__(self)
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# Perform *one* step of the client authentication process.
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def authorize(self, sec_buffer_in):
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if sec_buffer_in is not None and type(sec_buffer_in) != win32security.PySecBufferDescType:
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# User passed us the raw data - wrap it into a SecBufferDesc
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sec_buffer_new=win32security.PySecBufferDescType()
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tokenbuf=win32security.PySecBufferType(self.pkg_info['MaxToken'],
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sspicon.SECBUFFER_TOKEN)
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tokenbuf.Buffer=sec_buffer_in
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sec_buffer_new.append(tokenbuf)
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sec_buffer_in = sec_buffer_new
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sec_buffer_out=win32security.PySecBufferDescType()
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tokenbuf=win32security.PySecBufferType(self.pkg_info['MaxToken'], sspicon.SECBUFFER_TOKEN)
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sec_buffer_out.append(tokenbuf)
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## input context handle should be NULL on first call
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ctxtin=self.ctxt
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if self.ctxt is None:
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self.ctxt=win32security.PyCtxtHandleType()
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err, attr, exp=win32security.InitializeSecurityContext(
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self.credentials,
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ctxtin,
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self.targetspn,
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self.scflags,
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self.datarep,
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sec_buffer_in,
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self.ctxt,
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sec_buffer_out)
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# Stash these away incase someone needs to know the state from the
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# final call.
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self.ctxt_attr = attr
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self.ctxt_expiry = exp
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if err in (sspicon.SEC_I_COMPLETE_NEEDED,sspicon.SEC_I_COMPLETE_AND_CONTINUE):
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self.ctxt.CompleteAuthToken(sec_buffer_out)
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self.authenticated = err == 0
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return err, sec_buffer_out
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class ServerAuth(_BaseAuth):
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"""Manages the server side of an SSPI authentication handshake
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"""
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def __init__(self,
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pkg_name,
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spn = None,
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scflags=None,
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datarep=sspicon.SECURITY_NETWORK_DREP):
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self.spn=spn
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self.datarep=datarep
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if scflags is None:
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scflags = sspicon.ASC_REQ_INTEGRITY|sspicon.ASC_REQ_SEQUENCE_DETECT|\
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sspicon.ASC_REQ_REPLAY_DETECT|sspicon.ASC_REQ_CONFIDENTIALITY
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# Should we default to sspicon.KerbAddExtraCredentialsMessage
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# if pkg_name=='Kerberos'?
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self.scflags=scflags
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self.pkg_info=win32security.QuerySecurityPackageInfo(pkg_name)
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self.credentials, \
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self.credentials_expiry=win32security.AcquireCredentialsHandle(spn,
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self.pkg_info['Name'], sspicon.SECPKG_CRED_INBOUND, None, None)
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_BaseAuth.__init__(self)
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# Perform *one* step of the server authentication process.
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def authorize(self, sec_buffer_in):
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if sec_buffer_in is not None and type(sec_buffer_in) != win32security.PySecBufferDescType:
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# User passed us the raw data - wrap it into a SecBufferDesc
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sec_buffer_new=win32security.PySecBufferDescType()
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tokenbuf=win32security.PySecBufferType(self.pkg_info['MaxToken'],
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sspicon.SECBUFFER_TOKEN)
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tokenbuf.Buffer=sec_buffer_in
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sec_buffer_new.append(tokenbuf)
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sec_buffer_in = sec_buffer_new
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sec_buffer_out=win32security.PySecBufferDescType()
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tokenbuf=win32security.PySecBufferType(self.pkg_info['MaxToken'], sspicon.SECBUFFER_TOKEN)
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sec_buffer_out.append(tokenbuf)
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## input context handle is None initially, then handle returned from last call thereafter
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ctxtin=self.ctxt
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if self.ctxt is None:
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self.ctxt=win32security.PyCtxtHandleType()
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err, attr, exp = win32security.AcceptSecurityContext(self.credentials, ctxtin,
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sec_buffer_in, self.scflags,
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self.datarep, self.ctxt, sec_buffer_out)
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# Stash these away incase someone needs to know the state from the
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# final call.
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self.ctxt_attr = attr
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self.ctxt_expiry = exp
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if err in (sspicon.SEC_I_COMPLETE_NEEDED,sspicon.SEC_I_COMPLETE_AND_CONTINUE):
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self.ctxt.CompleteAuthToken(sec_buffer_out)
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self.authenticated = err == 0
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return err, sec_buffer_out
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if __name__=='__main__':
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# Setup the 2 contexts.
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sspiclient=ClientAuth("NTLM")
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sspiserver=ServerAuth("NTLM")
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# Perform the authentication dance, each loop exchanging more information
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# on the way to completing authentication.
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sec_buffer=None
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while 1:
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err, sec_buffer = sspiclient.authorize(sec_buffer)
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err, sec_buffer = sspiserver.authorize(sec_buffer)
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if err==0:
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break
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data = "hello".encode("ascii") # py3k-friendly
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sig = sspiclient.sign(data)
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sspiserver.verify(data, sig)
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data, key = sspiclient.encrypt(data)
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assert sspiserver.decrypt(data, key) == data
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print("cool!")
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