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import socket
import socketserver
import struct
import logging
import OpenSSL.SSL
import pytds.tds_socket
import pytds.tds_reader
import pytds.tds_writer
import pytds.collate
_BYTE_STRUCT = struct.Struct("B")
_OFF_LEN_STRUCT = struct.Struct(">HH")
_PROD_VER_STRUCT = struct.Struct(">LH")
logger = logging.getLogger(__name__)
class TdsParser:
def bad_stream(self, msg):
# TODO use different exception class
raise Exception(msg)
def parse_prelogin(self, buf):
# https://msdn.microsoft.com/en-us/library/dd357559.aspx
size = len(buf)
i = 0
result = {}
while True:
value = None
if i >= size:
self.bad_stream("Invalid size of PRELOGIN structure")
(type_id,) = _BYTE_STRUCT.unpack_from(buf, i)
if type_id == pytds.tds_base.PreLoginToken.TERMINATOR:
break
if i + 4 > size:
self.bad_stream("Invalid size of PRELOGIN structure")
off, l = _OFF_LEN_STRUCT.unpack_from(buf, i + 1)
if off > size or off + l > size:
self.bad_stream("Invalid offset in PRELOGIN structure")
if type_id == pytds.tds_base.PreLoginToken.VERSION:
value = _PROD_VER_STRUCT.unpack_from(buf, off)
elif type_id == pytds.tds_base.PreLoginToken.ENCRYPTION:
value = _BYTE_STRUCT.unpack_from(buf, off)[0]
elif type_id == pytds.tds_base.PreLoginToken.MARS:
value = bool(_BYTE_STRUCT.unpack_from(buf, off)[0])
elif type_id == pytds.tds_base.PreLoginToken.INSTOPT:
value = buf[off : off + l].decode("ascii")
i += 5
result[type_id] = value
return result
class TdsGenerator:
def generate_prelogin(self, prelogin):
hdr_size = (1 + _OFF_LEN_STRUCT.size) * len(prelogin) + 1
buf = bytearray([0] * hdr_size)
hdr_offset = 0
data_offset = hdr_size
for type_id, value in prelogin.items():
if type_id == pytds.tds_base.PreLoginToken.VERSION:
packed = _PROD_VER_STRUCT.pack(value)
elif type_id == pytds.tds_base.PreLoginToken.ENCRYPTION:
packed = [value]
elif type_id == pytds.tds_base.PreLoginToken.MARS:
packed = [1 if value else 0]
elif type_id == pytds.tds_base.PreLoginToken.INSTOPT:
packed = value.encode("ascii")
else:
raise Exception(
f"not implemented prelogin option {type_id} in prelogin message generator"
)
data_size = len(packed)
buf[hdr_offset] = type_id
hdr_offset += 1
_OFF_LEN_STRUCT.pack_into(buf, hdr_offset, data_offset, data_size)
hdr_offset += _OFF_LEN_STRUCT.size
buf.extend(packed)
data_offset += data_size
buf[hdr_offset] = pytds.tds_base.PreLoginToken.TERMINATOR
return buf
class Sock:
# wraps request in class compatible with TdsSocket
def __init__(self, req):
self._req = req
def recv(self, size):
return self._req.recv(size)
def recv_into(self, buffer, size=0):
return self._req.recv_into(buffer, size)
def sendall(self, data, flags=0):
return self._req.sendall(data, flags)
class RequestHandler(socketserver.StreamRequestHandler):
def handle(self):
parser = TdsParser()
gen = TdsGenerator()
bufsize = 4096
# TdsReader expects this
self._transport = Sock(self.request)
r = pytds.tds_reader._TdsReader(tds_session=self, transport=self._transport)
w = pytds.tds_writer._TdsWriter(
tds_session=self, bufsize=bufsize, transport=self._transport
)
resp_header = r.begin_response()
buf = r.read_whole_packet()
if resp_header.type != pytds.tds_base.PacketType.PRELOGIN:
msg = "Invalid packet type: {0}, expected PRELOGIN({1})".format(
r.packet_type, pytds.tds_base.PacketType.PRELOGIN
)
self.bad_stream(msg)
prelogin = parser.parse_prelogin(buf)
logger.info(f"received prelogin message from client {prelogin}")
srv_enc = self.server._enc
cli_enc = prelogin[pytds.tds_base.PreLoginToken.ENCRYPTION]
res_enc = None
close_conn = False
if srv_enc == pytds.PreLoginEnc.ENCRYPT_OFF:
if cli_enc == pytds.PreLoginEnc.ENCRYPT_OFF:
res_enc = pytds.PreLoginEnc.ENCRYPT_OFF
elif cli_enc == pytds.PreLoginEnc.ENCRYPT_ON:
res_enc = pytds.PreLoginEnc.ENCRYPT_ON
elif cli_enc == pytds.PreLoginEnc.ENCRYPT_NOT_SUP:
res_enc = pytds.PreLoginEnc.ENCRYPT_NOT_SUP
elif srv_enc == pytds.PreLoginEnc.ENCRYPT_ON:
if cli_enc == pytds.PreLoginEnc.ENCRYPT_OFF:
res_enc = pytds.PreLoginEnc.ENCRYPT_REQ
elif cli_enc == pytds.PreLoginEnc.ENCRYPT_ON:
res_enc = pytds.PreLoginEnc.ENCRYPT_ON
elif cli_enc == pytds.PreLoginEnc.ENCRYPT_NOT_SUP:
res_enc = pytds.PreLoginEnc.ENCRYPT_REQ
close_conn = True
elif srv_enc == pytds.PreLoginEnc.ENCRYPT_NOT_SUP:
if cli_enc == pytds.PreLoginEnc.ENCRYPT_OFF:
res_enc = pytds.PreLoginEnc.ENCRYPT_NOT_SUP
elif cli_enc == pytds.PreLoginEnc.ENCRYPT_ON:
res_enc = pytds.PreLoginEnc.ENCRYPT_NOT_SUP
close_conn = True
elif cli_enc == pytds.PreLoginEnc.ENCRYPT_NOT_SUP:
res_enc = pytds.PreLoginEnc.ENCRYPT_NOT_SUP
elif srv_enc == pytds.PreLoginEnc.ENCRYPT_REQ:
res_enc = pytds.PreLoginEnc.ENCRYPT_REQ
# sending reply to client's prelogin packet
prelogin_resp = gen.generate_prelogin(
{
pytds.tds_base.PreLoginToken.ENCRYPTION: res_enc,
}
)
w.begin_packet(pytds.tds_base.PacketType.REPLY)
w.write(prelogin_resp)
w.flush()
if close_conn:
return
wrapped_socket = None
if res_enc != pytds.PreLoginEnc.ENCRYPT_NOT_SUP:
# setup TLS connection
tlsconn = OpenSSL.SSL.Connection(self.server._tls_ctx)
tlsconn.set_accept_state()
done = False
while not done:
try:
tlsconn.do_handshake()
except OpenSSL.SSL.WantReadError:
try:
buf = tlsconn.bio_read(bufsize)
except OpenSSL.SSL.WantReadError:
pass
else:
w.begin_packet(pytds.tds_base.PacketType.PRELOGIN)
w.write(buf)
w.flush()
r.begin_response()
buf = r.read_whole_packet()
tlsconn.bio_write(buf)
else:
done = True
try:
buf = tlsconn.bio_read(bufsize)
except OpenSSL.SSL.WantReadError:
pass
else:
w.begin_packet(pytds.tds_base.PacketType.PRELOGIN)
w.write(buf)
w.flush()
wrapped_socket = pytds.tls.EncryptedSocket(
transport=self.request, tls_conn=tlsconn
)
r._transport = wrapped_socket
w._transport = wrapped_socket
try:
r.begin_response()
buf = r.read_whole_packet()
except pytds.tds_base.ClosedConnectionError:
logger.info(
"client closed connection, probably did not like server certificate"
)
return
logger.info(f"received login packet from client {buf}")
if res_enc == pytds.PreLoginEnc.ENCRYPT_OFF:
wrapped_socket.shutdown()
r._transport = self._transport
w._transport = self._transport
srv_name = "Simple TDS Server"
srv_ver = (1, 0, 0, 0)
tds_version = self.server._tds_version
w.begin_packet(pytds.tds_base.PacketType.REPLY)
# https://msdn.microsoft.com/en-us/library/dd340651.aspx
srv_name_coded, _ = pytds.collate.ucs2_codec.encode(srv_name)
srv_name_size = len(srv_name_coded)
w.put_byte(pytds.tds_base.TDS_LOGINACK_TOKEN)
size = 1 + 4 + 1 + srv_name_size + 4
w.put_usmallint(size)
w.put_byte(1) # interface
w.put_uint_be(tds_version)
w.put_byte(len(srv_name))
w.write(srv_name_coded)
w.put_byte(srv_ver[0])
w.put_byte(srv_ver[1])
w.put_byte(srv_ver[2])
w.put_byte(srv_ver[3])
# https://msdn.microsoft.com/en-us/library/dd340421.aspx
w.put_byte(pytds.tds_base.TDS_DONE_TOKEN)
w.put_usmallint(0) # status
w.put_usmallint(0) # curcmd
w.put_uint8(0) # done row count
w.flush()
def bad_stream(self, msg):
raise Exception(msg)
class SimpleServer(socketserver.TCPServer):
allow_reuse_address = True
def __init__(
self, address, enc, cert=None, pkey=None, tds_version=pytds.tds_base.TDS74
):
self._enc = enc
super().__init__(address, RequestHandler)
ctx = None
if cert and pkey:
ctx = OpenSSL.SSL.Context(OpenSSL.SSL.TLSv1_2_METHOD)
ctx.set_options(OpenSSL.SSL.OP_NO_SSLv2)
ctx.set_options(OpenSSL.SSL.OP_NO_SSLv3)
ctx.use_certificate(cert)
ctx.use_privatekey(pkey)
self._tls_ctx = ctx
self._tds_version = tds_version
def set_ssl_context(self, ctx):
self._tls_ctx = ctx
def set_enc(self, enc):
self._enc = enc
def run(address):
logger.info("Starting server...")
with SimpleServer(address) as server:
logger.info("Press Ctrl+C to stop the server")
server.serve_forever()
if __name__ == "__main__":
run()
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