1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
|
"""TLS serialization."""
import math
from ct.proto import tls_options_pb2 as options
from google.protobuf import descriptor
class Error(Exception):
pass
class TLSDecodingError(Error):
"""Decoding failed."""
pass
class TLSEncodingError(Error):
"""Encoding failed."""
pass
class TLSReader(object):
"""Read serialized TLS messages into a protocol buffer."""
def __init__(self, serialized_buffer):
# It would be nice to use BytesIO but it has no efficient way of
# testing whether it's empty without advancing the position, so
# we have to keep track of the position manually.
self._buf = serialized_buffer
self._pos = 0
def _read_fixed_bytes(self, num_bytes):
if self._pos + num_bytes > len(self._buf):
raise TLSDecodingError("Buffer underrun: need %d bytes, have "
"%d bytes" % (num_bytes,
len(self._buf) - self._pos))
ret = self._buf[self._pos:self._pos + num_bytes]
self._pos += num_bytes
return ret
def finished(self):
return self._pos >= len(self._buf)
def verify_finished(self):
if not self.finished():
raise TLSDecodingError("Bytes remaining in the buffer")
def _read_uint(self, num_bytes):
int_bytes = bytearray(self._read_fixed_bytes(num_bytes))
ret = 0
for b in int_bytes:
ret <<= 8
ret += b
return ret
def _read_bounded_uint(self, min_value, max_value):
length_of_value = int(math.ceil(math.log(max_value + 1, 256)))
value = self._read_uint(length_of_value)
if value < min_value or value > max_value:
raise TLSDecodingError("Value %d is out of range ([%d, %d])" %
(value, min_value, max_value))
return value
def _read_uint32(self, opts):
return self._read_uint(opts.bytes_in_use or 4)
def _read_uint64(self, opts):
return self._read_uint(opts.bytes_in_use or 8)
def _read_enum(self, opts):
if not opts.max_value:
raise TypeError("Enum field has no maximum value")
return self._read_bounded_uint(0, opts.max_value)
def _read_var_bytes(self, min_length, max_length):
length = self._read_bounded_uint(min_length, max_length)
return self._read_fixed_bytes(length)
def _read_bytes(self, opts):
if opts.fixed_length:
return self._read_fixed_bytes(opts.fixed_length)
elif opts.max_length:
return self._read_var_bytes(opts.min_length, opts.max_length)
else:
raise TypeError("Byte field has no length limit")
def _get_read_method(self, field):
if field.type == descriptor.FieldDescriptor.TYPE_UINT32:
return self._read_uint32
elif field.type == descriptor.FieldDescriptor.TYPE_UINT64:
return self._read_uint64
elif field.type == descriptor.FieldDescriptor.TYPE_ENUM:
return self._read_enum
elif field.type == descriptor.FieldDescriptor.TYPE_BYTES:
return self._read_bytes
else:
raise TypeError("Field %s of type %d not supported" %
(field.name, field.type))
def _read_repeated(self, message, field, opts):
"""Read a repeated field."""
if not opts.max_total_length:
raise TypeError("Repeated field %s has no length limit" %
field.name)
# Recursive, naive.
reader = TLSReader(self._read_var_bytes(opts.min_total_length,
opts.max_total_length))
target = getattr(message, field.name)
if field.type == field.TYPE_MESSAGE:
while not reader.finished():
new_message = target.add()
reader.read(new_message)
else:
if field.type == field.TYPE_ENUM:
opts = field.enum_type.GetOptions().Extensions[
options.tls_enum_opts]
# |reader| is another member of this class.
# pylint: disable=protected-access
read_method = reader._get_read_method(field)
while not reader.finished():
target.append(read_method(opts))
def read(self, message):
"""Read from the buffer into the protocol buffer message."""
# TODO(ekasper): probably better not to modify the
# original message until we're guaranteed to succeed?
fields = message.DESCRIPTOR.fields_by_number
for i in sorted(fields):
field = fields[i]
opts = field.GetOptions().Extensions[options.tls_opts]
if opts.skip:
continue
if opts.select_field:
value = getattr(message, opts.select_field)
if value != opts.select_value:
continue
if field.label == field.LABEL_REPEATED:
self._read_repeated(message, field, opts)
elif field.type == field.TYPE_MESSAGE:
self.read(getattr(message, field.name))
else:
if field.type == field.TYPE_ENUM:
opts = field.enum_type.GetOptions().Extensions[
options.tls_enum_opts]
setattr(message, field.name,
self._get_read_method(field)(opts))
@classmethod
def decode(cls, buf, message):
reader = cls(buf)
reader.read(message)
reader.verify_finished()
class TLSWriter(object):
"""Serialize protocol buffers into TLS wire format."""
def __init__(self):
self._buf = bytearray()
def __len__(self):
"""Current length of the result."""
return len(self._buf)
def get_serialized_result(self):
"""Get the serialized contents."""
return str(self._buf)
def _write_uint(self, value, num_bytes):
int_bytes = bytearray()
for _ in range(num_bytes):
int_bytes.append(value & 0xff)
value >>= 8
if value:
raise TLSEncodingError("Value %d is too large to fit in %d bytes" %
(value, num_bytes))
int_bytes.reverse()
self._buf.extend(int_bytes)
def _write_bounded_uint(self, value, min_value, max_value):
if value < min_value or value > max_value:
raise TLSEncodingError("Value %d out of range ([%d, %d])" %
(value, min_value, max_value))
length_of_value = int(math.ceil(math.log(max_value + 1, 256)))
self._write_uint(value, length_of_value)
def _write_uint32(self, value, opts):
self._write_uint(value, opts.bytes_in_use or 4)
def _write_uint64(self, value, opts):
self._write_uint(value, opts.bytes_in_use or 8)
def _write_enum(self, value, opts):
if not opts.max_value:
raise TypeError("Enum field has no maximum value")
self._write_bounded_uint(value, 0, opts.max_value)
def _write_fixed_bytes(self, value, length):
if len(value) != length:
raise TLSEncodingError("Invalid value %s of length %d: required "
"length is %d" % (value, len(value), length))
self._buf.extend(value)
def _write_var_bytes(self, value, min_length, max_length):
self._write_bounded_uint(len(value), min_length, max_length)
self._buf.extend(value)
def _write_bytes(self, value, opts):
if opts.fixed_length:
return self._write_fixed_bytes(value, opts.fixed_length)
elif opts.max_length:
return self._write_var_bytes(value, opts.min_length,
opts.max_length)
else:
raise TypeError("Byte field has no length limit")
def _get_write_method(self, field):
if field.type == descriptor.FieldDescriptor.TYPE_UINT32:
return self._write_uint32
elif field.type == descriptor.FieldDescriptor.TYPE_UINT64:
return self._write_uint64
elif field.type == descriptor.FieldDescriptor.TYPE_ENUM:
return self._write_enum
elif field.type == descriptor.FieldDescriptor.TYPE_BYTES:
return self._write_bytes
else:
raise TypeError("Field %s of type %d not supported" %
(field.name, field.type))
def _write_repeated(self, message, field, opts):
"""Write a repeated field."""
writer = TLSWriter()
if field.type == field.TYPE_MESSAGE:
# Recursive, naive: could instead read ahead to determine
# the total length first.
for elem in getattr(message, field.name):
writer.write(elem)
else:
if field.type == field.TYPE_ENUM:
opts = field.enum_type.GetOptions().Extensions[
options.tls_enum_opts]
# pylint: disable=protected-access
write_method = writer._get_write_method(field)
for elem in getattr(message, field.name):
write_method(elem, opts)
length = len(writer)
self._write_bounded_uint(length, opts.min_total_length,
opts.max_total_length)
self._buf.extend(writer._buf) # pylint: disable=protected-access
def write(self, message):
"""Append a serialized message to the writer's buffer."""
fields = message.DESCRIPTOR.fields_by_number
for i in sorted(fields):
field = fields[i]
opts = field.GetOptions().Extensions[options.tls_opts]
if opts.skip:
continue
if opts.select_field:
value = getattr(message, opts.select_field)
if value != opts.select_value:
continue
if field.label == field.LABEL_REPEATED:
self._write_repeated(message, field, opts)
elif field.type == field.TYPE_MESSAGE:
self.write(getattr(message, field.name))
else:
if field.type == field.TYPE_ENUM:
opts = field.enum_type.GetOptions().Extensions[
options.tls_enum_opts]
self._get_write_method(field)(getattr(message, field.name),
opts)
@classmethod
def encode(cls, message):
writer = cls()
writer.write(message)
return writer.get_serialized_result()
def encode(message):
return TLSWriter.encode(message)
def decode(buf, message):
TLSReader.decode(buf, message)
|
