ssh-audit/src/ssh_audit/writebuf.py

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"""
The MIT License (MIT)
Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
"""
import io
import struct
# pylint: disable=unused-import
from typing import Dict, List, Set, Sequence, Tuple, Iterable # noqa: F401
from typing import Callable, Optional, Union, Any # noqa: F401
class WriteBuf:
def __init__(self, data: Optional[bytes] = None) -> None:
super(WriteBuf, self).__init__()
self._wbuf = io.BytesIO(data) if data is not None else io.BytesIO()
def write(self, data: bytes) -> 'WriteBuf':
self._wbuf.write(data)
return self
def write_byte(self, v: int) -> 'WriteBuf':
return self.write(struct.pack('B', v))
def write_bool(self, v: bool) -> 'WriteBuf':
return self.write_byte(1 if v else 0)
def write_int(self, v: int) -> 'WriteBuf':
return self.write(struct.pack('>I', v))
def write_string(self, v: Union[bytes, str]) -> 'WriteBuf':
if not isinstance(v, bytes):
v = bytes(bytearray(v, 'utf-8'))
self.write_int(len(v))
return self.write(v)
def write_list(self, v: List[str]) -> 'WriteBuf':
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return self.write_string(','.join(v))
@classmethod
def _bitlength(cls, n: int) -> int:
try:
return n.bit_length()
except AttributeError:
return len(bin(n)) - (2 if n > 0 else 3)
@classmethod
def _create_mpint(cls, n: int, signed: bool = True, bits: Optional[int] = None) -> bytes:
if bits is None:
bits = cls._bitlength(n)
length = bits // 8 + (1 if n != 0 else 0)
ql = (length + 7) // 8
fmt, v2 = '>{}Q'.format(ql), [0] * ql
for i in range(ql):
v2[ql - i - 1] = n & 0xffffffffffffffff
n >>= 64
data = bytes(struct.pack(fmt, *v2)[-length:])
if not signed:
data = data.lstrip(b'\x00')
elif data.startswith(b'\xff\x80'):
data = data[1:]
return data
def write_mpint1(self, n: int) -> 'WriteBuf':
# NOTE: Data Type Enc @ http://www.snailbook.com/docs/protocol-1.5.txt
bits = self._bitlength(n)
data = self._create_mpint(n, False, bits)
self.write(struct.pack('>H', bits))
return self.write(data)
def write_mpint2(self, n: int) -> 'WriteBuf':
# NOTE: Section 5 @ https://www.ietf.org/rfc/rfc4251.txt
data = self._create_mpint(n)
return self.write_string(data)
def write_line(self, v: Union[bytes, str]) -> 'WriteBuf':
if not isinstance(v, bytes):
v = bytes(bytearray(v, 'utf-8'))
v += b'\r\n'
return self.write(v)
def write_flush(self) -> bytes:
payload = self._wbuf.getvalue()
self._wbuf.truncate(0)
self._wbuf.seek(0)
return payload
def reset(self) -> None:
self._wbuf = io.BytesIO()