# Copyright (C) 2003-2007 Robey Pointer <[email protected]>
#
# This file is part of paramiko.
#
# Paramiko is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Paramiko is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
Implementation of an SSH2 "message".
"""
import struct
from io import BytesIO
from paramiko import util
from paramiko.common import zero_byte, max_byte, one_byte
from paramiko.util import u
class Message:
"""
An SSH2 message is a stream of bytes that encodes some combination of
strings, integers, bools, and infinite-precision integers. This class
builds or breaks down such a byte stream.
Normally you don't need to deal with anything this low-level, but it's
exposed for people implementing custom extensions, or features that
paramiko doesn't support yet.
"""
big_int = 0xFF000000
def __init__(self, content=None):
"""
Create a new SSH2 message.
:param bytes content:
the byte stream to use as the message content (passed in only when
decomposing a message).
"""
if content is not None:
self.packet = BytesIO(content)
else:
self.packet = BytesIO()
def __bytes__(self):
return self.asbytes()
def __repr__(self):
"""
Returns a string representation of this object, for debugging.
"""
return "paramiko.Message(" + repr(self.packet.getvalue()) + ")"
# TODO 4.0: just merge into __bytes__ (everywhere)
def asbytes(self):
"""
Return the byte stream content of this Message, as a `bytes`.
"""
return self.packet.getvalue()
def rewind(self):
"""
Rewind the message to the beginning as if no items had been parsed
out of it yet.
"""
self.packet.seek(0)
def get_remainder(self):
"""
Return the `bytes` of this message that haven't already been parsed and
returned.
"""
position = self.packet.tell()
remainder = self.packet.read()
self.packet.seek(position)
return remainder
def get_so_far(self):
"""
Returns the `bytes` of this message that have been parsed and
returned. The string passed into a message's constructor can be
regenerated by concatenating ``get_so_far`` and `get_remainder`.
"""
position = self.packet.tell()
self.rewind()
return self.packet.read(position)
def get_bytes(self, n):
"""
Return the next ``n`` bytes of the message, without decomposing into an
int, decoded string, etc. Just the raw bytes are returned. Returns a
string of ``n`` zero bytes if there weren't ``n`` bytes remaining in
the message.
"""
b = self.packet.read(n)
max_pad_size = 1 << 20 # Limit padding to 1 MB
if len(b) < n < max_pad_size:
return b + zero_byte * (n - len(b))
return b
def get_byte(self):
"""
Return the next byte of the message, without decomposing it. This
is equivalent to `get_bytes(1) <get_bytes>`.
:return:
the next (`bytes`) byte of the message, or ``b'\000'`` if there
aren't any bytes remaining.
"""
return self.get_bytes(1)
def get_boolean(self):
"""
Fetch a boolean from the stream.
"""
b = self.get_bytes(1)
return b != zero_byte
def get_adaptive_int(self):
"""
Fetch an int from the stream.
:return: a 32-bit unsigned `int`.
"""
byte = self.get_bytes(1)
if byte == max_byte:
return util.inflate_long(self.get_binary())
byte += self.get_bytes(3)
return struct.unpack(">I", byte)[0]
def get_int(self):
"""
Fetch an int from the stream.
"""
return struct.unpack(">I", self.get_bytes(4))[0]
def get_int64(self):
"""
Fetch a 64-bit int from the stream.
:return: a 64-bit unsigned integer (`int`).
"""
return struct.unpack(">Q", self.get_bytes(8))[0]
def get_mpint(self):
"""
Fetch a long int (mpint) from the stream.
:return: an arbitrary-length integer (`int`).
"""
return util.inflate_long(self.get_binary())
# TODO 4.0: depending on where this is used internally or downstream, force
# users to specify get_binary instead and delete this.
def get_string(self):
"""
Fetch a "string" from the stream. This will actually be a `bytes`
object, and may contain unprintable characters. (It's not unheard of
for a string to contain another byte-stream message.)
"""
return self.get_bytes(self.get_int())
# TODO 4.0: also consider having this take over the get_string name, and
# remove this name instead.
def get_text(self):
"""
Fetch a Unicode string from the stream.
This currently operates by attempting to encode the next "string" as
``utf-8``.
"""
return u(self.get_string())
def get_binary(self):
"""
Alias for `get_string` (obtains a bytestring).
"""
return self.get_bytes(self.get_int())
def get_list(self):
"""
Fetch a list of `strings <str>` from the stream.
These are trivially encoded as comma-separated values in a string.
"""
return self.get_text().split(",")
def add_bytes(self, b):
"""
Write bytes to the stream, without any formatting.
:param bytes b: bytes to add
"""
self.packet.write(b)
return self
def add_byte(self, b):
"""
Write a single byte to the stream, without any formatting.
:param bytes b: byte to add
"""
self.packet.write(b)
return self
def add_boolean(self, b):
"""
Add a boolean value to the stream.
:param bool b: boolean value to add
"""
if b:
self.packet.write(one_byte)
else:
self.packet.write(zero_byte)
return self
def add_int(self, n):
"""
Add an integer to the stream.
:param int n: integer to add
"""
self.packet.write(struct.pack(">I", n))
return self
def add_adaptive_int(self, n):
"""
Add an integer to the stream.
:param int n: integer to add
"""
if n >= Message.big_int:
self.packet.write(max_byte)
self.add_string(util.deflate_long(n))
else:
self.packet.write(struct.pack(">I", n))
return self
def add_int64(self, n):
"""
Add a 64-bit int to the stream.
:param int n: long int to add
"""
self.packet.write(struct.pack(">Q", n))
return self
def add_mpint(self, z):
"""
Add a long int to the stream, encoded as an infinite-precision
integer. This method only works on positive numbers.
:param int z: long int to add
"""
self.add_string(util.deflate_long(z))
return self
# TODO: see the TODO for get_string/get_text/et al, this should change
# to match.
def add_string(self, s):
"""
Add a bytestring to the stream.
:param byte s: bytestring to add
"""
s = util.asbytes(s)
self.add_int(len(s))
self.packet.write(s)
return self
def add_list(self, l): # noqa: E741
"""
Add a list of strings to the stream. They are encoded identically to
a single string of values separated by commas. (Yes, really, that's
how SSH2 does it.)
:param l: list of strings to add
"""
self.add_string(",".join(l))
return self
def _add(self, i):
if type(i) is bool:
return self.add_boolean(i)
elif isinstance(i, int):
return self.add_adaptive_int(i)
elif type(i) is list:
return self.add_list(i)
else:
return self.add_string(i)
# TODO: this would never have worked for unicode strings under Python 3,
# guessing nobody/nothing ever used it for that purpose?
def add(self, *seq):
"""
Add a sequence of items to the stream. The values are encoded based
on their type: bytes, str, int, bool, or list.
.. warning::
Longs are encoded non-deterministically. Don't use this method.
:param seq: the sequence of items
"""
for item in seq:
self._add(item)