# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
#
# 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 distrubuted 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.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
"""
Implementation of an SSH2 "message".
"""
import struct
import cStringIO
from paramiko import util
class Message (object):
"""
An SSH2 I{Message} is a stream of bytes that encodes some combination of
strings, integers, bools, and infinite-precision integers (known in python
as I{long}s). 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.
"""
def __init__(self, content=None):
"""
Create a new SSH2 Message.
@param content: the byte stream to use as the Message content (passed
in only when decomposing a Message).
@type content: string
"""
if content != None:
self.packet = cStringIO.StringIO(content)
else:
self.packet = cStringIO.StringIO()
def __str__(self):
"""
Return the byte stream content of this Message, as a string.
@return: the contents of this Message.
@rtype: string
"""
return self.packet.getvalue()
def __repr__(self):
"""
Returns a string representation of this object, for debugging.
@rtype: string
"""
return 'paramiko.Message(' + repr(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.
@return: a string of the bytes not parsed yet.
@rtype: string
"""
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 C{get_so_far} and L{get_remainder}.
@return: a string of the bytes parsed so far.
@rtype: string
"""
position = self.packet.tell()
self.rewind()
return self.packet.read(position)
def get_bytes(self, n):
"""
Return the next C{n} bytes of the Message, without decomposing into
an int, string, etc. Just the raw bytes are returned.
@return: a string of the next C{n} bytes of the Message, or a string
of C{n} zero bytes, if there aren't C{n} bytes remaining.
@rtype: string
"""
b = self.packet.read(n)
if len(b) < n:
return b + '\x00' * (n - len(b))
return b
def get_byte(self):
"""
Return the next byte of the Message, without decomposing it. This
is equivalent to L{get_bytes(1)<get_bytes>}.
@return: the next byte of the Message, or C{'\000'} if there aren't
any bytes remaining.
@rtype: string
"""
return self.get_bytes(1)
def get_boolean(self):
"""
Fetch a boolean from the stream.
@return: C{True} or C{False} (from the Message).
@rtype: bool
"""
b = self.get_bytes(1)
return b != '\x00'
def get_int(self):
"""
Fetch an int from the stream.
@return: a 32-bit unsigned integer.
@rtype: int
"""
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.
@rtype: long
"""
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.
@rtype: long
"""
return util.inflate_long(self.get_string())
def get_string(self):
"""
Fetch a string from the stream. This could be a byte string and may
contain unprintable characters. (It's not unheard of for a string to
contain another byte-stream Message.)
@return: a string.
@rtype: string
"""
return self.get_bytes(self.get_int())
def get_list(self):
"""
Fetch a list of strings from the stream. These are trivially encoded
as comma-separated values in a string.
@return: a list of strings.
@rtype: list of strings
"""
return self.get_string().split(',')
def add_bytes(self, b):
"""
Write bytes to the stream, without any formatting.
@param b: bytes to add
@type b: str
"""
self.packet.write(b)
return self
def add_byte(self, b):
"""
Write a single byte to the stream, without any formatting.
@param b: byte to add
@type b: str
"""
self.packet.write(b)
return self
def add_boolean(self, b):
"""
Add a boolean value to the stream.
@param b: boolean value to add
@type b: bool
"""
if b:
self.add_byte('\x01')
else:
self.add_byte('\x00')
return self
def add_int(self, n):
"""
Add an integer to the stream.
@param n: integer to add
@type n: int
"""
self.packet.write(struct.pack('>I', n))
return self
def add_int64(self, n):
"""
Add a 64-bit int to the stream.
@param n: long int to add
@type n: long
"""
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 z: long int to add
@type z: long
"""
self.add_string(util.deflate_long(z))
return self
def add_string(self, s):
"""
Add a string to the stream.
@param s: string to add
@type s: str
"""
self.add_int(len(s))
self.packet.write(s)
return self
def add_list(self, l):
"""
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
@type l: list(str)
"""
self.add_string(','.join(l))
return self
def _add(self, i):
if type(i) is str:
return self.add_string(i)
elif type(i) is int:
return self.add_int(i)
elif type(i) is long:
if i > 0xffffffffL:
return self.add_mpint(i)
else:
return self.add_int(i)
elif type(i) is bool:
return self.add_boolean(i)
elif type(i) is list:
return self.add_list(i)
else:
raise Exception('Unknown type')
def add(self, *seq):
"""
Add a sequence of items to the stream. The values are encoded based
on their type: str, int, bool, list, or long.
@param seq: the sequence of items
@type seq: sequence
@bug: longs are encoded non-deterministically. Don't use this method.
"""
for item in seq:
self._add(item)