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#!/usr/bin/python
# Copyright (C) 2003-2004 Robey Pointer <robey@lag.net>
#
# 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 Foobar; 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 string, types, struct
from util import inflate_long, deflate_long
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.
"""
def __init__(self, content=''):
"""
Create a new SSH2 Message.
@param content: the byte stream to use as the Message content (usually
passed in only when decomposing a Message).
@type content: string
"""
self.packet = content
self.idx = 0
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
def __repr__(self):
"""
Returns a string representation of this object, for debugging.
@rtype: string
"""
return 'Message(' + repr(self.packet) + ')'
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
"""
return self.packet[self.idx:]
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
"""
return self.packet[:self.idx]
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
"""
if self.idx + n > len(self.packet):
return '\x00'*n
b = self.packet[self.idx:self.idx+n]
self.idx = self.idx + n
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)
if b == '\x00':
return False
else:
return True
def get_int(self):
"""
Fetch an int from the stream.
@return: a 32-bit unsigned integer.
@rtype: int
"""
x = self.packet
i = self.idx
if i + 4 > len(x):
return 0
n = struct.unpack('>I', x[i:i+4])[0]
self.idx = i+4
return n
def get_int64(self):
"""
Fetch a 64-bit int from the stream.
@return: a 64-bit unsigned integer.
@rtype: long
"""
x = self.packet
i = self.idx
if i + 8 > len(x):
return 0L
n = struct.unpack('>Q', x[i:i+8])[0]
self.idx += 8
return n
def get_mpint(self):
"""
Fetch a long int (mpint) from the stream.
@return: an arbitrary-length integer.
@rtype: long
"""
return 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
"""
l = self.get_int()
if self.idx + l > len(self.packet):
return ''
str = self.packet[self.idx:self.idx+l]
self.idx = self.idx + l
return str
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
"""
str = self.get_string()
l = string.split(str, ',')
return l
def add_bytes(self, b):
self.packet = self.packet + b
return self
def add_byte(self, b):
self.packet = self.packet + b
return self
def add_boolean(self, b):
if b:
self.add_byte('\x01')
else:
self.add_byte('\x00')
return self
def add_int(self, n):
self.packet = self.packet + 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 = self.packet + struct.pack('>Q', n)
return self
def add_mpint(self, z):
"this only works on positive numbers"
self.add_string(deflate_long(z))
return self
def add_string(self, s):
self.add_int(len(s))
self.packet = self.packet + s
return self
def add_list(self, l):
out = string.join(l, ',')
self.add_int(len(out))
self.packet = self.packet + out
return self
def add(self, i):
if type(i) == types.StringType:
return self.add_string(i)
elif type(i) == types.IntType:
return self.add_int(i)
elif type(i) == types.LongType:
if i > 0xffffffffL:
return self.add_mpint(i)
else:
return self.add_int(i)
elif type(i) == types.ListType:
return self.add_list(i)
else:
raise exception('Unknown type')
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