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# 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 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.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
from paramiko.common import max_byte, zero_byte
from paramiko.py3compat import b, byte_ord, byte_chr, long
import paramiko.util as util
class BERException (Exception):
pass
class BER(object):
"""
Robey's tiny little attempt at a BER decoder.
"""
def __init__(self, content=bytes()):
self.content = b(content)
self.idx = 0
def asbytes(self):
return self.content
def __str__(self):
return self.asbytes()
def __repr__(self):
return 'BER(\'' + repr(self.content) + '\')'
def decode(self):
return self.decode_next()
def decode_next(self):
if self.idx >= len(self.content):
return None
ident = byte_ord(self.content[self.idx])
self.idx += 1
if (ident & 31) == 31:
# identifier > 30
ident = 0
while self.idx < len(self.content):
t = byte_ord(self.content[self.idx])
self.idx += 1
ident = (ident << 7) | (t & 0x7f)
if not (t & 0x80):
break
if self.idx >= len(self.content):
return None
# now fetch length
size = byte_ord(self.content[self.idx])
self.idx += 1
if size & 0x80:
# more complimicated...
# FIXME: theoretically should handle indefinite-length (0x80)
t = size & 0x7f
if self.idx + t > len(self.content):
return None
size = util.inflate_long(self.content[self.idx: self.idx + t], True)
self.idx += t
if self.idx + size > len(self.content):
# can't fit
return None
data = self.content[self.idx: self.idx + size]
self.idx += size
# now switch on id
if ident == 0x30:
# sequence
return self.decode_sequence(data)
elif ident == 2:
# int
return util.inflate_long(data)
else:
# 1: boolean (00 false, otherwise true)
raise BERException('Unknown ber encoding type %d (robey is lazy)' % ident)
@staticmethod
def decode_sequence(data):
out = []
ber = BER(data)
while True:
x = ber.decode_next()
if x is None:
break
out.append(x)
return out
def encode_tlv(self, ident, val):
# no need to support ident > 31 here
self.content += byte_chr(ident)
if len(val) > 0x7f:
lenstr = util.deflate_long(len(val))
self.content += byte_chr(0x80 + len(lenstr)) + lenstr
else:
self.content += byte_chr(len(val))
self.content += val
def encode(self, x):
if type(x) is bool:
if x:
self.encode_tlv(1, max_byte)
else:
self.encode_tlv(1, zero_byte)
elif (type(x) is int) or (type(x) is long):
self.encode_tlv(2, util.deflate_long(x))
elif type(x) is str:
self.encode_tlv(4, x)
elif (type(x) is list) or (type(x) is tuple):
self.encode_tlv(0x30, self.encode_sequence(x))
else:
raise BERException('Unknown type for encoding: %s' % repr(type(x)))
@staticmethod
def encode_sequence(data):
ber = BER()
for item in data:
ber.encode(item)
return ber.asbytes()
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