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139 lines
4.2 KiB
Python
139 lines
4.2 KiB
Python
# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
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#
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# This file is part of paramiko.
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#
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# Paramiko is free software; you can redistribute it and/or modify it under the
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# terms of the GNU Lesser General Public License as published by the Free
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# Software Foundation; either version 2.1 of the License, or (at your option)
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# any later version.
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#
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# Paramiko is distributed in the hope that it will be useful, but WITHOUT ANY
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# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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# details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
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# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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from paramiko.common import max_byte, zero_byte
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from paramiko.py3compat import b, byte_ord, byte_chr, long
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import paramiko.util as util
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class BERException(Exception):
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pass
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class BER(object):
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"""
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Robey's tiny little attempt at a BER decoder.
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"""
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def __init__(self, content=bytes()):
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self.content = b(content)
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self.idx = 0
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def asbytes(self):
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return self.content
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def __str__(self):
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return self.asbytes()
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def __repr__(self):
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return "BER('" + repr(self.content) + "')"
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def decode(self):
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return self.decode_next()
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def decode_next(self):
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if self.idx >= len(self.content):
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return None
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ident = byte_ord(self.content[self.idx])
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self.idx += 1
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if (ident & 31) == 31:
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# identifier > 30
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ident = 0
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while self.idx < len(self.content):
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t = byte_ord(self.content[self.idx])
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self.idx += 1
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ident = (ident << 7) | (t & 0x7f)
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if not (t & 0x80):
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break
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if self.idx >= len(self.content):
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return None
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# now fetch length
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size = byte_ord(self.content[self.idx])
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self.idx += 1
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if size & 0x80:
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# more complimicated...
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# FIXME: theoretically should handle indefinite-length (0x80)
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t = size & 0x7f
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if self.idx + t > len(self.content):
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return None
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size = util.inflate_long(
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self.content[self.idx : self.idx + t], True
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)
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self.idx += t
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if self.idx + size > len(self.content):
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# can't fit
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return None
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data = self.content[self.idx : self.idx + size]
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self.idx += size
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# now switch on id
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if ident == 0x30:
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# sequence
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return self.decode_sequence(data)
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elif ident == 2:
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# int
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return util.inflate_long(data)
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else:
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# 1: boolean (00 false, otherwise true)
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msg = "Unknown ber encoding type {:d} (robey is lazy)"
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raise BERException(msg.format(ident))
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@staticmethod
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def decode_sequence(data):
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out = []
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ber = BER(data)
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while True:
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x = ber.decode_next()
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if x is None:
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break
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out.append(x)
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return out
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def encode_tlv(self, ident, val):
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# no need to support ident > 31 here
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self.content += byte_chr(ident)
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if len(val) > 0x7f:
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lenstr = util.deflate_long(len(val))
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self.content += byte_chr(0x80 + len(lenstr)) + lenstr
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else:
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self.content += byte_chr(len(val))
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self.content += val
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def encode(self, x):
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if type(x) is bool:
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if x:
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self.encode_tlv(1, max_byte)
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else:
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self.encode_tlv(1, zero_byte)
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elif (type(x) is int) or (type(x) is long):
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self.encode_tlv(2, util.deflate_long(x))
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elif type(x) is str:
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self.encode_tlv(4, x)
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elif (type(x) is list) or (type(x) is tuple):
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self.encode_tlv(0x30, self.encode_sequence(x))
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else:
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raise BERException(
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"Unknown type for encoding: {!r}".format(type(x))
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)
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@staticmethod
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def encode_sequence(data):
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ber = BER()
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for item in data:
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ber.encode(item)
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return ber.asbytes()
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