codekingpro/portable-devtools

1# Copyright (C) 2003-2007  Robey Pointer <robeypointer@gmail.com>2#3# This file is part of paramiko.4#5# Paramiko is free software; you can redistribute it and/or modify it under the6# terms of the GNU Lesser General Public License as published by the Free7# Software Foundation; either version 2.1 of the License, or (at your option)8# any later version.9#10# Paramiko is distributed in the hope that it will be useful, but WITHOUT ANY11# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR12# A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more13# details.14#15# You should have received a copy of the GNU Lesser General Public License16# along with Paramiko; if not, write to the Free Software Foundation, Inc.,17# 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA.18from paramiko.common import max_byte, zero_byte, byte_ord, byte_chr19 20import paramiko.util as util21from paramiko.util import b22from paramiko.sftp import int6423 24 25class BERException(Exception):26    pass27 28 29class BER:30    """31    Robey's tiny little attempt at a BER decoder.32    """33 34    def __init__(self, content=bytes()):35        self.content = b(content)36        self.idx = 037 38    def asbytes(self):39        return self.content40 41    def __str__(self):42        return self.asbytes()43 44    def __repr__(self):45        return "BER('" + repr(self.content) + "')"46 47    def decode(self):48        return self.decode_next()49 50    def decode_next(self):51        if self.idx >= len(self.content):52            return None53        ident = byte_ord(self.content[self.idx])54        self.idx += 155        if (ident & 31) == 31:56            # identifier > 3057            ident = 058            while self.idx < len(self.content):59                t = byte_ord(self.content[self.idx])60                self.idx += 161                ident = (ident << 7) | (t & 0x7F)62                if not (t & 0x80):63                    break64        if self.idx >= len(self.content):65            return None66        # now fetch length67        size = byte_ord(self.content[self.idx])68        self.idx += 169        if size & 0x80:70            # more complimicated...71            # FIXME: theoretically should handle indefinite-length (0x80)72            t = size & 0x7F73            if self.idx + t > len(self.content):74                return None75            size = util.inflate_long(76                self.content[self.idx : self.idx + t], True77            )78            self.idx += t79        if self.idx + size > len(self.content):80            # can't fit81            return None82        data = self.content[self.idx : self.idx + size]83        self.idx += size84        # now switch on id85        if ident == 0x30:86            # sequence87            return self.decode_sequence(data)88        elif ident == 2:89            # int90            return util.inflate_long(data)91        else:92            # 1: boolean (00 false, otherwise true)93            msg = "Unknown ber encoding type {:d} (robey is lazy)"94            raise BERException(msg.format(ident))95 96    @staticmethod97    def decode_sequence(data):98        out = []99        ber = BER(data)100        while True:101            x = ber.decode_next()102            if x is None:103                break104            out.append(x)105        return out106 107    def encode_tlv(self, ident, val):108        # no need to support ident > 31 here109        self.content += byte_chr(ident)110        if len(val) > 0x7F:111            lenstr = util.deflate_long(len(val))112            self.content += byte_chr(0x80 + len(lenstr)) + lenstr113        else:114            self.content += byte_chr(len(val))115        self.content += val116 117    def encode(self, x):118        if type(x) is bool:119            if x:120                self.encode_tlv(1, max_byte)121            else:122                self.encode_tlv(1, zero_byte)123        elif (type(x) is int) or (type(x) is int64):124            self.encode_tlv(2, util.deflate_long(x))125        elif type(x) is str:126            self.encode_tlv(4, x)127        elif (type(x) is list) or (type(x) is tuple):128            self.encode_tlv(0x30, self.encode_sequence(x))129        else:130            raise BERException(131                "Unknown type for encoding: {!r}".format(type(x))132            )133 134    @staticmethod135    def encode_sequence(data):136        ber = BER()137        for item in data:138            ber.encode(item)139        return ber.asbytes()140