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925 lines
29 KiB
925 lines
29 KiB
# Copyright (C) 2001-2007, 2009-2011 Nominum, Inc.
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#
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# Permission to use, copy, modify, and distribute this software and its
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# documentation for any purpose with or without fee is hereby granted,
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# provided that the above copyright notice and this permission notice
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# appear in all copies.
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#
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# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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"""DNS Names.
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@var root: The DNS root name.
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@type root: dns.name.Name object
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@var empty: The empty DNS name.
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@type empty: dns.name.Name object
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"""
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from io import BytesIO
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import struct
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import sys
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import copy
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import encodings.idna
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try:
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import idna
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have_idna_2008 = True
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except ImportError:
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have_idna_2008 = False
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import dns.exception
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import dns.wiredata
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from ._compat import long, binary_type, text_type, unichr, maybe_decode
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try:
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maxint = sys.maxint
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except AttributeError:
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maxint = (1 << (8 * struct.calcsize("P"))) // 2 - 1
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NAMERELN_NONE = 0
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NAMERELN_SUPERDOMAIN = 1
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NAMERELN_SUBDOMAIN = 2
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NAMERELN_EQUAL = 3
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NAMERELN_COMMONANCESTOR = 4
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class EmptyLabel(dns.exception.SyntaxError):
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"""A DNS label is empty."""
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class BadEscape(dns.exception.SyntaxError):
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"""An escaped code in a text format of DNS name is invalid."""
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class BadPointer(dns.exception.FormError):
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"""A DNS compression pointer points forward instead of backward."""
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class BadLabelType(dns.exception.FormError):
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"""The label type in DNS name wire format is unknown."""
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class NeedAbsoluteNameOrOrigin(dns.exception.DNSException):
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"""An attempt was made to convert a non-absolute name to
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wire when there was also a non-absolute (or missing) origin."""
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class NameTooLong(dns.exception.FormError):
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"""A DNS name is > 255 octets long."""
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class LabelTooLong(dns.exception.SyntaxError):
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"""A DNS label is > 63 octets long."""
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class AbsoluteConcatenation(dns.exception.DNSException):
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"""An attempt was made to append anything other than the
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empty name to an absolute DNS name."""
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class NoParent(dns.exception.DNSException):
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"""An attempt was made to get the parent of the root name
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or the empty name."""
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class NoIDNA2008(dns.exception.DNSException):
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"""IDNA 2008 processing was requested but the idna module is not
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available."""
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class IDNAException(dns.exception.DNSException):
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"""IDNA processing raised an exception."""
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supp_kwargs = set(['idna_exception'])
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fmt = "IDNA processing exception: {idna_exception}"
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class IDNACodec(object):
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"""Abstract base class for IDNA encoder/decoders."""
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def __init__(self):
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pass
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def encode(self, label):
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raise NotImplementedError
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def decode(self, label):
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# We do not apply any IDNA policy on decode; we just
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downcased = label.lower()
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if downcased.startswith(b'xn--'):
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try:
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label = downcased[4:].decode('punycode')
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except Exception as e:
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raise IDNAException(idna_exception=e)
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else:
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label = maybe_decode(label)
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return _escapify(label, True)
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class IDNA2003Codec(IDNACodec):
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"""IDNA 2003 encoder/decoder."""
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def __init__(self, strict_decode=False):
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"""Initialize the IDNA 2003 encoder/decoder.
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@param strict_decode: If True, then IDNA2003 checking is done when
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decoding. This can cause failures if the name was encoded with
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IDNA2008. The default is False.
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@type strict_decode: bool
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"""
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super(IDNA2003Codec, self).__init__()
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self.strict_decode = strict_decode
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def encode(self, label):
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if label == '':
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return b''
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try:
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return encodings.idna.ToASCII(label)
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except UnicodeError:
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raise LabelTooLong
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def decode(self, label):
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if not self.strict_decode:
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return super(IDNA2003Codec, self).decode(label)
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if label == b'':
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return u''
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try:
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return _escapify(encodings.idna.ToUnicode(label), True)
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except Exception as e:
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raise IDNAException(idna_exception=e)
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class IDNA2008Codec(IDNACodec):
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"""IDNA 2008 encoder/decoder."""
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def __init__(self, uts_46=False, transitional=False,
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allow_pure_ascii=False, strict_decode=False):
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"""Initialize the IDNA 2008 encoder/decoder.
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@param uts_46: If True, apply Unicode IDNA compatibility processing
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as described in Unicode Technical Standard #46
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(U{http://unicode.org/reports/tr46/}). This parameter is only
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meaningful if IDNA 2008 is in use. If False, do not apply
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the mapping. The default is False
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@type uts_46: bool
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@param transitional: If True, use the "transitional" mode described
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in Unicode Technical Standard #46. This parameter is only
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meaningful if IDNA 2008 is in use. The default is False.
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@type transitional: bool
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@param allow_pure_ascii: If True, then a label which
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consists of only ASCII characters is allowed. This is less strict
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than regular IDNA 2008, but is also necessary for mixed names,
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e.g. a name with starting with "_sip._tcp." and ending in an IDN
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suffixm which would otherwise be disallowed. The default is False
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@type allow_pure_ascii: bool
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@param strict_decode: If True, then IDNA2008 checking is done when
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decoding. This can cause failures if the name was encoded with
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IDNA2003. The default is False.
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@type strict_decode: bool
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"""
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super(IDNA2008Codec, self).__init__()
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self.uts_46 = uts_46
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self.transitional = transitional
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self.allow_pure_ascii = allow_pure_ascii
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self.strict_decode = strict_decode
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def is_all_ascii(self, label):
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for c in label:
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if ord(c) > 0x7f:
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return False
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return True
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def encode(self, label):
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if label == '':
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return b''
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if self.allow_pure_ascii and self.is_all_ascii(label):
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return label.encode('ascii')
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if not have_idna_2008:
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raise NoIDNA2008
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try:
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if self.uts_46:
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label = idna.uts46_remap(label, False, self.transitional)
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return idna.alabel(label)
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except idna.IDNAError as e:
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raise IDNAException(idna_exception=e)
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def decode(self, label):
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if not self.strict_decode:
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return super(IDNA2008Codec, self).decode(label)
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if label == b'':
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return u''
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if not have_idna_2008:
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raise NoIDNA2008
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try:
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if self.uts_46:
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label = idna.uts46_remap(label, False, False)
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return _escapify(idna.ulabel(label), True)
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except idna.IDNAError as e:
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raise IDNAException(idna_exception=e)
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_escaped = bytearray(b'"().;\\@$')
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IDNA_2003_Practical = IDNA2003Codec(False)
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IDNA_2003_Strict = IDNA2003Codec(True)
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IDNA_2003 = IDNA_2003_Practical
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IDNA_2008_Practical = IDNA2008Codec(True, False, True, False)
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IDNA_2008_UTS_46 = IDNA2008Codec(True, False, False, False)
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IDNA_2008_Strict = IDNA2008Codec(False, False, False, True)
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IDNA_2008_Transitional = IDNA2008Codec(True, True, False, False)
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IDNA_2008 = IDNA_2008_Practical
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def _escapify(label, unicode_mode=False):
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"""Escape the characters in label which need it.
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@param unicode_mode: escapify only special and whitespace (<= 0x20)
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characters
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@returns: the escaped string
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@rtype: string"""
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if not unicode_mode:
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text = ''
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if isinstance(label, text_type):
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label = label.encode()
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for c in bytearray(label):
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if c in _escaped:
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text += '\\' + chr(c)
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elif c > 0x20 and c < 0x7F:
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text += chr(c)
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else:
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text += '\\%03d' % c
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return text.encode()
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text = u''
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if isinstance(label, binary_type):
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label = label.decode()
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for c in label:
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if c > u'\x20' and c < u'\x7f':
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text += c
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else:
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if c >= u'\x7f':
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text += c
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else:
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text += u'\\%03d' % ord(c)
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return text
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def _validate_labels(labels):
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"""Check for empty labels in the middle of a label sequence,
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labels that are too long, and for too many labels.
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@raises NameTooLong: the name as a whole is too long
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@raises EmptyLabel: a label is empty (i.e. the root label) and appears
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in a position other than the end of the label sequence"""
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l = len(labels)
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total = 0
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i = -1
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j = 0
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for label in labels:
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ll = len(label)
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total += ll + 1
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if ll > 63:
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raise LabelTooLong
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if i < 0 and label == b'':
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i = j
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j += 1
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if total > 255:
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raise NameTooLong
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if i >= 0 and i != l - 1:
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raise EmptyLabel
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def _ensure_bytes(label):
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if isinstance(label, binary_type):
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return label
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if isinstance(label, text_type):
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return label.encode()
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raise ValueError
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class Name(object):
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"""A DNS name.
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The dns.name.Name class represents a DNS name as a tuple of labels.
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Instances of the class are immutable.
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@ivar labels: The tuple of labels in the name. Each label is a string of
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up to 63 octets."""
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__slots__ = ['labels']
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def __init__(self, labels):
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"""Initialize a domain name from a list of labels.
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@param labels: the labels
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@type labels: any iterable whose values are strings
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"""
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labels = [_ensure_bytes(x) for x in labels]
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super(Name, self).__setattr__('labels', tuple(labels))
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_validate_labels(self.labels)
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def __setattr__(self, name, value):
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raise TypeError("object doesn't support attribute assignment")
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def __copy__(self):
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return Name(self.labels)
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def __deepcopy__(self, memo):
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return Name(copy.deepcopy(self.labels, memo))
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def __getstate__(self):
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return {'labels': self.labels}
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def __setstate__(self, state):
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super(Name, self).__setattr__('labels', state['labels'])
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_validate_labels(self.labels)
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def is_absolute(self):
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"""Is the most significant label of this name the root label?
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@rtype: bool
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"""
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return len(self.labels) > 0 and self.labels[-1] == b''
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def is_wild(self):
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"""Is this name wild? (I.e. Is the least significant label '*'?)
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@rtype: bool
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"""
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return len(self.labels) > 0 and self.labels[0] == b'*'
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def __hash__(self):
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"""Return a case-insensitive hash of the name.
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@rtype: int
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"""
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h = long(0)
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for label in self.labels:
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for c in bytearray(label.lower()):
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h += (h << 3) + c
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return int(h % maxint)
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def fullcompare(self, other):
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"""Compare two names, returning a 3-tuple (relation, order, nlabels).
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I{relation} describes the relation ship between the names,
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and is one of: dns.name.NAMERELN_NONE,
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dns.name.NAMERELN_SUPERDOMAIN, dns.name.NAMERELN_SUBDOMAIN,
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dns.name.NAMERELN_EQUAL, or dns.name.NAMERELN_COMMONANCESTOR
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I{order} is < 0 if self < other, > 0 if self > other, and ==
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0 if self == other. A relative name is always less than an
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absolute name. If both names have the same relativity, then
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the DNSSEC order relation is used to order them.
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I{nlabels} is the number of significant labels that the two names
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have in common.
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"""
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sabs = self.is_absolute()
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oabs = other.is_absolute()
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if sabs != oabs:
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if sabs:
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return (NAMERELN_NONE, 1, 0)
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else:
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return (NAMERELN_NONE, -1, 0)
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l1 = len(self.labels)
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l2 = len(other.labels)
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ldiff = l1 - l2
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if ldiff < 0:
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l = l1
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else:
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l = l2
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order = 0
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nlabels = 0
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namereln = NAMERELN_NONE
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while l > 0:
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l -= 1
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l1 -= 1
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l2 -= 1
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label1 = self.labels[l1].lower()
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label2 = other.labels[l2].lower()
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if label1 < label2:
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order = -1
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if nlabels > 0:
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namereln = NAMERELN_COMMONANCESTOR
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return (namereln, order, nlabels)
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elif label1 > label2:
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order = 1
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if nlabels > 0:
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namereln = NAMERELN_COMMONANCESTOR
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return (namereln, order, nlabels)
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nlabels += 1
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order = ldiff
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if ldiff < 0:
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namereln = NAMERELN_SUPERDOMAIN
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elif ldiff > 0:
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namereln = NAMERELN_SUBDOMAIN
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else:
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namereln = NAMERELN_EQUAL
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return (namereln, order, nlabels)
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def is_subdomain(self, other):
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"""Is self a subdomain of other?
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The notion of subdomain includes equality.
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@rtype: bool
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"""
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(nr, o, nl) = self.fullcompare(other)
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if nr == NAMERELN_SUBDOMAIN or nr == NAMERELN_EQUAL:
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return True
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return False
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def is_superdomain(self, other):
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"""Is self a superdomain of other?
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The notion of subdomain includes equality.
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@rtype: bool
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"""
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(nr, o, nl) = self.fullcompare(other)
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if nr == NAMERELN_SUPERDOMAIN or nr == NAMERELN_EQUAL:
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return True
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return False
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def canonicalize(self):
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"""Return a name which is equal to the current name, but is in
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DNSSEC canonical form.
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@rtype: dns.name.Name object
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"""
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return Name([x.lower() for x in self.labels])
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def __eq__(self, other):
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if isinstance(other, Name):
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return self.fullcompare(other)[1] == 0
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else:
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return False
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def __ne__(self, other):
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if isinstance(other, Name):
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return self.fullcompare(other)[1] != 0
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else:
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return True
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def __lt__(self, other):
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if isinstance(other, Name):
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return self.fullcompare(other)[1] < 0
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else:
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return NotImplemented
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def __le__(self, other):
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if isinstance(other, Name):
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return self.fullcompare(other)[1] <= 0
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else:
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return NotImplemented
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def __ge__(self, other):
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if isinstance(other, Name):
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return self.fullcompare(other)[1] >= 0
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else:
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return NotImplemented
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def __gt__(self, other):
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if isinstance(other, Name):
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return self.fullcompare(other)[1] > 0
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else:
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return NotImplemented
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def __repr__(self):
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return '<DNS name ' + self.__str__() + '>'
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def __str__(self):
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return self.to_text(False)
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def to_text(self, omit_final_dot=False):
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"""Convert name to text format.
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@param omit_final_dot: If True, don't emit the final dot (denoting the
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root label) for absolute names. The default is False.
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@rtype: string
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"""
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if len(self.labels) == 0:
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return maybe_decode(b'@')
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if len(self.labels) == 1 and self.labels[0] == b'':
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return maybe_decode(b'.')
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if omit_final_dot and self.is_absolute():
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l = self.labels[:-1]
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else:
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l = self.labels
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s = b'.'.join(map(_escapify, l))
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return maybe_decode(s)
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def to_unicode(self, omit_final_dot=False, idna_codec=None):
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"""Convert name to Unicode text format.
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IDN ACE labels are converted to Unicode.
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@param omit_final_dot: If True, don't emit the final dot (denoting the
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root label) for absolute names. The default is False.
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@type omit_final_dot: bool
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@param idna_codec: IDNA encoder/decoder. If None, the
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IDNA_2003_Practical encoder/decoder is used. The IDNA_2003_Practical
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decoder does not impose any policy, it just decodes punycode, so if
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you don't want checking for compliance, you can use this decoder for
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IDNA2008 as well.
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@type idna_codec: dns.name.IDNA
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@rtype: string
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"""
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if len(self.labels) == 0:
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return u'@'
|
|
if len(self.labels) == 1 and self.labels[0] == b'':
|
|
return u'.'
|
|
if omit_final_dot and self.is_absolute():
|
|
l = self.labels[:-1]
|
|
else:
|
|
l = self.labels
|
|
if idna_codec is None:
|
|
idna_codec = IDNA_2003_Practical
|
|
return u'.'.join([idna_codec.decode(x) for x in l])
|
|
|
|
def to_digestable(self, origin=None):
|
|
"""Convert name to a format suitable for digesting in hashes.
|
|
|
|
The name is canonicalized and converted to uncompressed wire format.
|
|
|
|
@param origin: If the name is relative and origin is not None, then
|
|
origin will be appended to it.
|
|
@type origin: dns.name.Name object
|
|
@raises NeedAbsoluteNameOrOrigin: All names in wire format are
|
|
absolute. If self is a relative name, then an origin must be supplied;
|
|
if it is missing, then this exception is raised
|
|
@rtype: string
|
|
"""
|
|
|
|
if not self.is_absolute():
|
|
if origin is None or not origin.is_absolute():
|
|
raise NeedAbsoluteNameOrOrigin
|
|
labels = list(self.labels)
|
|
labels.extend(list(origin.labels))
|
|
else:
|
|
labels = self.labels
|
|
dlabels = [struct.pack('!B%ds' % len(x), len(x), x.lower())
|
|
for x in labels]
|
|
return b''.join(dlabels)
|
|
|
|
def to_wire(self, file=None, compress=None, origin=None):
|
|
"""Convert name to wire format, possibly compressing it.
|
|
|
|
@param file: the file where the name is emitted (typically
|
|
a BytesIO file). If None, a string containing the wire name
|
|
will be returned.
|
|
@type file: file or None
|
|
@param compress: The compression table. If None (the default) names
|
|
will not be compressed.
|
|
@type compress: dict
|
|
@param origin: If the name is relative and origin is not None, then
|
|
origin will be appended to it.
|
|
@type origin: dns.name.Name object
|
|
@raises NeedAbsoluteNameOrOrigin: All names in wire format are
|
|
absolute. If self is a relative name, then an origin must be supplied;
|
|
if it is missing, then this exception is raised
|
|
"""
|
|
|
|
if file is None:
|
|
file = BytesIO()
|
|
want_return = True
|
|
else:
|
|
want_return = False
|
|
|
|
if not self.is_absolute():
|
|
if origin is None or not origin.is_absolute():
|
|
raise NeedAbsoluteNameOrOrigin
|
|
labels = list(self.labels)
|
|
labels.extend(list(origin.labels))
|
|
else:
|
|
labels = self.labels
|
|
i = 0
|
|
for label in labels:
|
|
n = Name(labels[i:])
|
|
i += 1
|
|
if compress is not None:
|
|
pos = compress.get(n)
|
|
else:
|
|
pos = None
|
|
if pos is not None:
|
|
value = 0xc000 + pos
|
|
s = struct.pack('!H', value)
|
|
file.write(s)
|
|
break
|
|
else:
|
|
if compress is not None and len(n) > 1:
|
|
pos = file.tell()
|
|
if pos <= 0x3fff:
|
|
compress[n] = pos
|
|
l = len(label)
|
|
file.write(struct.pack('!B', l))
|
|
if l > 0:
|
|
file.write(label)
|
|
if want_return:
|
|
return file.getvalue()
|
|
|
|
def __len__(self):
|
|
"""The length of the name (in labels).
|
|
@rtype: int
|
|
"""
|
|
|
|
return len(self.labels)
|
|
|
|
def __getitem__(self, index):
|
|
return self.labels[index]
|
|
|
|
def __add__(self, other):
|
|
return self.concatenate(other)
|
|
|
|
def __sub__(self, other):
|
|
return self.relativize(other)
|
|
|
|
def split(self, depth):
|
|
"""Split a name into a prefix and suffix at depth.
|
|
|
|
@param depth: the number of labels in the suffix
|
|
@type depth: int
|
|
@raises ValueError: the depth was not >= 0 and <= the length of the
|
|
name.
|
|
@returns: the tuple (prefix, suffix)
|
|
@rtype: tuple
|
|
"""
|
|
|
|
l = len(self.labels)
|
|
if depth == 0:
|
|
return (self, dns.name.empty)
|
|
elif depth == l:
|
|
return (dns.name.empty, self)
|
|
elif depth < 0 or depth > l:
|
|
raise ValueError(
|
|
'depth must be >= 0 and <= the length of the name')
|
|
return (Name(self[: -depth]), Name(self[-depth:]))
|
|
|
|
def concatenate(self, other):
|
|
"""Return a new name which is the concatenation of self and other.
|
|
@rtype: dns.name.Name object
|
|
@raises AbsoluteConcatenation: self is absolute and other is
|
|
not the empty name
|
|
"""
|
|
|
|
if self.is_absolute() and len(other) > 0:
|
|
raise AbsoluteConcatenation
|
|
labels = list(self.labels)
|
|
labels.extend(list(other.labels))
|
|
return Name(labels)
|
|
|
|
def relativize(self, origin):
|
|
"""If self is a subdomain of origin, return a new name which is self
|
|
relative to origin. Otherwise return self.
|
|
@rtype: dns.name.Name object
|
|
"""
|
|
|
|
if origin is not None and self.is_subdomain(origin):
|
|
return Name(self[: -len(origin)])
|
|
else:
|
|
return self
|
|
|
|
def derelativize(self, origin):
|
|
"""If self is a relative name, return a new name which is the
|
|
concatenation of self and origin. Otherwise return self.
|
|
@rtype: dns.name.Name object
|
|
"""
|
|
|
|
if not self.is_absolute():
|
|
return self.concatenate(origin)
|
|
else:
|
|
return self
|
|
|
|
def choose_relativity(self, origin=None, relativize=True):
|
|
"""Return a name with the relativity desired by the caller. If
|
|
origin is None, then self is returned. Otherwise, if
|
|
relativize is true the name is relativized, and if relativize is
|
|
false the name is derelativized.
|
|
@rtype: dns.name.Name object
|
|
"""
|
|
|
|
if origin:
|
|
if relativize:
|
|
return self.relativize(origin)
|
|
else:
|
|
return self.derelativize(origin)
|
|
else:
|
|
return self
|
|
|
|
def parent(self):
|
|
"""Return the parent of the name.
|
|
@rtype: dns.name.Name object
|
|
@raises NoParent: the name is either the root name or the empty name,
|
|
and thus has no parent.
|
|
"""
|
|
if self == root or self == empty:
|
|
raise NoParent
|
|
return Name(self.labels[1:])
|
|
|
|
root = Name([b''])
|
|
empty = Name([])
|
|
|
|
|
|
def from_unicode(text, origin=root, idna_codec=None):
|
|
"""Convert unicode text into a Name object.
|
|
|
|
Labels are encoded in IDN ACE form.
|
|
|
|
@param text: The text to convert into a name.
|
|
@type text: Unicode string
|
|
@param origin: The origin to append to non-absolute names.
|
|
@type origin: dns.name.Name
|
|
@param idna_codec: IDNA encoder/decoder. If None, the default IDNA 2003
|
|
encoder/decoder is used.
|
|
@type idna_codec: dns.name.IDNA
|
|
@rtype: dns.name.Name object
|
|
"""
|
|
|
|
if not isinstance(text, text_type):
|
|
raise ValueError("input to from_unicode() must be a unicode string")
|
|
if not (origin is None or isinstance(origin, Name)):
|
|
raise ValueError("origin must be a Name or None")
|
|
labels = []
|
|
label = u''
|
|
escaping = False
|
|
edigits = 0
|
|
total = 0
|
|
if idna_codec is None:
|
|
idna_codec = IDNA_2003
|
|
if text == u'@':
|
|
text = u''
|
|
if text:
|
|
if text == u'.':
|
|
return Name([b'']) # no Unicode "u" on this constant!
|
|
for c in text:
|
|
if escaping:
|
|
if edigits == 0:
|
|
if c.isdigit():
|
|
total = int(c)
|
|
edigits += 1
|
|
else:
|
|
label += c
|
|
escaping = False
|
|
else:
|
|
if not c.isdigit():
|
|
raise BadEscape
|
|
total *= 10
|
|
total += int(c)
|
|
edigits += 1
|
|
if edigits == 3:
|
|
escaping = False
|
|
label += unichr(total)
|
|
elif c in [u'.', u'\u3002', u'\uff0e', u'\uff61']:
|
|
if len(label) == 0:
|
|
raise EmptyLabel
|
|
labels.append(idna_codec.encode(label))
|
|
label = u''
|
|
elif c == u'\\':
|
|
escaping = True
|
|
edigits = 0
|
|
total = 0
|
|
else:
|
|
label += c
|
|
if escaping:
|
|
raise BadEscape
|
|
if len(label) > 0:
|
|
labels.append(idna_codec.encode(label))
|
|
else:
|
|
labels.append(b'')
|
|
|
|
if (len(labels) == 0 or labels[-1] != b'') and origin is not None:
|
|
labels.extend(list(origin.labels))
|
|
return Name(labels)
|
|
|
|
|
|
def from_text(text, origin=root, idna_codec=None):
|
|
"""Convert text into a Name object.
|
|
|
|
@param text: The text to convert into a name.
|
|
@type text: string
|
|
@param origin: The origin to append to non-absolute names.
|
|
@type origin: dns.name.Name
|
|
@param idna_codec: IDNA encoder/decoder. If None, the default IDNA 2003
|
|
encoder/decoder is used.
|
|
@type idna_codec: dns.name.IDNA
|
|
@rtype: dns.name.Name object
|
|
"""
|
|
|
|
if isinstance(text, text_type):
|
|
return from_unicode(text, origin, idna_codec)
|
|
if not isinstance(text, binary_type):
|
|
raise ValueError("input to from_text() must be a string")
|
|
if not (origin is None or isinstance(origin, Name)):
|
|
raise ValueError("origin must be a Name or None")
|
|
labels = []
|
|
label = b''
|
|
escaping = False
|
|
edigits = 0
|
|
total = 0
|
|
if text == b'@':
|
|
text = b''
|
|
if text:
|
|
if text == b'.':
|
|
return Name([b''])
|
|
for c in bytearray(text):
|
|
byte_ = struct.pack('!B', c)
|
|
if escaping:
|
|
if edigits == 0:
|
|
if byte_.isdigit():
|
|
total = int(byte_)
|
|
edigits += 1
|
|
else:
|
|
label += byte_
|
|
escaping = False
|
|
else:
|
|
if not byte_.isdigit():
|
|
raise BadEscape
|
|
total *= 10
|
|
total += int(byte_)
|
|
edigits += 1
|
|
if edigits == 3:
|
|
escaping = False
|
|
label += struct.pack('!B', total)
|
|
elif byte_ == b'.':
|
|
if len(label) == 0:
|
|
raise EmptyLabel
|
|
labels.append(label)
|
|
label = b''
|
|
elif byte_ == b'\\':
|
|
escaping = True
|
|
edigits = 0
|
|
total = 0
|
|
else:
|
|
label += byte_
|
|
if escaping:
|
|
raise BadEscape
|
|
if len(label) > 0:
|
|
labels.append(label)
|
|
else:
|
|
labels.append(b'')
|
|
if (len(labels) == 0 or labels[-1] != b'') and origin is not None:
|
|
labels.extend(list(origin.labels))
|
|
return Name(labels)
|
|
|
|
|
|
def from_wire(message, current):
|
|
"""Convert possibly compressed wire format into a Name.
|
|
@param message: the entire DNS message
|
|
@type message: string
|
|
@param current: the offset of the beginning of the name from the start
|
|
of the message
|
|
@type current: int
|
|
@raises dns.name.BadPointer: a compression pointer did not point backwards
|
|
in the message
|
|
@raises dns.name.BadLabelType: an invalid label type was encountered.
|
|
@returns: a tuple consisting of the name that was read and the number
|
|
of bytes of the wire format message which were consumed reading it
|
|
@rtype: (dns.name.Name object, int) tuple
|
|
"""
|
|
|
|
if not isinstance(message, binary_type):
|
|
raise ValueError("input to from_wire() must be a byte string")
|
|
message = dns.wiredata.maybe_wrap(message)
|
|
labels = []
|
|
biggest_pointer = current
|
|
hops = 0
|
|
count = message[current]
|
|
current += 1
|
|
cused = 1
|
|
while count != 0:
|
|
if count < 64:
|
|
labels.append(message[current: current + count].unwrap())
|
|
current += count
|
|
if hops == 0:
|
|
cused += count
|
|
elif count >= 192:
|
|
current = (count & 0x3f) * 256 + message[current]
|
|
if hops == 0:
|
|
cused += 1
|
|
if current >= biggest_pointer:
|
|
raise BadPointer
|
|
biggest_pointer = current
|
|
hops += 1
|
|
else:
|
|
raise BadLabelType
|
|
count = message[current]
|
|
current += 1
|
|
if hops == 0:
|
|
cused += 1
|
|
labels.append('')
|
|
return (Name(labels), cused)
|