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Revert "(experimental) force to use custom dns"

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This reverts commit 2a6a5e62d4.
This commit is contained in:
mac12m99
2019-04-28 18:11:11 +02:00
parent 2a6a5e62d4
commit 1747bc98db
100 changed files with 2 additions and 15717 deletions
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lib/dns/name.py
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# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
# Copyright (C) 2001-2017 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
"""DNS Names.
"""
from io import BytesIO
import struct
import sys
import copy
import encodings.idna
try:
import idna
have_idna_2008 = True
except ImportError:
have_idna_2008 = False
import dns.exception
import dns.wiredata
from ._compat import long, binary_type, text_type, unichr, maybe_decode
try:
maxint = sys.maxint # pylint: disable=sys-max-int
except AttributeError:
maxint = (1 << (8 * struct.calcsize("P"))) // 2 - 1
# fullcompare() result values
#: The compared names have no relationship to each other.
NAMERELN_NONE = 0
#: the first name is a superdomain of the second.
NAMERELN_SUPERDOMAIN = 1
#: The first name is a subdomain of the second.
NAMERELN_SUBDOMAIN = 2
#: The compared names are equal.
NAMERELN_EQUAL = 3
#: The compared names have a common ancestor.
NAMERELN_COMMONANCESTOR = 4
class EmptyLabel(dns.exception.SyntaxError):
"""A DNS label is empty."""
class BadEscape(dns.exception.SyntaxError):
"""An escaped code in a text format of DNS name is invalid."""
class BadPointer(dns.exception.FormError):
"""A DNS compression pointer points forward instead of backward."""
class BadLabelType(dns.exception.FormError):
"""The label type in DNS name wire format is unknown."""
class NeedAbsoluteNameOrOrigin(dns.exception.DNSException):
"""An attempt was made to convert a non-absolute name to
wire when there was also a non-absolute (or missing) origin."""
class NameTooLong(dns.exception.FormError):
"""A DNS name is > 255 octets long."""
class LabelTooLong(dns.exception.SyntaxError):
"""A DNS label is > 63 octets long."""
class AbsoluteConcatenation(dns.exception.DNSException):
"""An attempt was made to append anything other than the
empty name to an absolute DNS name."""
class NoParent(dns.exception.DNSException):
"""An attempt was made to get the parent of the root name
or the empty name."""
class NoIDNA2008(dns.exception.DNSException):
"""IDNA 2008 processing was requested but the idna module is not
available."""
class IDNAException(dns.exception.DNSException):
"""IDNA processing raised an exception."""
supp_kwargs = {'idna_exception'}
fmt = "IDNA processing exception: {idna_exception}"
class IDNACodec(object):
"""Abstract base class for IDNA encoder/decoders."""
def __init__(self):
pass
def encode(self, label):
raise NotImplementedError
def decode(self, label):
# We do not apply any IDNA policy on decode; we just
downcased = label.lower()
if downcased.startswith(b'xn--'):
try:
label = downcased[4:].decode('punycode')
except Exception as e:
raise IDNAException(idna_exception=e)
else:
label = maybe_decode(label)
return _escapify(label, True)
class IDNA2003Codec(IDNACodec):
"""IDNA 2003 encoder/decoder."""
def __init__(self, strict_decode=False):
"""Initialize the IDNA 2003 encoder/decoder.
*strict_decode* is a ``bool``. If `True`, then IDNA2003 checking
is done when decoding. This can cause failures if the name
was encoded with IDNA2008. The default is `False`.
"""
super(IDNA2003Codec, self).__init__()
self.strict_decode = strict_decode
def encode(self, label):
"""Encode *label*."""
if label == '':
return b''
try:
return encodings.idna.ToASCII(label)
except UnicodeError:
raise LabelTooLong
def decode(self, label):
"""Decode *label*."""
if not self.strict_decode:
return super(IDNA2003Codec, self).decode(label)
if label == b'':
return u''
try:
return _escapify(encodings.idna.ToUnicode(label), True)
except Exception as e:
raise IDNAException(idna_exception=e)
class IDNA2008Codec(IDNACodec):
"""IDNA 2008 encoder/decoder.
*uts_46* is a ``bool``. If True, apply Unicode IDNA
compatibility processing as described in Unicode Technical
Standard #46 (http://unicode.org/reports/tr46/).
If False, do not apply the mapping. The default is False.
*transitional* is a ``bool``: If True, use the
"transitional" mode described in Unicode Technical Standard
#46. The default is False.
*allow_pure_ascii* is a ``bool``. If True, then a label which
consists of only ASCII characters is allowed. This is less
strict than regular IDNA 2008, but is also necessary for mixed
names, e.g. a name with starting with "_sip._tcp." and ending
in an IDN suffix which would otherwise be disallowed. The
default is False.
*strict_decode* is a ``bool``: If True, then IDNA2008 checking
is done when decoding. This can cause failures if the name
was encoded with IDNA2003. The default is False.
"""
def __init__(self, uts_46=False, transitional=False,
allow_pure_ascii=False, strict_decode=False):
"""Initialize the IDNA 2008 encoder/decoder."""
super(IDNA2008Codec, self).__init__()
self.uts_46 = uts_46
self.transitional = transitional
self.allow_pure_ascii = allow_pure_ascii
self.strict_decode = strict_decode
def is_all_ascii(self, label):
for c in label:
if ord(c) > 0x7f:
return False
return True
def encode(self, label):
if label == '':
return b''
if self.allow_pure_ascii and self.is_all_ascii(label):
return label.encode('ascii')
if not have_idna_2008:
raise NoIDNA2008
try:
if self.uts_46:
label = idna.uts46_remap(label, False, self.transitional)
return idna.alabel(label)
except idna.IDNAError as e:
raise IDNAException(idna_exception=e)
def decode(self, label):
if not self.strict_decode:
return super(IDNA2008Codec, self).decode(label)
if label == b'':
return u''
if not have_idna_2008:
raise NoIDNA2008
try:
if self.uts_46:
label = idna.uts46_remap(label, False, False)
return _escapify(idna.ulabel(label), True)
except idna.IDNAError as e:
raise IDNAException(idna_exception=e)
_escaped = bytearray(b'"().;\\@$')
IDNA_2003_Practical = IDNA2003Codec(False)
IDNA_2003_Strict = IDNA2003Codec(True)
IDNA_2003 = IDNA_2003_Practical
IDNA_2008_Practical = IDNA2008Codec(True, False, True, False)
IDNA_2008_UTS_46 = IDNA2008Codec(True, False, False, False)
IDNA_2008_Strict = IDNA2008Codec(False, False, False, True)
IDNA_2008_Transitional = IDNA2008Codec(True, True, False, False)
IDNA_2008 = IDNA_2008_Practical
def _escapify(label, unicode_mode=False):
"""Escape the characters in label which need it.
@param unicode_mode: escapify only special and whitespace (<= 0x20)
characters
@returns: the escaped string
@rtype: string"""
if not unicode_mode:
text = ''
if isinstance(label, text_type):
label = label.encode()
for c in bytearray(label):
if c in _escaped:
text += '\\' + chr(c)
elif c > 0x20 and c < 0x7F:
text += chr(c)
else:
text += '\\%03d' % c
return text.encode()
text = u''
if isinstance(label, binary_type):
label = label.decode()
for c in label:
if c > u'\x20' and c < u'\x7f':
text += c
else:
if c >= u'\x7f':
text += c
else:
text += u'\\%03d' % ord(c)
return text
def _validate_labels(labels):
"""Check for empty labels in the middle of a label sequence,
labels that are too long, and for too many labels.
Raises ``dns.name.NameTooLong`` if the name as a whole is too long.
Raises ``dns.name.EmptyLabel`` if a label is empty (i.e. the root
label) and appears in a position other than the end of the label
sequence
"""
l = len(labels)
total = 0
i = -1
j = 0
for label in labels:
ll = len(label)
total += ll + 1
if ll > 63:
raise LabelTooLong
if i < 0 and label == b'':
i = j
j += 1
if total > 255:
raise NameTooLong
if i >= 0 and i != l - 1:
raise EmptyLabel
def _maybe_convert_to_binary(label):
"""If label is ``text``, convert it to ``binary``. If it is already
``binary`` just return it.
"""
if isinstance(label, binary_type):
return label
if isinstance(label, text_type):
return label.encode()
raise ValueError
class Name(object):
"""A DNS name.
The dns.name.Name class represents a DNS name as a tuple of
labels. Each label is a `binary` in DNS wire format. Instances
of the class are immutable.
"""
__slots__ = ['labels']
def __init__(self, labels):
"""*labels* is any iterable whose values are ``text`` or ``binary``.
"""
labels = [_maybe_convert_to_binary(x) for x in labels]
super(Name, self).__setattr__('labels', tuple(labels))
_validate_labels(self.labels)
def __setattr__(self, name, value):
# Names are immutable
raise TypeError("object doesn't support attribute assignment")
def __copy__(self):
return Name(self.labels)
def __deepcopy__(self, memo):
return Name(copy.deepcopy(self.labels, memo))
def __getstate__(self):
# Names can be pickled
return {'labels': self.labels}
def __setstate__(self, state):
super(Name, self).__setattr__('labels', state['labels'])
_validate_labels(self.labels)
def is_absolute(self):
"""Is the most significant label of this name the root label?
Returns a ``bool``.
"""
return len(self.labels) > 0 and self.labels[-1] == b''
def is_wild(self):
"""Is this name wild? (I.e. Is the least significant label '*'?)
Returns a ``bool``.
"""
return len(self.labels) > 0 and self.labels[0] == b'*'
def __hash__(self):
"""Return a case-insensitive hash of the name.
Returns an ``int``.
"""
h = long(0)
for label in self.labels:
for c in bytearray(label.lower()):
h += (h << 3) + c
return int(h % maxint)
def fullcompare(self, other):
"""Compare two names, returning a 3-tuple
``(relation, order, nlabels)``.
*relation* describes the relation ship between the names,
and is one of: ``dns.name.NAMERELN_NONE``,
``dns.name.NAMERELN_SUPERDOMAIN``, ``dns.name.NAMERELN_SUBDOMAIN``,
``dns.name.NAMERELN_EQUAL``, or ``dns.name.NAMERELN_COMMONANCESTOR``.
*order* is < 0 if *self* < *other*, > 0 if *self* > *other*, and ==
0 if *self* == *other*. A relative name is always less than an
absolute name. If both names have the same relativity, then
the DNSSEC order relation is used to order them.
*nlabels* is the number of significant labels that the two names
have in common.
Here are some examples. Names ending in "." are absolute names,
those not ending in "." are relative names.
============= ============= =========== ===== =======
self other relation order nlabels
============= ============= =========== ===== =======
www.example. www.example. equal 0 3
www.example. example. subdomain > 0 2
example. www.example. superdomain < 0 2
example1.com. example2.com. common anc. < 0 2
example1 example2. none < 0 0
example1. example2 none > 0 0
============= ============= =========== ===== =======
"""
sabs = self.is_absolute()
oabs = other.is_absolute()
if sabs != oabs:
if sabs:
return (NAMERELN_NONE, 1, 0)
else:
return (NAMERELN_NONE, -1, 0)
l1 = len(self.labels)
l2 = len(other.labels)
ldiff = l1 - l2
if ldiff < 0:
l = l1
else:
l = l2
order = 0
nlabels = 0
namereln = NAMERELN_NONE
while l > 0:
l -= 1
l1 -= 1
l2 -= 1
label1 = self.labels[l1].lower()
label2 = other.labels[l2].lower()
if label1 < label2:
order = -1
if nlabels > 0:
namereln = NAMERELN_COMMONANCESTOR
return (namereln, order, nlabels)
elif label1 > label2:
order = 1
if nlabels > 0:
namereln = NAMERELN_COMMONANCESTOR
return (namereln, order, nlabels)
nlabels += 1
order = ldiff
if ldiff < 0:
namereln = NAMERELN_SUPERDOMAIN
elif ldiff > 0:
namereln = NAMERELN_SUBDOMAIN
else:
namereln = NAMERELN_EQUAL
return (namereln, order, nlabels)
def is_subdomain(self, other):
"""Is self a subdomain of other?
Note that the notion of subdomain includes equality, e.g.
"dnpython.org" is a subdomain of itself.
Returns a ``bool``.
"""
(nr, o, nl) = self.fullcompare(other)
if nr == NAMERELN_SUBDOMAIN or nr == NAMERELN_EQUAL:
return True
return False
def is_superdomain(self, other):
"""Is self a superdomain of other?
Note that the notion of superdomain includes equality, e.g.
"dnpython.org" is a superdomain of itself.
Returns a ``bool``.
"""
(nr, o, nl) = self.fullcompare(other)
if nr == NAMERELN_SUPERDOMAIN or nr == NAMERELN_EQUAL:
return True
return False
def canonicalize(self):
"""Return a name which is equal to the current name, but is in
DNSSEC canonical form.
"""
return Name([x.lower() for x in self.labels])
def __eq__(self, other):
if isinstance(other, Name):
return self.fullcompare(other)[1] == 0
else:
return False
def __ne__(self, other):
if isinstance(other, Name):
return self.fullcompare(other)[1] != 0
else:
return True
def __lt__(self, other):
if isinstance(other, Name):
return self.fullcompare(other)[1] < 0
else:
return NotImplemented
def __le__(self, other):
if isinstance(other, Name):
return self.fullcompare(other)[1] <= 0
else:
return NotImplemented
def __ge__(self, other):
if isinstance(other, Name):
return self.fullcompare(other)[1] >= 0
else:
return NotImplemented
def __gt__(self, other):
if isinstance(other, Name):
return self.fullcompare(other)[1] > 0
else:
return NotImplemented
def __repr__(self):
return '<DNS name ' + self.__str__() + '>'
def __str__(self):
return self.to_text(False)
def to_text(self, omit_final_dot=False):
"""Convert name to DNS text format.
*omit_final_dot* is a ``bool``. If True, don't emit the final
dot (denoting the root label) for absolute names. The default
is False.
Returns a ``text``.
"""
if len(self.labels) == 0:
return maybe_decode(b'@')
if len(self.labels) == 1 and self.labels[0] == b'':
return maybe_decode(b'.')
if omit_final_dot and self.is_absolute():
l = self.labels[:-1]
else:
l = self.labels
s = b'.'.join(map(_escapify, l))
return maybe_decode(s)
def to_unicode(self, omit_final_dot=False, idna_codec=None):
"""Convert name to Unicode text format.
IDN ACE labels are converted to Unicode.
*omit_final_dot* is a ``bool``. If True, don't emit the final
dot (denoting the root label) for absolute names. The default
is False.
*idna_codec* specifies the IDNA encoder/decoder. If None, the
dns.name.IDNA_2003_Practical encoder/decoder is used.
The IDNA_2003_Practical decoder does
not impose any policy, it just decodes punycode, so if you
don't want checking for compliance, you can use this decoder
for IDNA2008 as well.
Returns a ``text``.
"""
if len(self.labels) == 0:
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. All names in wire format are absolute. If the name
is a relative name, then an origin must be supplied.
*origin* is a ``dns.name.Name`` or ``None``. If the name is
relative and origin is not ``None``, then origin will be appended
to the name.
Raises ``dns.name.NeedAbsoluteNameOrOrigin`` if the name is
relative and no origin was provided.
Returns a ``binary``.
"""
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.
*file* is the file where the name is emitted (typically a
BytesIO file). If ``None`` (the default), a ``binary``
containing the wire name will be returned.
*compress*, a ``dict``, is the compression table to use. If
``None`` (the default), names will not be compressed.
*origin* is a ``dns.name.Name`` or ``None``. If the name is
relative and origin is not ``None``, then *origin* will be appended
to it.
Raises ``dns.name.NeedAbsoluteNameOrOrigin`` if the name is
relative and no origin was provided.
Returns a ``binary`` or ``None``.
"""
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).
Returns an ``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 names at the specified depth.
*depth* is an ``int`` specifying the number of labels in the suffix
Raises ``ValueError`` if *depth* was not >= 0 and <= the length of the
name.
Returns the tuple ``(prefix, suffix)``.
"""
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.
Raises ``dns.name.AbsoluteConcatenation`` if the name is
absolute and *other* is not the empty name.
Returns a ``dns.name.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 the name is a subdomain of *origin*, return a new name which is
the name relative to origin. Otherwise return the name.
For example, relativizing ``www.dnspython.org.`` to origin
``dnspython.org.`` returns the name ``www``. Relativizing ``example.``
to origin ``dnspython.org.`` returns ``example.``.
Returns a ``dns.name.Name``.
"""
if origin is not None and self.is_subdomain(origin):
return Name(self[: -len(origin)])
else:
return self
def derelativize(self, origin):
"""If the name is a relative name, return a new name which is the
concatenation of the name and origin. Otherwise return the name.
For example, derelativizing ``www`` to origin ``dnspython.org.``
returns the name ``www.dnspython.org.``. Derelativizing ``example.``
to origin ``dnspython.org.`` returns ``example.``.
Returns a ``dns.name.Name``.
"""
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 the name is returned.
Otherwise, if *relativize* is ``True`` the name is
relativized, and if *relativize* is ``False`` the name is
derelativized.
Returns a ``dns.name.Name``.
"""
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.
For example, the parent of ``www.dnspython.org.`` is ``dnspython.org``.
Raises ``dns.name.NoParent`` if the name is either the root name or the
empty name, and thus has no parent.
Returns a ``dns.name.Name``.
"""
if self == root or self == empty:
raise NoParent
return Name(self.labels[1:])
#: The root name, '.'
root = Name([b''])
#: The empty name.
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 according to rules specified by
the IDNA codec.
*text*, a ``text``, is the text to convert into a name.
*origin*, a ``dns.name.Name``, specifies the origin to
append to non-absolute names. The default is the root name.
*idna_codec*, a ``dns.name.IDNACodec``, specifies the IDNA
encoder/decoder. If ``None``, the default IDNA 2003 encoder/decoder
is used.
Returns a ``dns.name.Name``.
"""
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.
*text*, a ``text``, is the text to convert into a name.
*origin*, a ``dns.name.Name``, specifies the origin to
append to non-absolute names. The default is the root name.
*idna_codec*, a ``dns.name.IDNACodec``, specifies the IDNA
encoder/decoder. If ``None``, the default IDNA 2003 encoder/decoder
is used.
Returns a ``dns.name.Name``.
"""
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.
*message* is a ``binary`` containing an entire DNS message in DNS
wire form.
*current*, an ``int``, is the offset of the beginning of the name
from the start of the message
Raises ``dns.name.BadPointer`` if a compression pointer did not
point backwards in the message.
Raises ``dns.name.BadLabelType`` if an invalid label type was encountered.
Returns a ``(dns.name.Name, int)`` tuple consisting of the name
that was read and the number of bytes of the wire format message
which were consumed reading it.
"""
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)