# 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.
"""
import copy
import encodings.idna # type: ignore
import functools
import struct
from typing import Any, Callable, Dict, Iterable, Optional, Tuple, Union
import dns._features
import dns.enum
import dns.exception
import dns.immutable
import dns.wire
if dns._features.have("idna"):
import idna # type: ignore
have_idna_2008 = True
else: # pragma: no cover
have_idna_2008 = False
CompressType = Dict["Name", int]
[docs]
class NameRelation(dns.enum.IntEnum):
"""Name relation result from fullcompare()."""
# This is an IntEnum for backwards compatibility in case anyone
# has hardwired the constants.
#: The compared names have no relationship to each other.
NONE = 0
#: the first name is a superdomain of the second.
SUPERDOMAIN = 1
#: The first name is a subdomain of the second.
SUBDOMAIN = 2
#: The compared names are equal.
EQUAL = 3
#: The compared names have a common ancestor.
COMMONANCESTOR = 4
@classmethod
def _maximum(cls):
return cls.COMMONANCESTOR # pragma: no cover
@classmethod
def _short_name(cls):
return cls.__name__ # pragma: no cover
# Backwards compatibility
NAMERELN_NONE = NameRelation.NONE
NAMERELN_SUPERDOMAIN = NameRelation.SUPERDOMAIN
NAMERELN_SUBDOMAIN = NameRelation.SUBDOMAIN
NAMERELN_EQUAL = NameRelation.EQUAL
NAMERELN_COMMONANCESTOR = NameRelation.COMMONANCESTOR
[docs]
class EmptyLabel(dns.exception.SyntaxError):
"""A DNS label is empty."""
[docs]
class BadEscape(dns.exception.SyntaxError):
"""An escaped code in a text format of DNS name is invalid."""
[docs]
class BadPointer(dns.exception.FormError):
"""A DNS compression pointer points forward instead of backward."""
[docs]
class BadLabelType(dns.exception.FormError):
"""The label type in DNS name wire format is unknown."""
[docs]
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."""
[docs]
class AbsoluteConcatenation(dns.exception.DNSException):
"""An attempt was made to append anything other than the
empty name to an absolute DNS name."""
[docs]
class NoParent(dns.exception.DNSException):
"""An attempt was made to get the parent of the root name
or the empty name."""
[docs]
class NoIDNA2008(dns.exception.DNSException):
"""IDNA 2008 processing was requested but the idna module is not
available."""
[docs]
class IDNAException(dns.exception.DNSException):
"""IDNA processing raised an exception."""
supp_kwargs = {"idna_exception"}
fmt = "IDNA processing exception: {idna_exception}"
# We do this as otherwise mypy complains about unexpected keyword argument
# idna_exception
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
class NeedSubdomainOfOrigin(dns.exception.DNSException):
"""An absolute name was provided that is not a subdomain of the specified origin."""
_escaped = b'"().;\\@$'
_escaped_text = '"().;\\@$'
def _escapify(label: Union[bytes, str]) -> str:
"""Escape the characters in label which need it.
@returns: the escaped string
@rtype: string"""
if isinstance(label, bytes):
# Ordinary DNS label mode. Escape special characters and values
# < 0x20 or > 0x7f.
text = ""
for c in label:
if c in _escaped:
text += "\\" + chr(c)
elif c > 0x20 and c < 0x7F:
text += chr(c)
else:
text += "\\%03d" % c
return text
# Unicode label mode. Escape only special characters and values < 0x20
text = ""
for uc in label:
if uc in _escaped_text:
text += "\\" + uc
elif uc <= "\x20":
text += "\\%03d" % ord(uc)
else:
text += uc
return text
[docs]
class IDNACodec:
"""Abstract base class for IDNA encoder/decoders."""
def __init__(self):
pass
def is_idna(self, label: bytes) -> bool:
return label.lower().startswith(b"xn--")
def encode(self, label: str) -> bytes:
raise NotImplementedError # pragma: no cover
def decode(self, label: bytes) -> str:
# We do not apply any IDNA policy on decode.
if self.is_idna(label):
try:
slabel = label[4:].decode("punycode")
return _escapify(slabel)
except Exception as e:
raise IDNAException(idna_exception=e)
else:
return _escapify(label)
[docs]
class IDNA2003Codec(IDNACodec):
"""IDNA 2003 encoder/decoder."""
def __init__(self, strict_decode: bool = 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().__init__()
self.strict_decode = strict_decode
[docs]
def encode(self, label: str) -> bytes:
"""Encode *label*."""
if label == "":
return b""
try:
return encodings.idna.ToASCII(label)
except UnicodeError:
raise LabelTooLong
[docs]
def decode(self, label: bytes) -> str:
"""Decode *label*."""
if not self.strict_decode:
return super().decode(label)
if label == b"":
return ""
try:
return _escapify(encodings.idna.ToUnicode(label))
except Exception as e:
raise IDNAException(idna_exception=e)
[docs]
class IDNA2008Codec(IDNACodec):
"""IDNA 2008 encoder/decoder."""
def __init__(
self,
uts_46: bool = False,
transitional: bool = False,
allow_pure_ascii: bool = False,
strict_decode: bool = False,
):
"""Initialize the IDNA 2008 encoder/decoder.
*uts_46* is a ``bool``. If True, apply Unicode IDNA
compatibility processing as described in Unicode Technical
Standard #46 (https://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.
"""
super().__init__()
self.uts_46 = uts_46
self.transitional = transitional
self.allow_pure_ascii = allow_pure_ascii
self.strict_decode = strict_decode
def encode(self, label: str) -> bytes:
if label == "":
return b""
if self.allow_pure_ascii and is_all_ascii(label):
encoded = label.encode("ascii")
if len(encoded) > 63:
raise LabelTooLong
return encoded
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:
if e.args[0] == "Label too long":
raise LabelTooLong
else:
raise IDNAException(idna_exception=e)
def decode(self, label: bytes) -> str:
if not self.strict_decode:
return super().decode(label)
if label == b"":
return ""
if not have_idna_2008:
raise NoIDNA2008
try:
ulabel = idna.ulabel(label)
if self.uts_46:
ulabel = idna.uts46_remap(ulabel, False, self.transitional)
return _escapify(ulabel)
except (idna.IDNAError, UnicodeError) as e:
raise IDNAException(idna_exception=e)
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 _validate_labels(labels: Tuple[bytes, ...]) -> None:
"""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: Union[bytes, str]) -> bytes:
"""If label is ``str``, convert it to ``bytes``. If it is already
``bytes`` just return it.
"""
if isinstance(label, bytes):
return label
if isinstance(label, str):
return label.encode()
raise ValueError # pragma: no cover
[docs]
@dns.immutable.immutable
class Name:
"""A DNS name.
The dns.name.Name class represents a DNS name as a tuple of
labels. Each label is a ``bytes`` in DNS wire format. Instances
of the class are immutable.
"""
__slots__ = ["labels"]
def __init__(self, labels: Iterable[Union[bytes, str]]):
"""*labels* is any iterable whose values are ``str`` or ``bytes``."""
blabels = [_maybe_convert_to_binary(x) for x in labels]
self.labels = tuple(blabels)
_validate_labels(self.labels)
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().__setattr__("labels", state["labels"])
_validate_labels(self.labels)
[docs]
def is_absolute(self) -> bool:
"""Is the most significant label of this name the root label?
Returns a ``bool``.
"""
return len(self.labels) > 0 and self.labels[-1] == b""
[docs]
def is_wild(self) -> bool:
"""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) -> int:
"""Return a case-insensitive hash of the name.
Returns an ``int``.
"""
h = 0
for label in self.labels:
for c in label.lower():
h += (h << 3) + c
return h
[docs]
def fullcompare(self, other: "Name") -> Tuple[NameRelation, int, int]:
"""Compare two names, returning a 3-tuple
``(relation, order, nlabels)``.
*relation* describes the relation ship between the names,
and is one of: ``dns.name.NameRelation.NONE``,
``dns.name.NameRelation.SUPERDOMAIN``, ``dns.name.NameRelation.SUBDOMAIN``,
``dns.name.NameRelation.EQUAL``, or ``dns.name.NameRelation.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 (NameRelation.NONE, 1, 0)
else:
return (NameRelation.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 = NameRelation.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 = NameRelation.COMMONANCESTOR
return (namereln, order, nlabels)
elif label1 > label2:
order = 1
if nlabels > 0:
namereln = NameRelation.COMMONANCESTOR
return (namereln, order, nlabels)
nlabels += 1
order = ldiff
if ldiff < 0:
namereln = NameRelation.SUPERDOMAIN
elif ldiff > 0:
namereln = NameRelation.SUBDOMAIN
else:
namereln = NameRelation.EQUAL
return (namereln, order, nlabels)
[docs]
def is_subdomain(self, other: "Name") -> bool:
"""Is self a subdomain of other?
Note that the notion of subdomain includes equality, e.g.
"dnspython.org" is a subdomain of itself.
Returns a ``bool``.
"""
(nr, _, _) = self.fullcompare(other)
if nr == NameRelation.SUBDOMAIN or nr == NameRelation.EQUAL:
return True
return False
[docs]
def is_superdomain(self, other: "Name") -> bool:
"""Is self a superdomain of other?
Note that the notion of superdomain includes equality, e.g.
"dnspython.org" is a superdomain of itself.
Returns a ``bool``.
"""
(nr, _, _) = self.fullcompare(other)
if nr == NameRelation.SUPERDOMAIN or nr == NameRelation.EQUAL:
return True
return False
[docs]
def canonicalize(self) -> "Name":
"""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)
[docs]
def to_text(self, omit_final_dot: bool = False) -> str:
"""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 ``str``.
"""
if len(self.labels) == 0:
return "@"
if len(self.labels) == 1 and self.labels[0] == b"":
return "."
if omit_final_dot and self.is_absolute():
l = self.labels[:-1]
else:
l = self.labels
s = ".".join(map(_escapify, l))
return s
[docs]
def to_unicode(
self, omit_final_dot: bool = False, idna_codec: Optional[IDNACodec] = None
) -> str:
"""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 ``str``.
"""
if len(self.labels) == 0:
return "@"
if len(self.labels) == 1 and self.labels[0] == b"":
return "."
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 ".".join([idna_codec.decode(x) for x in l])
[docs]
def to_digestable(self, origin: Optional["Name"] = None) -> bytes:
"""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 ``bytes``.
"""
digest = self.to_wire(origin=origin, canonicalize=True)
assert digest is not None
return digest
[docs]
def to_wire(
self,
file: Optional[Any] = None,
compress: Optional[CompressType] = None,
origin: Optional["Name"] = None,
canonicalize: bool = False,
) -> Optional[bytes]:
"""Convert name to wire format, possibly compressing it.
*file* is the file where the name is emitted (typically an
io.BytesIO file). If ``None`` (the default), a ``bytes``
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. Note that
the compression code assumes that compression offset 0 is the
start of *file*, and thus compression will not be correct
if this is not the case.
*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.
*canonicalize*, a ``bool``, indicates whether the name should
be canonicalized; that is, converted to a format suitable for
digesting in hashes.
Raises ``dns.name.NeedAbsoluteNameOrOrigin`` if the name is
relative and no origin was provided.
Returns a ``bytes`` or ``None``.
"""
if file is None:
out = bytearray()
for label in self.labels:
out.append(len(label))
if canonicalize:
out += label.lower()
else:
out += label
if not self.is_absolute():
if origin is None or not origin.is_absolute():
raise NeedAbsoluteNameOrOrigin
for label in origin.labels:
out.append(len(label))
if canonicalize:
out += label.lower()
else:
out += label
return bytes(out)
labels: Iterable[bytes]
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:
if canonicalize:
file.write(label.lower())
else:
file.write(label)
return None
def __len__(self) -> int:
"""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)
[docs]
def split(self, depth: int) -> Tuple["Name", "Name"]:
"""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:]))
[docs]
def concatenate(self, other: "Name") -> "Name":
"""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)
[docs]
def relativize(self, origin: "Name") -> "Name":
"""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
[docs]
def derelativize(self, origin: "Name") -> "Name":
"""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
[docs]
def choose_relativity(
self, origin: Optional["Name"] = None, relativize: bool = True
) -> "Name":
"""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
[docs]
def parent(self) -> "Name":
"""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:])
[docs]
def predecessor(self, origin: "Name", prefix_ok: bool = True) -> "Name":
"""Return the maximal predecessor of *name* in the DNSSEC ordering in the zone
whose origin is *origin*, or return the longest name under *origin* if the
name is origin (i.e. wrap around to the longest name, which may still be
*origin* due to length considerations.
The relativity of the name is preserved, so if this name is relative
then the method will return a relative name, and likewise if this name
is absolute then the predecessor will be absolute.
*prefix_ok* indicates if prefixing labels is allowed, and
defaults to ``True``. Normally it is good to allow this, but if computing
a maximal predecessor at a zone cut point then ``False`` must be specified.
"""
return _handle_relativity_and_call(
_absolute_predecessor, self, origin, prefix_ok
)
[docs]
def successor(self, origin: "Name", prefix_ok: bool = True) -> "Name":
"""Return the minimal successor of *name* in the DNSSEC ordering in the zone
whose origin is *origin*, or return *origin* if the successor cannot be
computed due to name length limitations.
Note that *origin* is returned in the "too long" cases because wrapping
around to the origin is how NSEC records express "end of the zone".
The relativity of the name is preserved, so if this name is relative
then the method will return a relative name, and likewise if this name
is absolute then the successor will be absolute.
*prefix_ok* indicates if prefixing a new minimal label is allowed, and
defaults to ``True``. Normally it is good to allow this, but if computing
a minimal successor at a zone cut point then ``False`` must be specified.
"""
return _handle_relativity_and_call(_absolute_successor, self, origin, prefix_ok)
#: The root name, '.'
root = Name([b""])
#: The empty name.
empty = Name([])
[docs]
def from_unicode(
text: str, origin: Optional[Name] = root, idna_codec: Optional[IDNACodec] = None
) -> Name:
"""Convert unicode text into a Name object.
Labels are encoded in IDN ACE form according to rules specified by
the IDNA codec.
*text*, a ``str``, 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, str):
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 = ""
escaping = False
edigits = 0
total = 0
if idna_codec is None:
idna_codec = IDNA_2003
if text == "@":
text = ""
if text:
if text in [".", "\u3002", "\uff0e", "\uff61"]:
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 += chr(total)
elif c in [".", "\u3002", "\uff0e", "\uff61"]:
if len(label) == 0:
raise EmptyLabel
labels.append(idna_codec.encode(label))
label = ""
elif c == "\\":
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 is_all_ascii(text: str) -> bool:
for c in text:
if ord(c) > 0x7F:
return False
return True
[docs]
def from_text(
text: Union[bytes, str],
origin: Optional[Name] = root,
idna_codec: Optional[IDNACodec] = None,
) -> Name:
"""Convert text into a Name object.
*text*, a ``bytes`` or ``str``, 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, str):
if not is_all_ascii(text):
# Some codepoint in the input text is > 127, so IDNA applies.
return from_unicode(text, origin, idna_codec)
# The input is all ASCII, so treat this like an ordinary non-IDNA
# domain name. Note that "all ASCII" is about the input text,
# not the codepoints in the domain name. E.g. if text has value
#
# r'\150\151\152\153\154\155\156\157\158\159'
#
# then it's still "all ASCII" even though the domain name has
# codepoints > 127.
text = text.encode("ascii")
if not isinstance(text, bytes):
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 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)
# we need 'dns.wire.Parser' quoted as dns.name and dns.wire depend on each other.
[docs]
def from_wire_parser(parser: "dns.wire.Parser") -> Name:
"""Convert possibly compressed wire format into a Name.
*parser* is a dns.wire.Parser.
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``
"""
labels = []
biggest_pointer = parser.current
with parser.restore_furthest():
count = parser.get_uint8()
while count != 0:
if count < 64:
labels.append(parser.get_bytes(count))
elif count >= 192:
current = (count & 0x3F) * 256 + parser.get_uint8()
if current >= biggest_pointer:
raise BadPointer
biggest_pointer = current
parser.seek(current)
else:
raise BadLabelType
count = parser.get_uint8()
labels.append(b"")
return Name(labels)
[docs]
def from_wire(message: bytes, current: int) -> Tuple[Name, int]:
"""Convert possibly compressed wire format into a Name.
*message* is a ``bytes`` 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, bytes):
raise ValueError("input to from_wire() must be a byte string")
parser = dns.wire.Parser(message, current)
name = from_wire_parser(parser)
return (name, parser.current - current)
# RFC 4471 Support
_MINIMAL_OCTET = b"\x00"
_MINIMAL_OCTET_VALUE = ord(_MINIMAL_OCTET)
_SUCCESSOR_PREFIX = Name([_MINIMAL_OCTET])
_MAXIMAL_OCTET = b"\xff"
_MAXIMAL_OCTET_VALUE = ord(_MAXIMAL_OCTET)
_AT_SIGN_VALUE = ord("@")
_LEFT_SQUARE_BRACKET_VALUE = ord("[")
def _wire_length(labels):
return functools.reduce(lambda v, x: v + len(x) + 1, labels, 0)
def _pad_to_max_name(name):
needed = 255 - _wire_length(name.labels)
new_labels = []
while needed > 64:
new_labels.append(_MAXIMAL_OCTET * 63)
needed -= 64
if needed >= 2:
new_labels.append(_MAXIMAL_OCTET * (needed - 1))
# Note we're already maximal in the needed == 1 case as while we'd like
# to add one more byte as a new label, we can't, as adding a new non-empty
# label requires at least 2 bytes.
new_labels = list(reversed(new_labels))
new_labels.extend(name.labels)
return Name(new_labels)
def _pad_to_max_label(label, suffix_labels):
length = len(label)
# We have to subtract one here to account for the length byte of label.
remaining = 255 - _wire_length(suffix_labels) - length - 1
if remaining <= 0:
# Shouldn't happen!
return label
needed = min(63 - length, remaining)
return label + _MAXIMAL_OCTET * needed
def _absolute_predecessor(name: Name, origin: Name, prefix_ok: bool) -> Name:
# This is the RFC 4471 predecessor algorithm using the "absolute method" of section
# 3.1.1.
#
# Our caller must ensure that the name and origin are absolute, and that name is a
# subdomain of origin.
if name == origin:
return _pad_to_max_name(name)
least_significant_label = name[0]
if least_significant_label == _MINIMAL_OCTET:
return name.parent()
least_octet = least_significant_label[-1]
suffix_labels = name.labels[1:]
if least_octet == _MINIMAL_OCTET_VALUE:
new_labels = [least_significant_label[:-1]]
else:
octets = bytearray(least_significant_label)
octet = octets[-1]
if octet == _LEFT_SQUARE_BRACKET_VALUE:
octet = _AT_SIGN_VALUE
else:
octet -= 1
octets[-1] = octet
least_significant_label = bytes(octets)
new_labels = [_pad_to_max_label(least_significant_label, suffix_labels)]
new_labels.extend(suffix_labels)
name = Name(new_labels)
if prefix_ok:
return _pad_to_max_name(name)
else:
return name
def _absolute_successor(name: Name, origin: Name, prefix_ok: bool) -> Name:
# This is the RFC 4471 successor algorithm using the "absolute method" of section
# 3.1.2.
#
# Our caller must ensure that the name and origin are absolute, and that name is a
# subdomain of origin.
if prefix_ok:
# Try prefixing \000 as new label
try:
return _SUCCESSOR_PREFIX.concatenate(name)
except NameTooLong:
pass
while name != origin:
# Try extending the least significant label.
least_significant_label = name[0]
if len(least_significant_label) < 63:
# We may be able to extend the least label with a minimal additional byte.
# This is only "may" because we could have a maximal length name even though
# the least significant label isn't maximally long.
new_labels = [least_significant_label + _MINIMAL_OCTET]
new_labels.extend(name.labels[1:])
try:
return dns.name.Name(new_labels)
except dns.name.NameTooLong:
pass
# We can't extend the label either, so we'll try to increment the least
# signficant non-maximal byte in it.
octets = bytearray(least_significant_label)
# We do this reversed iteration with an explicit indexing variable because
# if we find something to increment, we're going to want to truncate everything
# to the right of it.
for i in range(len(octets) - 1, -1, -1):
octet = octets[i]
if octet == _MAXIMAL_OCTET_VALUE:
# We can't increment this, so keep looking.
continue
# Finally, something we can increment. We have to apply a special rule for
# incrementing "@", sending it to "[", because RFC 4034 6.1 says that when
# comparing names, uppercase letters compare as if they were their
# lower-case equivalents. If we increment "@" to "A", then it would compare
# as "a", which is after "[", "\", "]", "^", "_", and "`", so we would have
# skipped the most minimal successor, namely "[".
if octet == _AT_SIGN_VALUE:
octet = _LEFT_SQUARE_BRACKET_VALUE
else:
octet += 1
octets[i] = octet
# We can now truncate all of the maximal values we skipped (if any)
new_labels = [bytes(octets[: i + 1])]
new_labels.extend(name.labels[1:])
# We haven't changed the length of the name, so the Name constructor will
# always work.
return Name(new_labels)
# We couldn't increment, so chop off the least significant label and try
# again.
name = name.parent()
# We couldn't increment at all, so return the origin, as wrapping around is the
# DNSSEC way.
return origin
def _handle_relativity_and_call(
function: Callable[[Name, Name, bool], Name],
name: Name,
origin: Name,
prefix_ok: bool,
) -> Name:
# Make "name" absolute if needed, ensure that the origin is absolute,
# call function(), and then relativize the result if needed.
if not origin.is_absolute():
raise NeedAbsoluteNameOrOrigin
relative = not name.is_absolute()
if relative:
name = name.derelativize(origin)
elif not name.is_subdomain(origin):
raise NeedSubdomainOfOrigin
result_name = function(name, origin, prefix_ok)
if relative:
result_name = result_name.relativize(origin)
return result_name