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# Copyright (C) 2003-2007, 2009, 2011 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.
"""Common DNSSEC-related functions and constants."""
from io import BytesIO
import struct
import time
import dns.exception
import dns.hash
import dns.name
import dns.node
import dns.rdataset
import dns.rdata
import dns.rdatatype
import dns.rdataclass
from ._compat import string_types
class UnsupportedAlgorithm(dns.exception.DNSException):
"""The DNSSEC algorithm is not supported."""
class ValidationFailure(dns.exception.DNSException):
"""The DNSSEC signature is invalid."""
RSAMD5 = 1
DH = 2
DSA = 3
ECC = 4
RSASHA1 = 5
DSANSEC3SHA1 = 6
RSASHA1NSEC3SHA1 = 7
RSASHA256 = 8
RSASHA512 = 10
ECDSAP256SHA256 = 13
ECDSAP384SHA384 = 14
INDIRECT = 252
PRIVATEDNS = 253
PRIVATEOID = 254
_algorithm_by_text = {
'RSAMD5': RSAMD5,
'DH': DH,
'DSA': DSA,
'ECC': ECC,
'RSASHA1': RSASHA1,
'DSANSEC3SHA1': DSANSEC3SHA1,
'RSASHA1NSEC3SHA1': RSASHA1NSEC3SHA1,
'RSASHA256': RSASHA256,
'RSASHA512': RSASHA512,
'INDIRECT': INDIRECT,
'ECDSAP256SHA256': ECDSAP256SHA256,
'ECDSAP384SHA384': ECDSAP384SHA384,
'PRIVATEDNS': PRIVATEDNS,
'PRIVATEOID': PRIVATEOID,
}
# We construct the inverse mapping programmatically to ensure that we
# cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
# would cause the mapping not to be true inverse.
_algorithm_by_value = dict((y, x) for x, y in _algorithm_by_text.items())
def algorithm_from_text(text):
"""Convert text into a DNSSEC algorithm value
@rtype: int"""
value = _algorithm_by_text.get(text.upper())
if value is None:
value = int(text)
return value
def algorithm_to_text(value):
"""Convert a DNSSEC algorithm value to text
@rtype: string"""
text = _algorithm_by_value.get(value)
if text is None:
text = str(value)
return text
def _to_rdata(record, origin):
s = BytesIO()
record.to_wire(s, origin=origin)
return s.getvalue()
def key_id(key, origin=None):
rdata = _to_rdata(key, origin)
rdata = bytearray(rdata)
if key.algorithm == RSAMD5:
return (rdata[-3] << 8) + rdata[-2]
else:
total = 0
for i in range(len(rdata) // 2):
total += (rdata[2 * i] << 8) + \
rdata[2 * i + 1]
if len(rdata) % 2 != 0:
total += rdata[len(rdata) - 1] << 8
total += ((total >> 16) & 0xffff)
return total & 0xffff
def make_ds(name, key, algorithm, origin=None):
if algorithm.upper() == 'SHA1':
dsalg = 1
hash = dns.hash.hashes['SHA1']()
elif algorithm.upper() == 'SHA256':
dsalg = 2
hash = dns.hash.hashes['SHA256']()
else:
raise UnsupportedAlgorithm('unsupported algorithm "%s"' % algorithm)
if isinstance(name, string_types):
name = dns.name.from_text(name, origin)
hash.update(name.canonicalize().to_wire())
hash.update(_to_rdata(key, origin))
digest = hash.digest()
dsrdata = struct.pack("!HBB", key_id(key), key.algorithm, dsalg) + digest
return dns.rdata.from_wire(dns.rdataclass.IN, dns.rdatatype.DS, dsrdata, 0,
len(dsrdata))
def _find_candidate_keys(keys, rrsig):
candidate_keys = []
value = keys.get(rrsig.signer)
if value is None:
return None
if isinstance(value, dns.node.Node):
try:
rdataset = value.find_rdataset(dns.rdataclass.IN,
dns.rdatatype.DNSKEY)
except KeyError:
return None
else:
rdataset = value
for rdata in rdataset:
if rdata.algorithm == rrsig.algorithm and \
key_id(rdata) == rrsig.key_tag:
candidate_keys.append(rdata)
return candidate_keys
def _is_rsa(algorithm):
return algorithm in (RSAMD5, RSASHA1,
RSASHA1NSEC3SHA1, RSASHA256,
RSASHA512)
def _is_dsa(algorithm):
return algorithm in (DSA, DSANSEC3SHA1)
def _is_ecdsa(algorithm):
return _have_ecdsa and (algorithm in (ECDSAP256SHA256, ECDSAP384SHA384))
def _is_md5(algorithm):
return algorithm == RSAMD5
def _is_sha1(algorithm):
return algorithm in (DSA, RSASHA1,
DSANSEC3SHA1, RSASHA1NSEC3SHA1)
def _is_sha256(algorithm):
return algorithm in (RSASHA256, ECDSAP256SHA256)
def _is_sha384(algorithm):
return algorithm == ECDSAP384SHA384
def _is_sha512(algorithm):
return algorithm == RSASHA512
def _make_hash(algorithm):
if _is_md5(algorithm):
return dns.hash.hashes['MD5']()
if _is_sha1(algorithm):
return dns.hash.hashes['SHA1']()
if _is_sha256(algorithm):
return dns.hash.hashes['SHA256']()
if _is_sha384(algorithm):
return dns.hash.hashes['SHA384']()
if _is_sha512(algorithm):
return dns.hash.hashes['SHA512']()
raise ValidationFailure('unknown hash for algorithm %u' % algorithm)
def _make_algorithm_id(algorithm):
if _is_md5(algorithm):
oid = [0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05]
elif _is_sha1(algorithm):
oid = [0x2b, 0x0e, 0x03, 0x02, 0x1a]
elif _is_sha256(algorithm):
oid = [0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01]
elif _is_sha512(algorithm):
oid = [0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03]
else:
raise ValidationFailure('unknown algorithm %u' % algorithm)
olen = len(oid)
dlen = _make_hash(algorithm).digest_size
idbytes = [0x30] + [8 + olen + dlen] + \
[0x30, olen + 4] + [0x06, olen] + oid + \
[0x05, 0x00] + [0x04, dlen]
return struct.pack('!%dB' % len(idbytes), *idbytes)
def _validate_rrsig(rrset, rrsig, keys, origin=None, now=None):
"""Validate an RRset against a single signature rdata
The owner name of the rrsig is assumed to be the same as the owner name
of the rrset.
@param rrset: The RRset to validate
@type rrset: dns.rrset.RRset or (dns.name.Name, dns.rdataset.Rdataset)
tuple
@param rrsig: The signature rdata
@type rrsig: dns.rrset.Rdata
@param keys: The key dictionary.
@type keys: a dictionary keyed by dns.name.Name with node or rdataset
values
@param origin: The origin to use for relative names
@type origin: dns.name.Name or None
@param now: The time to use when validating the signatures. The default
is the current time.
@type now: int
"""
if isinstance(origin, string_types):
origin = dns.name.from_text(origin, dns.name.root)
for candidate_key in _find_candidate_keys(keys, rrsig):
if not candidate_key:
raise ValidationFailure('unknown key')
# For convenience, allow the rrset to be specified as a (name,
# rdataset) tuple as well as a proper rrset
if isinstance(rrset, tuple):
rrname = rrset[0]
rdataset = rrset[1]
else:
rrname = rrset.name
rdataset = rrset
if now is None:
now = time.time()
if rrsig.expiration < now:
raise ValidationFailure('expired')
if rrsig.inception > now:
raise ValidationFailure('not yet valid')
hash = _make_hash(rrsig.algorithm)
if _is_rsa(rrsig.algorithm):
keyptr = candidate_key.key
(bytes_,) = struct.unpack('!B', keyptr[0:1])
keyptr = keyptr[1:]
if bytes_ == 0:
(bytes_,) = struct.unpack('!H', keyptr[0:2])
keyptr = keyptr[2:]
rsa_e = keyptr[0:bytes_]
rsa_n = keyptr[bytes_:]
keylen = len(rsa_n) * 8
pubkey = Crypto.PublicKey.RSA.construct(
(Crypto.Util.number.bytes_to_long(rsa_n),
Crypto.Util.number.bytes_to_long(rsa_e)))
sig = (Crypto.Util.number.bytes_to_long(rrsig.signature),)
elif _is_dsa(rrsig.algorithm):
keyptr = candidate_key.key
(t,) = struct.unpack('!B', keyptr[0:1])
keyptr = keyptr[1:]
octets = 64 + t * 8
dsa_q = keyptr[0:20]
keyptr = keyptr[20:]
dsa_p = keyptr[0:octets]
keyptr = keyptr[octets:]
dsa_g = keyptr[0:octets]
keyptr = keyptr[octets:]
dsa_y = keyptr[0:octets]
pubkey = Crypto.PublicKey.DSA.construct(
(Crypto.Util.number.bytes_to_long(dsa_y),
Crypto.Util.number.bytes_to_long(dsa_g),
Crypto.Util.number.bytes_to_long(dsa_p),
Crypto.Util.number.bytes_to_long(dsa_q)))
(dsa_r, dsa_s) = struct.unpack('!20s20s', rrsig.signature[1:])
sig = (Crypto.Util.number.bytes_to_long(dsa_r),
Crypto.Util.number.bytes_to_long(dsa_s))
elif _is_ecdsa(rrsig.algorithm):
if rrsig.algorithm == ECDSAP256SHA256:
curve = ecdsa.curves.NIST256p
key_len = 32
elif rrsig.algorithm == ECDSAP384SHA384:
curve = ecdsa.curves.NIST384p
key_len = 48
else:
# shouldn't happen
raise ValidationFailure('unknown ECDSA curve')
keyptr = candidate_key.key
x = Crypto.Util.number.bytes_to_long(keyptr[0:key_len])
y = Crypto.Util.number.bytes_to_long(keyptr[key_len:key_len * 2])
assert ecdsa.ecdsa.point_is_valid(curve.generator, x, y)
point = ecdsa.ellipticcurve.Point(curve.curve, x, y, curve.order)
verifying_key = ecdsa.keys.VerifyingKey.from_public_point(point,
curve)
pubkey = ECKeyWrapper(verifying_key, key_len)
r = rrsig.signature[:key_len]
s = rrsig.signature[key_len:]
sig = ecdsa.ecdsa.Signature(Crypto.Util.number.bytes_to_long(r),
Crypto.Util.number.bytes_to_long(s))
else:
raise ValidationFailure('unknown algorithm %u' % rrsig.algorithm)
hash.update(_to_rdata(rrsig, origin)[:18])
hash.update(rrsig.signer.to_digestable(origin))
if rrsig.labels < len(rrname) - 1:
suffix = rrname.split(rrsig.labels + 1)[1]
rrname = dns.name.from_text('*', suffix)
rrnamebuf = rrname.to_digestable(origin)
rrfixed = struct.pack('!HHI', rdataset.rdtype, rdataset.rdclass,
rrsig.original_ttl)
rrlist = sorted(rdataset)
for rr in rrlist:
hash.update(rrnamebuf)
hash.update(rrfixed)
rrdata = rr.to_digestable(origin)
rrlen = struct.pack('!H', len(rrdata))
hash.update(rrlen)
hash.update(rrdata)
digest = hash.digest()
if _is_rsa(rrsig.algorithm):
# PKCS1 algorithm identifier goop
digest = _make_algorithm_id(rrsig.algorithm) + digest
padlen = keylen // 8 - len(digest) - 3
digest = struct.pack('!%dB' % (2 + padlen + 1),
*([0, 1] + [0xFF] * padlen + [0])) + digest
elif _is_dsa(rrsig.algorithm) or _is_ecdsa(rrsig.algorithm):
pass
else:
# Raise here for code clarity; this won't actually ever happen
# since if the algorithm is really unknown we'd already have
# raised an exception above
raise ValidationFailure('unknown algorithm %u' % rrsig.algorithm)
if pubkey.verify(digest, sig):
return
raise ValidationFailure('verify failure')
def _validate(rrset, rrsigset, keys, origin=None, now=None):
"""Validate an RRset
@param rrset: The RRset to validate
@type rrset: dns.rrset.RRset or (dns.name.Name, dns.rdataset.Rdataset)
tuple
@param rrsigset: The signature RRset
@type rrsigset: dns.rrset.RRset or (dns.name.Name, dns.rdataset.Rdataset)
tuple
@param keys: The key dictionary.
@type keys: a dictionary keyed by dns.name.Name with node or rdataset
values
@param origin: The origin to use for relative names
@type origin: dns.name.Name or None
@param now: The time to use when validating the signatures. The default
is the current time.
@type now: int
"""
if isinstance(origin, string_types):
origin = dns.name.from_text(origin, dns.name.root)
if isinstance(rrset, tuple):
rrname = rrset[0]
else:
rrname = rrset.name
if isinstance(rrsigset, tuple):
rrsigname = rrsigset[0]
rrsigrdataset = rrsigset[1]
else:
rrsigname = rrsigset.name
rrsigrdataset = rrsigset
rrname = rrname.choose_relativity(origin)
rrsigname = rrname.choose_relativity(origin)
if rrname != rrsigname:
raise ValidationFailure("owner names do not match")
for rrsig in rrsigrdataset:
try:
_validate_rrsig(rrset, rrsig, keys, origin, now)
return
except ValidationFailure:
pass
raise ValidationFailure("no RRSIGs validated")
def _need_pycrypto(*args, **kwargs):
raise NotImplementedError("DNSSEC validation requires pycrypto")
try:
import Crypto.PublicKey.RSA
import Crypto.PublicKey.DSA
import Crypto.Util.number
validate = _validate
validate_rrsig = _validate_rrsig
_have_pycrypto = True
except ImportError:
validate = _need_pycrypto
validate_rrsig = _need_pycrypto
_have_pycrypto = False
try:
import ecdsa
import ecdsa.ecdsa
import ecdsa.ellipticcurve
import ecdsa.keys
_have_ecdsa = True
class ECKeyWrapper(object):
def __init__(self, key, key_len):
self.key = key
self.key_len = key_len
def verify(self, digest, sig):
diglong = Crypto.Util.number.bytes_to_long(digest)
return self.key.pubkey.verifies(diglong, sig)
except ImportError:
_have_ecdsa = False