362 lines
11 KiB
Python
362 lines
11 KiB
Python
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
|
|
|
|
# Copyright (C) 2001-2007, 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.
|
|
|
|
"""DNS TSIG support."""
|
|
|
|
import base64
|
|
import hashlib
|
|
import hmac
|
|
import struct
|
|
|
|
import dns.exception
|
|
import dns.name
|
|
import dns.rcode
|
|
import dns.rdataclass
|
|
|
|
|
|
class BadTime(dns.exception.DNSException):
|
|
|
|
"""The current time is not within the TSIG's validity time."""
|
|
|
|
|
|
class BadSignature(dns.exception.DNSException):
|
|
|
|
"""The TSIG signature fails to verify."""
|
|
|
|
|
|
class BadKey(dns.exception.DNSException):
|
|
|
|
"""The TSIG record owner name does not match the key."""
|
|
|
|
|
|
class BadAlgorithm(dns.exception.DNSException):
|
|
|
|
"""The TSIG algorithm does not match the key."""
|
|
|
|
|
|
class PeerError(dns.exception.DNSException):
|
|
|
|
"""Base class for all TSIG errors generated by the remote peer"""
|
|
|
|
|
|
class PeerBadKey(PeerError):
|
|
|
|
"""The peer didn't know the key we used"""
|
|
|
|
|
|
class PeerBadSignature(PeerError):
|
|
|
|
"""The peer didn't like the signature we sent"""
|
|
|
|
|
|
class PeerBadTime(PeerError):
|
|
|
|
"""The peer didn't like the time we sent"""
|
|
|
|
|
|
class PeerBadTruncation(PeerError):
|
|
|
|
"""The peer didn't like amount of truncation in the TSIG we sent"""
|
|
|
|
|
|
# TSIG Algorithms
|
|
|
|
HMAC_MD5 = dns.name.from_text("HMAC-MD5.SIG-ALG.REG.INT")
|
|
HMAC_SHA1 = dns.name.from_text("hmac-sha1")
|
|
HMAC_SHA224 = dns.name.from_text("hmac-sha224")
|
|
HMAC_SHA256 = dns.name.from_text("hmac-sha256")
|
|
HMAC_SHA256_128 = dns.name.from_text("hmac-sha256-128")
|
|
HMAC_SHA384 = dns.name.from_text("hmac-sha384")
|
|
HMAC_SHA384_192 = dns.name.from_text("hmac-sha384-192")
|
|
HMAC_SHA512 = dns.name.from_text("hmac-sha512")
|
|
HMAC_SHA512_256 = dns.name.from_text("hmac-sha512-256")
|
|
GSS_TSIG = dns.name.from_text("gss-tsig")
|
|
|
|
default_algorithm = HMAC_SHA256
|
|
|
|
mac_sizes = {
|
|
HMAC_SHA1: 20,
|
|
HMAC_SHA224: 28,
|
|
HMAC_SHA256: 32,
|
|
HMAC_SHA256_128: 16,
|
|
HMAC_SHA384: 48,
|
|
HMAC_SHA384_192: 24,
|
|
HMAC_SHA512: 64,
|
|
HMAC_SHA512_256: 32,
|
|
HMAC_MD5: 16,
|
|
GSS_TSIG: 128, # This is what we assume to be the worst case!
|
|
}
|
|
|
|
|
|
class GSSTSig:
|
|
"""
|
|
GSS-TSIG TSIG implementation. This uses the GSS-API context established
|
|
in the TKEY message handshake to sign messages using GSS-API message
|
|
integrity codes, per the RFC.
|
|
|
|
In order to avoid a direct GSSAPI dependency, the keyring holds a ref
|
|
to the GSSAPI object required, rather than the key itself.
|
|
"""
|
|
|
|
def __init__(self, gssapi_context):
|
|
self.gssapi_context = gssapi_context
|
|
self.data = b""
|
|
self.name = "gss-tsig"
|
|
|
|
def update(self, data):
|
|
self.data += data
|
|
|
|
def sign(self):
|
|
# defer to the GSSAPI function to sign
|
|
return self.gssapi_context.get_signature(self.data)
|
|
|
|
def verify(self, expected):
|
|
try:
|
|
# defer to the GSSAPI function to verify
|
|
return self.gssapi_context.verify_signature(self.data, expected)
|
|
except Exception:
|
|
# note the usage of a bare exception
|
|
raise BadSignature
|
|
|
|
|
|
class GSSTSigAdapter:
|
|
def __init__(self, keyring):
|
|
self.keyring = keyring
|
|
|
|
def __call__(self, message, keyname):
|
|
if keyname in self.keyring:
|
|
key = self.keyring[keyname]
|
|
if isinstance(key, Key) and key.algorithm == GSS_TSIG:
|
|
if message:
|
|
GSSTSigAdapter.parse_tkey_and_step(key, message, keyname)
|
|
return key
|
|
else:
|
|
return None
|
|
|
|
@classmethod
|
|
def parse_tkey_and_step(cls, key, message, keyname):
|
|
# if the message is a TKEY type, absorb the key material
|
|
# into the context using step(); this is used to allow the
|
|
# client to complete the GSSAPI negotiation before attempting
|
|
# to verify the signed response to a TKEY message exchange
|
|
try:
|
|
rrset = message.find_rrset(
|
|
message.answer, keyname, dns.rdataclass.ANY, dns.rdatatype.TKEY
|
|
)
|
|
if rrset:
|
|
token = rrset[0].key
|
|
gssapi_context = key.secret
|
|
return gssapi_context.step(token)
|
|
except KeyError:
|
|
pass
|
|
|
|
|
|
class HMACTSig:
|
|
"""
|
|
HMAC TSIG implementation. This uses the HMAC python module to handle the
|
|
sign/verify operations.
|
|
"""
|
|
|
|
_hashes = {
|
|
HMAC_SHA1: hashlib.sha1,
|
|
HMAC_SHA224: hashlib.sha224,
|
|
HMAC_SHA256: hashlib.sha256,
|
|
HMAC_SHA256_128: (hashlib.sha256, 128),
|
|
HMAC_SHA384: hashlib.sha384,
|
|
HMAC_SHA384_192: (hashlib.sha384, 192),
|
|
HMAC_SHA512: hashlib.sha512,
|
|
HMAC_SHA512_256: (hashlib.sha512, 256),
|
|
HMAC_MD5: hashlib.md5,
|
|
}
|
|
|
|
def __init__(self, key, algorithm):
|
|
try:
|
|
hashinfo = self._hashes[algorithm]
|
|
except KeyError:
|
|
raise NotImplementedError(f"TSIG algorithm {algorithm} is not supported")
|
|
|
|
# create the HMAC context
|
|
if isinstance(hashinfo, tuple):
|
|
self.hmac_context = hmac.new(key, digestmod=hashinfo[0])
|
|
self.size = hashinfo[1]
|
|
else:
|
|
self.hmac_context = hmac.new(key, digestmod=hashinfo)
|
|
self.size = None
|
|
self.name = self.hmac_context.name
|
|
if self.size:
|
|
self.name += f"-{self.size}"
|
|
|
|
def update(self, data):
|
|
return self.hmac_context.update(data)
|
|
|
|
def sign(self):
|
|
# defer to the HMAC digest() function for that digestmod
|
|
digest = self.hmac_context.digest()
|
|
if self.size:
|
|
digest = digest[: (self.size // 8)]
|
|
return digest
|
|
|
|
def verify(self, expected):
|
|
# re-digest and compare the results
|
|
mac = self.sign()
|
|
if not hmac.compare_digest(mac, expected):
|
|
raise BadSignature
|
|
|
|
|
|
def _digest(wire, key, rdata, time=None, request_mac=None, ctx=None, multi=None):
|
|
"""Return a context containing the TSIG rdata for the input parameters
|
|
@rtype: dns.tsig.HMACTSig or dns.tsig.GSSTSig object
|
|
@raises ValueError: I{other_data} is too long
|
|
@raises NotImplementedError: I{algorithm} is not supported
|
|
"""
|
|
|
|
first = not (ctx and multi)
|
|
if first:
|
|
ctx = get_context(key)
|
|
if request_mac:
|
|
ctx.update(struct.pack("!H", len(request_mac)))
|
|
ctx.update(request_mac)
|
|
ctx.update(struct.pack("!H", rdata.original_id))
|
|
ctx.update(wire[2:])
|
|
if first:
|
|
ctx.update(key.name.to_digestable())
|
|
ctx.update(struct.pack("!H", dns.rdataclass.ANY))
|
|
ctx.update(struct.pack("!I", 0))
|
|
if time is None:
|
|
time = rdata.time_signed
|
|
upper_time = (time >> 32) & 0xFFFF
|
|
lower_time = time & 0xFFFFFFFF
|
|
time_encoded = struct.pack("!HIH", upper_time, lower_time, rdata.fudge)
|
|
other_len = len(rdata.other)
|
|
if other_len > 65535:
|
|
raise ValueError("TSIG Other Data is > 65535 bytes")
|
|
if first:
|
|
ctx.update(key.algorithm.to_digestable() + time_encoded)
|
|
ctx.update(struct.pack("!HH", rdata.error, other_len) + rdata.other)
|
|
else:
|
|
ctx.update(time_encoded)
|
|
return ctx
|
|
|
|
|
|
def _maybe_start_digest(key, mac, multi):
|
|
"""If this is the first message in a multi-message sequence,
|
|
start a new context.
|
|
@rtype: dns.tsig.HMACTSig or dns.tsig.GSSTSig object
|
|
"""
|
|
if multi:
|
|
ctx = get_context(key)
|
|
ctx.update(struct.pack("!H", len(mac)))
|
|
ctx.update(mac)
|
|
return ctx
|
|
else:
|
|
return None
|
|
|
|
|
|
def sign(wire, key, rdata, time=None, request_mac=None, ctx=None, multi=False):
|
|
"""Return a (tsig_rdata, mac, ctx) tuple containing the HMAC TSIG rdata
|
|
for the input parameters, the HMAC MAC calculated by applying the
|
|
TSIG signature algorithm, and the TSIG digest context.
|
|
@rtype: (string, dns.tsig.HMACTSig or dns.tsig.GSSTSig object)
|
|
@raises ValueError: I{other_data} is too long
|
|
@raises NotImplementedError: I{algorithm} is not supported
|
|
"""
|
|
|
|
ctx = _digest(wire, key, rdata, time, request_mac, ctx, multi)
|
|
mac = ctx.sign()
|
|
tsig = rdata.replace(time_signed=time, mac=mac)
|
|
|
|
return (tsig, _maybe_start_digest(key, mac, multi))
|
|
|
|
|
|
def validate(
|
|
wire, key, owner, rdata, now, request_mac, tsig_start, ctx=None, multi=False
|
|
):
|
|
"""Validate the specified TSIG rdata against the other input parameters.
|
|
|
|
@raises FormError: The TSIG is badly formed.
|
|
@raises BadTime: There is too much time skew between the client and the
|
|
server.
|
|
@raises BadSignature: The TSIG signature did not validate
|
|
@rtype: dns.tsig.HMACTSig or dns.tsig.GSSTSig object"""
|
|
|
|
(adcount,) = struct.unpack("!H", wire[10:12])
|
|
if adcount == 0:
|
|
raise dns.exception.FormError
|
|
adcount -= 1
|
|
new_wire = wire[0:10] + struct.pack("!H", adcount) + wire[12:tsig_start]
|
|
if rdata.error != 0:
|
|
if rdata.error == dns.rcode.BADSIG:
|
|
raise PeerBadSignature
|
|
elif rdata.error == dns.rcode.BADKEY:
|
|
raise PeerBadKey
|
|
elif rdata.error == dns.rcode.BADTIME:
|
|
raise PeerBadTime
|
|
elif rdata.error == dns.rcode.BADTRUNC:
|
|
raise PeerBadTruncation
|
|
else:
|
|
raise PeerError("unknown TSIG error code %d" % rdata.error)
|
|
if abs(rdata.time_signed - now) > rdata.fudge:
|
|
raise BadTime
|
|
if key.name != owner:
|
|
raise BadKey
|
|
if key.algorithm != rdata.algorithm:
|
|
raise BadAlgorithm
|
|
ctx = _digest(new_wire, key, rdata, None, request_mac, ctx, multi)
|
|
ctx.verify(rdata.mac)
|
|
return _maybe_start_digest(key, rdata.mac, multi)
|
|
|
|
|
|
def get_context(key):
|
|
"""Returns an HMAC context for the specified key.
|
|
|
|
@rtype: HMAC context
|
|
@raises NotImplementedError: I{algorithm} is not supported
|
|
"""
|
|
|
|
if key.algorithm == GSS_TSIG:
|
|
return GSSTSig(key.secret)
|
|
else:
|
|
return HMACTSig(key.secret, key.algorithm)
|
|
|
|
|
|
class Key:
|
|
def __init__(self, name, secret, algorithm=default_algorithm):
|
|
if isinstance(name, str):
|
|
name = dns.name.from_text(name)
|
|
self.name = name
|
|
if isinstance(secret, str):
|
|
secret = base64.decodebytes(secret.encode())
|
|
self.secret = secret
|
|
if isinstance(algorithm, str):
|
|
algorithm = dns.name.from_text(algorithm)
|
|
self.algorithm = algorithm
|
|
|
|
def __eq__(self, other):
|
|
return (
|
|
isinstance(other, Key)
|
|
and self.name == other.name
|
|
and self.secret == other.secret
|
|
and self.algorithm == other.algorithm
|
|
)
|
|
|
|
def __repr__(self):
|
|
r = f"<DNS key name='{self.name}', " + f"algorithm='{self.algorithm}'"
|
|
if self.algorithm != GSS_TSIG:
|
|
r += f", secret='{base64.b64encode(self.secret).decode()}'"
|
|
r += ">"
|
|
return r
|