1 # Copyright (C) 2001-2007, 2009, 2010 Nominum, Inc.
3 # Permission to use, copy, modify, and distribute this software and its
4 # documentation for any purpose with or without fee is hereby granted,
5 # provided that the above copyright notice and this permission notice
6 # appear in all copies.
8 # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
9 # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
11 # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
14 # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 """DNS TSIG support."""
25 class BadTime(dns.exception.DNSException):
26 """Raised if the current time is not within the TSIG's validity time."""
29 class BadSignature(dns.exception.DNSException):
30 """Raised if the TSIG signature fails to verify."""
33 class PeerError(dns.exception.DNSException):
34 """Base class for all TSIG errors generated by the remote peer"""
37 class PeerBadKey(PeerError):
38 """Raised if the peer didn't know the key we used"""
41 class PeerBadSignature(PeerError):
42 """Raised if the peer didn't like the signature we sent"""
45 class PeerBadTime(PeerError):
46 """Raised if the peer didn't like the time we sent"""
49 class PeerBadTruncation(PeerError):
50 """Raised if the peer didn't like amount of truncation in the TSIG we sent"""
53 default_algorithm = "HMAC-MD5.SIG-ALG.REG.INT"
60 def sign(wire, keyname, secret, time, fudge, original_id, error,
61 other_data, request_mac, ctx=None, multi=False, first=True,
62 algorithm=default_algorithm):
63 """Return a (tsig_rdata, mac, ctx) tuple containing the HMAC TSIG rdata
64 for the input parameters, the HMAC MAC calculated by applying the
65 TSIG signature algorithm, and the TSIG digest context.
66 @rtype: (string, string, hmac.HMAC object)
67 @raises ValueError: I{other_data} is too long
68 @raises NotImplementedError: I{algorithm} is not supported
71 (algorithm_name, digestmod) = get_algorithm(algorithm)
73 ctx = hmac.new(secret, digestmod=digestmod)
76 ctx.update(struct.pack('!H', ml))
77 ctx.update(request_mac)
78 id = struct.pack('!H', original_id)
82 ctx.update(keyname.to_digestable())
83 ctx.update(struct.pack('!H', dns.rdataclass.ANY))
84 ctx.update(struct.pack('!I', 0))
86 upper_time = (long_time >> 32) & 0xffffL
87 lower_time = long_time & 0xffffffffL
88 time_mac = struct.pack('!HIH', upper_time, lower_time, fudge)
89 pre_mac = algorithm_name + time_mac
92 raise ValueError('TSIG Other Data is > 65535 bytes')
93 post_mac = struct.pack('!HH', error, ol) + other_data
100 mpack = struct.pack('!H', len(mac))
101 tsig_rdata = pre_mac + mpack + mac + id + post_mac
103 ctx = hmac.new(secret)
105 ctx.update(struct.pack('!H', ml))
109 return (tsig_rdata, mac, ctx)
111 def hmac_md5(wire, keyname, secret, time, fudge, original_id, error,
112 other_data, request_mac, ctx=None, multi=False, first=True,
113 algorithm=default_algorithm):
114 return sign(wire, keyname, secret, time, fudge, original_id, error,
115 other_data, request_mac, ctx, multi, first, algorithm)
117 def validate(wire, keyname, secret, now, request_mac, tsig_start, tsig_rdata,
118 tsig_rdlen, ctx=None, multi=False, first=True):
119 """Validate the specified TSIG rdata against the other input parameters.
121 @raises FormError: The TSIG is badly formed.
122 @raises BadTime: There is too much time skew between the client and the
124 @raises BadSignature: The TSIG signature did not validate
125 @rtype: hmac.HMAC object"""
127 (adcount,) = struct.unpack("!H", wire[10:12])
129 raise dns.exception.FormError
131 new_wire = wire[0:10] + struct.pack("!H", adcount) + wire[12:tsig_start]
133 (aname, used) = dns.name.from_wire(wire, current)
134 current = current + used
135 (upper_time, lower_time, fudge, mac_size) = \
136 struct.unpack("!HIHH", wire[current:current + 10])
137 time = ((upper_time + 0L) << 32) + (lower_time + 0L)
139 mac = wire[current:current + mac_size]
141 (original_id, error, other_size) = \
142 struct.unpack("!HHH", wire[current:current + 6])
144 other_data = wire[current:current + other_size]
145 current += other_size
146 if current != tsig_rdata + tsig_rdlen:
147 raise dns.exception.FormError
150 raise PeerBadSignature
151 elif error == BADKEY:
153 elif error == BADTIME:
155 elif error == BADTRUNC:
156 raise PeerBadTruncation
158 raise PeerError('unknown TSIG error code %d' % error)
159 time_low = time - fudge
160 time_high = time + fudge
161 if now < time_low or now > time_high:
163 (junk, our_mac, ctx) = sign(new_wire, keyname, secret, time, fudge,
164 original_id, error, other_data,
165 request_mac, ctx, multi, first, aname)
170 def get_algorithm(algorithm):
171 """Returns the wire format string and the hash module to use for the
172 specified TSIG algorithm
174 @rtype: (string, hash constructor)
175 @raises NotImplementedError: I{algorithm} is not supported
181 hashes[dns.name.from_text('hmac-sha224')] = hashlib.sha224
182 hashes[dns.name.from_text('hmac-sha256')] = hashlib.sha256
183 hashes[dns.name.from_text('hmac-sha384')] = hashlib.sha384
184 hashes[dns.name.from_text('hmac-sha512')] = hashlib.sha512
185 hashes[dns.name.from_text('hmac-sha1')] = hashlib.sha1
186 hashes[dns.name.from_text('HMAC-MD5.SIG-ALG.REG.INT')] = hashlib.md5
189 if sys.hexversion < 0x02050000:
190 # hashlib doesn't conform to PEP 247: API for
191 # Cryptographic Hash Functions, which hmac before python
192 # 2.5 requires, so add the necessary items.
193 class HashlibWrapper:
194 def __init__(self, basehash):
195 self.basehash = basehash
196 self.digest_size = self.basehash().digest_size
198 def new(self, *args, **kwargs):
199 return self.basehash(*args, **kwargs)
202 hashes[name] = HashlibWrapper(hashes[name])
206 hashes[dns.name.from_text('HMAC-MD5.SIG-ALG.REG.INT')] = md5.md5
207 hashes[dns.name.from_text('hmac-sha1')] = sha.sha
209 if isinstance(algorithm, (str, unicode)):
210 algorithm = dns.name.from_text(algorithm)
212 if algorithm in hashes:
213 return (algorithm.to_digestable(), hashes[algorithm])
215 raise NotImplementedError("TSIG algorithm " + str(algorithm) +