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1 | # ldd - DNS implementation in Python |
2 | # Copyright (C) 2006 Fredrik Tolf <fredrik@dolda2000.com> |
3 | # |
4 | # This program is free software; you can redistribute it and/or modify |
5 | # it under the terms of the GNU General Public License as published by |
6 | # the Free Software Foundation; either version 2 of the License, or |
7 | # (at your option) any later version. |
8 | # |
9 | # This program is distributed in the hope that it will be useful, |
10 | # but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
12 | # GNU General Public License for more details. |
13 | # |
14 | # You should have received a copy of the GNU General Public License |
15 | # along with this program; if not, write to the Free Software |
16 | # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
17 | |
18 | import socket |
19 | import select |
20 | import time |
21 | import random |
22 | |
23 | import proto |
24 | import rec |
25 | import dn |
26 | |
27 | class error(Exception): |
28 | def __init__(self, text): |
29 | self.text = text |
30 | |
31 | def __str__(self): |
32 | return self.text |
33 | |
34 | class servfail(error): |
35 | def __init__(self): |
36 | error.__init__(self, "SERVFAIL") |
37 | |
38 | class unreachable(error): |
39 | def __init__(self, server): |
40 | error.__init__(self, "could not reach server: " + str(server)) |
41 | |
42 | def resolvecnames(pkt, res = None): |
43 | if res is None: res = default |
44 | for q in pkt.qlist: |
45 | cnrr = pkt.getanswer(q.name, rec.rtypebyname("CNAME")) |
46 | if cnrr is not None: |
47 | if pkt.getanswer(cnrr.data["priname"], q.rtype) is None: |
48 | try: |
49 | resp = res.squery(cnrr.data["priname"], q.rtype) |
50 | except error: |
51 | continue |
52 | if resp is None: |
53 | continue |
54 | anrr = resp.getanswer(cnrr.data["priname"], q.rtype) |
55 | if anrr is None: |
56 | continue |
57 | pkt.addan(anrr) |
58 | |
59 | def resolveadditional(pkt, rr, res = None): |
60 | if res is None: res = default |
61 | for name in rr.data: |
62 | if isinstance(rr.data[name], dn.domainname): |
63 | for rtype in ["A", "AAAA"]: |
64 | if pkt.getanswer(rr.data[name], rtype) is not None: |
65 | continue |
66 | try: |
67 | resp = res.squery(rr.data[name], rtype) |
68 | except error: |
69 | continue |
70 | if resp is None: |
71 | continue |
72 | anrr = resp.getanswer(rr.data[name], rtype) |
73 | if anrr is None: |
74 | continue |
75 | pkt.addad(anrr) |
76 | |
77 | def extractaddrinfo(packet, name): |
78 | ret = [] |
79 | for rr in packet.anlist + packet.adlist: |
80 | if rr.head.name == name: |
81 | if rr.head.istype("A"): |
82 | ret += [(socket.AF_INET, socket.inet_ntop(socket.AF_INET, rr.data["address"]))] |
83 | elif rr.head.istype("AAAA"): |
84 | ret += [(socket.AF_INET6, socket.inet_ntop(socket.AF_INET6, rr.data["address"]))] |
85 | return ret |
86 | |
87 | def resolve(packet, nameserver, recurse, retries = 3, timeout = 2000, hops = 0, cnameres = None, verbose = False, visited = None): |
88 | if cnameres is None: cnameres = default |
89 | if visited is None: visited = set() |
90 | visited |= set([nameserver]) |
91 | sk = socket.socket(nameserver[0], socket.SOCK_DGRAM) |
92 | sk.bind(("", 0)) |
93 | for i in range(retries): |
94 | sk.sendto(packet.encode(), nameserver[1:]) |
95 | p = select.poll() |
96 | p.register(sk.fileno(), select.POLLIN) |
97 | fds = p.poll(timeout) |
98 | if (sk.fileno(), select.POLLIN) in fds: |
99 | break |
100 | else: |
101 | raise unreachable(nameserver) |
102 | ret = sk.recv(65536) |
103 | sk.close() |
104 | try: |
105 | resp = proto.decodepacket(ret) |
106 | except proto.malformedpacket, inst: |
107 | raise error(str(inst)) |
108 | if resp.qid != packet.qid: |
109 | raise error("got response with wrong qid(?!)") |
110 | if "resp" not in resp.flags: |
111 | raise error("got query in response") |
112 | if resp.rescode != 0: |
113 | if resp.rescode == proto.SERVFAIL: |
114 | raise servfail() |
115 | if resp.rescode == proto.NXDOMAIN: |
116 | return resp |
117 | raise error("non-successful response (" + str(resp.rescode) + ")") |
118 | if recurse: |
119 | resolvecnames(resp, cnameres) |
120 | if not recurse or resp.hasanswers(): |
121 | return resp |
122 | if not resp.hasanswers() and "auth" in resp.flags: |
123 | return resp |
124 | if hops > 30: |
125 | raise error("too many levels deep") |
126 | for rr in resp.aulist: |
127 | if verbose: |
128 | print (hops * " ") + "Checking " + str(rr) |
129 | if rr.head.istype("NS"): |
130 | if verbose: |
131 | print (hops * " ") + "Will try " + str(rr) |
132 | ai = extractaddrinfo(resp, rr.data["nsname"]) |
133 | if len(ai) == 0: |
134 | if verbose: |
135 | print (hops * " ") + "Resolving nameservers for " + str(rr.data["nsname"]) |
136 | resolveadditional(resp, rr) |
137 | ai = extractaddrinfo(resp, rr.data["nsname"]) |
138 | for ns in ai: |
139 | ns += (53,) |
140 | if ns in visited: |
141 | if verbose: |
142 | print (hops * " ") + "Will not try " + str(ns) + " again" |
143 | continue |
144 | if verbose: |
145 | print (hops * " ") + "Trying " + str(ns) |
146 | try: |
147 | resp2 = resolve(packet, ns, recurse, retries, timeout, hops + 1, verbose = verbose, visited = visited) |
148 | except unreachable: |
149 | if verbose: |
150 | print (hops * " ") + "Could not reach " + str(ns) |
151 | continue |
152 | if verbose: |
153 | if resp2 is None: |
154 | print (hops * " ") + "Got None" |
155 | else: |
156 | if "auth" in resp2.flags: |
157 | austr = "Auth" |
158 | else: |
159 | austr = "Nonauth" |
160 | print (hops * " ") + "Got " + str(resp2.hasanswers()) + " (" + austr + ")" |
161 | if resp2 is not None and resp2.hasanswers(): |
162 | return resp2 |
163 | if resp2 is not None and not resp2.hasanswers() and "auth" in resp2.flags: |
164 | return resp2 |
165 | return None |
166 | |
167 | class resolver: |
168 | def __init__(self, nameserver, recurse, nsrecurse = True, retries = 3, timeout = 2000, verbose = False): |
169 | self.nameserver = nameserver |
170 | self.recurse = recurse |
171 | self.nsrecurse = nsrecurse |
172 | self.retries = retries |
173 | self.timeout = timeout |
174 | self.verbose = verbose |
175 | |
176 | def resolve(self, packet): |
177 | return resolve(packet, self.nameserver, self.recurse, self.retries, self.timeout, verbose = self.verbose) |
178 | |
179 | def squery(self, name, rtype): |
180 | packet = proto.packet() |
181 | try: |
182 | if self.nsrecurse: packet.setflags(["recurse"]) |
183 | except AttributeError: pass |
184 | packet.addq(rec.rrhead(name, rtype)) |
185 | return self.resolve(packet) |
186 | |
187 | class multiresolver(resolver): |
188 | def __init__(self, resolvers): |
189 | self.rl = [{"res": res, "qs": []} for res in resolvers] |
190 | self.lastclean = int(time.time()) |
191 | |
192 | def clean(self): |
193 | now = int(time.time()) |
194 | if now - self.lastclean < 60: |
195 | return |
196 | self.lastclean = now |
197 | for r in self.rl: |
198 | nl = [] |
199 | for q in r["qs"]: |
200 | if now - q["time"] < 1800: |
201 | nl += [q] |
202 | r["qs"] = nl |
203 | |
204 | def resolve(self, packet): |
205 | self.clean() |
206 | l = [] |
207 | ts = 0 |
208 | for r in self.rl: |
209 | if len(r["qs"]) < 1: |
210 | score = 1.0 |
211 | else: |
212 | score = float(sum([q["s"] for q in r["qs"]])) / len(r["qs"]) |
213 | l += [(score, r)] |
214 | ts += score |
215 | c = random.random() * ts |
216 | for score, r in l: |
217 | c -= score |
218 | if c <= 0: |
219 | break |
220 | else: |
221 | assert(False) |
222 | try: |
223 | res = r["res"].resolve(packet) |
224 | except error: |
225 | r["qs"] = r["qs"][:10] + [{"time": int(time.time()), "s": 0}] |
226 | raise |
227 | r["qs"] = r["qs"][:10] + [{"time": int(time.time()), "s": 1}] |
228 | return res |
229 | |
230 | class sysresolver(resolver): |
231 | def __init__(self, conffile = "/etc/resolv.conf"): |
232 | nslist = [] |
233 | prelist = [] |
234 | a = open(conffile, "r") |
235 | for line in (l.strip() for l in a): |
236 | p = line.find(" ") |
237 | if p >= 0: |
238 | c = line[:p] |
239 | line = line[p + 1:] |
240 | if c == "nameserver": |
241 | try: |
242 | socket.inet_pton(socket.AF_INET, line) |
243 | except socket.error: pass |
244 | else: |
245 | nslist += [(socket.AF_INET, line, 53)] |
246 | try: |
247 | socket.inet_pton(socket.AF_INET6, line) |
248 | except socket.error: pass |
249 | else: |
250 | nslist += [(socket.AF_INET6, line, 53)] |
251 | if c == "domain" or c == "search": # How do these differ? |
252 | prelist += line.split() |
253 | a.close() |
254 | rl = [] |
255 | for ns in nslist: |
256 | rl += [resolver(ns, False, True)] |
257 | self.resolver = multiresolver(rl) |
258 | self.prelist = [] |
259 | for prefix in prelist: |
260 | pp = dn.fromstring(prefix) |
261 | pp.rooted = True |
262 | self.prelist += [pp] |
263 | |
264 | def resolve(self, packet): |
265 | res = self.resolver.resolve(packet) |
266 | return res |
267 | |
268 | def squery(self, name, rtype): |
269 | if type(name) == str: |
270 | name = dn.fromstring(name) |
271 | if not name.rooted: |
272 | namelist = [name + prefix for prefix in self.prelist] + [name + dn.fromstring(".")] |
273 | else: |
274 | namelist = [name] |
275 | for name in namelist: |
276 | packet = proto.packet() |
277 | packet.setflags(["recurse"]) |
278 | packet.addq(rec.rrhead(name, rtype)) |
279 | res = self.resolve(packet) |
280 | if res.rescode == 0: |
281 | break |
282 | return res |
283 | |
284 | sysres = sysresolver() |
285 | rootresolvers = {"a": resolver((socket.AF_INET, "198.41.0.4", 53), True, False), |
286 | "b": resolver((socket.AF_INET, "192.228.79.201", 53), True, False), |
287 | "c": resolver((socket.AF_INET, "192.33.4.12", 53), True, False), |
288 | "d": resolver((socket.AF_INET, "128.8.10.90", 53), True, False), |
289 | "e": resolver((socket.AF_INET, "192.203.230.10", 53), True, False), |
290 | "f": resolver((socket.AF_INET, "192.5.5.241", 53), True, False), |
291 | "g": resolver((socket.AF_INET, "192.112.36.4", 53), True, False), |
292 | "h": resolver((socket.AF_INET, "128.63.2.53", 53), True, False), |
293 | "i": resolver((socket.AF_INET, "192.36.148.17", 53), True, False), |
294 | "j": resolver((socket.AF_INET, "192.58.128.30", 53), True, False), |
295 | "k": resolver((socket.AF_INET, "193.0.14.129", 53), True, False), |
296 | "l": resolver((socket.AF_INET, "198.32.64.12", 53), True, False), |
297 | "m": resolver((socket.AF_INET, "202.12.27.33", 53), True, False) |
298 | } |
299 | rootres = multiresolver(rootresolvers.values()) |
300 | |
301 | default = sysres |