| 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 |