Class Dnsruby::RR::TSIG
In: lib/Dnsruby/resource/TSIG.rb
Parent: RR
ResolvError EncodeError OtherResolvError ServFail FormErr DecodeError NXRRSet YXDomain NotImp NXDomain VerifyError NotAuth YXRRSet NotZone Refused TsigError Message Update CodeMapper Types MetaTypes QTypes Nsec3HashAlgorithms Algorithms OpCode Classes ExtendedRCode RCode Modes Comparable Name RRSet Resolver SingleResolver StandardError TimeoutError ResolvTimeout DNS Dnssec Hosts SelectThread\n[lib/Dnsruby/select_thread.rb\nlib/Dnsruby/select_thread.rb.michael.rb] Recursor IPv6 IPv4 ZoneTransfer MessageDecoder MessageEncoder Question Header TheLog RR\n[lib/Dnsruby/resource/A.rb\nlib/Dnsruby/resource/AAAA.rb\nlib/Dnsruby/resource/AFSDB.rb\nlib/Dnsruby/resource/CERT.rb\nlib/Dnsruby/resource/DLV.rb\nlib/Dnsruby/resource/DNSKEY.rb\nlib/Dnsruby/resource/DS.rb\nlib/Dnsruby/resource/HINFO.rb\nlib/Dnsruby/resource/IN.rb\nlib/Dnsruby/resource/ISDN.rb\nlib/Dnsruby/resource/LOC.rb\nlib/Dnsruby/resource/MINFO.rb\nlib/Dnsruby/resource/MX.rb\nlib/Dnsruby/resource/NAPTR.rb\nlib/Dnsruby/resource/NSAP.rb\nlib/Dnsruby/resource/NSEC.rb\nlib/Dnsruby/resource/NSEC3.rb\nlib/Dnsruby/resource/NSEC3PARAM.rb\nlib/Dnsruby/resource/OPT.rb\nlib/Dnsruby/resource/PX.rb\nlib/Dnsruby/resource/RP.rb\nlib/Dnsruby/resource/RRSIG.rb\nlib/Dnsruby/resource/RT.rb\nlib/Dnsruby/resource/SOA.rb\nlib/Dnsruby/resource/SPF.rb\nlib/Dnsruby/resource/SRV.rb\nlib/Dnsruby/resource/TKEY.rb\nlib/Dnsruby/resource/TSIG.rb\nlib/Dnsruby/resource/TXT.rb\nlib/Dnsruby/resource/X25.rb\nlib/Dnsruby/resource/domain_name.rb\nlib/Dnsruby/resource/generic.rb\nlib/Dnsruby/resource/resource.rb] ValidatorThread PacketSender ResolverRuby Config KeyCache Cache SingleVerifier Resolv Iana lib/Dnsruby/DNS.rb lib/Dnsruby/dnssec.rb lib/Dnsruby/Hosts.rb lib/Dnsruby/select_thread.rb.michael.rb lib/Dnsruby/Recursor.rb lib/Dnsruby/update.rb lib/Dnsruby/ipv6.rb lib/Dnsruby/ipv4.rb lib/Dnsruby/code_mapper.rb lib/Dnsruby/zone_transfer.rb lib/Dnsruby/message.rb lib/Dnsruby/TheLog.rb lib/Dnsruby/resource/resource.rb lib/Dnsruby/validator_thread.rb lib/Dnsruby/PacketSender.rb lib/Dnsruby/Resolver.rb lib/Dnsruby/Config.rb lib/Dnsruby/key_cache.rb lib/Dnsruby/Cache.rb lib/Dnsruby/single_verifier.rb lib/Dnsruby/SingleResolver.rb lib/Dnsruby/name.rb lib/dnsruby.rb lib/Dnsruby/resource/TKEY.rb lib/Dnsruby/iana_ports.rb Dnsruby dot/m_56_0.png

TSIG implements RFC2845.

"This protocol allows for transaction level authentication using shared secrets and one way hashing. It can be used to authenticate dynamic updates as coming from an approved client, or to authenticate responses as coming from an approved recursive name server."

A Dnsruby::RR::TSIG can represent the data present in a TSIG RR. However, it can also represent the data (specified in RFC2845) used to sign or verify a DNS message.

Example code :

    res = Dnsruby::Resolver.new("ns0.validation-test-servers.nominet.org.uk")

    # Now configure the resolver with the TSIG key for signing/verifying
    KEY_NAME="rubytsig"
    KEY = "8n6gugn4aJ7MazyNlMccGKH1WxD2B3UvN/O/RA6iBupO2/03u9CTa3Ewz3gBWTSBCH3crY4Kk+tigNdeJBAvrw=="
    res.tsig=KEY_NAME, KEY

    update = Dnsruby::Update.new("validation-test-servers.nominet.org.uk")
    # Generate update record name, and test it has been made. Then delete it and check it has been deleted
    update_name = generate_update_name
    update.absent(update_name)
    update.add(update_name, 'TXT', 100, "test signed update")

    # Resolver will automatically sign message and verify response
    response = res.send_message(update)
    assert(response.verified?) # Check that the response has been verified

Methods

Constants

HMAC_MD5 = Name.create("HMAC-MD5.SIG-ALG.REG.INT.")
HMAC_SHA1 = Name.create("hmac-sha1.")
HMAC_SHA256 = Name.create("hmac-sha256.")
DEFAULT_FUDGE = 300
DEFAULT_ALGORITHM = HMAC_MD5
TypeValue = Types::TSIG #:nodoc: all

Attributes

algorithm  [R]  Gets or sets the domain name that specifies the name of the algorithm. The only algorithms currently supported are hmac-md5 and hmac-sha1.
    rr.algorithm=(algorithm_name)
    print "algorithm = ", rr.algorithm, "\n"
error  [RW]  Returns the RCODE covering TSIG processing. Common values are NOERROR, BADSIG, BADKEY, and BADTIME. See RFC 2845 for details.
    print "error = ", rr.error, "\n"
fudge  [R]  Gets or sets the "fudge", i.e., the seconds of error permitted in the signing time.

The default fudge is 300 seconds.

    rr.fudge=(60)
    print "fudge = ", rr.fudge, "\n"
key  [RW]  Stores the secret key used for signing/verifying messages.
mac  [RW]  Returns the message authentication code (MAC) as a string of hex characters. The programmer must call a Net::DNS::Packet object‘s data method before this will return anything meaningful.
    print "MAC = ", rr.mac, "\n"
mac_size  [RW]  Returns the number of octets in the message authentication code (MAC). The programmer must call a Net::DNS::Packet object‘s data method before this will return anything meaningful.
    print "MAC size = ", rr.mac_size, "\n"
original_id  [RW]  Gets or sets the original message ID.
    rr.original_id(12345)
    print "original ID = ", rr.original_id, "\n"
other_data  [RW]  Returns the Other Data. This field should be empty unless the error is BADTIME, in which case it will contain the server‘s time as the number of seconds since 1 Jan 1970 00:00:00 UTC.
    print "other data = ", rr.other_data, "\n"
other_size  [RW]  Returns the length of the Other Data. Should be zero unless the error is BADTIME.
    print "other len = ", rr.other_size, "\n"
time_signed  [RW]  Gets or sets the signing time as the number of seconds since 1 Jan 1970 00:00:00 UTC.

The default signing time is the current time.

    rr.time_signed=(time)
    print "time signed = ", rr.time_signed, "\n"

Public Instance methods

Set the algorithm to use to generate the HMAC Supported values are :

  • hmac-md5
  • hmac-sha1
  • hmac-sha256

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 512
512:       def algorithm=(alg)
513:         if (alg.class == String)
514:           if (alg.downcase=="hmac-md5")
515:             @algorithm = HMAC_MD5;
516:           elsif (alg.downcase=="hmac-sha1")
517:             @algorithm = HMAC_SHA1;
518:           elsif (alg.downcase=="hmac-sha256")
519:             @algorithm = HMAC_SHA256;
520:           else
521:             raise ArgumentError.new("Invalid TSIG algorithm")
522:           end
523:         elsif (alg.class == Name)
524:           if (alg!=HMAC_MD5 && alg!=HMAC_SHA1 && alg!=HMAC_SHA256)
525:             raise ArgumentException.new("Invalid TSIG algorithm")
526:           end
527:           @algorithm=alg
528:         else
529:           raise ArgumentError.new("#{alg.class} not valid type for Dnsruby::RR::TSIG#algorithm=  - use String or Name")
530:         end
531:         Dnsruby.log.debug{"Using #{@algorithm.to_s} algorithm"}
532:       end

Generates a TSIG record and adds it to the message. Takes an optional original_request argument for the case where this is a response to a query (RFC2845 3.4.1)

Message#tsigstate will be set to :Signed.

[Source]

    # File lib/Dnsruby/resource/TSIG.rb, line 67
67:       def apply(message, original_request=nil)
68:         if (!message.signed?)
69:           tsig_rr = generate(message, original_request)
70:           message.add_additional(tsig_rr)
71:           message.tsigstate = :Signed
72:           @query = message
73:           tsig_rr.query = message
74:         end
75:       end

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 143
143:       def calculate_mac(algorithm, data)
144:         mac=nil
145:         key = @key.gsub(" ", "")
146:  #       key = Base64::decode64(key)

147:         key = key.unpack("m*")[0]
148:         if (algorithm.to_s.downcase == HMAC_MD5.to_s.downcase)
149:           mac = OpenSSL::HMAC.digest(OpenSSL::Digest::MD5.new, key, data)
150:         elsif (algorithm == HMAC_SHA1)
151:           mac = OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, key, data)
152:         elsif (algorithm == HMAC_SHA256)
153:           mac = OpenSSL::HMAC.digest(OpenSSL::Digest::SHA256.new, key, data)
154:         else
155:           # Should we allow client to pass in their own signing function?

156:           raise VerifyError.new("Algorithm #{algorithm} unsupported by TSIG")
157:         end
158:         return mac
159:       end

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 534
534:       def fudge=(f)
535:         if (f < 0 || f > 0x7FFF)
536:           @fudge = DEFAULT_FUDGE
537:         else
538:           @fudge = f
539:         end
540:       end

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 460
460:       def init_defaults
461:         # @TODO@ Have new() method which takes key_name and key?

462:         @algorithm   = DEFAULT_ALGORITHM
463:         @fudge       = DEFAULT_FUDGE
464:         @mac_size    = 0
465:         @mac         = ""
466:         @original_id = rand(65536)
467:         @error       = 0
468:         @other_size   = 0
469:         @other_data  = ""
470:         @time_signed = nil
471:         @buf = nil
472:         
473:         # RFC 2845 Section 2.3

474:         @klass = "ANY"
475:         
476:         @ttl = 0 # RFC 2845 Section 2.3

477:       end

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 483
483:       def name=(n)
484:         if (n.instance_of?String)
485:           n = Name.create(n)
486:         end
487:         if (!n.absolute?)
488:           @name = Name.create(n.to_s + ".")
489:         else 
490:           @name = n
491:         end
492:       end

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 542
542:       def rdata_to_string        
543:         rdatastr=""
544:         if (@algorithm!=nil)
545:           error = @error
546:           error = "UNDEFINED" unless error!=nil
547:           rdatastr = "#{@original_id} #{@time_signed} #{@algorithm}. #{error}";
548:           if (@other_size > 0 && @other_data!=nil)
549:             rdatastr += " #{@other_data}"
550:           end
551:           rdatastr += " " + mac.unpack("H*").to_s
552:         end
553:         
554:         return rdatastr
555:       end

Verify a response. This method will be called by Dnsruby::SingleResolver before passing a response to the client code. The TSIG record will be removed from packet before passing to client, and the Message#tsigstate and Message#tsigerror will be set accordingly. Message#tsigstate will be set to one of :

  • :Failed
  • :Verified

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 185
185:       def verify(query, response, response_bytes, buf="")
186:         #        4.6. Client processing of answer

187:         #

188:         #   When a client receives a response from a server and expects to see a

189:         #   TSIG, it first checks if the TSIG RR is present in the response.

190:         #   Otherwise, the response is treated as having a format error and

191:         #   discarded.  The client then extracts the TSIG, adjusts the ARCOUNT,

192:         #   and calculates the keyed digest in the same way as the server.  If

193:         #   the TSIG does not validate, that response MUST be discarded, unless

194:         #   the RCODE is 9 (NOTAUTH), in which case the client SHOULD attempt to

195:         #   verify the response as if it were a TSIG Error response, as specified

196:         #   in [4.3].  A message containing an unsigned TSIG record or a TSIG

197:         #   record which fails verification SHOULD not be considered an

198:         #   acceptable response; the client SHOULD log an error and continue to

199:         #   wait for a signed response until the request times out.

200: 
201:         # So, this verify method should simply remove the TSIG RR and calculate

202:         # the MAC (using original request MAC if required).

203:         # Should set tsigstate on packet appropriately, and return error.

204:         # Side effect is packet is stripped of TSIG.

205:         # Resolver (or client) can then decide what to do...

206: 
207:         msg_tsig_rr = response.tsig
208:         if (!verify_common(response))
209:           return false
210:         end
211: 
212:         new_msg_tsig_rr = generate(response, query, buf, response_bytes, msg_tsig_rr)
213:         
214:         if (msg_tsig_rr.mac == new_msg_tsig_rr.mac)
215:           response.tsigstate = :Verified
216:           response.tsigerror = RCode.NOERROR
217:           return true
218:         else
219:           response.tsigstate = :Failed
220:           response.tsigerror = RCode.BADSIG
221:           return false
222:         end
223:       end

Checks TSIG signatures across sessions of multiple DNS envelopes. This method is called each time a new envelope comes in. The envelope is checked - if a TSIG is present, them the stream so far is verified, and the response#tsigstate set to :Verified. If a TSIG is not present, and does not need to be present, then the message is added to the digest stream and the response#tsigstate is set to :Intermediate. If there is an error with the TSIG verification, then the response#tsigstate is set to :Failed. Like verify, this method will only be called by the Dnsruby::SingleResolver class. Client code need not call this method directly.

[Source]

     # File lib/Dnsruby/resource/TSIG.rb, line 273
273:       def verify_envelope(response, response_bytes)
274:         #RFC2845 Section 4.4

275:         #-----

276:         #A DNS TCP session can include multiple DNS envelopes.  This is, for

277:         #example, commonly used by zone transfer.  Using TSIG on such a

278:         #connection can protect the connection from hijacking and provide data

279:         #integrity.  The TSIG MUST be included on the first and last DNS

280:         #envelopes.  It can be optionally placed on any intermediary

281:         #envelopes.  It is expensive to include it on every envelopes, but it

282:         #MUST be placed on at least every 100'th envelope.  The first envelope

283:         #is processed as a standard answer, and subsequent messages have the

284:         #following digest components:

285:         #

286:         #*   Prior Digest (running)

287:         #*   DNS Messages (any unsigned messages since the last TSIG)

288:         #*   TSIG Timers (current message)

289:         #

290:         #This allows the client to rapidly detect when the session has been

291:         #altered; at which point it can close the connection and retry.  If a

292:         #client TSIG verification fails, the client MUST close the connection.

293:         #If the client does not receive TSIG records frequently enough (as

294:         #specified above) it SHOULD assume the connection has been hijacked

295:         #and it SHOULD close the connection.  The client SHOULD treat this the

296:         #same way as they would any other interrupted transfer (although the

297:         #exact behavior is not specified).

298:         #-----

299:         #

300:         # Each time a new envelope comes in, this method is called on the QUERY TSIG RR.

301:         # It will set the response tsigstate to :Verified :Intermediate or :Failed

302:         # as appropriate.

303:         
304:         # Keep digest going of messages as they come in (and mark them intermediate)

305:         # When TSIG comes in, work out what key should be and check. If OK, mark 

306:         # verified. Can reset digest then.

307:         if (!@buf)
308:           @num_envelopes = 0
309:           @last_signed = 0
310:         end
311:         @num_envelopes += 1
312:         if (!response.tsig)
313:           if ((@num_envelopes > 1) && (@num_envelopes - @last_signed < 100))
314:             Dnsruby.log.debug("Receiving intermediate envelope in TSIG TCP session")
315:             response.tsigstate = :Intermediate
316:             response.tsigerror = RCode.NOERROR
317:             @buf = @buf + response_bytes
318:             return
319:           else
320:             response.tsigstate = :Failed
321:             Dnsruby.log.error("Expecting signed packet")
322:             return false
323:           end
324:         end
325:         @last_signed = @num_envelopes
326:         
327:         # We have a TSIG - process it!

328:         tsig = response.tsig
329:         if (@num_envelopes == 1)
330:           Dnsruby.log.debug("First response in TSIG TCP session - verifying normally")
331:           # Process it as a standard answer

332:           ok = verify(@query, response, response_bytes)
333:           if (ok)
334:             mac_bytes = MessageEncoder.new {|m|
335:               m.put_pack('n', tsig.mac_size)
336:               m.put_bytes(tsig.mac)
337:             }.to_s
338:             @buf = mac_bytes
339:           end
340:           return ok
341:         end
342:         Dnsruby.log.debug("Processing TSIG on TSIG TCP session")
343: 
344:         if (!verify_common(response))
345:           return false
346:         end
347:         
348:         # Now add the current message data - remember to frig the arcount

349:         response_bytes = Header.decrement_arcount_encoded(response_bytes)
350:         @buf += response_bytes[0, response.tsigstart]
351:         
352:         # Let's add the timers

353:         timers_data = MessageEncoder.new { |msg|
354:           time_high = (tsig.time_signed >> 32)
355:           time_low = (tsig.time_signed & 0xFFFFFFFF)
356:           msg.put_pack('nN', time_high, time_low)
357:           msg.put_pack('n', tsig.fudge)
358:         }.to_s
359:         @buf += timers_data
360:         
361:         mac = calculate_mac(tsig.algorithm, @buf)
362: 
363:         if (mac != tsig.mac)
364:           Dnsruby.log.error("TSIG Verify error on TSIG TCP session")
365:           response.tsigstate = :Failed
366:           return false
367:         end
368:         mac_bytes = MessageEncoder.new {|m|
369:           m.put_pack('n', mac.length)
370:           m.put_bytes(mac)
371:         }.to_s
372:         @buf=mac_bytes
373: 
374:         response.tsigstate = :Verified
375:         response.tsigerror = RCode.NOERROR
376:         return true
377:       end

[Validate]