swede

   1 #!/usr/bin/python
   2
   3 # swede - A tool to create DANE/TLSA records.
   4 # This tool is really simple and not foolproof, it doesn't check the CN in the
   5 # Subject field of the certificate. It also doesn't check if the supplied
   6 # certificate is a CA certificate if usage 1 is specified (or any other
   7 # checking for that matter).
   8 #
   9 # Usage is explained when running this program with --help
  10 #
  11 # This tool is loosly based on the dane tool in the sshfp package by Paul
  12 # Wouters and Christopher Olah from xelerance.com.
  13 #
  14 # Copyright Pieter Lexis (pieter.lexis@os3.nl)
  15 #
  16 # License: GNU GENERAL PUBLIC LICENSE Version 2 or later
  17
  18 import sys
  19 import os
  20 import socket
  21 import unbound
  22 import re
  23 from M2Crypto import X509, SSL
  24 from binascii import a2b_hex, b2a_hex
  25 from hashlib import sha256, sha512
  26 from ipaddr import IPv4Address, IPv6Address
  27
  28
  29 def genTLSA(hostname, protocol, port, certificate, output='generic', usage=1, selector=0, mtype=1):
  30         """This function generates a TLSARecord object using the data passed in the parameters,
  31         it then validates the record and returns the RR as a string.
  32         """
  33         # check if valid vars were passed
  34         if hostname[-1] != '.':
  35                 hostname += '.'
  36
  37         certificate = loadCert(certificate)
  38         if not certificate:
  39                 raise Exception('Cannot load certificate from disk')
  40
  41         # Create the record without a certificate
  42         if port == '*':
  43                 record = TLSARecord(name='%s._%s.%s'%(port,protocol,hostname), usage=usage, selector=selector, mtype=mtype, cert ='')
  44         else:
  45                 record = TLSARecord(name='_%s._%s.%s'%(port,protocol,hostname), usage=usage, selector=selector, mtype=mtype, cert ='')
  46         # Check if the record is valid
  47         if record.isValid:
  48                 if record.selector == 0:
  49                         # Hash the Full certificate
  50                         record.cert = getHash(certificate, record.mtype)
  51                 else:
  52                         # Hash only the SubjectPublicKeyInfo
  53                         record.cert = getHash(certificate.get_pubkey(), record.mtype)
  54
  55         record.isValid(raiseException=True)
  56
  57         if output == 'generic':
  58                 return record.getRecord(generic=True)
  59         return record.getRecord()
  60
  61 def getA(hostname, secure=True):
  62         """Gets a list of A records for hostname, returns a list of ARecords"""
  63         try:
  64                 records = getRecords(hostname, rrtype='A', secure=secure)
  65         except InsecureLookupException, e:
  66                 print str(e)
  67                 sys.exit(1)
  68         except DNSLookupError, e:
  69                 print 'Unable to resolve %s: %s' % (hostname, str(e))
  70                 sys.exit(1)
  71         ret = []
  72         for record in records:
  73                 ret.append(ARecord(hostname, str(IPv4Address(int(b2a_hex(record),16)))))
  74         return ret
  75
  76 def getAAAA(hostname, secure=True):
  77         """Gets a list of A records for hostname, returns a list of AAAARecords"""
  78         try:
  79                 records = getRecords(hostname, rrtype='AAAA', secure=secure)
  80         except InsecureLookupException, e:
  81                 print str(e)
  82                 sys.exit(1)
  83         except DNSLookupError, e:
  84                 print 'Unable to resolve %s: %s' % (hostname, str(e))
  85                 sys.exit(1)
  86         ret = []
  87         for record in records:
  88                 ret.append(AAAARecord(hostname, str(IPv6Address(int(b2a_hex(record),16)))))
  89         return ret
  90
  91 def getVerificationErrorReason(num):
  92         """This function returns the name of the X509 Error based on int(num)
  93         """
  94         # These were taken from the M2Crypto.m2 code
  95         return {
  96 50: "X509_V_ERR_APPLICATION_VERIFICATION",
  97 22: "X509_V_ERR_CERT_CHAIN_TOO_LONG",
  98 10: "X509_V_ERR_CERT_HAS_EXPIRED",
  99 9:  "X509_V_ERR_CERT_NOT_YET_VALID",
 100 28: "X509_V_ERR_CERT_REJECTED",
 101 23: "X509_V_ERR_CERT_REVOKED",
 102 7:  "X509_V_ERR_CERT_SIGNATURE_FAILURE",
 103 27: "X509_V_ERR_CERT_UNTRUSTED",
 104 12: "X509_V_ERR_CRL_HAS_EXPIRED",
 105 11: "X509_V_ERR_CRL_NOT_YET_VALID",
 106 8:  "X509_V_ERR_CRL_SIGNATURE_FAILURE",
 107 18: "X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT",
 108 14: "X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD",
 109 13: "X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD",
 110 15: "X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD",
 111 16: "X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD",
 112 24: "X509_V_ERR_INVALID_CA",
 113 26: "X509_V_ERR_INVALID_PURPOSE",
 114 17: "X509_V_ERR_OUT_OF_MEM",
 115 25: "X509_V_ERR_PATH_LENGTH_EXCEEDED",
 116 19: "X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN",
 117 6:  "X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY",
 118 4:  "X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE",
 119 5:  "X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE",
 120 3:  "X509_V_ERR_UNABLE_TO_GET_CRL",
 121 2:  "X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT",
 122 20: "X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY",
 123 21: "X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE",
 124 0:  "X509_V_OK"}[int(num)]
 125
 126 def getRecords(hostname, rrtype='A', secure=True):
 127         """Do a lookup of a name and a rrtype, returns a list of binary coded strings. Only queries for rr_class IN."""
 128         global resolvconf
 129         ctx = unbound.ub_ctx()
 130         ctx.add_ta_file('root.key')
 131         ctx.set_option("dlv-anchor-file:", "dlv.isc.org.key")
 132         # Use the local cache
 133         if resolvconf and os.path.isfile(resolvconf):
 134                 ctx.resolvconf(resolvconf)
 135
 136         if type(rrtype) == str:
 137                 if 'RR_TYPE_' + rrtype in dir(unbound):
 138                         rrtype = getattr(unbound, 'RR_TYPE_' + rrtype)
 139                 else:
 140                         raise Exception('Error: unknown RR TYPE: %s.' % rrtype)
 141         elif type(rrtype) != int:
 142                 raise Exception('Error: rrtype in wrong format, neither int nor str.')
 143
 144         status, result = ctx.resolve(hostname, rrtype=rrtype)
 145         if status == 0 and result.havedata:
 146                 if not result.secure:
 147                         if secure:
 148                                 # The data is insecure and a secure lookup was requested
 149                                 raise InsecureLookupException('Error: query data not secure and secure data requested, unable to continue')
 150                         else:
 151                                 print >> sys.stderr, 'Warning: query data is not secure.'
 152                 # If we are here the data was either secure or insecure data is accepted
 153                 return result.data.raw
 154         else:
 155                 raise DNSLookupError('Unsuccesful lookup or no data returned for rrtype %s.' % rrtype)
 156
 157 def getHash(certificate, mtype):
 158         """Hashes the certificate based on the mtype.
 159         The certificate should be an M2Crypto.X509.X509 object (or the result of the get_pubkey() function on said object)
 160         """
 161         certificate = certificate.as_der()
 162         if mtype == 0:
 163                 return b2a_hex(certificate)
 164         elif mtype == 1:
 165                 return sha256(certificate).hexdigest()
 166         elif mtype == 2:
 167                 return sha512(certificate).hexdigest()
 168         else:
 169                 raise Exception('mtype should be 0,1,2')
 170
 171 def getTLSA(hostname, port=443, protocol='tcp', secure=True):
 172         """
 173         This function tries to do a secure lookup of the TLSA record.
 174         At the moment it requests the TYPE52 record and parses it into a 'valid' TLSA record
 175         It returns a list of TLSARecord objects
 176         """
 177         if hostname[-1] != '.':
 178                 hostname += '.'
 179
 180         if not protocol.lower() in ['tcp', 'udp', 'sctp']:
 181                 raise Exception('Error: unknown protocol: %s. Should be one of tcp, udp or sctp' % protocol)
 182         try:
 183                 if port == '*':
 184                         records = getRecords('*._%s.%s' % (protocol.lower(), hostname), rrtype=52, secure=secure)
 185                 else:
 186                         records = getRecords('_%s._%s.%s' % (port, protocol.lower(), hostname), rrtype=52, secure=secure)
 187         except InsecureLookupException, e:
 188                 print str(e)
 189                 sys.exit(1)
 190         except DNSLookupError, e:
 191                 print 'Unable to resolve %s: %s' % (hostname, str(e))
 192                 sys.exit(1)
 193         ret = []
 194         for record in records:
 195                 hexdata = b2a_hex(record)
 196                 if port == '*':
 197                         ret.append(TLSARecord('*._%s.%s' % (protocol.lower(), hostname), int(hexdata[0:2],16), int(hexdata[2:4],16), int(hexdata[4:6],16), hexdata[6:]))
 198                 else:
 199                         ret.append(TLSARecord('_%s._%s.%s' % (port, protocol.lower(), hostname), int(hexdata[0:2],16), int(hexdata[2:4],16), int(hexdata[4:6],16), hexdata[6:]))
 200         return ret
 201
 202 def loadCert(certificate):
 203         """Returns an M2Crypto.X509.X509 object"""
 204         if isinstance(certificate, X509.X509):
 205                 # nothing to be done :-)
 206                 return certificate
 207         try:
 208                 # Maybe we were passed a path
 209                 return X509.load_cert(certificate)
 210         except:
 211                 # Can't load the cert
 212                 raise Exception('Unable to load certificate %s.' % certificate)
 213
 214 def verifyCertMatch(record, cert):
 215         """
 216         Verify the certificate with the record.
 217         record should be a TLSARecord and cert should be a M2Crypto.X509.X509
 218         """
 219         if not isinstance(cert, X509.X509):
 220                 return
 221         if not isinstance(record, TLSARecord):
 222                 return
 223
 224         if record.selector == 1:
 225                 certhash = getHash(cert.get_pubkey(), record.mtype)
 226         else:
 227                 certhash = getHash(cert, record.mtype)
 228
 229         if not certhash:
 230                 return
 231
 232         if certhash == record.cert:
 233                 return True
 234         else:
 235                 return False
 236
 237 class TLSARecord:
 238         """When instanciated, this class contains all the fields of a TLSA record.
 239         """
 240         def __init__(self, name, usage, selector, mtype, cert):
 241                 """name is the name of the RR in the format: /^(_\d{1,5}|\*)\._(tcp|udp|sctp)\.([a-z0-9]*\.){2,}$/
 242                 usage, selector and mtype should be an integer
 243                 cert should be a hexidecimal string representing the certificate to be matched field
 244                 """
 245                 try:
 246                         self.rrtype = 52    # TLSA per https://www.iana.org/assignments/dns-parameters
 247                         self.rrclass = 1    # IN
 248                         self.name = str(name)
 249                         self.usage = int(usage)
 250                         self.selector = int(selector)
 251                         self.mtype = int(mtype)
 252                         self.cert = str(cert)
 253                 except:
 254                         raise Exception('Invalid value passed, unable to create a TLSARecord')
 255
 256         def getRecord(self, generic=False):
 257                 """Returns the RR string of this TLSARecord, either in rfc (default) or generic format"""
 258                 if generic:
 259                         return '%s IN TYPE52 \# %s %s%s%s%s' % (self.name, (len(self.cert)/2)+3 , self._toHex(self.usage), self._toHex(self.selector), self._toHex(self.mtype), self.cert)
 260                 return '%s IN TLSA %s %s %s %s' % (self.name, self.usage, self.selector, self.mtype, self.cert)
 261
 262         def _toHex(self, val):
 263                 """Helper function to create hex strings from integers"""
 264                 return "%0.2x" % val
 265
 266         def isValid(self, raiseException=False):
 267                 """Check whether all fields in the TLSA record are conforming to the spec and check if the port, protocol and name are good"""
 268                 err =[]
 269                 try:
 270                         if not 1 <= int(self.getPort()) <= 65535:
 271                                 err.append('Port %s not within correct range (1 <= port <= 65535)' % self.getPort())
 272                 except:
 273                         if self.getPort() != '*':
 274                                 err.append('Port %s not a number' % self.getPort())
 275                 if not self.usage in [0,1,2,3]:
 276                         err.append('Usage: invalid (%s is not one of 0, 1, 2 or 3)' % self.usage)
 277                 if not self.selector in [0,1]:
 278                         err.append('Selector: invalid (%s is not one of 0 or 1)' % self.selector)
 279                 if not self.mtype in [0,1,2]:
 280                         err.append('Matching Type: invalid (%s is not one of 0, 1 or 2)' % self.mtype)
 281                 if not self.isNameValid():
 282                         err.append('Name (%s) is not in the correct format: _portnumber._transportprotocol.hostname.dom.' % self.name)
 283                 # A certificate length of 0 is accepted
 284                 if self.mtype in [1,2] and len(self.cert) != 0:
 285                         if not len(self.cert) == {1:64,2:128}[self.mtype]:
 286                                 err.append('Certificate for Association: invalid (Hash length does not match hash-type in Matching Type(%s))' % {1:'SHA-256',2:'SHA-512'}[self.mtype])
 287                 if len(err) != 0:
 288                         if not raiseException:
 289                                 return False
 290                         else:
 291                                 msg = 'The TLSA record is invalid.'
 292                                 for error in err:
 293                                         msg += '\n\t%s' % error
 294                                 raise RecordValidityException(msg)
 295                 else:
 296                         return True
 297
 298         def isNameValid(self):
 299                 """Check if the name if in the correct format"""
 300                 if not re.match('^(_\d{1,5}|\*)\._(tcp|udp|sctp)\.([-a-z0-9]*\.){2,}$', self.name):
 301                         return False
 302                 return True
 303
 304         def getProtocol(self):
 305                 """Returns the protocol based on the name"""
 306                 return re.split('\.', self.name)[1][1:]
 307
 308         def getPort(self):
 309                 """Returns the port based on the name"""
 310                 if re.split('\.', self.name)[0][0] == '*':
 311                         return '*'
 312                 else:
 313                         return re.split('\.', self.name)[0][1:]
 314
 315 class ARecord:
 316         """An object representing an A Record (IPv4 address)"""
 317         def __init__(self, hostname, address):
 318                 self.rrtype = 1
 319                 self.hostname = hostname
 320                 self.address = address
 321
 322         def __str__(self):
 323                 return self.address
 324
 325         def isValid(self):
 326                 try:
 327                         IPv4Address(self.address)
 328                         return True
 329                 except:
 330                         return False
 331
 332 class AAAARecord:
 333         """An object representing an AAAA Record (IPv6 address)"""
 334         def __init__(self, hostname, address):
 335                 self.rrtype = 28
 336                 self.hostname = hostname
 337                 self.address = address
 338
 339         def __str__(self):
 340                 return self.address
 341
 342         def isValid(self):
 343                 try:
 344                         IPv6Address(self.address)
 345                         return True
 346                 except:
 347                         return False
 348
 349 # Exceptions
 350 class RecordValidityException(Exception):
 351         pass
 352
 353 class InsecureLookupException(Exception):
 354         pass
 355
 356 class DNSLookupError(Exception):
 357         pass
 358
 359 if __name__ == '__main__':
 360         import argparse
 361         # create the parser
 362         parser = argparse.ArgumentParser(description='Create and verify DANE records.', epilog='This tool has a few limitations')
 363
 364         subparsers = parser.add_subparsers(title='Functions', help='Available functions, see %(prog)s function -h for function-specific help')
 365         parser_verify = subparsers.add_parser('verify', help='Verify a TLSA record, exit 0 when all TLSA records are matched, exit 2 when a record does not match the received certificate, exit 1 on error.', epilog='Caveat: For TLSA validation, this program chases through the certificate chain offered by the server, not its local certificates.')
 366         parser_verify.set_defaults(function='verify')
 367         parser_create = subparsers.add_parser('create', help='Create a TLSA record')
 368         parser_create.set_defaults(function='create')
 369
 370         #parser.add_argument('-4', dest='ipv4', action='store_true',help='use ipv4 networking only')
 371         #parser.add_argument('-6', dest='ipv6', action='store_true',help='use ipv6 networking only')
 372         parser.add_argument('--insecure', action='store_true', default=False, help='Allow use of non-dnssec secured answers')
 373         parser.add_argument('--resolvconf', metavar='/PATH/TO/RESOLV.CONF', action='store', default='', help='Use a recursive resolver from resolv.conf')
 374         parser.add_argument('-v', '--version', action='version', version='%(prog)s v0.2', help='show version and exit')
 375         parser.add_argument('host', metavar="hostname")
 376
 377         parser_verify.add_argument('--port', '-p', action='store', default='443', help='The port, or \'*\' where running TLS is located (default: %(default)s).')
 378         parser_verify.add_argument('--protocol', action='store', choices=['tcp','udp','sctp'], default='tcp', help='The protocol the TLS service is using (default: %(default)s).')
 379         parser_verify.add_argument('--only-rr', '-o', action='store_true', help='Only verify that the TLSA resource record is correct (do not check certificate)')
 380         parser_verify.add_argument('--ca-cert', metavar='/PATH/TO/CERTSTORE', action='store', default = '/etc/ssl/certs/', help='Path to a CA certificate or a directory containing the certificates (default: %(default)s)')
 381         parser_verify.add_argument('--quiet', '-q', action='store_true', help='Only print the result of the validation')
 382
 383         parser_create.add_argument('--port', '-p', action='store', type=int, default=443, help='The port where running TLS is located (default: %(default)s).')
 384         parser_create.add_argument('--protocol', action='store', choices=['tcp','udp','sctp'], default='tcp', help='The protocol the TLS service is using (default: %(default)s).')
 385         parser_create.add_argument('--certificate', '-c', help='The certificate used for the host. If certificate is empty, the certificate will be downloaded from the server')
 386         parser_create.add_argument('--output', '-o', action='store', default='generic', choices=['generic','rfc','both'], help='The type of output. Generic (RFC 3597, TYPE52), RFC (TLSA) or both (default: %(default)s).')
 387
 388         # Usage of the certificate
 389         parser_create.add_argument('--usage', '-u', action='store', type=int, default=1, choices=[0,1,2,3], help='The Usage of the Certificate for Association. \'0\' for CA, \'1\' for End Entity, \'2\' for trust-anchor, \'3\' for ONLY End-Entity match (default: %(default)s).')
 390         parser_create.add_argument('--selector', '-s', action='store', type=int, default=0, choices=[0,1], help='The Selector for the Certificate for Association. \'0\' for Full Certificate, \'1\' for SubjectPublicKeyInfo (default: %(default)s).')
 391         parser_create.add_argument('--mtype', '-m', action='store', type=int, default=1, choices=[0,1,2], help='The Matching Type of the Certificate for Association. \'0\' for Exact match, \'1\' for SHA-256 hash, \'2\' for SHA-512 (default: %(default)s).')
 392
 393         args = parser.parse_args()
 394
 395         if args.host[-1] != '.':
 396                 args.host += '.'
 397
 398         global resolvconf
 399         if args.resolvconf:
 400                 if os.path.isfile(args.resolvconf):
 401                         resolvconf = args.resolvconf
 402                 else:
 403                         print >> sys.stdout, '%s is not a file. Unable to use it as resolv.conf' % args.resolvconf
 404                         sys.exit(1)
 405         else:
 406                 resolvconf = None
 407
 408         # not operations are fun!
 409         secure = not args.insecure
 410
 411         if args.function == 'verify':
 412                 records = getTLSA(args.host, args.port, args.protocol, secure)
 413                 if len(records) == 0:
 414                         sys.exit(1)
 415
 416                 for record in records:
 417                         pre_exit = 0
 418                         # First, check if the first three fields have correct values.
 419                         if not args.quiet:
 420                                 print 'Received the following record for name %s:' % record.name
 421                                 print '\tUsage:\t\t\t\t%d (%s)' % (record.usage, {0:'CA Constraint', 1:'End-Entity Constraint + chain to CA', 2:'Trust Anchor', 3:'End-Entity'}.get(record.usage, 'INVALID'))
 422                                 print '\tSelector:\t\t\t%d (%s)' % (record.selector, {0:'Certificate', 1:'SubjectPublicKeyInfo'}.get(record.selector, 'INVALID'))
 423                                 print '\tMatching Type:\t\t\t%d (%s)' % (record.mtype, {0:'Full Certificate', 1:'SHA-256', 2:'SHA-512'}.get(record.mtype, 'INVALID'))
 424                                 print '\tCertificate for Association:\t%s' % record.cert
 425
 426                         try:
 427                                 record.isValid(raiseException=True)
 428                         except RecordValidityException, e:
 429                                 print >> sys.stderr, 'Error: %s' % str(e)
 430                                 continue
 431                         else:
 432                                 if not args.quiet:
 433                                         print 'This record is valid (well-formed).'
 434
 435                         if args.only_rr:
 436                                 # Go to the next record
 437                                 continue
 438
 439                         # When we are here, The user also wants to verify the certificates with the record
 440                         if args.protocol != 'tcp':
 441                                 print >> sys.stderr, 'Only SSL over TCP is supported (sorry)'
 442                                 sys.exit(0)
 443
 444                         if not args.quiet:
 445                                 print 'Attempting to verify the record with the TLS service...'
 446                         addresses = getA(args.host, secure=secure) + getAAAA(args.host, secure=secure)
 447                         for address in addresses:
 448                                 if not args.quiet:
 449                                         print 'Got the following IP: %s' % str(address)
 450                                 # We do the certificate handling here, as M2Crypto keeps segfaulting when we do it in a method
 451                                 ctx = SSL.Context()
 452                                 if os.path.isfile(args.ca_cert):
 453                                         if ctx.load_verify_locations(cafile=args.ca_cert) != 1: raise Exception('No CA cert')
 454                                 elif os.path.exists(args.ca_cert):
 455                                         if ctx.load_verify_locations(capath=args.ca_cert) != 1: raise Exception('No CA certs')
 456                                 else:
 457                                         print >> sys.stderr, '%s is neither a file nor a directory, unable to continue' % args.ca_cert
 458                                         sys.exit(1)
 459                                 # Don't error when the verification fails in the SSL handshake
 460                                 ctx.set_verify(SSL.verify_none, depth=9)
 461                                 if isinstance(address, AAAARecord):
 462                                         sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
 463                                         sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 464                                 else:
 465                                         sock = None
 466                                 connection = SSL.Connection(ctx, sock=sock)
 467                                 try:
 468                                         connection.connect((str(address), int(args.port)))
 469                                 except SSL.Checker.WrongHost, e:
 470                                         # The name on the remote cert doesn't match the hostname because we connect on IP, not hostname (as we want secure lookup)
 471                                         pass
 472                                 except socket.error, e:
 473                                         print 'Cannot connect to %s: %s' % (address, str(e))
 474                                         continue
 475                                 chain = connection.get_peer_cert_chain()
 476                                 verify_result = connection.get_verify_result()
 477
 478                                 # Good, now let's verify
 479                                 if record.usage == 1: # End-host cert
 480                                         cert = chain[0]
 481                                         if verifyCertMatch(record, cert):
 482                                                 if verify_result == 0: # The cert chains to a valid CA cert according to the system-certificates
 483                                                         print 'SUCCESS (Usage 1): Certificate offered by the server matches the one mentioned in the TLSA record and chains to a valid CA certificate'
 484                                                 else:
 485                                                         print 'FAIL (Usage 1): Certificate offered by the server matches the one mentioned in the TLSA record but the following error was raised during PKIX validation: %s' % getVerificationErrorReason(verify_result)
 486                                                         if pre_exit == 0: pre_exit = 2
 487                                                 if not args.quiet: print 'The matched certificate has Subject: %s' % cert.get_subject()
 488                                         else:
 489                                                 print 'FAIL: Certificate offered by the server does not match the TLSA record'
 490                                                 if pre_exit == 0: pre_exit = 2
 491
 492                                 elif record.usage == 0: # CA constraint
 493                                         matched = False
 494                                         # Remove the first (= End-Entity cert) from the chain
 495                                         chain = chain[1:]
 496                                         for cert in chain:
 497                                                 if verifyCertMatch(record, cert):
 498                                                         matched = True
 499                                                         continue
 500                                         if matched:
 501                                                 if cert.check_ca():
 502                                                         if verify_result == 0:
 503                                                                 print 'SUCCESS (Usage 0): A certificate in the certificate chain offered by the server matches the one mentioned in the TLSA record and is a CA certificate'
 504                                                         else:
 505                                                                 print 'FAIL (Usage 0): A certificate in the certificate chain offered by the server matches the one mentioned in the TLSA record and is a CA certificate, but the following error was raised during PKIX validation:' % getVerificationErrorReason(verify_result)
 506                                                                 if pre_exit == 0: pre_exit = 2
 507                                                 else:
 508                                                         print 'FAIL (Usage 0): A certificate in the certificate chain offered by the server matches the one mentioned in the TLSA record but is not a CA certificate'
 509                                                         if pre_exit == 0: pre_exit = 2
 510                                                 if not args.quiet: print 'The matched certificate has Subject: %s' % cert.get_subject()
 511                                         else:
 512                                                 print 'FAIL (Usage 0): No certificate in the certificate chain offered by the server matches the TLSA record'
 513                                                 if pre_exit == 0: pre_exit = 2
 514
 515                                 elif record.usage == 2: # Usage 2, use the cert in the record as trust anchor
 516                                         #FIXME: doesnt comply to the spec
 517                                         matched = False
 518                                         previous_issuer = None
 519                                         for cert in chain:
 520                                                 if previous_issuer:
 521                                                         if not str(previous_issuer) == str(cert.get_subject()): # The chain cannot be valid
 522                                                                 print "FAIL: Certificates don't chain"
 523                                                                 break
 524                                                         previous_issuer = cert.get_issuer()
 525                                                 if verifyCertMatch(record, cert):
 526                                                         matched = True
 527                                                         continue
 528                                         if matched:
 529                                                 print 'SUCCESS (usage 2): A certificate in the certificate chain (including the end-entity certificate) offered by the server matches the TLSA record'
 530                                                 if not args.quiet: print 'The matched certificate has Subject: %s' % cert.get_subject()
 531                                         else:
 532                                                 print 'FAIL (usage 2): No certificate in the certificate chain (including the end-entity certificate) offered by the server matches the TLSA record'
 533                                                 if pre_exit == 0: pre_exit = 2
 534
 535                                 elif record.usage == 3: # EE cert MUST match
 536                                         if verifyCertMatch(record,chain[0]):
 537                                                 print 'SUCCESS (usage 3): The certificate offered by the server matches the TLSA record'
 538                                                 if not args.quiet: print 'The matched certificate has Subject: %s' % chain[0].get_subject()
 539                                         else:
 540                                                 print 'FAIL (usage 3): The certificate offered by the server does not match the TLSA record'
 541                                                 if pre_exit == 0: pre_exit = 2
 542
 543                                 # Cleanup, just in case
 544                                 connection.clear()
 545                                 connection.close()
 546                                 ctx.close()
 547
 548                         # END for address in addresses
 549                 # END for record in records
 550                 sys.exit(pre_exit)
 551         # END if args.verify
 552
 553         else: # we want to create
 554                 cert = None
 555                 if not args.certificate:
 556                         if args.protocol != 'tcp':
 557                                 print >> sys.stderr, 'Only SSL over TCP is supported (sorry)'
 558                                 sys.exit(1)
 559
 560                         print 'No certificate specified on the commandline, attempting to retrieve it from the server %s' % (args.host)
 561                         connection_port = args.port
 562                         if args.port == '*':
 563                                 sys.stdout.write('The port specified on the commandline is *, please specify the port of the TLS service on %s (443): ' % args.host)
 564                                 input_ok = False
 565                                 while not input_ok:
 566                                         user_input = raw_input()
 567                                         if user_input == '':
 568                                                 connection_port = 443
 569                                                 break
 570                                         try:
 571                                                 if 1 <= int(user_input) <= 65535:
 572                                                         connection_port = user_input
 573                                                         input_ok = True
 574                                         except:
 575                                                 sys.stdout.write('Port %s not numerical or within correct range (1 <= port <= 65535), try again (hit enter for default 443): ' % user_input)
 576                         # Get the address records for the host
 577                         try:
 578                                 addresses = getA(args.host, secure=secure) + getAAAA(args.host, secure=secure)
 579                         except InsecureLookupException, e:
 580                                 print >> sys.stderr, str(e)
 581                                 sys.exit(1)
 582
 583                         for address in addresses:
 584                                 print 'Attempting to get certificate from %s' % str(address)
 585                                 # We do the certificate handling here, as M2Crypto keeps segfaulting when try to do stuff with the cert if we don't
 586                                 ctx = SSL.Context()
 587                                 ctx.set_verify(SSL.verify_none, depth=9)
 588                                 if isinstance(address, AAAARecord):
 589                                         sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
 590                                         sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 591                                 else:
 592                                         sock = None
 593                                 connection = SSL.Connection(ctx, sock=sock)
 594                                 try:
 595                                         connection.connect((str(address), int(connection_port)))
 596                                 except SSL.Checker.WrongHost:
 597                                         pass
 598                                 except socket.error, e:
 599                                         print 'Cannot connect to %s: %s' % (address, str(e))
 600                                         continue
 601
 602                                 chain = connection.get_peer_cert_chain()
 603                                 for chaincert in chain:
 604                                         if int(args.usage) == 1 or int(args.usage) == 3:
 605                                                 # The first cert is the end-entity cert
 606                                                 print 'Got a certificate with Subject: %s' % chaincert.get_subject()
 607                                                 cert = chaincert
 608                                                 break
 609                                         else:
 610                                                 if (int(args.usage) == 0 and chaincert.check_ca()) or int(args.usage) == 2:
 611                                                         sys.stdout.write('Got a certificate with the following Subject:\n\t%s\nUse this as certificate to match? [y/N] ' % chaincert.get_subject())
 612                                                         input_ok = False
 613                                                         while not input_ok:
 614                                                                 user_input = raw_input()
 615                                                                 if user_input in ['','n','N']:
 616                                                                         input_ok=True
 617                                                                 elif user_input in ['y', 'Y']:
 618                                                                         input_ok = True
 619                                                                         cert = chaincert
 620                                                                 else:
 621                                                                         sys.stdout.write('Please answer Y or N')
 622                                                 if cert:
 623                                                         break
 624
 625                                 if cert: # Print the requested records based on the retrieved certificates
 626                                         if args.output == 'both':
 627                                                 print genTLSA(args.host, args.protocol, args.port, cert, 'draft', args.usage, args.selector, args.mtype)
 628                                                 print genTLSA(args.host, args.protocol, args.port, cert, 'rfc', args.usage, args.selector, args.mtype)
 629                                         else:
 630                                                 print genTLSA(args.host, args.protocol, args.port, cert, args.output, args.usage, args.selector, args.mtype)
 631
 632                                 # Clear the cert from memory (to stop M2Crypto from segfaulting)
 633                                 # And cleanup the connection and context
 634                                 cert=None
 635                                 connection.clear()
 636                                 connection.close()
 637                                 ctx.close()
 638
 639                 else: # Pass the path to the certificate to the genTLSA function
 640                         if args.output == 'both':
 641                                 print genTLSA(args.host, args.protocol, args.port, args.certificate, 'draft', args.usage, args.selector, args.mtype)
 642                                 print genTLSA(args.host, args.protocol, args.port, args.certificate, 'rfc', args.usage, args.selector, args.mtype)
 643                         else:
 644                                 print genTLSA(args.host, args.protocol, args.port, args.certificate, args.output, args.usage, args.selector, args.mtype)