Enter 2006 September/Enter 09 2006.iso/Internet/SpamExperts Home 1.1/SpamExperts Home.exe/lib/spamexperts.modules/dns/message.pyc

Python Compiled Bytecode | 2006-07-14 | 31.6 KB | 1,026 lines

# Source Generated with Decompyle++
# File: in.pyc (Python 2.4)

'''DNS Messages'''
import cStringIO
import random
import struct
import sys
import time
import dns.exception as dns
import dns.flags as dns
import dns.name as dns
import dns.opcode as dns
import dns.rcode as dns
import dns.rdata as dns
import dns.rdataclass as dns
import dns.rdatatype as dns
import dns.rrset as dns
import dns.renderer as dns
import dns.tsig as dns

class ShortHeader(dns.exception.FormError):
    '''Raised if the DNS packet passed to from_wire() is too short.'''
    pass


class TrailingJunk(dns.exception.FormError):
    '''Raised if the DNS packet passed to from_wire() has extra junk
    at the end of it.'''
    pass


class UnknownHeaderField(dns.exception.DNSException):
    '''Raised if a header field name is not recognized when converting from
    text into a message.'''
    pass


class BadEDNS(dns.exception.FormError):
    '''Raised if an OPT record occurs somewhere other than the start of
    the additional data section.'''
    pass


class BadTSIG(dns.exception.FormError):
    '''Raised if a TSIG record occurs somewhere other than the end of
    the additional data section.'''
    pass


class UnknownTSIGKey(dns.exception.DNSException):
    """Raised if we got a TSIG but don't know the key."""
    pass


class Message(object):
    """A DNS message.

    @ivar id: The query id; the default is a randomly chosen id.
    @type id: int
    @ivar flags: The DNS flags of the message.  @see: RFC 1035 for an
    explanation of these flags.
    @type flags: int
    @ivar question: The question section.
    @type question: list of dns.rrset.RRset objects
    @ivar answer: The answer section.
    @type answer: list of dns.rrset.RRset objects
    @ivar authority: The authority section.
    @type authority: list of dns.rrset.RRset objects
    @ivar additional: The additional data section.
    @type additional: list of dns.rrset.RRset objects
    @ivar edns: The EDNS level to use.  The default is -1, no Edns.
    @type edns: int
    @ivar ednsflags: The EDNS flags
    @type ednsflags: long
    @ivar payload: The EDNS payload size.  The default is 0.
    @type payload: int
    @ivar request_payload: The associated request's EDNS payload size.
    @type request_payload: int
    @ivar keyring: The TSIG keyring to use.  The default is None.
    @type keyring: dict
    @ivar keyname: The TSIG keyname to use.  The default is None.
    @type keyname: dns.name.Name object
    @ivar request_mac: The TSIG MAC of the request message associated with
    this message; used when validating TSIG signatures.   @see: RFC 2845 for
    more information on TSIG fields.
    @type request_mac: string
    @ivar fudge: TSIG time fudge; default is 300 seconds.
    @type fudge: int
    @ivar original_id: TSIG original id; defaults to the message's id
    @type original_id: int
    @ivar tsig_error: TSIG error code; default is 0.
    @type tsig_error: int
    @ivar other_data: TSIG other data.
    @type other_data: string
    @ivar mac: The TSIG MAC for this message.
    @type mac: string
    @ivar xfr: Is the message being used to contain the results of a DNS
    zone transfer?  The default is False.
    @type xfr: bool
    @ivar origin: The origin of the zone in messages which are used for
    zone transfers or for DNS dynamic updates.  The default is None.
    @type origin: dns.name.Name object
    @ivar tsig_ctx: The TSIG signature context associated with this
    message.  The default is None.
    @type tsig_ctx: hmac.HMAC object
    @ivar had_tsig: Did the message decoded from wire format have a TSIG
    signature?
    @type had_tsig: bool
    @ivar multi: Is this message part of a multi-message sequence?  The
    default is false.  This variable is used when validating TSIG signatures
    on messages which are part of a zone transfer.
    @type multi: bool
    @ivar first: Is this message standalone, or the first of a multi
    message sequence?  This variable is used when validating TSIG signatures
    on messages which are part of a zone transfer.
    @type first: bool
    @ivar index: An index of rrsets in the message.  The index key is
    (section, name, rdclass, rdtype, covers, deleting).  Indexing can be
    disabled by setting the index to None.
    @type index: dict
    """

    def __init__(self, id = None):
        if id is None:
            self.id = random.randint(0, 65535)
        else:
            self.id = id
        self.flags = 0
        self.question = []
        self.answer = []
        self.authority = []
        self.additional = []
        self.edns = -1
        self.ednsflags = 0
        self.payload = 0
        self.request_payload = 0
        self.keyring = None
        self.keyname = None
        self.request_mac = ''
        self.other_data = ''
        self.tsig_error = 0
        self.fudge = 300
        self.original_id = self.id
        self.mac = ''
        self.xfr = False
        self.origin = None
        self.tsig_ctx = None
        self.had_tsig = False
        self.multi = False
        self.first = True
        self.index = { }


    def __repr__(self):
        return '<DNS message, ID ' + `self.id` + '>'


    def __str__(self):
        return self.to_text()


    def to_text(self, origin = None, relativize = True, **kw):
        '''Convert the message to text.

        The I{origin}, I{relativize}, and any other keyword
        arguments are passed to the rrset to_wire() method.

        @rtype: string
        '''
        s = cStringIO.StringIO()
        print >>s, 'id %d' % self.id
        print >>s, 'opcode %s' % dns.opcode.to_text(dns.opcode.from_flags(self.flags))
        rc = dns.rcode.from_flags(self.flags, self.ednsflags)
        print >>s, 'rcode %s' % dns.rcode.to_text(rc)
        print >>s, 'flags %s' % dns.flags.to_text(self.flags)
        if self.edns >= 0:
            print >>s, 'edns %s' % self.edns
            if self.ednsflags != 0:
                print >>s, 'eflags %s' % dns.flags.edns_to_text(self.ednsflags)

            print >>s, 'payload', self.payload

        is_update = dns.opcode.is_update(self.flags)
        if is_update:
            print >>s, ';ZONE'
        else:
            print >>s, ';QUESTION'
        for rrset in self.question:
            print >>s, rrset.to_text(origin, relativize, **kw)

        if is_update:
            print >>s, ';PREREQ'
        else:
            print >>s, ';ANSWER'
        for rrset in self.answer:
            print >>s, rrset.to_text(origin, relativize, **kw)

        if is_update:
            print >>s, ';UPDATE'
        else:
            print >>s, ';AUTHORITY'
        for rrset in self.authority:
            print >>s, rrset.to_text(origin, relativize, **kw)

        print >>s, ';ADDITIONAL'
        for rrset in self.additional:
            print >>s, rrset.to_text(origin, relativize, **kw)

        return s.getvalue()[:-1]


    def __eq__(self, other):
        '''Two messages are equal if they have the same content in the
        header, question, answer, and authority sections.
        @rtype: bool'''
        if not isinstance(other, Message):
            return False

        if self.id != other.id:
            return False

        if self.flags != other.flags:
            return False

        for n in self.question:
            if n not in other.question:
                return False
                continue

        for n in other.question:
            if n not in self.question:
                return False
                continue

        for n in self.answer:
            if n not in other.answer:
                return False
                continue

        for n in other.answer:
            if n not in self.answer:
                return False
                continue

        for n in self.authority:
            if n not in other.authority:
                return False
                continue

        for n in other.authority:
            if n not in self.authority:
                return False
                continue

        return True


    def __ne__(self, other):
        '''Are two messages not equal?
        @rtype: bool'''
        return not self.__eq__(other)


    def is_response(self, other):
        '''Is other a response to self?
        @rtype: bool'''
        if other.flags & dns.flags.QR == 0 and self.id != other.id or dns.opcode.from_flags(self.flags) != dns.opcode.from_flags(other.flags):
            return False

        if dns.rcode.from_flags(other.flags, other.ednsflags) != dns.rcode.NOERROR:
            return True

        if dns.opcode.is_update(self.flags):
            return True

        for n in self.question:
            if n not in other.question:
                return False
                continue

        for n in other.question:
            if n not in self.question:
                return False
                continue

        return True


    def section_number(self, section):
        if section is self.question:
            return 0
        elif section is self.answer:
            return 1
        elif section is self.authority:
            return 2
        elif section is self.additional:
            return 3
        else:
            raise ValueError, 'unknown section'


    def find_rrset(self, section, name, rdclass, rdtype, covers = dns.rdatatype.NONE, deleting = None, create = False, force_unique = False):
        '''Find the RRset with the given attributes in the specified section.

        @param section: the section of the message to look in, e.g.
        self.answer.
        @type section: list of dns.rrset.RRset objects
        @param name: the name of the RRset
        @type name: dns.name.Name object
        @param rdclass: the class of the RRset
        @type rdclass: int
        @param rdtype: the type of the RRset
        @type rdtype: int
        @param covers: the covers value of the RRset
        @type covers: int
        @param deleting: the deleting value of the RRset
        @type deleting: int
        @param create: If True, create the RRset if it is not found.
        The created RRset is appended to I{section}.
        @type create: bool
        @param force_unique: If True and create is also True, create a
        new RRset regardless of whether a matching RRset exists already.
        @type force_unique: bool
        @raises KeyError: the RRset was not found and create was False
        @rtype: dns.rrset.RRset object'''
        key = (self.section_number(section), name, rdclass, rdtype, covers, deleting)
        if not force_unique:
            if self.index is not None:
                rrset = self.index.get(key)
                if rrset is not None:
                    return rrset

            else:
                for rrset in section:
                    if rrset.match(name, rdclass, rdtype, covers, deleting):
                        return rrset
                        continue


        if not create:
            raise KeyError

        rrset = dns.rrset.RRset(name, rdclass, rdtype, covers, deleting)
        section.append(rrset)
        if self.index is not None:
            self.index[key] = rrset

        return rrset


    def get_rrset(self, section, name, rdclass, rdtype, covers = dns.rdatatype.NONE, deleting = None, create = False, force_unique = False):
        '''Get the RRset with the given attributes in the specified section.

        If the RRset is not found, None is returned.

        @param section: the section of the message to look in, e.g.
        self.answer.
        @type section: list of dns.rrset.RRset objects
        @param name: the name of the RRset
        @type name: dns.name.Name object
        @param rdclass: the class of the RRset
        @type rdclass: int
        @param rdtype: the type of the RRset
        @type rdtype: int
        @param covers: the covers value of the RRset
        @type covers: int
        @param deleting: the deleting value of the RRset
        @type deleting: int
        @param create: If True, create the RRset if it is not found.
        The created RRset is appended to I{section}.
        @type create: bool
        @param force_unique: If True and create is also True, create a
        new RRset regardless of whether a matching RRset exists already.
        @type force_unique: bool
        @rtype: dns.rrset.RRset object or None'''

        try:
            rrset = self.find_rrset(section, name, rdclass, rdtype, covers, deleting, create, force_unique)
        except KeyError:
            rrset = None

        return rrset


    def to_wire(self, origin = None, max_size = 0, **kw):
        """Return a string containing the message in DNS compressed wire
        format.

        Additional keyword arguments are passed to the rrset to_wire()
        method.

        @param origin: The origin to be appended to any relative names.
        @type origin: dns.name.Name object
        @param max_size: The maximum size of the wire format output; default
        is 0, which means 'the message's request payload, if nonzero, or
        65536'.
        @type max_size: int
        @raises dns.exception.TooBig: max_size was exceeded
        @rtype: string
        """
        if max_size == 0:
            if self.request_payload != 0:
                max_size = self.request_payload
            else:
                max_size = 65535

        if max_size < 512:
            max_size = 512
        elif max_size > 65535:
            max_size = 65535

        r = dns.renderer.Renderer(self.id, self.flags, max_size, origin)
        for rrset in self.question:
            r.add_question(rrset.name, rrset.rdtype, rrset.rdclass)

        for rrset in self.answer:
            r.add_rrset(dns.renderer.ANSWER, rrset, **kw)

        for rrset in self.authority:
            r.add_rrset(dns.renderer.AUTHORITY, rrset, **kw)

        if self.edns >= 0:
            r.add_edns(self.edns, self.ednsflags, self.payload)

        for rrset in self.additional:
            r.add_rrset(dns.renderer.ADDITIONAL, rrset, **kw)

        r.write_header()
        if self.keyname is not None:
            r.add_tsig(self.keyname, self.keyring[self.keyname], self.fudge, self.original_id, self.tsig_error, self.other_data, self.request_mac)
            self.mac = r.mac

        return r.get_wire()


    def use_tsig(self, keyring, keyname = None, fudge = 300, original_id = None, tsig_error = 0, other_data = ''):
        """When sending, a TSIG signature using the specified keyring
        and keyname should be added.

        @param keyring: The TSIG keyring to use; defaults to None.
        @type keyring: dict
        @param keyname: The name of the TSIG key to use; defaults to None.
        The key must be defined in the keyring.  If a keyring is specified
        but a keyname is not, then the key used will be the first key in the
        keyring.  Note that the order of keys in a dictionary is not defined,
        so applications should supply a keyname when a keyring is used, unless
        they know the keyring contains only one key.
        @type keyname: dns.name.Name or string
        @param fudge: TSIG time fudge; default is 300 seconds.
        @type fudge: int
        @param original_id: TSIG original id; defaults to the message's id
        @type original_id: int
        @param tsig_error: TSIG error code; default is 0.
        @type tsig_error: int
        @param other_data: TSIG other data.
        @type other_data: string
        """
        self.keyring = keyring
        if keyname is None:
            self.keyname = self.keyring.keys()[0]
        elif isinstance(keyname, str):
            keyname = dns.name.from_text(keyname)

        self.keyname = keyname
        self.fudge = fudge
        if original_id is None:
            self.original_id = self.id
        else:
            self.original_id = original_id
        self.tsig_error = tsig_error
        self.other_data = other_data


    def use_edns(self, edns, ednsflags, payload, request_payload = 0):
        """Configure EDNS behavior.
        @param edns: The EDNS level to use.  Specifying None or -1 means
        'do not use EDNS'.
        @type edns: int or None
        @param ednsflags: EDNS flag values.
        @type ednsflags: int
        @param payload: The EDNS sender's payload field, which is the maximum
        size of UDP datagram the sender can handle.
        @type payload: int
        @see: RFC 2671
        """
        if edns is None:
            edns = -1

        self.edns = edns
        self.ednsflags = ednsflags
        self.payload = payload
        self.request_payload = request_payload


    def rcode(self):
        '''Return the rcode.
        @rtype: int
        '''
        return dns.rcode.from_flags(self.flags, self.ednsflags)


    def set_rcode(self, rcode):
        '''Set the rcode.
        @param rcode: the rcode
        @type rcode: int
        '''
        (value, evalue) = dns.rcode.to_flags(rcode)
        self.flags &= 65520
        self.flags |= value
        self.ednsflags &= 0xFF000000L
        self.ednsflags |= evalue


    def opcode(self):
        '''Return the opcode.
        @rtype: int
        '''
        return dns.opcode.from_flags(self.flags)


    def set_opcode(self, opcode):
        '''Set the opcode.
        @param opcode: the opcode
        @type opcode: int
        '''
        self.flags &= 34815
        self.flags |= dns.opcode.to_flags(opcode)



class _WireReader(object):
    '''Wire format reader.

    @ivar wire: the wire-format message.
    @type wire: string
    @ivar message: The message object being built
    @type message: dns.message.Message object
    @ivar current: When building a message object from wire format, this
    variable contains the offset from the beginning of wire of the next octet
    to be read.
    @type current: int
    @ivar updating: Is the message a dynamic update?
    @type updating: bool
    @ivar zone_rdclass: The class of the zone in messages which are
    DNS dynamic updates.
    @type zone_rdclass: int
    '''

    def __init__(self, wire, message, question_only = False):
        self.wire = wire
        self.message = message
        self.current = 0
        self.updating = False
        self.zone_rdclass = dns.rdataclass.IN
        self.question_only = question_only


    def _get_question(self, qcount):
        '''Read the next I{qcount} records from the wire data and add them to
        the question section.
        @param qcount: the number of questions in the message
        @type qcount: int'''
        if self.updating and qcount > 1:
            raise dns.exception.FormError

        for i in xrange(0, qcount):
            (qname, used) = dns.name.from_wire(self.wire, self.current)
            if self.message.origin is not None:
                qname = qname.relativize(self.message.origin)

            self.current = self.current + used
            (rdtype, rdclass) = struct.unpack('!HH', self.wire[self.current:self.current + 4])
            self.current = self.current + 4
            self.message.find_rrset(self.message.question, qname, rdclass, rdtype, create = True, force_unique = True)
            if self.updating:
                self.zone_rdclass = rdclass
                continue



    def _get_section(self, section, count):
        '''Read the next I{count} records from the wire data and add them to
        the specified section.
        @param section: the section of the message to which to add records
        @type section: list of dns.rrset.RRset objects
        @param count: the number of records to read
        @type count: int'''
        if self.updating:
            force_unique = True
        else:
            force_unique = False
        seen_opt = False
        for i in xrange(0, count):
            rr_start = self.current
            (name, used) = dns.name.from_wire(self.wire, self.current)
            if self.message.origin is not None:
                name = name.relativize(self.message.origin)

            self.current = self.current + used
            (rdtype, rdclass, ttl, rdlen) = struct.unpack('!HHIH', self.wire[self.current:self.current + 10])
            self.current = self.current + 10
            if rdtype == dns.rdatatype.OPT:
                if section is not self.message.additional or seen_opt:
                    raise BadEDNS

                self.message.payload = rdclass
                self.message.ednsflags = ttl
                self.message.edns = (ttl & 16711680) >> 16
                seen_opt = True
            elif rdtype == dns.rdatatype.TSIG:
                if not section is self.message.additional and i == count - 1:
                    raise BadTSIG

                if self.message.keyring is None:
                    raise UnknownTSIGKey, 'got signed message without keyring'

                secret = self.message.keyring.get(name)
                if secret is None:
                    raise UnknownTSIGKey, "key '%s' unknown" % name

                self.message.tsig_ctx = dns.tsig.validate(self.wire, name, secret, int(time.time()), self.message.request_mac, rr_start, self.current, rdlen, self.message.tsig_ctx, self.message.multi, self.message.first)
                self.message.had_tsig = True
            elif ttl < 0:
                ttl = 0

            if self.updating:
                if rdclass == dns.rdataclass.ANY or rdclass == dns.rdataclass.NONE:
                    deleting = rdclass
                    rdclass = self.zone_rdclass
                else:
                    deleting = None
            if deleting == dns.rdataclass.ANY:
                covers = dns.rdatatype.NONE
                rd = None
            else:
                rd = dns.rdata.from_wire(rdclass, rdtype, self.wire, self.current, rdlen, self.message.origin)
                covers = rd.covers()
            if self.message.xfr and rdtype == dns.rdatatype.SOA:
                force_unique = True

            rrset = self.message.find_rrset(section, name, rdclass, rdtype, covers, deleting, True, force_unique)
            if rd is not None:
                rrset.add(rd, ttl)

            self.current = self.current + rdlen



    def read(self):
        '''Read a wire format DNS message and build a dns.message.Message
        object.'''
        l = len(self.wire)
        if l < 12:
            raise ShortHeader

        (self.message.id, self.message.flags, qcount, ancount, aucount, adcount) = struct.unpack('!HHHHHH', self.wire[:12])
        self.current = 12
        if dns.opcode.is_update(self.message.flags):
            self.updating = True

        self._get_question(qcount)
        if self.question_only:
            return None

        self._get_section(self.message.answer, ancount)
        self._get_section(self.message.authority, aucount)
        self._get_section(self.message.additional, adcount)
        if self.current != l:
            raise TrailingJunk

        if self.message.multi and self.message.tsig_ctx and not (self.message.had_tsig):
            self.message.tsig_ctx.update(self.wire)




def from_wire(wire, keyring = None, request_mac = '', xfr = False, origin = None, tsig_ctx = None, multi = False, first = True, question_only = False):
    '''Convert a DNS wire format message into a message
    object.

    @param keyring: The keyring to use if the message is signed.
    @type keyring: dict
    @param request_mac: If the message is a response to a TSIG-signed request,
    I{request_mac} should be set to the MAC of that request.
    @type request_mac: string
    @param xfr: Is this message part of a zone transfer?
    @type xfr: bool
    @param origin: If the message is part of a zone transfer, I{origin}
    should be the origin name of the zone.
    @type origin: dns.name.Name object
    @param tsig_ctx: The ongoing TSIG context, used when validating zone
    transfers.
    @type tsig_ctx: hmac.HMAC object
    @param multi: Is this message part of a multiple message sequence?
    @type multi: bool
    @param first: Is this message standalone, or the first of a multi
    message sequence?
    @type first: bool
    @param question_only: Read only up to the end of the question section?
    @type question_only: bool
    @raises ShortHeader: The message is less than 12 octets long.
    @raises TrailingJunk: There were octets in the message past the end
    of the proper DNS message.
    @raises BadEDNS: An OPT record was in the wrong section, or occurred more
    than once.
    @raises BadTSIG: A TSIG record was not the last record of the additional
    data section.
    @rtype: dns.message.Message object'''
    m = Message(id = 0)
    m.keyring = keyring
    m.request_mac = request_mac
    m.xfr = xfr
    m.origin = origin
    m.tsig_ctx = tsig_ctx
    m.multi = multi
    m.first = first
    reader = _WireReader(wire, m, question_only)
    reader.read()
    return m


class _TextReader(object):
    '''Text format reader.

    @ivar tok: the tokenizer
    @type tok: dns.tokenizer.Tokenizer object
    @ivar message: The message object being built
    @type message: dns.message.Message object
    @ivar updating: Is the message a dynamic update?
    @type updating: bool
    @ivar zone_rdclass: The class of the zone in messages which are
    DNS dynamic updates.
    @type zone_rdclass: int
    @ivar last_name: The most recently read name when building a message object
    from text format.
    @type last_name: dns.name.Name object
    '''

    def __init__(self, text, message):
        self.message = message
        self.tok = dns.tokenizer.Tokenizer(text)
        self.last_name = None
        self.zone_rdclass = dns.rdataclass.IN
        self.updating = False


    def _header_line(self, section):
        '''Process one line from the text format header section.'''
        (ttype, what) = self.tok.get()
        if what == 'id':
            self.message.id = self.tok.get_int()
        elif what == 'flags':
            while True:
                token = self.tok.get()
                if token[0] != dns.tokenizer.IDENTIFIER:
                    self.tok.unget(token)
                    break

                self.message.flags = self.message.flags | dns.flags.from_text(token[1])
            if dns.opcode.is_update(self.message.flags):
                self.updating = True

        elif what == 'edns':
            self.message.edns = self.tok.get_int()
            self.message.ednsflags = self.message.ednsflags | self.message.edns << 16
        elif what == 'eflags':
            if self.message.edns < 0:
                self.message.edns = 0

            while True:
                token = self.tok.get()
                if token[0] != dns.tokenizer.IDENTIFIER:
                    self.tok.unget(token)
                    break

                self.message.ednsflags = self.message.ednsflags | dns.flags.edns_from_text(token[1])
        elif what == 'payload':
            self.message.payload = self.tok.get_int()
            if self.message.edns < 0:
                self.message.edns = 0

        elif what == 'opcode':
            text = self.tok.get_string()
            self.message.flags = self.message.flags | dns.opcode.to_flags(dns.opcode.from_text(text))
        elif what == 'rcode':
            text = self.tok.get_string()
            self.message.set_rcode(dns.rcode.from_text(text))
        else:
            raise UnknownHeaderField
        self.tok.get_eol()


    def _question_line(self, section):
        '''Process one line from the text format question section.'''
        token = self.tok.get(want_leading = True)
        if token[0] != dns.tokenizer.WHITESPACE:
            self.last_name = dns.name.from_text(token[1], None)

        name = self.last_name
        token = self.tok.get()
        if token[0] != dns.tokenizer.IDENTIFIER:
            raise dns.exception.SyntaxError


        try:
            rdclass = dns.rdataclass.from_text(token[1])
            token = self.tok.get()
            if token[0] != dns.tokenizer.IDENTIFIER:
                raise dns.exception.SyntaxError
        except dns.exception.SyntaxError:
            raise dns.exception.SyntaxError
        except:
            rdclass = dns.rdataclass.IN

        rdtype = dns.rdatatype.from_text(token[1])
        self.message.find_rrset(self.message.question, name, rdclass, rdtype, create = True, force_unique = True)
        if self.updating:
            self.zone_rdclass = rdclass

        self.tok.get_eol()


    def _rr_line(self, section):
        '''Process one line from the text format answer, authority, or
        additional data sections.
        '''
        deleting = None
        token = self.tok.get(want_leading = True)
        if token[0] != dns.tokenizer.WHITESPACE:
            self.last_name = dns.name.from_text(token[1], None)

        name = self.last_name
        token = self.tok.get()
        if token[0] != dns.tokenizer.IDENTIFIER:
            raise dns.exception.SyntaxError


        try:
            ttl = int(token[1], 0)
            token = self.tok.get()
            if token[0] != dns.tokenizer.IDENTIFIER:
                raise dns.exception.SyntaxError
        except dns.exception.SyntaxError:
            raise dns.exception.SyntaxError
        except:
            ttl = 0


        try:
            rdclass = dns.rdataclass.from_text(token[1])
            token = self.tok.get()
            if token[0] != dns.tokenizer.IDENTIFIER:
                raise dns.exception.SyntaxError

            if rdclass == dns.rdataclass.ANY or rdclass == dns.rdataclass.NONE:
                deleting = rdclass
                rdclass = self.zone_rdclass
        except dns.exception.SyntaxError:
            raise dns.exception.SyntaxError
        except:
            rdclass = dns.rdataclass.IN

        rdtype = dns.rdatatype.from_text(token[1])
        token = self.tok.get()
        if token[0] != dns.tokenizer.EOL and token[0] != dns.tokenizer.EOF:
            self.tok.unget(token)
            rd = dns.rdata.from_text(rdclass, rdtype, self.tok, None)
            covers = rd.covers()
        else:
            rd = None
            covers = dns.rdatatype.NONE
        rrset = self.message.find_rrset(section, name, rdclass, rdtype, covers, deleting, True, self.updating)
        if rd is not None:
            rrset.add(rd, ttl)



    def read(self):
        '''Read a text format DNS message and build a dns.message.Message
        object.'''
        line_method = self._header_line
        section = None
        while None:
            token = self.tok.get(True, True)
            if token[0] == dns.tokenizer.EOL or token[0] == dns.tokenizer.EOF:
                break

            if token[0] == dns.tokenizer.COMMENT:
                u = token[1].upper()
                if u == 'HEADER':
                    line_method = self._header_line
                elif u == 'QUESTION' or u == 'ZONE':
                    line_method = self._question_line
                    section = self.message.question
                elif u == 'ANSWER' or u == 'PREREQ':
                    line_method = self._rr_line
                    section = self.message.answer
                elif u == 'AUTHORITY' or u == 'UPDATE':
                    line_method = self._rr_line
                    section = self.message.authority
                elif u == 'ADDITIONAL':
                    line_method = self._rr_line
                    section = self.message.additional

                self.tok.get_eol()
                continue

            line_method(section)



def from_text(text):
    '''Convert the text format message into a message object.

    @param text: The text format message.
    @type text: string
    @raises UnknownHeaderField:
    @raises dns.exception.SyntaxError:
    @rtype: dns.message.Message object'''
    m = Message()
    reader = _TextReader(text, m)
    reader.read()
    return m


def from_file(f):
    '''Read the next text format message from the specified file.

    @param f: file or string.  If I{f} is a string, it is treated
    as the name of a file to open.
    @raises UnknownHeaderField:
    @raises dns.exception.SyntaxError:
    @rtype: dns.message.Message object'''
    if sys.hexversion >= 33751040:
        str_type = basestring
        opts = 'rU'
    else:
        str_type = str
        opts = 'r'
    if isinstance(f, str_type):
        f = file(f, opts)
        want_close = True
    else:
        want_close = False

    try:
        m = from_text(f)
    finally:
        if want_close:
            f.close()


    return m


def make_query(qname, rdtype, rdclass = dns.rdataclass.IN):
    '''Make a query message.

    The query name, type, and class may all be specified either
    as objects of the appropriate type, or as strings.

    The query will have a randomly choosen query id, and its DNS flags
    will be set to dns.flags.RD.

    @param qname: The query name.
    @type qname: dns.name.Name object or string
    @param rdtype: The desired rdata type.
    @type rdtype: int
    @param rdclass: The desired rdata class; the default is class IN.
    @type rdclass: int
    @rtype: dns.message.Message object'''
    if isinstance(qname, str):
        qname = dns.name.from_text(qname)

    if isinstance(rdtype, str):
        rdtype = dns.rdatatype.from_text(rdtype)

    if isinstance(rdclass, str):
        rdclass = dns.rdataclass.from_text(rdclass)

    m = Message()
    m.flags |= dns.flags.RD
    m.find_rrset(m.question, qname, rdclass, rdtype, create = True, force_unique = True)
    return m


def make_response(query, recursion_available = False, our_payload = 8192):
    """Make a message which is a response for the specified query.
    The message returned is really a response skeleton; it has all
    of the infrastructure required of a response, but none of the
    content.

    The response's question section is a shallow copy of the query's
    question section, so the query's question RRsets should not be
    changed.

    @param query: the query to respond to
    @type query: dns.message.Message object
    @param recursion_available: should RA be set in the response?
    @type recursion_available: bool
    @param our_payload: payload size to advertise in EDNS responses; default
    is 8192.
    @type our_payload: int
    @rtype: dns.message.Message object"""
    if query.flags & dns.flags.QR:
        raise dns.exception.FormError, 'specified query message is not a query'

    response = dns.message.Message(query.id)
    response.flags = dns.flags.QR | query.flags & dns.flags.RD
    if recursion_available:
        response.flags |= dns.flags.RA

    response.set_opcode(query.opcode())
    response.question = list(query.question)
    if query.edns >= 0:
        response.use_edns(0, 0, our_payload, query.payload)

    if query.keyname is not None:
        response.keyname = query.keyname
        response.keyring = query.keyring
        response.request_mac = query.mac

    return response