Class: Dnsruby::RR::TSIG

### Home Classes Methods

### In Files

- lib/Dnsruby/resource/TSIG.rb

### Parent

Dnsruby::RR

### Methods

- #algorithm=
- #apply
- #calculate_mac
- #fudge=
- #init_defaults
- #name=
- #rdata_to_string
- #verify
- #verify_envelope

### Files

- DNSSEC
- EVENTMACHINE
- EXAMPLES
- README

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No matching classes.

# Dnsruby::RR::TSIG

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

### Constants

DEFAULT_ALGORITHM
DEFAULT_FUDGE
HMAC_MD5
HMAC_SHA1
HMAC_SHA256
TypeValue

### 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

algorithm=(alg) click to toggle source

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

- hmac-md5

- hmac-sha1

- hmac-sha256

    # File lib/Dnsruby/resource/TSIG.rb, line 518
    def algorithm=(alg)
      if (alg.class == String)
        if (alg.downcase=="hmac-md5")
          @algorithm = HMAC_MD5;
        elsif (alg.downcase=="hmac-sha1")
          @algorithm = HMAC_SHA1;
        elsif (alg.downcase=="hmac-sha256")
          @algorithm = HMAC_SHA256;
        else
          raise ArgumentError.new("Invalid TSIG algorithm")
        end
      elsif (alg.class == Name)
        if (alg!=HMAC_MD5 && alg!=HMAC_SHA1 && alg!=HMAC_SHA256)
          raise ArgumentException.new("Invalid TSIG algorithm")
        end
        @algorithm=alg
      else
        raise ArgumentError.new("#{alg.class} not valid type for Dnsruby::RR::TSIG#algorithm=  - use String or Name")
      end
      Dnsruby.log.debug{"Using #{@algorithm.to_s} algorithm"}
    end

apply(message, original_request=nil) click to toggle source

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.

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

calculate_mac(algorithm, data) click to toggle source

    # File lib/Dnsruby/resource/TSIG.rb, line 143
          def calculate_mac(algorithm, data)
            mac=nil
    #+ if (key_size > max_digest_len) {

    #+   EVP_DigestInit(&ectx, digester);

    #+   EVP_DigestUpdate(&ectx, (const void*) key_bytes, key_size);

    #+   EVP_DigestFinal(&ectx, key_bytes, NULL);

    #+   key_size = max_digest_len;

    #+ }

            key = @key.gsub(" ", "")
     #       key = Base64::decode64(key)

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

              raise VerifyError.new("Algorithm #{algorithm} unsupported by TSIG")
            end
            return mac
          end

fudge=(f) click to toggle source

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

init_defaults() click to toggle source

    # File lib/Dnsruby/resource/TSIG.rb, line 466
    def init_defaults
      # @TODO@ Have new() method which takes key_name and key?

      @algorithm   = DEFAULT_ALGORITHM
      @fudge       = DEFAULT_FUDGE
      @mac_size    = 0
      @mac         = ""
      @original_id = rand(65536)
      @error       = 0
      @other_size   = 0
      @other_data  = ""
      @time_signed = nil
      @buf = nil

      # RFC 2845 Section 2.3

      @klass = Classes.ANY

      @ttl = 0 # RFC 2845 Section 2.3

    end

name=(n) click to toggle source

    # File lib/Dnsruby/resource/TSIG.rb, line 489
    def name=(n)
      if (n.instance_of?String)
        n = Name.create(n)
      end
      if (!n.absolute?)
        @name = Name.create(n.to_s + ".")
      else
        @name = n
      end
    end

rdata_to_string() click to toggle source

    # File lib/Dnsruby/resource/TSIG.rb, line 548
    def rdata_to_string
      rdatastr=""
      if (@algorithm!=nil)
        error = @error
        error = "UNDEFINED" unless error!=nil
        rdatastr = "#{@original_id} #{@time_signed} #{@algorithm.to_s(true)} #{error}";
        if (@other_size > 0 && @other_data!=nil)
          rdatastr += " #{@other_data}"
        end
        rdatastr += " " + mac.unpack("H*").to_s
      end

      return rdatastr
    end

verify(query, response, response_bytes, buf="") click to toggle source

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

    # File lib/Dnsruby/resource/TSIG.rb, line 191
    def verify(query, response, response_bytes, buf="")
      #        4.6. Client processing of answer

      #

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

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

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

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

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

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

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

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

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

      #   record which fails verification SHOULD not be considered an

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

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

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

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

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

      # Side effect is packet is stripped of TSIG.

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

      msg_tsig_rr = response.tsig
      if (!verify_common(response))
        return false
      end

      new_msg_tsig_rr = generate(response, query, buf, response_bytes, msg_tsig_rr)

      if (msg_tsig_rr.mac == new_msg_tsig_rr.mac)
        response.tsigstate = :Verified
        response.tsigerror = RCode.NOERROR
        return true
      else
        response.tsigstate = :Failed
        response.tsigerror = RCode.BADSIG
        return false
      end
    end

verify_envelope(response, response_bytes) click to toggle source

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 responsetsigstate 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 responsetsigstate is set to :Intermediate. If there is an error with the TSIG verification, then the responsetsigstate 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.

    # File lib/Dnsruby/resource/TSIG.rb, line 279
    def verify_envelope(response, response_bytes)
      #RFC2845 Section 4.4

      #-----

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

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

      #connection can protect the connection from hijacking and provide data

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

      #envelopes.  It can be optionally placed on any intermediary

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

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

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

      #following digest components:

      #

      #*   Prior Digest (running)

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

      #*   TSIG Timers (current message)

      #

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

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

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

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

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

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

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

      #exact behavior is not specified).

      #-----

      #

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

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

      # as appropriate.

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

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

      # verified. Can reset digest then.

      if (!@buf)
        @num_envelopes = 0
        @last_signed = 0
      end
      @num_envelopes += 1
      if (!response.tsig)
        if ((@num_envelopes > 1) && (@num_envelopes - @last_signed < 100))
          Dnsruby.log.debug("Receiving intermediate envelope in TSIG TCP session")
          response.tsigstate = :Intermediate
          response.tsigerror = RCode.NOERROR
          @buf = @buf + response_bytes
          return
        else
          response.tsigstate = :Failed
          Dnsruby.log.error("Expecting signed packet")
          return false
        end
      end
      @last_signed = @num_envelopes

      # We have a TSIG - process it!

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

        ok = verify(@query, response, response_bytes)
        if (ok)
          mac_bytes = MessageEncoder.new {|m|
            m.put_pack('n', tsig.mac_size)
            m.put_bytes(tsig.mac)
          }.to_s
          @buf = mac_bytes
        end
        return ok
      end
      Dnsruby.log.debug("Processing TSIG on TSIG TCP session")

      if (!verify_common(response))
        return false
      end

      # Now add the current message data - remember to frig the arcount

      response_bytes = Header.decrement_arcount_encoded(response_bytes)
      @buf += response_bytes[0, response.tsigstart]

      # Let's add the timers

      timers_data = MessageEncoder.new { |msg|
        time_high = (tsig.time_signed >> 32)
        time_low = (tsig.time_signed & 0xFFFFFFFF)
        msg.put_pack('nN', time_high, time_low)
        msg.put_pack('n', tsig.fudge)
      }.to_s
      @buf += timers_data

      mac = calculate_mac(tsig.algorithm, @buf)

      if (mac != tsig.mac)
        Dnsruby.log.error("TSIG Verify error on TSIG TCP session")
        response.tsigstate = :Failed
        return false
      end
      mac_bytes = MessageEncoder.new {|m|
        m.put_pack('n', mac.length)
        m.put_bytes(mac)
      }.to_s
      @buf=mac_bytes

      response.tsigstate = :Verified
      response.tsigerror = RCode.NOERROR
      return true
    end

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