Class: Dnsruby::RR::TSIG

Inherits:
Dnsruby::RR show all
Defined in:
lib/Dnsruby/resource/TSIG.rb

Overview

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

Constant Summary collapse

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 =

:nodoc: all

Types::TSIG
ClassValue =

:nodoc: all

nil

Constants inherited from Dnsruby::RR

ClassInsensitiveTypes

Instance Attribute Summary collapse

Attributes inherited from Dnsruby::RR

#klass, #name, #rdata, #ttl, #type

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Dnsruby::RR

#==, create, #eql?, #from_hash, get_class, get_num, #hash, implemented_rrs, new_from_data, new_from_hash, new_from_string, #rdlength, #sameRRset, #to_s

Instance Attribute Details

#algorithm ⇒ Object

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"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 391

def algorithm
  @algorithm
end

#error ⇒ Object

Returns the RCODE covering TSIG processing. Common values are NOERROR, BADSIG, BADKEY, and BADTIME. See RFC 2845 for details.

print "error = ", rr.error, "\n"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 441

def error
  @error
end

#fudge ⇒ Object

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"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 411

def fudge
  @fudge
end

#key ⇒ Object

Stores the secret key used for signing/verifying messages.



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# File 'lib/Dnsruby/resource/TSIG.rb', line 459

def key
  @key
end

#mac ⇒ Object

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"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 427

def mac
  @mac
end

#mac_size ⇒ Object

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"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 419

def mac_size
  @mac_size
end

#original_id ⇒ Object

Gets or sets the original message ID.

rr.original_id(12345)
print "original ID = ", rr.original_id, "\n"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 434

def original_id
  @original_id
end

#other_data ⇒ Object

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"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 456

def other_data
  @other_data
end

#other_size ⇒ Object

Returns the length of the Other Data. Should be zero unless the error is BADTIME.

print "other len = ", rr.other_size, "\n"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 448

def other_size
  @other_size
end

#time_signed ⇒ Object

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"



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# File 'lib/Dnsruby/resource/TSIG.rb', line 401

def time_signed
  @time_signed
end

Class Method Details

.decode_rdata(msg) ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/resource/TSIG.rb', line 573

def self.decode_rdata(msg) #:nodoc: all

  alg=msg.get_name
  time_high, time_low = msg.get_unpack("nN")
  time_signed = (time_high << 32) + time_low
  fudge, = msg.get_unpack("n")
  mac_size, = msg.get_unpack("n")
  mac = msg.get_bytes(mac_size)
  original_id, = msg.get_unpack("n")
  error, = msg.get_unpack("n")
  other_size, = msg.get_unpack("n")
  other_data = msg.get_bytes(other_size)
  return self.new([alg, time_signed, fudge, mac_size, mac, original_id, error, other_size, other_data])
end

Instance Method Details

#apply(message, original_request = nil) ⇒ Object

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.



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# 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) ⇒ Object 



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# File 'lib/Dnsruby/resource/TSIG.rb', line 143

def calculate_mac(algorithm, data)
  mac=nil
  key = @key.gsub(" ", "")
 #       key = Base64::decode64(key)

  key = key.unpack("m*")[0]
  if (algorithm == HMAC_MD5)
    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

#encode_rdata(msg, canonical = false) ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/resource/TSIG.rb', line 558

def encode_rdata(msg, canonical=false) #:nodoc: all

  # Name needs to be added with no compression - done in Dnsruby::Message#encode

  msg.put_name(@algorithm.downcase, true)
  time_high = (@time_signed >> 32)
  time_low = (@time_signed & 0xFFFFFFFF)
  msg.put_pack('nN', time_high, time_low)
  msg.put_pack('n', @fudge)
  msg.put_pack('n', @mac_size)
  msg.put_bytes(@mac)
  msg.put_pack('n', @original_id)
  msg.put_pack('n', @error)
  msg.put_pack('n', @other_size)
  msg.put_bytes(@other_data)
end

#from_data(data) ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/resource/TSIG.rb', line 480

def from_data(data) #:nodoc: all

  @algorithm, @time_signed, @fudge, @mac_size, @mac, @original_id, @error, @other_size, @other_data = data
end

#from_string(str) ⇒ Object

Create the RR from a standard string



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# File 'lib/Dnsruby/resource/TSIG.rb', line 496

def from_string(str) #:nodoc: all

  parts = str.split("[:/]")
  if (parts.length < 2 || parts.length > 3)
    raise ArgumentException.new("Invalid TSIG key specification")
  end
  if (parts.length == 3)
    return TSIG.new(parts[0], parts[1], parts[2]);
  else
    return TSIG.new(HMAC_MD5, parts[0], parts[1]);
  end
end

#generate(msg, original_request = nil, data = "", msg_bytes = nil, tsig_rr = self) ⇒ Object

Generates a TSIG record



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# File 'lib/Dnsruby/resource/TSIG.rb', line 83

def generate(msg, original_request = nil, data="", msg_bytes=nil, tsig_rr=self)#:nodoc: all

  time_signed=@time_signed
  if (!time_signed)
    time_signed=Time.now.to_i
  end
  if (tsig_rr.time_signed)
    time_signed = tsig_rr.time_signed
  end
  
  if (original_request)
    # # Add the request MAC if present (used to validate responses).

    #   hmac.update(pack("H*", request_mac))

    mac_bytes = MessageEncoder.new {|m|
      m.put_pack('n', original_request.tsig.mac_size)
      m.put_bytes(original_request.tsig.mac)
    }.to_s
    data  += mac_bytes
    # Original ID - should we set message ID to original ID?

    if (tsig_rr != self)
      msg.header.id = tsig_rr.original_id
    else
      msg.header.id = original_request.header.id
    end
  end
  
  if (!msg_bytes)
    msg_bytes = msg.encode
    data += msg_bytes
  else
    # If msg_bytes came in, we need somehow to remove the TSIG RR

    # It is the last record, so we can strip it if we know where it starts

    # We must also poke the header ARcount to decrement it

    msg_bytes = Header.decrement_arcount_encoded(msg_bytes)
    data += msg_bytes[0, msg.tsigstart]
  end
  
  data += sig_data(tsig_rr, time_signed)
  
  mac = calculate_mac(tsig_rr.algorithm, data)
  
  mac_size = mac.length

  new_tsig_rr = Dnsruby::RR.create({
      :name        => tsig_rr.name,
      :type        => Types.TSIG,
      :ttl         => tsig_rr.ttl,
      :klass       => tsig_rr.klass,
      :algorithm   => tsig_rr.algorithm,
      :fudge       => tsig_rr.fudge,
      :key         => @key,
      :mac         => mac,
      :mac_size    => mac_size,
      :error       => tsig_rr.error,
      :time_signed => time_signed,
      :original_id => msg.header.id
    })
  return new_tsig_rr
  
end

#init_defaults ⇒ Object 



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# File 'lib/Dnsruby/resource/TSIG.rb', line 461

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 = "ANY"
  
  @ttl = 0 # RFC 2845 Section 2.3

end

#name=(n) ⇒ Object 



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# File 'lib/Dnsruby/resource/TSIG.rb', line 484

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

#query=(q) ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/resource/TSIG.rb', line 77

def query=q#:nodoc: all

  @query = q
end

#rdata_to_string ⇒ Object 



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# File 'lib/Dnsruby/resource/TSIG.rb', line 543

def rdata_to_string        
  rdatastr=""
  if (@algorithm!=nil)
    error = @error
    error = "UNDEFINED" unless error!=nil
    rdatastr = "#{@original_id} #{@time_signed} #{@algorithm}. #{error}";
    if (@other_size > 0 && @other_data!=nil)
      rdatastr += " #{@other_data}"
    end
    rdatastr += " " + mac.unpack("H*").to_s
  end
  
  return rdatastr
end

#sig_data(tsig_rr, time_signed = @time_signed) ⇒ Object

Private method to return the TSIG RR data to be signed



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# File 'lib/Dnsruby/resource/TSIG.rb', line 162

def sig_data(tsig_rr, time_signed=@time_signed) #:nodoc: all

  return MessageEncoder.new { |msg|
    msg.put_name(tsig_rr.name.downcase, true)
    msg.put_pack('nN', tsig_rr.klass.code, tsig_rr.ttl)
    msg.put_name(tsig_rr.algorithm.downcase, true)
    
    time_high = (time_signed >> 32)
    time_low = (time_signed & 0xFFFFFFFF)
    msg.put_pack('nN', time_high, time_low)
    msg.put_pack('n', tsig_rr.fudge)
    msg.put_pack('n', tsig_rr.error)
    msg.put_pack('n', tsig_rr.other_size)
    msg.put_bytes(tsig_rr.other_data)
  }.to_s
end

#verify(query, response, response_bytes, buf = "") ⇒ Object

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



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# File 'lib/Dnsruby/resource/TSIG.rb', line 185

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_common(response) ⇒ Object

:nodoc: all



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# File 'lib/Dnsruby/resource/TSIG.rb', line 225

def verify_common(response)#:nodoc: all

  tsig_rr = response.tsig

  if (!tsig_rr)
    response.tsigerror = RCode.FORMERR
    response.tsigstate = :Failed
    return false
  end

  response.additional.delete(tsig_rr)
  response.header.arcount-=1

  # First, check the TSIG error in the RR

  if (tsig_rr.error != RCode.NOERROR)
    response.tsigstate = :Failed
    response.tsigerror = tsig_rr.error
    return false                    
  end
  
  if ((tsig_rr.name != @name) || (tsig_rr.algorithm.downcase != @algorithm.downcase))
    Dnsruby.log.error("BADKEY failure")
    response.tsigstate = :Failed
    response.tsigerror = RCode.BADKEY
    return false          
  end
  
  # Check time_signed (RFC2845, 4.5.2) - only really necessary for server

  if (Time.now.to_i > tsig_rr.time_signed + tsig_rr.fudge  ||
        Time.now.to_i < tsig_rr.time_signed - tsig_rr.fudge)
    Dnsruby.log.error("TSIG failed with BADTIME")
    response.tsigstate = :Failed
    response.tsigerror = RCode.BADTIME
    return false          
  end
  
  return true
end

#verify_envelope(response, response_bytes) ⇒ Object

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.



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# File 'lib/Dnsruby/resource/TSIG.rb', line 273

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
    else
    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