Bug in SIG(0) signature generation in 2.1.5

[Tekto <te...@ge...>]

Hi,

-- Description --

SIG0.signMessage in Version 2.1.5 is calculating a wrong signature. Sending
following update-request to a server will produce a SERVFAIL:

	SimpleResolver resolver = new SimpleResolver("somedns.example.invalid.");
	Name sig0zoneName = new Name("sig0.invalid.");
	Name sig0hostName = new Name("sometext.sig0.invalid.");

	KeyFactory keyFactory = KeyFactory.getInstance("RSA");
	RSAPrivateKey privKey = getPrivateZoneCrtKey(keyFactory);
	RSAPublicKey pubKey = getPublicZoneKey(keyFactory);

	KEYRecord keyRecord = new KEYRecord(sig0zoneName, DClass.IN, 0, Flags.HOST, Protocol.DNSSEC, Algorithm.RSASHA1, pubKey);		
	TXTRecord txtRecord = new TXTRecord(sig0hostName, DClass.IN, 0, "Hello World!");
	Update updateMessage = new Update(sig0zoneName);
	updateMessage.add(txtRecord);

	SIG0.signMessage(updateMessage, keyRecord, privKey, null);


-- How to reproduce --

Use SIG0.verifyMessage and try to verify updateMessage.toWire() which will
throw a DNSSEC.DNSSECException.

	SIG0.verifyMessage(updateMessage, updateMessage.toWire(), keyRecord, null);

-- Reason --
	
in DNSSEC.java signMessage(Message message, SIGRecord previous, KEYRecord key,
  PrivateKey privkey, Date inception, Date expiration)
update message is added to the same DNSOutput-Buffer as the introducing SIG-RDATA.
Therefore name compression calculation in update-section will refer to a wrong
offset (Start of to-sign data block instead of the start of the message will be
truly send over the wire. Verification on the server counterpart will fail.
(tested against BIND 9.7.3)

-- How to fix it --

Changing line 955 (in Version 2.1.5) in DNSSEC.java from

	message.toWire(out);

to
	
	out.writeByteArray(message.toWire());

will fix this behaviour since it uses a second, independent DNSOutput-buffer for
calculation.


Regards,
	Adam