org.eclipse.californium.scandium.dtls

Class HelloVerifyRequest

java.lang.Object

org.eclipse.californium.scandium.dtls.AbstractMessage

org.eclipse.californium.scandium.dtls.HandshakeMessage

org.eclipse.californium.scandium.dtls.HelloVerifyRequest

All Implemented Interfaces:

DTLSMessage

public final class HelloVerifyRequest
extends HandshakeMessage

The server send this request after receiving a ClientHello message to prevent Denial-of-Service Attacks.

See RFC 6347 for the definition.

It seems, that this definition is ambiguous about the server version to be used.

 The server_version field ...
 DTLS 1.2 server implementations SHOULD use DTLS version 1.0 regardless
 of the version of TLS that is expected to be negotiated. ...
 The server MUST use the same version number in the HelloVerifyRequest
 that it would use when sending a ServerHello. ...
 

A DTLS 1.2 server can either (SHOULD) send a version 1.0, or (MUST use same version) 1.2. This question is pending in the IETF TLS mailing list, see RFC 6347 - Section 4.2.1 - used version in a HelloVerifyReques.

There may be many assumptions about the intended behavior. One is to postpone the version negotiation according RFC 5246 - E.1 - Compatibility with TLS 1.0/1.1 and SSL 3.0 until the endpoint ownership is verified. That prevents sending protocol-version alerts to wrong clients.

Behavior of other DTLS 1.2 implementations:

openssl 1.1.1

1.0

gnutls 3.5.18

1.0

mbedtls 2.24.0

1.2

wolfssl 4.5

1.2

tinydtls 0.8.6

1.0 protocol-version in record-header, 1.2 server version in hello-verify-request

All clients of these libraries are able to perform a dtls-handshake with both variants, 1.0 and 1.2. Some other clients seems to have trouble with 1.0. If interoperability is required, a client MUST comply with the definition there:

 DTLS 1.2 and 1.0 clients MUST use the version solely to
 indicate packet formatting (which is the same in both DTLS 1.2 and
 1.0) and not as part of version negotiation.  In particular, DTLS 1.2
 clients MUST NOT assume that because the server uses version 1.0 in
 the HelloVerifyRequest that the server is not DTLS 1.2 or that it
 will eventually negotiate DTLS 1.0 rather than DTLS 1.2.
 

Field Summary

Fields inherited from class org.eclipse.californium.scandium.dtls.HandshakeMessage

FRAGMENT_LENGTH_BITS, FRAGMENT_OFFSET_BITS, MESSAGE_HEADER_LENGTH_BYTES, MESSAGE_LENGTH_BITS, MESSAGE_SEQ_BITS, MESSAGE_TYPE_BITS

Constructor Summary

Constructors

Constructor and Description
HelloVerifyRequest(ProtocolVersion version, byte[] cookie, InetSocketAddress peerAddress)

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	fragmentToByteArray() The serialization of the handshake body (without the handshake header).
static HandshakeMessage	fromReader(org.eclipse.californium.elements.util.DatagramReader reader, InetSocketAddress peerAddress)
byte[]	getCookie()
int	getMessageLength() Must be implemented by each subclass.
HandshakeType	getMessageType() Returns the type of the handshake message.
ProtocolVersion	getServerVersion()
String	toString()

Methods inherited from class org.eclipse.californium.scandium.dtls.HandshakeMessage

fragmentChanged, fromByteArray, fromGenericHandshakeMessage, getContentType, getFragmentLength, getFragmentOffset, getMessageSeq, getNextHandshakeMessage, getRawMessage, setMessageSeq, setNextHandshakeMessage, size, toByteArray, writeTo

Methods inherited from class org.eclipse.californium.scandium.dtls.AbstractMessage

getPeer

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

HelloVerifyRequest

public HelloVerifyRequest(ProtocolVersion version,
                  byte[] cookie,
                  InetSocketAddress peerAddress)

Method Detail

fragmentToByteArray

public byte[] fragmentToByteArray()

Description copied from class: HandshakeMessage

The serialization of the handshake body (without the handshake header). Must be implemented by each subclass. Except the ClientHello, the fragments are considered to be not modified. If a modification is required, call HandshakeMessage.fragmentChanged().

Specified by:

fragmentToByteArray in class HandshakeMessage

Returns:

the raw byte representation of the handshake body.

fromReader

public static HandshakeMessage fromReader(org.eclipse.californium.elements.util.DatagramReader reader,
                          InetSocketAddress peerAddress)

getMessageType

public HandshakeType getMessageType()

Description copied from class: HandshakeMessage

Returns the type of the handshake message. See HandshakeType.

Specified by:

getMessageType in class HandshakeMessage

Returns:

the HandshakeType.

getMessageLength

public int getMessageLength()

Description copied from class: HandshakeMessage

Must be implemented by each subclass. The length is given in bytes and only includes the length of the subclass' specific fields (not the handshake message header).

Specified by:

getMessageLength in class HandshakeMessage

Returns:

the length of the message in bytes.

getServerVersion

public ProtocolVersion getServerVersion()

getCookie

public byte[] getCookie()

toString

public String toString()

Overrides:

toString in class HandshakeMessage