org.eclipse.californium.scandium.dtls

Class HelloExtension

java.lang.Object

org.eclipse.californium.scandium.dtls.HelloExtension

Direct Known Subclasses:

CertificateTypeExtension, ConnectionIdExtension, MaxFragmentLengthExtension, RecordSizeLimitExtension, ServerNameExtension, SignatureAlgorithmsExtension, SupportedEllipticCurvesExtension, SupportedPointFormatsExtension

public abstract class HelloExtension
extends Object

An abstract class representing the functionality for all possible defined extensions.

See RFC 5246 for the extension format.

In particular this class is an object representation of the Extension struct defined in TLS 1.2, Section 7.4.1.4:

 struct {
    ExtensionType extension_type;
    opaque extension_data<0..2^16-1>;
 } Extension;
 
 enum {
    signature_algorithms(13), (65535)
 } ExtensionType;
 

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	HelloExtension.ExtensionType The possible extension types (defined in multiple documents).

Field Summary

Fields

Modifier and Type	Field and Description
static int	LENGTH_BITS
protected static int	TYPE_BITS

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	HelloExtension(HelloExtension.ExtensionType type)

Method Summary

Methods

Modifier and Type	Method and Description
protected abstract void	addExtensionData(org.eclipse.californium.elements.util.DatagramWriter writer) Adds binary encoding of this extension's data.
static HelloExtension	fromExtensionDataReader(int typeCode, org.eclipse.californium.elements.util.DatagramReader extensionDataReader, InetSocketAddress peerAddress) De-serializes a Client or Server Hello handshake message extension from its binary representation.
abstract int	getLength() Gets the overall length of this extension's corresponding Extension struct.
byte[]	toByteArray() Serializes this extension to its byte representation as specified by its respective RFC.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

TYPE_BITS

protected static final int TYPE_BITS

See Also:

Constant Field Values

LENGTH_BITS

public static final int LENGTH_BITS

See Also:

Constant Field Values

Constructor Detail

HelloExtension

protected HelloExtension(HelloExtension.ExtensionType type)

Method Detail

getLength

public abstract int getLength()

Gets the overall length of this extension's corresponding Extension struct.

Note that this includes the 2 bytes indicating the extension type.

Returns:

the length in bytes

toByteArray

public final byte[] toByteArray()

Serializes this extension to its byte representation as specified by its respective RFC.

This method writes this extension's 2-byte code to the result array and then hands the array over to the addExtensionData(DatagramWriter) method in order to add the encoded extension data.

Returns:

The byte representation.

addExtensionData

protected abstract void addExtensionData(org.eclipse.californium.elements.util.DatagramWriter writer)

Adds binary encoding of this extension's data.

This implementation does not do anything. Sub-classes should override this method and use the passed-in writer to add their extension_data bytes to the Extension data structure.

NB: Subclasses MUST NOT write the extension's type code to the writer as this will already have been done by the toByteArray() method.

Parameters:

writer - the writer to use for serialization

fromExtensionDataReader

public static HelloExtension fromExtensionDataReader(int typeCode,
                                     org.eclipse.californium.elements.util.DatagramReader extensionDataReader,
                                     InetSocketAddress peerAddress)
                                              throws HandshakeException

De-serializes a Client or Server Hello handshake message extension from its binary representation. The TLS spec is unspecific about how a server should handle extensions sent by a client that it does not understand. However, Section 4.2 of RFC 7250 mandates that a server implementation must simply ignore extensions of type client_certificate_type or server_certificate_type if it does not support these extensions. This (lenient) approach seems feasible for the server to follow in general when a client sends an extension of a type that the server does not know or support (yet).

Parameters:

typeCode - the extension type code

extensionDataReader - the serialized extension

peerAddress - the IP address and port of the peer that sent this extension

Returns:

the object representing the extension or null if the extension type is not (yet) known to or supported by Scandium.

Throws:

HandshakeException - if the (supported) extension could not be de-serialized, e.g. due to erroneous encoding etc.

toString

public String toString()

Overrides:

toString in class Object