ddn.net.dtls.client12

DTLS 1.2 client handshake state machine (RFC 6347).

Drives the DTLS 1.2 client handshake as a resumable state machine. Adapts the TLS 1.2 handshake for datagram transports with:

DTLS record framing (13-byte header)
DTLS handshake framing (12-byte header with message_seq)
Flight-based retransmission with exponential backoff
Cookie exchange (HelloVerifyRequest)
Handshake message fragmentation
Anti-replay protection

Reuses cryptographic primitives from the TLS 1.2 implementation: PRF (Tls12Prf), AEAD (TlsAead), key exchange (X25519, ECDH P-256), certificate parsing, and signature verification.

var DTLS_1_2_RECORD_VERSION

class Dtls12Client

Types 1

classDtls12Client

DTLS 1.2 client handshake engine.

Drives the client side of a DTLS 1.2 handshake over a datagram transport. Uses flight-based retransmission with exponential backoff and supports the HelloVerifyRequest cookie exchange for DoS mitigation.

Call handshake() repeatedly until it returns TlsProgress.DONE. Between calls, wait for socket readiness as indicated by the return value.

Fields

private DtlsTransport transport_

private DtlsTimerSink timer_

private DatagramEndpoint serverAddr_

private Dtls12ClientPhase phase_

private ushort epoch_

private ushort readEpoch_

private ulong recordSeq_

private int lastPeerMsgSeq_Highest fully processed peer handshake message_seq (RFC 6347 §4.2.2); -1 until the first message completes.

private ushort messageSeq_Per-direction transmit counter (RFC 6347 §4.2.2).

private ushort lastRecvSeq_message_seq from the most recently received handshake message, used when hashing inbound messages into the transcript.

private SecureRandom rng_

private DtlsFlight pendingFlight_

private int retryCount_

private ubyte[32] clientRandom_

private ubyte[32] serverRandom_

private ubyte[] preMasterSecret_

private ubyte[] masterSecret_

private ubyte[] receivedCookie_

private X25519PrivateKey ecdhePrivate_

private EcdhP256 ecdheP256_

private bool ecdheP256Valid_

private NamedGroup selectedGroup_

private string serverName_

private DtlsVersion minVersion_

private DtlsVersion maxVersion_

private string[] alpnProtocols_

private SrtpProfile[] srtpProfiles_

private string negotiatedAlpn_

private CipherSuiteId negotiatedCipher_

private DtlsVersion negotiatedVersion_

private SrtpProfile negotiatedSrtpProfile_

private Tls12Prf prf_

private TranscriptHash transcript_

private TlsAead writeAead_

private TlsAead readAead_

private X509Certificate[] peerX509Certs_

private TlsCertificateChain peerCerts_

private TlsVerifyMode verifyMode_

private DtlsVerifyCallback verifyCallback_

private NativeTlsTrustStore trustStore_

private DtlsFragmentBuffer reassembly_

private ubyte[65536] recvBuffer_

private ubyte[] pendingDatagram_

Methods

void setMinVersion(DtlsVersion ver) @safe pure nothrow @nogcSets the minimum DTLS version.

void setMaxVersion(DtlsVersion ver) @safe pure nothrow @nogcSets the maximum DTLS version.

void setAlpnProtocols(string[] protocols) @safe pure nothrowSets the ALPN protocols.

void setSrtpProfiles(SrtpProfile[] profiles) @safe pure nothrowSets the DTLS-SRTP profiles to negotiate (RFC 5764).

void setVerifyMode(TlsVerifyMode mode) @safe pure nothrow @nogcSets the certificate verification mode.

void setVerifyCallback(DtlsVerifyCallback callback) @safe pure nothrowSets a custom certificate verification callback.

void setTrustStore(NativeTlsTrustStore trustStore) @safe pure nothrowSets the trust store for certificate chain validation.

TlsProgress handshake() @trustedPerforms or continues the DTLS 1.2 client handshake.

ubyte[] buildDtlsClientHello(const(ubyte)[] cookie)Builds a DTLS ClientHello handshake message.

bool processServerResponse(const(ubyte)[] datagram)Process a received datagram during the handshake.

bool processHandshakePayload(const(ubyte)[] payload)Process a handshake payload from a DTLS record.

bool dispatchHandshakeType(HandshakeType msgType, const(ubyte)[] body)Dispatch a complete handshake message to the appropriate handler.

void processServerHello(const(ubyte)[] body)Process a ServerHello message body.

void processServerHelloExtensions(const(ubyte)[] extData)Process extensions from a ServerHello.

void processCertificate(const(ubyte)[] body)Process a Certificate message body.

private void verifyPeerCertificates()Verify the peer's certificate chain against the trust store.

void processServerKeyExchange(const(ubyte)[] body)Process a ServerKeyExchange message body.

void performKeyExchange(NamedGroup group, const(ubyte)[] peerPubKey)Perform ECDHE key exchange.

void verifyServerKeyExchange(SignatureScheme sigScheme,
           const(ubyte)[]  params,  const(ubyte)[]  signature)

Verify the server's signature on ServerKeyExchange parameters.

ubyte[] buildClientKeyExchange()Builds a ClientKeyExchange handshake message.

ubyte[] buildChangeCipherSpec()Builds a ChangeCipherSpec record.

void deriveKeys()Derives master secret and key material from the premaster secret.

ubyte[] buildFinished()Builds a Finished handshake message.

void processServerFinished(const(ubyte)[] body)Process a server Finished message body.

const(ubyte)[] decryptRecordPayload(const(ubyte)[]  payload,
           DtlsRecordHeader header)

Decrypts an encrypted DTLS 1.2 record payload using the read AEAD.

const(ubyte)[] extractHelloVerifyCookie(const(ubyte)[] body)Extract the cookie from a HelloVerifyRequest body.

void updateTranscript(HandshakeType msgType,  ushort  msgSeq,
           const(ubyte)[]  body)

Update the handshake transcript hash with a DTLS handshake message.

ubyte[] wrapHandshakeMessage(HandshakeType msgType,  const(ubyte)[]  body,
           bool  intoTranscript =  true)

Wraps a handshake message body in a DTLS handshake header.

ubyte[] wrapInRecord(ContentType contentType, const(ubyte)[] payload)Wraps a handshake message in a DTLS record.

ubyte[] buildDtlsRecord(ContentType contentType, const(ubyte)[] payload)Builds a complete DTLS record with 13-byte header.

ubyte[] encryptRecord(ContentType contentType, const(ubyte)[] plaintext)Encrypts a record payload using the current write AEAD.

const(ubyte)[] receiveDatagram()Receive a single datagram from the transport.

void feedDatagram(const(ubyte)[] data) @trustedFeed a received datagram for processing.

void sendDatagram(const(ubyte)[] data)Send a datagram via the transport.

void sendFlight(ubyte[][] records)Send a flight of records as one or more datagrams.

void scheduleRetransmit()Schedule retransmission timer for the current flight.

void retransmitFlight()Retransmit the pending flight.

Dtls12ClientPhase phase() @property const @safe pure nothrow @nogcReturns: The current handshake phase.

CipherSuiteId negotiatedCipher() @property const @safe pure nothrow @nogcReturns: The negotiated cipher suite.

DtlsVersion negotiatedVersion() @property const @safe pure nothrow @nogcReturns: The negotiated DTLS version.

string alpnProtocol() @property const @safe pure nothrowReturns: The negotiated ALPN protocol.

TlsCertificateChain peerCertificates() @property @trustedReturns: The peer's certificate chain.

ushort epoch() @property const @safe pure nothrow @nogcReturns: The current epoch.

ulong recordSeq() @property const @safe pure nothrow @nogcReturns: The next outgoing record sequence number for the current epoch.

SrtpProfile negotiatedSrtpProfile() @property const @safe pure nothrow @nogcReturns: The negotiated DTLS-SRTP profile (`SrtpProfile.init` when SRTP was not negotiated).

ubyte[] srtpMasterSecret() @property @safe pure nothrow @nogc

ubyte[] srtpClientRandom() @property @safe pure nothrow @nogc

ubyte[] srtpServerRandom() @property @safe pure nothrow @nogc

TlsAead writeAead() @propertyReturns: The write AEAD cipher (after key derivation).

TlsAead readAead() @propertyReturns: The read AEAD cipher (after key derivation).

Constructors

this(DtlsTransport transport,  DtlsTimerSink timer,
          DatagramEndpoint serverAddr,  string serverName)

Constructs a DTLS 1.2 client handshake engine.

Variables 1

enumvarDTLS_1_2_RECORD_VERSION = [0xFE, 0xFD]

DTLS 1.2 record version used on the wire.