ddn.net.dtls.cookie

DTLS cookie exchange for DoS mitigation.

Implements the cookie generation and verification mechanism described in RFC 6347 §4.2.1 (DTLS 1.2 HelloVerifyRequest). Cookies prevent spoofed-source denial-of-service attacks by requiring the client to prove it can receive at the claimed address before the server commits expensive resources.

Cookie computation: HMAC-SHA256(serverSecret, clientAddress || clientRandom)

var COOKIE_SECRET_SIZE MAX_COOKIE_SIZE

struct HelloVerifyRequest

fn buildHelloVerifyRequest extractClientHelloCookie generateCookie generateCookieSecret verifyCookie

Types 1

structHelloVerifyRequest

Parsed HelloVerifyRequest message (RFC 6347 §4.2.1).

Contains the server's DTLS version and a cookie that the client must echo back in its retried ClientHello.

Fields

DtlsVersion serverVersionServer's DTLS version.

const(ubyte)[] cookieCookie bytes to echo back.

Methods

HelloVerifyRequest parse(const(ubyte)[] data) @safe pure nothrow @nogcParses a HelloVerifyRequest handshake body (after the 12-byte DTLS handshake header has been stripped).

bool valid() @property const @safe pure nothrow @nogcReturns: true if this instance was successfully parsed.

Functions 5

ubyte[] generateCookie(const(ubyte)[]  serverSecret,  DatagramEndpoint clientAddr,
       const(ubyte)[]  clientRandom)

Generates a stateless cookie for DTLS HelloVerifyRequest.

bool verifyCookie(const(ubyte)[]  cookie,  const(ubyte)[]  serverSecret,
       DatagramEndpoint clientAddr,  const(ubyte)[]  clientRandom)

Verifies a cookie received from a client.

ubyte[] buildHelloVerifyRequest(DtlsVersion serverVersion,  ushort  messageSeq,
       const(ubyte)[]  cookie)

Builds a HelloVerifyRequest message with DTLS handshake header.

fnubyte[] generateCookieSecret(SecureRandom rng)Generates a random cookie secret for server use.

fnconst(ubyte)[] extractClientHelloCookie(const(ubyte)[] clientHelloBody) @safe pure nothrowExtracts the cookie from a DTLS ClientHello message.

Variables 2

enumvarCOOKIE_SECRET_SIZE = 32

Size of the server cookie secret key in bytes.

enumvarMAX_COOKIE_SIZE = 255

Maximum cookie size in bytes (per RFC 6347 §4.2.1: opaque cookie<0..2^8-1>).