Tls12Prf.deriveKeyBlock

ubyte[] deriveKeyBlock(const(ubyte)[]  masterSecret,
          const(ubyte)[]  serverRandom,  const(ubyte)[]  clientRandom,
          size_t length)

Derives key material from the master secret.

key_block = PRF(master_secret, "key expansion", ServerHello.random + ClientHello.random)

`masterSecret`	The 48-byte master secret.
`serverRandom`	The ServerHello.random (32 bytes).
`clientRandom`	The ClientHello.random (32 bytes).
`length`	Desired key block length.

Key block bytes.