int tls13_derive_finishedkey(SSL *s, const EVP_MD *md,
                             const unsigned char *secret,
                             unsigned char *fin, size_t finlen)
{
    static const unsigned char finishedlabel[] = "finished";

    return tls13_hkdf_expand(s, md, secret, finishedlabel,
                             sizeof(finishedlabel) - 1, NULL, 0, fin, finlen, 1);
}