pbkdf2_hmac

static VALUE
ossl_pkcs5_pbkdf2_hmac(VALUE self, VALUE pass, VALUE salt, VALUE iter, VALUE keylen, VALUE digest)
{
    VALUE str;
    const EVP_MD *md;
    int len = NUM2INT(keylen);

    StringValue(pass);
    StringValue(salt);
    md = GetDigestPtr(digest);

    str = rb_str_new(0, len);

    if (PKCS5_PBKDF2_HMAC(RSTRING_PTR(pass), RSTRING_LENINT(pass),
                          (unsigned char *)RSTRING_PTR(salt), RSTRING_LENINT(salt),
                          NUM2INT(iter), md, len,
                          (unsigned char *)RSTRING_PTR(str)) != 1)
        ossl_raise(ePKCS5, "PKCS5_PBKDF2_HMAC");

    return str;
}