syssign

static VALUE
ossl_dsa_sign(VALUE self, VALUE data)
{
    EVP_PKEY *pkey;
    unsigned int buf_len;
    VALUE str;

    GetPKeyDSA(self, pkey);
    StringValue(data);
    if (!DSA_PRIVATE(self, pkey->pkey.dsa)) {
        ossl_raise(eDSAError, "Private DSA key needed!");
    }
    str = rb_str_new(0, ossl_dsa_buf_size(pkey));
    if (!DSA_sign(0, (unsigned char *)RSTRING_PTR(data), RSTRING_LEN(data),
                  (unsigned char *)RSTRING_PTR(str),
                  &buf_len, pkey->pkey.dsa)) { /* type is ignored (0) */
        ossl_raise(eDSAError, NULL);
    }
    rb_str_set_len(str, buf_len);

    return str;
}