OpenSSL::Netscape::SPKI#challenge=

static VALUE
ossl_spki_set_challenge(VALUE self, VALUE str)
{
    NETSCAPE_SPKI *spki;

    StringValue(str);
    GetSPKI(self, spki);
    if (!ASN1_STRING_set(spki->spkac->challenge, RSTRING_PTR(str),
                         RSTRING_LENINT(str))) {
        ossl_raise(eSPKIError, NULL);
    }

    return str;
}