OpenSSL::X509::Attribute#value=

static VALUE
ossl_x509attr_set_value(VALUE self, VALUE value)
{
    X509_ATTRIBUTE *attr;
    GetX509Attr(self, attr);

    OSSL_Check_Kind(value, cASN1Data);
    VALUE der = ossl_to_der(value);
    const unsigned char *p = (const unsigned char *)RSTRING_PTR(der);
    STACK_OF(ASN1_TYPE) *sk = d2i_ASN1_SET_ANY(NULL, &p, RSTRING_LEN(der));
    if (!sk)
        ossl_raise(eX509AttrError, "attribute value must be ASN1::Set");

    if (X509_ATTRIBUTE_count(attr)) { /* populated, reset first */
        ASN1_OBJECT *obj = X509_ATTRIBUTE_get0_object(attr);
        X509_ATTRIBUTE *new_attr = X509_ATTRIBUTE_create_by_OBJ(NULL, obj, 0, NULL, -1);
        if (!new_attr) {
            sk_ASN1_TYPE_pop_free(sk, ASN1_TYPE_free);
            ossl_raise(eX509AttrError, "X509_ATTRIBUTE_create_by_OBJ");
        }
        SetX509Attr(self, new_attr);
        X509_ATTRIBUTE_free(attr);
        attr = new_attr;
    }

    for (int i = 0; i < sk_ASN1_TYPE_num(sk); i++) {
        ASN1_TYPE *a1type = sk_ASN1_TYPE_value(sk, i);
        if (!X509_ATTRIBUTE_set1_data(attr, ASN1_TYPE_get(a1type),
                                      a1type->value.ptr, -1)) {
            sk_ASN1_TYPE_pop_free(sk, ASN1_TYPE_free);
            ossl_raise(eX509AttrError, "X509_ATTRIBUTE_set1_data");
        }
    }
    sk_ASN1_TYPE_pop_free(sk, ASN1_TYPE_free);

    return value;
}