Examples with subrequest

[azoyan]

Is your feature request related to a problem? Please describe.
Show please example of module where we use subrequest with original body to custom own server, handle response and depend on response (403 or 200) return error or continue execution.

I don't know why i have Segfault on my module:

http_request_handler!(wafng_read_post_handler, |request: &mut http::Request| {
    let module = unsafe { addr_of!(NGX_HTTP_WAFNG_MODULE).as_ref().unwrap() };
    let config = request
        .get_module_loc_conf::<ModuleConfig>(module)
        .expect("module config is none");

    if matches!(config.mode, Mode::Off) {
        return Status::NGX_DECLINED;
    }

    let status = request.subrequest("/score", module, subrequest_callback);
}
unsafe extern "C" fn subrequest_callback(
    r: *mut ngx_http_request_t,
    v: *mut c_void,
    i: ngx_int_t,
) -> ngx_int_t {
    let req = unsafe { Request::from_ngx_http_request(r) };
    for (header, value) in req.headers_in_iterator() {
        eprint!("Header = {header}, value = {value}");
    }
    eprintln!("\nRECEIVED SUBREQUEST");
    0
}

[azoyan]

Another words, is it possible to code behavior like this?

const THRESHOLD = 40;
const IS_PROXY_MODE = false;

function score(r) {
    r.subrequest("/score" + r.uri, (response) => {
        const wafReplyJson = JSON.parse(response.responseText);

        if (wafReplyJson.description.length > 0) {
            const weight = wafReplyJson.score.weighted;
            if (IS_PROXY_MODE) {
                r.headersOut['X-Waf-Score'] = weight;
            }
            else {
                if (weight < THRESHOLD) {
                    return r.return(403, "Access Denied\n")
                }
            }
        }
        r.internalRedirect("/backend");
    });
}

export default { score };

This is example of usage njs module.

[Moudoux]

You could recompile NGINX with address sanitation to see why you get the segfault.

I recently attempted to do the exact thing you're trying to do and also got the same issue. I believe it is caused by the subrequest method using NGX_HTTP_SUBREQUEST_WAITED, which means that the output from the subrequest is sent to the original client causing issues with duplicated bodies.

To get around this I copied the code from the subrequest method and made my own with NGX_HTTP_SUBREQUEST_IN_MEMORY instead, since I don't want to send the response of my subrequest to the original client, but rather read it in my module.