processing a request without body

[Muhammad Nuzaihan]

Hi Maxim,

Sorry for asking too many questions.

I did looked at he mirror module and i couldn't find the code which
reads the body (from what i understand i need a ngx_chain_t type of
value to build the request body from buffer)
https://github.com/nginx/nginx/blob/master/src/http/modules/ngx_http_mirror_module.c

I'm going with point 1. I know it will break proxying but it's more
simpler and i can think of doing 2. later on.

Thank you,
Zaihan

On Thu, Dec 21, 2023 at 8:59 AM Maxim Dounin <mdounin at mdounin.ru> wrote:
>
> Hello!
>
> On Tue, Dec 19, 2023 at 10:11:04PM +0800, Muhammad Nuzaihan wrote:
>
> > Thanks Maxim, Vasility,
> >
> > The problem i was going to solve is to i needed to run my specific
> > function that takes  the data of request URL path, Headers and request
> > body and determine and validate that all that data is correct before
> > sending upstream, or else i would deny the request with 4xx code
> > errors.
> >
> > Handlers can only handle (from what i know) URL path and headers.
> >
> > Request body requires a request chain (ngx_chain_t)) to piece out the
> > request body and handlers doesn't seem to have t ngx_chain_t unlike
> > request body filters.
> >
> > Or maybe i am wrong in this case?
>
> It looks like you are trying to do something which simply cannot
> be done.  For example, consider a configuration with
> "proxy_request_buffering off;" - in such a configuration request
> body is being read _after_ the request is passed to the upstream
> server, and you simply cannot validate request body before passing
> request headers to the upstream server.
>
> As long as you have to examine both request body and request
> headers, I think there can be two possible solutions:
>
> 1. Install a phase handler, in which read the request body
> yourself, and check both request headers and request body once
> it's read.  See the mirror module as an example on how to read the
> body in a phase handler and properly resume processing after it.
> This will break proxying without request buffering, though might
> be good enough for your particular task.
>
> 2. Install a phase handler to check request headers, and a request
> body filter to check the request body.  Do checking in both
> places, and abort request processing when you see that data aren't
> correct.  This will work with proxying without request buffering,
> but will be generally more complex to implement.  And, obviously,
> this in case of proxying without request buffering this won't let
> you to validate request body before the request headers are sent
> to upstream server.
>
> Hope this helps.
>
> --
> Maxim Dounin
> http://mdounin.ru/
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