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|
open Lwt.Syntax
open Lwt.Infix
exception ClosedStream
type features = {
mechanisms : Sasl.auth_mechanism list;
starttls : [`Required | `Optional | `None];
unknown : Xml.element list;
}
(** [parse_features el] is a [features] record with all the features of the
[<stream:features>] stanza contained in [el]. *)
let parse_features (el : Xml.element) : features =
let open Xml in
let open Either in
let parse_mechanism_stanza = function
| Left {local_name = "mechanism"; children = [Right mechanism]; _} ->
Some (Sasl.parse_auth_mechanism mechanism)
| _ -> None
in
let parse_feature (acc : features) (feature : Xml.element) : features =
let parse_mechanisms ch =
List.filter_map parse_mechanism_stanza ch
and parse_starttls = function
| [Left {local_name="required"; _}] -> `Required
| [] -> `Optional
| _ -> raise (InvalidStanza (element_to_string el))
in match feature.local_name with
| "mechanisms" -> {acc with mechanisms=parse_mechanisms feature.children}
| "starttls" -> {acc with starttls=parse_starttls feature.children}
| _ -> {acc with unknown = feature :: acc.unknown}
in List.fold_left
parse_feature
{mechanisms=[]; starttls=`None; unknown=[]}
(List.filter_map find_left el.children)
(** [negotiate domain stream] is a promise containing the features supported by the
XMPP server communicating with [stream].
This function should be called every time a stream needs to be reopened and stream
negotiation takes place.
Basically, it conforms to
{{: https://datatracker.ietf.org/doc/html/rfc6120#section-4.3 }}. *)
let negotiate ?(prefer_starttls = true) (domain : string) (portal : Portal.t) : features Lwt.t =
(* Restart a stream: Send the usual business, ask for features. *)
let start_stream () : features Lwt.t =
let* _id = Portal.header domain portal
in Wire.get portal.stream >|= parse_features
in
let starttls features =
match features.starttls, prefer_starttls with
| `Optional, false | `None, _ -> Lwt.return features
| `Optional, true | `Required, _->
Starttls.upgrade portal >>= start_stream
in start_stream () >>= starttls
(** [initiate domain] initiates a stream with the XMPP server [domain].
Once [None] is pushed into the stream, the receiving stream is drained and the
socket is closed. *)
let initiate (domain : string) : (Portal.t * features) Lwt.t =
let open Portal in
let* p = connect domain
in let push = function
| Some n -> p.push (Some n)
| None ->
p.push (Some close);
(* Empty the stream completely, then close the socket. *)
Lwt.async (fun () -> let+ () = Markup_lwt.drain p.stream in p.push None)
in let portal = {p with push} in
let+ features = negotiate domain portal
in (portal, features)
|
