%%% @doc MASQUE CONNECT-UDP proxy listener.
%%%
%%% Two public entry points:
%%%
%%% <ul>
%%% <li>{@link start_listener/2} starts a dedicated `quic_h3' server
%%% that handles MASQUE end-to-end; the usual case for a pure
%%% MASQUE proxy.</li>
%%% <li>{@link h3_handlers/1} returns the `handler' and
%%% `connection_handler' functions that a caller can splat into
%%% their own `quic_h3:start_server/3' opts. This lets users who
%%% already run an HTTP/3 service add CONNECT-UDP support without
%%% giving up ownership of the listener; non-MASQUE requests can
%%% be routed to a `fallback' fun.</li>
%%% </ul>
%%%
%%% For each inbound request the handler validates the Extended
%%% CONNECT envelope per RFC 9298, matches the `:path' against the
%%% configured URI template, and either accepts the tunnel (2xx
%%% response, stream left open for subsequent datagrams) or rejects
%%% with the HTTP status selected by `masque_errors:handshake_status/1'
%%% (or defers to the caller's `fallback' fun when provided).
-module(masque_server).
-export([
start_listener/2,
stop_listener/1,
h3_handlers/1
]).
-include("masque.hrl").
-include("masque_ip.hrl").
-type listener_name() :: atom().
-type listener_opts() :: masque:listener_opts().
-type h3_handler_fun() ::
fun((Conn :: pid(), StreamId :: non_neg_integer(),
Method :: binary(), Path :: binary(),
Headers :: [{binary(), binary()}]) -> any()).
-type connection_handler_fun() :: fun((pid()) -> map()).
-export_type([listener_name/0, listener_opts/0,
h3_handler_fun/0, connection_handler_fun/0]).
%%====================================================================
%% API
%%====================================================================
%% @doc Start a MASQUE listener as a dedicated `quic_h3' server.
%%
%% Required keys: `port', `cert', `key' (DER-encoded, same shape as
%% `quic_h3:start_server/3' expects). Optional `uri_template' defaults
%% to RFC 9298's well-known path; optional `handler' defaults to
%% `masque_udp_proxy_handler'; optional `fallback' is invoked for
%% requests that are not CONNECT-UDP tunnels (see `h3_handlers/1').
-spec start_listener(listener_name(), listener_opts()) ->
{ok, pid()} | {error, term()}.
start_listener(Name, Opts0) when is_atom(Name), is_map(Opts0) ->
persistent_term:erase({masque_drain, Name}),
Opts = defaults(Opts0),
Port = maps:get(port, Opts),
#{handler := Handler,
connection_handler := ConnectionHandler} =
h3_handlers(Opts#{drain_key => Name}),
ServerOpts = #{
cert => maps:get(cert, Opts),
key => maps:get(key, Opts),
settings => merged_settings(Opts),
%% `alpn' and `max_datagram_frame_size' are not declared keys
%% on `quic_h3:server_opts()' - they belong in `quic_opts'.
quic_opts => build_quic_opts(Opts),
handler => Handler,
connection_handler => ConnectionHandler
},
quic_h3:start_server(Name, Port, ServerOpts).
build_quic_opts(Opts) ->
Base = #{
alpn => maps:get(alpn, Opts, [<<"h3">>]),
max_datagram_frame_size =>
maps:get(max_datagram_frame_size, Opts, 65535)
},
%% SO_REUSEPORT lets the OS spread incoming packets across N
%% listener processes for kernel-level scaling.
case maps:get(reuseport, Opts, false) of
true -> Base#{reuseport => true};
false -> Base
end.
%% @doc Stop a MASQUE listener.
-spec stop_listener(listener_name()) -> ok | {error, term()}.
stop_listener(Name) ->
persistent_term:erase({masque_drain, Name}),
quic_h3:stop_server(Name).
%% @doc Return the `handler' and `connection_handler' functions for a
%% MASQUE proxy, in a shape that can be dropped into a user-owned
%% `quic_h3:start_server/3' call.
%%
%% Accepted keys (all optional unless noted):
%% <ul>
%% <li>`uri_template' - RFC 6570 template, default the RFC 9298
%% well-known path template.</li>
%% <li>`handler' - module implementing the {@link masque_handler}
%% behaviour, default `masque_udp_proxy_handler'.</li>
%% <li>`handler_opts' - arbitrary term passed to the handler module's
%% `init/2' callback.</li>
%% <li>`fallback' - `fun(Conn, StreamId, Method, Path, Headers) -> any()'
%% invoked when the request is not a CONNECT-UDP tunnel. Absent
%% → non-MASQUE requests are rejected with 405/501/404 as
%% appropriate.</li>
%% </ul>
%%
%% Caveat: MASQUE must be the H3 connection's `owner' (HTTP Datagrams
%% are delivered to that pid), so the returned `connection_handler'
%% overrides the listener-wide owner. Sharing a single `quic_h3'
%% connection with another extension that also needs the `owner' slot
%% (e.g. WebTransport) is not supported in v0.1; run those on separate
%% listeners.
-spec h3_handlers(map()) ->
#{handler := h3_handler_fun(),
connection_handler := connection_handler_fun()}.
h3_handlers(Opts0) ->
Opts = defaults(Opts0),
UdpTemplate = maps:get(uri_template, Opts),
TcpTemplate = maps:get(tcp_uri_template, Opts),
IpTemplate = maps:get(ip_uri_template, Opts),
UdpHandler = maps:get(handler, Opts),
TcpHandler = maps:get(tcp_handler, Opts),
IpHandler = maps:get(ip_handler, Opts),
BindHandler = maps:get(bind_handler, Opts),
AcceptBind = maps:get(accept_bind, Opts),
Resolver = maps:get(resolver, Opts, fun default_resolver/1),
%% Lift IP-scoped listener options into handler_opts so the
%% default IP handler (and user handlers that follow the same
%% convention) see them without callers having to duplicate.
IpExtra = maps:with([address_pool, routes, mtu,
resolver, allow, family, allow_private,
connect_timeout, socket_opts], Opts),
%% Same for bind-scoped opts.
BindExtra = maps:with([bind_address, bind_port, bind_socket_opts,
public_addresses, public_address_fun,
peer_filter_fun, scrub_fun, allow_private,
allow_loopback,
max_compression_contexts,
max_compression_contexts_in,
max_compression_contexts_out,
max_pending_compression_responses], Opts),
UserHOpts = maps:get(handler_opts, Opts, #{}),
HandlerOpts = maps:merge(maps:merge(IpExtra, BindExtra), UserHOpts),
Fallback = maps:get(fallback, Opts, undefined),
DrainKey = maps:get(drain_key, Opts, undefined),
Dispatch = #{udp_template => UdpTemplate, tcp_template => TcpTemplate,
ip_template => IpTemplate,
udp_handler => UdpHandler, tcp_handler => TcpHandler,
ip_handler => IpHandler,
bind_handler => BindHandler,
accept_bind => AcceptBind,
resolver => Resolver,
handler_opts => HandlerOpts, fallback => Fallback,
name => DrainKey},
MaxTunnels = maps:get(max_tunnels_per_connection, Opts, 0),
ConnectionHandler = fun(_ConnPid) ->
{ok, Router} = masque_server_connection:start_link(MaxTunnels),
#{
owner => Router,
handler => make_dispatch_fun(Dispatch, Router),
h3_datagram_enabled => true
}
end,
#{
handler => make_dispatch_fun(Dispatch, undefined),
connection_handler => ConnectionHandler
}.
%%====================================================================
%% Internal
%%====================================================================
defaults(Opts) ->
D = #{
uri_template => ?MASQUE_DEFAULT_URI_TEMPLATE,
tcp_uri_template => ?MASQUE_DEFAULT_TCP_URI_TEMPLATE,
ip_uri_template => ?MASQUE_DEFAULT_IP_URI_PATH_PATTERN,
handler => masque_udp_proxy_handler,
tcp_handler => masque_tcp_proxy_handler,
ip_handler => masque_ip_proxy_handler,
bind_handler => masque_udp_bind_proxy_handler,
accept_bind => false
},
maps:merge(D, Opts).
%% Default resolver: resolve A and AAAA, merge results.
default_resolver(Host) when is_binary(Host) ->
default_resolver(binary_to_list(Host));
default_resolver(Host) when is_list(Host) ->
V4 = case inet_res:lookup(Host, in, a) of
[] -> []; Xs -> Xs
end,
V6 = case inet_res:lookup(Host, in, aaaa) of
[] -> []; Ys -> Ys
end,
case V4 ++ V6 of
[] -> {error, nxdomain};
Addrs -> {ok, Addrs}
end.
%% MASQUE requires `SETTINGS_ENABLE_CONNECT_PROTOCOL = 1' and
%% `SETTINGS_H3_DATAGRAM = 1'. Merge these on top of any user-supplied
%% settings rather than clobbering them.
merged_settings(Opts) ->
User = maps:get(settings, Opts, #{}),
maps:merge(User, #{
enable_connect_protocol => 1,
h3_datagram => 1
}).
make_dispatch_fun(Dispatch, Router) ->
fun(Conn, StreamId, Method, Path, Headers) ->
dispatch_request(Conn, StreamId, Method, Path, Headers,
Dispatch, Router)
end.
dispatch_request(Conn, StreamId, Method, Path, Headers, Dispatch, Router) ->
case masque:is_draining(maps:get(name, Dispatch, undefined)) of
true ->
reject(Conn, StreamId, overload);
false ->
dispatch_request_1(Conn, StreamId, Method, Path, Headers,
Dispatch, Router)
end.
dispatch_request_1(Conn, StreamId, Method, Path, Headers, Dispatch, Router) ->
#{udp_template := UdpTpl, tcp_template := TcpTpl,
ip_template := IpTpl,
udp_handler := UdpHandler, tcp_handler := TcpHandler,
ip_handler := IpHandler,
bind_handler := BindHandler,
accept_bind := AcceptBind,
resolver := Resolver,
handler_opts := HandlerOpts, fallback := Fallback} = Dispatch,
case validate(Method, Path, Headers, UdpTpl, TcpTpl, IpTpl,
AcceptBind) of
{ok, Req0} ->
Protocol = maps:get(protocol, Req0),
HandlerMod = case Protocol of
udp -> UdpHandler;
tcp -> TcpHandler;
ip -> IpHandler;
udp_bind -> BindHandler
end,
Req1 = add_peer_info(Conn, Req0),
Req2 = Req1#{handler_opts => HandlerOpts},
case resolve_target(Protocol, Req2, Resolver) of
{ok, Req3} ->
case accept_request(HandlerMod, Req3) of
accept ->
spawn_session(Conn, StreamId, Router, Protocol,
HandlerMod, HandlerOpts, Req3);
{reject, Reason} ->
reject(Conn, StreamId, Reason);
{reject, Reason, Extra} when is_list(Extra) ->
reject(Conn, StreamId, Reason, Extra)
end;
{error, Reason} ->
reject(Conn, StreamId, Reason)
end;
{error, Reason} ->
case Fallback of
undefined ->
reject(Conn, StreamId, Reason);
Fun when is_function(Fun, 5) ->
Fun(Conn, StreamId, Method, Path, Headers)
end
end.
%% RFC 9484 §4.7.1: hostname targets MUST be resolved before the 2xx
%% response. The resolved address list is attached to `req()` so the
%% handler's `accept/1' can apply SSRF policy on the real addresses
%% and the session's `init/2' gets them ready to emit in the first
%% ROUTE_ADVERTISEMENT.
resolve_target(ip, #{ip_target := Target} = Req, Resolver)
when is_binary(Target) ->
%% Binary ip_target is a hostname (IPs parse into tuples).
case Resolver(Target) of
{ok, Addrs} -> {ok, Req#{resolved_addresses => Addrs}};
{error, _} -> {error, resolution_failed}
end;
resolve_target(ip, #{ip_target := {_,_,_,_} = A} = Req, _Resolver) ->
{ok, Req#{resolved_addresses => [A]}};
resolve_target(ip, #{ip_target := {_,_,_,_,_,_,_,_} = A} = Req, _Resolver) ->
{ok, Req#{resolved_addresses => [A]}};
resolve_target(ip, Req, _Resolver) ->
{ok, Req#{resolved_addresses => []}};
resolve_target(_, Req, _Resolver) ->
{ok, Req}.
spawn_session(Conn, StreamId, undefined, _Proto, _Handler, _HOpts, _Req) ->
reject(Conn, StreamId, resolution_failed);
spawn_session(Conn, StreamId, Router, Protocol, Handler, HOpts, Req) ->
Args = #{conn => Conn, stream_id => StreamId, router => Router,
protocol => Protocol, transport => h3,
handler => Handler, handler_opts => HOpts, req => Req},
try masque_server_connection:start_session(Router, Args) of
{ok, _Pid} -> ok;
{error, Reason} -> reject(Conn, StreamId, map_init_error(Reason))
catch
exit:{timeout, _} ->
case masque_server_connection:cancel_pending(Router, StreamId) of
ok ->
reject(Conn, StreamId, resolution_failed);
{error, already_activated} ->
%% Session started after timeout. Tunnel is live.
ok
end
end.
add_peer_info(Conn, Req) ->
QuicConn = quic_h3:get_quic_conn(Conn),
Req1 = case quic:peername(QuicConn) of
{ok, PeerAddr} -> Req#{peer => PeerAddr};
_ -> Req
end,
case quic:peercert(QuicConn) of
{ok, Cert} -> Req1#{peer_cert => Cert};
_ -> Req1
end.
map_init_error(too_many_tunnels) -> overload;
map_init_error({resolution_failed, _}) -> resolution_failed;
map_init_error({reject, Err}) -> Err;
map_init_error(_) -> resolution_failed.
%% `AcceptBind' is the listener-level switch for Connect-UDP-Bind
%% (draft-ietf-masque-connect-udp-listen-11). When true, the
%% `connect-udp' branch additionally inspects the
%% `Connect-UDP-Bind' request header and routes to the bind matcher
%% on `?1'. When false (the default), the header is ignored and
%% legacy CONNECT-UDP behaviour is unchanged.
validate(Method, Path, Headers, UdpTemplate, TcpTemplate, IpTemplate,
AcceptBind) ->
case Method of
<<"CONNECT">> ->
Protocol = header(<<":protocol">>, Headers),
case Protocol of
?MASQUE_CONNECT_UDP_PROTOCOL when AcceptBind ->
match_udp_or_bind(Path, Headers, UdpTemplate);
?MASQUE_CONNECT_UDP_PROTOCOL ->
match_path(Path, Headers, UdpTemplate, udp);
?MASQUE_CONNECT_TCP_PROTOCOL ->
match_path(Path, Headers, TcpTemplate, tcp);
?MASQUE_CONNECT_IP_PROTOCOL ->
match_ip_path(Path, Headers, IpTemplate);
_ ->
{error, bad_protocol}
end;
_ ->
{error, bad_method}
end.
%% Read `Connect-UDP-Bind' first; on `?1' use the bind matcher
%% which accepts the percent-encoded `*' wildcard. Otherwise fall
%% through to the existing CONNECT-UDP path. Per draft-11, an
%% invalid value is treated as absent.
match_udp_or_bind(Path, Headers, Template) ->
case masque_uri_udp_bind:parse_bind_header(Headers) of
bind ->
case masque_uri_udp_bind:match(Template, Path) of
{ok, #{target_host := Host, target_port := Port,
bind := Scope}} ->
case {header(<<":scheme">>, Headers),
header(<<":authority">>, Headers)} of
{Scheme, Authority}
when Scheme =/= undefined,
Authority =/= undefined ->
{ok, #{
method => <<"CONNECT">>,
protocol => udp_bind,
bind => Scope,
path => Path,
authority => Authority,
scheme => Scheme,
target_host => Host,
target_port => Port,
headers => Headers
}};
_ ->
{error, bad_path}
end;
{error, bad_port} -> {error, bad_port};
{error, bad_host} -> {error, bad_host};
{error, _} -> {error, bad_path}
end;
_ ->
match_path(Path, Headers, Template, udp)
end.
match_path(Path, Headers, Template, Protocol) ->
case masque_uri:match(Template, Path) of
{ok, #{target_host := Host, target_port := Port}} ->
%% `:scheme' and `:authority' presence is enforced by
%% `quic_h3' for Extended CONNECT; we surface whatever it
%% delivers without silently substituting defaults.
case {header(<<":scheme">>, Headers),
header(<<":authority">>, Headers)} of
{Scheme, Authority} when Scheme =/= undefined,
Authority =/= undefined ->
{ok, #{
method => <<"CONNECT">>,
protocol => Protocol,
path => Path,
authority => Authority,
scheme => Scheme,
target_host => Host,
target_port => Port,
headers => Headers
}};
_ ->
{error, bad_path}
end;
{error, bad_port} ->
{error, bad_port};
{error, bad_host} ->
{error, bad_host};
{error, _} ->
{error, bad_path}
end.
match_ip_path(Path, Headers, Template) ->
case masque_uri_ip:parse_server_template(Template) of
{ok, T} ->
case masque_uri_ip:match(T, Path) of
{ok, #{target := Target, ipproto := IPProto}} ->
case {header(<<":scheme">>, Headers),
header(<<":authority">>, Headers)} of
{Scheme, Authority}
when Scheme =/= undefined,
Authority =/= undefined ->
{ok, #{
method => <<"CONNECT">>,
protocol => ip,
path => Path,
authority => Authority,
scheme => Scheme,
ip_target => Target,
ip_ipproto => IPProto,
headers => Headers
}};
_ ->
{error, bad_path}
end;
{error, bad_target} -> {error, bad_host};
{error, bad_ipproto} -> {error, bad_port};
{error, _} -> {error, bad_path}
end;
{error, _} ->
{error, bad_path}
end.
accept_request(HandlerMod, Req) ->
_ = code:ensure_loaded(HandlerMod),
case erlang:function_exported(HandlerMod, accept, 1) of
true -> HandlerMod:accept(Req);
false -> masque_handler:default_accept(Req)
end.
reject(Conn, StreamId, Reason) ->
reject(Conn, StreamId, Reason, []).
reject(Conn, StreamId, Reason, ExtraHeaders) ->
masque_metrics:tunnel_rejected(#{reason => Reason}),
Status = masque_errors:handshake_status(Reason),
Phrase = masque_errors:status_reason(Reason),
Body = <<Phrase/binary, "\n">>,
Base = [
{<<"content-type">>, <<"text/plain; charset=utf-8">>},
{<<"content-length">>, integer_to_binary(byte_size(Body))},
%% RFC 9209 structured field - gives clients a machine-readable
%% tag for the failure beyond the numeric status (RFC 9298 §3
%% recommendation).
{<<"proxy-status">>, proxy_status_field(Reason)}
],
Headers = merge_extra_headers(Base, ExtraHeaders),
ok = quic_h3:send_response(Conn, StreamId, Status, Headers),
ok = quic_h3:send_data(Conn, StreamId, Body, true).
%% Caller-supplied headers win on collision so apps can override the
%% proxy-status / content-type defaults. Order: ExtraHeaders first
%% (caller-visible), then whatever base entries remain.
merge_extra_headers(Base, []) ->
Base;
merge_extra_headers(Base, Extra) ->
Keys = [K || {K, _} <- Extra],
Kept = [Pair || {K, _} = Pair <- Base, not lists:member(K, Keys)],
Extra ++ Kept.
%% Map MASQUE handshake errors to a minimal Proxy-Status structured
%% field value. We use `masque' as the proxy identifier and attach an
%% RFC 9209 `error' parameter naming the failure class.
proxy_status_field(Reason) ->
Error = proxy_status_error(Reason),
<<"masque; error=", Error/binary>>.
proxy_status_error(bad_method) -> <<"http_protocol_error">>;
proxy_status_error(bad_protocol) -> <<"http_protocol_error">>;
proxy_status_error(bad_path) -> <<"http_protocol_error">>;
proxy_status_error(bad_port) -> <<"http_protocol_error">>;
proxy_status_error(bad_host) -> <<"http_protocol_error">>;
proxy_status_error(resolution_failed) -> <<"dns_error">>;
proxy_status_error(upstream_timeout) -> <<"connection_timeout">>;
proxy_status_error(forbidden) -> <<"destination_ip_prohibited">>;
proxy_status_error(loop_detected) -> <<"proxy_loop_detected">>;
proxy_status_error(overload) -> <<"proxy_internal_error">>;
proxy_status_error(_) -> <<"proxy_internal_error">>.
header(Name, Headers) ->
header(Name, Headers, undefined).
header(Name, Headers, Default) ->
case lists:keyfind(Name, 1, Headers) of
{_, V} -> V;
false -> Default
end.