TLS tunnel over Lwt_io.channel

src/conduit-lwt-unix/conduit_lwt_tls.dummy.ml

@@ -9,6 +9,9 @@ end
 module Client = struct
   let connect ?src:_ ?certificates:_ ~authenticator:_ _host _sa =
     failwith "Tls not available"
+
+  let tunnel ?certificates:_ ~authenticator:_ _host _ioc =
+    failwith "Tls not available"
 end
 
 module Server = struct

src/conduit-lwt-unix/conduit_lwt_tls.dummy.mli

@@ -33,6 +33,13 @@ module Client : sig
     [ `host ] Domain_name.t ->
     Lwt_unix.sockaddr ->
     (Lwt_unix.file_descr * Lwt_io.input_channel * Lwt_io.output_channel) Lwt.t
+
+  val tunnel :
+    ?certificates:'a ->
+    authenticator:X509.authenticator ->
+    [ `host ] Domain_name.t ->
+    Lwt_io.input_channel * Lwt_io.output_channel ->
+    (Lwt_io.input_channel * Lwt_io.output_channel) Lwt.t
 end
 
 module Server : sig

src/conduit-lwt-unix/conduit_lwt_tls.real.ml

@@ -30,19 +30,27 @@ module X509 = struct
 end
 
 module Client = struct
+  let config ?certificates authenticator =
+    match Tls.Config.client ~authenticator ?certificates () with
+    | Error (`Msg msg) -> failwith ("tls configuration problem: " ^ msg)
+    | Ok config -> config
+
   let connect ?src ?certificates ~authenticator host sa =
     Conduit_lwt_server.with_socket sa (fun fd ->
         (match src with
         | None -> Lwt.return_unit
         | Some src_sa -> Lwt_unix.bind fd src_sa)
         >>= fun () ->
-        match Tls.Config.client ~authenticator ?certificates () with
-        | Error (`Msg msg) -> failwith ("tls configuration problem: " ^ msg)
-        | Ok config ->
-            Lwt_unix.connect fd sa >>= fun () ->
-            Tls_lwt.Unix.client_of_fd config ~host fd >|= fun t ->
-            let ic, oc = Tls_lwt.of_t t in
-            (fd, ic, oc))
+        let config = config ?certificates authenticator in
+        Lwt_unix.connect fd sa >>= fun () ->
+        Tls_lwt.Unix.client_of_fd config ~host fd >|= fun t ->
+        let ic, oc = Tls_lwt.of_t t in
+        (fd, ic, oc))
+
+  let tunnel ?certificates ~authenticator host channels =
+    let config = config ?certificates authenticator in
+    Tls_lwt.Unix.client_of_channels config ~host channels >|= fun t ->
+    Tls_lwt.of_t t
 end
 
 module Server = struct

src/conduit-lwt-unix/conduit_lwt_tls.real.mli

@@ -34,6 +34,13 @@ module Client : sig
     [ `host ] Domain_name.t ->
     Lwt_unix.sockaddr ->
     (Lwt_unix.file_descr * Lwt_io.input_channel * Lwt_io.output_channel) Lwt.t
+
+  val tunnel :
+    ?certificates:Tls.Config.own_cert ->
+    authenticator:X509.authenticator ->
+    [ `host ] Domain_name.t ->
+    Lwt_io.input_channel * Lwt_io.output_channel ->
+    (Lwt_io.input_channel * Lwt_io.output_channel) Lwt.t
 end
 
 module Server : sig

src/conduit-lwt-unix/conduit_lwt_unix.ml

@@ -52,15 +52,16 @@ let () =
       (Sexplib0.Sexp.to_string (sexp_of_tls_lib !tls_library))
 
 type +'a io = 'a Lwt.t
-type ic = Lwt_io.input_channel
-type oc = Lwt_io.output_channel
+type ic = (Lwt_io.input_channel[@sexp.opaque]) [@@deriving sexp]
+type oc = (Lwt_io.output_channel[@sexp.opaque]) [@@deriving sexp]
 
 type client_tls_config =
   [ `Hostname of string ] * [ `IP of Ipaddr_sexp.t ] * [ `Port of int ]
 [@@deriving sexp]
 
 type client =
   [ `TLS of client_tls_config
+  | `TLS_tunnel of [ `Hostname of string ] * ic * oc
   | `TLS_native of client_tls_config
   | `OpenSSL of client_tls_config
   | `TCP of [ `IP of Ipaddr_sexp.t ] * [ `Port of int ]
@@ -140,6 +141,7 @@ type vchan_flow = { domid : int; port : string } [@@deriving sexp]
 
 type flow =
   | TCP of tcp_flow
+  | Tunnel
   | Domain_socket of domain_flow
   | Vchan of vchan_flow
 [@@deriving sexp]
@@ -262,31 +264,41 @@ let set_max_active maxactive = Conduit_lwt_server.set_max_active maxactive
 
 (** TLS client connection functions *)
 
-let connect_with_tls_native ~ctx (`Hostname hostname, `IP ip, `Port port) =
-  let sa = Unix.ADDR_INET (Ipaddr_unix.to_inet_addr ip, port) in
-  (match ctx.tls_own_key with
+let certificates ~ctx =
+  match ctx.tls_own_key with
   | `None -> Lwt.return_none
   | `TLS (_, _, `Password _) ->
       failwith "OCaml-TLS cannot handle encrypted pem files"
   | `TLS (`Crt_file_path cert, `Key_file_path priv_key, `No_password) ->
       Conduit_lwt_tls.X509.private_of_pems ~cert ~priv_key
-      >|= fun certificate -> Some (`Single certificate))
-  >>= fun certificates ->
-  let hostname =
-    try Domain_name.(host_exn (of_string_exn hostname))
-    with Invalid_argument msg ->
-      let s =
-        Printf.sprintf "couldn't convert %s to a [`host] Domain_name.t: %s"
-          hostname msg
-      in
-      invalid_arg s
-  in
+      >|= fun certificate -> Some (`Single certificate)
+
+let domain_name hostname =
+  try Domain_name.(host_exn (of_string_exn hostname))
+  with Invalid_argument msg ->
+    let s =
+      Printf.sprintf "couldn't convert %s to a [`host] Domain_name.t: %s"
+        hostname msg
+    in
+    invalid_arg s
+
+let connect_with_tls_native ~ctx (`Hostname hostname, `IP ip, `Port port) =
+  let sa = Unix.ADDR_INET (Ipaddr_unix.to_inet_addr ip, port) in
+  certificates ~ctx >>= fun certificates ->
+  let hostname = domain_name hostname in
   Conduit_lwt_tls.Client.connect ?src:ctx.src ?certificates
     ~authenticator:ctx.tls_authenticator hostname sa
   >|= fun (fd, ic, oc) ->
   let flow = TCP { fd; ip; port } in
   (flow, ic, oc)
 
+let connect_with_tls_tunnel ~ctx (`Hostname hostname, ic, oc) =
+  certificates ~ctx >>= fun certificates ->
+  let hostname = domain_name hostname in
+  Conduit_lwt_tls.Client.tunnel ?certificates
+    ~authenticator:ctx.tls_authenticator hostname (ic, oc)
+  >|= fun (ic, oc) -> (Tunnel, ic, oc)
+
 let connect_with_openssl ~ctx (`Hostname host_addr, `IP ip, `Port port) =
   let sa = Unix.ADDR_INET (Ipaddr_unix.to_inet_addr ip, port) in
   let ctx_ssl =
@@ -331,6 +343,7 @@ let connect ~ctx (mode : client) =
       let flow = Domain_socket { fd; path } in
       Lwt.return (flow, ic, oc)
   | `TLS c -> connect_with_default_tls ~ctx c
+  | `TLS_tunnel c -> connect_with_tls_tunnel ~ctx c
   | `OpenSSL c -> connect_with_openssl ~ctx c
   | `TLS_native c -> connect_with_tls_native ~ctx c
   | `Vchan_direct _ -> failwith "Vchan_direct not available on unix"
@@ -416,6 +429,7 @@ let serve ?backlog ?timeout ?stop ~on_exn ~(ctx : ctx) ~(mode : server) callback
 
 let endp_of_flow = function
   | TCP { ip; port; _ } -> `TCP (ip, port)
+  | Tunnel -> `Unknown "TLS tunnel"
   | Domain_socket { path; _ } -> `Unix_domain_socket path
   | Vchan { domid; port } -> `Vchan_direct (domid, port)
 

src/conduit-lwt-unix/conduit_lwt_unix.mli

@@ -28,6 +28,8 @@ type client_tls_config =
 
 type client =
   [ `TLS of client_tls_config
+  | `TLS_tunnel of
+    [ `Hostname of string ] * Lwt_io.input_channel * Lwt_io.output_channel
   | `TLS_native of client_tls_config
     (** Force use of native OCaml TLS stack to connect.*)
   | `OpenSSL of client_tls_config
@@ -104,8 +106,8 @@ type server =
       documentation for more. *)
 
 type 'a io = 'a Lwt.t
-type ic = Lwt_io.input_channel
-type oc = Lwt_io.output_channel
+type ic = (Lwt_io.input_channel[@sexp.opaque]) [@@deriving sexp]
+type oc = (Lwt_io.output_channel[@sexp.opaque]) [@@deriving sexp]
 
 type tcp_flow = private {
   fd : Lwt_unix.file_descr; [@sexp.opaque]
@@ -129,6 +131,7 @@ type vchan_flow = private { domid : int; port : string } [@@deriving sexp_of]
     transport method. *)
 type flow = private
   | TCP of tcp_flow
+  | Tunnel
   | Domain_socket of domain_flow
   | Vchan of vchan_flow
 [@@deriving sexp_of]

tests/conduit-lwt-unix/dune

@@ -1,6 +1,6 @@
 (executables
  (libraries lwt_ssl ssl conduit-lwt-unix lwt_log)
- (names cdtest cdtest_tls exit_test))
+ (names cdtest cdtest_tls exit_test tls_over_tls))
 
 (rule
  (alias runtest)

tests/conduit-lwt-unix/tls_over_tls.ml

@@ -0,0 +1,61 @@
+open Lwt.Infix
+
+let hostname = "mirage.io"
+
+(* To test TLS-over-TLS, the `squid` proxy can be installed locally and configured to support HTTPS:
+
+   - Generate a certificate for localhost: https://gist.github.com/cecilemuller/9492b848eb8fe46d462abeb26656c4f8
+
+   $ openssl req -x509 -nodes -new -sha256 -days 1024 -newkey rsa:2048 -keyout RootCA.key -out RootCA.pem -subj "/C=US/CN=Example-Root-CA"
+   $ openssl x509 -outform pem -in RootCA.pem -out RootCA.crt
+   $ cat > domains.ext
+   authorityKeyIdentifier=keyid,issuer
+   basicConstraints=CA:FALSE
+   keyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment
+   subjectAltName = @alt_names
+   [alt_names]
+   DNS.1 = localhost
+   $ openssl req -new -nodes -newkey rsa:2048 -keyout localhost.key -out localhost.csr -subj "/C=US/ST=YourState/L=YourCity/O=Example-Certificates/CN=localhost.local"
+   $ openssl x509 -req -sha256 -days 1024 -in localhost.csr -CA RootCA.pem -CAkey RootCA.key -CAcreateserial -extfile domains.ext -out localhost.crt
+
+   - Configure squid by adding HTTPS support on port 3129 in /etc/squid/squid.conf :
+
+   https_port 3129 tls-cert=/path/to/localhost.crt tls-key=/path/to/localhost.key
+*)
+
+let proxy =
+  `TLS
+    (`Hostname "localhost", `IP (Ipaddr.of_string_exn "127.0.0.1"), `Port 3129)
+
+let string_prefix ~prefix msg =
+  let len = String.length prefix in
+  String.length msg >= len && String.sub msg 0 len = prefix
+
+let main () =
+  let ctx = Lazy.force Conduit_lwt_unix.default_ctx in
+  Conduit_lwt_unix.connect ~ctx proxy >>= fun (_flow, ic, oc) ->
+  let req =
+    String.concat "\r\n"
+      [ "CONNECT " ^ hostname ^ ":443 HTTP/1.1"; "Host: " ^ hostname; ""; "" ]
+  in
+  Lwt_io.write oc req >>= fun () ->
+  let rec try_read () =
+    Lwt_io.read ic ~count:1024 >>= fun msg ->
+    if msg = "" then try_read () else Lwt.return msg
+  in
+  try_read () >>= fun msg ->
+  assert (string_prefix ~prefix:"HTTP/1.1 200 " msg);
+
+  (* We are now connected to mirage.io:443 through the proxy *)
+  let client = `TLS_tunnel (`Hostname hostname, ic, oc) in
+  Conduit_lwt_unix.connect ~ctx client >>= fun (_flow, ic, oc) ->
+  let req =
+    String.concat "\r\n" [ "GET / HTTP/1.1"; "Host: " ^ hostname; ""; "" ]
+  in
+  Lwt_io.write oc req >>= fun () ->
+  Lwt_io.read ic ~count:4096 >>= fun msg ->
+  Lwt_io.print msg >>= fun () ->
+  Lwt_io.read ic ~count:4096 >>= fun msg ->
+  Lwt_io.print msg >>= fun () -> Lwt_io.print "\n"
+
+let () = Lwt_main.run (main ())