package sendmail
Implementation of the sendmail command
Install
Dune Dependency
Authors
Maintainers
Sources
colombe-v0.2.0.tbz
sha256=12c2736f0e1a6e001a47e2b39907bc1f6ddb18718f2c341dcd10b19554706ead
sha512=09e19eff4a016f7735b35f2298f0557be38ee00b24b5bbf102b3c66c3b783ea5190e55ed2da3300fb8c05f445a832f1482fdea84ec35b78b238e771e5e377fd7
doc/src/sendmail.tls/sendmail_with_tls.ml.html
Source file sendmail_with_tls.ml
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open Colombe.Sigs open Colombe.State open Colombe let ( <.> ) f g = fun x -> f (g x) module Context_with_tls = struct type t = { context : Context.t ; mutable tls : Tls.Engine.state option } type encoder = t type decoder = t let pp ppf t = Fmt.pf ppf "{ @[<hov>context= @[<hov>%a@];@ \ tls= #state@] }" Context.pp t.context let encoder x = x let decoder x = x let make () = { context= Context.make () ; tls= None } let tls { tls; _ } = match tls with | Some _ -> true | _ -> false end let src = Logs.Src.create "sendmail-with-tls" ~doc:"logs sendmail's event with TLS" module Log = (val Logs.src_log src : Logs.LOG) module type VALUE = sig type 'x send type 'x recv type error val pp_error : error Fmt.t val encode_without_tls : Encoder.encoder -> 'x send -> 'x -> (unit, [> `Protocol of error ]) t val decode_without_tls : Decoder.decoder -> 'x recv -> ('x, [> `Protocol of error ]) t end module Value = struct type helo = Domain.t type mail_from = Reverse_path.t * (string * string option) list type rcpt_to = Forward_path.t * (string * string option) list type auth = Sendmail.mechanism type pp_220 = string list type pp_221 = string list type pp_250 = string list type tp_354 = string list type code = int * string list type error = [ Request.Encoder.error | Reply.Decoder.error | `Unexpected_response of int * string list ] let pp_error ppf = function | #Request.Encoder.error as err -> Request.Encoder.pp_error ppf err | #Reply.Decoder.error as err -> Reply.Decoder.pp_error ppf err | `Unexpected_response (code, txts) -> Fmt.pf ppf "Unexpected response %3d: %a" code Fmt.(Dump.list string) txts type 'x send = | Helo : helo send | Mail_from : mail_from send | Rcpt_to : rcpt_to send | Data : unit send | Dot : unit send | Quit : unit send | Auth : auth send | Payload : string send | Starttls : unit send type 'x recv = | PP_220 : pp_220 recv | PP_221 : pp_221 recv | PP_250 : pp_250 recv | TP_354 : tp_354 recv | Code : code recv let pp_witness : type a. a recv Fmt.t = fun ppf -> function | PP_220 -> Fmt.pf ppf "PP-220" | PP_221 -> Fmt.pf ppf "PP-221" | PP_250 -> Fmt.pf ppf "PP-250" | TP_354 -> Fmt.pf ppf "TP-354" | Code -> Fmt.pf ppf "<code>" let encode : type a. Encoder.encoder -> a send -> a -> (unit, [> Encoder.error ]) t = fun encoder w v -> let fiber : a send -> [> Encoder.error ] Encoder.state = function | Payload -> let k encoder = Encoder.write v encoder ; Encoder.write "\r\n" encoder ; Encoder.flush (fun _ -> Encoder.Done) encoder in Encoder.safe k encoder | Helo -> Request.Encoder.request (`Hello v) encoder | Mail_from -> Request.Encoder.request (`Mail v) encoder | Rcpt_to -> Request.Encoder.request (`Recipient v) encoder | Data -> Request.Encoder.request `Data encoder | Dot -> Request.Encoder.request `Data_end encoder | Quit -> Request.Encoder.request `Quit encoder | Starttls -> Request.Encoder.request (`Verb ("STARTTLS", [])) encoder | Auth -> match v with | PLAIN -> Request.Encoder.request (`Verb ("AUTH", [ "PLAIN" ])) encoder in let rec go = function | Encoder.Done -> Return () | Encoder.Write { continue; buffer; off; len; } -> Write { k= go <.> continue; buffer; off; len; } | Encoder.Error err -> Error err in (go <.> fiber) w let decode : type a. Decoder.decoder -> a recv -> (a, [> Decoder.error ]) t = fun decoder w -> let k : Reply.t -> (a, [> Decoder.error ]) t = fun v -> match w, v with | PP_220, `PP_220 txts -> Return txts | PP_221, `PP_221 txts -> Return txts | PP_250, `PP_250 txts -> Return txts | TP_354, `TP_354 txts -> Return txts | Code, `Other v -> Return v | Code, `PN_501 txts -> Return (501, txts) | Code, `PN_504 txts -> Return (504, txts) | Code, `PP_250 txts -> Return (250, txts) | _, _ -> Log.err (fun m -> m "Unexpected valid value: witness:%a value:%a" pp_witness w Reply.pp v) ; let code = Reply.code v in let txts = Reply.lines v in Error (`Unexpected_response (code, txts)) in let rec go = function | Decoder.Done v -> k v | Decoder.Read { buffer; off; len; continue; } -> Read { k= go <.> continue; buffer; off; len; } | Decoder.Error { error; _ } -> Error error in go (Reply.Decoder.response decoder) end module Value_without_tls = struct include Value let encode_without_tls ctx w v = let rec go = function | Error err -> Error (`Protocol err) | Read { k; buffer; off; len; } -> Read { k= go <.> k; buffer; off; len; } | Write { k; buffer; off; len; } -> Write { k= go <.> k; buffer; off; len; } | Return v -> Return v in go (encode ctx w v) let decode_without_tls ctx w = let rec go = function | Error err -> Error (`Protocol err) | Read { k; buffer; off; len; } -> Read { k= go <.> k; buffer; off; len; } | Write { k; buffer; off; len; } -> Write { k= go <.> k; buffer; off; len; } | Return v -> Return v in go (decode ctx w) end module type S = sig type 'x send type 'x recv module Value : sig type error end type error = [ `Protocol of Value.error | `Tls_alert of Tls.Packet.alert_type | `Tls_failure of Tls.Engine.failure ] val pp_error : error Fmt.t type encoder type decoder val starttls_as_client : encoder -> Tls.Config.client -> (unit, [> error ]) State.t val starttls_as_server : decoder -> Tls.Config.server -> (unit, [> error ]) State.t val close : encoder -> (unit, [> error ]) State.t val encode : encoder -> 'a send -> 'a -> (unit, [> error ]) State.t val decode : decoder -> 'a recv -> ('a, [> error ]) State.t end module Make_with_tls (Value : VALUE) : S with type 'x send = 'x Value.send and type 'x recv = 'x Value.recv and type encoder = Context_with_tls.encoder and type decoder = Context_with_tls.decoder and type Value.error = Value.error = struct type error = [ `Protocol of Value.error | `Tls_alert of Tls.Packet.alert_type | `Tls_failure of Tls.Engine.failure ] type encoder = Context_with_tls.t type decoder = Context_with_tls.t let pp_error ppf = function | `Protocol v -> Value.pp_error ppf v | `Tls_alert alert -> Fmt.pf ppf "TLS alert: %s" (Tls.Packet.alert_type_to_string alert) | `Tls_failure err -> Fmt.pf ppf "TLS failure: %s" (Tls.Packet.alert_type_to_string (Tls.Engine.alert_of_failure err)) type 'x send = 'x Value.send type 'x recv = 'x Value.recv let only_write_tls = function | `Response (Some raw) -> let rec k raw n = let raw = Cstruct.shift raw n in (* XXX(dinosaure): write until raw is non-empty. *) if Cstruct.len raw = 0 then Return () else Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw; } in Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw; } | `Response None -> Return () let rec go_to_failure failure = function | Read _ | Return _ | Error _ -> Error (`Tls_failure failure) | Write { k; buffer; off; len; } -> Write { k= go_to_failure failure <.> k; buffer; off; len; } let rec go_to_alert alert = function | Return _ | Error _ -> Error (`Tls_alert alert) | Write { k; buffer; off; len; } -> Write { k= go_to_alert alert <.> k; buffer; off; len; } | Read { k; buffer; off; len; } -> Read { k= go_to_alert alert <.> k; buffer; off; len; } let handle_handshake ctx state k_fiber = let buffer_with_tls = Bytes.create 0x1000 in let rec fiber_write state = function | `Response (Some raw) -> let rec k raw n = let raw = Cstruct.shift raw n in (* XXX(dinosaure): write until raw is non-empty. *) if Cstruct.len raw = 0 then ( if Tls.Engine.handshake_in_progress state then Read { k= k_handshake state; buffer= buffer_with_tls; off= 0; len= 0x1000; } else k_fiber state ) else Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw; } in Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw; } | `Response None -> k_fiber state and fiber_read state resp = function | `Data (Some raw) -> Log.debug (fun m -> m "~> %S" (Cstruct.to_string raw)) ; (* XXX(dinosaure): should never occur while handshake! *) let buffer = ctx.Context_with_tls.context.Context.decoder.Decoder.buffer in let max = ctx.Context_with_tls.context.Context.decoder.Decoder.max in let len = min (Bytes.length buffer - max) (Cstruct.len raw) in if len < Cstruct.len raw then Fmt.failwith "Read buffer is full and TLS handshake is not done" ; (* TODO: this case is when, while handshake, we receive much more data that what we can store. We can not consume them because handshake is not done. But to be clear, this case should __never__ appear. *) Cstruct.blit_to_bytes raw 0 buffer max len ; ctx.Context_with_tls.context.Context.decoder.Decoder.max <- max + len ; if Tls.Engine.handshake_in_progress state then Read { k= k_handshake state; buffer= buffer_with_tls; off= 0; len= 0x1000; } else k_fiber state | `Data None -> fiber_write state resp and k_handshake state len = let raw = Cstruct.of_bytes buffer_with_tls ~off:0 ~len in match Tls.Engine.handle_tls state raw with | `Ok (`Ok state, resp, data) -> fiber_read state resp data | `Ok (`Eof, _resp, _data) -> Fmt.failwith "Reach End-of-stream while handshake" | `Fail (failure, `Response resp) -> (go_to_failure failure <.> only_write_tls) (`Response (Some resp)) | `Ok (`Alert alert, resp, _data) -> (go_to_alert alert <.> only_write_tls) resp in Read { k= k_handshake state; buffer= buffer_with_tls; off= 0; len= 0x1000; } let rec go_with_tls ctx fiber delayed_data = match ctx.Context_with_tls.tls, fiber, Cstruct.len delayed_data with | Some state, fiber, _ when not (Tls.Engine.can_handle_appdata state) -> let k state = ctx.tls <- Some state ; go_with_tls ctx fiber delayed_data in handle_handshake ctx state k | Some state, Write { k; buffer; off; len; }, _ -> let raw = Cstruct.of_string ~off ~len buffer in Log.debug (fun m -> m "<= %S" (Cstruct.to_string raw)) ; ( match Tls.Engine.send_application_data state [ raw ] with | Some (state, raw) -> let k n = ctx.tls <- Some state ; go_with_tls ctx (k n) delayed_data in Write { k; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw; } | None -> k len ) | Some state, Read { k= k_without_tls; buffer= buffer_without_tls; off= off_0; len= len_0; }, 0 -> let buffer_with_tls = Bytes.make 0x1000 '\000' in let rec fiber_read = function | Some raw -> let len = min (Cstruct.len raw) len_0 in Log.debug (fun m -> m "=> %S" (Cstruct.to_string raw)) ; Cstruct.blit_to_bytes raw 0 buffer_without_tls off_0 len ; go_with_tls ctx (k_without_tls len) (Cstruct.shift raw len) | None -> (* Even if data is empty, eof was not reached. *) Read { k; buffer= Bytes.make 0x1000 '\000'; off= 0; len= 0x1000; } and fiber_write data = function | Some raw -> let rec k raw n = let raw = Cstruct.shift raw n in (* XXX(dinosaure): write until raw is non-empty. *) if Cstruct.len raw = 0 then fiber_read data else Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw; } in Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw; } | None -> fiber_read data and k n = let raw = Cstruct.of_bytes ~off:0 ~len:n buffer_with_tls in match Tls.Engine.handle_tls state raw with | `Ok (`Ok state, `Response None, `Data data) -> ctx.tls <- Some state ; fiber_read data | `Ok (`Ok state, `Response resp, `Data data) -> ctx.tls <- Some state ; fiber_write data resp | `Ok (`Eof, `Response resp, `Data data) -> ctx.tls <- None ; let rec go_to_eof = function | Read { k; _ } -> k 0 (* emit end-of-stream *) | Write { k; buffer; off; len; } -> Write { k= go_to_eof <.> k; buffer; off; len; } | v -> v in go_to_eof (fiber_write data resp) | `Fail (failure, `Response resp) -> (go_to_failure failure <.> only_write_tls) (`Response (Some resp)) | `Ok (`Alert alert, `Response resp, `Data _) -> (go_to_alert alert <.> only_write_tls) (`Response resp) in Read { k; buffer= buffer_with_tls; off= 0; len= (Bytes.length buffer_with_tls); } | Some _, Read { k; buffer= buffer_without_tls; off= off_0; len= len_0; }, delayed_len -> let len = min delayed_len len_0 in Cstruct.blit_to_bytes delayed_data 0 buffer_without_tls off_0 len ; go_with_tls ctx (k len) (Cstruct.shift delayed_data len) | None, (Read _ as fiber), 0 -> fiber | None, Read { k; buffer; off; len; }, delayed_len -> let len = min delayed_len len in Cstruct.blit_to_bytes delayed_data 0 buffer off len ; go_with_tls ctx (k len) (Cstruct.shift delayed_data len) | None, fiber, _ -> fiber | _, fiber, _ -> fiber let starttls_as_client ctx config = let state, raw = Tls.Engine.client config in let rec k raw len = let raw = Cstruct.shift raw len in if Cstruct.len raw = 0 then handle_handshake ctx state (fun state -> ctx.tls <- Some state ; Return ()) else Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw } in (* XXX(dinosaure): clean decoder. *) Log.debug (fun m -> m "Clean internal buffer to start TLS.") ; let buffer = ctx.Context_with_tls.context.Context.decoder.Decoder.buffer in Bytes.fill buffer 0 (Bytes.length buffer) '\000' ; ctx.Context_with_tls.context.Context.decoder.Decoder.pos <- 0 ; ctx.Context_with_tls.context.Context.decoder.Decoder.max <- 0 ; Log.debug (fun m -> m "Start TLS.") ; Write { k= k raw; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw } let starttls_as_server ctx config = let state = Tls.Engine.server config in (* XXX(dinosaure): clean decoder. *) Log.debug (fun m -> m "Clean internal buffer to start TLS.") ; let buffer = ctx.Context_with_tls.context.Context.decoder.Decoder.buffer in Bytes.fill buffer 0 (Bytes.length buffer) '\000' ; ctx.Context_with_tls.context.Context.decoder.Decoder.pos <- 0 ; ctx.Context_with_tls.context.Context.decoder.Decoder.max <- 0 ; Log.debug (fun m -> m "Start TLS.") ; handle_handshake ctx state (fun state -> ctx.tls <- Some state ; Return ()) let close ctx = match ctx.Context_with_tls.tls with | Some state -> let state, raw = Tls.Engine.send_close_notify state in ctx.tls <- Some state ; let rec loop len = let raw = Cstruct.shift raw len in if Cstruct.len raw = 0 then Return () else Write { k= loop ; buffer= Cstruct.to_string raw ; off= 0 ; len= Cstruct.len raw } in Write { k= loop; buffer= Cstruct.to_string raw; off= 0; len= Cstruct.len raw } | None -> Return () let encode : type a. encoder -> a send -> a -> (unit, [> error ]) t = fun ctx w v -> let fiber = Value.encode_without_tls ctx.Context_with_tls.context.Context.encoder w v in go_with_tls ctx fiber Cstruct.empty let decode : type a. decoder -> a recv -> (a, [> error ]) t = fun ctx w -> let decoder = ctx.Context_with_tls.context.Context.decoder in let fiber = Value.decode_without_tls decoder w in (* XXX(dinosaure): [decoder] can already contains something. TODO(dinosaure): [?relax] as an argument? *) if Decoder.at_least_one_line ~relax:true decoder then fiber else go_with_tls ctx fiber Cstruct.empty module Value = struct type error = Value.error end end module Value_with_tls = Make_with_tls(Value_without_tls) module Monad = State.Scheduler(Context_with_tls)(Value_with_tls) let properly_quit_and_fail ctx err = let open Monad in let* _txts = send ctx Value.Quit () >>= fun () -> recv ctx Value.PP_221 in Error err let auth ctx mechanism info = let open Monad in match info with | None -> return `Anonymous | Some (username, password) -> match mechanism with | Sendmail.PLAIN -> let* code, txts = send ctx Value.Auth mechanism >>= fun () -> recv ctx Value.Code in match code with | 504 -> properly_quit_and_fail ctx `Unsupported_mechanism | 538 -> properly_quit_and_fail ctx `Encryption_required | 534 -> properly_quit_and_fail ctx `Weak_mechanism | 334 -> let* () = match txts with | [] -> let payload = Base64.encode_exn (Fmt.strf "\000%s\000%s" username password) in send ctx Value.Payload payload | x :: _ -> let x = Base64.decode_exn x in let payload = Base64.encode_exn (Fmt.strf "%s\000%s\000%s" x username password) in send ctx Value.Payload payload in ( recv ctx Value.Code >>= function | (235, _txts) -> return `Authenticated | (501, _txts) -> properly_quit_and_fail ctx `Authentication_rejected | (535, _txts) -> properly_quit_and_fail ctx `Authentication_failed | (code, txts) -> Error (`Tls (`Protocol (`Unexpected_response (code, txts)))) ) | code -> Error (`Tls (`Protocol (`Unexpected_response (code, txts)))) type domain = Sendmail.domain type reverse_path = Sendmail.reverse_path type forward_path = Sendmail.forward_path type authentication = Sendmail.authentication type mechanism = Sendmail.mechanism type ('a, 's) stream = unit -> ('a option, 's) io type error = [ `Tls of [ `Protocol of Value.error | `Tls_alert of Tls.Packet.alert_type | `Tls_failure of Tls.Engine.failure ] | `Protocol of [ `Protocol of Value.error | `Tls_alert of Tls.Packet.alert_type | `Tls_failure of Tls.Engine.failure ] | `Unsupported_mechanism | `Encryption_required | `Weak_mechanism | `Authentication_rejected | `Authentication_failed | `Authentication_required | `STARTTLS_unavailable ] let pp_error ppf = function | `Protocol err | `Tls err -> Value_with_tls.pp_error ppf err | `Unsupported_mechanism -> Fmt.pf ppf "Unsupported mechanism" | `Encryption_required -> Fmt.pf ppf "Encryption required" | `Weak_mechanism -> Fmt.pf ppf "Weak mechanism" | `Authentication_rejected -> Fmt.pf ppf "Authentication rejected" | `Authentication_failed -> Fmt.pf ppf "Authentication failed" | `Authentication_required -> Fmt.pf ppf "Authentication required" | `STARTTLS_unavailable -> Fmt.pf ppf "STARTTLS unavailable" let has_8bit_mime_transport_extension = List.exists ((=) "8BITMIME") let has_starttls = List.exists ((=) "STARTTLS") (* XXX(dinosaure): [m0] IS [Sendmail.m0] + [STARTTLS], we should functorize it over a common interface. *) let m0 ctx config ?authentication ~domain sender recipients = let open Monad in recv ctx Value.PP_220 >>= fun _txts -> let* txts = send ctx Value.Helo domain >>= fun () -> recv ctx Value.PP_250 in let has_starttls = has_starttls txts in if not has_starttls then Error `STARTTLS_unavailable else let* _txts = send ctx Value.Starttls () >>= fun () -> recv ctx Value.PP_220 in Value_with_tls.starttls_as_client ctx config |> (reword_error (fun err -> `Tls err)) >>= fun () -> let* txts = send ctx Value.Helo domain >>= fun () -> recv ctx Value.PP_250 in let has_8bit_mime_transport_extension = has_8bit_mime_transport_extension txts in ( match authentication with | Some a -> auth ctx a.Sendmail.mechanism (Some (a.Sendmail.username, a.Sendmail.password)) | None -> return `Anonymous ) >>= fun _status -> let parameters = if has_8bit_mime_transport_extension then [ "BODY", Some "8BITMIME" ] else [] in let* code, txts = send ctx Value.Mail_from (sender, parameters) >>= fun () -> recv ctx Value.Code in let rec go = function | [] -> send ctx Value.Data () >>= fun () -> recv ctx Value.TP_354 >>= fun _txts -> return () | x :: r -> send ctx Value.Rcpt_to (x, []) >>= fun () -> recv ctx Value.PP_250 >>= fun _txts -> go r in match code with | 250 -> go recipients | 530 -> properly_quit_and_fail ctx `Authentication_required | _ -> Error (`Tls (`Protocol (`Unexpected_response (code, txts)))) let m1 ctx = let open Monad in let* _txts = send ctx Value.Dot () >>= fun () -> recv ctx Value.PP_250 in let* _txts = send ctx Value.Quit () >>= fun () -> recv ctx Value.PP_221 in return () let run : type s flow. s impl -> (flow, s) rdwr -> flow -> ('a, 'err) t -> (('a, 'err) result, s) io = fun { bind; return; } rdwr flow m -> let ( >>= ) = bind in let rec go = function | Read { buffer; off; len; k; } -> rdwr.rd flow buffer off len >>= fun len -> go (k len) | Write { buffer; off; len; k; } -> rdwr.wr flow buffer off len >>= fun () -> go (k len) | Return v -> return (Ok v) | Error err -> return (Error err : ('a, 'err) result) in go m let sendmail { bind; return } rdwr flow ctx mail = let ( >>= ) = bind in match ctx.Context_with_tls.tls with | None -> let rec go = function | Some (buf, off, len) -> rdwr.wr flow buf off len >>= mail >>= go | None -> return () in mail () >>= go | Some state -> let rec go state = mail () >>= function | None -> return state | Some (buf, off, len) -> let raw = Cstruct.of_string buf ~off ~len in match Tls.Engine.send_application_data state [ raw ] with | Some (state, raw) -> let buf = Cstruct.to_string raw in rdwr.wr flow buf 0 (Cstruct.len raw) >>= fun () -> go state | None -> go state in go state >>= fun state -> ctx.tls <- Some state ; return () let sendmail ({ bind; return; } as impl) rdwr flow context config ?authentication ~domain sender recipients mail : ((unit, error) result, 's) io = let ( >>- ) = bind in let ( >>= ) x f = x >>- function | Ok v -> f v | Error _ as err -> return err in let m0 = m0 context config ~domain ?authentication sender recipients in run impl rdwr flow m0 >>= fun () -> (* assert that context is empty. *) sendmail impl rdwr flow context mail >>- fun () -> let m1 = m1 context in run impl rdwr flow m1
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