(Relay) Handle unexpected replies and disconnections adequately

[mgsmtp.git] / Relay.pas

diff --git a/Relay.pas b/Relay.pas
index cea792d52c5237a026db4f17fb390c413e16fd1f..713db8d8641af8593d6703d4a9999bd6c548efd1 100644 (file)
--- a/Relay.pas
+++ b/Relay.pas
@@ -1,6 +1,6 @@
 {
    MegaBrutal's SMTP Server (MgSMTP)
-   Copyright (C) 2010 MegaBrutal
+   Copyright (C) 2010-2015 MegaBrutal
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
@@ -88,6 +88,7 @@ type
    protected
       FEnvelope: TEnvelope;
       FEMailProperties: TEMailProperties;
+      FTransactionComplete: boolean;
       FRoutingTarget: TRoutingTarget;
       RoutingTable: TRoutingTable;
       TCP: TTCPRFCConnection;
@@ -99,6 +100,7 @@ type
    public
       property Envelope: TEnvelope read FEnvelope;
       property EMailProperties: TEMailProperties read FEMailProperties;
+      property IsTransactionComplete: boolean read FTransactionComplete;
       property RelayServerName: string read GetRelayServerName;
       property RelayServerPort: integer read GetRelayServerPort;
       function OpenConnection: boolean;
@@ -171,6 +173,7 @@ begin
    Self.RoutingTable:= RoutingTable;
    FEnvelope:= Envelope;
    FEMailProperties:= EMailProperties;
+   FTransactionComplete:= false;
    FRoutingTarget:= RoutingTable.GetRouteInfo(Envelope.RelayHost);
    Response:= TRFCReply.Create;
    FillChar(SMTPExtensions, SizeOf(TSMTPExtensions), #0);
@@ -302,10 +305,8 @@ end;
 
 
 procedure TRelayer.AdministerMassFailure(var Result: boolean);
-var i: integer;
 begin
-   for i:= 0 to Envelope.GetNumberOfRecipients - 1 do
-      Envelope.SetRecipientData(i, Response.GetNumericCode, Response.ReplyText.Text);
+   Envelope.SetAllRecipientData(Response.GetNumericCode, Response.ReplyText.Text);
    Result:= false;
 end;
 
@@ -341,12 +342,13 @@ begin
    end
    else Result:= false;
    MXList.Free;
+   FTransactionComplete:= false;
 end;
 
 function TRelayer.Greet: boolean;
 { This function reads and checks the relay server's greeting.
+  Then identifies this server with an EHLO.
   Then, if necessary, authenticates at the connected relay server.
-  Then identifies this server with a HELO.
   The function returns true, if the authentication and the EHLO command were
   successful. }
 var
@@ -360,7 +362,9 @@ begin
    Response.Clear;
    AdministerMassFailure(Result);
    TCP.ReadResponse(Response);
-   if Response.GetNumericCode = SMTP_R_READY then begin
+
+   { Expect 2xx reply. }
+   if (Response.GetNumericCode div 100) = 2 then begin
 
       TCP.SendCommand(SMTP_C_EHLO, MainServerConfig.Name);
       TCP.ReadResponse(Response);
@@ -426,20 +430,32 @@ function TRelayer.SendEnvelope: boolean;
 { Sends the envelope (that is the return-path and the recipient addresses).
   The function returns true, if the MAIL command were successful, and the
   relay server has accepted at least one of the recipient addresses.
+  This function returns false if a null reply is read, which is considered
+  as protocol violation.
   This function is aware of the SMTP extension, named PIPELINING. If it's
   supported by the server, we send RCPT commands stuffed, without waiting
   for a response. After all RCPTs are sent, we check all responses. }
 var
-   i, c: integer; Prms: string;
+   i, c: integer; UltimateFail: boolean; Prms: string;
 
    procedure ProcessRCPTResponse;
    begin
       TCP.ReadResponse(Response);
-      if Response.GetNumericCode = SMTP_R_OK then Inc(c);
+      { If we get an "OK" reply code, we increase the count of sucessful
+        recipients. }
+      if Response.GetNumericCode = SMTP_R_OK then Inc(c)
+      { Response code 0 is non-existent in the SMTP protocol.
+        If we receive something we _perceive_ as 0, then it is likely
+        that something seriously went wrong. MgSMTP shouldn't treat
+        this condition as permanent. }
+      else if Response.GetNumericCode = 0 then UltimateFail:= true;
       Envelope.SetRecipientData(i, Response.GetNumericCode, Response.ReplyText.Text);
    end;
 
 begin
+   { The MAIL command is considered the beginning of the transaction. }
+   FTransactionComplete:= false;
+   UltimateFail:= false;
    Response.Clear;
    Prms:= 'FROM:<' + Envelope.ReturnPath + '>';
 
@@ -463,8 +479,16 @@ begin
          for i:= 0 to Envelope.GetNumberOfRecipients - 1 do
             ProcessRCPTResponse;
 
-      Result:= c <> 0;
+      Result:= (c <> 0) and (not UltimateFail);
+
+      { If there are no accepted recipients, and no protocol failure is
+        discovered, we can't send the DATA command, and practically we
+        can do nothing more for this transaction. Therefore it is
+        considered complete by protocol. }
+      FTransactionComplete:= (c = 0) and (not UltimateFail);
+
       if not Result then begin
+         { Either way, try to reset SMTP state in case of failure. }
          TCP.SendCommand(SMTP_C_RSET);
          TCP.ReadResponse(Response);
       end;
@@ -499,7 +523,12 @@ var i: integer;
 begin
    TCP.WriteLn('.');
    TCP.ReadResponse(Response);
+
+   { Mark the transaction complete, if we have a valid response. }
+   FTransactionComplete:= Response.GetNumericCode <> 0;
+
    for i:= 0 to Envelope.GetNumberOfRecipients - 1 do begin
+      { Set status code for recipients those were accepted in the envelope stage: }
       if Envelope.GetRecipient(i).Data = SMTP_R_OK then
          Envelope.SetRecipientData(i, Response.GetNumericCode, Response.ReplyText.Text);
    end;