SSL tunnel using Synapse?
lazarus / 38-Networking and Web Programming

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BigChimp · 2011-06-10 10:32

Hi,

For my Checkride UltraVNC over SSL reverse connect remote support tool
https://bitbucket.org/reiniero/checkride I'm using the stunnel
executable to listen on a local port for VNC traffic and forward it
through an SSL/TLS tunnel to the viewer on the other end (same setup:
stunnel provides the SSL connection).

This will be my first multithreading/networking project, so I'd like
to find out if I'm thinking in the right direction.

Would it be feasible to replace stunnel with Pascal code using e.g.
synapse? I'd imagine I'd have to create 2 additional threads, one to
listen/send on the local socket, one to set up the SSL connnection and
listen/send on that.
Then I'd have to have some kind of queue and forward the packets in
both threads using something like critical sections.

Any similar code that I could review for inspiration?

Thanks,
BigChimp

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BigChimp · 2013-05-18 08:30

Bump:
Quote from: BigChimp on June 10, 2011, 12:32:37 pmWould it be feasible
to replace stunnel with Pascal code using e.g. synapse?
<snip>
Any similar code that I could review for inspiration?

... perhaps there are some new people with new insights

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snorkel · 2013-06-17 22:07

You can do this with Synapse, there is a port forwarding example
somewhere.
Let me see if I can find the code.

You only need one thread I believe as one socket can read and write,
you just have to use select to monitor the socket for new data and
when new data is available you just write it to the remote host.

I couldn't find the full project but these are the two methods it
used.

Code: [Select]PROCEDURE DoTransfer(FromSocket : TTCPBlockSocket ;
ToSocket :
TTCPBlockSocket );
VAR
Buff : ARRAY[0..cMaxBuffer-1] OF CHAR ;
BuffLen : INTEGER ;
P : Pchar ;
Total : INTEGER ;
Delta : INTEGER ;
Count : INTEGER ;

BEGIN
BuffLen := SIZEOF(Buff);
BuffLen := FromSocket.recvBuffer(@Buff, BuffLen);
IF FromSocket.LastError = 0 THEN BEGIN
Total := 0 ;
Delta := 0 ;
P := Buff ;
Count := BuffLen;
WHILE Total < Count DO BEGIN
TRY
Delta := Count - Total ;
IF Delta > cMaxBuffer THEN
Delta := cMaxBuffer ;
Delta := ToSocket.SendBuffer(P,Delta);
EXCEPT
BREAK ;
END ;
INC(P,Delta);
INC(Total,Delta);
END ;
END ELSE BEGIN
BREAK;
END;
END;

function RelayTCP(const fsock, dsock:
TTCPBlockSocket;timeout:integer):
boolean;
var
FDSet: TFDSet;
FDSetSave: TFDSet;
TimeVal: PTimeVal;
TimeV: TTimeVal;
begin
result := false;
//buffer maybe contains some pre-readed datas...
if fsock.LineBuffer <> '' then
begin
buf := fsock.RecvPacket(timeout);
if fsock.LastError <> 0 then
Exit;
dsock.SendString(buf);
end;
//begin relaying of TCP
try
TimeV.tv_usec := (Timeout mod 1000) * 1000;
TimeV.tv_sec := Timeout div 1000;
TimeVal := @TimeV;
if Timeout = -1 then
TimeVal := nil;
FD_ZERO(FDSetSave);
FD_SET(fsock.Socket, FDSetSave);
FD_SET(dsock.Socket, FDSetSave);
FDSet := FDSetSave;
while synsock.Select(65535, @FDSet, nil, nil, TimeVal) > 0 do
begin
if FD_ISSET(dsock.Socket, FDSet) then
DoTransfer(dsock,fsock);
if FD_ISSET(fsock.Socket, FDSet) then
DoTransfer(fsock,dsock);
FDSet := FDSetSave;
end;
finally
end;
result := true;
end;

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BigChimp · 2013-06-18 05:33

Thanks snorkel - I've got some aborted attempt sitting on my harddrive
- I'll see if it matches your code

PS: Sorry, a bit like looking a gift horse in the mouth but the code
in your post would look much better surrounded by code tags