sslsockets, TSSLSocketHandler, TInetSocket - example?
lazarus / 38-Networking and Web Programming

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prof7bit · 2022-11-15 15:23

There is a TInetSocket in ssockets (in fcl-net), It wraps a TCP socket
into a TStream, I am using it to implement a TCP client like so:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i     try   
 FSocket := TInetSocket.Create(Host, Port);     
FSocket.WriteByte(42);      ... 
There is also a unit sslsockets that implements a TSSLSocketHandler
that seems to be meant to be plugged into the TInetSocket constructor
as the 3rd argument, probably to make it SSL capable.

But TSSLSocketHandler is not meant to be used directly because it has
abstract methods. Is there any example of how this code is supposed to
look like, how it is meant to be used? What do I need to implement to
make the above connection with TInetSocket talk to an SSL server?

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Warfley · 2022-11-15 16:20

Use "TSSLSocketHandler.GetDefaultHandler" to create an SSL handler
with the default handler class. To register the default handler class
to be OpenSSL simply import the "opensslsockets" unit in your uses
clause and you should be fine
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses 
ssockets, sslsockets, opensslsockets; ...FSocket :=
TInetSocket.Create(Host, Port, TSSLSocketHandler.GetDefaultHandler);

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prof7bit · 2022-11-16 10:52

Quote from: Warfley on November 15, 2022, 05:20:14 pmUse
"TSSLSocketHandler.GetDefaultHandler" to create an SSL handler with
the default handler class. To register the default handler class to be
OpenSSL simply import the "opensslsockets" unit in your uses clause
and you should be fine
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses 
ssockets, sslsockets, opensslsockets; ...FSocket :=
TInetSocket.Create(Host, Port, TSSLSocketHandler.GetDefaultHandler);
Thank you.

Unfortunatley this does not seem to work. If I run that code (with FPC
latest main) I get this exception:

Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i An
unhandled exception occurred at $00000000004AE9E1:EAccessViolation:
Access violation  $00000000004AE9E1  Write,  line 624 of
openssl/src/fpopenssl.pp  $0000000000460A18  WriteByte,  line 1221 of
../objpas/classes/streams.inc 
If I single step into it I notice that in

opensslsockets.pp, line 304,
in method TOpenSSLSocketHandler.Send
in that line:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    
Result:=FSsl.Write(@Buffer,Count); 
FSsl is nil!

So there seems to be some initialization missing or broken.

I am using Ubuntu 22.04.1 LTS and I have libssl.so.3 (which is why I
need FPC trunk)

Does the following minimal test program run on our system?
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
test1; uses  ssockets, sslsockets, opensslsockets; var  FSocket:
TInetSocket; begin  FSocket := TInetSocket.Create('google.com', 443,
TSSLSocketHandler.GetDefaultHandler);  FSocket.WriteByte(0); 
FSocket.Free;end.

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prof7bit · 2022-11-16 11:18

Found it.

I need to explicitly call Connect after Create. When a sockethandler
is passed then the behavior of the constructor changes, without
passing a handler the connect happens immediately.

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prof7bit · 2022-11-16 13:22

Ok, for the sake of completeness, I think I have figured out how to
use this in a real world application, because there was another minor
inconvenience when trying to shut down and close the socket while a
thread is in a blocking read on that socket.

Also there is another minor inconvenience when using FPC stable or
fixes release: the supported libssl versions are outdated (already
fixed in main), it would not work on current Linux distributions
anymore without patching the versions array.

This minimal demo example is what I came up with:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
test1; uses  cthreads, Classes, sysutils, sockets, ssockets,
sslsockets, opensslsockets, openssl; type   { TReadThread }  
TReadThread = class(TThread)    procedure Execute; override; 
end; const  SSL = True; var  Thread: TReadThread;  Socket:
TInetSocket;  SSLHandler: TOpenSSLSocketHandler; { TReadThread
} procedure TReadThread.Execute;var  B: Byte;begin  writeln('thread:
starting');  try    repeat      B := Socket.ReadByte;     
writeln(B);    until Terminated;   except    on E: EReadError do
begin      WriteLn('thread: read error means socket was shut down'); 
 end;    on E: Exception do begin      writeln('thread: some other
exception');      Writeln(E.ClassName);    end;  end; 
writeln('thread: ending');end; begin   // ############## connect   if
SSL then begin    if not InitSSLInterface then begin      writeln('did
not find libssl version 1, trying version 3');      // this is already
fixed in fpc trunk      openssl.DLLVersions[1] := '.3'; // patch the
versions array    end;    if not InitSSLInterface then begin     
writeln('coul not find any usable ssl support');      halt(1);   
end;    SSLHandler := TOpenSSLSocketHandler.create;    Socket :=
TInetSocket.Create('google.com', 443, SSLHandler);    Socket.Connect; 
end  else begin    Socket := TInetSocket.Create('google.com', 80); 
end;  Thread := TReadThread.Create(False);    // wait some time while
other thread is in blocking read  Sleep(1000);    // ##############
close connection   Thread.Terminate;   writeln('force it to exit
blocking read in a defined manner');  if SSL then begin    // we need
to shutdown the ssl handler, not the socket,    // otherwise the
entire program would crash    SSLHandler.Shutdown(True);  end  else
begin    fpshutdown(Socket.Handle, SHUT_RDWR);  end;   Socket.Free; 
Sleep(1000);  writeln('done');end. 
This should output something like this:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i did not
find libssl version 1, trying version 3thread: startingforce it to
exit blocking read in a defined mannerthread: read error means socket
was shut downthread: endingdone

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r.lukasiak · 2023-09-29 05:55

@prof7bit
great example!
I've applied it to my code and it seems to be working ok but how could
I apply it on the server side? I'm playing with the demos isocksvr.pp
and isockcli.pp