delphi - ssl v3 poodle and move to tls with indy

Question

As you know the new poodle is in town, Witch barks got Twitter, Cloudflare to drop support to SSL3.

The Indy(TidHttp) 10.6.0.0 revives this nice exception:

EidOsslUnerlayingCryptoError message 'Error connecting with SSL. error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure'

My question is what is the definition required to handle TLS?

update: here is a code that throw the exception: full working code.

var
  parameters:TStringList;
  keySecretBase64:string;
  stream:TStringStream;
  IdEncoderMIME1 : TIdEncoderMIME;
  idHttp1 : TIdHTTP;
  IdSSLIOHandlerSocketOpenSSL1:TIdSSLIOHandlerSocketOpenSSL;//assume on Form
begin
  stream:=TStringStream.create;
  parameters:=TStringList.Create;
  IdEncoderMIME1 := TIdEncoderMIME.Create(nil);
  idHttp1 := TIdHTTP.Create(nil);
  IdSSLIOHandlerSocketOpenSSL1:=TIdSSLIOHandlerSocketOpenSSL.Create(nil);
  IdSSLIOHandlerSocketOpenSSL1.SSLOptions.Method := sslvTLSv1_2;
  IdSSLIOHandlerSocketOpenSSL1.SSLOptions.SSLVersions := [sslvTLSv1_2];
    with IdSSLIOHandlerSocketOpenSSL1 do begin
      SSLOptions.Method := sslvSSLv3;
      SSLOptions.Mode :=  sslmUnassigned;
      SSLOptions.VerifyMode := [];
      SSLOptions.VerifyDepth := 2;
    end;
    with idHttp1 do begin
      IOHandler := IdSSLIOHandlerSocketOpenSSL1;
      ReadTimeout := 0;
      AllowCookies := True;
      ProxyParams.BasicAuthentication := False;
      ProxyParams.ProxyPort := 0;
      Request.ContentLength := -1;
      Request.ContentRangeEnd := 0;
      Request.ContentRangeStart := 0;
      Request.ContentType := 'application/x-www-form-urlencoded';
      Request.Accept := 'text/html, */*';

      Request.BasicAuthentication := False;
      Request.UserAgent := 'Mozilla/3.0 (compatible; Indy Library)';
      HTTPOptions := [hoForceEncodeParams];
    end;
    parameters.Clear;
    idHttp1.Request.CustomHeaders.Clear;
    IdEncoderMIME1.FillChar:='=';

  try
    keySecretBase64 := TIdEncoderMIME.EncodeString(key+ ':' + secret, IndyTextEncoding_UTF8);// this is twitter provided key and secret
    parameters.Add('grant_type=client_credentials');
    idHttp1.Request.CustomHeaders.AddValue('Authorization','Basic '+keySecretBase64);
    idHttp1.post(URL,parameters,stream);
  finally
    stream.Free;
    parameters.Free;
    parameters.Free;
    IdSSLIOHandlerSocketOpenSSL1.Free;
  end;
end;

Answer 1

Your code selects TLS 1.2 in the SSLOptions property Method:

IdSSLIOHandlerSocketOpenSSL1.SSLOptions.Method := sslvTLSv1_2;
IdSSLIOHandlerSocketOpenSSL1.SSLOptions.SSLVersions := [sslvTLSv1_2];

However, two lines later this value is overwritten with SSL 3:

with IdSSLIOHandlerSocketOpenSSL1 do begin
  SSLOptions.Method := sslvSSLv3;
  ...
end;

So the client will not connect with the newer TLS 1.2 protocol but with SSL 3, which is no longer supported by the server.

This explains the error message, which says that the SSL 3 handshake (which the client tried) failed:

SSL. error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure'

If you remove the second assignment, the IdHTTP client will use TLS 1.2 for the connect.