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ISAPI Filter? HOW?

Posted on 2001-06-16
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Last Modified: 2011-05-11
Hello,

I am looking for a way to write a ISAPI filter in Delphi. Can anyone point me into a direction where to find examples and/or documentation on this matter.

Thanx.
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Question by:mtieland
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5 Comments
 
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inthe earned 100 total points
ID: 6198058
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Expert Comment

by:inthe
ID: 6198063
a funny example from a teamb member (nick h)
it sends all incoming requests from an MSIE client
to a virtual directory called /NoIE/

library browser;

uses
  Windows,
  SysUtils,
  ISAPI2;

const
  FilterDescription = 'An ISAPI filter that will not let Internet
Explorer into the site.';

function GetFilterVersion(var pVer : THTTP_FILTER_VERSION) : BOOL;
export; stdcall;
begin
  Result := True;
  try
    pVer.dwFlags :=        (SF_NOTIFY_SECURE_PORT
                         or SF_NOTIFY_NONSECURE_PORT
                         or SF_NOTIFY_PREPROC_HEADERS //This is what
we are interested in
                         or SF_NOTIFY_ORDER_LOW
                         );
    pVer.dwFilterVersion := HTTP_FILTER_REVISION;
    StrPCopy(pVer.lpszFilterDesc, FilterDescription);
  except
    Result := False;
  end;
end;

function HttpFilterProc( var pfc: THTTP_FILTER_CONTEXT;
                                  NotificationType : DWORD;
                                  pvNotification   : Pointer): DWORD;
export; stdcall;
var
  PreprocHeaders : THTTP_FILTER_PREPROC_HEADERS;
  Buffer: array[0..1024] of Char;
  BufferSize: DWORD;
  AgentStr, URL: string;
  aPos: Integer;
const
  sUserAgent = 'USER-AGENT:';
  sURL       = 'url';
  NewURL = '/NoIE/';  //Note -- the URL _must_ have a '/' on the end
by the end of this function

function NoIE: DWORD;
begin
  PreprocHeaders := THTTP_FILTER_PREPROC_HEADERS(pvNotification^);
//cast to proper record type
  BufferSize := SizeOf(Buffer);
  PreprocHeaders.GetHeader(pfc, sUserAgent, Buffer, BufferSize);
//Grab the URL.  It will be everything after the domain
  SetString(AgentStr, Buffer, BufferSize);
  if Pos('MSIE', AgentStr) > 0 then //if we are dealing with MSIE
  begin
    BufferSize := SizeOf(Buffer); //Reset Buffer for new use
    PreprocHeaders.GetHeader(pfc, sURL, Buffer, BufferSize);
    SetString(URL, Buffer, BufferSize);
    //Replace whatever the URL is with the /NoIE/ URL
    aPos := Pos('/', URL);
    Delete(URL, aPos, Length(URL) - aPos + 1);
    URL := Concat(URL, NewURL);
    //This sends out the new header and sents the request on its way
    PreprocHeaders.SetHeader(pfc, sURL, PChar(URL));
  end;
  Result := SF_STATUS_REQ_NEXT_NOTIFICATION;  //Means all done and
ready to go on
end;

begin
   case NotificationType of
       SF_NOTIFY_PREPROC_HEADERS : Result := NoIE;
     else
       Result := SF_STATUS_REQ_NEXT_NOTIFICATION;
     end;
end;

exports
  HttpFilterProc,
  GetFilterVersion;


end.
 
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LVL 17

Expert Comment

by:inthe
ID: 6198078
he has a article here but im having diffuculty getting the page to load so dont kow if its still there or not:
www.xapxone.com/html/dl304.htm
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Author Comment

by:mtieland
ID: 6198646
Exactly what I was looking for,

And a funny way of writing too...

Thanx a lot.

(Sorry for the others I can give points only once so the
first good answer gets the points)
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Author Comment

by:mtieland
ID: 6201308
Something I found out about redirecting on the URL_MAP event:

res := 'Location: ' + 'http://www.mylink.com' + #13+#10+#13+#10;
TServerSupportFunc (pfc.ServerSupportFunc) (pfc, SF_REQ_SEND_RESPONSE_HEADER,pChar('302 Redirect'), Cardinal(PChar(res)) , 0);

The second line shows the way you should do the actual redirect!

Martijn
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