HTTP MIME Type Handler Detection
draft-ietf-trade-mime-detector-03

INTERNET-DRAFT                                    MIME Handler Detection
                                                                May 2000
                                                   Expires November 2000

                    HTTP MIME Type Handler Detection
                    ---- ---- ---- ------- ---------
                <draft-ietf-trade-mime-detector-03.txt>

                         Donald E. Eastlake 3rd
                             Chris J. Smith
                            David M. Soroka

                        Status of This Document

   This draft is intended to become an Informational RFC.  Distribution
   of this document is unlimited. Comments should be sent to the TRADE
   WG mailing list <ietf-trade@lists.eListX.com> or to the authors.

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet- Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   Entities composing web pages to provide services over HTTP frequently
   have the problem of not knowing what MIME types have handlers
   installed at a user's browser.  For example, whether an IOTP or VRML
   or SET or some streaming media handler is available.  In some cases
   they would want to display different web pages or content depending
   on a MIME handler's availability.  This document summarizes
   reasonable techniques to solve this problem for most of the browsers
   actually deployed on the Internet as of early 2000.  It is intended
   to be of practical use to implementors during the period before the
   wide deployment of superior standards based techniques which may be
   developed.

D. Eastlake, C. Smith, D. Soroka                                [Page 1]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

Acknowledegements

   Helpful comments by Tony Lewis of Visa have been incorported.

Table of Contents

      Status of This Document....................................1
      Abstract...................................................1

      Acknowledegements..........................................2
      Table of Contents..........................................2

      1. Introduction............................................3
      2. The HTTP 'Accept' Header................................3
      3. JavaScript..............................................3
      4. ActiveX and the Windows Registry........................4
      5. ECML, The Electronic Commerce Modeling Language.........5
      6. Putting It All Together.................................5
      7. Future Development......................................6
      8. Security Considerations.................................6
      9. IANA Considerations.....................................7

      References.................................................8

      Appendix A: Browser Version Sniffer Code...................9

      Authors Addresses.........................................13
      Expiration and File Name..................................13

D. Eastlake, C. Smith, D. Soroka                                [Page 2]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

1. Introduction

   Entities composing web pages to provide services over [HTTP]
   frequently have the problem of not knowing what [MIME] types have
   handlers installed at a user's browser.  For example, whether an
   [IOTP] or VRML or [SET] or some streaming media handler is available.
   In many cases they would want to display different web pages or
   content depending on a MIME handler's availability.  Sending a
   response with a MIME type that is not supported frequently results in
   interrupting the flow of the user experience, browser queries as to
   what to do with the data being provided, and, of course, failure to
   provide the behavior that would have occurred had the correct MIME
   type handler been installed.

   This document describes reasonable techniques to solve this problem
   for most of the browsers actually deployed on the Internet as of
   early 2000.  It is intended to be of practical use to implementors
   during the period before the wide deployment of superior standards
   based techniques which may be developed. It is written in terms of
   determining whether a handler for application/iotp or application/x-
   iotp exists but is equally applicable to other MIME types.

2. The HTTP 'Accept' Header

   The problem should be solved by the Hyper Text Transport Protocol
   [HTTP] request "Accept" header which lists accepted [MIME] types.
   This header is present in both Version 1.0 and 1.1 of HTTP and its
   content is supposed to be a list of MIME types and subtypes that are
   accepted.  The only problem is that many browsers just send "*/*" or
   the like.

   If the particular MIME type you are looking for is specifically
   present in the Accept header, it is generally safe to assume that a
   handler for it is actually installed or part of the browser.

   NOTE: Although not part of the main topic of this document, if you
   are designing MIME type handler software and have access to a browser
   interface that allows you to request the insertion of the MIME type
   or types your software handles into the Accept header, you generally
   should do so.  It will make it easier for servers sensitive to that
   MIME type to respond correctly.

3. JavaScript

   Most recent browsers support one or more scripting languages of which
   the most widely deployed is "JavaScript".  These scripting languages

D. Eastlake, C. Smith, D. Soroka                                [Page 3]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

   appear in web pages and permit the interpretive execution of
   programing language constructs that can probe the browser
   environment, conditionally cause different page contents to be
   displayed, etc.  For example, Appendix A shows JavaScript available
   from the Netscape web site for determining what operating system,
   browser, and version on which a web page is appearing.

   NOTE: JavaScript is a trademark of SUN Microsystems, Inc.  It was
   originally called LiveScript.  It has nothing to do with the Java
   language.

   The syntax for script use appears to be a Hyper Text Markup Language
   (HTML) comment so that bowsers that do not support scripting will
   ignore such items.  That is, script use is preceeded by "<!--" and
   terminated by "-->".  The following is a simple example of
   conditional execution of parts of a web page based on JavaScript MIME
   type handler detection.

   <SCRIPT LANGUAGE=JAVASCRIPT>
   <!-- hide it
   if (navigator.mimeTypes && navigator.mimeTypes.length > 0) {
     if ( navigator.mimeTypes["application/iotp"] ||
          navigator.mimeTypes["application/x-iotp"]) {
       // here if IOTP handler exists
       }
     else {
       // here if IOTP handler does not exist
       }
     }
   // end and hide -->
   </SCRIPT>

4. ActiveX and the Windows Registry

   If running on Microsoft Windows Internet Explorer version 3 or 4, it
   is necessary to query the Windows Registry to determine local MIME
   type support.  Although these broswers support JavaScript, in v3 the
   mimeTypes array is not present and in v4 the mimeTypes array is
   present but always empty.  For example, executing the following code
   will test for support of the IOTP types:

D. Eastlake, C. Smith, D. Soroka                                [Page 4]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

   CString iotpString, xiotpString;
   char* Key, Keyx;

      int rc, rcx;
      iotpString =
   "SOFTWARE\Classes\MIME\Database\Content Type\application/iotp";
      xiotpString =
   "SOFTWARE\Classes\MIME\Database\Content Type\application/x-iotp";
      Key = iotpString.GetBuffer(1);
      Keyx = xiotpString.GetBuffer(1);
      rc = RegOpenKeyEx(HKEY_LOCAL_MACHINE, Key, 0, KEY_READ, hDefKey);
      rcx = RegOpenKeyEx(HKEY_LOCAL_MACHINE, Key, 0, KEY_READ, hDefKey);
   if ( ( rc  == ERROR_SUCCESS ) || ( rcx == ERROR_SUCCESS ) )
    {
    // IOTP Handler exists
    }
   else
    {
    // No IOTP Handler
    }

   NOTE: ActiveX is a trademark of Microsoft and was originally called
   Sweeper.

5. ECML, The Electronic Commerce Modeling Language

   A industry group has recently proposed a standard for fields used in
   electronic commerce.  This fields allow "wallet" software acting for
   the consumer to convey standardized information to a merchant,
   including information as to what payment related protocols are
   supported at the customer site.  See [ECML].

6. Putting It All Together

   The following diagram indicates how these techniques can be put
   together.

D. Eastlake, C. Smith, D. Soroka                                [Page 5]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

   start>-----+
              |
      +------------------+
      | Was desired type |     NO      +-------------------------+
      |found in Accept?  |------------>| Is JavaScript available |
      +------------------+             |and does it show type?   |
            |                          +-------------------------+
       YES  |                            |         |           |
            |<---------------------------+         |        NO |
            |        YES                           |           |
            |                      +---<explorer<--+           |
            |                      |                           |
            |          +----------------------+                |
            |          | Is ActiveX available |                |
            |          |and does it show type?|                |
            |          +----------------------+                |
            |  YES       |        |         |             NO   |
            |<-----------+        |         +----------------->|
            |                     V                            |
   remember |               Indeterminate.            remember |
     that   |.              Take default             that type |
   type IS  |               action.                     is NOT |
   supported|                                        supported |
            X done                                             X

7. Future Development

   Active work is proceeding in the IETF, World Wide Web Consortium
   [W3C], and other standards and industry groups concerning content and
   capabilities negotiation.  This work is likely to lead to superior
   methods to implement the functionality described herein.  However,
   near universal deployment of such new standards/features will take
   some time.  Thus you should expect the methods given herein to be
   obsoleted, but perhaps not for some time.

8. Security Considerations

   It should be noted that the variety of ActiveX control suggested
   above is reading the user's registry, that is, examining their
   computer and reporting back some information it has discovered.  This
   may be a concern among some users.

   In general, the use of JavaScript and, even more so, ActiveX is
   dangerous because they are so powerful.  JavaScript or ActiveX from a
   web page could be invisibly damaging to the client.

D. Eastlake, C. Smith, D. Soroka                                [Page 6]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

   Security of web interactions is normally provided by adopting channel
   encryption on the browser to server connections, such as [TLS].  In
   the absence of some such additional security outside of HTTP,
   requests and/or responses may be forged or tampered with.

9. IANA Considerations

   None specific to the techniques described herein.  For MIME types and
   type registration procedures, see [MIME: RFCs 2046, 2048].

D. Eastlake, C. Smith, D. Soroka                                [Page 7]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

References

   [ECML] <http://www.ecml.org>
          RFC 2706 - "ECML v1: Field Names for E-Commerce", D. Eastlake,
   T. Goldstein, October 1999

   [HTTP] RFC 1945 - "Hypertext Transfer Protocol -- HTTP/1.0", T.
   Berners-Lee, R.  Fielding & H. Frystyk. May 1996.
          RFC 2616 - "Hypertext Transfer Protocol -- HTTP/1.1", R.
   Fielding, J.  Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T.
   Berners-Lee. June 1999.

   [IOTP] RFC 2801 - "Internet Open Trading Protocol - IOTP Version
   1.0", D. Burett. April 2000.

   [MIME] RFC 2045 - "Multipurpose Internet Mail Extensions (MIME) Part
   One: Format of Internet Message Bodies", N. Freed & N. Borenstein.
   November 1996.
          RFC 2046 - "Multipurpose Internet Mail Extensions (MIME) Part
   Two: Media Types", N. Freed & N. Borenstein. November 1996.
          RFC 2047 - "MIME (Multipurpose Internet Mail Extensions) Part
   Three: Message Header Extensions for Non-ASCII Text", K. Moore.
   November 1996.
          RFC 2048 - "Multipurpose Internet Mail Extensions (MIME) Part
   Four: Registration Procedures", N. Freed, J. Klensin & J. Postel.
   November 1996.

   [SET] - "Secure Electronic Transaction (SET) Specification, Version
   1.0", May 31, 1997, available from <http://www.setco.org>.
          Book 1: Business Description
          Book 2: Programmer's Guide
          Book 3: Formal Protocol Definition

   [TLS] RFC 2246 - "The TLS Protocol Version 1.0", T. Dierks, C. Allen.

   [W3C] World Wide Web Consortium, <www.w3.org>

D. Eastlake, C. Smith, D. Soroka                                [Page 8]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

Appendix A: Browser Version Sniffer Code

   <SCRIPT LANGUAGE="JavaScript">
   <!-- hide JavaScript from non-JavaScript browsers
   // Ultimate client-side JavaScript client sniff.
   // (C) Netscape Communications 1999.
   //     Permission granted to reuse and distribute.
   // Revised 17 May 99 to add is_nav5up and is_ie5up (see below).

   // Everything you always wanted to know about your JavaScript client
   // but were afraid to ask. Creates "is_" variables indicating:
   // (1) browser vendor:
   //     is_nav, is_ie, is_opera
   // (2) browser version number:
   //     is_major (integer indicating major version number: 2, 3, 4 ...)
   //     is_minor (float   indicating full  version number:
   //                                               2.02, 3.01, 4.04 ...)
   // (3) browser vendor AND major version number
   //     is_nav2, is_nav3, is_nav4, is_nav4up, is_nav5, is_nav5up,
   //     is_ie3, is_ie4, is_ie4up
   // (4) JavaScript version number:
   //     is_js (float indicating full JavaScript version number:
   //                                                    1, 1.1, 1.2 ...)
   // (5) OS platform and version:
   //     is_win, is_win16, is_win32, is_win31,
   //     is_win95, is_winnt, is_win98
   //     is_os2
   //     is_mac, is_mac68k, is_macppc
   //     is_unix
   //        is_sun, is_sun4, is_sun5, is_suni86
   //        is_irix, is_irix5, is_irix6
   //        is_hpux, is_hpux9, is_hpux10
   //        is_aix, is_aix1, is_aix2, is_aix3, is_aix4
   //        is_linux, is_sco, is_unixware, is_mpras, is_reliant
   //        is_dec, is_sinix, is_freebsd, is_bsd
   //     is_vms
   //
   // See http://www.it97.de/JavaScript/JS_tutorial/bstat/navobj.html and
   // http://www.it97.de/JavaScript/JS_tutorial/bstat/Browseraol.html
   // for detailed lists of userAgent strings.
   //
   // Note: you don't want your Nav4 or IE4 code to "turn off" or
   // stop working when Nav5 and IE5 (or later) are released, so
   // in conditional code forks, use is_nav4up ("Nav4 or greater")
   // and is_ie4up ("IE4 or greater") instead of is_nav4 or is_ie4
   // to check version in code which you want to work on future
   // versions.

   // convert all characters to lowercase to simplify testing
   var agt=navigator.userAgent.toLowerCase();

D. Eastlake, C. Smith, D. Soroka                                [Page 9]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

   // *** BROWSER VERSION ***
   // Note: On IE5, these return 4, so use is_ie5up to detect IE5.
   var is_major = parseInt(navigator.appVersion);
   var is_minor = parseFloat(navigator.appVersion);

   // Note: Opera and WebTV spoof Navigator.  We do strict client
   //  detection.  If you want to allow spoofing, take out the tests
   //  for opera and webtv.
   var is_nav  = ((agt.indexOf('mozilla')!=-1)
               && (agt.indexOf('spoofer')==-1)
               && (agt.indexOf('compatible') == -1)
               && (agt.indexOf('opera')==-1)
               && (agt.indexOf('webtv')==-1));
   var is_nav2 = (is_nav && (is_major == 2));
   var is_nav3 = (is_nav && (is_major == 3));
   var is_nav4 = (is_nav && (is_major == 4));
   var is_nav4up = (is_nav && (is_major >= 4));
   var is_navonly      = (is_nav && ((agt.indexOf(";nav") != -1) ||
                         (agt.indexOf("; nav") != -1)) );
   var is_nav5 = (is_nav && (is_major == 5));
   var is_nav5up = (is_nav && (is_major >= 5));

   var is_ie   = (agt.indexOf("msie") != -1);
   var is_ie3  = (is_ie && (is_major < 4));
   var is_ie4  = (is_ie && (is_major == 4)
                        && (agt.indexOf("msie 5.0")==-1) );
   var is_ie4up  = (is_ie  && (is_major >= 4));
   var is_ie5  = (is_ie && (is_major == 4)
                        && (agt.indexOf("msie 5.0")!=-1) );
   var is_ie5up  = (is_ie  && !is_ie3 && !is_ie4);

   // KNOWN BUG: On AOL4, returns false if IE3 is embedded browser
   // or if this is the first browser window opened.  Thus the
   // variables is_aol, is_aol3, and is_aol4 aren't 100% reliable.
   var is_aol   = (agt.indexOf("aol") != -1);
   var is_aol3  = (is_aol && is_ie3);
   var is_aol4  = (is_aol && is_ie4);

   var is_opera = (agt.indexOf("opera") != -1);
   var is_webtv = (agt.indexOf("webtv") != -1);

   // *** JAVASCRIPT VERSION CHECK ***
   var is_js;
   if (is_nav2 || is_ie3) is_js = 1.0
   else if (is_nav3 || is_opera) is_js = 1.1
   else if ((is_nav4 && (is_minor <= 4.05)) || is_ie4) is_js = 1.2
   else if ((is_nav4 && (is_minor > 4.05)) || is_ie5) is_js = 1.3
   else if (is_nav5) is_js = 1.4
   // NOTE: In the future, update this code when newer versions of JS
   // are released. For now, we try to provide some upward compatibility

D. Eastlake, C. Smith, D. Soroka                               [Page 10]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

   // so that future versions of Nav and IE will show they are at
   // *least* JS 1.x capable. Always check for JS version compatibility
   // with > or >=.
   else if (is_nav && (is_major > 5)) is_js = 1.4
   else if (is_ie && (is_major > 5)) is_js = 1.3
   // HACK: no idea for other browsers;
   //       always check for JS version with > or >=
   else is_js = 0.0;

   // *** PLATFORM ***
   var is_win   = ( (agt.indexOf("win")!=-1) ||
                    (agt.indexOf("16bit")!=-1) );
   // NOTE: On Opera 3.0, the userAgent string includes "Windows 95/NT4"
   // on all Win32, so you can't distinguish between Win95 and WinNT.
   var is_win95 = ((agt.indexOf("win95")!=-1) ||
                   (agt.indexOf("windows 95")!=-1));

   // is this a 16 bit compiled version?
   var is_win16 = ((agt.indexOf("win16")!=-1) ||
              (agt.indexOf("16bit")!=-1) ||
              (agt.indexOf("windows 3.1")!=-1) ||
              (agt.indexOf("windows 16-bit")!=-1) );

   var is_win31 = ((agt.indexOf("windows 3.1")!=-1) ||
                   (agt.indexOf("win16")!=-1) ||
                   (agt.indexOf("windows 16-bit")!=-1));

   // NOTE: Reliable detection of Win98 may not be possible.
   // It appears that:
   //  - On Nav 4.x and before you'll get plain "Windows" in userAgent.
   //  - On Mercury client, the 32-bit version will return "Win98", but
   //    the 16-bit version running on Win98 will still return "Win95".
   var is_win98 = ((agt.indexOf("win98")!=-1) ||
                   (agt.indexOf("windows 98")!=-1));
   var is_winnt = ((agt.indexOf("winnt")!=-1) ||
                   (agt.indexOf("windows nt")!=-1));
   var is_win32 = (is_win95 || is_winnt || is_win98 ||
                   ((is_major >= 4) &&
                    (navigator.platform == "Win32")) ||
                   (agt.indexOf("win32")!=-1) ||
                   (agt.indexOf("32bit")!=-1));

   var is_os2   = ((agt.indexOf("os/2")!=-1) ||
                   (navigator.appVersion.indexOf("OS/2")!=-1) ||
                   (agt.indexOf("ibm-webexplorer")!=-1));

   var is_mac    = (agt.indexOf("mac")!=-1);
   var is_mac68k = (is_mac && ((agt.indexOf("68k")!=-1) ||
                              (agt.indexOf("68000")!=-1)));
   var is_macppc = (is_mac && ((agt.indexOf("ppc")!=-1) ||

D. Eastlake, C. Smith, D. Soroka                               [Page 11]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

                               (agt.indexOf("powerpc")!=-1)));

   var is_sun   = (agt.indexOf("sunos")!=-1);
   var is_sun4  = (agt.indexOf("sunos 4")!=-1);
   var is_sun5  = (agt.indexOf("sunos 5")!=-1);
   var is_suni86= (is_sun && (agt.indexOf("i86")!=-1));
   var is_irix  = (agt.indexOf("irix") !=-1);    // SGI
   var is_irix5 = (agt.indexOf("irix 5") !=-1);
   var is_irix6 = ((agt.indexOf("irix 6") !=-1) ||
                   (agt.indexOf("irix6") !=-1));
   var is_hpux  = (agt.indexOf("hp-ux")!=-1);
   var is_hpux9 = (is_hpux && (agt.indexOf("09.")!=-1));
   var is_hpux10= (is_hpux && (agt.indexOf("10.")!=-1));
   var is_aix   = (agt.indexOf("aix") !=-1);      // IBM
   var is_aix1  = (agt.indexOf("aix 1") !=-1);
   var is_aix2  = (agt.indexOf("aix 2") !=-1);
   var is_aix3  = (agt.indexOf("aix 3") !=-1);
   var is_aix4  = (agt.indexOf("aix 4") !=-1);
   var is_linux = (agt.indexOf("inux")!=-1);
   var is_sco   = (agt.indexOf("sco")!=-1) ||
                  (agt.indexOf("unix_sv")!=-1);
   var is_unixware = (agt.indexOf("unix_system_v")!=-1);
   var is_mpras    = (agt.indexOf("ncr")!=-1);
   var is_reliant  = (agt.indexOf("reliantunix")!=-1);
   var is_dec   = ((agt.indexOf("dec")!=-1) ||
          (agt.indexOf("osf1")!=-1) ||
          (agt.indexOf("dec_alpha")!=-1) ||
          (agt.indexOf("alphaserver")!=-1) ||
          (agt.indexOf("ultrix")!=-1) ||
          (agt.indexOf("alphastation")!=-1));
   var is_sinix = (agt.indexOf("sinix")!=-1);
   var is_freebsd = (agt.indexOf("freebsd")!=-1);
   var is_bsd = (agt.indexOf("bsd")!=-1);
   var is_unix  = ((agt.indexOf("x11")!=-1) || is_sun ||
                is_irix || is_hpux ||
                is_sco ||is_unixware || is_mpras || is_reliant ||
                is_dec || is_sinix || is_aix || is_linux ||
                is_bsd || is_freebsd);

   var is_vms   = ((agt.indexOf("vax")!=-1) ||
                   (agt.indexOf("openvms")!=-1));
   </SCRIPT>

D. Eastlake, C. Smith, D. Soroka                               [Page 12]



INTERNET-DRAFT           MIME Handler Detection                 May 2000

Authors Addresses

   Donald E. Eastlake 3rd
        Motorola
        65 Shindegan Hill Road
        Carmel, NY 10512 USA

        Telephone:   +1 978-562-2827(h)
                     +1 508-261-5434(w)
        FAX:         +1 508-261-4447(w)
        email:       Donald.Eastlake@motorola.com

   Chris J. Smith
        Royal Bank of Canada
        277 Front Street West
        Toronto, Ontario M5V 3A4 CANADA

        Telephone: +1 416-348-6090
        FAX:       +1 416-348-2210
        email:     chris.smith@royalbank.com

   David M. Soroka
        IBM
        Raleigh, NC

        Telephone: +1 919-486-2684
        Fax:       +1 919-543-4653
        email:     dsoroka@us.ibm.com

Expiration and File Name

   This draft expires November 2000.

   Its file name is draft-ietf-trade-mime-detector-03.txt.

D. Eastlake, C. Smith, D. Soroka                               [Page 13]