HTTP MIME Type Handler Detection
draft-ietf-trade-mime-detector-03
The information below is for an old version of the document that is already published as an RFC.
| Document | Type | RFC Internet-Draft (trade WG) | |
|---|---|---|---|
| Authors | Donald E. Eastlake 3rd , Chris J. Smith , David M. Soroka | ||
| Last updated | 2013-03-02 (Latest revision 2000-05-11) | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | RFC 2936 (Informational) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
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]