- From: Eric W. Sink <eric@spyglass.com>
- Date: Thu, 22 Dec 1994 13:54:15 -0600
- To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
I submitted this proposal yesterday to the WG list. I have incorporated a
few revisions, and am submitting it again:
1. Remove tab characters to clean up formatting
2. Clarify intent of <opaque>
3. Clarify intent of <oldNonce>
4. Clarify that the header lines are single-line.
5. Clarify the server's responsibility for comparing the MD5 hash.
Thanks for the comments. I will be gone for a week or so over the Christmas
holiday.
Happy Holidays!
-- cut here --
[PROPOSED] HTTP Working Group Jeffery L. Hostetler
INTERNET-DRAFT Eric W. Sink
<draft-NOT_YET_SUBMITTED-simplemd5-aa-00.txt>
Expires SIX MONTHS FROM---> December 21, 1994
A Proposed Extension to HTTP : SimpleMD5 Access Authentication
Status of this Memo
This document is an Internet-Draft. 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.
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Distribution of this document is unlimited. Please send comments
to the proposed HTTP working group at <http-wg@cuckoo.hpl.hp.com>.
Discussions of the working group are archived at
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about HTTP and the applications which use HTTP should take place
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Abstract
The protocol referred to as "HTTP/1.0" includes specification
for a Basic Access Authentication scheme. This scheme is not
considered to be a secure method of user authentication, as the
user name and password are passed over the network in an
unencrypted form. A specification for a new authentication scheme
is needed for future versions of the HTTP protocol. This document
provides specification for such a scheme, referred to as "SimpleMD5
Access Authentication". The encryption method used is the RSA Data
Security, Inc. MD5 Message-Digest Algorithm.
Table of Contents
1. Introduction
1.1 Purpose
1.2 Overall Operation
2. Basic Access Authentication Scheme
2.1 Specification
2.2 Security protocol negotiation
2.3 Example
3. Acknowledgments
4. References
5. Authors Addresses
1. Introduction
1.1 Purpose
The protocol referred to as "HTTP/1.0" includes specification
for a Basic Access Authentication scheme[1]. This scheme is not
considered to be a secure method of user authentication, as the
user name and password are passed over the network in an
unencrypted form. A specification for a new authentication scheme
is needed for future versions of the HTTP protocol. This document
provides specification for such a scheme, referred to as "SimpleMD5
Access Authentication".
The SimpleMD5 Access Authentication scheme is not intended to be
a complete answer to the need for security in the World Wide Web.
This scheme provides no encryption of object content. The intent
is simply to facilitate secure access authentication.
It is proposed that this access authentication scheme be included
in the the proposed HTTP/1.1 specification.
1.2 Overall Operation
Like Basic Access Authentication, the SimpleMD5 scheme is based on
a simple challenge-response paradigm. The SimpleMD5 scheme challenges
using a nonce value. A valid response contains the MD5 checksum of
the password and the given nonce value. In this way, the password
is never sent in the clear. Just as with the Basic scheme, the
username and password must be prearranged in some fashion.
2. SimpleMD5 Access Authentication Scheme
2.1 Specification
The SimpleMD5 Access Authentication scheme is conceptually similar to
the Basic scheme. The formats of the modified WWW-Authenticate header line
and the Authorization header line are specified below.
Due to formatting constraints, both the WWW-Authenticate and the
Authorization header are depicted on multiple lines. In actual usage,
they are required to be a single line of comma-separated attribute-value
pairs, terminated by <CRLF>. Whitespace between the attribute-value pairs
is allowed.
If a server receives a request for an access-protected object,
and an acceptable Authorizatation header is not sent, the server
responds with:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: SimpleMD5 realm="<realm>",
domain="<domain>",
nonce="<nonce>",
opaque="<opaque>",
oldNonce="<TRUE | FALSE>"
The client is expected to retry the request, passing an Authorization header
line as follows:
Authorization: SimpleMD5 username="<username>",
realm="<realm>",
nonce="<nonce>",
response="<MD5response>",
opaque="<opaque>"
The meanings of the identifers used above are as follows:
<realm>
A name given to users so they know which username and password
to send.
<domain>
A comma separated list of URIs, as specified for HTTP/1.0. The
intent is that the client could use this information to know the
set of URIs for which the same authentication information should be
sent. The URIs in this list may exist on different servers. If
this keyword is omitted or empty, the client should assume that
the domain consists of all URIs on the responding server.
<nonce>
A server-specified integer value which may be uniquely generated
each time
a 401 response is made. Servers may defend themselves against replay
attacks by refusing to reuse nonce values.
<opaque>
A string of data, specified by the server, which should returned by
the client unchanged. It is recommended that this string be
base64 or hexadecimal data. Specifically, since the string is passed
in the header lines as a quoted string, the double-quote character
is not allowed.
<username>
It is assumed that both client and server know of a prearranged
username and password pair. The Authorization header returned
by the client specifies the username. The password is not specified
in the clear.
<response>
The MD5 encoding of "<nonce> <password>". The resulting string
should be a 32 digit hexadecimal string.
<oldNonce>
A flag, indicating that the previous request from the client
was rejected because the nonce value was stale. If oldNonce
is TRUE, the client may wish to simply retry the request with
a new encrypted response, without reprompting the user for a
new username and password.
Upon receiving the Authorization information, the server may check its
validity by looking up its known password which corresponds to the submitted
<username>. Then, the server must perform the same MD5 operation performed
by the client, and compare the result to the given <response>.
When the server is constructing the WWW-Authenticate header, the domain,
opaque, and oldNonce keywords may be omitted.
All keyword-value pairs must be expressed in characters from the
US-ASCII character set, excluding control characters.
A client may remember the username, password and nonce values, so that
future requests within the specified <domain> may include the Authorization
line preemptively. The server may choose to accept the old Authorization
information, even though the nonce value included might not be fresh.
Alternatively, the server could return a 401 response with a new nonce
value, causing the client to retry the request. By specifying oldNonce=TRUE
with this response, the server hints to the client that the request should
be retried with the new nonce, without reprompting the user for a new
username and password.
The <opaque> data is useful for transporting state information around.
For example, a server could be responsible for authenticating content
which actual sits on another server. The first 401 response would include
a <domain> which includes the URI on the second server, and the <opaque>
for specifying state information. The client will retry the request, at
which time the server may respond with a 301/302 redirection, pointing
to the URI on the second server. The client will follow the redirection,
and pass the same Authorization line, including the <opaque> data which
the second server may require.
As with the basic scheme, proxies must be completely transparent in
the SimpleMD5 access authentication scheme. That is, they must forward the
WWW-Authenticate and Authorization headers untouched. If a proxy
wants to authenticate a client before a request is forwarded to
the server, it can be done using the Proxy-Authenticate and
Proxy-Authorization headers.
2.2 Security Protocol Negotiation
It is useful for a server to be able to know which security schemes
a client is capable of handling. It is recommended that the HTTP extension
mechanism proposed by Dave Kristol [2] be used. If the client includes
the following header line with the request, then a server can safely assume
that the client can handle SimpleMD5 authentication.
Extension: Security SimpleMD5
If this proposal is accepted as a required part of the HTTP/1.1
specification, then a server may assume SimpleMD5 support when a client
identifies itself as HTTP/1.1 compliant, by sending:
HTTP-Version: HTTP/1.1
It is possible that a server may want to require SimpleMD5 as its
authentication method, even if the server does not know that the client
supports it. A client is encouraged to fail gracefully if the server
specifies any authorization scheme it cannot handle.
2.3 Example
The following example assumes that an access-protected document is being
requested from the server. Both client and server know that the username
for this document is "Mufasa", and the password is "CircleOfLife".
The first time the client requests the document, no Authorization header
is sent, so the server responds with:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: SimpleMD5 realm="PrideRock",
domain="",
nonce="67654464",
opaque="76da3afcb7c9a0",
oldNonce="FALSE"
The client may prompt the user for the username and password, after which it
will respond with a new request, including the following Authorization
header:
Authorization: SimpleMD5 username="Mufasa",
realm="PrideRock",
nonce="67654464",
response="9524c2516e37df5c6a3c7ef5e334a31b",
opaque="76da3afcb7c9a0"
Note that the hexadecimal string for the response is the MD5 encoding of
"67654464 CircleOfLife". The space character between the nonce value and the
password is required, and part of the encrypted result.
3. Acknowledgments
Larry Stewart, at OpenMarket, Inc., contributed to the development and
implementation of this authorization scheme.
Source code in C for the RSA Data Security, Inc. MD5 Message-Digest
Algorithm is available free of charge from RSA Data Security, Inc.
4. References
[1] T. Berners-Lee, R. T. Fielding, H. Frystyk Nielsen.
"Hypertext Transfer Protocol -- HTTP/1.0"
Internet-Draft (work in progress), UC Irvine,
<URL:http://ds.internic.net/internet-drafts/
draft-fielding-http-spec-01.txt>, December 1994.
[2] D. Kristol. "A Proposed Extension Mechanism for HTTP"
<URL:http://www.research.att.com/~dmk/extend.txt>,
December 1994.
5. Authors Addresses
Jeffery L. Hostetler
jeff@spyglass.com
Senior Software Engineer
Spyglass, Inc.
1800 Woodfield Drive
Savoy, IL 61874
Eric W. Sink
eric@spyglass.com
Senior Software Engineer
Spyglass, Inc.
1800 Woodfield Drive
Savoy, IL 61874
--
Eric W. Sink, Senior Software Engineer -- eric@spyglass.com
I don't speak for Spyglass.
"Can I get a direct flight back to reality, or do I have to change planes
in Denver?" - The Santa Clause
Received on Thursday, 22 December 1994 10:49:53 UTC