Cookie Prefixes
draft-west-cookie-prefixes-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Author | Mike West | ||
| Last updated | 2015-10-09 | ||
| Replaced by | draft-ietf-httpbis-cookie-prefixes | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-west-cookie-prefixes-02
HTTPbis M. West
Internet-Draft Google, Inc
Updates: 6265 (if approved) October 9, 2015
Intended status: Standards Track
Expires: April 11, 2016
Cookie Prefixes
draft-west-cookie-prefixes-02
Abstract
This document updates RFC6265 by adding a set of restrictions upon
the names which may be used for cookies with specific properties.
These restrictions enable user agents to smuggle cookie state to the
server within the confines of the existing "Cookie" request header
syntax, and limits the ways in which cookies may be abused in a
conforming user agent.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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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."
This Internet-Draft will expire on April 11, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and notation . . . . . . . . . . . . . . . . . . 2
3. Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. The "$Secure-" prefix . . . . . . . . . . . . . . . . . . 3
3.2. The "$Origin-" prefix . . . . . . . . . . . . . . . . . . 3
3.3. The "$SecureOrigin-" prefix . . . . . . . . . . . . . . . 4
4. User Agent Requirements . . . . . . . . . . . . . . . . . . . 4
5. Aesthetic Considerations . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Section 8.5 and Section 8.6 of [RFC6265] spell out some of the
drawbacks of cookies' implementation: due to historical accident, it
is impossible for a server to have confidence that a cookie set in a
secure way (e.g., as a domain cookie with the "Secure" (and possibly
"HttpOnly") flags set) remains intact and untouched by non-secure
subdomains.
We can't alter the syntax of the "Cookie" request header, as that
would likely break a number of implementations. This rules out
sending a cookie's flags along with the cookie directly, but we can
smuggle information along with the cookie if we reserve certain name
prefixes for cookies with certain properties.
This document describes such a scheme, which enables servers to set
cookies which conforming user agents will ensure are "Secure", and
locked to a domain.
2. Terminology and notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The "scheme" component of a URI is defined in Section 3 of [RFC3986].
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3. Prefixes
3.1. The "$Secure-" prefix
If a cookie's name begins with "$Secure-", the cookie MUST be set
with a "Secure" attribute.
The following cookie would be rejected:
Set-Cookie: $Secure-SID=12345; Domain=example.com
While the following would be accepted:
Set-Cookie: $Secure-SID=12345; Secure; Domain=example.com
3.2. The "$Origin-" prefix
If a cookie's name begins with "$Origin-", the cookie MUST be:
1. Sent only to hosts which are identical to the host which set the
cookie. That is, a cookie named "$Origin-cookie1" set from
"https://example.com" MUST NOT contain a "Domain" attribute (and
will therefore sent only to "example.com", and not to
"subdomain.example.com").
2. Sent to every request for a host. That is, a cookie named
"$Origin-cookie1" MUST contain a "Path" attribute with a value of
"/".
3. Sent only to secure origins, if set from a secure origin. That
is, a cookie named "$Origin-cookie1" set from
"https://example.com" MUST contain a "Secure" attribute, as it
was set from a URI whose "scheme" is considered "secure" by the
user agent.
The following cookies would always be rejected:
Set-Cookie: $Origin-SID=12345
Set-Cookie: $Origin-SID=12345; Secure
Set-Cookie: $Origin-SID=12345; Domain=example.com
Set-Cookie: $Origin-SID=12345; Secure; Domain=example.com
The following would be rejected, if set from a secure origin, but
accepted if set from a non-secure origin:
Set-Cookie: $Origin-SID=12345; Path=/
While the following would be accepted, if set from a secure origin:
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Set-Cookie: $Origin-SID=12345; Secure; Path=/
3.3. The "$SecureOrigin-" prefix
If a cookie's name begins with "$SecureOrigin-", the cookie MUST be:
1. Sent only to hosts which are identical to the host which set the
cookie. That is, a cookie named "$SecureOrigin-cookie1" set from
"https://example.com" MUST NOT contain a "Domain" attribute (and
will therefore sent only to "example.com", and not to
"subdomain.example.com").
2. Sent to every request for a host. That is, a cookie named
"$SecureOrigin-cookie1" MUST contain a "Path" attribute with a
value of "/".
3. Sent only to secure origins. That is, a cookie named
"$SecureOrigin-cookie1" MUST contain a "Secure" attribute.
4. User Agent Requirements
This document updates Section 5.3 of [RFC6265] as follows:
After step 10 of the current algorithm, the cookies flags are set.
Insert the following steps to perform the prefix checks this document
specifies:
1. If the "cookie-name" begins with the string "$Origin-", then:
1. If the "scheme" component of the "request-uri" denotes a
"secure" protocol (as determined by the user agent), and the
cookie's "secure-only-flag" is "false", abort these steps and
ignore the cookie entirely.
2. If the cookie's "host-only-flag" is "false", abort these
steps and ignore the cookie entirely.
3. If the cookie's "path" is not "/", abort these steps and
ignore the cookie entirely.
2. If the "cookie-name" begins with the string "$Secure-", and the
cookie's "secure-only-flag" is "false", abort these steps and
ignore the cookie entirely.
3. If the "cookie-name" begins with the string "$SecureOrigin-",
then:
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1. If the cookie's "secure-only-flag" is "false", abort these
steps and ignore the cookie entirely.
2. If the cookie's "host-only-flag" is "false", abort these
steps and ignore the cookie entirely.
3. If the cookie's "path" is not "/", abort these steps and
ignore the cookie entirely.
5. Aesthetic Considerations
Prefixes are ugly. :(
6. Security Considerations
This scheme gives no assurance to the server that the restrictions on
cookie names are enforced. Servers could certainly probe the user
agent's functionality to determine support, or sniff based on the
"User-Agent" request header, if such assurances were deemed
necessary.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011,
<http://www.rfc-editor.org/info/rfc6265>.
Appendix A. Acknowledgements
Eric Lawrence had this idea a million years ago. Devdatta Akhawe
helped justify the potential impact of the scheme on real-world
websites.
Author's Address
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Mike West
Google, Inc
Email: mkwst@google.com
URI: https://mikewest.org/
West Expires April 11, 2016 [Page 6]