HTTPbis Yongming Zhao
Internet-Draft Alibaba, Inc
Intended status: Standards Track Qinghuan Min
Expires: April 23, 2015 Alibaba, Inc
Xixi Xiang
Alibaba, Inc
Rui Chen
Alibaba, Inc
October 22, 2014
Hypertext Transfer Protocol: Access Control List
draft-zhao-http-acl-00
Abstract
In current Internet, HTTP/1.1 or HTTP/2 protocol has limited methods to
control resource access. Usually it's achieved by modifying the
configuration of the cache and proxy to enforce the access control
rules. When original server's access control list (ACL) is updated,
a reconfiguration of cache and proxy systems on the chain is
required for the change to take effect, which always impacts the
network stability. This document introduces a new access control
mechanism, which introduces a new header field to dynamically
control resource access.
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Table of Contents
1. Introduction 2
1.1. Requirements Language 3
2. Specification 3
2.1. HTTP header field extension 3
2.2. Mapping rule of X-Referer-ACL field 5
2.3. how to handle the cache expires time 6
3. Security Considerations 6
4. IANA Considerations 6
4.1. Header Field Registration 6
5. References 7
5.1. Normative References 7
5.2. Informative References 7
1. Introduction
In HTTP/1.1 or HTTP/2 protocol, there are few simple methods to
control resource access. These methods might not work well with
caches and proxies, which are widely used in current Internet.
Considering following case:
There some proprietary resources (html or image) in Web server,
which should be accessed only by authorized requests. If the
website is accelerated by CDN (Content Delivery Network),
proprietary resources might be cached by servers in CDN. Thus
access control should also be required on cache servers.
Practically it's neither possible nor efficient to have same
authorization mechanism as original web server on all cache
servers. HTTP 1.1 provides a simple solution by using "referrer"
header field to validate incoming requests, which is widely used
in CDN. But the solution has some drawbacks:
1. Inefficient with large scale networks
A proprietary resource could be cached publicly by cache or
proxy after a legal request with proper "referrer" head was
responded by original server, which means the designated access
control is invalidated in this node. Following requests to
cache or proxy with any "referrer" could access the resource.
In order to protect the resource, access control should be
enforced in each cache and proxy in the network. It's
troublesome and involving huge configuration work in a large
scale networks with thousands of caches and proxies even with
automation tool.
2. Inefficient with dynamic rule
The resource access control list may be updated frequently.
The changed to access control list at original sever should be
populated to caches and proxies in the network as soon as
possible, or it means unexpected responses to user requests.
Even with automation tool, there could be significant delay of
populating in network with lots of caches and proxies.
Practically, applying new access control might involve
reloading configuration or even rebooting, which could have
potential bad effect on network stability.
The goal in this proposal is to overcome the drawbacks mentioned
and provide a better solution. A new header field is proposed to
help cache and proxy to sync the access control rule from
original server efficiently. The benefit of this solution
increases as the number of cache and proxy in the network goes up.
This method can be used in combination with HTTP/1.1 or HTTP/2.
1.1. Requirements Language
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 RFC 2119
[RFC2119].
2. Specification
The detail description of our approach as follow three sections:
Section 2.1 introduces a new header field X-REFERER-ACL. This
field is only set in response header by original server. All
original servers, caches and proxies MUST check the request with
certain rule.
Section 2.2 introduces the mapping rules of X-REFERER-ACL. We will
give some examples to show the checking routine.
Section 2.3 describes rule of how to handle the cache expires time.
2.1. HTTP header field extension
A new header field named "X-Referer-ACL" is introduced. This
header field MUST be only set in response header, if it is set in
request header, original server, cache or proxies MUST ignore it.
Here's the format of the new header field:
X-Referer-ACL = X-Referer-ACL: ACTION TYPE PARAMS
ACTION = "A" | "D"
A = Allow ALL
D = Deny ALL
TYPE = "*" | "1" | "2"
* = Matching ALL
1 = Matching Domain
2 = Matching Hostname
PARAMS=","token
Description:
1. ACTION is a flag which indicates allow or deny. This value MUST
be one of the upper case "A" or "D".
"A" means Allow ALL. We can also consider it as "white list".
"D" means Deny ALL. We can also consider it as "black list".
2. TYPE value is a single character, it indicates the mapping type.
* means to check all type.
1 means to check domain name. It MUST check only domain name of
referer field of request.
2 means to check hostname name. It MUST check only hostname of
referer field of request.
3. PARAMS is parameter list. The item of PARAMS is hostname or
domain name, which is determined by "TYPE" value. The list item
must be separated by comma.
How to set the value:
If TYPE="*", it means no matter hostname or domain name will be
checked. PARAMS is optional and should be ignored.
If TYPE="1", domain name checking. PARAMS is the list of domain
name which is allowed or denied to access the resource. Domain
name MUST not has (.) in the headmost.
If TYPE="2", hostname checking. RARAMS is the list of hostname
list which is allowed or denied to access the resource.
4. X-Referer-ACL may include several ACTION TYPE PARAMS items
separated by semi-colon (;). ACTION TYPE PARAMS items should be
match one by one in order.
Here is an example:
X-Referer-ACL: A 1 A.B.taobao.com; D 1 B.taobao.com; A 1 taobao.com, taobaocdn.com; D*
The meaning of the header field value above is: allow A.B.taobao.com,
taobao.com and taobaocdn.com and their child domain name access the
resource. Deny B.taobao.com and any other domain name access it.
2.2. Matching rule of X-Referer-ACL field
No matter caches or proxies, when receiving the X-Referer-ACL header
field in response, they MUST observe the rule as following:
1. If there is no X-Referer-ACL field in the response, caches
and proxies should allow all request to access the resource and no
need to do any check.
2. If there is no referer in request, caches and proxies should
not check the request, even if response has the X-Referer-ACL
field.
3. If request has referer field and response has X-Referer-ACL,
caches and proxies MUST check rule of X-Referer-ACL field and
decide whether to allow or deny current request.
4.If refer doesn't match any X-Refer-
ACL rule, the request SHOULD be allowed unconditionally.
There are some more notices for our matching rule:
a) X-Referer-ACL field MUST appear only once. It is for
simplifying the macthing rule.
b) If there are more than one parameter list matching the request,
the first mapping value's ACTION should be used.
c) If the first ACTION TYPE PARAMS is D*, all requests should be
rejected. If the first ACTION TYPE PARAMS is A*, all requests should
be allowed.
d) If referer is not set in the request or the value of this field
is empty, original server, cache and proxies will allow this request
unconditionally.
e) If referer's value is not a correct URI (not http or https),
the request should be denied with HTTP 403.
f) Hostname and domain name would be normalized to lower case
before matching procedure.
We believe that the new field introduced in section 2.1 and the
rule defined in section 2.2 would help to enforce access control in
large scale network more efficiently.
2.3. How to handle the cache expiration time
If the resource being requested in the cache server is already
expired, the cache server MUST send a GET request with "If-Modify-
Since" to original server to check whether the resource is changed
or not. Original server should return HTTP 200 if the resource is
changed. HTTP 304 Not Modified should be returned if the resource
is untouched and the X-Referer-ACL MUST be included in the
response header.
3. Security Considerations
The new field introduced in this proposal is related with anti-
theft and access control. Cache server MUST record the X-Referer-
ACL rule of response. X-Referer-ACL MUST set in header of response
every time as HTTP request has no status. Once response doesn't
have the X-Referer-ACL at any time, the cache system will remove
the old ACL rule immediately, which will invalidate the access
control and expose the resource to the risk of unauthorized access.
Cache server MUST not change any of the X-Referer-ACL values
because any change would make the original server access control
invalidated. Cache servers and proxies MUST follow section 2.1 and
section 2.2 to check the entire request. Failing to follow might
access control invalidation.
4. IANA Considerations
4.1. Header Field Registration
HTTP header fields are registered within the Message Header Field
Registry maintained at [1].
This document defines the following HTTP header fields, so their
associated registry entries shall be updated according to the
permanent registrations below (see [BCP90]):
+-------------------+----------+-------------------+--------------+
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+-------------------+--------------+
| X-Referer-ACL | http | proposed standard | Section 2.1 |
+-------------------+----------+-------------------+--------------+
The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
5. References
5.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
5.2. Informative References
[3] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP
and Its Effect on Busy Servers", Proc. Infocom 1999 pp.
1573-1583.
[Fab1999] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in
TCP and Its Effect on Busy Servers", Proc. Infocom 1999
pp. 1573-1583.
Authors' Addresses
Yongming Zhao
0825, BUILDING North 4, ZHONGHONG BEIJINGXIANGSU, #1 WULIQIAOYIJIE
CHANGYING, CHAOYANG, BEIJING
China
Email: zym@efengcloud.com
QingHuan Min
Alibaba
No.1 East 3rd Ring Middle Rd
Chaoyang District, Beijing
China
Email: zongyi.mqh@taobao.com
XiXi Xiang
Alibaba
HangZhou, ZheJiang province,
China
Email: xixi.xxx@alibaba-inc.com
Rui Chen (editor)
Alibaba
No.1 East 3rd Ring Middle Rd
Chaoyang District, Beijing
China
Email: zhuquan.cr@taobao.com