Oblivious Proxy Feedback
draft-rdb-ohai-feedback-to-proxy-01
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 "Expired".
|
|
|---|---|---|---|
| Authors | Tirumaleswar Reddy.K , Dan Wing , Mohamed Boucadair | ||
| Last updated | 2022-03-20 | ||
| 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-rdb-ohai-feedback-to-proxy-01
ohai T. Reddy
Internet-Draft Akamai
Intended status: Standards Track D. Wing
Expires: 21 September 2022 Citrix
M. Boucadair
Orange
20 March 2022
Oblivious Proxy Feedback
draft-rdb-ohai-feedback-to-proxy-01
Abstract
To provide equitable service to clients, servers often rate-limit
incoming requests, often based upon the source IP address. However,
oblivious HTTP removes the ability for the server to distinguish
amongst clients so the server can only rate-limit traffic from the
oblivious proxy. This harms all clients behind that oblivious proxy.
This specification provides feedback from a server to an oblivious
proxy, enabling the oblivious proxy to rate-limit incoming requests
from clients. Cooperating oblivious proxies can thus provide more
equitable service to their distinguishable clients without triggering
rate-limiting on the request resource or the target resource that
would impact all clients behind that Oblivious proxy.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 21 September 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
Reddy, et al. Expires 21 September 2022 [Page 1]
Internet-Draft Oblivious Proxy Feedback March 2022
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Ohai-Proxy-Feedback Header . . . . . . . . . . . . . . . . . 4
4. Ohai-Proxy-Feedback Header Parameters . . . . . . . . . . . . 5
5. Request or Target Resource Generating Ohai-Proxy-Feedback
Header . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Proxy Processing of Ohai-Proxy-Feedback Header . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8.1. Registration of new HTTP Header Field . . . . . . . . . . 9
8.1.1. Ohai-Proxy-Feedback Header . . . . . . . . . . . . . 9
8.1.2. Ohai-Proxy-Feedback Parameter Name Registry . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Oblivious HTTP [I-D.ietf-ohai-ohttp] describes a method of
encapsulation for binary HTTP messages [BINARY] using Hybrid Public
Key Encryption (HPKE; [HPKE]). This protects the content of both
requests and responses and enables a deployment architecture that can
separate the identity of a requester from the request. This scheme
requires that servers and proxies explicitly support it. The server
is susceptible to attacks described below, but the server cannot take
any mitigation action per client to protect itself from various
attacks -- the server can only take mitigation actions per oblivious
proxy. Rate-limiting traffic from an oblivious proxy impacts all
clients behind that proxy -- both misbehaving clients and well-
behaved clients.
Attacks against the Request and Target Resources can be classified
into three primary categories:
Reddy, et al. Expires 21 September 2022 [Page 2]
Internet-Draft Oblivious Proxy Feedback March 2022
1. A client sends a malformed encapsulated request causing
decryption failure or decryption overload failure on the
oblivious request resource. This causes the oblivious request
resource to send an error status code back to the oblivious
proxy.
2. A client sends an HTTP transaction that causes an HTTP error on
the oblivious target resource. This might be a malformed HTTP
request, or request for a missing resource.,
3. HTTP flood: A botnet performing an HTTP flood attack against a
victim's server. Because each bot in a botnet makes seemingly
legitimate network requests the traffic is not spoofed and may
appear "normal" in origin. This might be too many requests from
a single client, too many requests from the clients behind the
same oblivious proxy or too many requests from all clients on the
Internet.
This document defines how an overload indication is communicated to
an oblivious proxy so that this proxy can rate limit transactions by
overzealous or misbehaving clients, allowing the oblivious proxy to
continue servicing well-behaved clients to that same oblivious target
resource.
"RateLimit Fields for HTTP" specification
[I-D.ietf-httpapi-ratelimit-headers] allows servers to publish
current service limits to clients, whereas this draft allows servers
to publish current service limits to oblivious proxies. The former
specification allows clients to shape their request policy and avoid
being throttled out, whereas this specification allows oblivious
proxies to shape their request policy and avoid being throttled out.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document makes use of the terms defined in
[I-D.ietf-ohai-ohttp].
Reddy, et al. Expires 21 September 2022 [Page 3]
Internet-Draft Oblivious Proxy Feedback March 2022
3. Ohai-Proxy-Feedback Header
The "Ohai-Proxy-Feedback" header field is defined in this
specification. The Ohai-Proxy-Feedback header provides feedback
information from the request resource or target resource to the proxy
in the HTTP response. The proxy MUST remove the Ohai-Proxy-Feedback
header before sending the HTTP response containing the encapsulated
response to the client. If the feedback information is generated by
the request resource before removing the protection (including being
unable to remove encapsulation for any reason)(see Section 6.2 of
[I-D.ietf-ohai-ohttp]), it will result in the Ohai-Proxy-Feedback
Header added in the status code being sent without protection in
response to the POST request from the client.
Figure 1 describes the syntax (Augmented Backus-Naur Form) of the
header field, using the grammar defined in [RFC5234] and the rules
defined in Section 3.2 of [RFC7230]. The field values of the header
field conform to the same rules.
Ohai-Proxy-Feedback = feedback-parameter *( OWS ";" OWS feedback-parameter)
feedback-parameter =
feedback-parameter-name [ "=" feedback-parameter-value ]
feedback-parameter-name = registered-token
registered-token = token
feedback-parameter-value = 1*DIGIT
Figure 1: Ohai-Proxy-Feedback Header Syntax
[[NOTE: CHECK IF WE CAN REUSE THE STRUCTURED FIELDS IN RFC 8941]]
Optional white space (OWS) is used as defined in Section 3.2.3 of
[RFC7230] and token is used as defined in Section 3.2.6 of [RFC7230].
The overall processing of the parameters is discussed below:
1. The order of appearance of the parameters is not significant.
2. A given parameter MUST NOT appear more than once in the Ohai-
Proxy-Feedback header.
3. Parameters are either optional or required, as explicited in
their definitions.
4. Parameter names are case insensitive.
Reddy, et al. Expires 21 September 2022 [Page 4]
Internet-Draft Oblivious Proxy Feedback March 2022
5. Proxies MUST ignore any parameters or values, that do not conform
to the syntax defined in this specification. In particular,
proxies must not attempt to fix malformed parameters or parameter
values.
6. If the parameter is not recognized by the proxy, it MUST be
ignored by the proxy.
4. Ohai-Proxy-Feedback Header Parameters
The feedback information includes the following parameters:
RateLimit-p-Limit: It indicates the maximum number of requests that
the server is willing to accept from the proxy. This is an
optional attribute.
RateLimit-p-Reset: It indicates the number of seconds until the
maximum number of requests quota resets for the proxy. This is an
optional attribute.
RateLimit-p-outstanding-Limit: It indicates the maximum number of
outstanding requests that the server is willing to accept from the
proxy. This is an optional attribute.
RateLimit-p-outstanding-Reset: It indicates the number of seconds
until the maximum number of outstanding requests quota resets for
the proxy. This is an optional attribute.
RateLimit-Limit: It indicates the maximum number of requests that
the server is willing to accept from the offending client. It is
defined in Section 5.1 of [I-D.ietf-httpapi-ratelimit-headers].
This is an optional attribute.
RateLimit-Reset: It indicates the number of seconds until the
maximum number of requests quota resets for the offending client.
It is defined in Section 5.3 of
[I-D.ietf-httpapi-ratelimit-headers]. This is an optional
attribute.
RateLimit-Outstanding-Limit: It indicates the maximum number of
outstanding requests that the server is willing to accept from the
offending client. This is an optional attribute.
RateLimit-Outstanding-Reset: It indicates the number of seconds
until the maximum number of outstanding requests quota resets for
the offending client. This is an optional attribute.
Reddy, et al. Expires 21 September 2022 [Page 5]
Internet-Draft Oblivious Proxy Feedback March 2022
TBD: Use of any other parameters like min-encap-request-size and max-
encap-request-size to defend from garbled encapsulated requests.
TBD: RateLimit-Outstanding-Limit parameter is not specific to OHAI
and it can be added to [I-D.ietf-httpapi-ratelimit-headers].
Note that we plan to use short parameter names in future versions of
the draft as recommended by [I-D.ietf-httpbis-bcp56bis].
The above parameters are in the form of a "name=value" pair.
The feedback information header MUST include at least one of the
parameters RateLimit-p-Limit, RateLimit-p-outstanding-Limit,
RateLimit-Limit, or RateLimit-Outstanding-Limit.
The RateLimit-Limit, RateLimit-Reset, RateLimit-Outstanding-Limit,
and RateLimit-Outstanding-Reset parameters are set if the client is
attacking the server (e.g., the client using an abnormal header that
matches an attack rule).
Example: A target resource receives a malformed message and generates
an HTTP response with a 400 status code. It adds the "Ohai-Proxy-
Feedback" header with the appropriate rate limit values to the 400
response and then sends the 400 response to the request resource.
The request resource copies the "Ohai-Proxy-Feedback" header from the
400 response, removes the "Ohai-Proxy-Feedback" header from the 400
response, and encapsulates the 400 response. The request resource
sends a single 200 response along with the copied "Ohai-Proxy-
Feedback" header in the 200 response and encapsulated 400 response as
the response content.
Reddy, et al. Expires 21 September 2022 [Page 6]
Internet-Draft Oblivious Proxy Feedback March 2022
+----+ +----------+ +----------+ +-----------+
| C | | Proxy | | Request | | Target |
| | | Resource | | Resource | | Resource |
+-+--+ +----+-----+ +-----+----+ +------+----+
| | | |
| Encapsulated | | |
+--------------------->| | |
| Request | | |
| | Encapsulated | |
| +--------------------->| |
| | Request | |
| | | Request | .---------.
| | +--------------------->| | Identify|
| | | +-+malformed|
| | | | | request |
| | | 400 response | '---------'
| | |<---------------------+
| | | |
| | 200 response with | |
| | Ohai-Proxy-Feedback | |
| | Header and | |
|<---------------------+ |
.---------------------. | Encapsulated 400 | |
| Process | | response | |
| Ohai-Proxy-Feedback +--+ | |
| and applies | | | |
| rate-limit for the | | | |
| offending client | | | |
'---------------------' | | |
| | |
| | | |
| Encapsulated 400 | | |
|<---------------------+ | |
| response | | |
| | | |
Figure 2: An Example of Feedback to Proxy
The response constructed by the oblivious request resource is
depicted below:
HTTP/1.1 200 OK
Date: Wed, 27 March 2022 04:45:07 GMT
Cache-Control: private, no-store
Ohai-Proxy-Feedback: RateLimit-p-Limit=10000; RateLimit-p-Reset=600
Content-Type: message/ohttp-res
Content-Length: 38 <content is the encapsulated 400 response>
Reddy, et al. Expires 21 September 2022 [Page 7]
Internet-Draft Oblivious Proxy Feedback March 2022
5. Request or Target Resource Generating Ohai-Proxy-Feedback Header
When an overload is experienced by the request or target resource it
adds the Ohai-Proxy-Feedback header and parameters to request load
adjustment. For example, when a HTTP server itself identifies high
frequency or high volume anomalies in the traffic directed to the
server it would include the Ohai-Proxy-Feedback header. Ideally the
Ohai-Proxy-Feedback header provides enough detail to the oblivious
proxy to avoid the server rate limiting the oblivious proxy's IP
address.
6. Proxy Processing of Ohai-Proxy-Feedback Header
When presented with a response that contains the Ohai-Proxy-Feedback
Header, the proxy can process the parameters in the header and take
appropriate actions. There is no mechanism for the proxy to indicate
to the server that feedback information was processed or was ignored.
The proxy can honor the rate indicated by the request resource/
resource target. To that aim, the proxy may take appropriate
additional actions such as (1) rate-limiting the requests from a
client not to exceed requests per second (RateLimit-Limit) value (2)
rate-limit the outstanding HTTP requests from a client not to exceed
outstanding requests (RateLimit-Outstanding-Limit) value.
If the proxy ignores the feedback information, there is a risk that
the overload may still be encountered by the request and target
resources. More severe actions may be, then, taken at the server,
e.g., block all the requests from this proxy for a given time
duration.
7. Security Considerations
The security considerations for the Oblivious HTTP protocol are
discussed in Section 8 of [I-D.ietf-ohai-ohttp]. The client needs to
trust the proxy that it does not leak the client identity to the
server. The target and request resources SHOULD convey the Ohai-
Proxy-Feedback header to trusted oblivious proxy. However, if this
oblivious proxy is not trusted, security risks discussed below may
arise:
* If oblivious proxy and clients attacking the server are managed by
an attacker, the attacker can use the Feedback information to
identify the server has detected the attack and possibly change
the attack strategy.
* The oblivious proxy can colloude with the attacking clients and
leak the Feedback information to the clients.
Reddy, et al. Expires 21 September 2022 [Page 8]
Internet-Draft Oblivious Proxy Feedback March 2022
8. IANA Considerations
8.1. Registration of new HTTP Header Field
8.1.1. Ohai-Proxy-Feedback Header
This section describes a header field for registration in the
Permanent Message Header Field Registry [RFC3864].
Header field name
Feedback
Applicable protocol
http
Status
standard
Author/Change controller
IETF
Specification document(s)
RFC XXXX
Related information
This header field is only used for Oblivious HTTP.
8.1.2. Ohai-Proxy-Feedback Parameter Name Registry
This specification requests the creation of a new IANA registry for
Feedback Parameter Names to be sent in the Feedback Header in
accordance with the principles set out in [RFC5226].
As part of this registry IANA will maintain the following
information:
Parameter Name
The name of the parameter.
9. Acknowledgements
Thanks to Lucas Pardue, Rich Salz and Brandon Williams for the
discussion and comments.
10. References
10.1. Normative References
Reddy, et al. Expires 21 September 2022 [Page 9]
Internet-Draft Oblivious Proxy Feedback March 2022
[BINARY] Thomson, M. and C. A. Wood, "Binary Representation of HTTP
Messages", Work in Progress, Internet-Draft, draft-ietf-
httpbis-binary-message-01, 3 February 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
binary-message-01>.
[HPKE] Barnes, R. L., Bhargavan, K., Lipp, B., and C. A. Wood,
"Hybrid Public Key Encryption", Work in Progress,
Internet-Draft, draft-irtf-cfrg-hpke-12, 2 September 2021,
<https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-
hpke-12>.
[I-D.ietf-httpapi-ratelimit-headers]
Polli, R. and A. M. Ruiz, "RateLimit Fields for HTTP",
Work in Progress, Internet-Draft, draft-ietf-httpapi-
ratelimit-headers-03, 7 March 2022,
<https://www.ietf.org/archive/id/draft-ietf-httpapi-
ratelimit-headers-03.txt>.
[I-D.ietf-ohai-ohttp]
Thomson, M. and C. A. Wood, "Oblivious HTTP", Work in
Progress, Internet-Draft, draft-ietf-ohai-ohttp-01, 15
February 2022, <https://www.ietf.org/archive/id/draft-
ietf-ohai-ohttp-01.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
Reddy, et al. Expires 21 September 2022 [Page 10]
Internet-Draft Oblivious Proxy Feedback March 2022
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10.2. Informative References
[I-D.ietf-httpbis-bcp56bis]
Nottingham, M., "Building Protocols with HTTP", Work in
Progress, Internet-Draft, draft-ietf-httpbis-bcp56bis-15,
27 August 2021, <https://www.ietf.org/archive/id/draft-
ietf-httpbis-bcp56bis-15.txt>.
Authors' Addresses
Tirumaleswar Reddy
Akamai
Embassy Golf Link Business Park
Bangalore 560071
Karnataka
India
Email: kondtir@gmail.com
Dan Wing
Citrix Systems, Inc.
4988 Great America Pkwy
Santa Clara, CA 95054
United States of America
Email: danwing@gmail.com
Mohamed Boucadair
Orange
35000 Rennes
France
Email: mohamed.boucadair@orange.com
Reddy, et al. Expires 21 September 2022 [Page 11]