Internet DRAFT - draft-chen-httpbis-window-size-use-case
draft-chen-httpbis-window-size-use-case
httpbis M. Chen
Internet-Draft Li. Su
Intended status: Informational China Mobile
Expires: December 17, 2021 June 15, 2021
http2 window size use case
draft-chen-httpbis-window-size-use-case-01
Abstract
This document presents an use case which actually happening in our
network, when window_size_increment in the window update frame less
than 128 bytes and the increased window size also less than 128
bytes, then network connection will come to an error.
Status of This Memo
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This Internet-Draft will expire on December 17, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 4
7. Informative References . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
The following content is from RFC 7540[RFC7540]
When an HTTP/2 connection is first established, new streams are
created with an initial flow-control window size of 65,535 octets.
The connection flow-control window is also 65,535 octets. Both
endpoints can adjust the initial window size for new streams by
including a value for SETTINGS_INITIAL_WINDOW_SIZE in the SETTINGS
frame that forms part of the connection preface. The connection
flow-control window can only be changed using WINDOW_UPDATE frames.
SETTINGS_INITIAL_WINDOW_SIZE (0x4): Indicates the sender's initial
window size (in octets) for stream-level flow control. The initial
value is 2^16-1 (65,535) octets.
Window Size Increment defined in the Window_update is 31, the legal
range for the increment to the flow-control window is 1 to 2^31-1
(2,147,483,647) octets.
RFC 7540 just Specifies the maximum value of Window and the Window
Size Increment, But there is no obvious rule about minimum values.
2. Terminology
The readers should be familiar with the terms defined in.
In addition, this document makes use of the following terms:
Window_update: The WINDOW_UPDATE frame (type=0x8) is used to
implement flow control;
3. Use Case
This section describes use case which happens between two different
manufacturers. They both use HTTP2.0 protocol to transmit messages.
We found this phenomenon, one issues a regular registration request,
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the other one receives the request, but judged to be attack
behaviour.
+---------+ +----------+
| Sender | |Receiver |
| | | |
+----+----+ +-----+----+
| Reqistration request |
+----------------------------------->
| |
| |
+----------------------------------->
| Http2 Window_update |
| (condition1:window size |
| increment) |
| |window+=window size increment
| |condition2: window
| |
| |condition1<128bytes
| connection break |& condition2<128bytes
| +-------------------------+ |=attack behaviour
| |
| Registration Failed |
+<----------------------------------+
+ +
Figure 1: A normal request is considered an attack
Why determine abnormal attack behavior, the analysis is as follows:
The default initial window size defined by the protocol is 64K.
After the data in the receiving window is removed, part of the window
occupied by the original data is released.
If there is a large backlog of data in the original receiving window
that has not been removed, resulting in a small remaining window, the
window added after the normal removal of data will not be too small.
If there is little backlog of data in the original receiving window,
the window that needs to be added after the data is removed will be
small, but the overall available window after the adjustment will be
larger. In neither case will the window be too small, So the
connection considered to be an attack.
So when need to solve this problem, two approaches can be discussed,
specifying a minimum value for window and window size increment, or
increasing more detailed flow control strategies.
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4. Security Considerations
Failure to set a minimum will result in frequent window_update if
only process a small amount of data at a time, it is likely to occur
Denial of service attacks, it would be fatal if it happened in an
Internet of Things scenario. In draft-ietf-httpbis-http2bis, there
are also Denial-of-Service consideration in section 10.5, includes
the misuse of some parameters and priorities.
5. IANA Considerations
This document does not require any action from IANA.
6. Acknowledgement
TBD
7. Informative References
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>.
Authors' Addresses
Meiling Chen
China Mobile
32, Xuanwumen West
BeiJing, BeiJing 100053
China
Email:
chenmeiling@chinamobile.com
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Li Su
China Mobile
32, Xuanwumen West
BeiJing
100053
China
Email:
suli@chinamobile.com
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