Internet DRAFT - draft-francois-ipv6-dots-signal-option
draft-francois-ipv6-dots-signal-option
DOTS J. Francois
INTERNET-DRAFT Inria
Intended Status: Standard Track A. Lahmadi
Expires: September 22, 2016 University of Lorraine - LORIA
Giovane C. M. Moura
SIDN Labs
Marco Davids
SIDN Labs
March 21, 2016
IPv6 DOTS Signal Option
draft-francois-ipv6-dots-signal-option-00
Abstract
This document describes a delivery mechanism based on the IPv6 Hop-
by-Hop options extension header type to carry a DOTS client signal
message over a congested network due to a DDoS attack. The specified
mechanism allows the DOTS client signal message to be included using
an opportunistic way in outgoing IPv6 packets traveling then through
the network to reach a DOTS server or relay.
Status of this Memo
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Copyright and License Notice
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Copyright (c) 2016 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
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Opportunistic DOTS signal format . . . . . . . . . . . . . . . 5
2.1 Hop-by-Hop option encoding . . . . . . . . . . . . . . . . . 5
2.2 DOTS signal Option attributes . . . . . . . . . . . . . . . 6
2.3 Example . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Option Processing . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Opportunistic DOTS signal initialization by a DOTS client . 7
3.2 Processing by a non DOTS opportunistic-capable router . . . 8
3.3 Processing by a DOTS opportunistic-capable router . . . . . 9
3.4 Processing by a DOTS opportunistic-capable relay . . . . . . 9
3.5 Processing by a DOTS opportunistic-capable server . . . . . 9
4 Impact on existing IP layer implementations . . . . . . . . . . 9
5 Security Considerations . . . . . . . . . . . . . . . . . . . . 10
6 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1 Normative References . . . . . . . . . . . . . . . . . . . 10
7.2 Informative References . . . . . . . . . . . . . . . . . . 11
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1 Introduction
1.1 Overview
A distributed denial-of-service (DDoS) attack aims at rendering
machines or network resources unavailable. These attacks have grown
in frequency, intensity and target diversity [I-D.draft-ietf-dots-
requirements]. Moreover, several protocols have been utilized to
amplify the intensity of the attacks [kuhrer2014exit], often peaking
at several hundred gigabits per second.
The DOTS aims at defining a common and open protocol to signal DDoS
attacks to facilitate a coordinated response to these attacks. This
document defines a signalling mechanism that instead of designing a
new application-layer protocol, it utilizes the IPv6 Hop-by-Hop
header [RFC2460]. This header has the advantage to be fully inspected
by all network devices and it is the first header in IPv6 extension
headers [RFC7045].
The new option containing the attributes of the signalling message
is included in an opportunistic way in available IPv6 packets leaving
a network element until the message reaches a DOTS server. It thus
constitutes an additional signalling channel but MUST NOT replace the
original signalling channel used between DOTS client and servers as
the one defined in [I-D.draft-reddy-dots-transport]. The DOTS client
will thus embed the signalling attributes into outgoing IPv6 packets
not necessarily going to the DOTS server. Intermediate routers
receiving such a packet will examine it and embed the same
information into other IPv6 packets. The process continues in this
opportunistic manner to increase the probability that such a packet
will be finally forwarded to a DOTS Relay or Server.
Only the Hop-by-Hop options header allows such behavior and using
Destination options header is not enough to make the DOTS signal
going through the network in an opportunistic way. Each network
element recognizing this new option will select the best fitted IPv6
packets to deliver the signal to the DOTS server or relay. For
this reason the Hop-by-Hop header option is essential to make such
behavior compared to other existing IPv6 extension headers [RFC6564].
It is also important to emphasize that while our mechanism utilizes
an IPv6 header field, it can also be used signal IPv4 attacks as well
- given that the network devices are dual stacked.
1.2 Motivation
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The traffic generated by a DDoS can be characterized according to
various parameters, such as the layer (IP/ICMP or application),
maximum and instant throughput, among others. Regardless its nature,
we assume that for most cases, a DOTS client will be able to signal
back one or few messages , during the attack, to the DOTS phase.
We have the same behavior in other DDoS attacks. For instance, on
November 30th and December 1st, 2015, the Root DNS system was hit by
an application layer (DNS) attack [rootops-ddos]. Each one of the 13
root server letters (A--M) was hit by attacks peaking at 5 million
queries per second. By utilizing the RIPE Atlas DNSMON
infrastructure, we can see that during the DDoS attacks, most of the
root server letters remained reachable and able to respond to the DNS
request sent by the probes employed by the DNSMON [ripe-dnsmon-ddos].
Few letters, however, had a packet loss rate of more than 99%. The
DNSMON probes, however, experience mostly delays in their DNS
requests instead.
Our signalling mechanism operates in an opportunistic way it is
designed for DDoS as the ones on the Root DNS system.
1.3 Terminology
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].
The terms DOTS client, DOTS server, DOTS relay, DOTS agents, signal
channel, DOTS signal and DOTS signal refers to the terminology
introduced in [I-D.draft-ietf-dots-requirements].
The following terms are introduced:
Opportunistic DOTS signal :
an IPv6 packet containing the signalling attributes of an
attack within the Hop-by-Hop extension header. The purpose is
the same as the DOTS signal. It is used to request help for
mitigating the attack.
DOTS opportunistic-capable router:
a router with the capacity to decode the opportunistic DOTS
signal and re-embed such an information in other IPv6 packets.
All DOTS opportunistic-capable agent are defined as the DOTS
agents supporting the opportunistic DOTS signal processing.
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2. Opportunistic DOTS signal format
The goal is to provide an efficient mechanism where nodes in a
network facing a DDoS attack can deliver a DOTS signal message
sent by a DOTS client to the DOTS server. The solution defines a
new IPv6 Hop-by-Hop header option with the semantic that the
network node SHOULD include the option content within one or
multiple outgoing IPv6 packets.
2.1 Hop-by-Hop option encoding
According to [RFC2460], options encoded into the IPv6 Hop-by-Hop
header are formatted as Type-Length-Values (TLVs). The option for
opportunistic DOTS signal is thus defined as follows:
0 7 15 22 31
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option type |Option Data Len| DOTS Signal Attribute[1] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DOTS Signal Attribute[2] | ... | DOTS Signal Attribute[n] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The first two bytes define the Hop-by-Hop Option type number
allocated to the DOTS opportunistic signalling. This number is not
yet fixed but the first three bits MUST be set to 0. The first two
zero bits indicate that routers which cannot handle the DOTS signal
option will continue to process other options. The third 0 bit means
that the option processing will not change the packet's final
destination [RFC2460].
The second two bytes contain the length of the option content. The
content of the DOTS Signal option is a variable-length field that
contains one or more type-length-values (TLV) encoded DOTS signal
attributes, and has the following format:
0 7 15
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type | Attr Data Len | Attr Data ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Attr Type is 8-bit identifier of a DOTS signal attribute.
The Attr Data Len is 8-bit unsigned integer which is the length of
Attr Data in bytes.
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The Attr Data is variable-length field that contains the data of the
attribute.
2.2 DOTS signal Option attributes
The first attribute embedded into the opportunistic DOTS signal is a
TTL (Time-to-Live) field which indicates the maximum number of
retransmission of the signal into another IPv6 packets until it MUST
be discarded. Remaining attributes are similar to the header fields
described in [I-D.draft-reddy-dots-transport] (section 5.1.1) used to
convey a DOTS signal through a HTTP POST.
The sequence of attributes to be inserted within the header SHOULD
be TLV encoded, and they are defined in the following order:
TTL: Time-to-Live. This is a mandatory attribute.
host: the IP address of the DOTS server where the signal option
SHOULD be delivered.
port: the listening port of the DOTS server.
policy-id: defined in [I-D.draft-reddy-dots-transport].
target-ip: defined in [I-D.draft-reddy-dots-transport].
However, each address or prefix is encoded in its own TLV
element.
target-port: defined in [I-D.draft-reddy-dots-transport].
However, each target port is encoded in its own TLV element.
target-protocol: defined in [I-D.draft-reddy-dots-transport].
However each target protocol is encoded in its own TLV element.
The encoded attributes MUST be included in the option header in the
order defined above.
2.3 Example
Following is an example of an encoded Hop-by-Hop Option header to
signal that a web service is under attack.
0 7 15 22 31
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=7 | PadN Option=2 | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | DOTS Type=31 |Opt Data Len=80| Attr. type=TTL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Att Data Len=1 | 128 |Attr. type=host|Att Data Len=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.0.2.1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Attr. type=port|Att Data Len=2 | 443 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A. type=policy |Att Data Len=2 | 123321333242 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Attr. type= ip |Att Data Len=4 | 192.0.... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... 2.20 |Attr. type= ip |Att Data Len=16|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| 2001:db8:6401::1 ... |
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Attr. type=port|Att Data Len=2 | 8080 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Attr. type=port|Att Data Len=2 | 443 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Attr.type=proto|Att Data Len=2 | TCP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 Option Processing
3.2 Opportunistic DOTS signal initialization by a DOTS client
When a DOTS client needs to inform the DOTS server that it is under
attack, it firstly makes a connection attempt and applies the
mechanisms described in [I-D.draft-reddy-dots-transport].
In addition it actives an opportunistic mechanism to include the Hop-
by-Hop header option defined in this document in one or multiple IPv6
packets leaving the node.
The selection of packets has to be configured a priori. The
configuration is composed of a sequence of rules defined in a
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hierarchical order such that they are triggered in a sequential
manner.
Each rule is defined by:
o a set of filters over the IPv6 packet headers. Only packets
matching those filters are selected for opportunistic signalling.
For instance, only packets heading to a given subnetwork or to
specific address close to a DOTS server can be selected to
increase the chance to reach the latter.
o a ratio to select only a proportion of packets matching the
filters in order to limit the induced overhead of the
opportunistic signalling.
o a timeout until the rule is active and selected IPv6 packets
embed the DOTS opportunistic signal.
The objective is to apply each ordered rule after another according
to their timeouts. The first rule is triggered immediately after the
opportunistic signalling is activated.
Although the definition of rules MUST be configured by the user. It
is RECOMMENDED to order them inversely related to the number of
packet that would be selected. This can be approximated regarding the
definition of filters. The core idea is to benefit from the first
instants of the attack before losing connectivity by using a maximum
of outgoing packets. It is thus RECOMMENDED to define the first as
matching all IPv6 packets with a ratio equals one to rapidly
disseminate the information but with a short timeout to limit the
implied overhead.
Here is the an example of rules:
1: all outgoing IPv6 packets with a 10 second timeout
2: all outgoing IPv6 packets with a ratio of 10% and a 1 minute
timeout
3: all outgoing multicast IPv6 packets with a ratio of 10% and a 1
minute timeout
4: all outgoing anycast IPv6 packets with a ratio of 10% and a 5
minute timeout
5: all outgoing IPv6 packets heading to the DOTS server with a
ratio of 100% and a one hour timeout
3.2 Processing by a non DOTS opportunistic-capable router
When receiving an opportunistic DOTS signal encoded in a IPv6 packet,
a non DOT opportunistic capable router simply skips the Hop-by-Hop
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option and continue the normal processing of the IPv6 packet because
the option type MUST start with three zero bits.
3.3 Processing by a DOTS opportunistic-capable router
A DOTS opportunistic-capable router MUST store DOTS signalling
information whose it is aware of. If a router processes an IPv6 DOTS
opportunistic signal and supports this option, it first checks if it
has already stored the associated information. In that case, the
router simply skips the option and continues the normal processing
otherwise it stores the encoded information in order to embed it
again in other IPv6 packets similarly to the DOTS client. Hence, a
set of rules are also defined in advance and are triggered upon the
reception of a new opportunistic DOTS signal. Once all rule have been
applied, signalling information MUST be discarded by the router. When
embedding the information into other IPv6 packets, the router MUST
decrease the TTL by one since opportunistic signalling does not
prevent loops in the dissemination of signalling.
3.4 Processing by a DOTS opportunistic-capable relay
If a DOTS relay has DOTS capabilities, it will apply the same
strategy as a DOTS client by making attempts of direct connections to
the DOST server and in addition it inserts the Hop-by-Hop header DOTS
signalling option in leaving IPv6 packets using the strategy
specified above.
3.5 Processing by a DOTS opportunistic-capable server
When the IP layer of the host where the DOTS server is running
receives an IPv6 packet carrying a Hop-by-Hop DOTS signal option
header it MUST extracts the content of the option and provides the
attributes data to the server program.
4 Impact on existing IP layer implementations
For this option to be applicable within an IP system, it requires
modifications to existing IP layer implementation. At DOTS capable
nodes (client, relay and server), it requires a service interface
used by upper-layer protocols and application programs to ask the IP
layer to insert and listen to the Hop-by-Hop header option in IPv6
packets with the content and strategies described in Section 3. A
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DOTS client invokes the service interface to insert the option, A
DOTS relay invokes the service interface for listening and inserting
the option, and finally a DOTS server only invokes the service
interface to listen to the DOTS signalling option.
Intermediate nodes (routers or middle boxes) IP layer needs to be
extended to perform processing of the new Hop-by-Hop header option as
described in Section 3. They mainly parse the first host attribute of
the option and make a selection of a leaving IPv6 packet where the
option will be inserted.
Every node inserting the new proposed Hop-by-Hop option SHOULD only
select IPv6 packets with enough left space to avoid fragmentation.
5 Security Considerations
Any IPv6 header option could be used by an attacker to create an
attack on the routers and intermediate boxes that process packets
containing the option. The proposed IPv6 option in this document MAY
be abused by an attacker to create a covert channel at the IP layer
where data is hidden inside the content of the option [RFC6564].
However, this attack is not specific to the proposed option and it is
known issue of IPv6 header extensions and options.
The option may also be used by an attacker to forge or modify
opportunistic DOTS signal leading to trigger additional processing on
intermediate nodes and DOTS servers. Besides, an attacker can also
listen opportunistic DOTS signals to monitor the impact of its own
attack. These considerations are not specific to the proposed option.
The DOTS agent MAY use techniques to enforce confidentiality,
authenticity and integrity over the opportunistic DOTS signal
channel.
6 IANA Considerations
This draft defines a new IPv6 [RFC2460] hop-by-hop option. This
requires an IANA RFC3692-style update of:
http://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml
and ultimately the assignment of a new hop-by-hop option according to
the guidelines described in [RFC5237].
7 References
7.1 Normative References
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7.2 Informative References
[I-D.draft-ietf-dots-requirements]
A. Mortensen., R. Moskowitz., and T. Reddy., "DDoS Open Threat
Signaling Requirements", draft-ietf-dots-requirements-00 (work in
progress), October 2015.
[kuhrer2014exit]
Kuhrer, Marc and Hupperich, Thomas and Rossow, Christian and Holz,
Thorsten. Exit from Hell? Reducing the Impact of Amplification
DDoS Attacks. In: 23rd USENIX Security Symposium (USENIX Security
14).
[I-D.draft-reddy-dots-transport]
T. Reddy., D. Wing., P. Patil., M. Geller., M. Boucadair.,and R.
Moskowitz., "Co-operative DDoS Mitigation", draft-reddy-dots-
transport-03 (work in progress), March 2016.
[rootops-ddos]
rootops.: Events of 2015-11-30. Online: http://root-
servers.org/news/events-of-20151130.txt
[ripe-dnsmon-ddos]
RIPE NCC DNS Monitoring Service (DNSMON). Online:
https://atlas.ripe.net/dnsmon/
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Acknowledgements
This work is partly funded by FLAMINGO, a Network of Excellence
project (ICT-318488) supported by the European Commission under
its Seventh Framework Programme.
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Authors' Addresses
Jerome Francois
Inria
615 rue du Jardin Botanique
54600 Villers-les-Nancy
France
Phone: +33 3 83 59 30 66
EMail: jerome.francois@inria.fr
Abdelkader Lahmadi
University of Lorraine - LORIA
615 rue du Jardin Botanique
54600 Villers-les-Nancy
France
Phone: +33 3 83 59 30 00
Email: Abdelkader.Lahmadi@loria.fr
Giovane C. M. Moura
SIDN Labs
6825 MD Meander 501
Arnhem, the Netherlands
Marco Davids
SIDN Labs
6825 MD Meander 501
Arnhem, the Netherlands
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