DOTS T. Reddy
Internet-Draft D. Wing
Intended status: Standards Track P. Patil
Expires: April 20, 2016 M. Geller
Cisco
M. Boucadair
France Telecom
R. Moskowitz
HTT Consulting
October 18, 2015
Co-operative DDoS Mitigation
draft-reddy-dots-transport-01
Abstract
This document discusses mechanisms that a DOTS client can use, when
it detects a potential Distributed Denial-of-Service (DDoS) attack,
to signal that the DOTS client is under an attack or request an
upstream DOTS server to perform inbound filtering in its ingress
routers for traffic that the DOTS client wishes to drop. The DOTS
server can then undertake appropriate actions (including, blackhole,
drop, rate-limit, or add to watch list) on the suspect traffic to the
DOTS client, thus reducing the effectiveness of the attack.
Status of This Memo
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Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 3
4. Protocol for Signal Channel: HTTP REST . . . . . . . . . . . 4
4.1. SOS . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.1. Signal SOS . . . . . . . . . . . . . . . . . . . . . 5
4.1.2. Recall SOS . . . . . . . . . . . . . . . . . . . . . 6
4.1.3. Retrieving SOS . . . . . . . . . . . . . . . . . . . 6
4.2. REST . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2.1. Filtering Rules . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. BGP . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
A distributed denial-of-service (DDoS) attack is an attempt to make
machines or network resources unavailable to their intended users.
In most cases, sufficient scale can be achieved by compromising
enough end-hosts and using those infected hosts to perpetrate and
amplify the attack. The victim in this attack can be an application
server, a client, a router, a firewall, or an entire network, etc.
The reader may refer, for example, to [REPORT] that reports the
following:
o Very large DDoS attacks above the 100 Gbps threshold are
experienced.
o DDoS attacks against customers remain the number one operational
threat for service providers, with DDoS attacks against
infrastructures being the top concern for 2014.
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o Over 60% of service providers are seeing increased demand for DDoS
detection and mitigation services from their customers (2014),
with just over one-third seeing the same demand as in 2013.
In a lot of cases, it may not be possible for an enterprise to
determine the cause for an attack, but instead just realize that
certian resources seem to be under attack. The document proposes
that, in such cases, the DOTS client just inform the DOTS server that
the enterprise is under a potential attack and that the DOTS server
monitor traffic to the enterprise to mitigate any possible attack.
This document also describes a means for an enterprise, which act as
DOTS clients, to dynamically inform its DOTS server of the IP
addresses or prefixes that are causing DDoS. A DOTS server can use
this information to discard flows from such IP addresses reaching the
customer network.
The proposed mechanism can also be used between applications from
various vendors that are deployed within the same network, some of
them are responsible for monitoring and detecting attacks while
others are responsible for enforcing policies on appropriate network
elements. This cooperations contributes to a ensure a highly
automated network that is also robust, reliable and secure. The
advantage of the proposed mechanism is that the DOTS server can
provide protection to the DOTS client from bandwidth-saturating DDoS
traffic.
How a DOTS server determines which network elements should be
modified to install appropriate filtering rules is out of scope. A
variety of mechanisms and protocols (including NETCONF) may be
considered to exchange information through a communication interface
between the server and these underlying elements; the selection of
appropriate mechanisms and protocols to be invoked for that
interfaces is deployment-specific.
Terminology and protocol requirements for co-operative DDoS
mitigation are obtained from [I-D.mortensen-dots-requirements].
2. Notational Conventions
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].
3. Solution Overview
Network applications have finite resources like CPU cycles, number of
processes or threads they can create and use, maximum number of
simultaneous connections it can handle, limited resources of the
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control plane, etc. When processing network traffic, such an
application uses these resources to offer its intended task in the
most efficient fashion. However, an attacker may be able to prevent
the application from performing its intended task by causing the
application to exhaust the finite supply of a specific resource.
TCP DDoS SYN-flood is a memory-exhaustion attack on the victim and
ACK-flood is a CPU exhaustion attack on the victim. Attacks on the
link are carried out by sending enough traffic such that the link
becomes excessively congested, and legitimate traffic suffers high
packet loss. Stateful firewalls can also be attacked by sending
traffic that causes the firewall to hold excessive state and the
firewall runs out of memory, and can no longer instantiate the state
required to pass legitimate flows. Other possible DDoS attacks are
discussed in [RFC4732].
In each of the cases described above, if a network resource detects a
potential DDoS attack from a set of IP addresses, the network
resource (DOTS client) informs its servicing router (DOTS relay) of
all suspect IP addresses that need to be blocked or black-listed for
further investigation. DOTS client could also specify protocols and
ports in the black-list rule. That DOTS relay in-turn propagates the
black-listed IP addresses to the DOTS server and the DOTS server
blocks traffic from these IP addresses to the DOTS client thus
reducing the effectiveness of the attack. The DOTS client
periodically queries the DOTS server to check the counters mitigating
the attack. If the DOTS client receives response that the counters
have not incremented then it can instruct the black-list rules to be
removed. If a blacklisted IPv4 address is shared by multiple
subscribers then the side effect of applying the black-list rule will
be that traffic from non-attackers will also be blocked by the access
network.
If a DOTS client cannot determine the IP address(s) that are causing
the attack, but is under an attack nonetheless, the DOTS client can
just notifiy the DOTS server that it is under a potential attack and
request that the DOTS server take precautionary measures to mitigate
the attack.
4. Protocol for Signal Channel: HTTP REST
A DOTS client can use RESTful APIs discussed in this section to
signal/inform a DOTS server of an attack or any desired IP filtering
rules.
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4.1. SOS
The following APIs define the means to signal an SOS from a DOTS
client to a DOTS server.
TBD: SOS messages SHOULD be exchanged over DTLS over UDP.
4.1.1. Signal SOS
An HTTP POST request will be used to signal SOS to the DOTS server.
POST {scheme}://{host}:{port}/.well-known/{version}/{URI suffix for SOS}
Accept: application/json
Content-type: application/json
{
"policy-id": number,
"target-ip": string,
"target-port": string,
"target-protocol": string,
}
Figure 1: POST to signal SOS
The header fields are described below.
policy-id: Identifier of the policy represented using a number.
This identifier must be unique for each policy bound to the DOTS
client. This identifier must be generated by the client and used
as an opaque value by the server. This document does not make any
assumption about how this identifier is generated.
target-ip: A list of addresses or prefixes under attack. This is an
optional attribute.
target-port: A list of ports under attack. This is an optional
attribute.
target-protocol: A list of protocols under attack. Valid protocol
values include tcp, udp, sctp and dccp. This is an optional
attribute.
Note: administrative-related clauses may be included as part of the
request (such a contract Identifier or a customer identifier). Those
clauses are out of scope of this document.
To avoid SOS message fragmentation and the consequently decreased
probability of message delivery, DOTS agents MUST ensure that the
DTLS record MUST fit within a single datagram. DOTS agents can
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exploit the fact that the IP specification [RFC0791] specifies that
IP packets up to 576 bytes should never need to be fragmented, thus
sending a maximum of 500 bytes of SOS message over a UDP datagram
will generally avoid IP fragmentation.
The following example shows POST request to signal that a Web-Service
is under attack.
POST https://www.example.com/.well-known/v1/SOS
Accept: application/json
Content-type: application/json
{
"policy-id": 123321333242,
"target-ip": "2002:db8:6401::1",
"target-port": "443",
"target-protocol": "tcp",
}
Figure 2: POST to signal SOS
4.1.2. Recall SOS
An HTTP DELETE request will be used to delete an SOS signaled to the
DOTS server.
DELETE {scheme}://{host}:{port}/.well-known/{URI suffix for SOS}
Accept: application/json
Content-type: application/json
{
"policy-id": number
}
Figure 3: Recall SOS
4.1.3. Retrieving SOS
An HTTP GET request will be used to retrieve an SOS signaled to the
DOTS server.
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1) To retrieve all SOS signaled by the DOTS client.
GET {scheme}://{host}:{port}/.well-known/{URI suffix for SOS}
2) To retrieve a specific SOS signaled by the DOTS client.
GET {scheme}://{host}:{port}/.well-known/{URI suffix for SOS}
Accept: application/json
Content-type: application/json
{
"policy-id": number
}
Figure 4: GET to retrieve the rules
4.2. REST
A DOTS client could use HTTP to provision and manage filters on the
DOTS server. The DOTS client authenticates itself to the DOTS relay,
which in turn authenticates itself to a DOTS server, creating a two-
link chain of transitive authentication between the DOTS client and
the DOTS server. The DOTS relay validates if the DOTS client is
authorized to signal the black-list rules. Likewise, the DOTS server
validates if the DOTS relay is authorized to signal the black-list
rules. To create or purge filters, the DOTS client sends HTTP
requests to the DOTS relay. The DOTS relay acts as an HTTP proxy,
validates the rules and proxies the HTTP requests containing the
black-listed IP addresses to the DOTS server. When the DOTS relay
receives the associated HTTP response from the HTTP server, it
propagates the response back to the DOTS client.
If an attack is detected by the DOTS relay then it can act as a HTTP
client and signal the black-list rules to the DOTS server. Thus the
DOTS relay plays the role of both HTTP client and HTTP proxy.
Network
Resource CPE router Access network
(DOTS client) (DOTS relay) (DOTS server) __________
+-----------+ +----------+ +-------------+ / \
| |____| |_______| |___ | Internet |
|HTTP Client| |HTTP Proxy| | HTTP Server | | |
| | | | | | | |
+-----------+ +----------+ +-------------+ \__________/
Figure 5
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JSON [RFC7159] payloads can be used to convey both filtering rules as
well as protocol-specific payload messages that convey request
parameters and response information such as errors.
The figure above explains the protocol with a DOTS relay. The
protocol is equally applicable to scenarios where a DOTS client
directly talks to the DOTS server.
4.2.1. Filtering Rules
The following APIs define means for a DOTS client to configure
filtering rules on a DOTS server.
4.2.1.1. Install filtering rules
An HTTP POST request will be used to push filtering rules to the DOTS
server.
POST {scheme}://{host}:{port}/.well-known/{version}/{URI suffix for filtering}
Accept: application/json
Content-type: application/json
{
"policy-id": number,
"traffic-protocol": string,
"source-protocol-port": string,
"destination-protocol-port": string,
"destination-ip": string,
"source-ip": string,
"lifetime": number,
"traffic-rate" : number,
}
Figure 6: POST to install filtering rules
The header fields are described below.
policy-id: Identifier of the policy represented using a number.
This identifier must be unique for each policy bound to the same
downstream network. This identifier must be generated by the
client and used as an opaque value by the server. This document
does not make any assumption about how this identifier is
generated.
traffic-protocol: Valid protocol values include tcp and udp.
source-protocol-port: For TCP or UDP or SCTP or DCCP: the source
range of ports (e.g., 1024-65535).
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destination-protocol-port: For TCP or UDP or SCTP or DCCP: the
destination range of ports (e.g., 443-443). This information is
useful to avoid disturbing a group of customers when address
sharing is in use [RFC6269].
destination-ip: The destination IP addresses or prefixes.
source-ip: The source IP addresses or prefixes.
lifetime: Lifetime of the policy in seconds. Indicates the
validity of a rule. Upon the expiry of this lifetime, and if the
request is not reiterated, the rule will be withdrawn at the
upstream network. A null value is not allowed.
traffic-rate: This field carries the rate information in IEEE
floating point [IEEE.754.1985] format, units being bytes per
second. A traffic-rate of '0' should result on all traffic for
the particular flow to be discarded.
The relative order of two rules is determined by comparing their
respective policy identifiers. The rule with lower numeric policy
identifier value has higher precedence (and thus will match before)
than the rule with higher numeric policy identifier value.
Note: administrative-related clauses may be included as part of the
request (such a contract Identifier or a customer identifier). Those
clauses are out of scope of this document.
The following example shows POST request to block traffic from
attacker IPv6 prefix 2001:db8:abcd:3f01::/64 to network resource
using IPv6 address 2002:db8:6401::1 to provide HTTPS web service.
POST https://www.example.com/.well-known/v1/filter
Accept: application/json
Content-type: application/json
{
"policy-id": 123321333242,
"traffic-protocol": "tcp",
"source-protocol-port": "1-65535",
"destination-protocol-port": "443",
"destination-ip": "2001:db8:abcd:3f01::/64",
"source-ip": "2002:db8:6401::1",
"lifetime": 1800,
"traffic-rate": 0,
}
Figure 7: POST to install black-list rules
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4.2.1.2. Remove filtering rules
An HTTP DELETE request will be used to delete filtering rules
programmed on the DOTS server.
DELETE {scheme}://{host}:{port}/.well-known/{URI suffix for filtering}
Accept: application/json
Content-type: application/json
{
"policy-id": number
}
Figure 8: DELETE to remove the rules
4.2.1.3. Retrieving installed filtering rules
An HTTP GET request will be used to retrieve filtering rules
programmed on the DOTS server.
1) To retrieve all the black-lists rules programmed by the DOTS client.
GET {scheme}://{host}:{port}/.well-known/{URI suffix for filtering}
2) To retrieve specific black-list rules programmed by the DOTS-cient.
GET {scheme}://{host}:{port}/.well-known/{URI suffix for filtering}
Accept: application/json
Content-type: application/json
{
"policy-id": number
}
Figure 9: GET to retrieve the rules
5. IANA Considerations
TODO
6. Security Considerations
TODO
HTTPS MUST be used for data confidentiality and (D)TLS based on
client certificate MUST be used for mutual authentication. The
interaction between the DOTS agents requires Datagram Transport Layer
Security (DTLS) and Transport Layer Security (TLS) with a ciphersuite
offering confidentiality protection and the guidance given in
[RFC7525] must be followed to avoid attacks on (D)TLS.
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Special care should be taken in order to ensure that the activation
of the proposed mechanism won't have an impact on the stability of
the network (including connectivity and services delivered over that
network).
Involved functional elements in the cooperation system must establish
exchange instructions and notification over a secure and
authenticated channel. Adequate filters can be enforced to avoid
that nodes outside a trusted domain can inject request such as
deleting filtering rules. Nevertheless, attacks can be initiated
from within the trusted domain if an entity has been corrupted.
Adequate means to monitor trusted nodes should also be enabled.
7. Acknowledgements
Thanks to C. Jacquenet for the discussion and comments.
8. References
8.1. 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>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.
8.2. Informative References
[REPORT] "Worldwide Infrastructure Security Report", 2014,
<http://pages.arbornetworks.com/rs/arbor/images/
WISR2014.pdf>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006,
<http://www.rfc-editor.org/info/rfc4732>.
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[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
and D. McPherson, "Dissemination of Flow Specification
Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
<http://www.rfc-editor.org/info/rfc5575>.
[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
P. Roberts, "Issues with IP Address Sharing", RFC 6269,
DOI 10.17487/RFC6269, June 2011,
<http://www.rfc-editor.org/info/rfc6269>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>.
Appendix A. BGP
BGP defines a mechanism as described in [RFC5575] that can be used to
automate inter-domain coordination of traffic filtering, such as what
is required in order to mitigate DDoS attacks. However, support for
BGP in an access network does not guarantee that traffic filtering
will always be honored. Since a DOTS client will not receive an
acknowledgment for the filtering request, the DOTS client should
monitor and apply similar rules in its own network in cases where the
DOTS server is unable to enforce the filtering rules. In addition,
enforcement of filtering rules of BGP on Internet routers are usually
governed by the maximum number of data elements the routers can hold
as well as the number of events they are able to process in a given
unit of time.
Authors' Addresses
Tirumaleswar Reddy
Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli
Sarjapur Marathalli Outer Ring Road
Bangalore, Karnataka 560103
India
Email: tireddy@cisco.com
Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
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Prashanth Patil
Cisco Systems, Inc.
Email: praspati@cisco.com
Mike Geller
Cisco Systems, Inc.
3250
Florida 33309
USA
Email: mgeller@cisco.com
Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Robert Moskowitz
HTT Consulting
Oak Park, MI 42837
United States
Email: rgm@htt-consult.com
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