| DOTS | K. Nishizuka |
| Internet-Draft | NTT Communications |
| Intended status: Standards Track | M. Boucadair |
| Expires: December 17, 2020 | Orange |
| T. Reddy | |
| McAfee | |
| T. Nagata | |
| Lepidum | |
| June 15, 2020 |
Controlling Filtering Rules Using Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel
draft-ietf-dots-signal-filter-control-05
This document specifies an extension to the Distributed Denial-of-Service Open Threat Signaling (DOTS) signal channel protocol so that DOTS clients can control their filtering rules when an attack mitigation is active.
Particularly, this extension allows a DOTS client to activate or de-activate existing filtering rules during a DDoS attack. The characterization of these filtering rules is supposed to be conveyed by a DOTS client during an idle time by means of the DOTS data channel protocol.
Please update these statements within the document with the RFC number to be assigned to this document:
Please update the "revision" date of the YANG module.
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 December 17, 2020.
Copyright (c) 2020 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 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
The Distributed Denial-of-Service Open Threat Signaling (DOTS) data channel protocol [RFC8783] is used for bulk data exchange between DOTS agents to improve the coordination of parties involved in the response to a Distributed Denial-of-Service (DDoS) attack. Filter management is one of its tasks which enables a DOTS client to retrieve the filtering capabilities of a DOTS server and to manage filtering rules. Typically, these Filtering rules are used for dropping or rate-limiting unwanted traffic, and permitting accept-listed traffic.
Unlike the DOTS signal channel protocol [RFC8782], the DOTS data channel protocol is not expected to deal with attack conditions. As such, an issue that might be encountered in some deployments is when filters installed by means of the DOTS data channel protocol may not function as expected during DDoS attacks or, worse, exacerbate an ongoing DDoS attack. The DOTS data channel protocol cannot be used then to change these filters, which may complicate DDoS mitigation operations [Interop].
A typical case is a DOTS client which configures during 'idle' time (i.e., no mitigation is active) some filtering rules using the DOTS data channel protocol to permit traffic from accept-listed sources, but during a volumetric DDoS attack the DDoS mitigator identifies the source addresses/prefixes in the accept-listed filtering rules are attacking the target. For example, an attacker can spoof the IP addresses of accept-listed sources to generate attack traffic or the attacker can compromise the accept-listed sources and program them to launch a DDoS attack.
[RFC8782] is designed so that the DDoS server notifies the conflict to the DOTS client (that is, 'conflict-cause' parameter set to 2 (Conflicts with an existing accept list)), but the DOTS client may not be able to withdraw the accept-list rules during the attack period due to the high-volume attack traffic saturating the inbound link to the DOTS client domain. In other words, the DOTS client cannot use the DOTS data channel protocol to withdraw the accept-list filters when a DDoS attack is in progress.
This specification addresses the problems discussed in Section 1.1 by adding a capability for managing filtering rules using the DOTS signal channel protocol, which enables a DOTS client to request the activation (or deactivation) of filtering rules during a DDoS attack. Note that creating these filtering rules is still the responsibility of the DOTS data channel [RFC8783].
The DOTS signal channel protocol is designed to enable a DOTS client to contact a DOTS server for help even under severe network congestion conditions. Therefore, extending the DOTS signal channel protocol to manage the filtering rules during an attack will enhance the protection capability offered by DOTS protocols.
Conflicts that are induced by filters installed by other DOTS clients of the same domain are not discussed in this specification.
An augment to the DOTS signal channel YANG module is defined in Section 3.2.2.
Sample examples are provided in Section 4, in particular:
The JavaScript Object Notation (JSON) encoding of YANG-modeled data [RFC7951] is used to illustrate the examples.
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.
The reader should be familiar with the terms defined in [RFC8612].
The terminology for describing YANG modules is defined in [RFC7950]. The meaning of the symbols in the tree diagram is defined in [RFC8340].
The filtering rules eventually managed using the DOTS signal channel protocol are created a priori by the same DOTS client using the DOTS data channel protocol. Managing conflicts with filters installed by other DOTS clients of the same domain is out of scope.
As discussed in Section 4.4.1 of [RFC8782], a DOTS client must use the same 'cuid' for both the DOTS signal and data channels. This requirement is meant to facilitate binding DOTS channels used by the same DOTS client.
The DOTS signal and data channels from a DOTS client may or may not use the same DOTS server. Nevertheless, the scope of the mitigation request, alias, and filtering rules are not restricted to the DOTS server but to the DOTS server domain. To that aim, DOTS servers within a domain are assumed to have a mechanism to coordinate the mitigation requests, aliases, and filtering rules to coordinate their decisions for better mitigation operation efficiency. The exact details about such mechanism is out of the scope of this document.
A filtering rule controlled by the DOTS signal channel is identified by its ACL name (Section 4.3 of [RFC8782]). Note that an ACL name unambiguously identifies an ACL bound to a DOTS client, but the same name may be used by distinct DOTS clients.
The activation or deactivation of an ACL by the DOTS signal channel overrides the 'activation-type' (defined in Section 4.3 of [RFC8783]) a priori conveyed with the filtering rules using the DOTS data channel protocol.
Once the attack is mitigated, the DOTS client may use the data channel to control the 'activation-type' (e.g., revert to a default value) of some of the filtering rules controlled by the DOTS signal channel or delete some of these filters. This behavior is deployment specific.
This specification extends the mitigation request defined in Section 4.4.1 of [RFC8782] to convey the intended control of configured filtering rules. Concretely, the DOTS client conveys 'acl-list' attribute with the following sub-attributes in the CBOR body of a mitigation request (see the YANG structure in Section 3.2.2.1):
The JSON/YANG mappings for DOTS filter control attributes are shown in Table 1.
+-------------------+------------+--------+---------------+--------+ | Parameter Name | YANG | CBOR | CBOR Major | JSON | | | Type | Key | Type & | Type | | | | | Information | | +===================+============+========+===============+========+ |ietf-dots-signal- | | | | | |control:activation-| | | | | | type | enumeration| TBA1 | 0 unsigned | String | | | | | | | |ietf-dots-signal- | | | | | | control:acl-list | list | TBA2 | 4 array | Array | | | | | | | |ietf-dots-signal- | | | | | | control:acl-name | leafref | TBA3 | 3 text string | String | +-------------------+------------+--------+---------------+--------+ Table 1: JSON/YANG Mapping to CBOR for Filter Control Attributes
By default, ACL-related operations are achieved using the DOTS data channel protocol when no attack is ongoing. DOTS clients MUST NOT use the filtering control over DOTS signal channel in 'idle' time; such requests MUST be discarded by DOTS servers with 4.00 (Bad Request).
During an attack time, DOTS clients may include 'acl-list', 'acl-name', and 'activation-type' attributes in a mitigation request. This request may be the initial mitigation request for a given mitigation scope or a new one overriding an existing request. In both cases, a new 'mid' MUST be used. Nevertheless, it is NOT RECOMMENDED to include ACL attributes in an initial mitigation request for a given mitigation scope or in a mitigation request adjusting the mitigation scope. This recommendation is meant to avoid delaying attack mitigations because of failures to process ACL attributes.
As the attack evolves, DOTS clients can adjust the 'activation-type' of an ACL conveyed in a mitigation request or control other filters as necessary. This can be achieved by sending a PUT request with a new 'mid' value.
It is RECOMMENDED for a DOTS client to subscribe to asynchronous notifications of the attack mitigation, as detailed in Section 4.4.2.1 of [RFC8782]. If not, the polling mechanism in Section 4.4.2.2 of [RFC8782] has to be followed by the DOTS client.
A DOTS client relies on the information received from the DOTS server and/or local information to the DOTS client domain to trigger a filter control request. Only filters that are pertinent for an ongoing mitigation should be controlled by a DOTS client using the DOTS signal channel.
'acl-list', 'acl-name', and 'activation-type' are defined as comprehension-required parameters (Section 5.1). Following the rules in Section 6 of [RFC8782], if the DOTS server does not understand the 'acl-list' or 'acl-name' or 'activation-type' attributes, it responds with a "4.00 (Bad Request)" error response code.
If the DOTS server does not find the ACL name ('acl-name') conveyed in the mitigation request for this DOTS client, it MUST respond with 4.04 (Not Found) error response code.
If the DOTS server finds the ACL name for this DOTS client, and assuming the request passed the validation checks in Section 4.4.1 of [RFC8782], the DOTS server MUST proceed with the 'activation-type' update. The update is immediately enforced by the DOTS server and will be maintained as the new activation type for the ACL name even after the termination of the mitigation request. In addition, the DOTS server MUST update the lifetime of the corresponding ACL similar to the update when a refresh request is received using the DOTS data channel (Section 7.2 of [RFC8783]). If, for some reason, the DOTS server fails to apply the filter update, it MUST respond with 5.03 (Service Unavailable) error response code and include the failed ACL update in the diagnostic payload of the response (an example is shown in Figure 1). Else, the DOTS server replies with the appropriate response code defined in Section 4.4.1 of [RFC8782].
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"mid": 123,
"ietf-dots-signal-control:acl-list": [
{
"ietf-dots-signal-control:acl-name": "an-accept-list",
"ietf-dots-signal-control:activation-type": "deactivate"
}
]
}
]
}
}
Figure 1: Example of a Diagnostic Payload Including Failed ACL Update
If the DOTS client receives a 5.03 (Service Unavailable) with a diagnostic payload indicating a failed ACL update as a response to an initial mitigation or a mitigation with adjusted scope, the DOTS client MUST immediately send a new request which repeats all the parameters as sent in the failed mitigation request but without including the ACL attributes. After the expiry of Max-Age returned in the 5.03 (Service Unavailable) response, the DOTS client retries with a new mitigation request (i.e., a new 'mid') that repeats all the parameters as sent in the failed mitigation request (i.e., the one including the ACL attributes).
If, during an active mitigation, the 'activation-type' is changed at the DOTS server (e.g., as a result of an external action) for an ACL bound to a DOTS client, the DOTS server notifies that DOTS client with the change by including the corresponding ACL parameters in an asynchronous notification (the DOTS client is observing the active mitigation) or in a response to a polling request (Section 4.4.2.2 of [RFC8782]).
If the DOTS signal and data channels of a DOTS client are not established with the same DOTS server of a DOTS server domain, the above request processing operations are undertaken using the coordination mechanism discussed in Section 3.1.
This specification does not require any modification to the efficacy update and the withdrawal procedures defined in [RFC8782]. In particular, ACL-related clauses are not included in a PUT request used to send an efficacy update and DELETE requests.
This document augments the "ietf-dots-signal-channel" YANG module defined in [RFC8782] for managing filtering rules.
module: ietf-dots-signal-control
augment /ietf-signal:dots-signal/ietf-signal:message-type
/ietf-signal:mitigation-scope/ietf-signal:scope:
+--rw acl-list* [acl-name] {control-filtering}?
+--rw acl-name
| -> /ietf-data:dots-data/dots-client/acls/acl/name
+--rw activation-type? ietf-data:activation-type
This document defines the YANG module "ietf-dots-signal-control", which has the following tree structure:
This YANG module is not intended to be used via NETCONF/RESTCONF for DOTS server management purposes; such module is out of the scope of this document. It serves only to provide a data model and encoding, but not a management data model.
This module uses types defined in [RFC8783].
<CODE BEGINS> file "ietf-dots-signal-control@2019-05-13.yang"
module ietf-dots-signal-control {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-dots-signal-control";
prefix dots-control;
import ietf-dots-signal-channel {
prefix ietf-signal;
reference
"RFC 8782: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel Specification";
}
import ietf-dots-data-channel {
prefix ietf-data;
reference
"RFC 8783: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Data Channel Specification";
}
organization
"IETF DDoS Open Threat Signaling (DOTS) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/dots/>
WG List: <mailto:dots@ietf.org>
Author: Kaname Nishizuka
<mailto:kaname@nttv6.jp>
Author: Mohamed Boucadair
<mailto:mohamed.boucadair@orange.com>
Author: Konda, Tirumaleswar Reddy
<mailto:TirumaleswarReddy_Konda@McAfee.com>
Author: Takahiko Nagata
<mailto:nagata@lepidum.co.jp>";
description
"This module contains YANG definition for the signaling
messages exchanged between a DOTS client and a DOTS server
to control, by means of the DOTS signal channel, filtering
rules configured using the DOTS data channel.
Copyright (c) 2020 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
revision 2019-05-13 {
description
"Initial revision.";
reference
"RFC XXXX: Controlling Filtering Rules Using Distributed
Denial-of-Service Open Threat Signaling (DOTS)
Signal Channel";
}
feature control-filtering {
description
"This feature means that the DOTS signal channel is able
to manage the filtering rules created by the same DOTS
client using the DOTS data channel.";
}
augment "/ietf-signal:dots-signal/ietf-signal:message-type"
+ "/ietf-signal:mitigation-scope/ietf-signal:scope" {
if-feature control-filtering;
description "ACL name and activation type.";
list acl-list {
key "acl-name";
description
"List of ACLs as defined using the DOTS data
channel. ACLs bound to a DOTS client are uniquely
identified by a name.";
leaf acl-name {
type leafref {
path "/ietf-data:dots-data/ietf-data:dots-client"
+ "/ietf-data:acls/ietf-data:acl/ietf-data:name";
}
description
"Reference to the ACL name bound to a DOTS client.";
}
leaf activation-type {
type ietf-data:activation-type;
default "activate-when-mitigating";
description
"Sets the activation type of an ACL.";
}
}
}
}
<CODE ENDS>
This section provides some examples to illustrate the behavior specified in Section 3.2.1. These examples are provided for illustration purposes; they should not be considered as deployment recommendations.
Let's consider a DOTS client which contacts its DOTS server during 'idle' time to install an accept-list allowing for UDP traffic issued from 2001:db8:1234::/48 with a destination port number 443 to be forwarded to 2001:db8:6401::2/127. It does so by sending, for example, a PUT request shown in Figure 2.
PUT /restconf/data/ietf-dots-data-channel:dots-data\
/dots-client=paL8p4Zqo4SLv64TLPXrxA/acls\
/acl=an-accept-list HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
{
"ietf-dots-data-channel:acls": {
"acl": [
{
"name": "an-accept-list",
"type": "ipv6-acl-type",
"activation-type": "activate-when-mitigating",
"aces": {
"ace": [
{
"name": "test-ace-ipv6-udp",
"matches": {
"ipv6": {
"destination-ipv6-network": "2001:db8:6401::2/127",
"source-ipv6-network": "2001:db8:1234::/48"
},
"udp": {
"destination-port-range-or-operator": {
"operator": "eq",
"port": 443
}
}
},
"actions": {
"forwarding": "accept"
}
}
]
}
}
]
}
}
Figure 2: DOTS Data Channel Request to Create a Filter
Some time later, consider that a DDoS attack is detected by the DOTS client on 2001:db8:6401::2/127. Consequently, the DOTS client sends a mitigation request to its DOTS server as shown in Figure 3.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=paL8p4Zqo4SLv64TLPXrxA"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:6401::2/127"
],
"target-protocol": [
17
],
"lifetime": 3600
}
]
}
}
Figure 3: DOTS Signal Channel Mitigation Request
The DOTS server accepts immediately the request by replying with 2.01 (Created) (Figure 4 depicts the message body of the response).
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"mid": 123,
"lifetime": 3600
}
]
}
}
Figure 4: Status Response (Message Body)
Assuming the DOTS client subscribed to asynchronous notifications, when the DOTS server concludes that some of the attack sources belong to 2001:db8:1234::/48, it sends a notification message with 'status' code set to '1 (Attack mitigation is in progress)' and 'conflict-cause' set to '2' (conflict-with-acceptlist) to the DOTS client to indicate that this mitigation request is in progress, but a conflict is detected.
Upon receipt of the notification message from the DOTS server, the DOTS client sends a PUT request to deactivate the "an-accept-list" ACL as shown in Figure 5.
The DOTS client can also decide to send a PUT request to deactivate the "an-accept-list" ACL, if suspect traffic is received from an accept-listed source (2001:db8:1234::/48). The structure of that PUT is the same as the one shown in Figure 5.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=paL8p4Zqo4SLv64TLPXrxA"
Uri-Path: "mid=124"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:6401::2/127"
],
"target-protocol": [
17
],
"ietf-dots-signal-control:acl-list": [
{
"ietf-dots-signal-control:acl-name": "an-accept-list",
"ietf-dots-signal-control:activation-type": "deactivate"
}
],
"lifetime": 3600
}
]
}
}
Figure 5: PUT for Deactivating a Conflicting Filter
Then, the DOTS server deactivates "an-accept-list" ACL and replies with 2.04 (Changed) response to the DOTS client to confirm the successful operation. The message body is similar to the one depicted in Figure 4.
Once the attack is mitigated, the DOTS client may use the data channel to retrieve its ACLs maintained by the DOTS server. As shown in Figure 6, the activation type is set to 'deactivate' as set by the DOTS signal channel (Figure 5) instead of the type initially set using the DOTS data channel (Figure 2).
{
"ietf-dots-data-channel:acls": {
"acl": [
{
"name": "an-accept-list",
"type": "ipv6-acl-type",
"activation-type": "deactivate",
"pending-lifetime": 10021,
"aces": {
"ace": [
{
"name": "test-ace-ipv6-udp",
"matches": {
"ipv6": {
"destination-ipv6-network": "2001:db8:6401::2/127",
"source-ipv6-network": "2001:db8:1234::/48"
},
"udp": {
"destination-port-range-or-operator": {
"operator": "eq",
"port": 443
}
}
},
"actions": {
"forwarding": "accept"
}
}
]
}
}
]
}
}
Figure 6: DOTS Data Channel GET Response after Mitigation (Message Body)
Let's consider a DOTS client which contacts its DOTS server during 'idle' time to install an accept-list allowing for UDP traffic issued from 2001:db8:1234::/48 to be forwarded to 2001:db8:6401::2/127. It does so by sending, for example, a PUT request shown in Figure 7. The DOTS server installs this filter with a "deactivated" state.
PUT /restconf/data/ietf-dots-data-channel:dots-data\
/dots-client=ioiuLoZqo4SLv64TLPXrxA/acls\
/acl=my-accept-list HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
{
"ietf-dots-data-channel:acls": {
"acl": [
{
"name": "my-accept-list",
"type": "ipv6-acl-type",
"activation-type": "deactivate",
"aces": {
"ace": [
{
"name": "an-ace",
"matches": {
"ipv6": {
"destination-ipv6-network": "2001:db8:6401::2/127",
"source-ipv6-network": "2001:db8:1234::/48",
"protocol": 17
}
},
"actions": {
"forwarding": "accept"
}
}
]
}
}
]
}
}
Figure 7: DOTS Data Channel Request to Create an Accept-List Filter
Sometime later, consider that a UDP DDoS attack is detected by the DOTS client on 2001:db8:6401::2/127 but the DOTS client wants to let the traffic from 2001:db8:1234::/48 to be accept-listed to the DOTS client domain. Consequently, the DOTS client sends a mitigation request to its DOTS server as shown in Figure 8.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=ioiuLoZqo4SLv64TLPXrxA"
Uri-Path: "mid=4879"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:6401::2/127"
],
"target-protocol": [
17
],
"ietf-dots-signal-control:acl-list": [
{
"ietf-dots-signal-control:acl-name": "my-accept-list",
"ietf-dots-signal-control:activation-type": "immediate"
}
],
"lifetime": 3600
}
]
}
}
Figure 8: DOTS Signal Channel Mitigation Request with a Filter Control
The DOTS server activates "my-accept-list" ACL and replies with 2.01 (Created) response to the DOTS client to confirm the successful operation.
This section describes a scenario in which a DOTS client activates a drop-list or a rate-limit filter during an attack.
Consider a DOTS client that contacts its DOTS server during 'idle' time to install an accept-list that rate-limits all (or a part thereof) traffic to be forwarded to 2001:db8:123::/48 as a last resort countermeasure whenever required. Installing the accept-list can be done by sending, for example, the PUT request shown in Figure 9. The DOTS server installs this filter with a "deactivated" state.
PUT /restconf/data/ietf-dots-data-channel:dots-data\
/dots-client=OopPisZqo4SLv64TLPXrxA/acls\
/acl=my-ratelimit-list HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
{
"ietf-dots-data-channel:acls": {
"acl": [
{
"name": "my-ratelimit-list",
"type": "ipv6-acl-type",
"activation-type": "deactivate",
"aces": {
"ace": [
{
"name": "my-ace",
"matches": {
"ipv6": {
"destination-ipv6-network": "2001:db8:123::/48"
}
},
"actions": {
"forwarding": "accept",
"rate-limit": "20000.00"
}
}
]
}
}
]
}
}
Figure 9: DOTS Data Channel Request to Create a Rate-Limit Filter
Consider now that a DDoS attack is detected by the DOTS client on 2001:db8:123::/48. Consequently, the DOTS client sends a mitigation request to its DOTS server (Figure 10).
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=OopPisZqo4SLv64TLPXrxA"
Uri-Path: "mid=85"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:123::/48"
],
"lifetime": 3600
}
]
}
}
Figure 10: DOTS Signal Channel Mitigation Request
For some reason (e.g., the DOTS server, or the mitigator, is lacking a capability or capacity), the DOTS client is still receiving attack traffic which saturates available links. To soften the problem, the DOTS client decides to activate the filter that rate-limits the traffic destined to the DOTS client domain. To that aim, the DOTS client sends the mitigation request to its DOTS server shown in Figure 11.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=OopPisZqo4SLv64TLPXrxA"
Uri-Path: "mid=86"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:123::/48"
],
"ietf-dots-signal-control:acl-list": [
{
"ietf-dots-signal-control:acl-name": "my-ratelimit-list",
"ietf-dots-signal-control:activation-type": "immediate"
}
],
"lifetime": 3600
}
]
}
}
Figure 11: DOTS Signal Channel Mitigation Request to Activate a Rate-Limit Filter
Then, the DOTS server activates "my-ratelimit-list" ACL and replies with 2.04 (Changed) response to the DOTS client to confirm the successful operation.
As the attack mitigation evolves, the DOTS client may decide to deactivate the rate-limit policy (e.g., upon receipt of notification status change from 'attack-exceeded-capability' to 'attack-mitigation-in-progress'). Based on the mitigation status conveyed by the DOTS server, the DOTS client can de-activate the rate-limit action. It does so by sending the request shown in Figure 12.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=OopPisZqo4SLv64TLPXrxA"
Uri-Path: "mid=87"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:123::/48"
],
"ietf-dots-signal-control:acl-list": [
{
"ietf-dots-signal-control:acl-name": "my-ratelimit-list",
"ietf-dots-signal-control:activation-type": "deactivate"
}
],
"lifetime": 3600
}
]
}
}
Figure 12: DOTS Signal Channel Mitigation Request to Deactivate a Rate-Limit Filter
This specification registers the following parameters in the IANA "DOTS Signal Channel CBOR Key Values" registry established by [RFC8782] (https://www.iana.org/assignments/dots/dots.xhtml#dots-signal-channel-cbor-key-values).
+--------------------+--------+-------+------------+---------------+ | Parameter Name | CBOR | CBOR | Change | Specification | | | Key | Major | Controller | Document(s) | | | Value | Type | | | +====================+========+=======+============+===============+ |ietf-dots-signal- | | | | | |control:activation- | 52 | | | | | type | (TBA1) | 0 | IESG | [RFCXXXX] | |ietf-dots-signal- | 53 | | | | | control:acl-list | (TBA2) | 4 | IESG | [RFCXXXX] | |ietf-dots-signal- | 54 | | | | | control:acl-name | (TBA3) | 3 | IESG | [RFCXXXX] | +--------------------+--------+-------+------------+---------------+
This document requests IANA to register the following URI in the "ns" subregistry within the "IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-dots-signal-control Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace.
This document requests IANA to register the following YANG module in the "YANG Module Names" subregistry [RFC7950] within the "YANG Parameters" registry.
Name: ietf-dots-signal-control Namespace: urn:ietf:params:xml:ns:yang:ietf-dots-signal-control Maintained by IANA: N Prefix: dots-control Reference: RFC XXXX
The security considerations for the DOTS signal channel protocol are discussed in Section 10 of [RFC8782], while those for the DOTS data channel protocol are discussed in Section 10 of [RFC8783]. The following discusses the security considerations that are specific to the DOTS signal channel extension defined in this document.
This specification does not allow to create new filtering rules, which is the responsibility of the DOTS data channel. DOTS client domains should be adequately prepared prior to an attack, e.g., by creating filters that will be activated on demand when an attack is detected.
A DOTS client is entitled to access only to resources it creates. In particular, a DOTS client can not tweak filtering rules created by other DOTS clients of the same DOTS client domain. As a reminder, DOTS servers must associate filtering rules with the DOTS client that created these resources. Failure to ensure such association by a DOTS server will have severe impact on DOTS client domains.
A compromised DOTS client can use the filtering control capability to exacerbate an ongoing attack. Likewise, such a compromised DOTS client may abstain from reacting to an ACL conflict notification received from the DOTS server during attacks. These are not new attack vectors, but variations of threats discussed in [RFC8782] and [RFC8783]. DOTS operators should carefully monitor and audit DOTS agents to detect misbehaviors and to deter misuses.
Many thanks to Wei Pan, Xia Liang, Jon Shallow, Dan Wing, Christer Holmberg, and Shawn Emery for the comments.
Thanks to Benjamin Kaduk for the AD review.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC3688] | Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004. |
| [RFC7950] | Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016. |
| [RFC8174] | Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017. |
| [RFC8782] | Reddy.K, T., Boucadair, M., Patil, P., Mortensen, A. and N. Teague, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification", RFC 8782, DOI 10.17487/RFC8782, May 2020. |
| [RFC8783] | Boucadair, M. and T. Reddy.K, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Data Channel Specification", RFC 8783, DOI 10.17487/RFC8783, May 2020. |
| [Interop] | Nishizuka, K., Shallow, J. and L. Xia , "DOTS Interop test report, IETF 103 Hackathon", November 2018. |
| [RFC7951] | Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC 7951, DOI 10.17487/RFC7951, August 2016. |
| [RFC8340] | Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018. |
| [RFC8612] | Mortensen, A., Reddy, T. and R. Moskowitz, "DDoS Open Threat Signaling (DOTS) Requirements", RFC 8612, DOI 10.17487/RFC8612, May 2019. |