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| author | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
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| committer | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
| commit | 4bfd864f10b68b71482b35c818559068ef8d5797 (patch) | |
| tree | e3989f47a7994642eb325063d46e8f08ffa681dc /doc/rfc/rfc9066.txt | |
| parent | ea76e11061bda059ae9f9ad130a9895cc85607db (diff) | |
doc: Add RFC documents
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diff --git a/doc/rfc/rfc9066.txt b/doc/rfc/rfc9066.txt new file mode 100644 index 0000000..2891d55 --- /dev/null +++ b/doc/rfc/rfc9066.txt @@ -0,0 +1,1851 @@ + + + + +Internet Engineering Task Force (IETF) T. Reddy.K +Request for Comments: 9066 Akamai +Category: Standards Track M. Boucadair, Ed. +ISSN: 2070-1721 Orange + J. Shallow + December 2021 + + + Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal + Channel Call Home + +Abstract + + This document specifies the Denial-of-Service Open Threat Signaling + (DOTS) signal channel Call Home, which enables a Call Home DOTS + server to initiate a secure connection to a Call Home DOTS client and + to receive attack traffic information from the Call Home DOTS client. + The Call Home DOTS server in turn uses the attack traffic information + to identify compromised devices launching outgoing DDoS attacks and + take appropriate mitigation action(s). + + The DOTS signal channel Call Home is not specific to home networks; + the solution targets any deployment in which it is required to block + DDoS attack traffic closer to the source(s) of a DDoS attack. + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Further information on + Internet Standards is available in Section 2 of RFC 7841. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + https://www.rfc-editor.org/info/rfc9066. + +Copyright Notice + + Copyright (c) 2021 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 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. Terminology + 3. Applicability Scope + 4. Coexistence of a Base DOTS Signal Channel and DOTS Call Home + 5. DOTS Signal Channel Call Home + 5.1. Procedure + 5.2. DOTS Signal Channel Variations + 5.2.1. Heartbeat Mechanism + 5.2.2. Redirected Signaling + 5.3. DOTS Signal Channel Extension + 5.3.1. Mitigation Request + 5.3.2. Address Sharing Considerations + 6. DOTS Signal Call Home YANG Module + 6.1. Tree Structure + 6.2. YANG/JSON Mapping Parameters to CBOR + 6.3. YANG Module + 7. IANA Considerations + 7.1. DOTS Signal Channel CBOR Mappings Registry + 7.2. New DOTS Conflict Cause + 7.3. DOTS Signal Call Home YANG Module + 8. Security Considerations + 9. Privacy Considerations + 10. References + 10.1. Normative References + 10.2. Informative References + Appendix A. Some Home Network Issues + Appendix B. Disambiguating Base DOTS Signal vs. DOTS Call Home + Acknowledgements + Contributors + Authors' Addresses + +1. Introduction + + The Distributed Denial-of-Service Open Threat Signaling (DOTS) signal + channel protocol [RFC9132] is used to carry information about a + network resource or a network (or a part thereof) that is under a + Distributed Denial-of-Service (DDoS) attack [RFC4732]. Such + information is sent by a DOTS client to one or multiple DOTS servers + so that appropriate mitigation actions are undertaken on traffic + deemed suspicious. Various use cases are discussed in [RFC8903]. + + However, [RFC9132] only covers how to mitigate when being attacked + (i.e., protecting a network from inbound DDoS attacks). It does not + cover how to control the attacks close to their source(s) that are + misusing network resources (i.e., outbound DDoS attacks). In + particular, the DOTS signal protocol does not discuss cooperative + DDoS mitigation between the network hosting an attack source and the + Internet Service Provider (ISP) to suppress the outbound DDoS attack + traffic originating from that network. As a reminder, the base basic + DOTS architecture is depicted in Figure 1 (Section 2 of [RFC8811]). + + +-----------+ +-------------+ + | Mitigator | ~~~~~~~~~~ | DOTS Server | + +-----------+ +-------------+ + | + | + | + +---------------+ +-------------+ + | Attack Target | ~~~~~~ | DOTS Client | + +---------------+ +-------------+ + + Figure 1: Basic DOTS Architecture + + Appendix A details why the rise of Internet of Things (IoT) compounds + the possibility of these being used as malicious actors that need to + be controlled. Similar issues can be encountered in enterprise + networks, data centers, etc. The ISP offering a DDoS mitigation + service can detect outgoing DDoS attack traffic originating from its + subscribers, or the ISP may receive filtering rules (e.g., using BGP + Flowspec [RFC8955] [RFC8956]) from a transit provider to filter, + block, or rate-limit DDoS attack traffic originating from the ISP's + subscribers to a downstream target. Nevertheless, the DOTS signal + channel does not provide means for the ISP to request blocking such + attacks close to the sources without altering legitimate traffic. + This document fills that void by specifying an extension to the DOTS + signal channel: DOTS signal channel Call Home. + + Note: Another design approach would be to extend the DOTS signal + channel with a new attribute to explicitly indicate whether a + mitigation request concerns an outbound DDoS attack. In such an + approach, it is assumed that a DOTS server is deployed within the + domain that is hosting the attack source(s), while a DOTS client + is enabled within an upstream network (e.g., access network). + However, initiating a DOTS signal channel from an upstream network + to a source network is complicated because of the presence of + translators and firewalls. Moreover, the use of the same signal + channel to handle both inbound and outbound attacks complicates + both the heartbeat and redirection mechanisms that are executed as + a function of the attack direction (see Sections 5.2.1 and 5.2.2). + Also, the DOTS server will be subject to fingerprinting (e.g., + using scanning tools) and DoS attacks (e.g., by having the DOTS + server perform computationally expensive operations). Various + management and deployment considerations that motivate the Call + Home functionality are listed in Section 1.1 of [RFC8071]. + + "DOTS signal channel Call Home" (or "DOTS Call Home" for short) + refers to a DOTS signal channel established at the initiative of a + DOTS server thanks to a role reversal at the (D)TLS layer + (Section 5.1). That is, the DOTS server initiates a secure + connection to a DOTS client and uses that connection to receive the + attack traffic information (e.g., attack sources) from the DOTS + client. + + A high-level DOTS Call Home functional architecture is shown in + Figure 2. Attack source(s) are within the DOTS server domain. + + Scope + +.-.-.-.-.-.-.-.-.-.-.-.+ + +---------------+ : +-------------+ : + | Alert | ~~~:~~~ | Call Home | : + | | : | DOTS client | : + +---------------+ : +------+------+ : + : | : + : | : + : | : + +---------------+ : +------+------+ : + | Attack | ~~~:~~~ | Call Home | : + | Source(s) | : | DOTS server | : + +---------------+ : +-------------+ : + +.-.-.-.-.-.-.-.-.-.-.-.+ + + Figure 2: Basic DOTS Signal Channel Call Home Functional Architecture + + DOTS agents involved in the DOTS Call Home otherwise adhere to the + DOTS roles as defined in [RFC8612]. For clarity, this document uses + "Call Home DOTS client" (or "Call Home DOTS server") to refer to a + DOTS client (or DOTS server) deployed in a Call Home scenario + (Figure 2). Call Home DOTS agents may (or may not) be co-located + with DOTS agents that are compliant with [RFC9132] (see Section 4 for + more details). + + A Call Home DOTS client relies upon a variety of triggers to make use + of the Call Home function (e.g., scrubbing the traffic from the + attack source or receiving an alert from an attack target, a peer + DDoS Mitigation System (DMS), or a transit provider). The definition + of these triggers is deployment specific. It is therefore out of the + scope of this document to elaborate on how these triggers are made + available to a Call Home DOTS client. + + In a typical deployment scenario, the Call Home DOTS server is + enabled on a Customer Premises Equipment (CPE), which is aligned with + recent trends to enrich the CPE with advanced security features. For + example, the DOTS Call Home service can be part of services supported + by an ISP-managed CPE or a managed security service subscribed to by + the user. Unlike classic DOTS deployments [RFC8903], a Call Home + DOTS server maintains a single DOTS signal channel session for each + DOTS-capable upstream provisioning domain [DOTS-MULTIHOMING]. + + For instance, the Call Home DOTS server in the home network initiates + the signal channel Call Home in "idle" time; subsequently, the Call + Home DOTS client in the ISP environment can initiate a mitigation + request whenever the ISP detects there is an attack from a + compromised device in the DOTS server domain (i.e., from within the + home network). + + The Call Home DOTS server uses the DDoS attack traffic information to + identify the compromised device in its domain that is responsible for + launching the DDoS attack, optionally notifies a network + administrator, and takes appropriate mitigation action(s). For + example, a mitigation action can be to quarantine the compromised + device or block its traffic to the attack target(s) until the + mitigation request is withdrawn. + + This document assumes that Call Home DOTS servers are provisioned + with a way to know how to reach the upstream Call Home DOTS + client(s), which could occur by a variety of means (e.g., [RFC8973]). + The specification of such means are out of scope of this document. + + More information about the applicability scope of the DOTS signal + channel Call Home is provided in Section 3. + +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. + + The reader should be familiar with the terms defined in Section 1.2 + of [RFC8612]. + + "DDoS Mitigation System (DMS)" refers to a system that performs DDoS + mitigation. + + "Base DOTS signal channel" refers to [RFC9132]. + + The meaning of the symbols in YANG tree diagrams are defined in + [RFC8340] and [RFC8791]. + + (D)TLS is used for statements that apply to both Transport Layer + Security (TLS) [RFC8446] and Datagram Transport Layer Security (DTLS) + [RFC6347] [DTLS13]. Specific terms are used for any statement that + applies to either protocol alone. + +3. Applicability Scope + + The problems discussed in Section 1 may be encountered in many + deployments (e.g., home networks, enterprise networks, transit + networks, data centers). The solution specified in this document can + be used for those deployments to block DDoS attack traffic closer to + the source(s) of the attack. That is, attacks that are issued, e.g., + from within an enterprise network or a data center will thus be + blocked before exiting these networks. + + An instantiation of the Call Home functional architecture is depicted + in Figure 3. + + +-------------+ + |Attack Target| + +-----+-------+ + | /\ Target Network + ......................|.||.................... + .--------+-||-------. + ( || )-. + .' || ' + ( Internet || ) + ( || -' + '-( || ) + '------+-||---------' + ......................|.||..................... + .--------+-||-------. Network + ( || )-. Provider + .' Call Home || ' (DMS) + ( DOTS client || ) + ( || -' + '-( || ) + '------+-||---------' + ......................|.||....................... + .--------+-||-------. Source Network + ( || )-. + .' Call Home || ' + ( DOTS server || Outbound ) + ( || DDoS -' + '-( || Attack ) + '------+-||---------' + | || + +-----+-++----+ + |Attack Source| + +-------------+ + + Figure 3: DOTS Signal Channel Call Home Reference Architecture + + It is out of the scope of this document to identify an exhaustive + list of such deployments. + + Call Home DOTS agent relationships are similar to those discussed in + Section 2.3 of [RFC8811]. For example, multiple Call Home DOTS + servers of the same domain can be associated with the same Call Home + DOTS client. A Call Home DOTS client may decide to contact these + Call Home DOTS servers sequentially, fork a mitigation request to all + of them, or select one Call Home DOTS server to place a mitigation + request. Such a decision is implementation specific. + + For some mitigations, feedback may be required from an administrator + to confirm a filtering action. The means to seek an administrator's + consent are deployment specific. Indeed, a variety of implementation + options can be considered for any given Call Home DOTS deployment, + such as push notifications using a dedicated application, Syslog, + etc. It is out of the scope of this document to make recommendations + about how such interactions are implemented (see Figure 2). + + The Call Home DOTS server can be enabled on a border router or a + dedicated appliance. For the particular case of home networks, the + Call Home DOTS server functionality can be enabled on a managed CPE + or bundled with a CPE management application that is provided by an + ISP to its subscribers. These managed services are likely to be + designed to hide the complexity of managing (including configuring) + the CPE. For example, managed CPEs support the means to notify the + user when a new device is detected in order to seek confirmation as + to whether or not access should be granted to the device. These + means can be upgraded to interface with the Call Home DOTS server. + Customized settings can be configured by users to control the + notifications (e.g., triggers, type) and default actions. + +4. Coexistence of a Base DOTS Signal Channel and DOTS Call Home + + The DOTS signal channel Call Home does not require or preclude the + activation of the base DOTS signal channel [RFC9132]. Some sample + deployment schemes are discussed in this section for illustration + purposes. + + The network that hosts an attack source may also be subject to + inbound DDoS attacks. In that case, both the base DOTS signal + channel and DOTS signal channel Call Home may be enabled as shown in + Figure 4 (same DMS provider) or Figure 5 (distinct DMS providers). + + DOTS Signal Channel Base DOTS + Call Home Signal Channel + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + : +------+ :: +------+ : + : | DOTS | :: | DOTS | : + : |client| :: |server| : + : +--+---+ :: +---+--+ : + : /\ | :: | : Network + : || | :: | :Provider + : || | :: | : (DMS) + ...:.....||......|.....::.....|.............:........ + Outbound || | :: | || Inbound + DDoS || | :: | || DDoS + Attack || | :: | \/ Attack + : +--+---+ :: +---+--+ : + : | DOTS | :: | DOTS | : + : |server| :: |client| : + : +------+ :: +------+ : + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + Network #A + + Figure 4: Activation of a Base DOTS Signal Channel and Call Home + (Same DMS Provider) + + Note that a DMS provider may not be on the default forwarding path of + inbound DDoS attack traffic targeting a network (e.g., Network #B in + Figure 5). Nevertheless, the DOTS signal channel Call Home requires + the DMS provider to be on the default forwarding path of the outbound + traffic from a given network. + + DOTS Signal Channel Base DOTS + Call Home Signal Channel + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + : Network +------+ :: +------+ Third : + : Provider | DOTS | :: | DOTS | Party : + : (DMS) |client| :: |server| DMS : + : +--+---+ :: +---+--+ Provider : + : /\ | :: | : + : || | :: | : + : || | :: | : + ...:.....||......|.....::.....|.............:........ + Outbound || | :: | || Inbound + DDoS || | :: | || DDoS + Attack || | :: | \/ Attack + : +--+---+ :: +---+--+ : + : | DOTS | :: | DOTS | : + : |server| :: |client| : + : +------+ :: +------+ : + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + Network #B + + Figure 5: Activation of a Base DOTS Signal Channel and Call Home + (Distinct DMS Providers) + + Figures 6 and 7 depict examples where the same node embeds both base + DOTS and Call Home DOTS agents. For example, a DOTS server and a + Call Home DOTS client may be enabled on the same device within the + infrastructure of a DMS provider (e.g., Node #i in Figure 6), or a + DOTS client and a Call Home DOTS server may be enabled on the same + device within a source network (e.g., Node #j with Network #D shown + in Figure 7). + + Whether the same or distinct nodes are used to host base DOTS and + Call Home DOTS agents is specific to each domain. + + DOTS Signal Channel Base DOTS + Call Home Signal Channel + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + : +----------------------+ : + : | Node #i | : + : | +------+ +------+ | : + : | | DOTS | | DOTS | | : + : | |client| |server| | : + : | +--+---+ +---+--+ | : + : +----|-----::-----|----+ : Network + : /\ | :: | :Provider + : || | :: | : (DMS) + ...:.....||......|.....::.....|.............:........ + Outbound || | :: | || Inbound + DDoS || | :: | || DDoS + Attack || | :: | \/ Attack + : +--+---+ :: +---+--+ : + : | DOTS | :: | DOTS | : + : |server| :: |client| : + : +------+ :: +------+ : + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + Network #C + + Figure 6: The Same Node Embedding a Call Home DOTS Client and a + DOTS Server at the Network Provider's Side + + DOTS Signal Channel Base DOTS + Call Home Signal Channel + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + : +----------------------+ : + : | Node #k | : + : | +------+ +------+ | : + : | | DOTS | | DOTS | | : + : | |client| |server| | : + : | +--+---+ +---+--+ | : + : +----|-----::-----|----+ : Network + : /\ | :: | :Provider + : || | :: | : (DMS) + ...:.....||......|.....::.....|.............:........ + Outbound || | :: | || Inbound + DDoS || | :: | || DDoS + Attack || | :: | \/ Attack + : +----|-----::-----|----+ : + : | +--+---+ +---+--+ | : + : | | DOTS | | DOTS | | : + : | |server| |client| | : + : | +------+ +------+ | : + : | Node #j | : + : +----------------------+ : + +-.-.-.-.-.-.-.-.-.-++-.-.-.-.-.-.-.-.-.-+ + Network #D + + Figure 7: The Same Node Embedding both a DOTS Client and a Call + Home DOTS Server + + Appendix B elaborates on the considerations to unambiguously + distinguish DOTS messages that belong to each of these channels. + +5. DOTS Signal Channel Call Home + +5.1. Procedure + + The DOTS signal channel Call Home preserves all but one of the DOTS + client/server roles in the DOTS protocol stack, as compared to the + client-initiated DOTS signal channel protocol [RFC9132]. The role + reversal that occurs is at the (D)TLS layer; that is, (1) the Call + Home DOTS server acts as a DTLS client, and the Call Home DOTS client + acts as a DTLS server; or (2) the Call Home DOTS server acts as a TLS + client initiating the underlying TCP connection, and the Call Home + DOTS client acts as a TLS server. The Call Home DOTS server + initiates a (D)TLS handshake to the Call Home DOTS client. + + For example, a home network element (e.g., home router) co-located + with a Call Home DOTS server is the (D)TLS client. That is, the Call + Home DOTS server assumes the role of the (D)TLS client, but the + network element's role as a DOTS server remains the same. + + Existing certificate chains and mutual authentication mechanisms + between the DOTS agents are unaffected by the Call Home function. + From a deployment standpoint, and given the scale of Call Home DOTS + servers that may be involved, enabling means for automating the + provisioning of credentials on Call Home DOTS servers to authenticate + to the Call Home DOTS client is encouraged. It is out of the scope + of this document to elaborate on these means. + + Figure 8 illustrates a sample DOTS Call Home flow exchange: + + +-----------+ +-----------+ + | Call Home | | Call Home | + | DOTS | | DOTS | + | server | | client | + +-----+-----+ +-----+-----+ + (D)TLS client (D)TLS server + | | + | 1. (D)TLS connection | + |----------------------------------->| + | 2. Mitigation request | + |<-----------------------------------| + | ... | + + Figure 8: DOTS Signal Channel Call Home Sequence Diagram + + The DOTS signal channel Call Home procedure is as follows: + + 1. If UDP transport is used, the Call Home DOTS server begins by + initiating a DTLS connection to the Call Home DOTS client. + + If TCP is used, the Call Home DOTS server begins by initiating a + TCP connection to the Call Home DOTS client. Once connected, the + Call Home DOTS server continues to initiate a TLS connection to + the Call Home DOTS client. + + Peer DOTS agents may have mutual agreement to use a specific port + number, such as by explicit configuration or dynamic discovery + [RFC8973]. The interaction between the base DOTS signal channel + and the Call Home is discussed in Appendix B. + + The Happy Eyeballs mechanism explained in Section 4.3 of + [RFC9132] is used for initiating (D)TLS connections. + + 2. Using this (D)TLS connection, the Call Home DOTS client may + request, withdraw, or retrieve the status of mitigation requests. + The Call Home DOTS client supplies the source information by + means of new attributes defined in Section 5.3.1. + + The heartbeat mechanism used for the DOTS Call Home deviates from + the one defined in Section 4.7 of [RFC9132]. Section 5.2.1 + specifies the behavior to be followed by Call Home DOTS agents. + + +5.2. DOTS Signal Channel Variations + + +5.2.1. Heartbeat Mechanism + + Once the (D)TLS section is established between the DOTS agents, the + Call Home DOTS client contacts the Call Home DOTS server to retrieve + the session configuration parameters (Section 4.5 of [RFC9132]). The + Call Home DOTS server adjusts the "heartbeat-interval" to accommodate + binding timers used by on-path NATs and firewalls. Heartbeats will + then be exchanged by the DOTS agents following the instructions + retrieved using the signal channel session configuration exchange. + + It is the responsibility of Call Home DOTS servers to ensure that on- + path translators/firewalls are maintaining a binding so that the same + external IP address and/or port number is retained for the DOTS + signal channel session. A Call Home DOTS client MAY trigger their + heartbeat requests immediately after receiving heartbeat probes from + its peer Call Home DOTS server. + + When an outgoing attack that saturates the outgoing link from the + Call Home DOTS server is detected and reported by a Call Home DOTS + client, the latter MUST continue to use the DOTS signal channel even + if no traffic is received from the Call Home DOTS server. + + If the Call Home DOTS server receives traffic from the Call Home DOTS + client, the Call Home DOTS server MUST continue to use the DOTS + signal channel even if the threshold of allowed missing heartbeats + ("missing-hb-allowed") is reached. + + If the Call Home DOTS server does not receive any traffic from the + peer Call Home DOTS client during the time span required to exhaust + the maximum "missing-hb-allowed" threshold, the Call Home DOTS server + concludes the session is disconnected. Then, the Call Home DOTS + server MUST try to establish a new DOTS signal channel session, + preferably by resuming the (D)TLS session. + +5.2.2. Redirected Signaling + + A Call Home DOTS server MUST NOT support the redirected signaling + mechanism as specified in Section 4.6 of [RFC9132] (i.e., a 5.03 + response that conveys an alternate DOTS server's Fully Qualified + Domain Name (FQDN) or IP address(es)). A Call Home DOTS client MUST + silently discard such a message as only a Call Home DOTS server can + initiate a new (D)TLS connection. + + If a Call Home DOTS client wants to redirect a Call Home DOTS server + to another Call Home DOTS client, it MUST send a Non-confirmable PUT + request to the predefined resource ".well-known/dots/redirect" with + the following attributes in the body of the PUT request: + + alt-ch-client: The FQDN of an alternate Call Home DOTS client. It + is also presented as a reference identifier for authentication + purposes. + + This is a mandatory attribute for DOTS signal Call Home. It MUST + NOT be used for base DOTS signal channel operations. + + alt-ch-client-record: List of IP addresses for the alternate Call + Home DOTS client. If no "alt-ch-client-record" is provided, the + Call Home DOTS server passes the "alt-ch-client" name to a name + resolution library to retrieve one or more IP addresses of the + alternate Call Home DOTS client. + + This is an optional attribute for DOTS signal Call Home. It MUST + NOT be used for base DOTS signal channel operations. + + ttl: The Time To Live (TTL) of the alternate Call Home DOTS client. + That is, the time interval in which the alternate Call Home DOTS + client may be cached for use by a Call Home DOTS server. + + This is an optional attribute for DOTS signal Call Home. It MUST + NOT be used for base DOTS signal channel operations. + + On receipt of this PUT request, the Call Home DOTS server responds + with a 2.01 (Created), closes this connection, and establishes a + connection with the new Call Home DOTS client. The processing of the + TTL is defined in Section 4.6 of [RFC9132]. If the Call Home DOTS + server cannot service the PUT request, the response is rejected with + a 4.00 (Bad Request). + + Figure 9 shows a PUT request example to convey the alternate Call + Home DOTS client "alt-call-home-client.example" together with its IP + addresses 2001:db8:6401::1 and 2001:db8:6401::2. The validity of + this alternate Call Home DOTS client is 10 minutes. + + Header: PUT (Code=0.03) + Uri-Path: ".well-known" + Uri-Path: "dots" + Uri-Path: "redirect" + Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" + Uri-Path: "mid=123" + Content-Format: "application/dots+cbor" + + { + "ietf-dots-signal-channel:redirected-signal": { + "ietf-dots-call-home:alt-ch-client": + "alt-call-home-client.example", + "ietf-dots-call-home:alt-ch-client-record": [ + "2001:db8:6401::1", + "2001:db8:6401::2" + ], + "ietf-dots-call-home:ttl": 600 + } + + Figure 9: Example of a PUT Request for Redirected Signaling + + Figure 9 uses the JSON encoding of YANG-modeled data for the CoAP + message body. The same encoding is used in Figure 10 + (Section 5.3.1). + +5.3. DOTS Signal Channel Extension + +5.3.1. Mitigation Request + + This specification extends the mitigation request defined in + Section 4.4.1 of [RFC9132] to convey the attack source information + (e.g., source prefixes, source port numbers). The DOTS client + conveys the following new parameters in the Concise Binary Object + Representation (CBOR) body of the mitigation request: + + source-prefix: A list of attacker IP prefixes used to attack the + target. Prefixes are represented using Classless Inter-Domain + Routing (CIDR) notation (BCP 122 [RFC4632]). + + As a reminder, the prefix length MUST be less than or equal to 32 + (or 128) for IPv4 (or IPv6). + + The prefix list MUST NOT include broadcast, loopback, or multicast + addresses. These addresses are considered invalid values. Note + that link-local addresses are allowed. The Call Home DOTS client + MUST validate that attacker prefixes are within the scope of the + Call Home DOTS server domain (e.g., prefixes assigned to the Call + Home DOTS server domain or networks it services). This check is + meant to avoid contacting Call Home DOTS servers that are not + entitled to enforce actions on specific prefixes. + + This is an optional attribute for the base DOTS signal channel + operations. + + source-port-range: A list of port numbers used by the attack traffic + flows. + + A port range is defined by two bounds, a lower port number + ("lower-port") and an upper port number ("upper-port"). When only + "lower-port" is present, it represents a single port number. + + For TCP, UDP, Stream Control Transmission Protocol (SCTP) + [RFC4960], or Datagram Congestion Control Protocol (DCCP) + [RFC4340], a range of ports can be any subrange of 0-65535 -- for + example, 0-1023, 1024-65535, or 1024-49151. + + This is an optional attribute for the base DOTS signal channel + operations. + + source-icmp-type-range: A list of ICMP types used by the attack + traffic flows. An ICMP type range is defined by two bounds, a + lower ICMP type (lower-type) and an upper ICMP type (upper-type). + When only "lower-type" is present, it represents a single ICMP + type. Both ICMP [RFC0792] and ICMPv6 [RFC4443] types are + supported. Whether ICMP or ICMPv6 types are to be used is + determined by the address family of the "target-prefix". + + This is an optional attribute for the base DOTS signal channel + operations. + + The "source-prefix" parameter is a mandatory attribute when the + attack traffic information is signaled by a Call Home DOTS client + (i.e., the Call Home scenario depicted in Figure 8). The "target- + prefix" attribute MUST be included in the mitigation request + signaling the attack information to a Call Home DOTS server. The + "target-uri" or "target-fqdn" parameters can be included in a + mitigation request for diagnostic purposes to notify the Call Home + DOTS server domain administrator but SHOULD NOT be used to determine + the target IP addresses. "alias-name" is unlikely to be conveyed in + a Call Home mitigation request given that a target may be any IP + resource and that there is no incentive for a Call Home DOTS server + (embedded, for example, in a CPE) to maintain aliases. + + In order to help attack source identification by a Call Home DOTS + server, the Call Home DOTS client SHOULD include in its mitigation + request additional information such as "source-port-range" or + "source-icmp-type-range" to disambiguate nodes sharing the same + "source-prefix". IPv6 addresses/prefixes are sufficient to uniquely + identify a network endpoint, without need for port numbers or ICMP + type information. While this is also possible for IPv4, it is much + less often the case than for IPv6. More address sharing implications + on the setting of source information ("source-prefix", "source-port- + range") are discussed in Section 5.3.2. + + Only immediate mitigation requests (i.e., "trigger-mitigation" set to + "true") are allowed; Call Home DOTS clients MUST NOT send requests + with "trigger-mitigation" set to "false". Such requests MUST be + discarded by the Call Home DOTS server with a 4.00 (Bad Request). + + An example of a mitigation request sent by a Call Home DOTS client is + shown in Figure 10. + + Header: PUT (Code=0.03) + Uri-Path: ".well-known" + Uri-Path: "dots" + Uri-Path: "mitigate" + Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" + Uri-Path: "mid=56" + Content-Format: "application/dots+cbor" + + { + "ietf-dots-signal-channel:mitigation-scope": { + "scope": [ + { + "target-prefix": [ + "2001:db8:c000::/128" + ], + "ietf-dots-call-home:source-prefix": [ + "2001:db8:123::1/128" + ], + "lifetime": 3600 + } + ] + } + } + + Figure 10: An Example of a Mitigation Request Issued by a Call + Home DOTS Client + + The Call Home DOTS server MUST check that the "source-prefix" is + within the scope of the Call Home DOTS server domain. Note that in a + DOTS Call Home scenario, the Call Home DOTS server considers, by + default, that any routable IP prefix enclosed in "target-prefix" is + within the scope of the Call Home DOTS client. Invalid mitigation + requests are handled as per Section 4.4.1 of [RFC9132]. + + Note: These validation checks do not apply when the source + information is included as a hint in the context of the base DOTS + signal channel. + + Call Home DOTS server domain administrator consent MAY be required to + block the traffic from the compromised device to the attack target. + An implementation MAY have a configuration knob to block the traffic + from the compromised device to the attack target with or without DOTS + server domain administrator consent. + + If consent from the Call Home DOTS server domain administrator is + required, the Call Home DOTS server replies with 2.01 (Created) and + the "status" code set to 1 (attack-mitigation-in-progress). Then, + the mechanisms defined in Section 4.4.2 of [RFC9132] are followed by + the DOTS agents to update the mitigation status. In particular, if + the attack traffic is blocked, the Call Home DOTS server informs the + Call Home DOTS client that the attack is being mitigated (i.e., by + setting the "status" code to 2 (attack-successfully-mitigated)). + + If the attack traffic information is identified by the Call Home DOTS + server or the Call Home DOTS server domain administrator as + legitimate traffic, the mitigation request is rejected with a 4.09 + (Conflict) (e.g., when no consent is required from an administrator) + or a notification message with the "conflict-clause" (Section 4.4.1 + of [RFC9132]) set to the following new value: + + 4: Mitigation request rejected. This code is returned by the DOTS + server to indicate the attack traffic has been classified as + legitimate traffic. + + Once the request is validated by the Call Home DOTS server, + appropriate actions are enforced to block the attack traffic within + the source network. For example, if the Call Home DOTS server is + embedded in a CPE, it can program the packet processor to punt all + the traffic from the compromised device to the target to slow path. + The CPE inspects the punted slow path traffic to detect and block the + outgoing DDoS attack traffic or quarantine the device (e.g., using + MAC-level filtering) until it is remediated and notifies the CPE + administrator about the compromised device. Note that the Call Home + DOTS client is informed about the progress of the attack mitigation + following the rules in Section 4.4.2 of [RFC9132]. + + The DOTS agents follow the same procedures specified in [RFC9132] for + managing a mitigation request. + +5.3.2. Address Sharing Considerations + + Figure 11 depicts an example of a network provider that hosts a Call + Home DOTS client and deploys a Carrier-Grade NAT (CGN) between the + DOTS client domain and DOTS server domain. In such cases, + communicating an external IP address in a mitigation request by a + Call Home DOTS client is likely to be discarded by the Call Home DOTS + server because the external IP address is not visible locally to the + Call Home DOTS server (Figure 11). The Call Home DOTS server is only + aware of the internal IP addresses/prefixes bound to its domain + (i.e., those used in the internal realm shown in Figure 11). Thus, + Call Home DOTS clients that are aware of the presence of on-path CGNs + MUST NOT include the external IP address and/or port number + identifying the suspect attack source (i.e., those used in the + external realm shown in Figure 11) but MUST include the internal IP + address and/or port number. To that aim, the Call Home DOTS client + SHOULD rely on mechanisms, such as those described in [RFC8512] or + [RFC8513], to retrieve the internal IP address and port number that + are mapped to an external IP address and port number. For the + particular case of NAT64 [RFC6146], if the target address is an IPv4 + address, the IPv4-converted IPv6 address of this target address + [RFC6052] SHOULD be used. + + N | .-------------------. + E | ( )-. + T | .' ' + W | ( Call Home ) + O | ( DOTS client -' + R | '-( ) + K | '-------+-----------' + | | + P | | + R | +---+---+ + O | | CGN | External Realm + V |..............| |...................... + I | | | Internal Realm + D | +---+---+ + E | | + R | | + --- | + .---------+---------. + ( )-. + .' Source Network ' + ( ) + ( Call Home -' + '-( DOTS server ) + '------+------------' + | + +-----+-------+ + |Attack Source| + +-------------+ + + Figure 11: Example of a CGN between DOTS Domains + + If a Mapping of Address and Port (MAP) Border Relay [RFC7597] or + Lightweight Address Family Transition Router (lwAFTR) [RFC7596] is + enabled in the provider's domain to service its customers, the + identification of an attack source bound to an IPv4 address/prefix + MUST also rely on source port numbers because the same IPv4 address + is assigned to multiple customers. The port information is required + to unambiguously identify the source of an attack. + + If a translator is enabled on the boundaries of the domain hosting + the Call Home DOTS server (e.g., a CPE with NAT enabled as shown in + Figures 12 and 13), the Call Home DOTS server uses the attack traffic + information conveyed in a mitigation request to find the internal + source IP address of the compromised device and blocks the traffic + from the compromised device traffic to the attack target until the + mitigation request is withdrawn. The Call Home DOTS server proceeds + with a NAT mapping table lookup using the attack information (or a + subset thereof) as a key. The lookup can be local (Figure 12) or via + a dedicated administration interface that is offered by the CPE + (Figure 13). This identification allows the suspicious device to be + isolated while avoiding disturbances of other services. + + .-------------------. + ( )-. + .' Network Provider (DMS)' + ( ) + ( Call Home -' + '-( DOTS client ) + '-------+-----------' + | + --- +---+---+ + S | | CPE | External Realm + O |..............| |................ + U | | NAT | Internal Realm + R | +---+---+ + C | | + E | .---------+---------. + | ( )-. + N | .' ' + E | ( Call Home ) + T | ( DOTS server -' + W | '-( ) + O | '-------+-----------' + R | | + K | +------+------+ + | |Attack Source| + +-------------+ + + Figure 12: Example of a DOTS Server Domain with a NAT Embedded in + a CPE + + .-------------------. + ( )-. + .' Network Provider (DMS) ' + ( ) + ( Call Home -' + '-( DOTS client ) + '---------+---------' + | + --- +-----+-----+ + S | | CPE/NAT | External Realm + O |..............| |................ + U | | Call Home | Internal Realm + R | |DOTS server| + C | +-----+-----+ + E | | + | .-----------+-------. + | ( )-. + N | .' ' + E | ( Local Area Network ) + T | ( -' + W | '-( ) + O | '--------+----------' + R | | + K | +------+------+ + | |Attack Source| + +-------------+ + + Figure 13: Example of a Call Home DOTS Server and a NAT Embedded + in a CPE + + If, for any reason, address sharing is deployed in both source and + provider networks, both Call Home DOTS agents have to proceed with + address mapping lookups following the behavior specified in reference + to Figure 11 (network provider) and Figures 12 and 13 (source + network). + +6. DOTS Signal Call Home YANG Module + +6.1. Tree Structure + + This document augments the "ietf-dots-signal-channel" (dots-signal) + DOTS signal YANG module defined in [RFC9132] for signaling the attack + traffic information. This document defines the YANG module "ietf- + dots-call-home", which has the following tree structure: + + module: ietf-dots-call-home + + augment-structure /dots-signal:dots-signal/dots-signal:message-type + /dots-signal:mitigation-scope/dots-signal:scope: + +-- source-prefix* inet:ip-prefix + +-- source-port-range* [lower-port] + | +-- lower-port inet:port-number + | +-- upper-port? inet:port-number + +-- source-icmp-type-range* [lower-type] + +-- lower-type uint8 + +-- upper-type? uint8 + augment-structure /dots-signal:dots-signal/dots-signal:message-type + /dots-signal:redirected-signal: + +-- (type)? + +--:(call-home-only) + +-- alt-ch-client inet:domain-name + +-- alt-ch-client-record* inet:ip-address + +-- ttl? uint32 + +6.2. YANG/JSON Mapping Parameters to CBOR + + The YANG/JSON mapping parameters to CBOR are listed in Table 1. + + Note: Implementers must check that the mapping output provided by + their YANG-to-CBOR encoding schemes is aligned with the content of + Table 1. + + +========================+=============+=====+=============+========+ + |Parameter Name |YANG Type |CBOR |CBOR Major | JSON | + | | |Key |Type & | Type | + | | |Value|Information | | + +========================+=============+=====+=============+========+ + |ietf-dots-call- |leaf-list |32768|4 array | Array | + |home:source-prefix |inet:ip- | |3 text string| String | + | |prefix | | | | + +------------------------+-------------+-----+-------------+--------+ + |ietf-dots-call- |list |32769|4 array | Array | + |home:source-port-range | | | | | + +------------------------+-------------+-----+-------------+--------+ + |ietf-dots-call- |list |32770|4 array | Array | + |home:source-icmp-type- | | | | | + |range | | | | | + +------------------------+-------------+-----+-------------+--------+ + |lower-type |uint8 |32771|0 unsigned | Number | + +------------------------+-------------+-----+-------------+--------+ + |upper-type |uint8 |32772|0 unsigned | Number | + +------------------------+-------------+-----+-------------+--------+ + |ietf-dots-call-home:alt-|inet: domain-|32773|3 text string| String | + |ch-client |name | | | | + +------------------------+-------------+-----+-------------+--------+ + |ietf-dots-call-home:alt-|leaf-list |32774|4 array | Array | + |ch-client-record |inet:ip- | |3 text string| String | + | |address | | | | + +------------------------+-------------+-----+-------------+--------+ + |ietf-dots-call-home:ttl |uint32 |32775|0 unsigned | Number | + +------------------------+-------------+-----+-------------+--------+ + + Table 1: YANG/JSON Mapping Parameters to CBOR + + The YANG/JSON mappings to CBOR for "lower-port" and "upper-port" are + already defined in Table 5 of [RFC9132]. + +6.3. YANG Module + + This module uses the common YANG types defined in [RFC6991] and the + data structure extension defined in [RFC8791]. + + <CODE BEGINS> file "ietf-dots-call-home@2021-12-09.yang" + module ietf-dots-call-home { + yang-version 1.1; + namespace "urn:ietf:params:xml:ns:yang:ietf-dots-call-home"; + prefix dots-call-home; + + import ietf-inet-types { + prefix inet; + reference + "Section 4 of RFC 6991"; + } + import ietf-dots-signal-channel { + prefix dots-signal; + reference + "RFC 9132: Distributed Denial-of-Service Open Threat + Signaling (DOTS) Signal Channel Specification"; + } + import ietf-yang-structure-ext { + prefix sx; + reference + "RFC 8791: YANG Data Structure Extensions"; + } + + 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: Konda, Tirumaleswar Reddy + <mailto:kondtir@gmail.com>; + + Author: Mohamed Boucadair + <mailto:mohamed.boucadair@orange.com>; + + Author: Jon Shallow + <mailto:ietf-supjps@jpshallow.com>"; + description + "This module contains YANG definitions for the signaling + messages exchanged between a DOTS client and a DOTS server + for the Call Home deployment scenario. + + Copyright (c) 2021 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 9066; see + the RFC itself for full legal notices."; + + revision 2021-12-09 { + description + "Initial revision."; + reference + "RFC 9066: Distributed Denial-of-Service Open Threat + Signaling (DOTS) Signal Channel Call Home"; + } + sx:augment-structure "/dots-signal:dots-signal" + + "/dots-signal:message-type" + + "/dots-signal:mitigation-scope" + + "/dots-signal:scope" { + description + "Attack source details."; + leaf-list source-prefix { + type inet:ip-prefix; + description + "IPv4 or IPv6 prefix identifying the attack source(s)."; + } + list source-port-range { + key "lower-port"; + description + "Port range. When only lower-port is + present, it represents a single port number."; + leaf lower-port { + type inet:port-number; + description + "Lower port number of the port range."; + } + leaf upper-port { + type inet:port-number; + must '. >= ../lower-port' { + error-message + "The upper port number must be greater than + or equal to the lower port number."; + } + description + "Upper port number of the port range."; + } + } + list source-icmp-type-range { + key "lower-type"; + description + "ICMP/ICMPv6 type range. When only lower-type is + present, it represents a single ICMP/ICMPv6 type. + + The address family of the target-prefix is used + to determine whether ICMP or ICMPv6 is used."; + leaf lower-type { + type uint8; + description + "Lower ICMP/ICMPv6 type of the ICMP type range."; + reference + "RFC 792: Internet Control Message Protocol + RFC 4443: Internet Control Message Protocol (ICMPv6) + for the Internet Protocol Version 6 (IPv6) + Specification."; + } + leaf upper-type { + type uint8; + must '. >= ../lower-type' { + error-message + "The upper ICMP/ICMPv6 type must be greater than + or equal to the lower ICMP type."; + } + description + "Upper type of the ICMP type range."; + reference + "RFC 792: Internet Control Message Protocol + RFC 4443: Internet Control Message Protocol (ICMPv6) + for the Internet Protocol Version 6 (IPv6) + Specification."; + } + } + } + sx:augment-structure "/dots-signal:dots-signal" + + "/dots-signal:message-type" + + "/dots-signal:redirected-signal" { + description + "Augments the redirected signal to communicate an + alternate Call Home DOTS client."; + choice type { + description + "Indicates the type of the DOTS session (e.g., base + DOTS signal channel, DOTS Call Home)."; + case call-home-only { + description + "These attributes appear only in a signal Call Home + channel message from a Call Home DOTS client + to a Call Home DOTS server."; + leaf alt-ch-client { + type inet:domain-name; + mandatory true; + description + "FQDN of an alternate Call Home DOTS client. + + This name is also presented as a reference + identifier for authentication purposes."; + } + leaf-list alt-ch-client-record { + type inet:ip-address; + description + "List of IP addresses for the alternate Call + Home DOTS client. + + If this data node is not present, a Call Home + DOTS server resolves the alt-ch-client into + one or more IP addresses."; + } + leaf ttl { + type uint32; + units "seconds"; + description + "The Time To Live (TTL) of the alternate Call Home + DOTS client."; + reference + "Section 4.6 of RFC 9132"; + } + } + } + } + } + <CODE ENDS> + +7. IANA Considerations + + +7.1. DOTS Signal Channel CBOR Mappings Registry + + This specification registers the following comprehension-optional + parameters (Table 2) in the IANA "DOTS Signal Channel CBOR Key + Values" registry [Key-Map]. + + +========================+=======+=======+============+===========+ + | Parameter Name | CBOR | CBOR | Change | Reference | + | | Key | Major | Controller | | + | | Value | Type | | | + +========================+=======+=======+============+===========+ + | ietf-dots-call- | 32768 | 4 | IESG | RFC 9066 | + | home:source-prefix | | | | | + +------------------------+-------+-------+------------+-----------+ + | ietf-dots-call- | 32769 | 4 | IESG | RFC 9066 | + | home:source-port-range | | | | | + +------------------------+-------+-------+------------+-----------+ + | ietf-dots-call- | 32770 | 4 | IESG | RFC 9066 | + | home:source-icmp-type- | | | | | + | range | | | | | + +------------------------+-------+-------+------------+-----------+ + | lower-type | 32771 | 0 | IESG | RFC 9066 | + +------------------------+-------+-------+------------+-----------+ + | upper-type | 32772 | 0 | IESG | RFC 9066 | + +------------------------+-------+-------+------------+-----------+ + | ietf-dots-call- | 32773 | 3 | IESG | RFC 9066 | + | home:alt-ch-client | | | | | + +------------------------+-------+-------+------------+-----------+ + | ietf-dots-call- | 32774 | 4 | IESG | RFC 9066 | + | home:alt-ch-client- | | | | | + | record | | | | | + +------------------------+-------+-------+------------+-----------+ + | ietf-dots-call-home: | 32775 | 0 | IESG | RFC 9066 | + | ttl | | | | | + +------------------------+-------+-------+------------+-----------+ + + Table 2: Assigned DOTS Signal Channel CBOR Key Values + +7.2. New DOTS Conflict Cause + + Per this document, IANA has assigned a new code from the "DOTS Signal + Channel Conflict Cause Codes" registry [Cause]. + + +====+=====================================+=============+==========+ + |Code| Label |Description |Reference | + +====+=====================================+=============+==========+ + |4 | request-rejected-legitimate-traffic |Mitigation |RFC 9066 | + | | |request | | + | | |rejected. | | + | | |This code is | | + | | |returned by | | + | | |the DOTS | | + | | |server to | | + | | |indicate the | | + | | |attack | | + | | |traffic has | | + | | |been | | + | | |classified as| | + | | |legitimate | | + | | |traffic. | | + +----+-------------------------------------+-------------+----------+ + + Table 3: Assigned DOTS Signal Channel Conflict Cause Code + + +7.3. DOTS Signal Call Home YANG Module + + Per this document, IANA has registered the following URI in the "ns" + subregistry within the "IETF XML Registry" [RFC3688]: + + URI: urn:ietf:params:xml:ns:yang:ietf-dots-call-home + Registrant Contact: The IETF. + XML: N/A; the requested URI is an XML namespace. + + Per this document, IANA has registered the following YANG module in + the "YANG Module Names" subregistry [RFC6020] within the "YANG + Parameters" registry: + + name: ietf-dots-call-home + namespace: urn:ietf:params:xml:ns:yang:ietf-dots-call-home + maintained by IANA: N + prefix: dots-call-home + reference: RFC 9066 + +8. Security Considerations + + This document deviates from classic DOTS signal channel usage by + having the DOTS server initiate the (D)TLS connection. Security + considerations related to the DOTS signal channel discussed in + Section 11 of [RFC9132] and (D)TLS early data discussed in Section 7 + of [RFC9132] MUST be considered. DOTS agents MUST authenticate each + other using (D)TLS before a DOTS signal channel session is considered + valid. + + The Call Home function enables a Call Home DOTS server to be + reachable by only the intended Call Home DOTS client. Appropriate + filters (e.g., access control lists) can be installed on the Call + Home DOTS server and network between the Call Home DOTS agents so + that only communications from a trusted Call Home DOTS client to the + Call Home DOTS server are allowed. These filters can be + automatically installed by a Call Home DOTS server based on the + configured or discovered peer Call Home DOTS client(s). + + An attacker may launch a DoS attack on the DOTS client by having it + perform computationally expensive operations before deducing that the + attacker doesn't possess a valid key. For instance, in TLS 1.3 + [RFC8446], the ServerHello message contains a key share value based + on an expensive asymmetric key operation for key establishment. + Common precautions mitigating DoS attacks are recommended, such as + temporarily adding the source address to a drop-list after a set + number of unsuccessful authentication attempts. + + The DOTS signal Call Home channel can be misused by a misbehaving + Call Home DOTS client by arbitrarily signaling legitimate traffic as + being attack traffic or falsifying mitigation signals so that some + sources are disconnected or some traffic is rate-limited. Such + misbehaving Call Home DOTS clients may include sources identified by + IP addresses that are used for internal use only (that is, these + addresses are not visible outside a Call Home DOTS server domain). + Absent explicit policy (e.g., the Call Home DOTS client and server + are managed by the same administrative entity), such requests should + be discarded by the Call Home DOTS server. More generally, Call Home + DOTS servers should not blindly trust mitigation requests from Call + Home DOTS clients. For example, Call Home DOTS servers could use the + attack flow information contained in a mitigation request to enable a + full-fledged packet inspection function to inspect all the traffic + from the compromised device to the target. They could also redirect + the traffic from the potentially compromised device to the target + towards a DDoS mitigation system that can scrub the suspicious + traffic without blindly blocking all traffic from the indicated + attack source to the target. Call Home DOTS servers can also seek + the consent of the DOTS server domain administrator to block the + traffic from the potentially compromised device to the target (see + Section 5.3.1). The means to seek consent are implementation + specific. + + Call Home DOTS agents may interact with on-path address sharing + functions to retrieve an internal IP address / external IP address + mapping (Section 5.3.2) identifying an attack source. Blocking + access or manipulating the mapping information will complicate DDoS + attack mitigation close to an attack source. Additional security + considerations are specific to the actual mechanism used to access + that mapping (refer, e.g., to Section 4 of [RFC8512] or Section 4 of + [RFC8513]). + + This document augments YANG data structures that are meant to be used + as an abstract representation of DOTS signal channel Call Home + messages. As such, the "ietf-dots-call-home" module does not + introduce any new vulnerabilities beyond those specified above and in + [RFC9132]. + +9. Privacy Considerations + + The considerations discussed in [RFC6973] were taken into account to + assess whether the DOTS Call Home introduces privacy threats. + + Concretely, the protocol does not leak any new information that can + be used to ease surveillance. In particular, the Call Home DOTS + server is not required to share information that is local to its + network (e.g., internal identifiers of an attack source) with the + Call Home DOTS client. Also, the recommended data to be included in + Call Home DOTS messages is a subset of the Layer 3 / Layer 4 + information that can be learned from the overall traffic flows that + exit the Call Home DOTS server domain. Furthermore, Call Home DOTS + clients do not publicly reveal attack identification information; + that information is encrypted and only shared with an authorized + entity in the domain to which the IP address/prefix is assigned, from + which an attack was issued. + + The DOTS Call Home does not preclude the validation of mitigation + requests received from a Call Home DOTS client. For example, a + security service running on the CPE may require an administrator's + consent before the CPE acts upon the mitigation request indicated by + the Call Home DOTS client. How the consent is obtained is out of + scope of this document. + + Note that a Call Home DOTS server can seek an administrator's + consent, validate the request by inspecting the relevant traffic for + attack signatures, or proceed with both courses of action. + + The DOTS Call Home is only advisory in nature. Concretely, the DOTS + Call Home does not impose any action to be enforced within the + network hosting an attack source; it is up to the Call Home DOTS + server (and/or network administrator) to decide whether and which + actions are required. + + Moreover, the DOTS Call Home avoids misattribution by appropriately + identifying the network to which a suspect attack source belongs + (e.g., address sharing issues discussed in Section 5.3.1). + + Triggers to send a DOTS mitigation request to a Call Home DOTS server + are deployment specific. For example, a Call Home DOTS client may + rely on the output of some DDoS detection systems (flow exports or + similar functions) deployed within the DOTS client domain to detect + potential outbound DDoS attacks or may rely on abuse claims received + from remote victim networks. These systems may be misused to track + users and infer their activities. Such misuses are not required to + achieve the functionality defined in this document (that is, protect + the Internet and avoid altering the IP reputation of source + networks). It is out of the scope to identify privacy threats + specific to given attack detection technology. The reader may refer, + for example, to Section 11.8 of [RFC7011]. + +10. References + +10.1. Normative References + + [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, + RFC 792, DOI 10.17487/RFC0792, September 1981, + <https://www.rfc-editor.org/info/rfc792>. + + [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>. + + [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, + DOI 10.17487/RFC3688, January 2004, + <https://www.rfc-editor.org/info/rfc3688>. + + [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet + Control Message Protocol (ICMPv6) for the Internet + Protocol Version 6 (IPv6) Specification", STD 89, + RFC 4443, DOI 10.17487/RFC4443, March 2006, + <https://www.rfc-editor.org/info/rfc4443>. + + [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for + the Network Configuration Protocol (NETCONF)", RFC 6020, + DOI 10.17487/RFC6020, October 2010, + <https://www.rfc-editor.org/info/rfc6020>. + + [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. + Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, + DOI 10.17487/RFC6052, October 2010, + <https://www.rfc-editor.org/info/rfc6052>. + + [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful + NAT64: Network Address and Protocol Translation from IPv6 + Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, + April 2011, <https://www.rfc-editor.org/info/rfc6146>. + + [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer + Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, + January 2012, <https://www.rfc-editor.org/info/rfc6347>. + + [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", + RFC 6991, DOI 10.17487/RFC6991, July 2013, + <https://www.rfc-editor.org/info/rfc6991>. + + [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>. + + [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol + Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, + <https://www.rfc-editor.org/info/rfc8446>. + + [RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data + Structure Extensions", RFC 8791, DOI 10.17487/RFC8791, + June 2020, <https://www.rfc-editor.org/info/rfc8791>. + + [RFC9132] Boucadair, M., Ed., Shallow, J., and T. Reddy.K, + "Distributed Denial-of-Service Open Threat Signaling + (DOTS) Signal Channel Specification", RFC 9132, + DOI 10.17487/RFC9132, September 2021, + <https://www.rfc-editor.org/info/rfc9132>. + +10.2. Informative References + + [Cause] IANA, "DOTS Signal Channel Conflict Cause Codes", + <https://www.iana.org/assignments/dots/>. + + [DOTS-MULTIHOMING] + Boucadair, M., Reddy, T., and W. Pan, "Multi-homing + Deployment Considerations for Distributed-Denial-of- + Service Open Threat Signaling (DOTS)", Work in Progress, + Internet-Draft, draft-ietf-dots-multihoming-09, 2 December + 2021, <https://datatracker.ietf.org/doc/html/draft-ietf- + dots-multihoming-09>. + + [DTLS13] Rescorla, E., Tschofenig, H., and N. Modadugu, "The + Datagram Transport Layer Security (DTLS) Protocol Version + 1.3", Work in Progress, Internet-Draft, draft-ietf-tls- + dtls13-43, 30 April 2021, + <https://datatracker.ietf.org/doc/html/draft-ietf-tls- + dtls13-43>. + + [I2NSF-TERMS] + Hares, S., Strassner, J., Lopez, D. R., Xia, L., and H. + Birkholz, "Interface to Network Security Functions (I2NSF) + Terminology", Work in Progress, Internet-Draft, draft- + ietf-i2nsf-terminology-08, 5 July 2019, + <https://datatracker.ietf.org/doc/html/draft-ietf-i2nsf- + terminology-08>. + + [Key-Map] IANA, "DOTS Signal Channel CBOR Key Values", + <https://www.iana.org/assignments/dots/>. + + [RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address + Translator (NAT) Terminology and Considerations", + RFC 2663, DOI 10.17487/RFC2663, August 1999, + <https://www.rfc-editor.org/info/rfc2663>. + + [RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram + Congestion Control Protocol (DCCP)", RFC 4340, + DOI 10.17487/RFC4340, March 2006, + <https://www.rfc-editor.org/info/rfc4340>. + + [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing + (CIDR): The Internet Address Assignment and Aggregation + Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August + 2006, <https://www.rfc-editor.org/info/rfc4632>. + + [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet + Denial-of-Service Considerations", RFC 4732, + DOI 10.17487/RFC4732, December 2006, + <https://www.rfc-editor.org/info/rfc4732>. + + [RFC4949] Shirey, R., "Internet Security Glossary, Version 2", + FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007, + <https://www.rfc-editor.org/info/rfc4949>. + + [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", + RFC 4960, DOI 10.17487/RFC4960, September 2007, + <https://www.rfc-editor.org/info/rfc4960>. + + [RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and + Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October + 2011, <https://www.rfc-editor.org/info/rfc6398>. + + [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., + Morris, J., Hansen, M., and R. Smith, "Privacy + Considerations for Internet Protocols", RFC 6973, + DOI 10.17487/RFC6973, July 2013, + <https://www.rfc-editor.org/info/rfc6973>. + + [RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken, + "Specification of the IP Flow Information Export (IPFIX) + Protocol for the Exchange of Flow Information", STD 77, + RFC 7011, DOI 10.17487/RFC7011, September 2013, + <https://www.rfc-editor.org/info/rfc7011>. + + [RFC7596] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I. + Farrer, "Lightweight 4over6: An Extension to the Dual- + Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596, + July 2015, <https://www.rfc-editor.org/info/rfc7596>. + + [RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S., + Murakami, T., and T. Taylor, Ed., "Mapping of Address and + Port with Encapsulation (MAP-E)", RFC 7597, + DOI 10.17487/RFC7597, July 2015, + <https://www.rfc-editor.org/info/rfc7597>. + + [RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home", + RFC 8071, DOI 10.17487/RFC8071, February 2017, + <https://www.rfc-editor.org/info/rfc8071>. + + [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", + BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, + <https://www.rfc-editor.org/info/rfc8340>. + + [RFC8512] Boucadair, M., Ed., Sivakumar, S., Jacquenet, C., + Vinapamula, S., and Q. Wu, "A YANG Module for Network + Address Translation (NAT) and Network Prefix Translation + (NPT)", RFC 8512, DOI 10.17487/RFC8512, January 2019, + <https://www.rfc-editor.org/info/rfc8512>. + + [RFC8513] Boucadair, M., Jacquenet, C., and S. Sivakumar, "A YANG + Data Model for Dual-Stack Lite (DS-Lite)", RFC 8513, + DOI 10.17487/RFC8513, January 2019, + <https://www.rfc-editor.org/info/rfc8513>. + + [RFC8517] Dolson, D., Ed., Snellman, J., Boucadair, M., Ed., and C. + Jacquenet, "An Inventory of Transport-Centric Functions + Provided by Middleboxes: An Operator Perspective", + RFC 8517, DOI 10.17487/RFC8517, February 2019, + <https://www.rfc-editor.org/info/rfc8517>. + + [RFC8576] Garcia-Morchon, O., Kumar, S., and M. Sethi, "Internet of + Things (IoT) Security: State of the Art and Challenges", + RFC 8576, DOI 10.17487/RFC8576, April 2019, + <https://www.rfc-editor.org/info/rfc8576>. + + [RFC8612] Mortensen, A., Reddy, T., and R. Moskowitz, "DDoS Open + Threat Signaling (DOTS) Requirements", RFC 8612, + DOI 10.17487/RFC8612, May 2019, + <https://www.rfc-editor.org/info/rfc8612>. + + [RFC8811] Mortensen, A., Ed., Reddy.K, T., Ed., Andreasen, F., + Teague, N., and R. Compton, "DDoS Open Threat Signaling + (DOTS) Architecture", RFC 8811, DOI 10.17487/RFC8811, + August 2020, <https://www.rfc-editor.org/info/rfc8811>. + + [RFC8903] Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia, + L., and K. Nishizuka, "Use Cases for DDoS Open Threat + Signaling", RFC 8903, DOI 10.17487/RFC8903, May 2021, + <https://www.rfc-editor.org/info/rfc8903>. + + [RFC8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M. + Bacher, "Dissemination of Flow Specification Rules", + RFC 8955, DOI 10.17487/RFC8955, December 2020, + <https://www.rfc-editor.org/info/rfc8955>. + + [RFC8956] Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed., + "Dissemination of Flow Specification Rules for IPv6", + RFC 8956, DOI 10.17487/RFC8956, December 2020, + <https://www.rfc-editor.org/info/rfc8956>. + + [RFC8973] Boucadair, M. and T. Reddy.K, "DDoS Open Threat Signaling + (DOTS) Agent Discovery", RFC 8973, DOI 10.17487/RFC8973, + January 2021, <https://www.rfc-editor.org/info/rfc8973>. + + [RS] RSnake, "Slowloris HTTP DoS", + <https://web.archive.org/web/20150315054838/ + http://ha.ckers.org/slowloris/>. + + [Sec-by-design] + UK Department for Digital, Culture, Media & Sport, "Secure + by Design: Improving the cyber security of consumer + Internet of Things Report", March 2018, + <https://www.gov.uk/government/publications/secure-by- + design-report>. + +Appendix A. Some Home Network Issues + + Internet of Things (IoT) devices are becoming more and more + prevalent, in particular in home networks. With compute and memory + becoming cheaper and cheaper, various types of IoT devices become + available in the consumer market at affordable prices. But on the + downside, there is a corresponding threat since most of these IoT + devices are bought off-the-shelf and most manufacturers haven't + considered security in the product design (e.g., [Sec-by-design]). + IoT devices deployed in home networks can be easily compromised, they + often do not have an easy mechanism to upgrade, and even when + upgradable, IoT manufacturers may cease manufacture and/or + discontinue patching vulnerabilities on IoT devices (Sections 5.4 and + 5.5 of [RFC8576]). These vulnerable and compromised devices will + continue to be used for a long period of time in the home, and the + end-user does not know that IoT devices in his/her home are + compromised. The compromised IoT devices are typically used for + launching DDoS attacks (Section 3 of [RFC8576]) on victims while the + owner/administrator of the home network is not aware about such + misbehaviors. Similar to other DDoS attacks, the victim in this + attack can be an application server, a host, a router, a firewall, or + an entire network. Such misbehaviors can cause collateral damage + that will affect end users, and can also harm the reputation of an + Internet Service Provider (ISP) for being a source of attack traffic. + + Nowadays, network devices in a home network can offer network + security functions (e.g., firewall [RFC4949] or Intrusion Protection + System (IPS) service [I2NSF-TERMS] on a home router) to protect the + devices connected to the home network from both external and internal + attacks. It is natural to seek to provide DDoS defense in these + devices as well, and over the years several techniques have been + identified to detect DDoS attacks; some of these techniques can be + enabled on home network devices but most of them are used within the + ISP's network. + + Some of the DDoS attacks like spoofed RST or FIN packets, Slowloris + [RS], and Transport Layer Security (TLS) renegotiation are difficult + to detect on a home network device without adversely affecting its + performance. The reason is that typically home devices such as home + routers have fast path to boost the throughput. For every new TCP/ + UDP flow, only the first few packets are punted through the slow + path. Hence, it is not possible to detect various DDoS attacks in + the slow path, since the attack payload is sent to the target server + after the flow is switched to fast path. The reader may refer to + Section 2 of [RFC6398] for a brief definition of slow and fast paths. + + Deep Packet Inspection (DPI) of all the packets of a flow would be + able to detect some of the attacks. However, a full-fledged DPI to + detect these type of DDoS attacks is functionally or operationally + not possible for all the devices attached to the home network because + of the memory and CPU limitations of the home routers. Furthermore, + for certain DDoS attacks the logic needed to distinguish legitimate + traffic from attack traffic on a per-packet basis is complex. This + complexity is because that the packet itself may look "legitimate" + and no attack signature can be identified. The anomaly can be + identified only after detailed statistical analysis. In addition, + network security services in home networks may not be able to detect + all types of DDoS attacks using DPI. ISPs offering DDoS mitigation + services have a DDoS detection capability that relies upon anomaly + detection to identify zero day DDoS attacks and to detect DDoS + attacks that cannot be detected using signatures and rate-limit + techniques. + + ISPs can detect some DDoS attacks originating from a home network + (e.g., Section 2.6 of [RFC8517]), but the ISP usually does not have a + mechanism to detect which device in the home network is generating + the DDoS attack traffic. The primary reason for this is that devices + in an IPv4 home network are typically behind a Network Address + Translation (NAT) border [RFC2663]. Even in case of an IPv6 home + network, although the ISP can identify the infected device in the + home network launching the DDoS traffic by tracking its unique IPv6 + address, the infected device can easily change its IPv6 address to + evade remediation. A security function on the local home network is + better positioned to track the compromised device across IPv6 address + (and potentially even MAC address) changes and thus ensure that + remediation remains in place across such events. + +Appendix B. Disambiguating Base DOTS Signal vs. DOTS Call Home + + With the DOTS signal channel Call Home, there is a chance that two + DOTS agents can simultaneously establish two DOTS signal channels + with different directions (base DOTS signal channel and DOTS signal + channel Call Home). Here is one example drawn from the home network. + Nevertheless, the outcome of the discussion is not specific to these + networks, but applies to any DOTS Call Home scenario. + + In the Call Home scenario, the Call Home DOTS server in, for example, + the home network can mitigate the DDoS attacks launched by the + compromised device in its domain by receiving the mitigation request + sent by the Call Home DOTS client in the ISP environment. In + addition, the DOTS client in the home network can initiate a + mitigation request to the DOTS server in the ISP environment to ask + for help when the home network is under a DDoS attack. Such Call + Home DOTS server and DOTS client in the home network can co-locate in + the same home network element (e.g., the Customer Premises + Equipment). In this case, with the same peer at the same time the + home network element will have the base DOTS signal channel defined + in [RFC9132] and the DOTS signal channel Call Home defined in this + specification. Thus, these two signal channels need to be + distinguished when they are both supported. Two approaches have been + considered for distinguishing the two DOTS signal channels, but only + the one that using the dedicated port number has been chosen as the + best choice. + + By using a dedicated port number for each, these two signal channels + can be separated unambiguously and easily. For example, the CPE uses + the port number 4646 allocated in [RFC9132] to initiate the basic + signal channel to the ISP when it acts as the DOTS client, and uses + another port number to initiate the signal channel Call Home. Based + on the different port numbers, the ISP can directly decide which kind + of procedures should follow immediately after it receives the DOTS + messages. This approach just requires two (D)TLS sessions to be + established respectively for the basic signal channel and signal + channel Call Home. + + The other approach is signaling the role of each DOTS agent (e.g., by + using the DOTS data channel as depicted in Figure 14). For example, + the DOTS agent in the home network first initiates a DOTS data + channel to the peer DOTS agent in the ISP environment, at this time + the DOTS agent in the home network is the DOTS client and the peer + DOTS agent in the ISP environment is the DOTS server. After that, + the DOTS agent in the home network retrieves the DOTS Call Home + capability of the peer DOTS agent. If the peer supports the DOTS + Call Home, the DOTS agent needs to subscribe to the peer to use this + extension. Then, the reversal of DOTS role can be recognized as done + by both DOTS agents. When the DOTS agent in the ISP environment, + which now is the DOTS client, wants to filter the attackers' traffic, + it requests the DOTS agent in the home network, which now is the DOTS + server, for help. + + augment /ietf-data:dots-data/ietf-data:capabilities: + +--ro call-home-support? boolean + augment /ietf-data:dots-data/ietf-data:dots-client: + +--rw call-home-enable? boolean + + Figure 14: Example of DOTS Data Channel Augmentation + + Signaling the role will complicate the DOTS protocols, and this + complexity is not required in context where the DOTS Call Home is not + required or only when the DOTS Call Home is needed. Besides, the + DOTS data channel may not work during attack time. Even if changing + the above example from using the DOTS data channel to the DOTS signal + channel, the more procedures will still reduce the efficiency. Using + the dedicated port number is much easier and more concise compared to + the second approach, and its cost that establishing two (D)TLS + sessions is much less. So, using a dedicated port number for the + DOTS Call Home is recommended in this specification. The dedicated + port number can be configured locally or discovered using means such + as [RFC8973]. + +Acknowledgements + + Thanks to Wei Pei, Xia Liang, Roman Danyliw, Dan Wing, Toema + Gavrichenkov, Daniel Migault, Sean Turner, and Valery Smyslov for the + comments. + + Benjamin Kaduk's AD review is valuable. Many thanks to him for the + detailed review. + + Thanks to Radia Perlman and David Schinazi for the directorate + reviews. + + Thanks to Ebben Aries for the YANG Doctors review. + + Thanks to Éric Vyncke, Roman Danyliw, Barry Leiba, Robert Wilton, and + Erik Kline for the IESG review. + +Contributors + + The following individuals have contributed to this document: + + Joshi Harsha + McAfee, Inc. + Embassy Golf Link Business Park + Bangalore 560071 + Karnataka + India + + Email: harsha_joshi@mcafee.com + + + Wei Pan + Huawei Technologies + China + + Email: william.panwei@huawei.com + + +Authors' Addresses + + Tirumaleswar Reddy.K + Akamai + Embassy Golf Link Business Park + Bangalore 560071 + Karnataka + India + + Email: kondtir@gmail.com + + + Mohamed Boucadair (editor) + Orange + 35000 Rennes + France + + Email: mohamed.boucadair@orange.com + + + Jon Shallow + United Kingdom + + Email: supjps-ietf@jpshallow.com |