| DOTS | T. Reddy |
| Internet-Draft | McAfee |
| Intended status: Standards Track | M. Boucadair |
| Expires: September 3, 2020 | Orange |
| J. Shallow | |
| March 2, 2020 |
Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Call Home
draft-ietf-dots-signal-call-home-08
This document specifies the DOTS signal channel Call Home, which enables a DOTS server to initiate a secure connection to a DOTS client, and to receive the attack traffic information from the DOTS client. The DOTS server in turn uses the attack traffic information to identify the compromised devices launching the outgoing DDoS attack and takes appropriate mitigation action(s).
The DOTS signal channel Call Home is not specific to the home networks; the solution targets any deployment which requires to block DDoS attack traffic closer to the source(s) of a DDoS attack.
Please update these statements within the document with the RFC number to be assigned to this document:
Please update this statement with the RFC number to be assigned to the following documents:
Please update TBD statements with the assignment made by IANA to DOTS Signal Channel Call Home.
Also, 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 September 3, 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 DOTS signal channel protocol [I-D.ietf-dots-signal-channel] 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 [I-D.ietf-dots-use-cases].
Internet of Things (IoT) devices are becoming more and more prevalent in home networks, in particular. 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, the main threat being most of these IoT devices are bought off-the-shelf and most manufacturers haven't considered security in the product design (e.g., [Sec]). IoT devices deployed in home networks can be easily compromised, they do not have an easy mechanism to upgrade, and IoT manufactures 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 will have a collateral damage that affects end users and the reputation of an Internet Service Provider (ISP).
Nowadays, network devices in a home network offer network security (e.g., firewall [RFC4949] or Intrusion Protection System (IPS) service [I-D.ietf-i2nsf-terminology] on a home router) to protect the devices connected to the home network from both external and internal attacks. 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. 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 [RFC5575][I-D.ietf-idr-flow-spec-v6]) from a downstream service provider to filter, block, or rate-limit DDoS attack traffic originating from the ISP's subscribers to a downstream target.
Some of the DDoS attacks like spoofed RST or FIN packets, Slowloris, and Transport Layer Security (TLS) re-negotiation are difficult to detect on a home network device without adversely affecting its performance. The reason is 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 owing to the memory and CPU limitations of the home routers. Furthermore, for certain DDoS attacks the ability to distinguish legitimate traffic from attack traffic on a per packet basis is complex. This complexity is due to that the packet itself may look "legitimate" and no attack signature can be identified. The anomaly can be identified only after detailed statistical analysis.
ISPs can detect some DDoS attacks originating from a home network (e.g., Section 2.6 of [RFC8517]), but the ISP does not have a mechanism to detect which device in the home network is generating the DDoS attack traffic. The primary reason being 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.
Existing approaches are still suffering from misused access network resources by abusing devices; the support of means for blocking such attacks close to the sources are missing. In particular, the DOTS signal protocol does not discuss cooperative DDoS mitigation between the network hosting an attack source and the ISP to the suppress the outbound DDoS attack traffic originating from that network.
This specification addresses the problems discussed in Section 1.1 and presents an extension to the DOTS signal channel: DOTS signal channel Call Home.
'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. 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. More details are provided in Section 3.
DOTS agents involved in the DOTS Call Home 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 1).
A high-level DOTS Call Home functional architecture is shown in Figure 1. Attack source(s) are within the DOTS server domain.
Scope
+.-.-.-.-.-.-.-.-.-.-.-.+
+---------------+ : +-------------+ :
| Alert/DMS/ | ~~~:~~~ | Call Home | :
| Peer DMS/... | : | DOTS client | :
+---------------+ : +------+------+ :
: | :
: | :
: | :
+---------------+ : +------+------+ :
| Attack | ~~~:~~~ | Call Home | :
| Source(s) | : | DOTS server | :
+---------------+ : +-------------+ :
+.-.-.-.-.-.-.-.-.-.-.-.+
Figure 1: Basic DOTS Signal Channel Call Home Functional Architecture
A 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, 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. Unlike classic DOTS deployments [I-D.ietf-dots-use-cases], such DOTS server maintains a single DOTS signal channel session for each DOTS-capable upstream provisioning domain [I-D.ietf-dots-multihoming].
For instance, the Call Home DOTS server in the home network initiates the signal channel Call Home in 'idle' time and then 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.
Other motivations for introducing the Call Home function are discussed in Section 1.1 of [RFC8071].
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., [I-D.ietf-dots-server-discovery]). 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 1.3.
The aforementioned problems may be encountered in other deployments than those discussed in Section 1.1 (e.g., data centers, enterprise networks). 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.
An instantiation of the Call Home functional architecture is depicted in Figure 2.
+-------------+
|Attack Target|
+-----+-------+
| /\ Target Network
......................|.||....................
.--------+-||-------.
( || )-.
.' || '
( Internet || )
( || -'
'-( || )
'------+-||---------'
......................|.||.....................
.--------+-||-------. Network
( || )-. Provider
.' Call Home || ' (DMS)
( DOTS client || )
( || -'
'-( || )
'------+-||---------'
......................|.||.......................
.--------+-||-------. Source Network
( || )-.
.' Call Home || '
( DOTS server || Outbound )
( || DDoS -'
'-( || Attack )
'------+-||---------'
| ||
+-----+-++----+
|Attack Source|
+-------------+
Figure 2: DOTS Signal Channel Call Home Reference Architecture
It is out of the scope of this document to identify an exhaustive list of such deployments.
The DOTS signal channel Call Home does not require nor preclude the activation of the base DOTS signal channel [I-D.ietf-dots-signal-channel]. 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 3 (Same DMS provider) or Figure 4 (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 3: Activation of Base DOTS Signal Channel and Call Home (Same DMS Provider)
Note that a DMS provider may not be on the default forwarding path of an inbound DDoS attack traffic targeting a network (e.g., Network #B in Figure 4). 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 4: Activation of Base DOTS Signal Channel and Call Home (Distinct DMS Providers)
Figures 5 and 6 depict examples where the same node embeds both base DOTS and DOTS Call Home 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 5) 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 6) .
Whether the same or distinct nodes are used to host base DOTS and DOTS Call Home 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 5: An Example of the Same Node Embedding both 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 6: Another Example where the Same Node Embeds both a DOTS Client and a Call Home DOTS Server
Appendix A elaborates on the considerations to unambiguously distinguish DOTS messages which belong to each of these channels.
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].
'Base DOTS signal channel' refers to [I-D.ietf-dots-signal-channel].
The meaning of the symbols in YANG tree diagrams is defined in [RFC8340].
(D)TLS is used for statements that apply to both Transport Layer Security (TLS) [RFC8446] and Datagram Transport Layer Security (DTLS) [RFC6347]. Specific terms are used for any statement that applies to either protocol alone.
The DOTS signal channel Call Home preserves all but one of the DOTS client/server roles in the DOTS protocol stack, as compared to DOTS client-initiated DOTS signal channel protocol [I-D.ietf-dots-signal-channel]. 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 (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 server. However, when calling home, the DOTS server initially assumes the role of the (D)TLS client, but the network element's role as a DOTS server remains the same. Furthermore, existing certificate chains and mutual authentication mechanisms between the DOTS agents are unaffected by the Call Home function. This Call Home function enables the DOTS server co-located with a network element (possibly behind NATs and firewalls) reachable by only the intended Call Home DOTS client and hence the Call Home DOTS server cannot be subjected to these DDoS attacks.
Figure 7 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 7: DOTS Signal Channel Call Home Sequence Diagram
The DOTS signal channel Call Home procedure is as follows:
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 [I-D.ietf-dots-signal-channel]). The Call Home DOTS server adjusts the 'heartbeat-interval' to accommodate binding timers used by on-path NATs and firewalls. Heartbeats will be then 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 missing heartbeats allowed threshold ('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 resume the (D)TLS session.
A Call Home DOTS server MUST NOT support the Redirected Signaling mechanism as specified in Section 4.6 of [I-D.ietf-dots-signal-channel] (i.e., a 5.03 response that conveys an alternate DOTS server's FQDN or alternate DOTS server's IP address(es)). A Call Home DOTS client MUST silently discard such 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 new Call Home DOTS client FQDN or IP address in the body of the PUT similar to what is described in Section 4.6 of [I-D.ietf-dots-signal-channel]. Furthermore, a new clause called 'ttl" is defined to return the Time to live (TTL) of the alternate Call Home DOTS client.
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 [I-D.ietf-dots-signal-channel]. If the Call Home DOTS server cannot service the PUT request, the response is rejected with a 4.00 (bad Request).
Figure 8 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 8: Example of a PUT Request for Redirected Signaling
This specification extends the mitigation request defined in Section 4.4.1 of [I-D.ietf-dots-signal-channel] to convey the attack source information (e.g., source prefixes, source port numbers). The DOTS client conveys the following new parameters in the CBOR body of the mitigation request:
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 7). 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. Note that 'target-prefix' becomes a mandatory attribute in the mitigation request signaling the attack information because 'target-uri' and 'target-fqdn' are optional attributes and 'alias-name' will not be conveyed in a mitigation request.
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'. The Call Home DOTS client may not include such information if 'source-prefix' conveys an IPv6 address/prefix. Address sharing implications on the setting of source information ('source-prefix', 'source-port-range') are discussed in Section 3.3.2.
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).
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::/128"
],
"lifetime": 3600
}
]
}
}
Figure 9: An Example of Mitigation Request Issued by a Call Home DOTS Client
An example of a mitigation request sent by a Call Home DOTS client is shown in Figure 9.
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 routeable 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 [I-D.ietf-dots-signal-channel].
The 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 the attack traffic is blocked, the Call Home DOTS server informs the Call Home DOTS client that the attack is being 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, and 4.09 (Conflict) is returned to the Call Home DOTS client. The conflict-clause (defined in Section 4.4.1 of [I-D.ietf-dots-signal-channel]) indicates the cause of the conflict. The following new value is defined:
Once the request is validated by the Call Home DOTS server, appropriate actions are enforced to block the attack traffic within the source network. The Call Home DOTS client is informed about the progress of the attack mitigation following the rules in [I-D.ietf-dots-signal-channel]. 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.
The DOTS agents follow the same procedures specified in [I-D.ietf-dots-signal-channel] for managing a mitigation request.
If a Carrier Grade NAT (CGN, including NAT64) is located between the DOTS client domain and DOTS server domain, communicating an external IP address in a mitigation request 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 (see Figure 10). The Call Home DOTS server is only aware of the internal IP addresses/prefixes bound to its domain. Thus, the Call Home DOTS client MUST NOT include the external IP address and/or port number identifying the suspect attack source, 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 [RFC8512] or [RFC8513], to retrieve the internal IP address and port number which are mapped to an external IP address and port number.
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 10: Example of a CGN between DOTS Domains
If a MAP Border Relay [RFC7597] or 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 11 and 12), 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. Doing so allows to isolate the suspicious device while avoiding to disturb 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 11: 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 12: Example of a Call Home DOTS Server and a NAT Embedded in a CPE
module: ietf-dots-call-home
augment /ietf-signal:dots-signal/ietf-signal:message-type
/ietf-signal:mitigation-scope/ietf-signal:scope:
+--rw source-prefix* inet:ip-prefix {source-signaling}?
+--rw source-port-range* [lower-port] {source-signaling}?
| +--rw lower-port inet:port-number
| +--rw upper-port? inet:port-number
+--rw source-icmp-type-range*
| [lower-type] {source-signaling}?
+--rw lower-type uint8
+--rw upper-type? uint8
augment /ietf-signal:dots-signal/ietf-signal:message-type
/ietf-signal:redirected-signal:
+--rw alt-ch-client string {call-home}?
+--rw alt-ch-client-record* inet:ip-address {call-home}?
+--rw ttl uint32 {call-home}?
This document augments the "ietf-dots-signal-channel" DOTS signal YANG module defined in [I-D.ietf-dots-signal-channel] for signaling the attack traffic information. This document defines the YANG module "ietf-dots-call-home", which has the following tree structure:
The YANG/JSON mapping parameters to CBOR are listed in Table 1.
+--------------------+------------+------+---------------+--------+
| Parameter Name | YANG | CBOR | CBOR Major | JSON |
| | Type | Key | Type & | Type |
| | | | Information | |
+--------------------+------------+------+---------------+--------+
|ietf-dots-call-home:| leaf-list | | | |
| source-prefix | inet: | TBA1 | 4 array | Array |
| | ip-prefix | | 3 text string | String |
|ietf-dots-call-home:| | | | |
| source-port-range | list | TBA2 | 4 array | Array |
|ietf-dots-call-home:| | | | |
| source-icmp-type- | list | TBA3 | 4 array | Array |
| range | | | | |
|ietf-dots-call-home:| | | | |
| lower-type | uint8 | TBA4 | 0 unsigned | Number |
|ietf-dots-call-home:| | | | |
| upper-type | uint8 | TBA5 | 0 unsigned | Number |
|ietf-dots-call-home:| | | | |
| alt-ch-client | string | TBA6 | 3 text string | String |
|ietf-dots-call-home:| leaf-list | TBA7 | 4 array | Array |
| alt-ch-client- | inet: | | | |
| record | ip-address| | 3 text string | String |
|ietf-dots-call-home:| | | | |
| ttl | uint32 | TBA8 | 0 unsigned | Number |
+--------------------+------------+------+---------------+--------+
Table 1: YANG/JSON Mapping Parameters to CBOR
This module uses the common YANG types defined in [RFC6991].
<CODE BEGINS> file "ietf-dots-call-home@2019-09-06.yang"
module ietf-dots-call-home {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dots-call-home";
prefix call-home;
import ietf-inet-types {
prefix inet;
reference
"Section 4 of RFC 6991";
}
import ietf-dots-signal-channel {
prefix ietf-signal;
reference
"RFC YYYY: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal 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: Konda, Tirumaleswar Reddy
<mailto:TirumaleswarReddy_Konda@McAfee.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) 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 2019-09-06 {
description
"Initial revision.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel Call Home";
}
feature source-signaling {
description
"This feature means that source-related information
can be supplied in mitigation requests. This is
typically applicable for DOTS Call Home.";
}
feature call-home {
description
"This feature means that Call Home functionality
is supported.";
}
augment "/ietf-signal:dots-signal/ietf-signal:message-type/"
+ "ietf-signal:mitigation-scope/ietf-signal:scope" {
if-feature source-signaling;
description "Attacker source details.";
leaf-list source-prefix {
type inet:ip-prefix;
description
"IPv4 or IPv6 prefix identifying the attacker(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;
mandatory true;
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 lower port number.";
}
description
"Upper port number of the port range.";
}
}
list source-icmp-type-range {
key "lower-type";
description
"ICMP type range. When only lower-type is
present, it represents a single ICMP type.";
leaf lower-type {
type uint8;
mandatory true;
description
"Lower ICMP type of the ICMP type range.";
}
leaf upper-type {
type uint8;
must ". >= ../lower-type" {
error-message
"The upper ICMP type must be greater than
or equal to lower ICMP type.";
}
description
"Upper type of the ICMP type range.";
}
}
}
augment "/ietf-signal:dots-signal/ietf-signal:message-type/"
+ "ietf-signal:redirected-signal" {
if-feature call-home;
description
"The alternate Call Home DOTS client.";
leaf alt-ch-client {
type string;
description
"FQDN of an alternate Call Home DOTS client.";
}
leaf-list alt-ch-client-record {
type inet:ip-address;
description
"List of records for the alternate Call Home
DOTS client.";
}
leaf ttl {
type uint32;
units "seconds";
description
"The Time to live (TTL) of the alternate Call Home
DOTS client.";
}
}
}
<CODE ENDS>
IANA is requested to assign the port number TBD to the DOTS signal channel Call Home protocol for both UDP and TCP from the "Service Name and Transport Protocol Port Number Registry" available at: https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml.
Service Name: dots-call-home Port Number: TBD Transport Protocol(s): TCP/UDP Description: DOTS Signal Channel Call Home Assignee: IESG <iesg@ietf.org> Contact: IETF Chair <chair@ietf.org> Reference: RFC XXXX
The assignment of port number 4647 is strongly suggested (DOTS signal channel uses port number 4646).
This specification registers the following comprehension-optional parameters (Table 2) in the IANA "DOTS Signal Channel CBOR Key Values" registry established by [I-D.ietf-dots-signal-channel] and maintained at 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-call-home:| | | | |
| source-prefix | TBA1 | 4 | IESG | [RFCXXXX] |
|ietf-dots-call-home:| | | | |
| source-port-range | TBA2 | 4 | IESG | [RFCXXXX] |
|ietf-dots-call-home:| | | | |
| source-icmp-type- | TBA3 | 4 | IESG | [RFCXXXX] |
| range | | | | |
|ietf-dots-call-home:| | | | |
| lower-type | TBA4 | 0 | IESG | [RFCXXXX] |
|ietf-dots-call-home:| | | | |
| upper-type | TBA5 | 0 | IESG | [RFCXXXX] |
|ietf-dots-call-home:| | | | |
| alt-ch-client | TBA6 | 3 | IESG | [RFCXXXX] |
|ietf-dots-call-home:| | | | |
|alt-ch-client-record| TBA7 | 4 | IESG | [RFCXXXX] |
|ietf-dots-call-home:| | | | |
| ttl | TBA8 | 0 | IESG | [RFCXXXX] |
+--------------------+-------+-------+------------+---------------+
Table 2: Assigned DOTS Signal Channel CBOR Key Values
This document requests IANA to assign a new code from the "DOTS Signal Channel Conflict Cause Codes" registry established by [I-D.ietf-dots-signal-channel] and maintained at https://www.iana.org/assignments/dots/dots.xhtml#dots-signal-channel-conflict-cause-codes.
| Code | Label | Description | Reference |
|---|---|---|---|
| 4 (TBA9) | request-rejected-legitimate-traffic | Mitigation request rejected. This code is returned by the DOTS server to indicate the attack traffic has been classified as legitimate traffic. | [RFCXXXX] |
URI: urn:ietf:params:xml:ns:yang:ietf-dots-call-home
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
name: ietf-dots-call-home
namespace: urn:ietf:params:xml:ns:yang:ietf-dots-call-home
maintained by IANA: N
prefix: call-home
reference: RFC XXXX
This document requests IANA to register the following URI in the "ns" subregistry within the "IETF XML Registry" [RFC3688]: [RFC7950] within the "YANG Parameters" registry:
This document deviates from classic DOTS signal channel usage by having the DOTS server initiate the (D)TLS connection. DOTS signal channel related security considerations discussed in Section 10 of [I-D.ietf-dots-signal-channel] MUST be considered. DOTS agents MUST authenticate each other using (D)TLS before a DOTS signal channel session is considered valid.
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 blacklisting the source address after a set number of unsuccessful authentication attempts.
Call Home DOTS servers may not blindly trust mitigation requests from Call Home DOTS clients. For example, DOTS servers can use the attack flow information in a mitigation request to enable full-fledged packet inspection function to inspect all the traffic from the compromised device to the target or to re-direct the traffic from the compromised device to the target to a DDoS mitigation system to scrub the suspicious traffic. Call Home DOTS servers can also seek the consent of DOTS server domain administrator to block the traffic from the compromised device to the target (see Section 3.3.1).
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.
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 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 for an administrator's consent, validate the request by inspecting the traffic, or proceed with both.
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 to (e.g., address sharing issues discussed in Section 3.3.1).
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 deployed within the DOTS client domain to detect potential outbound DDoS attacks or on abuse claims received from remote victim networks. Such DDoS detection and mitigation techniques are not meant to track the activity of users, but to protect the Internet and avoid altering the IP reputation of the DOTS client domain.
The following individuals have contributed to this document:
Joshi Harsha McAfee, Inc. Embassy Golf Link Business Park Bangalore, Karnataka 560071 India Email: harsha_joshi@mcafee.com Wei Pan Huawei Technologies China Email: william.panwei@huawei.com
Thanks to Wei Pei, Xia Liang, Roman Danyliw, Dan Wing, Töma Gavrichenkov, Daniel Migault, and Valery Smyslov for the comments.
| [I-D.ietf-dots-signal-channel] | Reddy.K, T., Boucadair, M., Patil, P., Mortensen, A. and N. Teague, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification", Internet-Draft draft-ietf-dots-signal-channel-41, January 2020. |
| [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. |
| [RFC6347] | Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012. |
| [RFC6991] | Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013. |
| [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. |
| [RFC8446] | Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018. |
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 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 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 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 [I-D.ietf-dots-signal-channel] to initiate the basic signal channel to the ISP when it acts as the DOTS client, and uses the port number TBD 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). 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.
Signaling the role will complicate the DOTS protocol, 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 chosen in this specification.