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IETF RFC 9761
Last modified on Friday, April 18th, 2025
 Permanent link to RFC 9761
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Internet Engineering Task Force (IETF) T. Reddy.K
Request for Comments: 9761 Nokia
Category: Standards Track D. Wing
ISSN: 2070-1721 Citrix
B. Anderson
Cisco
April 2025
Manufacturer Usage Description (MUD) for TLS and DTLS Profiles for
Internet of Things (IoT) Devices
 Abstract
This memo extends the Manufacturer Usage Description (MUD)
specification to allow manufacturers to define TLS and DTLS profile
parameters. This allows a network security service to identify
unexpected (D)TLS usage, which can indicate the presence of
unauthorized software, malware, or security policy-violating traffic
on an endpoint.
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/RFC 9761.
Copyright Notice
Copyright (c) 2025 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. Overview of MUD (D)TLS Profiles for IoT devices
4. (D)TLS 1.3 Handshake
4.1. Full (D)TLS 1.3 Handshake Inspection
4.2. Encrypted DNS
5. (D)TLS Profile of an IoT device
5.1. Tree Structure of the (D)TLS Profile Extension to the ACL
YANG Module
5.2. The (D)TLS Profile Extension to the ACL YANG Module
5.3. IANA (D)TLS Profile YANG Module
5.4. MUD (D)TLS Profile Extension
6. Processing of the MUD (D)TLS Profile
7. MUD File Example
8. Software-Based ACLs and ACLs Within a (D)TLS 1.3 Proxy
9. Security Considerations
9.1. Challenges in Mimicking (D)TLS 1.2 Handshakes for IoT
Devices
9.2. Considerations for the "iana-tls-profile" Module
9.3. Considerations for the "ietf-acl-tls" Module
9.4. Considerations for the "ietf-mud-tls" Module
10. Privacy Considerations
11. IANA Considerations
11.1. (D)TLS Profile YANG Modules
11.2. Considerations for the iana-tls-profile Module
11.3. ACL TLS Version Registry
11.4. ACL DTLS Version Registry
11.5. ACL (D)TLS Parameters Registry
11.6. MUD Extensions Registry
12. References
12.1. Normative References
12.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
Encryption is necessary to enhance the privacy of end users using
Internet of Things (IoT) devices. TLS [RFC 8446] and DTLS [RFC 9147]
are the dominant protocols (counting all (D)TLS versions) that
provide encryption for IoT device traffic. Unfortunately, in
conjunction with IoT applications' rise of encryption, malware
authors are also using encryption that thwarts network-based
analysis, such as deep packet inspection (DPI). Thus, other
mechanisms are needed to help detect malware running on an IoT
device.
Malware often reuses certain libraries, and there are notable
differences in how malware uses encryption compared to software that
is not malware. Several common patterns in the use of (D)TLS by
malware include:
* Use of older and weaker cryptographic parameters.
* TLS server name indication (SNI) extension [RFC 6066] and server
certificates are composed of subjects with characteristics of a
domain generation algorithm (DGA) (e.g., "www.33mhwt2j.net").
* Higher use of self-signed certificates compared with typical
legitimate software using certificates from a certificate
authority (CA) trusted by the device.
* Discrepancies in the SNI TLS extension and the DNS names in the
SubjectAltName (SAN) X.509 extension in the server Certificate
message.
* Discrepancies in the key exchange algorithm and the client public
key length in comparison with legitimate flows. As a reminder,
the Client Key Exchange message has been removed from TLS 1.3.
* Lower diversity in extensions advertised by TLS clients compared
to legitimate clients.
* Using privacy enhancing technologies like Tor, Psiphon, Ultrasurf
(see [MALWARE-TLS]), and evasion techniques such as ClientHello
randomization.
* Using an alternative DNS server (via encrypted transport) to avoid
detection by malware DNS filtering services [MALWARE-DOH].
Specifically, malware may not use the Do53 or encrypted DNS server
provided by the local network (DHCP, Discovery of Network-
designated Resolvers (DNR) [RFC 9463], or Discovery of Designated
Resolvers (DDR) [RFC 9462]).
If (D)TLS profile parameters are defined, the following functions
that have a positive impact on the local network security are
possible:
* Permit intended DTLS or TLS use, and block malicious DTLS or TLS
use. This is superior to the Access Control Lists (ACLs) of
Layers 3 and 4 in "Manufacturer Usage Description Specification"
[RFC 8520], which are not suitable for broad communication
patterns. The goal of this document is to enhance and complement
the existing MUD specifications rather than undermine them.
* Ensure TLS certificates are valid. Several TLS deployments have
been vulnerable to active Man-In-The-Middle (MITM) attacks because
of the lack of certificate validation or vulnerability in the
certificate validation function (see [CRYPTO-VULNERABILITY]). By
observing (D)TLS profile parameters, a network element can detect
when the TLS SNI mismatches the SubjectAltName and when the
server's certificate is invalid. In (D)TLS 1.2 [RFC 5246]
[RFC 6347], the ClientHello, ServerHello, and Certificate messages
are all sent in cleartext. This check is not possible with (D)TLS
1.3, which encrypts the Certificate message and therefore hides
the server identity from any intermediary. In (D)TLS 1.3, the
server certificate validation functions should be executed within
an on-path (D)TLS proxy if such a proxy exists.
* Support new communication patterns. An IoT device can learn a new
capability, and the new capability can change the way the IoT
device communicates with other devices located in the local
network and the Internet. There would be an inaccurate policy if
an IoT device rapidly changes the IP addresses and domain names it
communicates with while the MUD ACLs were slower to update (see
[CLEAR-AS-MUD]). In such a case, observable (D)TLS profile
parameters can be used to permit intended use and block malicious
behavior from the IoT device.
The YANG module specified in Section 5.2 of this document is an
extension of "YANG Data Model for Network Access Control Lists
(ACLs)" [RFC 8519] to enhance MUD [RFC 8520] to model observable (D)TLS
profile parameters. Using these (D)TLS profile parameters, an active
MUD-enforcing network security service (e.g., firewall) can identify
MUD non-compliant (D)TLS behavior indicating outdated cryptography or
malware. This detection can prevent malware downloads, block access
to malicious domains, enforce use of strong ciphers, stop data
exfiltration, etc. In addition, organizations may have policies
around acceptable ciphers and certificates for the websites the IoT
devices connect to. Examples include no use of old and less secure
versions of TLS, no use of self-signed certificates, deny-list or
accept-list of Certificate Authorities, valid certificate expiration
time, etc. These policies can be enforced by observing the (D)TLS
profile parameters. Network security services can use the IoT
device's (D)TLS profile parameters to identify legitimate flows by
observing (D)TLS sessions, and can make inferences to permit
legitimate flows and block malicious or insecure flows.
Additionally, it supports network communications adherence to
security policies by ensuring that TLS certificates are valid and
deprecated cipher suites are avoided. The proposed technique is also
suitable in deployments where decryption techniques are not ideal due
to privacy concerns, non-cooperating endpoints, and expense.
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 [RFC 2119] [RFC 8174] when, and only when, they appear in all
capitals, as shown here.
(D)TLS: Used for statements that apply to both Transport Layer
Security [RFC 8446] and Datagram Transport Layer Security
[RFC 6347]. Specific terms "TLS" and "DTLS" are used for any
statement that applies to either protocol alone.
DoH/DoT: Refers to DNS-over-HTTPS [RFC 8484] and/or DNS-over-TLS
[RFC 7858].
Middlebox: A middlebox that interacts with TLS traffic can either
act as a TLS proxy, intercepting and decrypting the traffic for
inspection, or inspect the traffic between TLS peers without
terminating the TLS session.
Endpoint Security Agent: An Endpoint Security Agent is a software
installed on endpoint devices that protects them from security
threats. It provides features such as malware protection,
firewall, and intrusion prevention to ensure the device's security
and integrity.
Network Security Service: A Network Security Service refers to a set
of mechanisms designed to protect network communications and
resources from attacks.
3. Overview of MUD (D)TLS Profiles for IoT devices
In Enterprise networks, protection and detection are typically done
both on end hosts and in the network. Endpoint security agents have
deep visibility on the devices where they are installed, whereas the
network has broader visibility. Installing endpoint security agents
may not be a viable option on IoT devices, and network security
service is an efficient means to protect such IoT devices. If the
IoT device supports a MUD (D)TLS profile, the (D)TLS profile
parameters of the IoT device can be used by a middlebox to detect and
block malware communication, while at the same time preserving the
privacy of legitimate uses of encryption. In addition, it enforces
organizational security policies, ensuring that devices comply. By
monitoring (D)TLS parameters, network administrators can identify and
mitigate the use of outdated TLS versions, cryptographic algorithms,
and non-compliant certificates. The middlebox need not proxy (D)TLS,
but can passively observe the parameters of (D)TLS handshakes from
IoT devices and gain visibility into TLS 1.2 parameters and partial
visibility into TLS 1.3 parameters.
Malicious agents can try to use the (D)TLS profile parameters of
legitimate agents to evade detection, but it becomes a challenge to
mimic the behavior of various IoT device types and IoT device models
from several manufacturers. In other words, malware developers will
have to develop malicious agents per IoT device type, manufacturer
and model, infect the device with the tailored malware agent, and
will have keep up with updates to the device's (D)TLS profile
parameters over time. Furthermore, the malware's command and control
server certificates need to be signed by the same certifying
authorities trusted by the IoT devices. Typically, IoT devices have
an infrastructure that supports a rapid deployment of updates, and
malware agents will have a near-impossible task of similarly
deploying updates and continuing to mimic the TLS behavior of the IoT
device it has infected.
However, if the IoT device has reached end-of-life (EOL) and the IoT
manufacturer will not issue a firmware or software update to the IoT
device or will not update the MUD file, the "is-supported" attribute
defined in Section 3.6 of [RFC 8520] can be used by the MUD manager to
indicate that the IoT manufacturer no longer supports the device.
The EOL of a device, where the IoT manufacturer no longer supports
it, does not necessarily mean the device is defective. Instead, it
signifies that the device is no longer receiving updates, support, or
security patches, which necessitates replacement and upgrading to
next-generation devices to ensure continued functionality, security,
and compatibility with modern networks. The network security service
will have to rely on other techniques discussed in Section 9 to
identify malicious connections until the device is replaced.
Compromised IoT devices are typically used for launching DDoS attacks
(Section 3 of [RFC 8576]). For example, DDoS attacks like Slowloris
[SLOWLORIS] and Transport Layer Security (TLS) re-negotiation can be
blocked if the victim's server certificate is not be signed by the
same certifying authorities trusted by the IoT device.
4. (D)TLS 1.3 Handshake
In (D)TLS 1.3, full (D)TLS handshake inspection is not possible since
all (D)TLS handshake messages excluding the ClientHello message are
encrypted. (D)TLS 1.3 has introduced new extensions in the handshake
record layers called Encrypted Extensions. When using these
extensions, handshake messages will be encrypted and network security
services (such as a firewall) are incapable of deciphering the
handshake, and thus cannot view the server certificate. However, the
ClientHello and ServerHello still have some fields visible, such as
the list of supported versions, named groups, cipher suites,
signature algorithms, extensions in ClientHello, and the chosen
cipher in the ServerHello. For instance, if the malware uses evasion
techniques like ClientHello randomization, the observable list of
cipher suites and extensions offered by the malware agent in the
ClientHello message will not match the list of cipher suites and
extensions offered by the legitimate client in the ClientHello
message, and the middlebox can block malicious flows without acting
as a (D)TLS 1.3 proxy.
4.1. Full (D)TLS 1.3 Handshake Inspection
To obtain more visibility into negotiated TLS 1.3 parameters, a
middlebox can act as a (D)TLS 1.3 proxy. A middlebox can act as a
(D)TLS proxy for the IoT devices owned and managed by the IT team in
the Enterprise network and the (D)TLS proxy must meet the security
and privacy requirements of the organization. In other words, the
scope of a middlebox acting as a (D)TLS proxy is restricted to the
Enterprise network owning and managing the IoT devices. The
middlebox would have to follow the behavior detailed in Section 9.3
of [RFC 8446] to act as a compliant (D)TLS 1.3 proxy.
To further increase privacy, the Encrypted Client Hello (ECH)
extension [TLS-ESNI] prevents passive observation of the TLS Server
Name Indication extension and other potentially sensitive fields,
such as the Application-Layer Protocol Negotiation (ALPN) [RFC 7301].
To effectively provide that privacy protection, the ECH extension
needs to be used in conjunction with DNS encryption (e.g., DoH). A
middlebox (e.g., firewall) passively inspecting the ECH extension
cannot observe the encrypted SNI nor observe the encrypted DNS
traffic. The middlebox acting as a (D)TLS 1.3 proxy that does not
support the ECH extension will act as if it is connecting to the
public name and follows the behavior discussed in Section 6.1.6 of
[TLS-ESNI] to securely signal the client to disable ECH.
4.2. Encrypted DNS
A common usage pattern for certain types of IoT devices (e.g., light
bulb) is for it to "call home" to a service that resides on the
public Internet, where that service is referenced through a domain
name (A or AAAA record). As discussed in "Manufacturer Usage
Description Specification" [RFC 8520], these devices tend to require
access to very few sites. Thus, all other access should be
considered suspect. This technique complements MUD policy
enforcement at the TLS level by ensuring that DNS queries are
monitored and filtered, thereby enhancing overall security. If an
IoT device is pre-configured to use a DNS resolver not signaled by
the network, the MUD policy enforcement point is moved to that
resolver, which cannot enforce the MUD policy based on domain names
(Section 8 of [RFC 8520]). If the DNS query is not accessible for
inspection, it becomes quite difficult for the infrastructure to
detect any issues. Therefore, the use of a DNS resolver that is not
signaled by the network is generally incompatible with MUD. A
network-designated DoH/DoT server is necessary to allow MUD policy
enforcement on the local network, for example, using the techniques
specified in DNR [RFC 9463] and DDR [RFC 9462].
5. (D)TLS Profile of an IoT device
This document specifies a YANG module that represents the (D)TLS
profile. This YANG module provides a means to characterize the
(D)TLS traffic profile of a device. Network security services can
use these profiles to permit conformant traffic or to deny traffic
from devices that deviates from it. This module uses the
cryptographic types defined in [RFC 9640]. See [RFC 7925] for (D)TLS
1.2 and [IoT-PROFILE] for DTLS 1.3 recommendations related to IoT
devices, and [RFC 9325] for additional (D)TLS 1.2 recommendations.
A companion YANG module is defined to include a collection of (D)TLS
parameters and (D)TLS versions maintained by IANA: "iana-tls-profile"
(Section 5.3).
The (D)TLS parameters in each (D)TLS profile include the following:
* Profile name
* (D)TLS versions supported by the IoT device.
* List of supported cipher suites (Section 11 of [RFC 8446]). For
(D)TLS 1.2, [RFC 7925] recommends Authenticated Encryption with
Associated Data (AEAD) ciphers for IoT devices.
* List of supported extension types.
* List of trust anchor certificates used by the IoT device. If the
server certificate is signed by one of the trust anchors, the
middlebox continues with the connection as normal. Otherwise, the
middlebox will react as if the server certificate validation has
failed and takes appropriate action (e.g, blocks the (D)TLS
session). An IoT device can use a private trust anchor to
validate a server's certificate (e.g., the private trust anchor
can be preloaded at manufacturing time on the IoT device and the
IoT device fetches the firmware image from the firmware server
whose certificate is signed by the private CA). This empowers the
middlebox to reject TLS sessions to servers that the IoT device
does not trust.
* List of pre-shared key exchange modes.
* List of named groups (DHE or ECDHE) supported by the client.
* List of signature algorithms the client can validate in X.509
server certificates.
* List of signature algorithms the client is willing to accept for
the CertificateVerify message (Section 4.2.3 of [RFC 8446]). For
example, a TLS client implementation can support different sets of
algorithms for certificates, and it can signal the capabilities in
the "signature_algorithms_cert" and "signature_algorithms"
extensions.
* List of supported application protocols (e.g., h3, h2, http/1.1
etc.).
* List of certificate compression algorithms (defined in [RFC 8879]).
* List of the distinguished names [X501] of acceptable certificate
authorities, represented in DER-encoded format [X690] (defined in
Section 4.2.4 of [RFC 8446]).
GREASE [RFC 8701] defines a mechanism for TLS peers to send random
values on TLS parameters to ensure future extensibility of TLS
extensions. Similar random values might be extended to other TLS
parameters. Thus, the (D)TLS profile parameters defined in the YANG
module by this document MUST NOT include the GREASE values for
extension types, named groups, signature algorithms, (D)TLS versions,
pre-shared key exchange modes, cipher suites, and any other TLS
parameters defined in future RFCs.
The (D)TLS profile does not include parameters like compression
methods for data compression. [RFC 9325] recommends disabling TLS-
level compression to prevent compression-related attacks. In TLS
1.3, only the "null" compression method is allowed (Section 4.1.2 of
[RFC 8446]).
5.1. Tree Structure of the (D)TLS Profile Extension to the ACL YANG
Module
This document augments the "ietf-acl" ACL YANG module defined in
[RFC 8519] for signaling the IoT device (D)TLS profile. This document
defines the YANG module "ietf-acl-tls". The meaning of the symbols
in the YANG tree diagram are defined in [RFC 8340] and it has the
following tree structure:
module: ietf-acl-tls
augment /acl:acls/acl:acl/acl:aces/acl:ace/acl:matches:
+--rw client-profiles {match-on-tls-dtls}?
+--rw tls-dtls-profile* [name]
+--rw name string
+--rw supported-tls-version* ianatp:tls-version
+--rw supported-dtls-version* ianatp:dtls-version
+--rw cipher-suite* ianatp:cipher-algorithm
+--rw extension-type*
| ianatp:extension-type
+--rw accept-list-ta-cert*
| ct:trust-anchor-cert-cms
+--rw psk-key-exchange-mode*
| ianatp:psk-key-exchange-mode
| {tls13 or dtls13}?
+--rw supported-groups*
| ianatp:supported-group
+--rw signature-algorithm-cert*
| ianatp:signature-algorithm
| {tls13 or dtls13}?
+--rw signature-algorithm*
| ianatp:signature-algorithm
+--rw application-protocol*
| ianatp:application-protocol
+--rw cert-compression-algorithm*
| ianatp:cert-compression-algorithm
| {tls13 or dtls13}?
+--rw certificate-authorities*
certificate-authority
{tls13 or dtls13}?
5.2. The (D)TLS Profile Extension to the ACL YANG Module
<CODE BEGINS> file "ietf-acl-tls@2025-04-18.yang"
module ietf-acl-tls {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-acl-tls";
prefix acl-tls;
import iana-tls-profile {
prefix ianatp;
reference
"RFC 9761: Manufacturer Usage Description (MUD) for TLS and
DTLS Profiles for Internet of Things (IoT) Devices";
}
import ietf-crypto-types {
prefix ct;
reference
"RFC 9640: YANG Data Types and Groupings for Cryptography";
}
import ietf-access-control-list {
prefix acl;
reference
"RFC 8519: YANG Data Model for Network Access
Control Lists (ACLs)";
}
organization
"IETF OPSAWG (Operations and Management Area Working Group)";
contact
"WG Web: <https://datatracker.ietf.org/wg/opsawg/>
WG List: opsawg@ietf.org
Author: Tirumaleswar Reddy.K
kondtir@gmail.com
Author: Dan Wing
danwing@gmail.com
Author: Blake Anderson
blake.anderson@cisco.com
";
description
"This YANG module defines a component that augments the
IETF description of an access list to allow (D)TLS profiles
as matching criteria.
Copyright (c) 2025 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 Revised 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 9761; see
the RFC itself for full legal notices.";
revision 2025-04-18 {
description
"Initial revision.";
reference
"RFC 9761: Manufacturer Usage Description (MUD) for TLS and
DTLS Profiles for Internet of Things (IoT) Devices";
}
feature tls12 {
description
"TLS Protocol Version 1.2 is supported.";
reference
"RFC 5246: The Transport Layer Security (TLS) Protocol
Version 1.2";
}
feature tls13 {
description
"TLS Protocol Version 1.3 is supported.";
reference
"RFC 8446: The Transport Layer Security (TLS) Protocol
Version 1.3";
}
feature dtls12 {
description
"DTLS Protocol Version 1.2 is supported.";
reference
"RFC 6347: Datagram Transport Layer Security
Version 1.2";
}
feature dtls13 {
description
"DTLS Protocol Version 1.3 is supported.";
reference
"RFC 9147: Datagram Transport Layer Security 1.3";
}
feature match-on-tls-dtls {
description
"The networking device can support matching on
(D)TLS parameters.";
}
typedef spki-pin-set {
type binary;
description
"Subject Public Key Info pin set as discussed in
Section 2.4 of RFC 7469.";
}
typedef certificate-authority {
type string;
description
"Distinguished Name of Certificate authority as discussed
in Section 4.2.4 of RFC 8446.";
}
augment "/acl:acls/acl:acl/acl:aces/acl:ace/acl:matches" {
if-feature "match-on-tls-dtls";
description
"(D)TLS specific matches.";
container client-profiles {
description
"A grouping for (D)TLS profiles.";
list tls-dtls-profile {
key "name";
description
"A list of (D)TLS version profiles supported by
the client.";
leaf name {
type string {
length "1..64";
}
description
"The name of (D)TLS profile; space and special
characters are not allowed.";
}
leaf-list supported-tls-version {
type ianatp:tls-version;
description
"TLS versions supported by the client.";
}
leaf-list supported-dtls-version {
type ianatp:dtls-version;
description
"DTLS versions supported by the client.";
}
leaf-list cipher-suite {
type ianatp:cipher-algorithm;
description
"A list of cipher suites supported by the client.";
}
leaf-list extension-type {
type ianatp:extension-type;
description
"A list of Extension Types supported by the client.";
}
leaf-list accept-list-ta-cert {
type ct:trust-anchor-cert-cms;
description
"A list of trust anchor certificates used by the
client.";
}
leaf-list psk-key-exchange-mode {
if-feature "tls13 or dtls13";
type ianatp:psk-key-exchange-mode;
description
"pre-shared key exchange modes.";
}
leaf-list supported-group {
type ianatp:supported-group;
description
"A list of named groups supported by the client.";
}
leaf-list signature-algorithm-cert {
if-feature "tls13 or dtls13";
type ianatp:signature-algorithm;
description
"A list signature algorithms the client can validate
in X.509 certificates.";
}
leaf-list signature-algorithm {
type ianatp:signature-algorithm;
description
"A list signature algorithms the client can validate
in the CertificateVerify message.";
}
leaf-list application-protocol {
type ianatp:application-protocol;
description
"A list application protocols supported by the client.";
}
leaf-list cert-compression-algorithm {
if-feature "tls13 or dtls13";
type ianatp:cert-compression-algorithm;
description
"A list certificate compression algorithms
supported by the client.";
}
leaf-list certificate-authorities {
if-feature "tls13 or dtls13";
type certificate-authority;
description
"A list of the distinguished names of certificate
authorities acceptable to the client.";
}
}
}
}
}
<CODE ENDS>
5.3. IANA (D)TLS Profile YANG Module
The TLS and DTLS IANA registries are available from
<https://www.iana.org/assignments/tls-parameters> and
<https://www.iana.org/assignments/tls-extensiontype-values>. Changes
to TLS- and DTLS-related IANA registries are discussed in [RFC 8447].
The values for all the parameters in the "iana-tls-profile" YANG
module are defined in the TLS and DTLS IANA registries excluding the
tls-version, dtls-version, spki-pin-set, and certificate-authority
parameters. The values of spki-pin-set and certificate-authority
parameters will be specific to the IoT device.
The TLS and DTLS IANA registries do not maintain (D)TLS version
numbers. In (D)TLS 1.2 and below, the "legacy_version" field in the
ClientHello message is used for version negotiation. However, in
(D)TLS 1.3, the "supported_versions" extension is used by the client
to indicate which versions of (D)TLS it supports. TLS 1.3
ClientHello messages are identified as having a "legacy_version" of
0x0303 and a "supported_versions" extension present with 0x0304 as
the highest version. DTLS 1.3 ClientHello messages are identified as
having a "legacy_version" of 0xfefd and a "supported_versions"
extension present with 0x0304 as the highest version.
In order to ease updating the "iana-tls-profile" YANG module with
future (D)TLS versions, new (D)TLS version registries are defined in
Section 11.3 and Section 11.4. Whenever a new (D)TLS protocol
version is defined, the registry will be updated using expert review;
the "iana-tls-profile" YANG module will be automatically updated by
IANA.
Implementers or users of this specification must refer to the IANA-
maintained "iana-tls-profile" YANG module available at
<https://www.iana.org/assignments/yang-parameters>.
The initial version of the "iana-tls-profile" YANG module is defined
as follows:
<CODE BEGINS> file "iana-tls-profile@2025-04-18.yang"
module iana-tls-profile {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:iana-tls-profile";
prefix ianatp;
organization
"IANA";
contact
" Internet Assigned Numbers Authority
Postal: ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094-2536
United States
Tel: +1 310 301 5800
Email: iana@iana.org>";
description
"This module contains the YANG definition for the (D)TLS profile.
Copyright (c) 2025 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 Revised 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).
All revisions of IETF and IANA published modules can be found
at the YANG Parameters registry
(https://www.iana.org/assignments/yang-parameters).
The initial version of this YANG module is part of RFC 9761;
see the RFC itself for full legal notices.
The latest version of this YANG module is available at
https://www.iana.org/assignments/yang-parameters.";
revision 2025-04-18 {
description
"Initial revision.";
reference
"RFC 9761: Manufacturer Usage Description (MUD) for TLS and
DTLS Profiles for Internet of Things (IoT) Devices";
}
typedef extension-type {
type uint16;
description
"Extension type in the TLS ExtensionType Values registry as
defined in Section 7 of RFC 8447.";
}
typedef supported-group {
type uint16;
description
"Supported Group in the TLS Supported Groups registry as
defined in Section 9 of RFC 8447.";
}
typedef signature-algorithm {
type uint16;
description
"Signature algorithm in the TLS SignatureScheme registry as
defined in Section 11 of RFC 8446.";
}
typedef psk-key-exchange-mode {
type uint8;
description
"Pre-shared key exchange mode in the TLS PskKeyExchangeMode
registry as defined in Section 11 of RFC 8446.";
}
typedef application-protocol {
type string;
description
"Application-Layer Protocol Negotiation (ALPN) Protocol ID
registry as defined in Section 6 of RFC 7301.";
}
typedef cert-compression-algorithm {
type uint16;
description
"Certificate compression algorithm in TLS Certificate
Compression Algorithm IDs registry as defined in
Section 7.3 of RFC 8879.";
}
typedef cipher-algorithm {
type uint16;
description
"Cipher suite in TLS Cipher Suites registry
as discussed in Section 11 of RFC 8446.";
}
typedef tls-version {
type enumeration {
enum tls12 {
value 1;
description
"TLS Protocol Version 1.2.
TLS 1.2 ClientHello contains
0x0303 in 'legacy_version'.";
reference
"RFC 5246: The Transport Layer Security (TLS) Protocol
Version 1.2";
}
enum tls13 {
value 2;
description
"TLS Protocol Version 1.3.
TLS 1.3 ClientHello contains a
supported_versions extension with 0x0304
contained in its body and the ClientHello contains
0x0303 in 'legacy_version'.";
reference
"RFC 8446: The Transport Layer Security (TLS) Protocol
Version 1.3";
}
}
description
"Indicates the TLS version.";
}
typedef dtls-version {
type enumeration {
enum dtls12 {
value 1;
description
"DTLS Protocol Version 1.2.
DTLS 1.2 ClientHello contains
0xfefd in 'legacy_version'.";
reference
"RFC 6347: Datagram Transport Layer Security 1.2";
}
enum dtls13 {
value 2;
description
"DTLS Protocol Version 1.3.
DTLS 1.3 ClientHello contains a
supported_versions extension with 0x0304
contained in its body and the ClientHello contains
0xfefd in 'legacy_version'.";
reference
"RFC 9147: Datagram Transport Layer Security 1.3";
}
}
description
"Indicates the DTLS version.";
}
}
<CODE ENDS>
5.4. MUD (D)TLS Profile Extension
This document augments the "ietf-mud" MUD YANG module to indicate
whether the device supports (D)TLS profile. If the "ietf-mud-tls"
extension is supported by the device, MUD file is assumed to
implement the "match-on-tls-dtls" ACL model feature defined in this
specification. Furthermore, only "accept" or "drop" actions SHOULD
be included with the (D)TLS profile similar to the actions allowed in
Section 2 of [RFC 8520].
This document defines the YANG module "ietf-mud-tls", which has the
following tree structure:
module: ietf-mud-tls
augment /ietf-mud:mud:
+--rw is-tls-dtls-profile-supported? boolean
The model is defined as follows:
<CODE BEGINS> file "ietf-mud-tls@2025-04-18.yang"
module ietf-mud-tls {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-mud-tls";
prefix ietf-mud-tls;
import ietf-mud {
prefix ietf-mud;
reference
"RFC 8520: Manufacturer Usage Description Specification";
}
organization
"IETF OPSAWG (Operations and Management Area Working Group)";
contact
"WG Web: <https://datatracker.ietf.org/wg/opsawg/>
WG List: opsawg@ietf.org
Author: Tirumaleswar Reddy.K
kondtir@gmail.com
Author: Dan Wing
danwing@gmail.com
Author: Blake Anderson
blake.anderson@cisco.com
";
description
"Extension to a MUD module to indicate (D)TLS
profile support.
Copyright (c) 2025 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 Revised 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 9761; see
the RFC itself for full legal notices.";
revision 2025-04-18 {
description
"Initial revision.";
reference
"RFC 9761: Manufacturer Usage Description (MUD) for TLS and
DTLS Profiles for Internet of Things (IoT)
Devices";
}
augment "/ietf-mud:mud" {
description
"This adds an extension for a manufacturer
to indicate whether the (D)TLS profile is
supported by a device.";
leaf is-tls-dtls-profile-supported {
type boolean;
default "false";
description
"This value will equal 'true' if a device supports
(D)TLS profile.";
}
}
}
<CODE ENDS>
6. Processing of the MUD (D)TLS Profile
The following text outlines the rules for a network security service
(e.g., firewall) to follow to process the MUD (D)TLS Profile so as to
avoid ossification:
* If the (D)TLS parameter observed in a (D)TLS session is not
specified in the MUD (D)TLS profile and the parameter is
recognized by the firewall, it can identify unexpected (D)TLS
usage, which can indicate the presence of unauthorized software or
malware on an endpoint. The firewall can take several actions,
such as blocking the (D)TLS session or raising an alert to
quarantine and remediate the compromised device. For example, if
the cipher suite TLS_RSA_WITH_AES_128_CBC_SHA in the ClientHello
message is not specified in the MUD (D)TLS profile and the cipher
suite is recognized by the firewall, it can identify unexpected
TLS usage.
* If the (D)TLS parameter observed in a (D)TLS session is not
specified in the MUD (D)TLS profile and the (D)TLS parameter is
not recognized by the firewall, it can ignore the unrecognized
parameter and the correct behavior is not to block the (D)TLS
session. The behavior is functionally equivalent to the compliant
TLS middlebox description in Section 9.3 of [RFC 8446] to ignore
all unrecognized cipher suites, extensions, and other parameters.
For example, if the cipher suite TLS_CHACHA20_POLY1305_SHA256 in
the ClientHello message is not specified in the MUD (D)TLS profile
and the cipher suite is not recognized by the firewall, it can
ignore the unrecognized cipher suite. This rule also ensures that
the network security service will ignore the GREASE values
advertised by TLS peers and interoperate with the implementations
advertising GREASE values.
* Deployments update at different rates, so an updated MUD (D)TLS
profile may support newer parameters. If the firewall does not
recognize the newer parameters, an alert should be triggered to
the firewall vendor and the IoT device owner or administrator. A
firewall must be readily updatable so that when new parameters in
the MUD (D)TLS profile are discovered that are not recognized by
the firewall, it can be updated quickly. Most importantly, if the
firewall is not readily updatable, its protection efficacy to
identify emerging malware will decrease with time. For example,
if the cipher suite TLS_AES_128_CCM_8_SHA256 specified in the MUD
(D)TLS profile is not recognized by the firewall, an alert will be
triggered. Similarly, if the (D)TLS version specified in the MUD
file is not recognized by the firewall, an alert will be
triggered.
* If the MUD (D)TLS profile includes any parameters that are
susceptible to attacks (e.g., weaker cryptographic parameters), an
alert MUST be triggered to the firewall vendor and the IoT device
owner or administrator.
7. MUD File Example
The example below contains (D)TLS profile parameters for an IoT
device used to reach servers listening on port 443 using TCP
transport. JSON encoding of YANG-modeled data [RFC 7951] is used to
illustrate the example.
{
"ietf-mud:mud": {
"mud-version": 1,
"mud-url": "https://example.com/IoTDevice",
"last-update": "2024-08-05T03:56:40.105+10:00",
"cache-validity": 100,
"extensions": [
"ietf-mud-tls"
],
"ietf-mud-tls:is-tls-dtls-profile-supported": "true",
"is-supported": true,
"systeminfo": "IoT device name",
"from-device-policy": {
"access-lists": {
"access-list": [
{
"name": "mud-7500-profile"
}
]
}
},
"ietf-access-control-list:acls": {
"acl": [
{
"name": "mud-7500-profile",
"type": "ipv6-acl-type",
"aces": {
"ace": [
{
"name": "cl0-frdev",
"matches": {
"ipv6": {
"protocol": 6
},
"tcp": {
"ietf-mud:direction-initiated": "from-device",
"destination-port": {
"operator": "eq",
"port": 443
}
},
"ietf-acl-tls:client-profile" : {
"tls-dtls-profiles" : [
{
"name" : "profile1",
"supported-tls-versions" : ["tls13"],
"cipher-suite" : [4865, 4866],
"extension-types" : [10,11,13,16,24],
"supported-groups" : [29]
}
]
},
"actions": {
"forwarding": "accept"
}
}
}
]
}
}
]
}
}
}
The following illustrates the example scenarios for processing the
above profile:
* If the extension type "encrypt_then_mac" (code point 22) [RFC 7366]
in the ClientHello message is recognized by the firewall, it can
identify unexpected TLS usage.
* If the extension type "token_binding" (code point 24) [RFC 8472] in
the MUD (D)TLS profile is not recognized by the firewall, it can
ignore the unrecognized extension. Because the extension type
"token_binding" is specified in the profile, an alert will be
triggered to the firewall vendor and the IoT device owner or
administrator to notify the firewall is not up-to-date.
* The two-byte values assigned by IANA for the cipher suites
TLS_AES_128_GCM_SHA256 and TLS_AES_256_GCM_SHA384 are represented
in decimal format.
8. Software-Based ACLs and ACLs Within a (D)TLS 1.3 Proxy
While ACL technology is traditionally associated with fixed-length
bit matching in hardware implementations, such as those found in
Ternary Content-Addressable Memory (TCAM), the use of ACLs in
software, like with iptables, allows for more flexible matching
criteria, including string matching. In the context of MUD (D)TLS
profiles, the ability to match binary data and strings is a
deliberate choice made to leverage the capabilities of software-based
ACLs. This enables more dynamic and context-sensitive access
control, which is essential for the intended application of MUD. The
DNS extension added to ACL in the MUD specification [RFC 8520] also
requires software-based ACLs.
Regarding the use of MUD (D)TLS ACL in a (D)TLS 1.3 proxy, the goal
is for the proxy to intercept the (D)TLS handshake before applying
any ACL rules. This implies that MUD (D)TLS ACL matching would need
to occur after decrypting the encrypted TLS handshake messages within
the proxy. The proxy would inspect the handshake fields according to
the MUD profile. ACL matching would be performed in two stages:
first, by filtering clear-text TLS handshake message and second, by
filtering after decrypting the TLS handshake messages.
9. Security Considerations
Security considerations in [RFC 8520] need to be taken into
consideration. The middlebox MUST adhere to the invariants discussed
in Section 9.3 of [RFC 8446] to act as a compliant proxy.
Although it is challenging for malware to mimic the TLS behavior of
various IoT device types and models from different manufacturers,
there is still a potential for malicious agents to use similar (D)TLS
profile parameters as legitimate devices to evade detection. This
difficulty arises because IoT devices often have distinct (D)TLS
profiles between models and especially between manufacturers. While
malware may find it hard to perfectly replicate the TLS behavior
across such diverse devices, it is not impossible. Malicious agents
might manage to use (D)TLS profile parameters that resemble those of
legitimate devices. The feasibility of this depends on the nature of
the profile parameters; for instance, parameters like certificate
authorities are complex to mimic, while others, such as signature
algorithms, may be easier to replicate. The difficulty in mimicking
these profiles correlates with the specificity of the profiles and
the variability in parameters used by different devices.
Network security services should also rely on contextual network data
(e.g., domain name, IP address, etc.) to detect false negatives. For
example, network security services filter malicious domain names and
destination IP addresses with a bad reputation score. Furthermore,
in order to detect such malicious flows, anomaly detection (deep
learning techniques on network data) can be used to detect malicious
agents using the same (D)TLS profile parameters as the legitimate
agent on the IoT device. In anomaly detection, the main idea is to
maintain rigorous learning of "normal" behavior and where an
"anomaly" (or an attack) is identified and categorized based on the
knowledge about the normal behavior and a deviation from this normal
behavior. Network security vendors leverage TLS parameters and
contextual network data to identify malware (for example, see [EVE]).
The efficacy of identifying malware in (D)TLS 1.3 flows will be
significantly reduced without leveraging contextual network data or
acting as a proxy, as the encryption in (D)TLS 1.3 obscures many of
the handshake details that could otherwise be used for detection.
9.1. Challenges in Mimicking (D)TLS 1.2 Handshakes for IoT Devices
(D)TLS 1.2 generally does not require a proxy, as all fields in the
(D)TLS profile are transmitted in cleartext during the handshake.
While it is technically possible for an attacker to observe and mimic
the handshake, an attacker would need to use a domain name and
destination IP address with a good reputation, obtain certificates
from the same CAs used by the IoT devices, and evade traffic analysis
techniques (e.g., [EVE], which detects malicious patterns in
encrypted traffic without decryption). This task is particularly
challenging because IoT devices often have distinct (D)TLS profiles
that vary between models and manufacturers. Unlike the developers of
legitimate applications, malware authors are under additional
constraints, such as avoiding any noticeable differences on the
infected devices and the potential for take-down requests impacting
their server infrastructure (e.g., certificate revocation by a CA
upon reporting).
9.2. Considerations for the "iana-tls-profile" Module
This section follows the template defined in Section 3.7.1 of
[YANG-GUIDELINES].
The "iana-tls-profile" YANG module defines a data model that is
designed to be accessed via YANG-based management protocols, such as
NETCONF [RFC 6241] and RESTCONF [RFC 8040]. These protocols have to
use a secure transport layer (e.g., SSH [RFC 4252], TLS [RFC 8446], and
QUIC [RFC 9000]) and have to use mutual authentication.
The Network Configuration Access Control Model (NACM) [RFC 8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
There are no particularly sensitive writable data nodes.
There are no particularly sensitive readable data nodes.
This YANG module defines YANG enumerations for a public IANA-
maintained registry.
YANG enumerations are not security-sensitive, as they are statically
defined in the publicly accessible YANG module. IANA MAY deprecate
and/or obsolete enumerations over time as needed to address security
issues.
There are no particularly sensitive RPC or action operations.
The YANG module defines a set of identities, types, and groupings.
These nodes are intended to be reused by other YANG modules. The
module by itself does not expose any data nodes that are writable,
data nodes that contain read-only state, or RPCs. As such, there are
no additional security issues related to the YANG module that need to
be considered.
9.3. Considerations for the "ietf-acl-tls" Module
This section follows the template defined in Section 3.7.1 of
[YANG-GUIDELINES].
The "ietf-acl-tls" YANG module defines a data model that is designed
to be accessed via YANG-based management protocols, such as NETCONF
[RFC 6241] and RESTCONF [RFC 8040]. These protocols have to use a
secure transport layer (e.g., SSH [RFC 4252], TLS [RFC 8446], and QUIC
[RFC 9000]) and have to use mutual authentication.
The Network Configuration Access Control Model (NACM) [RFC 8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., "config true", which is the
default). All writable data nodes are likely to be reasonably
sensitive or vulnerable in some network environments. Write
operations (e.g., edit-config) and delete operations to these data
nodes without proper protection or authentication can have a negative
effect on network operations. For instance, the addition or removal
of references to trusted anchors, (D)TLS versions, cipher suites,
etc., can dramatically alter the implemented security policy. For
this reason, the NACM extension "default-deny-write" has been set for
all data nodes defined in this module.
Some of the readable data nodes defined in this YANG module may be
considered sensitive or vulnerable in some network environments. It
is thus important to control read access (e.g., via get, get-config,
or notification) to these data nodes. The YANG module will provide
insights into (D)TLS profiles of the IoT devices, and the privacy
considerations discussed in Section 10 need to be taken into account.
There are no particularly sensitive RPC or action operations.
This YANG module uses groupings from other YANG modules that define
nodes that may be considered sensitive or vulnerable in network
environments. Refer to the Security Considerations for dependent
YANG modules for information as to which nodes may be considered
sensitive or vulnerable in network environments.
9.4. Considerations for the "ietf-mud-tls" Module
This section follows the template defined in Section 3.7.1 of
[YANG-GUIDELINES].
The "ietf-mud-tls" YANG module defines a data model that is designed
to be accessed via YANG-based management protocols, such as NETCONF
[RFC 6241] and RESTCONF [RFC 8040]. These protocols have to use a
secure transport layer (e.g., SSH [RFC 4252], TLS [RFC 8446], and QUIC
[RFC 9000]) and have to use mutual authentication.
The Network Configuration Access Control Model (NACM) [RFC 8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., "config true", which is the
default). All writable data nodes are likely to be reasonably
sensitive or vulnerable in some network environments. Write
operations (e.g., edit-config) and delete operations to these data
nodes without proper protection or authentication can have a negative
effect on network operations. For instance, update that the device
does not support (D)TLS profile can dramatically alter the
implemented security policy. For this reason, the NACM extension
"default-deny-write" has been set for all data nodes defined in this
module.
There are no particularly sensitive RPC or action operations.
This YANG module uses groupings from other YANG modules that define
nodes that may be considered sensitive or vulnerable in network
environments. Refer to the Security Considerations for dependent
YANG modules for information as to which nodes may be considered
sensitive or vulnerable in network environments.
10. Privacy Considerations
Privacy considerations discussed in Section 16 of [RFC 8520] to not
reveal the MUD URL to an attacker need to be taken into
consideration. The MUD URL can be stored in a Trusted Execution
Environment (TEE) for secure operation, enhanced data security, and
prevention of exposure to unauthorized software. The MUD URL MUST be
encrypted and shared only with the authorized components in the
network (see Sections 1.5 and 1.8 of [RFC 8520]) so that an on-path
attacker cannot read the MUD URL and identify the IoT device.
Otherwise, it provides the attacker with guidance on what
vulnerabilities may be present on the IoT device. Note that while
protecting the MUD URL is valuable as described above, a compromised
IoT device may be susceptible to malware performing vulnerability
analysis (and version mapping) of the legitimate software located in
memory or on non-volatile storage (e.g., disk, NVRAM). However, the
malware on the IoT device is intended to be blocked from establishing
a (D)TLS connection with the C&C server to reveal this information
because the connection would be blocked by the network security
service supporting this specification.
Full handshake inspection (Section 4.1) requires a (D)TLS proxy
device that needs to decrypt traffic between the IoT device and its
server(s). There is a tradeoff between privacy of the data carried
inside (D)TLS (for example, personally identifiable information and
protected health information especially) and efficacy of endpoint
security. The use of (D)TLS proxies is NOT RECOMMENDED whenever
possible. For example, an enterprise firewall administrator can
configure the middlebox to bypass (D)TLS proxy functionality or
payload inspection for connections destined to specific well-known
services. Alternatively, an IoT device could be configured to reject
all sessions that involve proxy servers to specific well-known
services. In addition, mechanisms based on object security can be
used by IoT devices to enable end-to-end security and the middlebox
will not have any access to the packet data. For example, Object
Security for Constrained RESTful Environments (OSCORE) [RFC 8613] is a
proposal that protects Constrained Application Protocol (CoAP)
messages by wrapping them in the CBOR Object Signing and Encryption
(COSE) format [RFC 9052].
11. IANA Considerations
11.1. (D)TLS Profile YANG Modules
IANA has registered the following URIs in the "ns" subregistry within
the "IETF XML Registry" [RFC 3688]:
URI: urn:ietf:params:xml:ns:yang:iana-tls-profile
Registrant Contact: IANA.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-acl-tls
Registrant Contact: IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-mud-tls
Registrant Contact: IESG.
XML: N/A; the requested URI is an XML namespace.
IANA has created an IANA-maintained YANG module called "iana-tls-
profile" based on the contents of Section 5.3, which allows for new
(D)TLS parameters and (D)TLS versions to be added to "client-
profile".
IANA has registered the following YANG modules in the "YANG Module
Names" registry [RFC 6020] of the "YANG Parameters" registry group.
Name: iana-tls-profile
Namespace: urn:ietf:params:xml:ns:yang:iana-tls-profile
Maintained by IANA: Y
Prefix: ianatp
Reference: RFC 9761
Name: ietf-acl-tls
Namespace: urn:ietf:params:xml:ns:yang:ietf-acl-tls
Maintained by IANA: N
Prefix: ietf-acl-tls
Reference: RFC 9761
Name: ietf-mud-tls
Namespace: urn:ietf:params:xml:ns:yang:ietf-mud-tls
Maintained by IANA: N
Prefix: ietf-mud-tls
Reference: RFC 9761
11.2. Considerations for the iana-tls-profile Module
IANA has created the initial version of the IANA-maintained YANG
module called "iana-tls-profile" based on the contents of
Section 5.3, which will allow for new (D)TLS parameters and (D)TLS
versions to be added. IANA is requested to add this note:
* tls-version and dtls-version values must not be directly added to
the iana-tls-profile YANG module. Instead, they must be added to
the "ACL TLS Version Codes" and "ACL DTLS Version Codes"
registries (respectively), provided the new (D)TLS version has
been standardized by the IETF. It allows a new (D)TLS version to
be added to the "iana-tls-profile" YANG module.
* (D)TLS parameters must not be directly added to the iana-tls-
profile YANG module. They must instead be added to the "ACL
(D)TLS Parameters" registry if the new (D)TLS parameters can be
used by a middlebox to identify a MUD non-compliant (D)TLS
behavior. It allows new (D)TLS parameters to be added to the
"iana-tls-profile" YANG module.
When a "tls-version" or "dtls-version" value is added to the "ACL TLS
Version Codes" or "ACL DTLS Version Codes" registry (respectively), a
new "enum" statement must be added to the iana-tls-profile YANG
module. The following "enum" statement, and substatements thereof,
should be defined:
"enum": Replicates the label from the registry.
"value": Contains the IANA-assigned value corresponding to the
"tls-version" or "dtls-version".
"description": Replicates the description from the registry.
"reference": RFC YYYY: <Title of the RFC>, where YYYY is the RFC
that added the "tls-version" or "dtls-version".
When a (D)TLS parameter is added to the "ACL (D)TLS Parameters"
registry, a new "type" statement must be added to the iana-tls-
profile YANG module. The following "type" statement, and
substatements thereof, should be defined:
"derived type": Replicates the parameter name from the registry.
"built-in type": Contains the built-in YANG type.
"description": Replicates the description from the registry.
When the iana-tls-profile YANG module is updated, a new "revision"
statement must be added in front of the existing revision statements.
IANA has added this note to "ACL TLS Version Codes", "ACL DTLS
Version Codes", and "ACL (D)TLS Parameters" registries:
When this registry is modified, the YANG module "iana-tls-profile"
must be updated as defined in [RFC 9761].
11.3. ACL TLS Version Registry
IANA has created a new registry titled "ACL TLS Version Codes".
Codes in this registry are used as valid values of "tls-version"
parameter. Further assignments are to be made through Expert Review
[RFC 8126]. Experts must ensure that the TLS protocol version in a
new registration is one that has been standardized by the IETF. It
is expected that the registry will be updated infrequently, primarily
when a new TLS version is standardized by the IETF.
+=======+=======+=================+===========+
| Value | Label | Description | Reference |
+=======+=======+=================+===========+
| 1 | tls12 | TLS Version 1.2 | [RFC 5246] |
+-------+-------+-----------------+-----------+
| 2 | tls13 | TLS Version 1.3 | [RFC 8446] |
+-------+-------+-----------------+-----------+
Table 1
11.4. ACL DTLS Version Registry
IANA has created a new registry titled "ACL DTLS Version Codes".
Codes in this registry are used as valid values of "dtls-version"
parameter. Further assignments are to be made through Expert Review
[RFC 8126]. Experts must ensure that the DTLS protocol version in a
new registration is one that has been standardized by the IETF. It
is expected that the registry will be updated infrequently, primarily
when a new DTLS version is standardized by the IETF.
+=======+========+==================+===========+
| Value | Label | Description | Reference |
+=======+========+==================+===========+
| 1 | dtls12 | DTLS Version 1.2 | [RFC 6347] |
+-------+--------+------------------+-----------+
| 2 | dtls13 | DTLS Version 1.3 | [RFC 9147] |
+-------+--------+------------------+-----------+
Table 2
11.5. ACL (D)TLS Parameters Registry
IANA has created a new registry titled "ACL (D)TLS Parameters".
The values for all the (D)TLS parameters in the registry are defined
in the TLS and DTLS IANA registries
(https://www.iana.org/assignments/tls-parameters/ and
https://www.iana.org/assignments/tls-extensiontype-values/) excluding
the tls-version and dtls-version parameters. Further assignments are
to be made through Expert Review [RFC 8126]. Experts must ensure that
the (D)TLS parameter in a new registration is one that has been
standardized by the IETF. The registry is expected to be updated
periodically, primarily when a new (D)TLS parameter is standardized
by the IETF. The registry has been populated with the following
initial parameters:
+============================+=============+========+==============+
| Parameter Name | YANG Type | JSON | Description |
| | | Type | |
+============================+=============+========+==============+
| extension-type | uint16 | Number | Extension |
| | | | type |
+----------------------------+-------------+--------+--------------+
| supported-group | uint16 | Number | Supported |
| | | | group |
+----------------------------+-------------+--------+--------------+
| signature-algorithm | uint16 | Number | Signature |
| | | | algorithm |
+----------------------------+-------------+--------+--------------+
| psk-key-exchange-mode | uint8 | Number | Pre-shared |
| | | | key exchange |
| | | | mode |
+----------------------------+-------------+--------+--------------+
| application-protocol | string | String | Application |
| | | | protocol |
+----------------------------+-------------+--------+--------------+
| cert-compression-algorithm | uint16 | Number | Certificate |
| | | | compression |
| | | | algorithm |
+----------------------------+-------------+--------+--------------+
| cipher-algorithm | uint16 | Number | Cipher suite |
+----------------------------+-------------+--------+--------------+
| tls-version | enumeration | String | TLS version |
+----------------------------+-------------+--------+--------------+
| dtls-version | enumeration | String | DTLS version |
+----------------------------+-------------+--------+--------------+
Table 3
11.6. MUD Extensions Registry
IANA has created a new MUD Extension Name "ietf-mud-tls" in the "MUD
Extensions" IANA registry <https://www.iana.org/assignments/mud>.
12. References
12.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<https://www.rfc-editor.org/info/RFC 2119>.
[RFC 3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC 3688, January 2004,
<https://www.rfc-editor.org/info/RFC 3688>.
[RFC 4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC 4252,
January 2006, <https://www.rfc-editor.org/info/RFC 4252>.
[RFC 5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC 5246, August 2008,
<https://www.rfc-editor.org/info/RFC 5246>.
[RFC 6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC 6241, June 2011,
<https://www.rfc-editor.org/info/RFC 6241>.
[RFC 6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC 6347,
January 2012, <https://www.rfc-editor.org/info/RFC 6347>.
[RFC 8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC 8040, January 2017,
<https://www.rfc-editor.org/info/RFC 8040>.
[RFC 8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC 8174,
May 2017, <https://www.rfc-editor.org/info/RFC 8174>.
[RFC 8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC 8341, March 2018,
<https://www.rfc-editor.org/info/RFC 8341>.
[RFC 8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC 8446, August 2018,
<https://www.rfc-editor.org/info/RFC 8446>.
[RFC 8519] Jethanandani, M., Agarwal, S., Huang, L., and D. Blair,
"YANG Data Model for Network Access Control Lists (ACLs)",
RFC 8519, DOI 10.17487/RFC 8519, March 2019,
<https://www.rfc-editor.org/info/RFC 8519>.
[RFC 8520] Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
Description Specification", RFC 8520,
DOI 10.17487/RFC 8520, March 2019,
<https://www.rfc-editor.org/info/RFC 8520>.
[RFC 8701] Benjamin, D., "Applying Generate Random Extensions And
Sustain Extensibility (GREASE) to TLS Extensibility",
RFC 8701, DOI 10.17487/RFC 8701, January 2020,
<https://www.rfc-editor.org/info/RFC 8701>.
[RFC 8879] Ghedini, A. and V. Vasiliev, "TLS Certificate
Compression", RFC 8879, DOI 10.17487/RFC 8879, December
2020, <https://www.rfc-editor.org/info/RFC 8879>.
[RFC 9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC 9000, May 2021,
<https://www.rfc-editor.org/info/RFC 9000>.
[RFC 9147] Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", RFC 9147, DOI 10.17487/RFC 9147, April 2022,
<https://www.rfc-editor.org/info/RFC 9147>.
[RFC 9640] Watsen, K., "YANG Data Types and Groupings for
Cryptography", RFC 9640, DOI 10.17487/RFC 9640, October
2024, <https://www.rfc-editor.org/info/RFC 9640>.
[X690] ITU-T, "Information technology - ASN.1 encoding Rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ITU-T Recommendation X.690, 2021,
<https://www.itu.int/rec/T-REC-X.690-202102-I/en>.
12.2. Informative References
[CLEAR-AS-MUD]
Hamza, A., Ranathunga, D., Gharakheili, H. H., Roughan,
M., and V. Sivaraman, "Clear as MUD: Generating,
Validating and Applying IoT Behaviorial Profiles
(Technical Report)", arXiv:1804.04358,
DOI 10.48550/arXiv.1804.04358, April 2018,
<https://arxiv.org/pdf/1804.04358.pdf>.
[CRYPTO-VULNERABILITY]
Perez, B., "Exploiting the Windows CryptoAPI
Vulnerability", January 2020,
<https://securityboulevard.com/2020/01/exploiting-the-
windows-cryptoapi-vulnerability/>.
[EVE] Cisco, "Encrypted Visibility Engine", Cisco Secure
Firewall documentation, <https://secure.cisco.com/secure-
firewall/docs/encrypted-visibility-engine>.
[IoT-PROFILE]
Tschofenig, H., Fossati, T., and M. Richardson, "TLS/DTLS
1.3 Profiles for the Internet of Things", Work in
Progress, Internet-Draft, draft-ietf-uta-tls13-iot-
profile-13, 3 March 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-uta-
tls13-iot-profile-13>.
[MALWARE-DOH]
Cimpanu, C., "First-ever malware strain spotted abusing
new DoH (DNS over HTTPS) protocol", ZDNET, July 2019,
<https://www.zdnet.com/article/first-ever-malware-strain-
spotted-abusing-new-doh-dns-over-https-protocol/>.
[MALWARE-TLS]
Anderson, B. and D. McGrew, "TLS Beyond the Browser:
Combining End Host and Network Data to Understand
Application Behavior", IMC '19: Proceedings of the
Internet Measurement Conference, pp. 379-392,
DOI 10.1145/3355369.3355601, October 2019,
<https://dl.acm.org/citation.cfm?id=3355601>.
[RFC 6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC 6020, October 2010,
<https://www.rfc-editor.org/info/RFC 6020>.
[RFC 6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC 6066, January 2011,
<https://www.rfc-editor.org/info/RFC 6066>.
[RFC 7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC 7301,
July 2014, <https://www.rfc-editor.org/info/RFC 7301>.
[RFC 7366] Gutmann, P., "Encrypt-then-MAC for Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", RFC 7366, DOI 10.17487/RFC 7366, September 2014,
<https://www.rfc-editor.org/info/RFC 7366>.
[RFC 7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC 7858, May
2016, <https://www.rfc-editor.org/info/RFC 7858>.
[RFC 7925] Tschofenig, H., Ed. and T. Fossati, "Transport Layer
Security (TLS) / Datagram Transport Layer Security (DTLS)
Profiles for the Internet of Things", RFC 7925,
DOI 10.17487/RFC 7925, July 2016,
<https://www.rfc-editor.org/info/RFC 7925>.
[RFC 7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC 7951, August 2016,
<https://www.rfc-editor.org/info/RFC 7951>.
[RFC 8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC 8126, June 2017,
<https://www.rfc-editor.org/info/RFC 8126>.
[RFC 8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC 8340, March 2018,
<https://www.rfc-editor.org/info/RFC 8340>.
[RFC 8447] Salowey, J. and S. Turner, "IANA Registry Updates for TLS
and DTLS", RFC 8447, DOI 10.17487/RFC 8447, August 2018,
<https://www.rfc-editor.org/info/RFC 8447>.
[RFC 8472] Popov, A., Ed., Nystroem, M., and D. Balfanz, "Transport
Layer Security (TLS) Extension for Token Binding Protocol
Negotiation", RFC 8472, DOI 10.17487/RFC 8472, October
2018, <https://www.rfc-editor.org/info/RFC 8472>.
[RFC 8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC 8484, October 2018,
<https://www.rfc-editor.org/info/RFC 8484>.
[RFC 8576] Garcia-Morchon, O., Kumar, S., and M. Sethi, "Internet of
Things (IoT) Security: State of the Art and Challenges",
RFC 8576, DOI 10.17487/RFC 8576, April 2019,
<https://www.rfc-editor.org/info/RFC 8576>.
[RFC 8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments
(OSCORE)", RFC 8613, DOI 10.17487/RFC 8613, July 2019,
<https://www.rfc-editor.org/info/RFC 8613>.
[RFC 9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC 9052, August 2022,
<https://www.rfc-editor.org/info/RFC 9052>.
[RFC 9325] Sheffer, Y., Saint-Andre, P., and T. Fossati,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC 9325, November
2022, <https://www.rfc-editor.org/info/RFC 9325>.
[RFC 9462] Pauly, T., Kinnear, E., Wood, C. A., McManus, P., and T.
Jensen, "Discovery of Designated Resolvers", RFC 9462,
DOI 10.17487/RFC 9462, November 2023,
<https://www.rfc-editor.org/info/RFC 9462>.
[RFC 9463] Boucadair, M., Ed., Reddy.K, T., Ed., Wing, D., Cook, N.,
and T. Jensen, "DHCP and Router Advertisement Options for
the Discovery of Network-designated Resolvers (DNR)",
RFC 9463, DOI 10.17487/RFC 9463, November 2023,
<https://www.rfc-editor.org/info/RFC 9463>.
[SLOWLORIS]
Wikipedia, "Slowloris (cyber attack)", December 2024,
<https://en.wikipedia.org/w/index.php?title=Slowloris_(cyb
er_attack)&oldid=1263305193>.
[TLS-ESNI] Rescorla, E., Oku, K., Sullivan, N., and C. A. Wood, "TLS
Encrypted Client Hello", Work in Progress, Internet-Draft,
draft-ietf-tls-esni-24, 20 March 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
esni-24>.
[X501] "Information Technology - Open Systems Interconnection -
The Directory: Models", ITU-T Recommendation X.501,
October 2019,
<https://www.itu.int/rec/T-REC-X.501-201910-I/en>.
[YANG-GUIDELINES]
Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
Authors and Reviewers of Documents Containing YANG Data
Models", Work in Progress, Internet-Draft, draft-ietf-
netmod-rfc8407bis-23, 15 April 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
rfc8407bis-23>.
Acknowledgments
Thanks to Flemming Andreasen, Shashank Jain, Michael Richardson,
Piyush Joshi, Eliot Lear, Harsha Joshi, Qin Wu, Mohamed Boucadair,
Ben Schwartz, Eric Rescorla, Panwei William, Nick Lamb, Tom Petch,
Paul Wouters, Thomas Fossati, and Nick Harper for the discussion and
comments.
Thanks to Xufeng Liu for YANGDOCTOR review. Thanks to Linda Dunbar
for SECDIR review. Thanks to Qin Wu for OPSDIR review. Thanks to
R. Gieben for DNSDIR review.
Thanks to Roman Danyliw, Orie Steele, Éric Vyncke, Mahesh
Jethanandani, Murray Kucherawy, Zaheduzzaman Sarker, and Deb Cooley
for the IESG review.
Authors' Addresses
Tirumaleswar Reddy.K
Nokia
India
Email: kondtir@gmail.com
Dan Wing
Citrix Systems, Inc.
4988 Great America Pkwy
Santa Clara, CA 95054
United States of America
Email: danwing@gmail.com
Blake Anderson
Cisco Systems, Inc.
170 West Tasman Dr
San Jose, CA 95134
United States of America
Email: blake.anderson@cisco.com
RFC TOTAL SIZE: 81483 bytes
PUBLICATION DATE: Friday, April 18th, 2025
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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