Manufacturer Usage Description Specification
draft-ietf-opsawg-mud-24
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8520.
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| Authors | Eliot Lear , Ralph Droms , Dan Romascanu | ||
| Last updated | 2018-06-04 | ||
| Replaces | draft-lear-ietf-netmod-mud | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Telechat review
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-20)
by Robert Sparks
Ready w/issues
GENART Early review
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by Robert Sparks
Almost ready
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Ready w/issues
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Joe Clarke | ||
| Shepherd write-up | Show Last changed 2017-10-10 | ||
| IESG | IESG state | Became RFC 8520 (Proposed Standard) | |
| Consensus boilerplate | Yes | ||
| Telechat date |
(None)
Needs 9 more YES or NO OBJECTION positions to pass. |
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| Responsible AD | Ignas Bagdonas | ||
| Send notices to | Joe Clarke <jclarke@cisco.com> | ||
| IANA | IANA review state | Version Changed - Review Needed |
draft-ietf-opsawg-mud-24
Internet-Draft Manufacturer Usage Descriptions June 2018 description "The name of the ACL for this entry."; } } } } augment "/acl:acls/acl:acl/acl:aces/acl:ace/acl:matches" { description "adding abstractions to avoid need of IP addresses"; container mud { description "MUD-specific matches."; leaf manufacturer { type inet:host; description "A domain that is intended to match the authority section of the MUD URL. This node is used to specify one or more manufacturers a device should be authorized to access."; } leaf same-manufacturer { type empty; description "This node matches the authority section of the MUD URL of a Thing. It is intended to grant access to all devices with the same authority section."; } leaf model { type inet:uri; description "Devices of the specified model type will match if they have an identical MUD URL."; } leaf local-networks { type empty; description "IP addresses will match this node if they are considered local addresses. A local address may be a list of locally defined prefixes and masks that indicate a particular administrative scope."; } leaf controller { type inet:uri; description "This node names a class that has associated with it zero or more IP addresses to match against. These may be scoped to a manufacturer or via a standard Lear, et al. Expires December 7, 2018 [Page 24] Internet-Draft Manufacturer Usage Descriptions June 2018 URN."; } leaf my-controller { type empty; description "This node matches one or more network elements that have been configured to be the controller for this Thing, based on its MUD URL."; } } } augment "/acl:acls/acl:acl/acl:aces/acl:ace/acl:matches" + "/acl:l4/acl:tcp/acl:tcp" { description "add direction-initiated"; leaf direction-initiated { type direction; description "This node matches based on which direction a connection was initiated. The means by which that is determined is discussed in this document."; } } } <CODE ENDS> 8. The Domain Name Extension to the ACL Model This module specifies an extension to IETF-ACL model such that domain names may be referenced by augmenting the "matches" node. Different implementations may deploy differing methods to maintain the mapping between IP address and domain name, if indeed any are needed. However, the intent is that resources that are referred to using a name should be authorized (or not) within an access list. The structure of the change is as follows: module: ietf-acldns augment /acl:acls/acl:acl/acl:aces/acl:ace/ acl:matches/acl:l3/acl:ipv4/acl:ipv4: +--rw src-dnsname? inet:host +--rw dst-dnsname? inet:host augment /acl:acls/acl:acl/acl:aces/acl:ace/ acl:matches/acl:l3/acl:ipv6/acl:ipv6: +--rw src-dnsname? inet:host +--rw dst-dnsname? inet:host Lear, et al. Expires December 7, 2018 [Page 25] Internet-Draft Manufacturer Usage Descriptions June 2018 The choice of these particular points in the access-list model is based on the assumption that we are in some way referring to IP- related resources, as that is what the DNS returns. A domain name in our context is defined in [RFC6991]. The augmentations are replicated across IPv4 and IPv6 to allow MUD file authors the ability to control the IP version that the Thing may utilize. The following node are defined. 8.1. src-dnsname The argument corresponds to a domain name of a source as specified by inet:host. A number of means may be used to resolve hosts. What is important is that such resolutions be consistent with ACLs required by Things to properly operate. 8.2. dst-dnsname The argument corresponds to a domain name of a destination as specified by inet:host See the previous section relating to resolution. Note when using either of these with a MUD file, because access is associated with a particular Thing, MUD files MUST NOT contain either a src-dnsname in an ACL associated with from-device-policy or a dst- dnsname associated with to-device-policy. 8.3. The ietf-acldns Model <CODE BEGINS>file "ietf-acldns@2018-06-05.yang" module ietf-acldns { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-acldns"; prefix ietf-acldns; import ietf-access-control-list { prefix acl; } import ietf-inet-types { prefix inet; } organization "IETF OPSAWG (Ops Area) Working Group"; contact "WG Web: http://tools.ietf.org/wg/opsawg/ WG List: opsawg@ietf.org Author: Eliot Lear Lear, et al. Expires December 7, 2018 [Page 26] Internet-Draft Manufacturer Usage Descriptions June 2018 lear@cisco.com Author: Ralph Droms rdroms@gmail.com Author: Dan Romascanu dromasca@gmail.com "; description "This YANG module defines a component that augments the IETF description of an access list to allow DNS names as matching criteria."; revision 2018-06-05 { description "Base version of dnsname extension of ACL model"; reference "RFC XXXX: Manufacturer Usage Description Specification"; } grouping dns-matches { description "Domain names for matching."; leaf src-dnsname { type inet:host; description "domain name to be matched against"; } leaf dst-dnsname { type inet:host; description "domain name to be matched against"; } } augment "/acl:acls/acl:acl/acl:aces/acl:ace/acl:matches" + "/acl:l3/acl:ipv4/acl:ipv4" { description "Adding domain names to matching"; uses dns-matches; } augment "/acl:acls/acl:acl/acl:aces/acl:ace/acl:matches" + "/acl:l3/acl:ipv6/acl:ipv6" { description "Adding domain names to matching"; uses dns-matches; } } <CODE ENDS> Lear, et al. Expires December 7, 2018 [Page 27] Internet-Draft Manufacturer Usage Descriptions June 2018 9. MUD File Example This example contains two access lists that are intended to provide outbound access to a cloud service on TCP port 443. { "ietf-mud:mud": { "mud-version": 1, "mud-url": "https://lighting.example.com/lightbulb2000", "last-update": "2018-03-02T11:20:51+01:00", "cache-validity": 48, "is-supported": true, "systeminfo": "The BMS Example Lightbulb", "from-device-policy": { "access-lists": { "access-list": [ { "name": "mud-76100-v6fr" } ] } }, "to-device-policy": { "access-lists": { "access-list": [ { "name": "mud-76100-v6to" } ] } } }, "ietf-access-control-list:acls": { "acl": [ { "name": "mud-76100-v6to", "type": "ipv6-acl-type", "aces": { "ace": [ { "name": "cl0-todev", "matches": { "ipv6": { "ietf-acldns:src-dnsname": "test.example.com", "protocol": 6 }, "tcp": { "ietf-mud:direction-initiated": "from-device", Lear, et al. Expires December 7, 2018 [Page 28] Internet-Draft Manufacturer Usage Descriptions June 2018 "source-port": { "operator": "eq", "port": 443 } } }, "actions": { "forwarding": "accept" } } ] } }, { "name": "mud-76100-v6fr", "type": "ipv6-acl-type", "aces": { "ace": [ { "name": "cl0-frdev", "matches": { "ipv6": { "ietf-acldns:dst-dnsname": "test.example.com", "protocol": 6 }, "tcp": { "ietf-mud:direction-initiated": "from-device", "destination-port": { "operator": "eq", "port": 443 } } }, "actions": { "forwarding": "accept" } } ] } } ] } } In this example, two policies are declared, one from the Thing and the other to the Thing. Each policy names an access list that applies to the Thing, and one that applies from. Within each access Lear, et al. Expires December 7, 2018 [Page 29] Internet-Draft Manufacturer Usage Descriptions June 2018 list, access is permitted to packets flowing to or from the Thing that can be mapped to the domain name of "service.bms.example.com". For each access list, the enforcement point should expect that the Thing initiated the connection. 10. The MUD URL DHCP Option The IPv4 MUD URL client option has the following format: +------+-----+------------------------------ | code | len | MUDstring +------+-----+------------------------------ Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single octet that indicates the length of MUD string in octets. The MUD string is defined as follows: MUDstring = mudurl [ " " reserved ] mudurl = URI; a URL [RFC3986] that uses the "https" schema [RFC7230] reserved = 1*( OCTET ) ; from [RFC5234] The entire option MUST NOT exceed 255 octets. If a space follows the MUD URL, a reserved string that will be defined in future specifications follows. MUD managers that do not understand this field MUST ignore it. The IPv6 MUD URL client option has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_MUD_URL_V6 | option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MUDstring | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OPTION_MUD_URL_V6 (112; assigned by IANA). option-length contains the length of the MUDstring, as defined above, in octets. The intent of this option is to provide both a new Thing classifier to the network as well as some recommended configuration to the routers that implement policy. However, it is entirely the purview Lear, et al. Expires December 7, 2018 [Page 30] Internet-Draft Manufacturer Usage Descriptions June 2018 of the network system as managed by the network administrator to decide what to do with this information. The key function of this option is simply to identify the type of Thing to the network in a structured way such that the policy can be easily found with existing toolsets. 10.1. Client Behavior A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit DHCPv6 option. These options are singletons, as specified in [RFC7227]. Because clients are intended to have at most one MUD URL associated with them, they may emit at most one MUD URL option via DHCPv4 and one MUD URL option via DHCPv6. In the case where both v4 and v6 DHCP options are emitted, the same URL MUST be used. 10.2. Server Behavior A DHCP server may ignore these options or take action based on receipt of these options. When a server consumes this option, it will either forward the URL and relevant client information (such as the gateway address or giaddr and requested IP address, and lease length) to a network management system, or it will retrieve the usage description itself by resolving the URL. DHCP servers may implement MUD functionality themselves or they may pass along appropriate information to a network management system or MUD manager. A DHCP server that does process the MUD URL MUST adhere to the process specified in [RFC2818] and [RFC5280] to validate the TLS certificate of the web server hosting the MUD file. Those servers will retrieve the file, process it, create and install the necessary configuration on the relevant network element. Servers SHOULD monitor the gateway for state changes on a given interface. A DHCP server that does not provide MUD functionality and has forwarded a MUD URL to a MUD manager MUST notify the MUD manager of any corresponding change to the DHCP state of the client (such as expiration or explicit release of a network address lease). Should the DHCP server fail, in the case when it implements the MUD manager functionality, any backup mechanisms SHOULD include the MUD state, and the server SHOULD resolve the status of clients upon its restart, similar to what it would do, absent MUD manager functionality. In the case where the DHCP server forwards information to the MUD manager, the MUD manager will either make use of redundant DHCP servers for information, or otherwise clear state based on other network information, such as monitoring port status on a switch via SNMP, Radius accounting, or similar mechanisms. Lear, et al. Expires December 7, 2018 [Page 31] Internet-Draft Manufacturer Usage Descriptions June 2018 10.3. Relay Requirements There are no additional requirements for relays. 11. The Manufacturer Usage Description (MUD) URL X.509 Extension This section defines an X.509 non-critical certificate extension that contains a single Uniform Resource Locator (URL) that points to an on-line Manufacturer Usage Description concerning the certificate subject. URI must be represented as described in Section 7.4 of [RFC5280]. Any Internationalized Resource Identifiers (IRIs) MUST be mapped to URIs as specified in Section 3.1 of [RFC3987] before they are placed in the certificate extension. The semantics of the URL are defined Section 6 of this document. The choice of id-pe is based on guidance found in Section 4.2.2 of [RFC5280]: These extensions may be used to direct applications to on-line information about the issuer or the subject. The MUD URL is precisely that: online information about the particular subject. In addition, a separate new extension is defined as id-pe-mudsigner. This contains the subject field of the signing certificate of the MUD file. Processing of this field is specified in Section 13.2. The purpose of this signature is to make a claim that the MUD file found on the server is valid for a given device, independent of any other factors. There are several security considerations below in Section 16. A new content-type id-ct-mud is also defined. While signatures are detached today, should a MUD file be transmitted as part of a CMS message, this content-type SHOULD be used. The new extension is identified as follows: <CODE BEGINS> MUDURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-mudURLExtn2016(88) } DEFINITIONS IMPLICIT TAGS ::= BEGIN Lear, et al. Expires December 7, 2018 [Page 32] Internet-Draft Manufacturer Usage Descriptions June 2018 -- EXPORTS ALL -- IMPORTS -- RFC 5912 EXTENSION FROM PKIX-CommonTypes-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkixCommon-02(57) } -- RFC 5912 id-ct FROM PKIXCRMF-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-crmf2005-02(55) } -- RFC 6268 CONTENT-TYPE FROM CryptographicMessageSyntax-2010 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-cms-2009(58) } -- RFC 5912 id-pe, Name FROM PKIX1Explicit-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-explicit-02(51) } ; -- -- Certificate Extensions -- MUDCertExtensions EXTENSION ::= { ext-MUDURL | ext-MUDsigner, ... } ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax IDENTIFIED BY id-pe-mud-url } id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 } MUDURLSyntax ::= IA5String ext-MUDsigner EXTENSION ::= { SYNTAX MUDsignerSyntax IDENTIFIED BY id-pe-mudsigner } Lear, et al. Expires December 7, 2018 [Page 33] Internet-Draft Manufacturer Usage Descriptions June 2018 id-pe-mudsigner OBJECT IDENTIFIER ::= { id-pe TBD } MUDsignerSyntax ::= Name -- -- CMS Content Types -- MUDContentTypes CONTENT-TYPE ::= { ct-mud, ... } ct-mud CONTENT-TYPE ::= { -- directly include the content IDENTIFIED BY id-ct-mudtype } -- The binary data that is in the form -- 'application/mud+json" is directly encoded as the -- signed data. No additional ASN.1 encoding is added. id-ct-mudtype OBJECT IDENTIFIER ::= { id-ct TBD } END <CODE ENDS> While this extension can appear in either an 802.AR manufacturer certificate (IDevID) or deployment certificate (LDevID), of course it is not guaranteed in either, nor is it guaranteed to be carried over. It is RECOMMENDED that MUD manager implementations maintain a table that maps a Thing to its MUD URL based on IDevIDs. 12. The Manufacturer Usage Description LLDP extension The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop vendor-neutral link layer protocol used by end hosts network Things for advertising their identity, capabilities, and neighbors on an IEEE 802 local area network. Its Type-Length-Value (TLV) design allows for 'vendor-specific' extensions to be defined. IANA has a registered IEEE 802 organizationally unique identifier (OUI) defined as documented in [RFC7042]. The MUD LLDP extension uses a subtype defined in this document to carry the MUD URL. The LLDP vendor specific frame has the following format: +--------+--------+----------+---------+-------------- |TLV Type| len | OUI |subtype | MUDString | =127 | |= 00 00 5E| = 1 | |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets) +--------+--------+----------+---------+-------------- Lear, et al. Expires December 7, 2018 [Page 34] Internet-Draft Manufacturer Usage Descriptions June 2018 where: o TLV Type = 127 indicates a vendor-specific TLV o len - indicates the TLV string length o OUI = 00 00 5E is the organizationally unique identifier of IANA o subtype = 1 (to be assigned by IANA for the MUD URL) o MUD URL - the length MUST NOT exceed 255 octets The intent of this extension is to provide both a new Thing classifier to the network as well as some recommended configuration to the routers that implement policy. However, it is entirely the purview of the network system as managed by the network administrator to decide what to do with this information. The key function of this extension is simply to identify the type of Thing to the network in a structured way such that the policy can be easily found with existing toolsets. Hosts, routers, or other network elements that implement this option are intended to have at most one MUD URL associated with them, so they may transmit at most one MUD URL value. Hosts, routers, or other network elements that implement this option may ignore these options or take action based on receipt of these options. For example they may fill in information in the respective extensions of the LLDP Management Information Base (LLDP MIB). LLDP operates in a one-way direction. LLDPDUs are not exchanged as information requests by one Thing and response sent by another Thing. The other Things do not acknowledge LLDP information received from a Thing. No specific network behavior is guaranteed. When a Thing consumes this extension, it may either forward the URL and relevant remote Thing information to a MUD manager, or it will retrieve the usage description by resolving the URL in accordance with normal HTTP semantics. 13. Creating and Processing of Signed MUD Files Because MUD files contain information that may be used to configure network access lists, they are sensitive. To ensure that they have not been tampered with, it is important that they be signed. We make use of DER-encoded Cryptographic Message Syntax (CMS) [RFC5652] for this purpose. Lear, et al. Expires December 7, 2018 [Page 35] Internet-Draft Manufacturer Usage Descriptions June 2018 13.1. Creating a MUD file signature A MUD file MUST be signed using CMS as an opaque binary object. In order to make successful verification more likely, intermediate certificates SHOULD be included. The signature is stored at the location specified in the MUD file. Signatures are transferred using content-type "application/pkcs7-signature". For example: % openssl cms -sign -signer mancertfile -inkey mankey \ -in mudfile -binary -outform DER -binary \ -certfile intermediatecert -out mudfile.p7s Note: A MUD file may need to be re-signed if the signature expires. 13.2. Verifying a MUD file signature Prior to processing the rest of a MUD file, the MUD manager MUST retrieve the MUD signature file by retrieving the value of "mud- signature" and validating the signature across the MUD file. The Key Usage Extension in the signing certificate MUST be present and have the bit digitalSignature(0) set. When the id-pe-mudsigner extension is present in a device's X.509 certificate, the MUD signature file MUST have been generated by a certificate whose subject matches the contents of that id-pe-mudsigner extension. If these conditions are not met, or if it cannot validate the chain of trust to a known trust anchor, the MUD manager MUST cease processing the MUD file until an administrator has given approval. The purpose of the signature on the file is to assign accountability to an entity, whose reputation can be used to guide administrators on whether or not to accept a given MUD file. It is already common place to check web reputation on the location of a server on which a file resides. While it is likely that the manufacturer will be the signer of the file, this is not strictly necessary, and may not be desirable. For one thing, in some environments, integrators may install their own certificates. For another, what is more important is the accountability of the recommendation, and not just the relationship between the Thing and the file. An example: % openssl cms -verify -in mudfile.p7s -inform DER -content mudfile Note the additional step of verifying the common trust root. Lear, et al. Expires December 7, 2018 [Page 36] Internet-Draft Manufacturer Usage Descriptions June 2018 14. Extensibility One of our design goals is to see that MUD files are able to be understood by as broad a cross-section of systems as is possible. Coupled with the fact that we have also chosen to leverage existing mechanisms, we are left with no ability to negotiate extensions and a limited desire for those extensions in any event. A such, a two-tier extensibility framework is employed, as follows: 1. At a coarse grain, a protocol version is included in a MUD URL. This memo specifies MUD version 1. Any and all changes are entertained when this version is bumped. Transition approaches between versions would be a matter for discussion in future versions. 2. At a finer grain, only extensions that would not incur additional risk to the Thing are permitted. Specifically, adding nodes to the mud container is permitted with the understanding that such additions will be ignored by unaware implementations. Any such extensions SHALL be standardized through the IETF process, and MUST be named in the "extensions" list. MUD managers MUST ignore YANG nodes they do not understand and SHOULD create an exception to be resolved by an administrator, so as to avoid any policy inconsistencies. 15. Deployment Considerations Because MUD consists of a number of architectural building blocks, it is possible to assemble different deployment scenarios. One key aspect is where to place policy enforcement. In order to protect the Thing from other Things within a local deployment, policy can be enforced on the nearest switch or access point. In order to limit unwanted traffic within a network, it may also be advisable to enforce policy as close to the Internet as possible. In some circumstances, policy enforcement may not be available at the closest hop. At that point, the risk of lateral infection (infection of devices that reside near one another) is increased to the number of Things that are able to communicate without protection. A caution about some of the classes: admission of a Thing into the "manufacturer" and "same-manufacturer" class may have impact on access of other Things. Put another way, the admission may grow the access-list on switches connected to other Things, depending on how access is managed. Some care should be given on managing that access-list growth. Alternative methods such as additional network segmentation can be used to keep that growth within reason. Lear, et al. Expires December 7, 2018 [Page 37] Internet-Draft Manufacturer Usage Descriptions June 2018 Because as of this writing MUD is a new concept, one can expect a great many devices to not have implemented it. It remains a local deployment decision as to whether a device that is first connected should be allowed broad or limited access. Furthermore, as mentioned in the introduction, a deployment may choose to ignore a MUD policy in its entirety, but simply taken into account the MUD URL as a classifier to be used as part of a local policy decision. Finally, please see directly below regarding device lifetimes and use of domain names. 16. Security Considerations Based on how a MUD URL is emitted, a Thing may be able to lie about what it is, thus gaining additional network access. This can happen in a number of ways when a device emits a MUD URL using DHCP or LLDP, such as being inappropriately admitted to a class such as "same- manufacturer", given access to a device such as "my-controller", or being permitted access to an Internet resource, where such access would otherwise be disallowed. Whether that is the case will depend on the deployment. Implementations SHOULD be configurable to disallow additive access for devices using MUD-URLs that are not emitted in a secure fashion such as in a certificate. Similarly, implementations SHOULD NOT grant elevated permissions (beyond those of devices presenting no MUD policy) to devices which do not strongly bind their identity to their L2/L3 transmissions. When insecure methods are used by the MUD Manager, the classes SHOULD NOT contain devices that use both insecure and secure methods, in order to prevent privilege escalation attacks, and MUST NOT contain devices with the same MUD-URL that are derived from both strong and weak authentication methods. Devices may forge source (L2/L3) information. Deployments should apply appropriate protections to bind communications to the authentication that has taken place. For 802.1X authentication, IEEE 802.1AE (MACsec) [IEEE8021AE] is one means by which this may happen. A similar approach can be used with 802.11i (WPA2) [IEEE80211i]. Other means are available with other lower layer technologies. Implementations using session-oriented access that is not cryptographically bound should take care to remove state when any form of break in the session is detected. A rogue CA may sign a certificate that contains the same subject name as is listed in the MUDsigner field in the manufacturer certificate, thus seemingly permitting a substitute MUD file for a device. There are two mitigations available: first, if the signer changes, this may be flagged as an exception by the MUD manager. If the MUD file also changes, the MUD manager SHOULD seek administrator approval (it Lear, et al. Expires December 7, 2018 [Page 38] Internet-Draft Manufacturer Usage Descriptions June 2018 should do this in any case). In all circumstances, the MUD manager MUST maintain a cache of trusted CAs for this purpose. When such a rogue is discovered, it SHOULD be removed. Additional mitigations are described below. When certificates are not present, Things claiming to be of a certain manufacturer SHOULD NOT be included in that manufacturer grouping without additional validation of some form. This will be relevant whenthe MUD manager makes use of primitives such as "manufacturer" for the purpose of accessing Things of a particular type. Similarly, network management systems may be able to fingerprint the Thing. In such cases, the MUD URL can act as a classifier that can be proven or disproven. Fingerprinting may have other advantages as well: when 802.1AR certificates are used, because they themselves cannot change, fingerprinting offers the opportunity to add artifacts to the MUD string in the form of the reserved field discussed in Section 10. The meaning of such artifacts is left as future work. MUD managers SHOULD NOT accept a usage description for a Thing with the same MAC address that has indicated a change of the URL authority without some additional validation (such as review by a network administrator). New Things that present some form of unauthenticated MUD URL SHOULD be validated by some external means when they would be be given increased network access. It may be possible for a rogue manufacturer to inappropriately exercise the MUD file parser, in order to exploit a vulnerability. There are three recommended approaches to address this threat. The first is to validate that the signer of the MUD file is known to and trusted by the MUD manager. The second is to have a system do a primary scan of the file to ensure that it is both parseable and believable at some level. MUD files will likely be relatively small, to start with. The number of ACEs used by any given Thing should be relatively small as well. It may also be useful to limit retrieval of MUD URLs to only those sites that are known to have decent web or domain reputations. Use of a URL necessitates the use of domain names. If a domain name changes ownership, the new owner of that domain may be able to provide MUD files that MUD managers would consider valid. There are a few approaches that can mitigate this attack. First, MUD managers SHOULD cache certificates used by the MUD file server. When a new certificate is retrieved for whatever reason, the MUD manager should check to see if ownership of the domain has changed. A fair programmatic approximation of this is when the name servers for the domain have changed. If the actual MUD file has changed, the MUD manager MAY check the WHOIS database to see if registration ownership Lear, et al. Expires December 7, 2018 [Page 39] Internet-Draft Manufacturer Usage Descriptions June 2018 of a domain has changed. If a change has occurred, or if for some reason it is not possible to determine whether ownership has changed, further review may be warranted. Note, this remediation does not take into account the case of a Thing that was produced long ago and only recently fielded, or the case where a new MUD manager has been installed. The release of a MUD URL by a Thing reveals what the Thing is, and provides an attacker with guidance on what vulnerabilities may be present. While the MUD URL itself is not intended to be unique to a specific Thing, the release of the URL may aid an observer in identifying individuals when combined with other information. This is a privacy consideration. In addressing both of these concerns, implementors should take into account what other information they are advertising through mechanisms such as mDNS[RFC6872], how a Thing might otherwise be identified, perhaps through how it behaves when it is connected to the network, whether a Thing is intended to be used by individuals or carry personal identifying information, and then apply appropriate data minimization techniques. One approach is to make use of TEAP [RFC7170] as the means to share information with authorized components in the network. Network elements may also assist in limiting access to the MUD URL through the use of mechanisms such as DHCPv6-Shield [RFC7610]. There is the risk of the MUD manager itself being spied on to determine what things are connected to the network. To address this risk, MUD managers may choose to make use of TLS proxies that they trust that would aggregate other information. Please note that the security considerations mentioned in Section 4.7 of [I-D.ietf-netmod-rfc6087bis] are not applicable in this case because the YANG serialization is not intended to be accessed via NETCONF. However, for those who try to instantiate this model in a network element via NETCONF, all objects in each model in this draft exhibit similar security characteristics as [I-D.ietf-netmod-acl-model]. The basic purpose of MUD is to configure access, and so by its very nature can be disruptive if used by unauthorized parties. 17. IANA Considerations [ There was originally a registry entry for .well-known suffixes. This has been removed from the draft and may be marked as deprecated in the registry. RFC Editor: please remove this comment. ] Lear, et al. Expires December 7, 2018 [Page 40] Internet-Draft Manufacturer Usage Descriptions June 2018 17.1. YANG Module Registrations The following YANG modules are requested to be registered in the "IANA Module Names" registry: The ietf-mud module: o Name: ietf-mud o URN: urn:ietf:params:xml:ns:yang:ietf-mud o Prefix: ietf-mud o Registrant conact: The IESG o Reference: [RFCXXXX] The ietf-acldns module: o Name: ietf-acldns o URI: urn:ietf:params:xml:ns:yang:ietf-acldns o Prefix: ietf-acldns o Registrant: the IESG o Reference: [RFCXXXX] 17.2. DHCPv4 and DHCPv6 Options The IANA has allocated option 161 in the Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry for the MUD DHCPv4 option, and option 112 for DHCPv6, as described in Section 10. 17.3. PKIX Extensions IANA is kindly requested to make the following assignments for: o The MUDURLExtnModule-2016 ASN.1 module in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). o id-pe-mud-url object identifier from the "SMI Security for PKIX Certificate Extension" registry (1.3.6.1.5.5.7.1). o id-pe-mudsigner object identifier from the "SMI Security for PKIX Certificate Extension" registry (TBD). Lear, et al. Expires December 7, 2018 [Page 41] Internet-Draft Manufacturer Usage Descriptions June 2018 o id-ct-mud object identifier from the "SMI Security for S/MIME CMS Content Type" registry. The use of these values is specified in Section 11. 17.4. MIME Media-type Registration for MUD files The following media-type is defined for transfer of MUD file: o Type name: application o Subtype name: mud+json o Required parameters: n/a o Optional parameters: n/a o Encoding considerations: 8bit; application/mud+json values are represented as a JSON object; UTF-8 encoding MUST be employed. [RFC3629] o Security considerations: See Security Considerations of RFCXXXX and [RFC8259] Section 12. o Interoperability considerations: n/a o Published specification: [RFCXXXX] o Applications that use this media type: MUD managers as specified by [RFCXXXX]. o Fragment identifier considerations: n/a o Additional information: Magic number(s): n/a File extension(s): n/a Macintosh file type code(s): n/a o Person & email address to contact for further information: Eliot Lear <lear@cisco.com>, Ralph Droms <rdroms@gmail.com> o Intended usage: COMMON o Restrictions on usage: none o Author: Eliot Lear <lear@cisco.com> Ralph Droms <rdroms@gmail.com> o Change controller: IESG o Provisional registration? (standards tree only): No. 17.5. LLDP IANA TLV Subtype Registry IANA is requested to create a new registry for IANA Link Layer Discovery Protocol (LLDP) TLV subtype values. The recommended policy for this registry is Expert Review. The maximum number of entries in the registry is 256. IANA is required to populate the initial registry with the value: Lear, et al. Expires December 7, 2018 [Page 42] Internet-Draft Manufacturer Usage Descriptions June 2018 LLDP subtype value = 1 (All the other 255 values should be initially marked as 'Unassigned'.) Description = the Manufacturer Usage Description (MUD) Uniform Resource Locator (URL) Reference = < this document > 17.6. The MUD Well Known Universal Resource Name (URNs) The following parameter registry is requested to be added in accordance with [RFC3553] Registry name: "urn:ietf:params:mud" is requested. Specification: this document Repository: this document Index value: Encoded identically to a TCP/UDP port service name, as specified in Section 5.1 of [RFC6335] The following entries should be added to the "urn:ietf:params:mud" name space: "urn:ietf:params:mud:dns" refers to the service specified by [RFC1123]. "urn:ietf:params:mud:ntp" refers to the service specified by [RFC5905]. 17.7. Extensions Registry The IANA is requested to establish a registry of extensions as follows: Registry name: MUD extensions registry Registry policy: Standards action Standard reference: document Extension name: UTF-8 encoded string, not to exceed 40 characters. Each extension MUST follow the rules specified in this specification. As is usual, the IANA issues early allocations based in accordance with [RFC7120]. 18. Acknowledgments The authors would like to thank Einar Nilsen-Nygaard, who singlehandedly updated the model to match the updated ACL model, Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm, John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk Birkholz, Adam Montville, Jim Schaad, and Robert Sparks for their valuable advice and reviews. Russ Housley entirely rewrote Lear, et al. Expires December 7, 2018 [Page 43] Internet-Draft Manufacturer Usage Descriptions June 2018 Section 11 to be a complete module. Adrian Farrel provided the basis for privacy considerations text. Kent Watsen provided a thorough review of the architecture and the YANG model. The remaining errors in this work are entirely the responsibility of the authors. 19. References 19.1. Normative References [I-D.ietf-netmod-acl-model] Jethanandani, M., Huang, L., Agarwal, S., and D. Blair, "Network Access Control List (ACL) YANG Data Model", draft-ietf-netmod-acl-model-19 (work in progress), April 2018. [IEEE8021AB] Institute for Electrical and Electronics Engineers, "IEEE Standard for Local and Metropolitan Area Networks-- Station and Media Access Control Connectivity Discovery", n.d.. [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, DOI 10.17487/RFC1123, October 1989, <https://www.rfc-editor.org/info/rfc1123>. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, DOI 10.17487/RFC2131, March 1997, <https://www.rfc-editor.org/info/rfc2131>. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, DOI 10.17487/RFC2818, May 2000, <https://www.rfc-editor.org/info/rfc2818>. [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2003, <https://www.rfc-editor.org/info/rfc3315>. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, <https://www.rfc-editor.org/info/rfc3629>. Lear, et al. Expires December 7, 2018 [Page 44] Internet-Draft Manufacturer Usage Descriptions June 2018 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. Levkowetz, Ed., "Extensible Authentication Protocol (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, <https://www.rfc-editor.org/info/rfc3748>. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, <https://www.rfc-editor.org/info/rfc3986>. [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, January 2005, <https://www.rfc-editor.org/info/rfc3987>. [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, <https://www.rfc-editor.org/info/rfc5234>. [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, <https://www.rfc-editor.org/info/rfc5280>. [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009, <https://www.rfc-editor.org/info/rfc5652>. [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, <https://www.rfc-editor.org/info/rfc5905>. [RFC5911] Hoffman, P. and J. Schaad, "New ASN.1 Modules for Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911, DOI 10.17487/RFC5911, June 2010, <https://www.rfc-editor.org/info/rfc5911>. [RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the Public Key Infrastructure Using X.509 (PKIX)", RFC 5912, DOI 10.17487/RFC5912, June 2010, <https://www.rfc-editor.org/info/rfc5912>. Lear, et al. Expires December 7, 2018 [Page 45] Internet-Draft Manufacturer Usage Descriptions June 2018 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. Cheshire, "Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry", BCP 165, RFC 6335, DOI 10.17487/RFC6335, August 2011, <https://www.rfc-editor.org/info/rfc6335>. [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, <https://www.rfc-editor.org/info/rfc6991>. [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 2014, <https://www.rfc-editor.org/info/rfc7120>. [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and S. Krishnan, "Guidelines for Creating New DHCPv6 Options", BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, <https://www.rfc-editor.org/info/rfc7227>. [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014, <https://www.rfc-editor.org/info/rfc7230>. [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014, <https://www.rfc-editor.org/info/rfc7231>. [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield: Protecting against Rogue DHCPv6 Servers", BCP 199, RFC 7610, DOI 10.17487/RFC7610, August 2015, <https://www.rfc-editor.org/info/rfc7610>. [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, <https://www.rfc-editor.org/info/rfc7950>. [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC 7951, DOI 10.17487/RFC7951, August 2016, <https://www.rfc-editor.org/info/rfc7951>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. Lear, et al. Expires December 7, 2018 [Page 46] Internet-Draft Manufacturer Usage Descriptions June 2018 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, <https://www.rfc-editor.org/info/rfc8259>. [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, <https://www.rfc-editor.org/info/rfc8340>. [RFC8348] Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A YANG Data Model for Hardware Management", RFC 8348, DOI 10.17487/RFC8348, March 2018, <https://www.rfc-editor.org/info/rfc8348>. 19.2. Informative References [FW95] Chapman, D. and E. Zwicky, "Building Internet Firewalls", January 1995. [I-D.ietf-netmod-rfc6087bis] Bierman, A., "Guidelines for Authors and Reviewers of YANG Data Model Documents", draft-ietf-netmod-rfc6087bis-20 (work in progress), March 2018. [IEEE80211i] Institute for Electrical and Electronics Engineers, "IEEE Standard for information technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements-Part 11- Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications- Amendment 6- Medium Access Control (MAC) Security Enhancements", 2004. [IEEE8021AE] Institute for Electrical and Electronics Engineers, "IEEE Standard for Local and Metropolitan Area Networks- Media Access Control (MAC) Security", 2006. [IEEE8021AR] Institute for Electrical and Electronics Engineers, "Secure Device Identity", 1998. [IEEE8021X] Institute for Electrical and Electronics Engineers, "IEEE Standard for Local and metropolitan area networks--Port- Based Network Access Control", 2010. Lear, et al. Expires December 7, 2018 [Page 47] Internet-Draft Manufacturer Usage Descriptions June 2018 [ISO.8601.1988] International Organization for Standardization, "Data elements and interchange formats - Information interchange - Representation of dates and times", ISO Standard 8601, June 1988. [RFC1984] IAB and IESG, "IAB and IESG Statement on Cryptographic Technology and the Internet", BCP 200, RFC 1984, DOI 10.17487/RFC1984, August 1996, <https://www.rfc-editor.org/info/rfc1984>. [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, <https://www.rfc-editor.org/info/rfc3339>. [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An IETF URN Sub-namespace for Registered Protocol Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June 2003, <https://www.rfc-editor.org/info/rfc3553>. [RFC6092] Woodyatt, J., Ed., "Recommended Simple Security Capabilities in Customer Premises Equipment (CPE) for Providing Residential IPv6 Internet Service", RFC 6092, DOI 10.17487/RFC6092, January 2011, <https://www.rfc-editor.org/info/rfc6092>. [RFC6872] Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur, H., and O. Festor, "The Common Log Format (CLF) for the Session Initiation Protocol (SIP): Framework and Information Model", RFC 6872, DOI 10.17487/RFC6872, February 2013, <https://www.rfc-editor.org/info/rfc6872>. [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and IETF Protocol and Documentation Usage for IEEE 802 Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042, October 2013, <https://www.rfc-editor.org/info/rfc7042>. [RFC7170] Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna, "Tunnel Extensible Authentication Protocol (TEAP) Version 1", RFC 7170, DOI 10.17487/RFC7170, May 2014, <https://www.rfc-editor.org/info/rfc7170>. [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained Application Protocol (CoAP)", RFC 7252, DOI 10.17487/RFC7252, June 2014, <https://www.rfc-editor.org/info/rfc7252>. Lear, et al. Expires December 7, 2018 [Page 48] Internet-Draft Manufacturer Usage Descriptions June 2018 [RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson, "Architectural Considerations in Smart Object Networking", RFC 7452, DOI 10.17487/RFC7452, March 2015, <https://www.rfc-editor.org/info/rfc7452>. [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. Reddy, "Port Control Protocol (PCP) Server Selection", RFC 7488, DOI 10.17487/RFC7488, March 2015, <https://www.rfc-editor.org/info/rfc7488>. [RFC8343] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, <https://www.rfc-editor.org/info/rfc8343>. Appendix A. Changes from Earlier Versions RFC Editor to remove this section prior to publication. Draft -19: * Edits after discussion with apps area to address reserved field for the future. * Correct systeminfo to be utf8. * Remove "hardware-rev" from list. Draft -18: * Correct an error in the augment statement * Changes to the ACL model re ports. Draft -17: o One editorial. Draft -16 o add mud-signature element based on review comments o redo mud-url o make clear that systeminfo uses UTF8 Draft -13 to -14: o Final WGLC comments and review comments o Move version from MUD-URL to Model o Have MUD-URL in model o Update based on update to draft-ietf-netmod-acl-model o Point to tree diagram draft instead of 6087bis. Lear, et al. Expires December 7, 2018 [Page 49] Internet-Draft Manufacturer Usage Descriptions June 2018 Draft -12 to -13: o Additional WGLC comments Draft -10 to -12: These are based on WGLC comments: o Correct examples based on ACL model changes. o Change ordering nodes. o Additional explanatory text around systeminfo. o Change ordering in examples. o Make it VERY VERY VERY VERY clear that these are recommendations, not mandates. o DHCP -> NTP in some of the intro text. o Remove masa-server o "Things" to "network elements" in a few key places. o Reference to JSON YANG RFC added. Draft -10 to -11: o Example corrections o Typo o Fix two lists. o Addition of 'any-acl' and 'mud-acl' in the list of allowed features. o Clarification of what should be in a MUD file. Draft -09 to -10: o AD input. o Correct dates. o Add compliance sentence as to which ACL module features are implemented. Lear, et al. Expires December 7, 2018 [Page 50] Internet-Draft Manufacturer Usage Descriptions June 2018 Draft -08 to -09: o Resolution of Security Area review, IoT directorate review, GenART review, YANG doctors review. o change of YANG structure to address mandatory nodes. o Terminology cleanup. o specify out extra portion of MUD-URL. o consistency changes. o improved YANG descriptions. o Remove extra revisions. o Track ACL model changes. o Additional cautions on use of ACL model; further clarifications on extensions. Draft -07 to -08: o a number of editorials corrected. o definition of MUD file tweaked. Draft -06 to -07: o Examples updated. o Additional clarification for direction-initiated. o Additional implementation guidance given. Draft -06 to -07: o Update models to match new ACL model o extract directionality from the ACL, introducing a new device container. Draft -05 to -06: o Make clear that this is a component architecture (Polk and Watson) o Add order of operations (Watson) Lear, et al. Expires December 7, 2018 [Page 51] Internet-Draft Manufacturer Usage Descriptions June 2018 o Add extensions leaf-list (Pritikin) o Remove previous-mud-file (Watson) o Modify text in last-update (Watson) o Clarify local networks (Weis, Watson) o Fix contact info (Watson) o Terminology clarification (Weis) o Advice on how to handle LDevIDs (Watson) o Add deployment considerations (Watson) o Add some additional text about fingerprinting (Watson) o Appropriate references to 6087bis (Watson) o Change systeminfo to a URL to be referenced (Lear) Draft -04 to -05: * syntax error correction Draft -03 to -04: * Re-add my-controller Draft -02 to -03: * Additional IANA updates * Format correction in YANG. * Add reference to TEAP. Draft -01 to -02: * Update IANA considerations * Accept Russ Housley rewrite of X.509 text * Include privacy considerations text * Redo the URL limit. Still 255 bytes, but now stated in the URL definition. * Change URI registration to be under urn:ietf:params Draft -00 to -01: * Fix cert trust text. * change supportInformation to meta-info * Add an informational element in. * add urn registry and create first entry * add default elements Appendix B. Default MUD nodes What follows is the portion of a MUD file that permits DNS traffic to a controller that is registered with the URN "urn:ietf:params:mud:dns" and traffic NTP to a controller that is registered "urn:ietf:params:mud:ntp". This is considered the default behavior and the ACEs are in effect appended to whatever other "ace" entries that a MUD file contains. To block DNS or NTP one repeats the matching statement but replaces the "forwarding" action "accept" with "drop". Because ACEs are processed in the order they are Lear, et al. Expires December 7, 2018 [Page 52] Internet-Draft Manufacturer Usage Descriptions June 2018 received, the defaults would not be reached. A MUD manager might further decide to optimize to simply not include the defaults when they are overridden. Four "acl" list entries that implement default MUD nodes are listed below. Two are for IPv4 and two are for IPv6 (one in each direction for both versions of IP). Note that neither access-list name nor ace name need be retained or used in any way by local implementations, but are simply there for completeness' sake. "ietf-access-control-list:acls": { "acl": [ { "name": "mud-59776-v4to", "type": "ipv4-acl-type", "aces": { "ace": [ { "name": "ent0-todev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:dns" }, "ipv4": { "protocol": 17 }, "udp": { "source-port": { "operator": "eq", "port": 53 } } }, "actions": { "forwarding": "accept" } }, { "name": "ent1-todev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:ntp" }, "ipv4": { "protocol": 17 }, "udp": { "source-port": { Lear, et al. Expires December 7, 2018 [Page 53] Internet-Draft Manufacturer Usage Descriptions June 2018 "operator": "eq", "port": 123 } } }, "actions": { "forwarding": "accept" } } ] } }, { "name": "mud-59776-v4fr", "type": "ipv4-acl-type", "aces": { "ace": [ { "name": "ent0-frdev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:dns" }, "ipv4": { "protocol": 17 }, "udp": { "destination-port": { "operator": "eq", "port": 53 } } }, "actions": { "forwarding": "accept" } }, { "name": "ent1-frdev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:ntp" }, "ipv4": { "protocol": 17 }, "udp": { "destination-port": { Lear, et al. Expires December 7, 2018 [Page 54] Internet-Draft Manufacturer Usage Descriptions June 2018 "operator": "eq", "port": 123 } } }, "actions": { "forwarding": "accept" } } ] } }, { "name": "mud-59776-v6to", "type": "ipv6-acl-type", "aces": { "ace": [ { "name": "ent0-todev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:dns" }, "ipv6": { "protocol": 17 }, "udp": { "source-port": { "operator": "eq", "port": 53 } } }, "actions": { "forwarding": "accept" } }, { "name": "ent1-todev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:ntp" }, "ipv6": { "protocol": 17 }, "udp": { "source-port": { Lear, et al. Expires December 7, 2018 [Page 55] Internet-Draft Manufacturer Usage Descriptions June 2018 "operator": "eq", "port": 123 } } }, "actions": { "forwarding": "accept" } } ] } }, { "name": "mud-59776-v6fr", "type": "ipv6-acl-type", "aces": { "ace": [ { "name": "ent0-frdev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:dns" }, "ipv6": { "protocol": 17 }, "udp": { "destination-port": { "operator": "eq", "port": 53 } } }, "actions": { "forwarding": "accept" } }, { "name": "ent1-frdev", "matches": { "ietf-mud:mud": { "controller": "urn:ietf:params:mud:ntp" }, "ipv6": { "protocol": 17 }, "udp": { "destination-port": { Lear, et al. Expires December 7, 2018 [Page 56] Internet-Draft Manufacturer Usage Descriptions June 2018 "operator": "eq", "port": 123 } } }, "actions": { "forwarding": "accept" } } ] } } ] } Appendix C. A Sample Extension: DETNET-indicator In this sample extension we augment the core MUD model to indicate whether the device implements DETNET. If a device claims not to use DETNET, but then later attempts to do so, a notification or exception might be generated. Note that this example is intended only for illustrative purposes. Extension Name: "Example-Extension" (to be used in the extensions list) Standard: this document (but do not register the example) This extension augments the MUD model to include a single node, using the following sample module that has the following tree structure: module: ietf-mud-detext-example augment /ietf-mud:mud: +--rw is-detnet-required? boolean The model is defined as follows: <CODE BEGINS>file "ietf-mud-detext-example@2018-06-05.yang" module ietf-mud-detext-example { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-mud-detext-example"; prefix ietf-mud-detext-example; import ietf-mud { prefix ietf-mud; } Lear, et al. Expires December 7, 2018 [Page 57] Internet-Draft Manufacturer Usage Descriptions June 2018 organization "IETF OPSAWG (Ops Area) Working Group"; contact "WG Web: http://tools.ietf.org/wg/opsawg/ WG List: opsawg@ietf.org Author: Eliot Lear lear@cisco.com Author: Ralph Droms rdroms@gmail.com Author: Dan Romascanu dromasca@gmail.com "; description "Sample extension to a MUD module to indicate a need for DETNET support."; revision 2018-06-05 { description "Initial revision."; reference "RFC XXXX: Manufacturer Usage Description Specification"; } augment "/ietf-mud:mud" { description "This adds a simple extension for a manufacturer to indicate whether DETNET is required by a device."; leaf is-detnet-required { type boolean; description "This value will equal true if a device requires detnet to properly function"; } } } <CODE ENDS> Using the previous example, we now show how the extension would be expressed: { "ietf-mud:mud": { "mud-version": 1, "mud-url": "https://lighting.example.com/lightbulb2000", "last-update": "2018-03-02T11:20:51+01:00", Lear, et al. Expires December 7, 2018 [Page 58] Internet-Draft Manufacturer Usage Descriptions June 2018 "cache-validity": 48, "extensions": [ "ietf-mud-detext-example" ], "ietf-mud-detext-example:is-detnet-required": "false", "is-supported": true, "systeminfo": "The BMS Example Lightbulb", "from-device-policy": { "access-lists": { "access-list": [ { "name": "mud-76100-v6fr" } ] } }, "to-device-policy": { "access-lists": { "access-list": [ { "name": "mud-76100-v6to" } ] } } }, "ietf-access-control-list:acls": { "acl": [ { "name": "mud-76100-v6to", "type": "ipv6-acl-type", "aces": { "ace": [ { "name": "cl0-todev", "matches": { "ipv6": { "ietf-acldns:src-dnsname": "test.example.com", "protocol": 6 }, "tcp": { "ietf-mud:direction-initiated": "from-device", "source-port": { "operator": "eq", "port": 443 } } }, Lear, et al. Expires December 7, 2018 [Page 59] Internet-Draft Manufacturer Usage Descriptions June 2018 "actions": { "forwarding": "accept" } } ] } }, { "name": "mud-76100-v6fr", "type": "ipv6-acl-type", "aces": { "ace": [ { "name": "cl0-frdev", "matches": { "ipv6": { "ietf-acldns:dst-dnsname": "test.example.com", "protocol": 6 }, "tcp": { "ietf-mud:direction-initiated": "from-device", "destination-port": { "operator": "eq", "port": 443 } } }, "actions": { "forwarding": "accept" } } ] } } ] } } Authors' Addresses Lear, et al. Expires December 7, 2018 [Page 60] Internet-Draft Manufacturer Usage Descriptions June 2018 Eliot Lear Cisco Systems Richtistrasse 7 Wallisellen CH-8304 Switzerland Phone: +41 44 878 9200 Email: lear@cisco.com Ralph Droms Google 355 Main St., 5th Floor Cambridge Phone: +1 978 376 3731 Email: rdroms@gmail.com Dan Romascanu Phone: +972 54 5555347 Email: dromasca@gmail.com Lear, et al. Expires December 7, 2018 [Page 61]