Network Working Group E. Lear
Internet-Draft Cisco Systems
Intended status: Standards Track R. Droms
Expires: January 4, 2018
D. Romascanu
July 03, 2017
Manufacturer Usage Description Specification
draft-ietf-opsawg-mud-07
Abstract
This memo specifies a component-based architecture for manufacturer
usage descriptions (MUD). This includes two YANG modules, IPv4 and
IPv6 DHCP options, an LLDP TLV, a URL suffix specification, an X.509
certificate extension and a means to sign and verify the
descriptions.
Status of This Memo
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This Internet-Draft will expire on January 4, 2018.
Copyright Notice
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. What MUD doesn't do . . . . . . . . . . . . . . . . . . . 4
1.2. A Simple Example . . . . . . . . . . . . . . . . . . . . 4
1.3. Determining Intended Use . . . . . . . . . . . . . . . . 5
1.4. Finding A Policy: The MUD URL . . . . . . . . . . . . . . 5
1.5. Types of Policies . . . . . . . . . . . . . . . . . . . . 6
1.6. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
1.7. The Manufacturer Usage Description Architecture . . . . . 8
1.8. Order of operations . . . . . . . . . . . . . . . . . . . 9
2. The MUD Model and Semantic Meaning . . . . . . . . . . . . . 9
3. Element Definitions . . . . . . . . . . . . . . . . . . . . . 11
3.1. last-update . . . . . . . . . . . . . . . . . . . . . . . 11
3.2. cache-validity . . . . . . . . . . . . . . . . . . . . . 11
3.3. masa-server . . . . . . . . . . . . . . . . . . . . . . . 12
3.4. is-supported . . . . . . . . . . . . . . . . . . . . . . 12
3.5. systeminfo . . . . . . . . . . . . . . . . . . . . . . . 12
3.6. extensions . . . . . . . . . . . . . . . . . . . . . . . 12
3.7. packet-direction . . . . . . . . . . . . . . . . . . . . 12
3.8. manufacturer . . . . . . . . . . . . . . . . . . . . . . 12
3.9. same-manufacturer . . . . . . . . . . . . . . . . . . . . 13
3.10. model . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.11. local-networks . . . . . . . . . . . . . . . . . . . . . 13
3.12. controller . . . . . . . . . . . . . . . . . . . . . . . 13
3.13. my-controller . . . . . . . . . . . . . . . . . . . . . . 13
3.14. direction-initiated . . . . . . . . . . . . . . . . . . . 13
4. Processing of the MUD file . . . . . . . . . . . . . . . . . 14
5. What does a MUD URL look like? . . . . . . . . . . . . . . . 14
6. The MUD YANG Model . . . . . . . . . . . . . . . . . . . . . 15
7. The Domain Name Extension to the ACL Model . . . . . . . . . 20
7.1. source-dnsname . . . . . . . . . . . . . . . . . . . . . 21
7.2. destination-dnsname . . . . . . . . . . . . . . . . . . . 21
7.3. The ietf-acldns Model . . . . . . . . . . . . . . . . . . 21
8. MUD File Example . . . . . . . . . . . . . . . . . . . . . . 22
9. The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . . 24
9.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 25
9.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 25
9.3. Relay Requirements . . . . . . . . . . . . . . . . . . . 26
10. The Manufacturer Usage Description (MUD) URL X.509 Extension 26
11. The Manufacturer Usage Description LLDP extension . . . . . . 27
12. Creating and Processing of Signed MUD Files . . . . . . . . . 29
12.1. Creating a MUD file signature . . . . . . . . . . . . . 29
12.2. Verifying a MUD file signature . . . . . . . . . . . . . 29
13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 30
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14. Deployment Considerations . . . . . . . . . . . . . . . . . . 30
15. Security Considerations . . . . . . . . . . . . . . . . . . . 31
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
16.1. YANG Module Registrations . . . . . . . . . . . . . . . 32
16.2. DHCPv4 and DHCPv6 Options . . . . . . . . . . . . . . . 33
16.3. PKIX Extensions . . . . . . . . . . . . . . . . . . . . 33
16.4. Well Known URI Suffix . . . . . . . . . . . . . . . . . 33
16.5. MIME Media-type Registration for MUD files . . . . . . . 33
16.6. LLDP IANA TLV Subtype Registry . . . . . . . . . . . . . 34
16.7. The MUD Well Known Universal Resource Name (URNs) . . . 35
17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 35
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
18.1. Normative References . . . . . . . . . . . . . . . . . . 35
18.2. Informative References . . . . . . . . . . . . . . . . . 38
Appendix A. Changes from Earlier Versions . . . . . . . . . . . 39
Appendix B. Default MUD elements . . . . . . . . . . . . . . . . 40
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45
1. Introduction
The Internet has largely been constructed on general purpose
computers; those devices that may be used for a purpose that is
specified by those who buy the device. [RFC1984] presumed that an
end device would be most capable of protecting itself. This made
sense when the typical device was a workstation or a mainframe, and
it continues to make sense for general purpose computing devices
today, including laptops, smart phones, and tablets.
[RFC7452] discusses design patterns for, and poses questions about,
smart objects. Let us then posit a group of objects that are
specifically NOT general purpose computers. These devices therefore
have a purpose to their use. By definition, therefore, all other
purposes are NOT intended. The combination of these two statements
can be restated as a manufacturer usage description (MUD) that can be
applied at various points within a network. Although this memo may
seem to stress access requirements, usage intent also consists of
quality of service needs a device may have.
We use the notion of "manufacturer" loosely in this context, to
simply mean the entity or organization that will state how a device
is intended to be used. In the context of a lightbulb, this might
indeed be the lightbulb manufacturer. In the context of a smarter
device that has a built in Linux stack, it might be integrator of
that device. The key points are that the device itself is expected
to serve a limited purpose, and that there may exist an organization
in the supply chain of that device that will take responsibility for
informing the network about that purpose.
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The intent of MUD is to therefore solve for the following problems:
o Substantially reduce the threat surface on a device entering a
network to those communications intended by the manufacturer.
o Provide for a means to scale network policies to the ever-
increasing number types of devices in the network.
o Provide a means to address at least some vulnerabilities in a way
that is faster than it might take to update systems. This will be
particularly true for systems that are no longer supported by
their manufacturer.
o Keep the cost of implementation of such a system to the bare
minimum.
MUD therefore consists of three architectural building blocks: - A
classifier that a device emits that can be used to locate a
description; - The description itself, including how it is
interpreted, and; - A means to retrieve the description.
In this specification we specify each of these building blocks and
how they are intended to be used together. However, they may also be
used separately, independent of this specification by enterprise
networks for their own purposes.
1.1. What MUD doesn't do
General computing systems will benefit very little from MUD, as their
manufacturers cannot envision a specific communication pattern to
describe. In addition, even those devices that have a single or
small number of uses might have very broad communication patterns.
MUD is not for them either.
No matter how good a MUD-enabled network is, it will never replace
the need for manufacturers to patch vulnerabilities. It may,
however, provide network administrators with some additional
protection when those vulnerabilities exist.
1.2. A Simple Example
A light bulb is intended to light a room. It may be remotely
controlled through the network; and it may make use of a rendezvous
service of some form that an app on smart phone accesses. What we
can say about that light bulb, then, is that all other network access
is unwanted. It will not contact a news service, nor speak to the
refrigerator, and it has no need of a printer or other devices. It
has no Facebook friends. Therefore, an access list applied to it
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that states that it will only connect to the single rendezvous
service will not impede the light bulb in performing its function,
while at the same time allowing the network to provide both it and
other devices an additional layer of protection.
1.3. Determining Intended Use
The notion of intended use is in itself not new. Network
administrators apply access lists every day to allow for only such
use. This notion of white listing was well described by Chapman and
Zwicky in [FW95]. Programmatically profiling systems have existed
for years as well. These systems make use of heuristics that take at
least some time to assert what a system is.
A system could just as easily tell the network what sort of
protection it requires without going into what sort of system it is.
This would, in effect, be the converse of [RFC7488]. In seeking a
general purpose solution, however, we assume that a device has so few
capabilities that it will implement the least necessary capabilities
to function properly. This is a basic economic constraint. Unless
the network would refuse access to such a device, its developers
would have no reason to implement such an approach. To date, such an
assertion has held true.
1.4. Finding A Policy: The MUD URL
Our work begins, therefore, with the device emitting a Universal
Resource Locator (URL) [RFC3986]. This URL may serves both to
classify the device type and to provide a means to locate a policy
file.
In this memo three means are defined to emit the MUD URL. One is a
DHCP option[RFC2131],[RFC3315] that the DHCP client uses to inform
the DHCP server. The DHCP server may take further actions, such as
retrieve the URL or otherwise pass it along to network management
system or controller. The other method defined is an X.509
constraint. The IEEE has developed [IEEE8021AR] that provides a
certificate-based approach to communicate device characteristics,
which itself relies on [RFC5280]. The MUD URL extension is non-
critical, as required by IEEE 802.1AR. Various means may be used to
communicate that certificate, including Tunnel Extensible
Authentication Protocol (TEAP) [RFC7170]. Finally, a Link Layer
Discovery Protocol (LLDP) frame is defined [IEEE8021AB].
It is possible that there may be other means for a MUD URL to be
learned by a network. For instance, if a device has a serial number,
it may be possible for the MUD controller to perform a lookup of the
device, if it has some knowledge as to who the device manufacturer
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is, and what its MUD file server is. Such mechanisms are not
described in this memo, but are possible.
1.5. Types of Policies
When the MUD URL is resolved, the MUD controller retrieves a file
that describes what sort of communications a device is designed to
have. The manufacturer may specify either specific hosts for cloud
based services or certain classes for access within an operational
network. An example of a class might be "devices of a specified
manufacturer type", where the manufacturer type itself is indicated
simply by the authority component (e.g, the domain name) of the MUD
URL. Another example might to allow or disallow local access. Just
like other policies, these may be combined. For example:
Allow access to devices of the same manufacturer
Allow access to and from controllers who need to speak COAP
Allow access to local DNS/DHCP
Deny all other access
To add a bit more depth that should not be a stretch of anyone's
imagination, one could also make use of port-based access lists.
Thus a printer might have a description that states:
Allow access for port IPP or port LPD
Allow local access for port HTTP
Deny all other access
In this way anyone can print to the printer, but local access would
be required for the management interface.
The files that are retrieved are intended to be closely aligned to
existing network architectures so that they are easy to deploy. We
make use of YANG [RFC6020] because of the time and effort spent to
develop accurate and adequate models for use by network devices.
JSON is used as a serialization for compactness and readability,
relative to XML.
While the policy examples given here focus on access control, this is
not intended to be the sole focus. By structuring the model
described in this document with clear extension points, and by
leveraging YANG-based models, we provide the opportunity for new
policies to be introduced as required.
The YANG modules specified here are extensions of
[I-D.ietf-netmod-acl-model]. The extensions to this model allow for
a manufacturer to express classes of systems that a manufacturer
would find necessary for the proper function of the device. Two
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modules are specified. The first module specifies a means for domain
names to be used in ACLs so that devices that have their controllers
in the cloud may be appropriately authorized with domain names, where
the mapping of those names to addresses may rapidly change.
The other module abstracts away IP addresses into certain classes
that are instantiated into actual IP addresses through local
processing. Through these classes, manufacturers can specify how the
device is designed to communicate, so that network elements can be
configured by local systems that have local topological knowledge.
That is, the deployment populates the classes that the manufacturer
specifies. The abstractions are as follows:
Manufacturer: A device made by a particular manufacturer, as
identified by the authority component of its MUD-URL
same-manufacturer: Devices that have the same authority component of
their MUD-URL.
Controller: A device that the local network administrator admits to
the particular class.
my-controller: A class associated with the MUD-URL of a device that
the administrator admits.
The "manufacturer" classes can be easily specified by the
manufacturer, whereas controller classes are initially envisioned to
be specified by the administrator.
Because manufacturers do not know who will be using their devices, it
is important for functionality referenced in usage descriptions to be
relatively ubiquitous, and therefore, mature. Therefore, only a a
limited subset YANG-based configuration of is permitted in a MUD
file.
1.6. Terminology
MUD: manufacturer usage description.
MUD file: a file containing YANG-based JSON that describes a
recommended behavior.
MUD file server: a web server that hosts a MUD file.
MUD controller: the system that requests and receives the MUD file
from the MUD server. After it has processed a MUD file it may
direct changes to relevant network elements.
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MUD URL: a URL that can be used by the MUD controller to receive the
MUD file.
Thing: the end device that emits a MUD URL.
Manufacturer: the entity that configures the Thing to emit the MUD
URL and the one who asserts a recommendation in a MUD file. The
manufacturer might not always be the entity that constructs a
device. It could, for instance, be a systems integrator, or even
a component provider.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.7. The Manufacturer Usage Description Architecture
With these components laid out we now have the basis for an
archicture. This leads us to ASCII art.
.........................................
. ____________ . _____________
. | | . | |
. | MUD |----->get URL->| MUD |
. | Controller | .(https) | File Server |
. End system network |____________|<--MUD file<--<|_____________|
. . .
. . .
. _______ _________ .
.| | (dhcp et al) | router | .
.| Thing |---->MUD URL-->| or | .
.|_______| | switch | .
. |_________| .
.........................................
Figure 1: MUD Architecture
In the above diagram, the switch or router collects MUD URLs and
forwards them to the network management system for processing. This
happens in different ways, depending on how the URI is communicated.
For instance, in the case of DHCP, the DHCP server might receive the
URI and then process it. In the case of IEEE 802.1X, the switch
would carry the URI via a certificate to the authentication server
via EAP over Radius[RFC3748], which would then process it. One
method to do this is TEAP, described in [RFC7170]. The certificate
extension is described below.
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The information returned by the web site is valid for the duration of
the device's connection, or as specified in the description. Thus if
the device is mobile, when it moves on, any configuration in the
switch is removed. Similarly, from time to time the description may
be refreshed, based on new capabilities or communication patterns or
vulnerabilities.
The web site is typically run by or on behalf of the manufacturer.
Its domain name is that of the authority found in the MUD URL. For
legacy cases where Things cannot emit a URL, if the switch is able to
determine the appropriate URI, it may proxy it, the trivial cases
being a map between some registered device or port and a URL.
1.8. Order of operations
As mentioned above, MUD contains architectural building blocks, and
so order of operation may vary. However, here is one clear intended
example:
1. Device emits URL.
2. That URL is forwarded to a MUD controller by the nearest switch
(how this happens depends on the way in which the MUD URL is
emitted).
3. The MUD controller retrieves the MUD file from the MUD file
server, assuming it doesn't already have a copy. It may test the
URL against a reputation service, and it may test any hosts
within the file against reputation services, as it deems fit.
4. The MUD controller may query the administrator for permission to
add the device and associated policy. If the device is known or
the device type is known, it may skip this step.
5. The MUD controller instantiates local configuration based on the
abstractions defined in this document.
6. The MUD controller configures the switch nearest the device.
Other systems may be configured as well.
7. When the device disconnects, policy is removed.
2. The MUD Model and Semantic Meaning
A MUD file consists of JSON based on a YANG model. For purposes of
MUD, the elements that can be modified are access lists as augmented
by this model. The MUD file is limited to the serialization of a
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small number of YANG schema, including the models specified in the
following documents:
o [I-D.ietf-netmod-acl-model]
o [RFC6991]
Publishers of MUD files MUST NOT include other elements except as
described in Section 3.6, and MUST only contain information relevant
to the device being described. Devices parsing MUD files MUST cease
processing if they find other elements.
======= This module is structured into four parts:
o The first container, metainfo, holds information that is relevant
to retrieval and validity of the MUD file itself.
o The second container, device, describes the policies to be applied
to traffic to and from the device. The only policy currently
defined is a list of access control lists, but the from-device-
policy and to-device-policy containers serve as extension points
for subsequent augmentation.
o The third container augments the matching container of the ACL
model to add several elements that are relevant to the MUD URL, or
other otherwise abstracted for use within a local environment.
o The fourth container augments the tcp-acl container of the ACL
model to add the ability to match on the direction of initiation
of a TCP connection.
A simplified graphical representation of the data models is used in
this document. The meaning of the symbols in these diagrams is
defined in [I-D.ietf-netmod-rfc6087bis].
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module: ietf-mud
+--rw metainfo
| +--rw last-update? yang:date-and-time
| +--rw cache-validity? uint8
| +--rw masa-server? inet:uri
| +--rw is-supported? boolean
| +--rw systeminfo? inet:uri
| +--rw extensions* string
+--rw device
+--rw from-device-policy
| +--rw access-lists
| +--rw access-list* [acl-name acl-type]
| +--rw acl-name -> /acl:access-lists/acl/acl-name
| +--rw acl-type identityref
+--rw to-device-policy
+--rw access-lists
+--rw access-list* [acl-name acl-type]
+--rw acl-name -> /acl:access-lists/acl/acl-name
+--rw acl-type identityref
augment /acl:access-lists/acl:acl/acl:access-list-entries \
/acl:ace/acl:matches:
+--rw mud-acl {mud-acl}?
+--rw manufacturer? inet:host
+--rw same-manufacturer? empty
+--rw model? string
+--rw local-networks? empty
+--rw controller? inet:uri
+--rw my-controller? empty
augment /acl:access-lists/acl:acl/acl:access-list-entries \
/acl:ace/acl:matches/acl:tcp-acl:
+--rw direction-initiated? direction
3. Element Definitions
The following elements are defined.
3.1. last-update
This is a date-and-time value of when the MUD file was generated.
This is akin to a version number. Its form is taken from [RFC6991]
which, for those keeping score, turn was taken from Section 5.6 of
[RFC3339], which was taken from [ISO.8601.1988].
3.2. cache-validity
This uint8 is the period of time in hours that a network management
station MUST wait since its last retrieval before checking for an
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update. It is RECOMMENDED that this value be no less than 24 and
MUST NOT be more than 168 for any device that is supported.
3.3. masa-server
This optional element refers to the URL that should be used to
resolve the location any MASA service, as specified in
[I-D.ietf-anima-bootstrapping-keyinfra].
3.4. is-supported
This boolean is an indication from the manufacturer to the network
administrator as to whether or not the device is supported. In this
context a device is said to be supported if the manufacturer might
issue an update to the device or if the manufacturer might update the
MUD file.
3.5. systeminfo
This is a URL that points to a description of the device to be
connected. The intent is for administrators to be able to read about
what the device is the first time the MUD-URL is used.
3.6. extensions
This optional leaf-list names MUD extensions that are used in the MUD
file. Note that NO MUD extensions may be used in a MUD file prior to
the extensions being declared. Implementations MUST ignore any
elements in this file that they do not understand.
3.7. packet-direction
[I-D.ietf-netmod-acl-model] describes access-lists but does not
attempt to indicate where they are applied as that is handled
elsewhere in a configuration. However, in this case, a MUD file must
be explicit in describing the communication pattern of a device, and
that includes indicating what is to be permitted or denied in either
direction of communication. This element takes a single value of
either "to-device" or "from-device", based on a typedef "direction".
This is applied specifically for TCP, and may be implemented either
via stateful or stateless approaches (e.g,. TCP flags)
3.8. manufacturer
This element consists of a hostname that would be matched against the
authority component of another device's MUD URL.
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3.9. same-manufacturer
This is an equivalent for when the manufacturer element is used to
indicate the authority that is found in another device's MUD URL
matches that of the authority found in this device's MUD URL.
3.10. model
This string matches the one and only segment following the authority
component of the MUD URL. It refers to a model that is unique within
the context of the authority. It may also include product version
information. Thus how this field is constructed is entirely a local
matter for the manufacturer.
3.11. local-networks
This null-valued element expands to include local networks. Its
default expansion is that packets must not traverse toward a default
route that is received from the router. However, administrators may
expand the expression as is appropriate in their deployments.
3.12. controller
This URI specifies a value that a controller will register with the
mud controller. The element then is expanded to the set of hosts
that are so registered. This element may also be a URN. In this
case, the URN describes a well known service, such as DNS or NTP.
Great care should be used when invoking the controller class. For
one thing, it requires some understanding by the administrator as to
when it is appropriate. Classes that are standardized may make it
possible to code in certain intelligence. Nonstandard classes may
require substantially more care. Pre-registration in such classes by
controllers with the MUD server is encouraged. The mechanism to do
that is beyond the scope of this work.
3.13. my-controller
This null-valued element establishes a class of controllers that are
intended to control the device associated with a given MUD-URL.
3.14. direction-initiated
When applied this matches packets when the flow was initiated in the
corresponding direction. [RFC6092] specifies IPv6 guidance best
practices. While that document is scoped specifically to IPv6, its
contents are applicable for IPv4 as well. When this flag is set, and
the system has no reason to believe a flow has been initiated it MUST
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drop the packet. This match SHOULD be applied with specific
transport parameters, such as protocol.
4. Processing of the MUD file
To keep things relatively simple in addition to whatever definitions
exist, we also apply two additional default behaviors:
o Anything not explicitly permitted is denied.
o Local DNS and NTP are, by default, permitted to and from the
device.
An explicit description of the defaults can be found in Appendix B.
5. What does a MUD URL look like?
To begin with, MUD takes full advantage of both the https: scheme and
the use of .well-known. HTTPS is important in this case because a
man in the middle attack could otherwise harm the operation of a
class of devices. .well-known is used because we wish to add
additional structure to the URL. And so the URL appears as follows:
mud-url = "https://" authority "/.well-known/mud/" mud-rev
"/" model ( "?" extras )
; authority is from RFC3986
mud-rev = "v1"
model = segment ; from RFC3986
extras = query ; from RFC3986
mud-rev signifies the version of the manufacturer usage description
file. This memo specifies "v1" of that file. Later versions may
permit additional schemas or modify the format. In order to provide
for the broadest compatibility for the various transmission
mechanisms, the length of the URL for v1 MUST NOT exceed 255 octets.
"model" represents a device model as the manufacturer wishes to
represent it. It could be a brand name or something more specific.
It also may provide a means to indicate what version the product is.
Specifically if it has been updated in the field, this is the place
where evidence of that update would appear. The field should be
changed when the intended communication patterns of a device change.
While from a controller standpoint, only comparison and matching
operations are safe, it is envisioned that updates will require some
administrative review. Processing of this URL occurs as specified in
[RFC2818] and [RFC3986].
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6. The MUD YANG Model
<CODE BEGINS>file "ietf-mud@2017-07-03.yang"
module ietf-mud {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-mud";
prefix "ietf-mud";
import ietf-access-control-list {
prefix "acl";
}
import ietf-yang-types {
prefix "yang";
}
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@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. This specific module
focuses on additional filters that include local, model,
and same-manufacturer.
Copyright (c) 2016,2017 IETF Trust and the persons
identified as the document authors. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD
License set forth in Section 4.c of the IETF Trust's Legal
Provisions Relating to IETF Documents
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(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
revision "2017-07-03" {
description
"More work on ACL usage.";
reference "RFC XXXX: Manufacturer Usage Description
Specification";
}
revision "2017-06-29" {
description
"Take packet directionality out of ACL. " +
"Introduce device container.";
reference "RFC XXXX: Manufacturer Usage Description
Specification";
}
revision "2017-04-18" {
description "Base version of MUD extensions to ACL model";
reference "RFC XXXX: Manufacturer Usage Description
Specification";
}
typedef direction {
type enumeration {
enum to-device {
description "packets or flows destined to the target
device";
}
enum from-device {
description "packets or flows destined from
the target device";
}
}
description "Which way are we talking about?";
}
identity mud-acl {
base "acl:acl-base";
description
"ACL that contains MUD-specific access control list entries.";
}
feature mud-acl {
description
"MUD ACL augmentations supported.";
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}
container metainfo {
description "Information about when support end(ed), and
when to refresh";
leaf last-update {
type yang:date-and-time;
description "This is intended to be when
the MUD file was generated.";
}
leaf cache-validity {
type uint8 {
range "1..168";
}
description "The information retrieved from the MUD server is
valid for these many hours, after which it should
be refreshed.";
}
leaf masa-server {
type inet:uri;
description "The URI of the MASA server that network
elements should forward requests to for this device.";
}
leaf is-supported {
type boolean;
description "The element is currently supported
by the manufacturer.";
}
leaf systeminfo {
type inet:uri;
description "A reference to a description of this device";
}
leaf-list extensions {
type string;
description "A list of extension names that are used in this MUD
file. Each name is registered with the IANA and
described in an RFC.";
}
}
grouping ACCESS_LISTS {
description "A grouping for access lists in the context of device
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policy.";
container access-lists {
description "The access lists that should be applied to traffic
to or from the device.";
list access-list {
key "acl-name acl-type";
description "Each entry on this list refers to an ACL that
should be present in the overall access list
data model. Each ACL is identified by name and
type.";
leaf acl-name {
type leafref {
path "/acl:access-lists/acl:acl/acl:acl-name";
}
description "The name of the ACL for this entry.";
}
leaf acl-type {
type identityref {
base acl:acl-base;
}
description "The type of the ACL for this entry.";
}
}
}
}
container device {
description "A container allowing us to associate data with the
device type being described in the instance document";
container from-device-policy {
description "The policies that should be enforced on traffic
coming from the device. These policies are not
necessarily intended to be enforced at a single
point, but may be rendered by the controller to any
relevant enorcement points in the network or
elsewhere.";
uses ACCESS_LISTS;
}
container to-device-policy {
description "The policies that should be enforced on traffic
going to the device. These policies are not
necessarily intended to be enforced at a single
point, but may be rendered by the controller to any
relevant enorcement points in the network or
elsewhere.";
uses ACCESS_LISTS;
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}
}
augment "/acl:access-lists/acl:acl/" +
"acl:access-list-entries/acl:ace/" +
"acl:matches" {
description "adding abstractions to avoid need of IP addresses";
container mud-acl {
if-feature mud-acl;
must "../../../../acl-type = 'ietf-mud:mud-acl'";
description
"TODO; improve. MUD-specific matches.";
leaf manufacturer {
type inet:host;
description "authority component of the manufacturer URI";
}
leaf same-manufacturer {
type empty;
description "expand to ACEs for each device
with the same origin";
}
leaf model {
type string;
description "specific model (including version) for a
given manufacturer";
}
leaf local-networks {
type empty;
description "this string is used to indicate networks
considered local in a given environment.";
}
leaf controller {
type inet:uri;
description "expands to one or more controllers for a
given service that is codified by inet:uri.";
}
leaf my-controller {
type empty;
description "This element indicates that the network should manage
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a class of devices related to this MUD-URL that are
intended to control this device.";
}
}
}
augment "/acl:access-lists/acl:acl/" +
"acl:access-list-entries/acl:ace/" +
"acl:matches/acl:tcp-acl" {
description "Adding domain names to matching";
leaf direction-initiated {
type direction;
description "which direction a flow was initiated";
}
}
}
<CODE ENDS>
7. 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" element.
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:access-lists/acl:acl/acl:access-list-entries \
/acl:ace/acl:matches/acl:ipv4-acl:
+--rw src-dnsname? inet:host
+--rw dst-dnsname? inet:host
augment /acl:access-lists/acl:acl/acl:access-list-entries \
/acl:ace/acl:matches/acl:ipv6-acl:
+--rw src-dnsname? inet:host
+--rw dst-dnsname? inet:host
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 autjors the ability
to control the IP version that the device may utilize.
The following elements are defined.
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7.1. source-dnsname
The argument corresponds to a domain name of a source as specified by
inet:host. Depending on how the model is used, it may or may not be
resolved, as required by the implementation and circumstances.
7.2. destination-dnsname
The argument corresponds to a domain name of a destination as
specified by inet:host. Depending on how the model is used, it may
or may not be resolved, as required by the implementation and
circumstances.
7.3. The ietf-acldns Model
<CODE BEGINS>file "ietf-acldns@2016-07-20.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@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.";
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revision "2017-07-03" {
description "Clone across IP ACL types.";
reference "RFC XXXX: Manufacturer Usage Description
Specification";
}
revision "2016-07-20" {
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:access-lists/acl:acl/" +
"acl:access-list-entries/acl:ace/" +
"acl:matches/acl:ipv4-acl" {
description "Adding domain names to matching";
uses DNS_MATCHES;
}
augment "/acl:access-lists/acl:acl/" +
"acl:access-list-entries/acl:ace/" +
"acl:matches/acl:ipv6-acl" {
description "Adding domain names to matching";
uses DNS_MATCHES;
}
}
<CODE ENDS>
8. MUD File Example
This example contains two access lists that are intended to provide
outbound access to a cloud service on TCP port 443.
TODO: this needs to be revised.
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{
"ietf-mud:metainfo": {
"last-update": "2016-05-18T20:00:50Z",
"cache-validity": 168
},
"ietf-access-control-list:access-lists": {
"acl": [ {
"acl-name": "inbound-stuff",
"acl-type" : "ipv4-acl",
"ietf-mud:packet-direction" : "to-device",
"access-list-entries": {
"ace": [
{
"rule-name": "access-cloud",
"matches": {
"ietf-acldns:src-dnsname":
"lighting-system.example.com",
"protocol" : 6,
"source-port-range" : {
"lower-port" : 443,
"upper-port" : 443
}
},
"actions" : {
"permit" : [null]
}
}
]
}
},
{
"acl-name": "outbound-stuff",
"acl-type" : "ipv4-acl",
"ietf-mud:packet-direction" : "from-device",
"access-list-entries": {
"ace": [
{
"rule-name": "access-cloud",
"matches": {
"ietf-acldns:dst-dnsname":
"lighting-system.example.com",
"protocol" : 6,
"destination-port-range" : {
"lower-port" : 443,
"upper-port" : 443
}
},
"actions" : {
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"permit" : [null]
}
}
]
}
}
]
}
}
9. The MUD URL DHCP Option
The IPv4 MUD URL client option has the following format:
+------+-----+------------------------------
| code | len | MUD URL
+------+-----+------------------------------
Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single
octet that indicates the length of the URL in octets. MUD URL is a
URL. MUD URLs MUST NOT exceed 255 octets.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUD URL |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OPTION_MUD_URL_V6 (112; assigned by IANA).
option-length contains the length of the URL in octets.
The intent of this option is to provide both a new device 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
option is simply to identify the type of device to the network in a
structured way such that the policy can be easily found with existing
toolsets.
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9.1. 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.
Clients SHOULD log or otherwise report improper acknowledgments from
servers, but they MUST NOT modify their MUD URL configuration based
on a server's response. The server's response is only an
acknowledgment that the server has processed the option, and promises
no specific network behavior to the client. In particular, it may
not be possible for the server to retrieve the file associated with
the MUD URL, or the local network administration may not wish to use
the usage description. Neither of these situations should be
considered in any way exceptional.
9.2. Server Behavior
A DHCP server may ignore these options or take action based on
receipt of these options. If a server successfully parses the option
and the URL, it MUST return the option with length field set to zero
and a corresponding null URL field as an acknowledgment. Even in
this circumstance, no specific network behavior is guaranteed. When
a server consumes this option, it will either forward the URL and
relevant client information to a network management system (such as
the giaddr), or it will retrieve the usage description 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 controller. 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 controller MUST notify the MUD controller of any
corresponding change to the DHCP state of the client (such as
expiration or explicit release of a network address lease).
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9.3. Relay Requirements
There are no additional requirements for relays.
10. 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 Identifier (URI) 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 URI are defined Section 5 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.
The new extension is identified as follows:
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<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
-- EXPORTS ALL --
IMPORTS
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) }
id-pe
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) } ;
MUDCertExtensions EXTENSION ::= { ext-MUDURL, ... }
ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax
IDENTIFIED BY id-pe-mud-url }
id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 }
MUDURLSyntax ::= IA5String
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 controller implementations maintain a
table that maps a device to its MUD-URL.
11. The Manufacturer Usage Description LLDP extension
The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop
vendor-neutral link layer protocols used by end hosts network devices
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
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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 | MUD URL
| =127 | |= 00 00 5E| = 1 |
|(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets)
+--------+--------+----------+---------+--------------
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 device
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 device to the network in
a structured way such that the policy can be easily found with
existing toolsets.
Hosts, routers, or other network devices 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 devices 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 device and response sent by another
device. The other devices do not acknowledge LLDP information
received from a device. No specific network behavior is guaranteed.
When a device consumes this extension, it may either forward the URL
and relevant remote device information to a MUD controller, or it
will retrieve the usage description by resolving the URL.
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12. 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 insure 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.
12.1. 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 same
location as the MUD URL but with the suffix of ".p7s". Signatures
are transferred using content-type "Application/pkcs7-signature".
For example:
% openssl cms -sign -signer mancertfile -inkey mankey \
-in mudfile -binary -outform DER - \
-certfile intermediatecert -out mudfile.p7s
Note: A MUD file may need to be re-signed if the signature expires.
12.2. Verifying a MUD file signature
Prior to retrieving a MUD file the MUD controller SHOULD retrieve the
MUD signature file using the MUD URL with a suffix of ".p7s". For
example, if the MUD URL is "https://example.com/.well-known/v1/
modela", the MUD signature URL will be "https://example.com/.well-
known/v1/modela.p7s".
Upon retrieving a MUD file, a MUD controller MUST validate the
signature of the file before continuing with further processing. A
MUD controller SHOULD produce an error and it MUST cease all
processing of that file if the signature cannot be validated. It is
important that MUD controllers have some reason to trust the
certificates they are seeing. Therefore, it is RECOMMENDED that new
signers be validated either directly by an administrator or by a
service that has some reason to believe that the signer is a good
actor.
For Example:
% openssl cms -verify -in mudfile.p7s -inform DER -content mudfile
Note the additional step of verifying the common trust root.
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13. 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 device are permitted. Specifically, augmenting of
the metainfo container is permitted with the understanding that
such additions may be ignored. In addition, augmentation of the
ACL model is permitted so long as it remains safe for a given ACE
to be ignored by the MUD Controller or the network elements it
configures. Most specifically, is is not permitted to include as
an augmentation that modifies "deny" behavior without bumping the
version. Furthermore, implementations that are not able to parse
a component of the ACE array MUST ignore the entire array entry
(e.g., not the entire array) and MAY ignore the entire MUD file.
14. 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
device from other devices 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 so-called east-west infection is
increased to the number of devices that are able to communicate
without protection.
A caution about some of the classes: admission of a device into the
"manufacturer" and "same-manufacturer" class may have impact on
access of other devices. Put another way, the admission may grow the
access-list on switches connected to other devices, depending on how
access is managed. Therefore, care should be given on managing that
access-list growth. Alternative methods such as additional
segmentation can be used to keep that growth within reason.
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15. Security Considerations
Based on how a MUD-URL is emitted, a device may be able to lie about
what it is, thus gaining additional network access. There are
several means to limit risk in this case. The most obvious is to
only believe devices that make use of certificate-based
authentication such as IEEE 802.1AR certificates. When those
certificates are not present, devices claiming to be of a certain
manufacturer SHOULD NOT be included in that manufacturer grouping
without additional validation of some form. This will occur when it
makes use of primitives such as "manufacturer" for the purpose of
accessing devices of a particular type. Similarly, network
management systems may be able to fingerprint the device. 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 artificats to the MUD-
URL. The meaning of such artifacts is left as future work.
Network management systems SHOULD NOT accept a usage description for
a device with the same MAC address that has indicated a change of
authority without some additional validation (such as review of the
class). New devices that present some form of unauthenticated MUD
URL SHOULD be validated by some external means when they would be
otherwise 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 the signature of the MUD file. 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 device 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 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 controllers would consider valid. There
are a few approaches that can mitigate this attack. First, MUD
controllers SHOULD cache certificates used by the MUD file server.
When a new certificate is retrieved for whatever reason, the MUD
controller 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 controller MAY check the WHOIS database to see if
registration ownership of a domain has changed. If a change has
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occured, 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
device that was produced long ago and only recently fielded, or the
case where a new MUD controller has been installed.
The release of a MUD URL by a device reveals what the device 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
device, 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 device might otherwise be
identified, perhaps through how it behaves when it is connected to
the network, whether a device 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 devices may also assist in
limiting access to the MUD-URL through the use of mechanisms such as
DHCPv6-Shield [RFC7610].
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
device 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.
16. IANA Considerations
16.1. YANG Module Registrations
The following YANG modules are requested to be registred in the "IANA
Module Names" registry:
The ietf-mud module:
o Name: ietf-mud
o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-mud
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o Prefix: ief-mud
o Reference: This memo
The ietf-acldns module:
o Name: ietf-acldns
o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldns
o Prefix: ietf-acldns
o Reference: This memo
16.2. 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.
IANA is requested to allocated the DHCPv4 and v6 options as specified
in Section 9.
16.3. 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).
The use fo these values is specified in Section 10.
16.4. Well Known URI Suffix
The IANA has allocated the URL suffix of "mud" as follows:
o URI Suffix: "mud" o Specification documents: this document o
Related information: n/a
16.5. MIME Media-type Registration for MUD files
The following media-type is defined for transfer of MUD file:
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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 SHOULD be
employed.
o Security considerations: See {{secon}} of this document.
o Interoperability considerations: n/a
o Published specification: this document
o Applications that use this media type: MUD controllers as
specified by this document.
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@cisco.com>
o Intended usage: COMMON
o Restrictions on usage: none
o Author:
Eliot Lear <lear@cisco.com>
Ralph Droms <rdroms@cisco.com>
o Change controller: IESG
o Provisional registration? (standards tree only): No.
16.6. 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:
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 >
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16.7. 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. 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, and Dan Wing for their
valuable advice and reviews. Russ Housley entirely rewrote
Section 10 to be a complete module. Adrian Farrel provided the basis
for privacy considerations text. Kent Watson provided a thorough
review of the archictecture and the YANG model. The remaining errors
in this work are entirely the responsibility of the author.
18. References
18.1. Normative References
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
S., and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-06 (work in progress), May 2017.
[I-D.ietf-netmod-acl-model]
Bogdanovic, D., Jethanandani, M., Huang, L., Agarwal, S.,
and D. Blair, "Network Access Control List (ACL) YANG Data
Model", draft-ietf-netmod-acl-model-11 (work in progress),
June 2017.
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[I-D.ietf-netmod-rfc6087bis]
Bierman, A., "Guidelines for Authors and Reviewers of YANG
Data Model Documents", draft-ietf-netmod-rfc6087bis-13
(work in progress), June 2017.
[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,
<http://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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<http://www.rfc-editor.org/info/rfc2131>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<http://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, <http://www.rfc-editor.org/info/rfc3315>.
[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,
<http://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,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
January 2005, <http://www.rfc-editor.org/info/rfc3987>.
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[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,
<http://www.rfc-editor.org/info/rfc5280>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<http://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,
<http://www.rfc-editor.org/info/rfc5905>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<http://www.rfc-editor.org/info/rfc6020>.
[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,
<http://www.rfc-editor.org/info/rfc6092>.
[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,
<http://www.rfc-editor.org/info/rfc6335>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<http://www.rfc-editor.org/info/rfc6991>.
[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,
<http://www.rfc-editor.org/info/rfc7227>.
[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,
<http://www.rfc-editor.org/info/rfc7610>.
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18.2. Informative References
[FW95] Chapman, D. and E. Zwicky, "Building Internet Firewalls",
January 1995.
[IEEE8021AR]
Institute for Electrical and Electronics Engineers,
"Secure Device Identity", 1998.
[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,
<http://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,
<http://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, <http://www.rfc-editor.org/info/rfc3553>.
[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, <http://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, <http://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,
<http://www.rfc-editor.org/info/rfc7170>.
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[RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
"Architectural Considerations in Smart Object Networking",
RFC 7452, DOI 10.17487/RFC7452, March 2015,
<http://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,
<http://www.rfc-editor.org/info/rfc7488>.
Appendix A. Changes from Earlier Versions
RFC Editor to remove this section prior to publication.
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)
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)
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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 informaitonal element in. * add urn registry
and create first entry * add default elements
Appendix B. Default MUD elements
What follows is 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 ACEs. To block DNS or NTP one repeats the
matching statement but replace "permit" with deny. Because ACEs are
processed in the order they are received, the defaults would not be
reached. A MUD controller might further decide to optimize to simply
not include the defaults when they are overriden.
A complete MUD entry is included below.
{
"ietf-mud:metainfo": {
"last-update": "2016-09-27T15:10:24+02:00",
"cache-validity": 168
},
"acl:access-lists": {
"access-list": [
{
"acl-name": "mud-53134-v4in",
"acl-type": "ipv4-acl",
"ietf-mud:packet-direction": "to-device",
"access-list-entries": {
"ace": [
{
"rule-name": "entout0-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:dns",
"protocol": 17,
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"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout1-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:dns",
"protocol": 6,
"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout2-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:ntp",
"protocol": 17,
"source-port-range": {
"lower-port": 123,
"upper-port": 123
}
},
"actions": {
"permit": [
null
]
}
}
]
}
},
{
"acl-name": "mud-53134-v4out",
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"acl-type": "ipv4-acl",
"ietf-mud:packet-direction": "from-device",
"access-list-entries": {
"ace": [
{
"rule-name": "entout0-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:dns",
"protocol": 17,
"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout1-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:dns",
"protocol": 6,
"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout2-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:ntp",
"protocol": 17,
"source-port-range": {
"lower-port": 123,
"upper-port": 123
}
},
"actions": {
"permit": [
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null
]
}
}
]
}
},
{
"acl-name": "mud-53134-v6in",
"acl-type": "ipv6-acl",
"ietf-mud:packet-direction": "to-device",
"access-list-entries": {
"ace": [
{
"rule-name": "entout0-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:dns",
"protocol": 17,
"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout1-in",
"matches": {
"ietf-mud:controller": "urn:params:mud:dns",
"protocol": 6,
"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout2-in",
"matches": {
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"ietf-mud:controller": "urn:ietf:params:mud:ntp",
"protocol": 17,
"source-port-range": {
"lower-port": 123,
"upper-port": 123
}
},
"actions": {
"permit": [
null
]
}
}
]
}
},
{
"acl-name": "mud-53134-v6out",
"acl-type": "ipv6-acl",
"ietf-mud:packet-direction": "from-device",
"access-list-entries": {
"ace": [
{
"rule-name": "entout0-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:dns",
"protocol": 17,
"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout1-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:dns",
"protocol": 6,
"source-port-range": {
"lower-port": 53,
"upper-port": 53
}
},
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"actions": {
"permit": [
null
]
}
},
{
"rule-name": "entout2-in",
"matches": {
"ietf-mud:controller": "urn:ietf:params:mud:ntp",
"protocol": 17,
"source-port-range": {
"lower-port": 123,
"upper-port": 123
}
},
"actions": {
"permit": [
null
]
}
}
]
}
}
]
}
}
Authors' Addresses
Eliot Lear
Cisco Systems
Richtistrasse 7
Wallisellen CH-8304
Switzerland
Phone: +41 44 878 9200
Email: lear@cisco.com
Ralph Droms
Phone: +1 978 376 3731
Email: rdroms@gmail.com
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Dan Romascanu
Phone: +972 54 5555347
Email: dromasca@gmail.com
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