Manufacturer Usage Description SpecificationCisco SystemsRichtistrasse 7WallisellenCH-8304Switzerland+41 44 878 9200lear@cisco.com+1 978 376 3731rdroms@gmail.com+972 54 5555347dromasca@gmail.comInternet-DraftThis 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.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. 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. 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.The intent of MUD is to therefore solve for the following problems:Substantially reduce the threat surface on a device entering a
network to those communications intended by the manufacturer.Provide for a means to scale network policies to the ever-increasing
number types of devices in the network.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.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.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.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 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.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 . 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 . 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.Our work begins, therefore, with the device emitting a Universal
Resource Locator (URL) . 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, 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 that provides a
certificate-based approach to communicate device characteristics,
which itself relies on . 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) . Finally, a
Link Layer Discovery Protocol (LLDP) frame is defined .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
is, and what its MUD file server is. Such mechanisms are not
described in this memo, but are possible.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: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: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 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.The YANG modules specified here are extensions of
. 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 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:
A device made by a particular manufacturer, as identified by the authority
component of its MUD-URL
Devices that have the same authority component of their MUD-URL.
A device that the local network administrator admits to the particular class.
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.
manufacturer usage description.
a file containing YANG-based JSON that describes a recommended behavior.
a web server that hosts a MUD file.
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.
a URL that can be used by the MUD controller to receive the MUD file.
the end device that emits a MUD URL.
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
.With these components laid out we now have the basis for an
archicture. This leads us to ASCII art.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, which would then process it. One method to do
this is TEAP, described in . The certificate extension is
described below.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.As mentioned above, MUD contains architectural building blocks, and so
order of operation may vary. However, here is one clear intended
example:Device emits URL.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).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.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.The MUD controller instantiates local configuration based on
the abstractions defined in this document.The MUD controller configures the switch nearest the device.
Other systems may be configured as well.When the device disconnects, policy is removed.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
small number of YANG schema, including the models specified in the
following documents:Publishers of MUD files MUST NOT include other elements except as
described in , 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 three parts. The first container holds
information that is relevant to retrieval and validity of the MUD file
itself. The second container augments the access list to indicate
direction the ACL is to be applied. The final 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.Simplified graphical representation of the data models are used in
this document. The meaning of the symbols in these diagrams is
defined in .The following elements are defined.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
which, for those keeping score, turn was taken from
Section 5.6 of , which was taken from .This uint8 is the period of time in hours that a network management
station MUST wait since its last retrieval before checking for an
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.This optional element refers to the URL that should be used to
resolve the location any MASA service, as specified in
.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.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.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. 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 element consists of a hostname that would be matched against the
authority component of another device’s MUD URL.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.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.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.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.This null-valued element establishes a class of controllers that are
intended to control the device associated with the MUD file being
referenced.When applied this matches packets when the flow was initiated in the
corresponding direction. 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 drop the packet. This match SHOULD be applied with specific
transport parameters, such as protocol.To keep things relatively simple in addition to whatever definitions
exist, we also apply two additional default behaviors:Anything not explicitly permitted is denied.Local DNS and NTP are, by default, permitted to and from the
device.An explicit description of the defaults can be found in .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-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
and .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:The choice of this particular point 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 .The following elements are defined.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.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.This example contains two access lists that are intended to provide
outbound access to a cloud service on TCP port 443.The IPv4 MUD URL client option has the following format: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: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.A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit
DHCPv6 option. These options are singletons, as specified in
. 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.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 and 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).There are no additional requirements for relays.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 .Any Internationalized Resource Identifiers (IRIs) MUST be mapped to
URIs as specified in Section 3.1 of before they are placed
in the certificate extension.The semantics of the URI are defined of this document.The choice of id-pe is based on guidance found in Section 4.2.2 of
:The MUD URL is precisely that: online information about the particular subject.The new extension is identified as follows: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.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
as documented in . 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:where:TLV Type = 127 indicates a vendor-specific TLVlen – indicates the TLV string lengthOUI = 00 00 5E is the organizationally unique identifier of IANAsubtype = 1 (to be assigned by IANA for the MUD URL)MUD URL – the length MUST NOT exceed 255 octetsThe 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.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) for
this purpose.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:Note: A MUD file may need to be re-signed if the signature expires.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:Note the additional step of verifying the common trust root.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: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.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.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.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 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, 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
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 .Please note that the security considerations mentioned in Section 4.7
of 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 .
The basic purpose of MUD is to configure access, and so by its very
nature can be disruptive if used by unauthorized parties.The following YANG modules are requested to be registred in the “IANA
Module Names” registry:The ietf-mud module:Name: ietf-mudXML Namespace: urn:ietf:params:xml:ns:yang:ietf-mudPrefix: ief-mudReference: This memoThe ietf-acldns module:Name: ietf-acldnsXML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldnsPrefix: ietf-acldnsReference: This memoThe 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 .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 .The IANA has allocated the URL suffix of “mud” as follows:o URI Suffix: “mud”
o Specification documents: this document
o Related information: n/aThe following media-type is defined for transfer of MUD file: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 >The following parameter registry is requested to be added in
accordance with 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 .
“urn:ietf:params:mud:ntp” refers to the service specified by .The authors would like to thank Einar Nilsen-Nygaard, 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 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.Requirements for Internet Hosts - Application and SupportThis RFC is an official specification for the Internet community. It incorporates by reference, amends, corrects, and supplements the primary protocol standards documents relating to hosts. [STANDARDS-TRACK]Key words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Extensible Authentication Protocol (EAP)This document defines the Extensible Authentication Protocol (EAP), an authentication framework which supports multiple authentication methods. EAP typically runs directly over data link layers such as Point-to-Point Protocol (PPP) or IEEE 802, without requiring IP. EAP provides its own support for duplicate elimination and retransmission, but is reliant on lower layer ordering guarantees. Fragmentation is not supported within EAP itself; however, individual EAP methods may support this. This document obsoletes RFC 2284. A summary of the changes between this document and RFC 2284 is available in Appendix A. [STANDARDS-TRACK]Uniform Resource Identifier (URI): Generic SyntaxA Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK]Internationalized Resource Identifiers (IRIs)This document defines a new protocol element, the Internationalized Resource Identifier (IRI), as a complement of the Uniform Resource Identifier (URI). An IRI is a sequence of characters from the Universal Character Set (Unicode/ISO 10646). A mapping from IRIs to URIs is defined, which means that IRIs can be used instead of URIs, where appropriate, to identify resources. The approach of defining a new protocol element was chosen instead of extending or changing the definition of URIs. This was done in order to allow a clear distinction and to avoid incompatibilities with existing software. Guidelines are provided for the use and deployment of IRIs in various protocols, formats, and software components that currently deal with URIs.YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]Network Access Control List (ACL) YANG Data ModelThis document describes a data model of Access Control List (ACL) basic building blocks. Editorial Note (To be removed by RFC Editor) This draft contains many placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. Please note that no other RFC Editor instructions are specified anywhere else in this document. Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements o "XXXX" --> the assigned RFC value for this draft. o Revision date in model (Oct 12, 2016) needs to get updated with the date the draft gets approved. The date also needs to get reflected on the line with <CODE BEGINS>.Bootstrapping Remote Secure Key Infrastructures (BRSKI)This document specifies automated bootstrapping of a remote secure key infrastructure (BRSKI) using vendor installed X.509 certificate, in combination with a vendor's authorizing service, both online the Internet, and offline. Bootstrapping a new device can occur using a routable address and a cloud service, or using only link-local connectivity, or on limited/disconnected networks. Support for lower security models, including devices with minimal identity, is described for legacy reasons but not encouraged. Bootstrapping is complete when the cryptographic identity of the new key infrastructure is successfully deployed to the device but the established secure connection can be used to deploy a locally issued certificate to the device as well.Guidelines for Authors and Reviewers of YANG Data Model DocumentsThis memo provides guidelines for authors and reviewers of Standards Track specifications containing YANG data model modules. Applicable portions may be used as a basis for reviews of other YANG data model documents. Recommendations and procedures are defined, which are intended to increase interoperability and usability of Network Configuration Protocol (NETCONF) and RESTCONF protocol implementations that utilize YANG data model modules.HTTP Over TLSThis memo describes how to use Transport Layer Security (TLS) to secure Hypertext Transfer Protocol (HTTP) connections over the Internet. This memo provides information for the Internet community.Network Time Protocol Version 4: Protocol and Algorithms SpecificationThe Network Time Protocol (NTP) is widely used to synchronize computer clocks in the Internet. This document describes NTP version 4 (NTPv4), which is backwards compatible with NTP version 3 (NTPv3), described in RFC 1305, as well as previous versions of the protocol. NTPv4 includes a modified protocol header to accommodate the Internet Protocol version 6 address family. NTPv4 includes fundamental improvements in the mitigation and discipline algorithms that extend the potential accuracy to the tens of microseconds with modern workstations and fast LANs. It includes a dynamic server discovery scheme, so that in many cases, specific server configuration is not required. It corrects certain errors in the NTPv3 design and implementation and includes an optional extension mechanism. [STANDARDS-TRACK]Common YANG Data TypesThis document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021.Dynamic Host Configuration ProtocolThe Dynamic Host Configuration Protocol (DHCP) provides a framework for passing configuration information to hosts on a TCPIP network. DHCP is based on the Bootstrap Protocol (BOOTP), adding the capability of automatic allocation of reusable network addresses and additional configuration options. [STANDARDS-TRACK]Dynamic Host Configuration Protocol for IPv6 (DHCPv6)Guidelines for Creating New DHCPv6 OptionsThis document provides guidance to prospective DHCPv6 option developers to help them create option formats that are easily adoptable by existing DHCPv6 software. It also provides guidelines for expert reviewers to evaluate new registrations. This document updates RFC 3315.DHCPv6-Shield: Protecting against Rogue DHCPv6 ServersThis document specifies a mechanism for protecting hosts connected to a switched network against rogue DHCPv6 servers. It is based on DHCPv6 packet filtering at the layer 2 device at which the packets are received. A similar mechanism has been widely deployed in IPv4 networks ('DHCP snooping'); hence, it is desirable that similar functionality be provided for IPv6 networks. This document specifies a Best Current Practice for the implementation of DHCPv6-Shield.Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) ProfileThis memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK]Cryptographic Message Syntax (CMS)This document describes the Cryptographic Message Syntax (CMS). This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content. [STANDARDS-TRACK]Recommended Simple Security Capabilities in Customer Premises Equipment (CPE) for Providing Residential IPv6 Internet ServiceThis document identifies a set of recommendations for the makers of devices and describes how to provide for "simple security" capabilities at the perimeter of local-area IPv6 networks in Internet-enabled homes and small offices. This document is not an Internet Standards Track specification; it is published for informational purposes.Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number RegistryThis document defines the procedures that the Internet Assigned Numbers Authority (IANA) uses when handling assignment and other requests related to the Service Name and Transport Protocol Port Number registry. It also discusses the rationale and principles behind these procedures and how they facilitate the long-term sustainability of the registry.This document updates IANA's procedures by obsoleting the previous UDP and TCP port assignment procedures defined in Sections 8 and 9.1 of the IANA Allocation Guidelines, and it updates the IANA service name and port assignment procedures for UDP-Lite, the Datagram Congestion Control Protocol (DCCP), and the Stream Control Transmission Protocol (SCTP). It also updates the DNS SRV specification to clarify what a service name is and how it is registered. This memo documents an Internet Best Current Practice.IEEE Standard for Local and Metropolitan Area Networks-- Station and Media Access Control Connectivity DiscoveryInstitute for Electrical and Electronics EngineersIAB and IESG Statement on Cryptographic Technology and the InternetIABIESGThe Internet Architecture Board (IAB) and the Internet Engineering Steering Group (IESG), the bodies which oversee architecture and standards for the Internet, are concerned by the need for increased protection of international commercial transactions on the Internet, and by the need to offer all Internet users an adequate degree of privacy. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.Date and Time on the Internet: TimestampsAn IETF URN Sub-namespace for Registered Protocol ParametersThis document describes a new sub-delegation for the 'ietf' URN namespace for registered protocol items. The 'ietf' URN namespace is defined in RFC 2648 as a root for persistent URIs that refer to IETF- defined resources. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.The Common Log Format (CLF) for the Session Initiation Protocol (SIP): Framework and Information ModelWell-known web servers such as Apache and web proxies like Squid support event logging using a common log format. The logs produced using these de facto standard formats are invaluable to system administrators for troubleshooting a server and tool writers to craft tools that mine the log files and produce reports and trends. Furthermore, these log files can also be used to train anomaly detection systems and feed events into a security event management system. The Session Initiation Protocol (SIP) does not have a common log format, and, as a result, each server supports a distinct log format that makes it unnecessarily complex to produce tools to do trend analysis and security detection. This document describes a framework, including requirements and analysis of existing approaches, and specifies an information model for development of a SIP common log file format that can be used uniformly by user agents, proxies, registrars, and redirect servers as well as back-to-back user agents.IANA Considerations and IETF Protocol and Documentation Usage for IEEE 802 ParametersSome IETF protocols make use of Ethernet frame formats and IEEE 802 parameters. This document discusses several uses of such parameters in IETF protocols, specifies IANA considerations for assignment of points under the IANA OUI (Organizationally Unique Identifier), and provides some values for use in documentation. This document obsoletes RFC 5342.Tunnel Extensible Authentication Protocol (TEAP) Version 1This document defines the Tunnel Extensible Authentication Protocol (TEAP) version 1. TEAP is a tunnel-based EAP method that enables secure communication between a peer and a server by using the Transport Layer Security (TLS) protocol to establish a mutually authenticated tunnel. Within the tunnel, TLV objects are used to convey authentication-related data between the EAP peer and the EAP server.Architectural Considerations in Smart Object NetworkingThe term "Internet of Things" (IoT) denotes a trend where a large number of embedded devices employ communication services offered by Internet protocols. Many of these devices, often called "smart objects", are not directly operated by humans but exist as components in buildings or vehicles, or are spread out in the environment. Following the theme "Everything that can be connected will be connected", engineers and researchers designing smart object networks need to decide how to achieve this in practice.This document offers guidance to engineers designing Internet- connected smart objects.Port Control Protocol (PCP) Server SelectionThis document specifies the behavior to be followed by a Port Control Protocol (PCP) client to contact its PCP server(s) when one or several PCP server IP addresses are configured.This document updates RFC 6887.Data elements and interchange formats - Information interchange - Representation of dates and timesInternational Organization for StandardizationSecure Device IdentityInstitute for Electrical and Electronics EngineersBuilding Internet FirewallsRFC Editor to remove this section prior to publication.Draft -05 to -06:Make clear that this is a component architecture (Polk and Watson)Add order of operations (Watson)Add extensions leaf-list (Pritikin)Remove previous-mud-file (Watson)Modify text in last-update (Watson)Clarify local networks (Weis, Watson)Fix contact info (Watson)Terminology clarification (Weis)Advice on how to handle LDevIDs (Watson)Add deployment considerations (Watson)Add some additional text about fingerprinting (Watson)Appropriate references to 6087bis (Watson)Change systeminfo to a URL to be referenced (Lear)Draft -04 to -05:
* syntax error correctionDraft -03 to -04:
* Re-add my-controllerDraft -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:paramsDraft -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 elementsWhat 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.