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RFC 8240

Informational
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Report from the Internet of Things Software Update (IoTSU) Workshop 2016

 


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Internet Architecture Board (IAB)                          H. Tschofenig
Request for Comments: 8240                                    S. Farrell
Category: Informational                                   September 2017
ISSN: 2070-1721


Report from the Internet of Things Software Update (IoTSU) Workshop 2016

Abstract

   This document provides a summary of the Internet of Things Software
   Update (IoTSU) Workshop that took place at Trinity College Dublin,
   Ireland on the 13th and 14th of June, 2016.  The main goal of the
   workshop was to foster a discussion on requirements, challenges, and
   solutions for bringing software and firmware updates to IoT devices.
   This report summarizes the discussions and lists recommendations to
   the standards community.

   Note that this document is a report on the proceedings of the
   workshop.  The views and positions documented in this report are
   those of the workshop participants and do not necessarily reflect IAB
   views and positions.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Architecture Board (IAB)
   and represents information that the IAB has deemed valuable to
   provide for permanent record.  It represents the consensus of the
   Internet Architecture Board (IAB).  Documents approved for
   publication by the IAB are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8240.

[Page 2] 
Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Requirements and Questions Raised . . . . . . . . . . . . . .   6
   4.  Authorizing a Software/Firmware Update  . . . . . . . . . . .  12
   5.  End-of-Support  . . . . . . . . . . . . . . . . . . . . . . .  13
   6.  Incentives  . . . . . . . . . . . . . . . . . . . . . . . . .  15
   7.  Measurements and Analysis . . . . . . . . . . . . . . . . . .  15
   8.  Firmware Distribution in Mesh Networks  . . . . . . . . . . .  16
   9.  Compromised Devices . . . . . . . . . . . . . . . . . . . . .  17
   10. Miscellaneous Points  . . . . . . . . . . . . . . . . . . . .  17
   11. Tentative Conclusions and Next Steps  . . . . . . . . . . . .  19
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  20
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   14. Informative References  . . . . . . . . . . . . . . . . . . .  20
   Appendix A.  Program Committee  . . . . . . . . . . . . . . . . .  24
   Appendix B.  Accepted Position Papers . . . . . . . . . . . . . .  24
   Appendix C.  List of Participants . . . . . . . . . . . . . . . .  26
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

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1.  Introduction

   This document provides a summary of the Internet of Things Software
   Update (IoTSU) Workshop [IoTSU] that took place at Trinity College
   Dublin, Ireland on the 13th and 14th of June, 2016.  The main goal of
   the workshop was to foster a discussion on requirements, challenges,
   and solutions for bringing software and firmware updates to IoT
   devices.

   The views and positions in this report are those of the workshop
   participants and do not necessarily reflect those of their employers/
   sponsors, the authors of this memo, nor the Internet Architecture
   Board (IAB), under whose auspices the workshop was held.

   The IAB holds occasional workshops designed to consider long-term
   issues and strategies for the Internet, and to suggest future
   directions for the Internet architecture.  The topics investigated
   often require coordinated efforts of different organizations and
   industry bodies to improve an identified problem.  One of the goals
   of such workshops is to assist with communication between relevant
   organizations, companies, and universities, especially when the
   topics are partly out of the scope for the Internet Engineering Task
   Force (IETF).  This long-term planning function of the IAB is
   complementary to the ongoing engineering efforts performed by working
   groups of the IETF.

   In his essay "The Internet of Things Is Wildly Insecure -- And Often
   Unpatchable" [BS14], Bruce Schneier expressed concerns about the
   status of software/firmware updates for IoT devices.  IoT devices,
   which have a reputation for being insecure from the time they are
   manufactured, are often expected to stay active in the field for 10
   or more years and to operate unattended with Internet connectivity.

   Incorporating a software update mechanism to fix vulnerabilities, to
   update configuration settings and, to add new functionality as well,
   is recommended by security experts.  However, there are challenges
   when using software updates, as documented in the United States
   Federal Trade Commission (FTC) report titled "internet of things:
   Privacy & Security in a Connected World" [FTC] and in the Article 29
   Data Protection Working Party document "Opinion 8/2014 on the on
   [sic] Recent Developments on the Internet of Things"[WP29].

   Among the challenges in designing a basic software/firmware update
   function are:

   -  Implementations of software update mechanisms may incorporate
      vulnerabilities, becoming an attractive attack target.  See, for
      example, [OS14].

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   -  Operational challenges, such as the case of an expired certificate
      in a hub device [BB14].

   -  Privacy issues if devices "call home" often to check for updates.

   -  A lack of incentives to distribute software updates along the
      value chain.

   -  Questions such as the following.  Who should be able to update
      device software after normal support stops?  When should an
      alternate source of software updates take over?

   There are various (often proprietary) software update mechanisms in
   use today, and the functionality of those varies significantly with
   the envisioned use of the IoT devices.  More powerful IoT devices,
   such as those running general purpose operating systems (like Linux),
   can make use of sophisticated software update mechanisms known from
   the desktop and the mobile world.  This workshop focused on more
   constrained IoT devices that often run dedicated real-time operating
   systems or potentially no operating system at all.

   There is a real risk that many IoT devices will continue to be
   shipped without a solid software/firmware update mechanism in place.
   Ideally, IoT software developers and product designers should be able
   to integrate standardized mechanisms that have experienced
   substantial review and where the documentation is available to the
   public.

   Hence, the IAB decided to organize a workshop to reach out to
   relevant stakeholders to explore the state of the art and to identify
   requirements and gaps.  In particular, the call for position papers
   asked for:

   -  Protocol mechanisms for distributing software updates.

   -  Mechanisms for securing software updates.

   -  Metadata about software/firmware packages.

   -  Implications of operating system and hardware design on the
      software update mechanisms.

   -  Installation of software updates (in context of software and
      hardware security of IoT devices).

   -  Privacy implications of software update mechanisms.

   -  Implications of device ownership and control for software update.

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   The rest of the document is organized as follows: basic terminology
   is provided in Section 2, followed by a longer section discussing
   requirements.  Subsequent sections explore selected topics, such as
   incentives and measurements in more detail.  Most of the write-up
   does raise more questions than it answers.  Nevertheless, we tried to
   synthesize possible conclusions and offer a few next steps.

2.  Terminology

   As is typical with people from different backgrounds, workshop
   participants started the workshop with a discussions of terminology.
   This section is more intended to reflect those discussions than to
   present canonical definitions of terms.

   Device Classes:  IoT devices come in various "sizes" (such as size of
      RAM or size of flash memory).  With these configurations, devices
      are limited in what they can support in terms of operating-system
      features, cryptographic algorithms, and protocol stacks.  For this
      reason, the group differentiated two types of classes, namely ARM
      Cortex A-class/Intel Atom and Cortex M-class/Intel Quark types of
      devices.  A-class devices are equipped with powerful processors
      typically found in set-top boxes and home routers.  The Raspberry
      Pi is an example of an A-class device that is capable of running a
      regular desktop operating system, such as Linux.  There are
      differences between the Intel and the ARM-based CPUs in terms of
      architecture, microcode, and who is allowed to update a Basic
      Input/Output System (BIOS) (if available).  A detailed discussion
      of these hardware architectural differences were, however, outside
      the scope of the workshop.  The implication is that lower-end
      microcontrollers have constraints that put restrictions on the
      amount of software that can be put on them.  While it is easy to
      require support of a wide range of features, those may not
      necessarily fit on these devices.

   Software Update and Firmware Update:  Based on the device classes, it
      was observed that regular operating systems come with
      sophisticated software update mechanisms (such as Red Hat Package
      Manager (RPM) [RPM] or pacman [PACMAN]) that make use of the
      operating system to install and run each application in a
      compartmentalized fashion.  Firmware updates typically do not
      provide such a fine-grained granularity for software updates and
      instead distribute the entire binary image, which consists of the
      (often minimalistic) operating system and all applications.  While
      the distinction between the mechanisms that A-class and M-class
      devices will typically use may get more fuzzy over time, most
      M-class devices use firmware updates while A-class devices use a
      combination of firmware and software updates (with firmware
      updates being less frequent operations).

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   Hitless Update:  A hitless update implies that the user experience is
      not "hit", i.e., it is not impacted.  It is possible to impact the
      user experience when applying an update even when the device does
      not reboot (to obtain or apply said update).  If the update is
      applied when a user is not using a product and their service is
      not impacted, the update is "hitless".

3.  Requirements and Questions Raised

   Workshop participants discussed requirements and several of these
   raised further questions.  As with the previous section, we aim to
   present the discussion as it was.

   -  There may be a need to be support partial (differential) updates
      that do not require the entire firmware image to be sent.  This
      may mean that techniques like bsdiff [BSDIFF] and courgette
      [COURGETTE] are used but might also mean devices supporting the
      download of applications and libraries alone.  The latter feature
      may require dynamic linking and position independent code.  It was
      unclear whether position independent code should be recommended
      for low-end IoT devices.

   -  The relative importance of dynamic linkers for low-end IoT devices
      is unclear.  Some operating systems used with M-class devices,
      such as Contiki, provide support for a dynamic linker according to
      [OS-Support].  This could help to minimize the amount of data
      transmitted during updates since only the modified application or
      library needs to be transmitted.

   -  How should dependencies among various software updates be handled?
      These dependencies may include information about the hardware
      platform and configuration as well as other software components
      running on a system.  For firmware updates, the problem of
      dependencies are often solved by the manufacturer or Original
      Equipment Manufacturer (OEM) rather than on the device itself.

   -  Support for devices with multiple microcontrollers may require an
      architecture where one microcontroller is responsible for
      interacting with the update service and then dispatching software
      images to the attached microcontrollers within its local realm.
      The alternative of letting each microcontroller interact with an
      update service appeared less practical.

   -  Support may be required for devices with multiple owners/
      stakeholders where the question arises about who is authorized to
      push a firmware/software update.

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   -  Data origin authentication (DAO) was agreed to be required for
      software updates.  Without DAO, updates simply become a perfect
      vulnerability.  It is, however, nontrivial to ensure that the
      actual trust relationships that exist are modeled by the DAO
      mechanism.  For some devices and deployment scenarios, any DAO
      mechanism is onerous, possibly to the point where it may be hard
      to convince a device maker to include the functionality.

   -  Should digital signatures and encryption for software updates be
      recommended as a best current practice?  This question
      particularly raises the question about the use of symmetric key
      cryptography since not all low-end IoT devices are currently using
      asymmetric crypto.

   -  DAO is most commonly provided via digital signature mechanisms,
      but symmetric schemes could also be developed, though IETF
      discussion of such mechanisms (for purposes less sensitive than
      software update) has proved significantly controversial.  The main
      problem seems to be that simple symmetric schemes only ensure that
      the sender is a member of a group, and they do not fully
      authenticate a specific sender.  And with a software update, we do
      not want any (possibly compromised) device to be able to
      authenticate new software for all other similar devices.

   -  What are the firmware update signing key requirements?  Since
      devices have a rather long lifetime, there has to be a way to
      change the signing key during the lifetime of the device.

   -  Should a firmware update mechanism support multiple signatures of
      firmware images?  Multiple signatures can come in two different
      flavors, namely:

         A single firmware image may be signed by multiple different
         parties.  In this case, one could imagine an environment where
         an OEM signs the software it creates, but then the software is
         again signed by the enterprise that approves the distribution
         within the company.  Other examples include regulatory
         signatures where the software for a medical device may be
         signed as approved by a certification body.

         A software image may contain libraries that are each signed by
         their developers.

      Is a device expected to verify the different types of signatures
      or is this a service provided by some unconstrained device?  This
      raises questions about who the IoT device should trust for what
      and whether transitive trust is acceptable for some types of
      devices.

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   -  Are applications from a range of sources allowed to run on a
      device or only those from the OEM?  If the device is a "closed"
      device that only supports/runs software from the OEM, then a
      single signature may be sufficient.  In a system that is more
      "open", third-party applications may require support of multiple
      signatures.

   -  There is a need for some form of secure storage, at least for
      those IoT devices that are exposed to physical attacks.  This
      includes at least the need to protect the integrity of the public
      key of the update service on the device (if signature-based DAO is
      in use).  The use of symmetric key cryptography requires improved
      confidentiality protection (in addition to integrity protection).

   -  Is there a need to allow the update infrastructure side to
      authenticate the IoT device before distributing an update?
      Questions about the identifier used for such an authentication
      action were raised.  The idea of reusing Media Access Control
      (MAC) addresses lead to concerns about the significant privacy
      implications of such identifier reuse.

   -  It is important to minimize device/service downtime due to update
      processing and to minimize user interaction (e.g., car should not
      distract the driver) (see "Hitless Update" in Section 2).  While
      it may not be possible to avoid all downtime, there was agreement
      that one ought to strive for "no inappropriate" device downtime.
      This means minimal downtime impacting the user/operation of the
      device.  The definition of "downtime" also depends on the use
      case, with a smart light bulb, the device could be "up" if the
      light is still on, even if some advanced services are unavailable
      for a short time.  Whether an update can be done without rebooting
      the device depends on the software being installed, on the OS
      architecture, and potentially even on the hardware architecture.
      The cost/benefit ratio also plays a role.

   -  It is desirable to minimize the time taken from the start of the
      update to when it is finished.  In some systems with many devices
      (e.g., industrial lighting), this can be a challenge if updates
      need to be unicasted.

   -  In some systems with multiple devices, it can be a challenge to
      ensure that all devices are at the same release level, especially
      if some devices are sleepy.  There are some systems where ensuring
      all relevant devices are at the same release level is a hard
      requirement.  In other cases, it is acceptable if devices converge
      much more slowly to the current release level.

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   -  It ought not be possible for a factory worker to compromise the
      update process (e.g., copy signing keys and install unauthorized
      public keys/trust anchors) during the manufacturing process.
      There are typically two factories involved: the first factory
      produces microcontrollers and other components and the second
      factory produces the complete product, such as a fridge.  This
      fridge contains many of the components previously manufactured.
      Hence, the firmware of components produced in the first stage may
      be six months old when the fridge leaves the factory.  One does
      not want to install a firmware update when the fridge boots the
      first time.  For that time, the firmware update happens already at
      the end of the manufacturing process.

   -  Should devices have a recovery procedure when the device gets
      compromised?  How is the compromise detected?

   -  There was a bit of discussion about the importance for IoT devices
      to know the current time for the purpose of checking certificate
      validity.  For example, what does "real-time clock" (RTC) actually
      mean?  And what constitutes "good enough" time?  There are,
      however, cost, power, size, and environmental constraints that can
      make the addition of a real-time clock to an IoT device complex:

      o  Cost: Battery- or supercap-backed RTC modules might be several
         times the cost of the rest of the bill of materials.

      o  Size: The battery and other components are often several times
         larger than the rest of the material.

      o  Manufacturing: Some modules require an extra assembly step,
         because the battery could be damaged or explode at high
         temperatures during the reflow process.

      o  Supply chain: Devices containing fitted batteries need
         additional supply-chain management to account for storage
         temperature and to avoid shipping aged devices.

      o  Environmental: Real-time-clock modules are typically not rated
         at industrial temperature ranges.  Those that are have
         extremely reduced lifetime at high temperatures.

      o  Lifetime: Some of these modules last only a few years at the
         top of their environmental range.

      While a good solution is needed, it is not clear whether there is
      one true solution.  A recent proposal from Google called
      "Roughtime" [RT] may be worthwhile to explore.

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   -  How do devices learn about a firmware update?  Push or Pull?  What
      should be required functionality for a firmware update protocol?

   -  There is a need to find out whether a software update was
      successful.  In one discussed solution, the bootloader analyzes
      the performance of the running image to determine which image to
      run (rather than just verifying the integrity of the received
      image).  One of the key criteria is that the updated system is
      able to make a connection to the device management/software update
      infrastructure.  As long as it is able to talk to the update
      infrastructure, it can receive another update.  As an alternative
      perspective, the argument was made that one needs to have a way to
      update the system without having the full system running.

   -  Gateway requirements.  In some deployments, gateways terminate the
      IP-based protocol communication and use non-IP mechanisms to
      communicate with other microcontrollers, for example, within a
      car.  The gateway in such a system is the endpoint of the IP
      communication.  The group had mixed feelings about the use of
      gateways versus the use of IP communication to every
      microcontroller.  Participants argued that there is a lack of
      awareness of IPv6 header compression (with the IPv6 over Low-Power
      Wireless Personal Area Network (6LoWPAN) standards) and of the
      possible benefits of IPv6 in those environments in terms of
      lowering the complexity of the overall system.

   -  The amount of energy consumed due to software update needs to be
      minimized.  For example, awakening a sleepy device regularly only
      to check for new software would seem wasteful if the device cannot
      feasibly be exploited while asleep.  However, the trade-off is
      that once the device awakens with old software, there may be a
      window of vulnerability if some relevant exploit has been
      discovered.

   -  The amount of storage required for update ought to be minimized
      and can sometimes be significant.  However, there are also
      benefits to schemes that store two or three different software
      images for robustness, e.g., if one has space for separate current
      last-known-good and being-updated images, then devices can better
      survive the buggy occasional updates that are also inevitable.

   Which of the features discussed in the list above are nice to have?
   Which are required?  Not all of these are required to achieve
   improvement.  Which are most important?

   Among the participants, there was consensus that supporting
   signatures (for integrity and authentication) of the firmware image
   itself and the need for partial updates were seen as important.

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   However, there were also concerns regarding the performance
   implications, since certain device categories may not utilize public
   key cryptography at all; hence, only a symmetric key approach seems
   viable, unless some other scheme such as a hash-based signature
   became practical (they currently aren't, due to signature size).
   This aspect raised concerns and triggered a discussion around the use
   of device management infrastructure, similar to Kerberos, that
   manages keys and distributes them to the appropriate parties.  As
   such, in this setup, there could be a unique key shared with the key
   distribution center; but for use with specific services (such as a
   software update service), a fresh and unique secret would be
   distributed.

   In addition to the requirements for the end devices, there are also
   infrastructure-related requirements.  The infrastructure may consist
   of servers in the local network and/or various servers deployed on
   the Internet.  It may also consist of some application-layer
   gateways.  The potential benefits of having such a local server might
   include:

   -  The local server acting for neighboring nodes.  For example, in a
      vehicle one microcontroller can process all firmware updates and
      redistribute the relevant parts of those to interconnected
      microcontrollers.

   -  Local infrastructure could perform some digital signature checks
      on behalf of the devices, e.g., certificate-revocation checking.

   -  Local multicast can enable transmission of the same update to many
      devices.

   -  Local servers can hide complexity associated with Network Address
      Translation (NAT) and firewalls from the device.

   Another point related to local infrastructure is that since many IoT
   devices will not be (directly) connected to the Internet, but only
   through a gateway, there may in any case be a need to develop a
   software/firmware update mechanism that works in environments where
   no end-to-end Internet connectivity exists.

   Some current firmware update schemes need to identify devices.
   Different design approaches are possible.

   -  In an extreme form in one case, the decision about updating a
      device is made by the infrastructure based on the unique device
      identification.  The operator of the firmware update
      infrastructure knows about the hardware and software requirements
      for the IoT devices, knows about the policy for updating the

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      device, etc.  The device itself is provisioned with credentials so
      that it can verify a firmware update coming from an authorized
      device.

   -  In another extreme, the device has knowledge about the software
      and hardware configuration and possible dependencies.  It consults
      software repositories to obtain those software packages that are
      most appropriate.  Verifying the authenticity of the software
      packages/firmware images will still be required.

   Hence, in some deployed software update mechanisms there is no desire
   for the device to be identified beyond the need to exchange
   information about the most recent software versions.  For other
   devices, it is seen as important to identify the device itself in
   order to provide the appropriate firmware image/software packages.

   Related to device identification, various privacy concerns arise,
   such as the need to determine what information is provided to whom
   and the uses to which this information is put.  For IoT devices where
   there is a close relationship to an individual (see [RFC6973]),
   privacy concerns are likely higher than for devices where such a
   relationship does not exist (e.g., a sensor measuring concrete).  The
   software/firmware update mechanism should, however, not make the
   privacy situation of IoT devices worse.  The proposal from the group
   was to introduce a minimal requirement of not sending any new
   identifiers over an unencrypted channel as part of an update
   protocol.

   However, software updates will provide yet another venue in which the
   tension between those advocating better privacy and those seeking to
   monetize information will play out.  It is in the nature of software
   update that it requires devices to sometimes "call home" and such
   interactions provide fertile ground for monetization.

4.  Authorizing a Software/Firmware Update

   There were quite a few points revolving around authorization:

   -  Who can accept or reject an update?  Is it the owner of the
      device, the user, or both?  The user may not necessarily be the
      owner.

   -  With products that fall under a regulatory structure, such as
      healthcare, you don't want firmware other than what has been
      accredited.

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   -  In some cases, it will be very difficult for a firmware update
      system to communicate to users that an update is available.  Doing
      so may require tracking the device and its status with regard to
      the installed firmware/software, with all the privacy downsides if
      such tracking is badly done.

   -  Not all updates are the same.  Security updates are often treated
      differently compared to feature updates, and the authorization for
      these may differ.

   -  Some people may choose to decline updates, often on the basis that
      their system is currently stable, but also possibly due to
      concerns about unwanted changes, such as the HP printer firmware
      update pushed in March 2016 [HP-Firmware] that turned off features
      that end users liked.

5.  End-of-Support

   There was quite a bit of discussion about end-of-support for
   products/devices and how to handle that.

   -  How should end-of-support or end-of-features be treated?  Devices
      are often deployed for 10+ years (or even longer in some
      verticals).  Device makers may not want or be able to support
      software and services for such an extended period of time.  Will
      these devices stop working after a certain, previously unannounced
      period of time, such as Eye-Fi cards [EYEFI]?

   -  There will be a broad range of device makers involved in IoT, who
      may differ substantially in terms of how well they can handle the
      full device life cycle.  Some will be large commercial enterprises
      that are used to dealing with long device lifetimes, whereas
      others may be very small commercial entities where the device
      lifetime may be longer than the company lifetime.  Yet other
      devices may be the result of open-source activities that prosper
      or flounder.  The problem of end-of-support arises in all these
      cases, though feasible solutions for software update may
      substantially differ.  In some cases, device makers may not be
      willing to continue to update devices, for example, due to a
      change in business strategies caused by a merger.  In yet other
      cases, a company may have gone bankrupt.

   -  While there are many legal, ethical, and business-related
      questions, can we technically enable transfer of device service to
      another provider?  Could there even be business models for
      entities that take over device updates for original device makers
      that no longer wish to handle software update?

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   -  The release of code, as it was done with the Little Printer
      manufactured and developed by a company called "Berg"
      [LittlePrinter], could provide a useful example.  While the
      community took over the support in that case, this can hardly be
      assumed in all cases.  Just releasing the source code for a device
      will not necessarily motivate others to work on the code, to fix
      bugs, or to maintain a service.  Nevertheless, escrowing code so
      that the community can take it over if a company fails is one
      possible option.

   -  The situation gets more complex when the device has security
      mechanisms to ensure that only selected parties are allowed to
      update the device (which is really a basic requirement for any
      secure software update).  In this case, private signing keys (or
      similar) may need to be made available as well, which could
      introduce security problems for already-deployed software.  In the
      best case, it changes assumptions made about the trust model and
      about who can submit updates.

   -  How should deployed devices behave when they are end-of-support
      and support ends?  Many of them may still function normally, but
      others may fail due to the absence of cloud infrastructure
      services.  Some products are probably expected to fail safely,
      similarly to a smoke alarm that makes a loud noise when the
      battery becomes empty.  Cell phones without a contract can, in
      some countries, still be used for emergency services (although at
      the expense of society due to untraceable hoax calls), as
      discussed in RFC 7406 [RFC7406].

   The recommendation that can be provided to device makers and users is
   to think about the end-of-support and end-of-support scenarios ahead
   of time and plan for those.  While device makers rarely want to
   consider what happens if their business fails, it is definitely
   legitimate to consider scenarios where they are hugely successful and
   want to evolve a product line instead of supporting previously sold
   products forever.  Maybe there is also value in subscription-based
   models where product and device support is only provided as long as
   the subscription is paid.  Without a subscription, the product is
   deactivated and cannot pose a threat to the Internet at large.

Top      ToC       Page 15 
6.  Incentives

   Workshop participants also discussed how to create incentives for
   companies to ship software updates, which is particularly important
   for products that will be deployed in the market for a long time.  It
   is also further complicated by complex value chains.

   -  Companies shipping software updates benefit from improved
      security.  Their devices are less likely to be abused as a vector
      to launch other attacks, whether on their own networks or (as part
      of a botnet) on other Internet hosts.  This clearly creates an
      incentive to support and use software updates.

   -  On the other hand, updates can also break things.  The negative
      customer experience can be due to service interruptions during or
      after the update process but can also result from bad experience
      from deliberate changes introduced as part of an update -- such as
      a feature that is not available anymore, or a "bug" that another
      service has relied upon being fixed.

   -  For most classes of device, there does not seem to be a regulatory
      requirement to report or fix vulnerabilities, similar to data-
      breach-notification laws.

   -  Subscription models for device management were suggested so that
      companies providing the service have an economic interest in
      keeping devices online (and updated for that).

7.  Measurements and Analysis

   From a security point of view, it is important to know what devices
   are out there and what version of software they run.  One workshop
   paper [PLONKA] reported measurements that were initially done on
   buggy devices first distributed in 2003, and that were still
   detectable in significant numbers just before the workshop 13 years
   later.  As such, in addition to the firmware update mechanism,
   companies have been offering device management solutions that allow
   OEMs to keep track of their devices.  Tracking these devices and
   their status is still challenging since some devices are only
   connected irregularly or are only turned on when needed (such as a
   hockey alarm that is only turned on before a match).

Top      ToC       Page 16 
   Various stakeholders have a justified interest in knowing something
   about deployed devices.  For example:

   -  Manufacturers and other players in the supply chain are interested
      to know what devices are out there, how many have been sold, and
      what devices are out there but have not been sold.  This could
      help to understand which firmware versions to support and for how
      long.

   -  Device users, owners, and customers like these may want to know
      what devices are installed over a longer period of time, what
      software/firmware version is the device running, what is the
      uptime of each of these devices, what types of faults have
      occurred, etc.  Forgotten devices may pose problems, particularly
      if they (have the potential to) behave badly.

   -  To an extent, network operators offering services to device owners
      and other actors may also need similar information, for example,
      to control botnets.

   -  Researchers doing analysis on the state of the Internet ecosystem
      (such as what protocols are being used, how much data IoT devices
      generate, etc.,) need measurements for their work.

   There can easily be some invasiveness in approaches to acquiring such
   measurements.  The challenge was put forward to find ways to create
   measurement infrastructures that are privacy preserving.  Arnar
   Birgisson noted that there are privacy-preserving statistical
   techniques, such as RAPPOR [RAPPOR], and Ned Smith added that
   techniques like Intel's Enhanced Privacy ID (EPID) may play a role in
   maintaining some level of anonymity for the IoT device (owners) while
   also enabling measurement.  It seemed clear that naive approaches to
   measurement (e.g., where devices are willing to expose a unique
   identifier to anyone on request) are unlikely to prove sufficient.

8.  Firmware Distribution in Mesh Networks

   There was some discussion of the requirements for mesh-based
   networks, mainly relating to industrial lighting.  In these networks,
   software update can impose unacceptable performance burdens,
   especially if there are many devices, some of which may be sleepy.

   The workshop discussed whether some forms of multicast (perhaps not
   IP multicast) would be needed to provide acceptable solutions for
   software update in such cases.  It was not clear at which layer a
   multicast solution might be effective in such cases, though there did
   not seem to be any clearly applicable standards-based approach that
   was available at the time of the workshop.

Top      ToC       Page 17 
9.  Compromised Devices

   There was recognition that there are, and perhaps always will be,
   large numbers of devices that can be, or have been, compromised.
   While updating these can mitigate problems, there will always be new
   devices added to networks that cannot be updated (for various
   reasons); so the question of what, if anything, to do about
   compromised devices was discussed.

   -  There may be value if it were possible to single out a device that
      shows faulty behavior or has been compromised, and to shut it down
      in some sense.

   -  Prior work in the IETF on Network Endpoint Assessment (NEA) [NEA]
      allowed assessing the "posture" of devices.  Posture refers to the
      hardware or software configuration of a device and may include
      knowledge that the software installed is up to date.  The obtained
      information can then be used by some network infrastructure to
      create a quarantined region network around the device.

   -  RFC 6561 [RFC6561] describes one scheme for an ISP to send
      "signals" to customers about hosts (usually those that are part of
      a botnet or generating spam) in their home network.

   -  Neither RFC 6561 nor NEA has found widespread deployment.  Whether
      such mechanisms can be more successful in the IoT environment has
      yet to be studied.

   The conclusion of the discussion at the workshop itself was that
   there is some interest in identifying and stopping misbehaving
   devices, but the actual solution mechanisms are unclear.

10.  Miscellaneous Points

   There were a number of points discussed at the workshop that don't
   neatly fit under the above headings but that are worth recording.
   Those include:

   -  Complex questions can arise when considering the impact of the
      lack of updates on other devices, other persons, or the public in
      general.  If I don't update my device, and it is used to attack a
      random host on the Internet, but at no apparent cost to me, then
      what incentive do I have to do updates that would have protected
      that random host?  What incentive has my device's vendor to have
      provided those updates in advance?  An example of such a case can
      be found in DDoS attacks from IoT devices, such as printers
      [SNMP-DDOS] and cameras [DDOS-KREBS].

Top      ToC       Page 18 
   -  With some IoT devices, there are many stakeholders contributing to
      the end product (e.g., contributing different subsystems).
      Ensuring that vulnerabilities are fixed and software/firmware
      updates are communicated through the value chain is known to be
      difficult, as demonstrated in [OS14].

   -  What about forgotten devices?  There are many such, and there will
      be more.  Even though they are forgotten, such devices may be
      useless consumers of electricity, or they may be part of some
      critical system.

   -  Can we determine whether an update impacts other devices in the
      Internet?  Updates to one device can have unintended impact on
      other devices that depend on it.  This can have cascading effects
      if we are not careful.  Changing the format of the output of a
      sensor could have cascading impacts, e.g., if some actuator reacts
      to the presence/absence of that sensor's data.

   -  How should a device behave when it is running out-of-date
      software?  The example of a smoke alarm was mentioned.  We don't
      want 100 devices in a living room to start beeping when their
      batteries run low or when they cannot communicate with the cloud.
      But are devices supposed to simply stop working?

   -  The IETF has published a specification that uses the Cryptographic
      Message Syntax (CMS) to protect firmware packages, as described in
      RFC 4108 [RFC4108], which also contains metadata to describe the
      firmware image itself.  During the workshop, the question was
      raised whether a solution will, in the future, be needed that is
      post-quantum secure.  A post-quantum cryptosystem is a system that
      is secure against quantum computers that have more than a trivial
      number of quantum bits.  It is open to conjecture whether it is
      feasible to build such a machine, but current signature algorithms
      are known not to be post-quantum secure.  This would require
      introducing technologies like the Hash-based Merkle Tree Signature
      (MTS) [HOUSLEY], which was presented and discussed at the
      workshop.  The downsides of such solutions are their novelty and,
      for these use cases, the fairly large signature or key sizes
      involved; e.g., depending on the parameters, a signature could
      easily have a size of 5-10 KiB [HASHSIG] [XMSS].  While it is
      likely that post-quantum secure signature algorithms will be
      needed for software updates at some point in time, it may be the
      case that such algorithms will be needed sooner for services
      requiring long-term confidentiality, (e.g., using Transport Layer
      Security (TLS)), so it was not clear that this application would
      be a first-mover in terms of post-quantum security.

Top      ToC       Page 19 
   -  Many devices that use certificates do not check the revocation
      status of certificates, even though extensions like Online
      Certificate Status Protocol (OCSP) stapling exists [RFC6961] and
      is increasingly deployed with Web browsers.  The workshop
      participants did not reach a conclusion regarding the
      recommendations of certificate revocation checking, although the
      importance has been recognized.  The reluctance regarding
      deploying certificate revocation deserves further investigation.

11.  Tentative Conclusions and Next Steps

   The workshop participants discussed some tentative conclusions and
   possible next steps:

   -  There was strong agreement that having some standardized secure
      (authorized and authenticated) software update would be an
      improvement over having none.

   -  It would be valuable to find agreement on the right scope for a
      standardized software/firmware update mechanism.  It is not clear
      that an entire update system can or should be standardized, but
      there may be some aspects of such solutions where standards would
      be beneficial, e.g., (meta-)data formats and/or protocols for
      distributing firmware updates.  More discussion is needed to
      identify which parts of the problem space could benefit from
      standardization.

   -  It will be useful to investigate solutions to install updates with
      no operational interruption as well as ways to distribute software
      updates without disrupting network operations (specifically, in
      low-power wireless networks), including the development of a
      multicast transfer mechanism (with appropriate security).

   -  There will almost certainly be a need for a way to transfer
      authority/responsibility for updates, particularly considering
      end-of-support cases.  This is very close to calling for a
      standard way to "root" devices as a feature of all devices.

   -  We would benefit from documentation of proofs-of-concept of
      software/firmware updates for constrained devices on different
      operating system architectures.  The IETF Light-Weight
      Implementation Guidance (lwig) Working Group may be a good venue
      for such documents.

Top      ToC       Page 20 
12.  Security Considerations

   This document summarizes an IAB workshop on software/firmware updates
   and the entire content is, therefore, security related.
   Standardizing and deploying a software/firmware update mechanism for
   use with IoT devices could help fix security vulnerabilities faster
   and, in some cases, be the only via to get vulnerability patched at
   all.

13.  IANA Considerations

   This document does not require any IANA actions.

14.  Informative References

   [BB14]     Barrett, B., "Winks Outage Shows Us How Frustrating Smart
              Homes Could Be", April 2014,
              <http://www.wired.com/2015/04/smart-home-headaches/>.

   [BS14]     Schneier, B., "The Internet of Things Is Wildly Insecure
              -- And Often Unpatchable", January 2014,
              <https://www.schneier.com/essays/archives/2014/01/
              the_internet_of_thin.html>.

   [BSDIFF]   Percival, C., "Matching with Mismatches and Assorted
              Applications", September 2016,
              <https://ora.ox.ac.uk/objects/
              uuid:4f0d53cc-fb9f-4246-a835-3c8734eba735/datastreams/
              THESIS01>.

   [COURGETTE]
              Google, "Software Updates: Courgette", September 2016,
              <https://www.chromium.org/developers/design-documents/
              software-updates-courgette>.

   [DDOS-KREBS]
              Goodin, D., "Record-breaking DDoS reportedly delivered by
              >145k hacked cameras", September 2016,
              <http://arstechnica.com/security/2016/09/botnet-of-145k-
              cameras-reportedly-deliver-internets-biggest-ddos-ever/>.

   [EYEFI]    Aldred, J., "Eye-Fi to Drop Suport for Some Cards. They
              Will 'Magically' Stop Working on September 16, 2016", June
              2016, <http://www.diyphotography.net/eyefi-drop-support-
              cards-will-magically-stop-working-september-16-2016/>.

Top      ToC       Page 21 
   [FTC]      Federal Trade Commission, "FTC Report on Internet of
              Things Urges Companies to Adopt Best Practices to Address
              Consumer Privacy and Security Risks", January 2015,
              <https://www.ftc.gov/system/files/documents/reports/
              federal-trade-commission-staff-report-november-2013-
              workshop-entitled-internet-things-
              privacy/150127iotrpt.pdf>.

   [HASHSIG]  Langley, A., "Hash based signatures", July 2013,
              <https://www.imperialviolet.org/2013/07/18/hashsig.html>.

   [HOUSLEY]  Housley, R., "Use of the Hash-based Merkle Tree Signature
              (MTS) Algorithm in the Cryptographic Message Syntax
              (CMS)", Work in Progress, draft-housley-cms-mts-hash-
              sig-07, June 2017.

   [HP-Firmware]
              BoingBoing, "HP detonates its timebomb: printers stop
              accepting third party ink en masse", September 2016,
              <http://boingboing.net/2016/09/19/
              hp-detonates-its-timebomb-pri.html>.

   [IoTSU]    IAB, "Internet of Things Software Update Workshop (IoTSU)
              2016", June 2016,
              <https://www.iab.org/activities/workshops/iotsu/>.

   [LittlePrinter]
              Berg, "The future of Little Printer", September 2014,
              <http://littleprinterblog.tumblr.com/post/97047976103/
              the-future-of-little-printer>.

   [NEA]      IETF, "Network Endpoint Assessment (nea) Concluded WG",
              October 2016,
              <https://datatracker.ietf.org/wg/nea/charter/>.

   [OS-Support]
              Dong, W., Chen, C., Liu, X., and J. Bu, "Providing OS
              Support for Wireless Sensor Networks: Challenges and
              Approaches", DOI 10.1109/SURV.2010.032610.00045, May 2010,
              <http://ieeexplore.ieee.org/stamp/
              stamp.jsp?arnumber=5462978>.

   [OS14]     Oppenheim, L. and S. Tal, "Too Many Cooks: Exploiting the
              Internet of TR-069 Things", December 2014,
              <http://mis.fortunecook.ie/
              too-many-cooks-exploiting-tr069_tal-oppenheim_31c3.pdf>.

Top      ToC       Page 22 
   [PACMAN]   "pacman", 2016, <https://www.archlinux.org/pacman/>.

   [PLONKA]   Plonka, D. and E. Boschi, "The Internet of Things Old and
              Unmanaged", June 2016,
              <https://down.dsg.cs.tcd.ie/iotsu/subs/
              IoTSU_2016_paper_25.pdf>.

   [RAPPOR]   Erlingsson, U., Pihur, V., and A. Korolova, "RAPPOR",
              DOI 10.1145/2660267.2660348, July 2014,
              <http://dl.acm.org/citation.cfm?doid=2660267.2660348>.

   [RFC4108]  Housley, R., "Using Cryptographic Message Syntax (CMS) to
              Protect Firmware Packages", RFC 4108,
              DOI 10.17487/RFC4108, August 2005,
              <https://www.rfc-editor.org/info/rfc4108>.

   [RFC6561]  Livingood, J., Mody, N., and M. O'Reirdan,
              "Recommendations for the Remediation of Bots in ISP
              Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012,
              <https://www.rfc-editor.org/info/rfc6561>.

   [RFC6961]  Pettersen, Y., "The Transport Layer Security (TLS)
              Multiple Certificate Status Request Extension", RFC 6961,
              DOI 10.17487/RFC6961, June 2013,
              <https://www.rfc-editor.org/info/rfc6961>.

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973,
              DOI 10.17487/RFC6973, July 2013,
              <https://www.rfc-editor.org/info/rfc6973>.

   [RFC7406]  Schulzrinne, H., McCann, S., Bajko, G., Tschofenig, H.,
              and D. Kroeselberg, "Extensions to the Emergency Services
              Architecture for Dealing With Unauthenticated and
              Unauthorized Devices", RFC 7406, DOI 10.17487/RFC7406,
              December 2014, <https://www.rfc-editor.org/info/rfc7406>.

   [RPM]      "Red Hat Package Manager (RPM)", 2016, <http://rpm.org/>.

   [RT]       Google, "Roughtime", September 2016,
              <https://roughtime.googlesource.com/roughtime>.

   [SNMP-DDOS]
              BITAG, "SNMP Reflected Amplification DDoS Attack
              Mitigation", August 2012,
              <https://www.bitag.org/documents/
              SNMP-Reflected-Amplification-DDoS-Attack-Mitigation.pdf>.

Top      ToC       Page 23 
   [WP29]     Article 29 Data Protection Working Party, "Opinion 8/2014
              on the on Recent Developments on the Internet of Things",
              14/EN, WP 223, September 2014,
              <http://ec.europa.eu/justice/data-protection/article-
              29/documentation/opinion-recommendation/files/2014/
              wp223_en.pdf>.

   [XMSS]     Huelsing, A., Butin, D., Gazdag, S., Rijneveld, J., and A.
              Mohaisen, "XMSS: Extended Hash-Based Signatures", Work in
              Progress, draft-irtf-cfrg-xmss-hash-based-signatures-10,
              July 2017.

Top      ToC       Page 24 
Appendix A.  Program Committee

   The following individuals helped to organize the workshop: Jari
   Arkko, Arnar Birgisson, Carsten Bormann, Stephen Farrell, Russ
   Housley, Ned Smith, Robert Sparks, and Hannes Tschofenig.

Appendix B.  Accepted Position Papers

   The list of accepted position papers is below.  Links to these, and
   to the workshop agenda and raw minutes are accessible at:
   <https://down.dsg.cs.tcd.ie/iotsu/>.

   -  R. Housley, "Position Paper for Internet of Things Software Update
      Workshop (IoTSU)"

   -  D. Thomas and A. Beresford, "Incentivising software updates"

   -  L. Zappaterra and E. Dijk, "Software Updates for Wireless
      Connected Lighting Systems: requirements, challenges and
      recommendations"

   -  M. Orehek and A. Zugenmaier, "Updates in IoT are more than just
      one iota"

   -  D. Plonka and E. Boschi, "The Internet of Things Old and
      Unmanaged"

   -  D. Bosschaert, "Using OSGi for an extensible, updatable and future
      proof IoT"

   -  A. Padilla, E. Baccelli, T. Eichinger, and K. Schleiser, "The
      Future of IoT Software Must be Updated"

   -  T. Hardie, "Software Update in a multi-system Internet of Things"

   -  R. Sparks and B. Campbell, "Avoiding the Obsolete-Thing Event
      Horizon"

   -  J. Karkov, "SW update for Long lived products"

   -  S. Farrell, "Some Software Update Requirements"

   -  S. Chakrabarti, "Internet Of Things Software Update Challenges:
      Ownership, Software Security & Services"

   -  M. Kovatsch, A. Scholz, and J. Hund, "Why Software Updates Are
      More Than a Security Issue: Challenges for IETF CoRE and the W3C
      Web of Things"

Top      ToC       Page 25 
   -  A. Grau, "Secure Software Updates for IoT Devices"

   -  Birr-Pixton, "Electric Imp's experiences of upgrading half a
      million embedded devices"

   -  Y. Zhang, J. Yin, C. Groves, and M. Patel, "oneM2M device
      management and software/firmware update"

   -  E. Smith, M. Stitt, R. Ensink, and K. Jager, "User Experience (UX)
      Centric IoT Software Update"

   -  J.-P. Fassino, E.A. Moktad, and J.-M. Brun, "Secure Firmware
      Update in Schneider Electric IOT-enabled offers"

   -  M. Orehek, "Summary of existing firmware update strategies for
      deeply embedded systems"

   -  N. Smith, "Toward A Common Modeling Standard for Software Update
      and IoT Objects"

   -  S. Schmidt, M. Tausig, M. Hudler, and G. Simhandl, "Secure
      Firmware Update Over the Air in the Internet of Things Focusing on
      Flexibility and Feasibility"

   -  A. Adomnicai, J. Fournier, L. Masson, and A. Tria, "How careful
      should we be when implementing cryptography for software update
      mechanisms in the IoT?"

   -  V. Prevelakis and H. Hamad, "Controlling Change via Policy
      Contracts"

   -  H. Birkholz, N. Cam-Winget, and C. Bormann, "IoT Software Updates
      need Security Automation"

   -  R. Bisewski, "Comparative Analysis of Distributed Repository
      Update Methodology and How CoAP-like Update Methods Could
      Alleviate Internet Strain for Devices that Constitute the Internet
      of Things"

   -  J. Arrko, "Architectural Considerations with Smart Objects and
      Software Updates"

   -  J. Jimenez and M. Ocak, "Software Update Experiences for IoT"

   -  H. Tschofenig, "Software and Firmware Updates with the OMA LWM2M
      Protocol"

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Appendix C.  List of Participants

   -  Arnar Birgisson, Google

   -  Alan Grau, IconLabs

   -  Alexandre Adomnicai, Trusted Objects

   -  Alf Zugenmaier, Munich University of Applied Science

   -  Ben Campbell, Oracle

   -  Carsten Bormann, TZI University Bremen

   -  Daniel Thomas, University of Cambridge

   -  David Bosschaert, Adobe

   -  David Malone, Maynooth University

   -  David Plonka, Akamai

   -  Doug Leith, Trinity College Dublin

   -  Emmanuel Baccelli, Inria

   -  Eric Smith, SpinDance

   -  Jean-Philippe Fassino, Schneider Electric

   -  Joergen Karkov, Grundfos

   -  Jonathon Dukes, Trinity College Dublin

   -  Joseph Birr-Pixton, Electric Imp

   -  Kaspar Schleiser, Freie Universitaet Berlin

   -  Luca Zappaterra, Philips Lighting Research

   -  Martin Orehek, Munich University of Applied Science

   -  Mathias Tausig, FH Campus Wien

   -  Matthias Kovatsch, Siemens

   -  Milan Patel, Huawei

Top      ToC       Page 27 
   -  Ned Smith, Intel

   -  Robert Ensink, SpinDance

   -  Robert Sparks, Oracle

   -  Russ Housley, Vigil Security

   -  Samita Chakrabarti, Ericsson

   -  Stephen Farrell, Trinity College Dublin

   -  Vassilis Prevelakis, TU Braunschweig

   -  Hannes Tschofenig, ARM Ltd.

Acknowledgements

   We would like to thank all paper authors and participants for their
   contributions.  The IoTSU workshop is co-sponsored by the Internet
   Architecture Board and the Science Foundation Ireland funded CONNECT
   Centre for future networks and communications.  The program committee
   would like to express their thanks to Comcast for sponsoring the
   social event.

Authors' Addresses

   Hannes Tschofenig
   ARM Limited

   Email: hannes.tschofenig@gmx.net


   Stephen Farrell
   Trinity College Dublin
   Dublin  2
   Ireland

   Phone: +353-1-896-2354
   Email: stephen.farrell@cs.tcd.ie