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Versions: 00 01 02 draft-ietf-ace-usecases

ACE Working Group                                          L. Seitz, Ed.
Internet-Draft                                       SICS Swedish ICT AB
Intended status: Informational                            S. Gerdes, Ed.
Expires: January 3, 2015                         Universitaet Bremen TZI
                                                             G. Selander
                                                                Ericsson
                                                                 M. Mani
                                                                   Itron
                                                                S. Kumar
                                                        Philips Research
                                                           July 02, 2014


                             ACE use cases
                      draft-seitz-ace-usecases-01

Abstract

   This document presents use cases for authentication and access
   control in scenarios involving constrained RESTful devices.  Where
   specific details are relevant, it is assumed that the devices use
   CoAP as communication protocol, however most conclusions apply
   generally.

   A number of security requirements are derived from the use cases,
   which are intended as a guideline for developing a comprehensive
   authentication and access control approach for this class of
   scenarios.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 3, 2015.

Copyright Notice




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   Copyright (c) 2014 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Container monitoring . . . . . . . . . . . . . . . . . . .  4
       2.1.1.  Bananas for Munich . . . . . . . . . . . . . . . . . .  4
       2.1.2.  Requirements . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Home Automation  . . . . . . . . . . . . . . . . . . . . .  5
       2.2.1.  Remotely letting in a visitor  . . . . . . . . . . . .  6
       2.2.2.  Requirements . . . . . . . . . . . . . . . . . . . . .  6
     2.3.  Personal Health Monitoring . . . . . . . . . . . . . . . .  7
       2.3.1.  John and the heart rate monitor  . . . . . . . . . . .  7
       2.3.2.  Requirements . . . . . . . . . . . . . . . . . . . . .  8
     2.4.  Building Automation  . . . . . . . . . . . . . . . . . . .  9
       2.4.1.  Device Lifecycle . . . . . . . . . . . . . . . . . . .  9
       2.4.2.  Requirements . . . . . . . . . . . . . . . . . . . . . 11
     2.5.  Smart Metering . . . . . . . . . . . . . . . . . . . . . . 12
       2.5.1.  Drive-by metering  . . . . . . . . . . . . . . . . . . 12
       2.5.2.  Meshed Topology  . . . . . . . . . . . . . . . . . . . 13
       2.5.3.  Customer Direct Access to the metering Data  . . . . . 13
       2.5.4.  Requirements . . . . . . . . . . . . . . . . . . . . . 13
   3.  Consolidated Requirements From The Use Cases . . . . . . . . . 14
     3.1.  General Security Requirements  . . . . . . . . . . . . . . 14
     3.2.  Authentication Requirements  . . . . . . . . . . . . . . . 15
     3.3.  Access Control Requirements  . . . . . . . . . . . . . . . 15
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   5.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 18
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   7.  Informative References . . . . . . . . . . . . . . . . . . . . 20
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21






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1.  Introduction

   This document presents use cases in an attempt to analyze the
   authentication and access control requirements in an Internet of
   Things setting.  This setting features constrained devices [RFC7228]
   communicating over the Internet.
   Some of these devices may have very low capacity in terms of memory
   and processing power, and may additionally be limited by the fact
   that they run on battery power.

   These devices offer resources such as sensor data and actuators,
   which are accessed by clients, sometimes without human intervention
   (M2M).  In some situations the communication will happen through
   intermediaries (e.g. gateways, proxies).

   Where specific detail is necessary it is assumed that the devices
   communicate using the CoAP protocol [RFC7252], although most
   conclusions are generic.

1.1.  Terminology

   Resource Server (RS): The constrained device which hosts resources
   the Client wants to access.

   Client (C): A device which wants to access a resource on the Resource
   Server.
   This could also be a constrained device.

   Resource Owner (RO): The subject who owns the resource and controls
   its access permissions.





















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2.  Use Cases

   This section lists use cases involving constrained devices with
   security requirements.  Each use case first presents a general
   description of the application area, then one or more specific use
   cases, and finally the resulting requirements.  We assume that basic
   communication security requirements apply for all of these scenarios.

2.1.  Container monitoring

   The ability of sensors to communicate environmental data wirelessly
   opens up new application areas.  The use of such sensor systems makes
   it possible to continuously track and transmit specific
   characteristics such as temperature, humidity and gas content during
   the transportation and storage of goods.

   The proper handling of the sensors in this scenario is not easy to
   accomplish.  They have to be associated to the appropriate pallet of
   the respective container.  Moreover, the goods and the corresponding
   sensors belong to specific customers.

   During the shipment to their destination the goods often pass stops
   where they are transloaded to other means of transportation, e.g.
   from ship transport to road transport.

   The transportation and storage of perishable goods is especially
   challenging since they have to be stored at a constant temperature
   and with proper ventilation.  Additionally, it is very important for
   the vendors to be informed about irregularities in the temperature
   and ventilation of fruits to avoid the delivery of decomposed fruits
   to their customers.  The need for a constant monitoring of perishable
   goods has led to projects such as The Intelligent Container
   (http://www.intelligentcontainer.com).

2.1.1.  Bananas for Munich

   A fruit vendor grows bananas in Costa Rica for the German market.  It
   instructs a transport company to deliver the goods via ship to
   Rotterdam where they are picked up by trucks and transported to a
   ripening facility.  A Munich supermarket chain buys ripened bananas
   from the fruit vendor and transports them with their own company
   trucks.

   The fruit vendor's quality management wants to assure the quality of
   their products and thus equips the banana boxes with sensors.  The
   state of the goods is monitored consistently during shipment and
   ripening and abnormal sensor values are recorded.  Additionally, the
   sensor values are used to control the climate within the cargo



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   containers.

   The personnel that transloades the goods must be able to locate the
   goods meant for a specific customer.  However the fruit vendor does
   not want to disclose sensor information pertaining to the condition
   of the goods to other companies.

   When the goods arrive at the supermarket in Munich, the supermarket
   conducts its own quality check.  If no anomalies occurred during the
   transport, the bananas are admitted for sale.

2.1.2.  Requirements

   o  U1.1 The fruit vendor must be able to allow the transport company
      and the delivery service to access the position data on the
      monitoring devices.  Other state information must not be
      accessible.

   o  U1.2 The climate regulation system in the containers must be able
      to access the monitoring devices' state information to regulate
      the climate accordingly, without manual intervention of the
      resource owner.

   o  U1.3 The fruit vendor must be able to allow the fruit vendor's
      quality management to access the recorded state information on the
      monitoring devices.

   o  U1.4 Since the fruit vendor does not want other companies to be
      able to read sensor information, there should be some access
      control for the monitoring devices' state information.

2.2.  Home Automation

   Automation of the home has the potential to become a big future
   market for the Internet of Things.  A home automation system connects
   electrical devices in a house to the Internet and thus makes them
   accessible and manageable remotely.  Such devices might control for
   example heating, ventilation, lighting, home entertainment or home
   security.

   Such a system needs to accommodate a number of regular users
   (inhabitants, close friends, cleaning personnel) as well as a
   heterogeneous group of dynamically varying users (visitors,
   repairmen, delivery men).

   The security required by the systems in a automated home varies,
   however it is clear that the security system controlling e.g. the
   door-locks and alarms needs to be at least as secure as for a



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   comparable unautomated home.

   As the users are not typically trained in security (or even computer
   use), the configuration must use secure default settings, and the
   interface must be well adapted to novice users.

2.2.1.  Remotely letting in a visitor

   Jane is the owner of a flat with automated connected door-locks and
   alarm system, that allow her to remotely control them through a web
   interface or mobile application.  To allow for centralized management
   of both locks and the alarm system, they need to be able to
   communicate with both the web interface and the mobile application
   using a standardized, secure protocol.

   Jane has invited her acquaintance Jeffrey over for dinner, but is
   stuck in traffic and can not arrive in time, while Jeffrey who uses
   the subway will arrive punctually.  Jane calls Jeffrey and offers him
   to let him in remotely, so he can make himself comfortable while
   waiting.

   Jeffrey downloads an application that lets him communicate with
   Jane's door-lock and alarm system.  Then Jane sets permissions for
   Jeffery that allow him to open the door, and shut down the alarm when
   he arrives.

2.2.2.  Requirements

   o  U2.1 Jane needs to be able to spontaneously provision
      authentication means to Jeffrey.

   o  U2.2 Jane must be able to spontaneously change the access control
      policies.

   o  U2.3 Jane needs to be able to apply different rights for different
      users.

   o  U2.4 Jane must be able to apply context-based conditions
      (presence, time) to authorizations, and the devices (door-lock or
      alarm) need to be able to verify these conditions.

   o  U2.5 The security mechanisms of the door-lock and the alarm in
      Jane's home need to be able to communicate with different control
      devices (e.g.  Jeffrey's mobile phone).

   o  U2.6 The access control configuration of Jane's home needs to be
      secure by default.




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   o  U2.7 It must be easy for Jane to edit the access control policies
      for her home, even remotely and easy for Jeffrey to get access
      with correct authorization.

2.3.  Personal Health Monitoring

   The use of wearable health monitoring technology is expected to grow
   strongly, as a multitude of novel devices are developed and marketed.
   The need for open industry standards to ensure interoperability
   between products has lead to initiatives such as Continua Alliance
   (continuaalliance.org) and Personal Connected Health Alliance
   (pchalliance.org).  Personal health devices are typically battery
   driven, and located physically on the user.  They monitor some bodily
   function, such as e.g. temperature, blood pressure, or pulse.  They
   are connected to the Internet through an intermediary base-station,
   using wireless technologies.  Through this connection they report the
   monitored data to some entity, which may either be the user herself,
   or some medical personnel in charge of the user.

   Medical data has always been considered as very sensitive, and
   therefore requires good protection against unauthorized disclosure.
   A frequent, conflicting requirement is the capability for medical
   personnel to gain emergency access, even if no specific access rights
   exist.  As a result, the importance of secure audit logs increases in
   such scenarios.

   Since the users are not typically trained in security (or even
   computer use), the configuration must use secure default settings,
   and the interface must be well adapted to novice users.  Parts of the
   system must operate with minimal maintenance.  Especially frequent
   changes of battery are unacceptable.

2.3.1.  John and the heart rate monitor

   John has a heart condition, that can result in sudden cardiac
   arrests.  He therefore uses a device called HeartGuard that monitors
   his heart rate and his position.  In case of a cardiac arrest it
   automatically sends an alarm to an emergency service, transmitting
   John's current location.  The HeartGuard also broadcasts emergency
   information in the neighborhood to notify doctors or people with
   certain skills who have been enrolled in an emergency program, e.g.
   people who got training in heart and lung rescue.  For doctors,
   medical information or diagnosis can be provided with the
   notification to improve immediate treatment.

   The device includes some smart logic, with which it identifies its
   owner John and allows him to configure the device's settings,
   including access control.



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   This prevents situation where someone else wearing that device can
   act as the owner and mess up the access control and security
   settings.

   John can configure additional persons that get notified in an
   emergency, for example his daughter Jill.  Furthermore the device
   stores data on John's heart rate, which can later be accessed by a
   physician to assess the condition of John's heart.

   However John is a rather private person, and is worried that Jill
   might use HeartGuard to monitor his location while there is no
   emergency.  Furthermore he doesn't want his health insurance to get
   access to the HeartGuard data, or even to the fact that he is wearing
   a HeartGuard, since they might refuse to renew his insurance if they
   decided he was too big a risk for them.

   NOTE: Monitoring of some state parameter (e.g. an alarm button) and
   the position of a person also fits well into an elderly care service.
   This is particularly useful for people suffering from dementia, where
   the relatives or caregivers need to be notified of the whereabouts of
   the person under certain conditions.  In this case it is not the
   patient that decides about access.

2.3.2.  Requirements

   o  U3.1 John must be able to pre-configure access rights to the
      position data for persons or groups, in the context of an
      emergency.

   o  U3.2 John must be able to selectively allow different persons or
      groups to access the heart rate data.

   o  U3.3 John must be able to block access to specific persons in an
      otherwise allowed group (e.g. doctors in an emergency), if he
      mistrusts them.

   o  U3.4 The security measures must consider the battery lifetime of
      the devices and should consume as little energy as possible.

   o  U3.5 The device must have secure access control settings by
      default.

   o  U3.6 The device's access control settings must be easy to
      configure for an authorized, non-technical user.

   o  U3.7 Security mechanisms on medical devices must not provide
      opportunities for denial of service attacks on the device.




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2.4.  Building Automation

   Buildings for commercial use such as shopping malls or office
   buildings nowadays are equipped increasingly with semi-automatic
   components to enhance the overall living quality and to save energy
   where possible.  This includes for example heating, ventilation and
   air condition (HVAC) as well as illumination and security systems
   such as fire alarms.

   Different areas of these buildings are often exclusively leased to
   different companies.  However they also share some of the common
   areas of the building.
   Accordingly, a company must be able to control the light and HVAC
   system of its own part of the building and must not have access to
   control rooms that belong to other companies.

   Some parts of the building automation system such as entrance
   illumination and fire alarm systems are controlled either by all
   parties together or by a service company.

2.4.1.  Device Lifecycle

2.4.1.1.  Installation and Commissioning

   A building is hired out to different companies for office space.
   This building features various automated systems, such as a fire
   alarm system, which is triggered by several smoke detectors which are
   spread out across the building.  It also has automated HVAC, lighting
   and physical access control systems.

   A vacant area of the building has been recently leased to company A.
   Before moving into its new office, Company A wishes to replace the
   lighting with a more energy efficient and a better light quality
   luminaries.  They hire an installation and commissioning company C to
   redo the illumination.  Company C is instructed to integrate the new
   lighting devices, which may be from multiple manufacturers, into the
   existing lighting infrastructure of the building which includes
   presence sensors, switches, controllers etc.

   Company C gets the necessary authorization from the service company
   to interact with the existing Building and Lighting Management System
   (BLMS).
   To prevent disturbance to other occupants of the building, Company C
   is provided authorization to perform the commissioning only during
   non-office hours and only to modify configuration on devices
   belonging to the domain of Company A's space.  After installation
   (wiring) of the new lighting devices, the commissioner adds the
   devices into the company A's lighting domain.



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   Once the devices are in the correct domain, the commissioner
   authorizes the interaction rules between the new lighting devices and
   existing devices like presence sensors.  For this, the commissioner
   creates the authorization rules on the BLMS which define which lights
   form a group and which sensors /switches/controllers are allowed to
   control which groups.  These authorization rules may be context based
   like time of the day (office or non-office hours) or location of the
   handheld lighting controller etc.

2.4.1.2.  Operational

   Company A's staff move into the newly furnished office space.  Most
   lighting is controlled by presence sensors which control the lighting
   of specific group of lights based on the authorization rules in the
   BLMS.  Additionally employees are allowed to manually override the
   lighting brightness and color in their office by using the switches
   or handheld controllers.  Such changes are allowed only if the
   authorization rules exist in the BLMS.  For example lighting in the
   corridors may not be manually adjustable.

   At the end of the day, lighting is dimmed down or switched off if no
   occupancy is detected even if manually overridden during the day.

   On a later date company B also moves into the same building, and
   shares some of the common spaces with company A. On a really hot day
   James who works for company A turns on the air condition in his
   office.  Lucy who works for company B wants to make tea using an
   electric kettle.  After she turned it on she goes outside to talk to
   a colleague until the water is boiling.  Unfortunately, her kettle
   has a malfunction which causes overheating and results in a
   smoldering fire of the kettle's plastic case.

   Due to the smoke coming from the kettle the fire alarm is triggered.
   Alarm sirens throughout the building are notified and alert the staff
   of both companies.  Additionally, the ventilation system of the whole
   building is closed off to prevent the smoke from spreading and to
   withdraw oxygen from the fire.  The smoke cannot get into James'
   office although he turned on his air condition because the fire alarm
   overrides the manual setting.

   The fire department is notified of the fire automatically and arrives
   within a short time.  After inspecting the damage and extinguishing
   the smoldering fire a fire fighter resets the fire alarm because only
   the fire department is authorized to do that.







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2.4.1.3.  Maintenance

   Company A's staff are annoyed that the lights switch off too often in
   their rooms if they work silently in front of their computer.
   Company A notifies the commissioning Company C about the issue and
   asks them to increase the delay before lights switch off.

   Company C again gets the necessary authorization from the service
   company to interact with the BLMS.  The commissioner's tool gets the
   necessary authorization from BMLS to send a configuration change to
   all lighting devices in Company A's offices to increase their delay
   before they switch off.

2.4.1.4.  Decommissioning

   Company A has noticed that the handheld controllers are often
   misplaced and hard to find when needed.  So most of the time staff
   use the existing wall switches for manual control.  Company A decides
   it would be better to completely remove handheld controllers and asks
   Company C to decommission them from the lighting system.

   Company C again gets the necessary authorization from the service
   company to interact with the BLMS.  The commissioner now deletes any
   rules that allowed handheld controllers authorization to control the
   lighting.  Additionally the commissioner instructs the BLMS to push
   these new rules to prevent cached rules at the end devices from being
   used.

2.4.2.  Requirements

   o  U4.1.  A user with sufficient authorization to a device should be
      able to transfer the device to a different authorization server.

   o  U4.2.  Authorization rules may be context-based.

   o  U4.3.  Devices can access resources on other devices only if a
      rule exists in the authorization server (default deny).

   o  U4.4 Devices can be authorized to control individual devices using
      unicast or multiple devices using multicast.

   o  U4.5.  Devices may cache authorization rules locally.

   o  U4.6.  Subsystems under different operational domains must be able
      to interoperate with each other if the domain owners agree.

   o  U4.7.  A user with sufficient authorization to a device should be
      able to remove the device from an authorization server.



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   o  U4.8.  Authorization server may have a mechanism to override
      locally cached rules at devices.

   o  U4.9.  Revocation of security credentials should be possible.

2.5.  Smart Metering

   Automated measuring of customer consumption is an established
   technology for electricity, water, and gas providers.  Increasingly
   these systems also feature networking capability to allow for remote
   management.  Such systems are in use for commercial, industrial and
   residential customers and require a certain level of security, in
   order to avoid economic loss to the providers, vulnerability of the
   distribution system, as well as disruption of services for the
   customers.

   The smart metering equipment for gas and water solutions is battery
   driven and communication should be used sparingly due to battery
   consumption.  Therefore the types of meters sleep most of the time,
   and only wake up every minute/hour to check for incoming
   instructions.  Furthermore they wake up a few times a day (based on
   their configuration) to upload their measured metering data.

   Different networking topologies exist for smart metering solutions.
   Based on environment, regulatory rules and expected cost, one or a
   mixture of these topologies may be deployed to collect the metering
   information.  Drive-By metering is one of the most current solutions
   deployed for collection of gas and water meters.

2.5.1.  Drive-by metering

   A company offers smart metering infrastructures and related services
   to various providers.  Among these is a water provider, who in turn
   supplies several residential complexes in a city.  The smart meters
   are installed in the end customer's homes to measure water
   consumption and thus generate billing data for the provider.  The
   meters do so by sending data to a base station.  Several base
   stations are installed around the city to collect the metering data.
   However in the denser urban areas, the base stations would have to be
   installed very close to the meters.  This would require a high number
   of base stations and expose this more expensive equipment to
   manipulation or sabotage.  The company has therefore chosen another
   approach, which is to drive around with a mobile base-station and let
   the meters connect to that in regular intervals in order to gather
   metering data.






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2.5.2.  Meshed Topology

   In another deployment, the water meters are installed in a building
   that already has power meters installed, the latter are mains
   powered, and are therefore not subject to the same power saving
   restrictions.  The water meters can therefore use the power meters as
   proxies, in order to achieve better connectivity.  This requires the
   security measures on the water meters to work through intermediaries.

2.5.3.  Customer Direct Access to the metering Data

   The provider also wishes to offer its customer limited access to some
   of the data on the metering devices, in order to allow them to check
   and optimize their consumption.  However the provider expects the
   company to implement measures to prevent tampering with the data
   relevant for billing.

2.5.4.  Requirements

   o  U5.1 If security information can be recovered by a physical attack
      on a meter, this information must not be usable in an attack on
      other parts of the metering infrastructure.

   o  U5.2 The meters must be able to perform fine-grained access
      control on the metering data and on the configuration while being
      offline.

   o  U5.3 Authentication and access control must function without
      online connection to a back-end server.

   o  U5.4 Since there are many smart meters deployed and reaching them
      is difficult, authentication and access control policy updates
      must not depend on directly (or worse manually) provisioning these
      updates to individual meters.

   o  U5.5 The authentication and access control measures must cope with
      the presence of intermediary proxies between the Resource Servers
      and the Client.













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3.  Consolidated Requirements From The Use Cases

   This section consolidates the requirements derived from the use cases
   above.  Note that not every single requirement applies to every
   Resource Server, however protocols should allow for all of these
   requirements to be fulfilled.

3.1.  General Security Requirements

   The following requirements refer to general security measures that
   are affected by the design of authentication and access control
   protocols.

   o  Protect the Resource Server against denial of service (U3.7)

      *  Minimize the number of protocol steps that an attacker can
         induce a Resource Server to perform without proper
         authentication and access control.

      *  Note well that for constrained devices this includes attacks
         that aim to drain the battery of the target.

   o  Authentication and access control measures must work when traffic
      from the Client to the Resource Server goes through intermediary
      nodes.  (U5.5)

      Rationale: In many deployments, there will be gateways, proxies,
      firewalls etc. between a Client and a Resource Server.  This means
      that e.g.  DTLS [RFC6347] client authentication can not be used to
      authenticate the Client.

   o  Minimize resource usage for authentication and access control on
      the constrained device(s) (U3.4)

      *  Minimize battery usage

         +  Minimize message exchanges required by security measures

         +  Minimize the size of authentication and access control data
            that is transmitted

         +  Minimize the size of code required and reuse existing code
            libraries

         +  Minimize memory and stack usage on the devices






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   o  Require secure default settings (U1.4, U2.6, U3.5, U4.3)

      Rationale: Many attacks exploit insecure default settings, and
      experience shows that default settings are frequently left
      unchanged by the end users.  Therefore the security protocols for
      constrained devices should require secure modes of use by default.

   o  Interoperability (U1.1, U2.5, U4.6)

      Rationale: Resource Owners may interact with Clients from various
      manufacturers and vice-versa.  For the overall system to function
      correctly the authentication and access control mechanisms need to
      work consistently.  This is best achieved by standardization.

   o  Usability (U2.7, U3.6)

      *  Keep response times reasonable

      *  Make authentication and access control transparent for human
         users where possible

      *  Make the administration of authentication and access control as
         simple as possible

3.2.  Authentication Requirements

   o  Standardized provisioning of authentication means to Clients and
      Resource Servers (U2.1, U4.1, U4.7)

      *  Allow for remote provisioning as an option

   o  Enable remote revocation of authentication means (U4.9, U5.4)

3.3.  Access Control Requirements

   o  Enforce the access control policies of the Resource Owner (all use
      cases)

      *  Provision of access control policies set by the Resource Owner
         to the Policy Decision Point [RFC2904] (which may be on the
         Resource Server or on another trusted entity).

      *  Apply the access control policies to incoming requests (this
         may be done by the Resource Server or by another trusted
         entity).






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   o  Allow for different rights to the same resource for different
      requesting entities (U1.1, U1.2, U2.3, U3.1, U3.2, U3.3, U5.2)

      Rationale: In some cases different types of users require
      different access rights, as opposed to all-or-nothing access
      control.

   o  Allow for fine-grained access control (U1.1, U1.2, U3.1, U3.2,
      U5.2) Resource Servers can host several resources, and a resource
      (e.g. an actuator) can have different settings.  In some cases
      access rights need to be different at this level of granularity.

   o  Support access control on multicast requests to several Resource
      Servers (U4.4)

   o  Access control must work when the Resource Server has intermittent
      connectivity (U4.5)

   o  The Resource Server should be able to evaluate context-based
      permissions (U2.4, U3.1, U4.2)


     Access may depend on local conditions e.g. access to health data in
     an emergency.  The Policy Decision Point must be able to take such
     conditions into account.

   o  Enable policy updates without re-provisioning individual devices
      (U2.2, U4.7, U4.8, U5.4)

      Rationale: Clients can change rapidly and re-provisioning might be
      prohibitively expensive.

   o  Do not require manual intervention of the Resource Owner in the
      access control process (U1.2, U3.1, U5.4).

      Rationale: Manually approving access requests, while being a
      common solution in web access control, does not scale well in an
      M2M scenario.

   o  Enable revocation of authorizations, also considering locally
      cached authorization information (U4.9)










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4.  Security Considerations

   This document lists security requirements for constrained devices,
   motivated by specific use cases.  Therefore the whole document deals
   with security considerations.














































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5.  Acknowledgments

   The authors would like to thank Olaf Bergmann, Sumit Singhal, John
   Mattson, Mohit Sethi, Carsten Bormann, Corinna Schmitt, Hannes
   Tschofenig, and Erik Wahlstroem for reviewing and/or contributing to
   the document.  Also, thanks to Markus Becker, Thomas Poetsch and
   Koojana Kuladinithi for their input on the container monitoring use
   case."











































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6.  IANA Considerations

   This document has no IANA actions.
















































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7.  Informative References

   [RFC2904]  Vollbrecht, J., Calhoun, P., Farrell, S., Gommans, L.,
              Gross, G., de Bruijn, B., de Laat, C., Holdrege, M., and
              D. Spence, "AAA Authorization Framework", RFC 2904,
              August 2000.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228, May 2014.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252, June 2014.




































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Authors' Addresses

   Ludwig Seitz (editor)
   SICS Swedish ICT AB
   Scheelevaegen 17
   Lund  223 70
   Sweden

   Email: ludwig@sics.se


   Stefanie Gerdes (editor)
   Universitaet Bremen TZI
   Postfach 330440
   Bremen  28359
   Germany

   Phone: +49-421-218-63906
   Email: gerdes@tzi.org


   Goeran Selander
   Ericsson
   Faroegatan 6
   Kista  164 80
   Sweden

   Email: goran.selander@ericsson.com


   Mehdi Mani
   Itron
   52, rue Camille Desmoulins
   Issy-les-Moulineaux  92130
   France

   Email: Mehdi.Mani@itron.com


   Sandeep S. Kumar
   Philips Research
   High Tech Campus
   Eindhoven  5656 AA
   The Netherlands

   Email: sandeep.kumar@philips.com





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