Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Informational                                  C. Doyle
Expires: October 9, 23, 2020                               Juniper Networks
                                                          April 07, 21, 2020

                         Secure Device Install
                        draft-ietf-opsawg-sdi-07
                        draft-ietf-opsawg-sdi-08

Abstract

   Deploying a new network device in a location where the operator has
   no staff of its own often requires that an employee physically travel
   to the location to perform the initial install and configuration,
   even in shared datacenters with "smart-hands" type support.  In many
   cases, this could be avoided if there were a secure way to initially
   provision the device.

   This document extends existing auto-install / Zero-Touch Provisioning
   mechanisms to make the process more secure.

   [ Ed note: Text inside square brackets ([]) is additional background
   information, answers to frequently asked questions, general musings,
   etc.  They will be removed before publication.  This document is
   being collaborated on in Github at: https://github.com/wkumari/draft-
   wkumari-opsawg-sdi.  The most recent version of the document, open
   issues, etc should all be available here.  The authors (gratefully)
   accept pull requests. ]

   [ Ed note: This document introduces concepts and serves as the basic
   for discussion - because of this, it is conversational, and would
   need to be firmed up before being published ]

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   4
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Example Scenario  . . . . . . . . . . . . . . . . . . . .   5
   3.  Vendor Role / Requirements  . . . . . . . . . . . . . . . . .   6
     3.1.  Device key generation . . . . . . . . . . . . . . . . . .   6
     3.2.  Certificate Publication Server  . . . . . . . . . . . . .   6
   4.  Operator Role / Responsibilities  . . . . . . . . . . . . . .   7
     4.1.  Administrative  . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Technical . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  Example Initial Customer Boot . . . . . . . . . . . . . .   8
   5.  Additional Considerations . . . . . . . . . . . . . . . . . .  11
     5.1.  Key storage . . . . . . . . . . . . . . . . . . . . . . .  11
     5.2.  Key replacement . . . . . . . . . . . . . . . . . . . . .  11
     5.3.  Device reinstall  . . . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Appendix A.  Changes / Author Notes.  . . . . . . . . . . . . . .  14
   Appendix B.  Demo / proof of concept  . . . . . . . . . . . . . .  15
     B.1.  Step 1: Generating the certificate. . . . . . . . . . . .  15
       B.1.1.  Step 1.1: Generate the private key. . . . . . . . . .  15
       B.1.2.  Step 1.2: Generate the certificate signing request. .  16
       B.1.3.  Step 1.3: Generate the (self signed) certificate
               itself. . . . . . . . . . . . . . . . . . . . . . . .  16
     B.2.  Step 2: Generating the encrypted config.  . . . . . . . .  16
       B.2.1.  Step 2.1: Fetch the certificate.  . . . . . . . . . .  16
       B.2.2.  Step 2.2: Encrypt the config file.  . . . . . . . . .  16  17
       B.2.3.  Step 2.3: Copy config to the config server. . . . . .  17
     B.3.  Step 3: Decrypting and using the config.  . . . . . . . .  17
       B.3.1.  Step 3.1: Fetch encrypted config file from config
               server. . . . . . . . . . . . . . . . . . . . . . . .  17
       B.3.2.  Step 3.2: Decrypt and use the config. . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   In a growing, global network, significant amounts of time and money
   are spent deploying new devices and "forklift" upgrading existing
   devices.  In many cases, these devices are in shared datacenters (for
   example, Internet Exchange Points (IXP) or "carrier neutral
   datacenters"), which have staff on hand that can be contracted to
   perform tasks including physical installs, device reboots, loading
   initial configurations, etc.  There are also a number of (often
   vendor proprietary) protocols to perform initial device installs and
   configurations - for example, many network devices will attempt to
   use DHCP [RFC2131]to get an IP address and configuration server, and
   then fetch and install a configuration when they are first powered
   on.

   The configurations of network devices contain a significant amount of
   security related and / or and/or proprietary information (for example, RADIUS
   [RFC2865] or TACACS+ [I-D.ietf-opsawg-tacacs] secrets).  Exposing
   these to a third party to load onto a new device (or using an auto-install auto-
   install techniques which fetch an unencrypted config file via TFTP
   [RFC1350]) or something similar, is an unacceptable security risk for
   many operators, and so they send employees to remote locations to
   perform the initial configuration work; this costs, time and money.

   There are some workarounds to this, such as asking the vendor to pre-
   configure the devices before shipping it; asking the smart-hands to
   install a terminal server; providing a minimal, unsecured
   configuration and using that to bootstrap to a complete
   configuration, etc; but these are often clumsy and have security
   issues - for example, in the terminal server case, the console port
   connection could be easily snooped.

   This document layers security onto existing auto-install solutions to
   provide a secure method to initially configure new devices.  It is
   optimized for simplicity, both for the implementor and the operator;
   it is explicitly not intended to be an "all singing, all dancing"
   fully featured system for managing installed / deployed devices, nor
   is it intended to solve all use-cases - rather it is a simple
   targeted solution to solve a common operational issue where the
   network device has been delivered, fibre laid (as appropriate) but
   there is no trusted member of the operator's staff to perform the
   initial configuration.

   Solutions such as Secure Zero Touch Provisioning (SZTP)" [RFC8572],
   [I-D.ietf-anima-bootstrapping-keyinfra] and similar are much more
   fully featured, but also more complex to implement and / or and/or are not
   widely deployed yet.

   This solution is specifically designed to be a simple method on top
   of exiting device functionality.  If devices do not support this new
   method, they can continue to use the existing functionality.  In
   addition, operators can choose to use this to protect their
   configuration information, or can continue to use the existing
   functionality.

   The issue of securely installing devices is in no way a new issue,
   nor is it limited to network devices; it occurs when deploying
   servers, PCs, IoT devices, and in many other situations.  While the
   solution described in this document is obvious (encrypt the config,
   then decrypt it with a device key), this document only discusses the
   use for network devices, such as routers and switches.

1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Overview

   Most network devices already include some sort of initial
   bootstrapping logic (sometimes called 'autoboot', or 'autoinstall').
   This generally works by having a newly installed / unconfigured
   device obtain an IP address and address of a config server (often
   called 'next-server', 'siaddr' or 'tftp-server-name') using DHCP (see
   [RFC2131]).  The device then contacts this configuration server to
   download its initial configuration, which is often identified using
   the devices serial number, MAC address or similar.  This document
   extends this (vendor specific) paradigm by allowing the configuration
   file to be encrypted.

   This document describes a concept, and some example ways of
   implementing this concept.  As devices have different capabilities,
   and use different configuration paradigms, one method will not suit
   all, and so it is expected that vendors will differ in exactly how
   they implement this.

   This document uses the serial number of the device as a unique device
   identifier for simplicity; some vendors may not want to implement the
   system using the serial number as the identifier for business reasons
   (a competitor or similar could enumerate the serial numbers and
   determine how many devices have been manufactured).  Implementors are
   free to choose some other way of generating identifiers (e.g., UUID
   [RFC4122]), but this will likely make it somewhat harder for
   operators to use (the serial number is usually easy to find on a
   device, a more complex system is likely harder to track).

   [ Ed note: This example also uses TFTP because that is what many
   vendors use in their auto-install / ZTP feature.  It could easily
   instead be HTTP, FTP, etc. ]

2.1.  Example Scenario

   Sirius Cybernetics Corp needs another peering router, and so they
   order another router from Acme Network Widgets, to be drop-shipped to
   the Point of Presence (POP) / datacenter.  Acme begins assembling the
   new device, and tells Sirius what the new device's serial number will
   be (SN:17894321).  When Acme first installs the firmware on the
   device and boots it, the device generates a public-private keypair,
   and Acme publishes it the public key on their keyserver (in a public key
   certificate, for ease of use).

   While the device is being shipped, Sirius generates the initial
   device configuration, fetches the certificate from Acme keyservers by
   providing the serial number of the new device.  Sirius then encrypts
   the device configuration and puts this encrypted config on a (local)
   TFTP server.

   When the device arrives at the POP, it gets installed in Sirius'
   rack, and cabled as instructed.  The new device powers up and
   discovers that it has not yet been configured.  It enters its
   autoboot state, and begins the DHCP process.  Sirius' DHCP server
   provides it with an IP address and the address of the configuration
   server.  The router uses TFTP to fetch its config file (note that all
   this is existing functionality).  The device attempts to load the
   config file - if the config file is unparsable, (new functionality)
   the device tries to use its private key to decrypt the file, and,
   assuming it validates, installs the new configuration.

   Only the "correct" device will have the required private key and be
   able to decrypt and use the config file (See Security
   Considerations).  An attacker would be able to connect to the network
   and get an IP address.  They would also be able to retrieve
   (encrypted) config files by guessing serial numbers (or perhaps the
   server would allow directory listing), but without the private keys
   an attacker will not be able to decrypt the files.

3.  Vendor Role / Requirements

   This section describes the vendors roles and responsibilities and
   provides an overview of what the device needs to do.

3.1.  Device key generation

   Each devices requires a public-private key keypair, and for the
   public part to be published and retrievable by the operator.  The
   cryptograthic algorithm and keylenghts key lenghts to be used are out of the
   scope of this document.  This section illustrates one method, but, as
   with much of this document the exact mechanism may will vary by vendor.
   EST [RFC7030]and [I-D.gutmann-scep] is one method are methods which vendors may
   want to
   strongly consider.

   During the manufacturing stage, when the device is initially powered
   on, it will generate a public-private keypair.  It will send its
   unique device identifier and the public key to the vendor's
   Certificate Publication Server to be published.  The vendor's
   Certificate Publication Server should only accept certificates from
   the manufacturing facility, and which match vendor defined policies
   (for example, extended key usage, extensions, etc.)  Note that some
   devices may be constrained, and so may send the raw public key and
   unique device identifier to the certificate publication server, while
   more capable devices may generate and send self-signed certificates.

3.2.  Certificate Publication Server

   The certificate publication server contains a database of
   certificates.  If newly manufactured devices upload certificates the
   certificate publication server can simply publish these, these; if the
   devices provide the raw public keys and unique identifiers device identifier, the
   certificate publication server will need to wrap these in a
   certificate.  Note that the certificate publication server MUST only
   accept certificates or keys from the vendor's manufacturing
   facilities.

   The customers (e.g., Sirius Cybernetics Corp) query this server with
   the serial number (or other provided unique identifier) of a device,
   and retrieve the associated certificate.  It is expected that
   operators will receive the unique device identifier (serial number)
   of devices when they purchase them, and will download and store /
   cache the certificate.  This means that there is not a hard
   requirement on the uptime / reachability of the certificate
   publication server.

                         +------------+
        +------+         |Certificate |
        |Device|         |Publication |
        +------+         |   Server   |
                         +------------+
   +----------------+   +--------------+
   |   +---------+  |   |              |
   |   | Initial |  |   |              |
   |   |  boot?  |  |   |              |
   |   +----+----+  |   |              |
   |        |       |   |              |
   | +------v-----+ |   |              |
   | |  Generate  | |   |              |
   | |Self-signed | |   |              |
   | |Certificate | |   |              |
   | +------------+ |   |              |
   |        |       |   |   +-------+  |
   |        +-------|---|-->|Receive|  |
   |                |   |   +---+---+  |
   |                |   |       |      |
   |                |   |   +---v---+  |
   |                |   |   |Publish|  |
   |                |   |   +-------+  |
   |                |   |              |
   +----------------+   +--------------+

   Initial certificate generation and publication.

4.  Operator Role / Responsibilities

4.1.  Administrative

   When purchasing a new device, the accounting department will need to
   get the unique device identifier (likely serial number) of the new
   device and communicate it to the operations group.

4.2.  Technical

   The operator will contact the vendor's publication server, and
   download the certificate (by providing the unique device identifier
   of the device).  The operator SHOULD fetch the certificate using a
   secure transport (e.g., HTTPS).  The operator will then encrypt the
   initial configuration (for example, using SMIME [RFC5751]) using the
   key in the certificate, and place it on their TFTP server.  See
   Appendix B for examples.

                         +------------+
      +--------+         |Certificate |
      |Operator|         |Publication |
      +--------+         |   Server   |
                         +------------+
   +----------------+  +----------------+
   | +-----------+  |  |  +-----------+ |
   | |   Fetch   |  |  |  |           | |
   | |  Device   |<------>|Certificate| |
   | |Certificate|  |  |  |           | |
   | +-----+-----+  |  |  +-----------+ |
   |       |        |  |                |
   | +-----v------+ |  |                |
   | |  Encrypt   | |  |                |
   | |   Device   | |  |                |
   | |   Config   | |  |                |
   | +-----+------+ |  |                |
   |       |        |  |                |
   | +-----v------+ |  |                |
   | |  Publish   | |  |                |
   | |    TFTP    | |  |                |
   | |   Server   | |  |                |
   | +------------+ |  |                |
   |                |  |                |
   +----------------+  +----------------+

   Fetching the certificate, encrypting the configuration, publishing
   the encrypted configuration.

4.3.  Example Initial Customer Boot

   When the device is first booted by the customer (and on subsequent
   boots), if the device does not have a valid configuration, it will
   use existing auto-install functionality.  As an example, it performs
   DHCP Discovery until it gets a DHCP offer including DHCP option 66
   (Server-Name) or 150 (TFTP server address), contact contacts the server
   listed in these DHCP options and downloads its config file.  Note
   that this is existing functionality (for example, Cisco devices fetch
   the config file named by the Bootfile-Name DHCP option (67)).

   After retrieving the config file, the device needs to determine if it
   is encrypted or not.  If it is not encrypted, the existing behavior
   is used.  If the configuration is encrypted, the process continues as
   described in this document.  The method used to determine if the
   config is encrypted or not is implementation dependant; there are a
   number of (obvious) options, including having a magic string in the
   file header, using a file name extension (e.g., config.enc), or using
   specific DHCP options.

   If the file is encrypted, the device will attempt to decrypt and
   parse the file.  It  If able, it will install the configuration, and
   start using it.  If this it cannot decrypt the file, or if parsing the
   configurations fails, the device with will either abort the auto-install
   process, or will repeat this process until it succeeds.

   Note that the device only needs to be able to download the config
   file; after the initial power-on in the factory it never needs to
   access the Internet or vendor or certificate publication server - it
   (and only it) has the private key and so has the ability to decrypt
   the config file.

             +--------+                +--------------+
             | Device |                |Config server |
             +--------+                | (e.g. TFTP)  |
                                       +--------------+
   +---------------------------+    +------------------+
   | +-----------+             |    |                  |
   | |           |             |    |                  |
   | |   DHCP    |             |    |                  |
   | |           |             |    |                  |
   | +-----+-----+             |    |                  |
   |       |                   |    |                  |
   | +-----v------+            |    |  +-----------+   |
   | |            |            |    |  | Encrypted |   |
   | |Fetch config|<------------------>|  config   |   |
   | |            |            |    |  |   file    |   |
   | +-----+------+            |    |  +-----------+   |
   |       |                   |    |                  |
   |       X                   |    |                  |
   |      / \                  |    |                  |
   |     /   \ N    +--------+ |    |                  |
   |    | Enc?|---->|Install,| |    |                  |
   |     \   /      |  Boot  | |    |                  |
   |      \ /       +--------+ |    |                  |
   |       V                   |    |                  |
   |       |Y                  |    |                  |
   |       |                   |    |                  |
   | +-----v------+            |    |                  |
   | |Decrypt with|            |    |                  |
   | |private key |            |    |                  |
   | +-----+------+            |    |                  |
   |       |                   |    |                  |
   |       v                   |    |                  |
   |      / \                  |    |                  |
   |     /   \ Y    +--------+ |    |                  |
   |    |Sane?|---->|Install,| |    |                  |
   |     \   /      |  Boot  | |    |                  |
   |      \ /       +--------+ |    |                  |
   |       V                   |    |                  |
   |       |N                  |    |                  |
   |       |                   |    |                  |
   |  +----v---+               |    |                  |
   |  |Give up | up,|               |    |                  |
   |  |go home |               |    |                  |
   |  +--------+               |    |                  |
   |                           |    |                  |
   +---------------------------+    +------------------+

   Device boot, fetch and install config file

5.  Additional Considerations

5.1.  Key storage

   Ideally, the keypair would be stored in a Trusted Platform Module
   (TPM) on something which is identified as the "router" - for example,
   the chassis / backplane.  This is so that a keypair is bound to what
   humans think of as the "device", and not, for example (redundant)
   routing engines.  Devices which implement IEEE 802.1AR [IEEE802-1AR]
   could choose to use the IDevID for this purpose.

5.2.  Key replacement

   It is anticipated that some operator may want to replace the (vendor
   provided) keys after installing the device.  There are two options
   when implementing this - a vendor could allow the operator's key to
   completely replace the initial device generated key (which means
   that, if the device is ever sold, the new owner couldn't use this
   technique to install the device), or the device could prefer the
   operators installed key.  This is an implementation decision left to
   the vendor.

5.3.  Device reinstall

   Increasingly, operations is moving towards an automated model of
   device management, whereby portions (or the entire) configuration is
   programmatically generated.  This means that operators may want to
   generate an entire configuration after the device has been initially
   installed and ask the device to load and use this new configuration.
   It is expected (but not defined in this document, as it is vendor
   specific) that vendors will allow the operator to copy a new,
   encrypted config (or part of a config) onto a device and then request
   that the device decrypt and install it (e.g.: 'load replace
   <filename> encrypted)).  The operator could also choose to reset the
   device to factory defaults, and allow the device to act as though it
   were the initial boot (see Section 4.3).

6.  IANA Considerations

   This document makes no requests of the IANA.

7.  Security Considerations

   This mechanism is intended to replace either expensive (traveling
   employees) or insecure mechanisms of installing newly deployed
   devices such as: unencrypted config files which can be downloaded by
   connecting to unprotected ports in datacenters, mailing initial
   config files on flash drives, or emailing config files and asking a
   third-party to copy and paste it over a serial terminal.  It does not
   protect against devices with malicious firmware, nor theft and reuse
   of devices.

   An attacker (e.g., a malicious datacenter employee) who has physical
   access to the device before it is connected to the network the
   attacker may be able to extract the device private key (especially if
   it isn't is not stored in a TPM), pretend to be the device when connecting
   to the network, and download and extract the (encrypted) config file.

   This mechanism does not protect against a malicious vendor - while
   the keypair should be generated on the device, and the private key
   should be securely stored, the mechanism cannot detect or protect
   against a vendor who claims to do this, but instead generates the
   keypair off device and keeps a copy of the private key.  It is
   largely understood in the operator community that a malicious vendor
   or attacker with physical access to the device is largely a "Game
   Over" situation.

   Even when using a secure bootstrapping mechanism, security conscious
   operators may wish to bootstrapping devices with a minimal / less
   sensitive config, and then replace this with a more complete one
   after install.

8.  Acknowledgments

   The authors wish to thank everyone who contributed, including Benoit
   Claise, Francis Dupont, Sam Ribeiro, Michael Richardson, Sean Turner
   and Kent Watsen.  Joe Clarke also provided significant comments and
   review, and Tom Petch provided significant editorial contributions to
   better describe the use cases, and clarify the scope.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2.  Informative References

   [I-D.gutmann-scep]
              Gutmann, P., "Simple Certificate Enrolment Protocol",
              draft-gutmann-scep-16 (work in progress), March 2020.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
              and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-40
              keyinfra-41 (work in progress), April 2020.

   [I-D.ietf-opsawg-tacacs]
              Dahm, T., Ota, A., dcmgash@cisco.com, d., Carrel, D., and
              L. Grant, "The TACACS+ Protocol", draft-ietf-opsawg-
              tacacs-18 (work in progress), March 2020.

   [IEEE802-1AR]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks - Secure Device Identity", June 2018,
              <https://standards.ieee.org/standard/802_1AR-2018.html>.

   [RFC1350]  Sollins, K., "The TFTP Protocol (Revision 2)", STD 33,
              RFC 1350, DOI 10.17487/RFC1350, July 1992,
              <https://www.rfc-editor.org/info/rfc1350>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <https://www.rfc-editor.org/info/rfc2131>.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,
              <https://www.rfc-editor.org/info/rfc2865>.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,
              <https://www.rfc-editor.org/info/rfc4122>.

   [RFC5751]  Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
              Mail Extensions (S/MIME) Version 3.2 Message
              Specification", RFC 5751, DOI 10.17487/RFC5751, January
              2010, <https://www.rfc-editor.org/info/rfc5751>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/info/rfc7030>.

   [RFC8572]  Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero
              Touch Provisioning (SZTP)", RFC 8572,
              DOI 10.17487/RFC8572, April 2019,
              <https://www.rfc-editor.org/info/rfc8572>.

Appendix A.  Changes / Author Notes.

   [RFC Editor: Please remove this section before publication ]

   From -03 to -04

   o  Addressed Joe's WGLC comments.  This involved changing the "just
      try decrypt and pray" to vendor specific, like a file extension,
      magic header sting, etc.

   o  Addressed tom's comments.

   From individual WG-01 to -03:

   o  Addressed Joe Clarke's comments -
      https://mailarchive.ietf.org/arch/msg/opsawg/JTzsdVXw-
      XtWXZIIFhH7aW_-0YY

   o  Many typos / nits

   o  Broke Overview and Example Scenario into 2 sections.

   o  Reordered text for above.

   From individual -04 to WG-01:

   o  Renamed from draft-wkumari-opsawg-sdi-04 -> draft-ietf-opsawg-
      sdi-00

   From -00 to -01

   o  Nothing changed in the template!

   From -01 to -03:

   o  See github commit log (AKA, we forgot to update this!)

   o  Added Colin Doyle.

   From -03 to -04:

   Addressed a number of comments received before / at IETF104 (Prague).
   These include:

   o  Pointer to https://datatracker.ietf.org/doc/draft-ietf-netconf-
      zerotouch -- included reference to (now) RFC8572 (KW)

   o  Suggested that 802.1AR IDevID (or similar) could be used.  Stress
      that this is designed for simplicity (MR)

   o  Added text to explain that any unique device identifier can be
      used, not just serial number - serial number is simple and easy,
      but anything which is unique (and can be communicated to the
      customer) will work (BF).

   o  Lots of clarifications from Joe Clarke.

   o  Make it clear it should first try use the config, and if it
      doesn't work, then try decrypt and use it.

   o  The CA part was confusing people - the certificate is simply a
      wrapper for the key, and the Subject just an index, and so removed
      that.

   o  Added a bunch of ASCII diagrams

Appendix B.  Demo / proof of concept

   This section contains a rough demo / proof of concept of the system.
   It is only intended for illustration, and is not intended to be used
   in production.

   It uses OpenSSL from the command line, in production something more
   automated would be used.  In this example, the unique device
   identifier is the serial number of the router, SN19842256.

B.1.  Step 1: Generating the certificate.

   This step is performed by the router.  It generates a key, then a
   csr, and then a self signed certificate.

B.1.1.  Step 1.1: Generate the private key.

   $ openssl genrsa -out key.pem 2048
   Generating RSA private key, 2048 bit long modulus
   .................................................
   .................................................
   ..........................+++
   ...................+++
   e is 65537 (0x10001)

B.1.2.  Step 1.2: Generate the certificate signing request.

   $ openssl req -new -key key.pem -out SN19842256.csr
   Country Name (2 letter code) [AU]:.
   State or Province Name (full name) [Some-State]:.
   Locality Name (eg, city) []:.
   Organization Name (eg, company) [Internet Widgits Pty Ltd]:.
   Organizational Unit Name (eg, section) []:.
   Common Name (e.g. server FQDN or YOUR name) []:SN19842256
   Email Address []:.

   Please enter the following 'extra' attributes
   to be sent with your certificate request
   A challenge password []:
   An optional company name []:.

B.1.3.  Step 1.3: Generate the (self signed) certificate itself.

   $ openssl req -x509 -days 36500 -key key.pem -in SN19842256.csr -out
   SN19842256.crt

   The router then sends the key to the vendor's keyserver for
   publication (not shown).

B.2.  Step 2: Generating the encrypted config.

   The operator now wants to deploy the new router.

   They generate the initial config (using whatever magic tool generates
   router configs!), fetch the router's certificate and encrypt the
   config file to that key.  This is done by the operator.

B.2.1.  Step 2.1: Fetch the certificate.

   $ wget http://keyserv.example.net/certificates/SN19842256.crt

B.2.2.  Step 2.2: Encrypt the config file.

   I'm using S/MIME because it is simple to demonstrate.  This is almost
   definitely not the best way to do this.

   $ openssl smime -encrypt -aes-256-cbc -in SN19842256.cfg\
     -out SN19842256.enc -outform PEM SN19842256.crt
   $ more SN19842256.enc
   -----BEGIN PKCS7-----
   MIICigYJKoZIhvcNAQcDoIICezCCAncCAQAxggE+MIIBOgIBADAiMBUxEzARBgNV
   BAMMClNOMTk4NDIyNTYCCQDJVuBlaTOb1DANBgkqhkiG9w0BAQEFAASCAQBABvM3
   ...
   LZoq08jqlWhZZWhTKs4XPGHUdmnZRYIP8KXyEtHt
   -----END PKCS7-----

B.2.3.  Step 2.3: Copy config to the config server.

   $ scp SN19842256.enc config.example.com:/tftpboot

B.3.  Step 3: Decrypting and using the config.

   When the router connects to the operator's network it will detect
   that does not have a valid configuration file, and will start the
   "autoboot" process.  This is a well documented process, but the high
   level overview is that it will use DHCP to obtain an IP address and
   config server.  It will then use TFTP to download a configuration
   file, based upon its serial number (this document modifies the
   solution to fetch an encrypted config file (ending in .enc)).  It
   will then decrypt the config file, and install it.

B.3.1.  Step 3.1: Fetch encrypted config file from config server.

   $ tftp 2001:0db8::23 -c get SN19842256.enc

B.3.2.  Step 3.2: Decrypt and use the config.

   $ openssl smime -decrypt -in SN19842256.enc -inform pkcs7\
     -out config.cfg -inkey key.pem

   If an attacker does not have the correct key, they will not be able
   to decrypt the config:

   $ openssl smime -decrypt -in SN19842256.enc -inform pkcs7\
     -out config.cfg -inkey wrongkey.pem
   Error decrypting PKCS#7 structure
   140352450692760:error:06065064:digital envelope
    routines:EVP_DecryptFinal_ex:bad decrypt:evp_enc.c:592:
   $ echo $?
   4

Authors' Addresses

   Warren Kumari
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA  94043
   US

   Email: warren@kumari.net

   Colin Doyle
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, CA  94089
   US

   Email: cdoyle@juniper.net