Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Informational                                  C. Doyle
Expires: November 21, December 10, 2020                              Juniper Networks
                                                            May 20,
                                                           June 08, 2020

                         Secure Device Install
                        draft-ietf-opsawg-sdi-11
                        draft-ietf-opsawg-sdi-12

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 facilities with "remote-hands" type support.  In many
   cases, this could be avoided if there were a secure an easy way to initially
   provision transfer
   the device. initial configuration to a new device, while still maintaining
   confidentiality of the configuration.

   This document extends existing vendor proprietary auto-install to
   make
   provide confidentiality to initial configuration during bootstrapping
   of the process more secure. device.

   [ 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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   This Internet-Draft will expire on November 21, December 10, 2020.

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   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Example Scenario  . . . . . . . . . . . . . . . . . . . .   5
   3.  Vendor Role . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Device key generation . . . . . . . . . . . . . . . . . .   6
     3.2.  Certificate Publication  Directory Server  . . . . . . . . . . . . .   6 . . . . . . .   7
   4.  Operator Role . . . . . . . . . . . . . . . . . . . . . . . .   7   8
     4.1.  Administrative  . . . . . . . . . . . . . . . . . . . . .   7   8
     4.2.  Technical . . . . . . . . . . . . . . . . . . . . . . . .   7   8
     4.3.  Example Initial Customer Boot . . . . . . . . . . . . . .   8   9
   5.  Additional Considerations . . . . . . . . . . . . . . . . . .  11  12
     5.1.  Key storage . . . . . . . . . . . . . . . . . . . . . . .  11  12
     5.2.  Key replacement . . . . . . . . . . . . . . . . . . . . .  11  12
     5.3.  Device reinstall  . . . . . . . . . . . . . . . . . . . .  11  12
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11  12
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12  13
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  13  14
   Appendix A.  Changes / Author Notes.  . . . . . . . . . . . . . .  14  15
   Appendix B.  Proof of Concept . . . . . . . . . . . . . . . . . .  16  17
     B.1.  Step 1: Generating the certificate. . . . . . . . . . . .  16  17
       B.1.1.  Step 1.1: Generate the private key. . . . . . . . . .  16  17
       B.1.2.  Step 1.2: Generate the certificate signing request. .  16  17
       B.1.3.  Step 1.3: Generate the (self signed) certificate
               itself. . . . . . . . . . . . . . . . . . . . . . . .  17
     B.2.  Step 2: Generating the encrypted configuration. . . . . .  17  18
       B.2.1.  Step 2.1: Fetch the certificate.  . . . . . . . . . .  17  18
       B.2.2.  Step 2.2: Encrypt the configuration file. . . . . . .  17  18
       B.2.3.  Step 2.3: Copy configuration to the configuration
               server. . . . . . . . . . . . . . . . . . . . . . . .  17  18
     B.3.  Step 3: Decrypting and using the configuration. . . . . .  17  18
       B.3.1.  Step 3.1: Fetch encrypted configuration file from
               configuration server. . . . . . . . . . . . . . . . .  18  19
       B.3.2.  Step 3.2: Decrypt and use the configuration.  . . . .  18  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18  19

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 facilities (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
   proprietary) protocols to perform initial device installs and
   configurations.  For example, many network devices will attempt to
   use DHCP [RFC2131] or DHCPv6 [RFC8415] 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 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 technique which fetches an unencrypted configuration 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 device before shipping it; asking the remote support to
   install a terminal server; providing a minimal, unsecured
   configuration and using that to bootstrap to a complete
   configuration, etc.  However, these are often clumsy and have
   security issues.  As an example, in the terminal server case, the
   console port connection could be easily snooped.

   An ideal solution in this space would protect both the
   confidentiality of device configuration in transit and the
   authenticity (and authorization status) of configuration to be used
   by the device.  The mechanism described in this document only
   addresses the former, and makes no effort to do the latter, with the
   device accepting any configuration file that comes its way and is
   encrypted to the device's key (or not encrypted, as the case may be).
   Other solutions (such as "Secure Zero Touch Provisioning (SZTP)"
   [RFC8572], [I-D.ietf-anima-bootstrapping-keyinfra] and other voucher-
   based methods) are more fully featured, but also require more
   complicated machinery.  This document describes something much
   simpler, at the cost of only providing limited protection.

   This document layers security onto existing auto-install solutions
   (one example of which is [Cisco_AutoInstall]) to provide a secure method to
   initially configure new devices. devices while maintaining confidentiality of
   the initial configuration.  It is optimized for simplicity, for both
   the implementor and the operator; it is explicitly not intended to be
   a fully featured system for managing installed 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 and there is no
   trusted member of the operator's staff to perform the initial
   configuration.  This solution is only intended to increase
   confidentiality of the information in the configuration file, and
   does not to protect the device itself.

   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 are not widely
   deployed yet.  In addition, work in the IETF "Software Updates for
   Internet of Things (suit)" WG is expected to provide mechanisms for
   firmware updates, and are out of scope for this document. itself from loading a malicious
   configuration.

   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 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.

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 for itself and discover the address of a
   configuration server (often called 'next-server', 'siaddr' or 'tftp-
   server-name') using DHCP or DHXPv6 (see [RFC2131]). [RFC2131], [RFC8415]).  The
   device then contacts this configuration server to download its
   initial configuration, which is often identified using the device's
   serial number, MAC address or similar.  This document extends this
   (vendor-specific) paradigm by allowing the configuration file to be
   encrypted.

   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).
   device).

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

2.1.  Example Scenario

   Operator_A needs another peering router, and so they order another
   router from Vendor_B, to be drop-shipped to the facility.  Vendor_B
   begins assembling the new device, and tells Operator_A what the new
   device's serial number will be (SN:17894321).  When Vendor_B first
   installs the firmware on the device and boots it, the device
   generates a public-private key pair, and Vendor_B publishes the
   public key on their keyserver (in a public key certificate, for ease
   of use).

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

   When the device arrives at the POP, it gets installed in Operator_A's
   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.  Operator_A's DHCP
   server provides it with an IP address and the address of the
   configuration server.  The router uses TFTP to fetch its
   configuration file.  Note that all of this is existing functionality.
   The device attempts to load the configuration file.  As an added
   step, if the configuration file cannot be parsed, the device tries to
   use its private key to decrypt the file and, assuming it validates,
   proceeds to install the new, decrypted, configuration.

   Only the "correct" device will have the required private key and be
   able to decrypt and use the configuration file (See Security
   Considerations (Section 7)).  An attacker would be able to connect to
   the network and get an IP address.  They would also be able to
   retrieve (encrypted) configuration 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

   This section describes the vendor's roles and provides an overview of
   what the device needs to do.

3.1.  Device key generation

   Each device requires a public-private key pair, and for the public
   part to be published and retrievable by the operator.  The
   cryptographic algorithm and key lengths 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 vary by vendor.
   Enrollment over Secure Transport ([RFC7030]) and or possibly
   [I-D.gutmann-scep] are methods which vendors may want to consider.

   During the manufacturing stage, when the device is initially powered
   on, it will generate a public-private key pair.  It will send its
   unique device identifier and the public key to the vendor's
   Certificate Publication Server directory
   server to be published.  The vendor's
   Certificate Publication Server directory server should only
   accept certificates from the manufacturing facility, and which match
   vendor defined policies (for example, extended key usage, and
   extensions) 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.  This communication with
   the directory server should be integrity protected, and in a
   controlled environment.

   This reference architecture needs a serialization format for the key
   material.  Due to the prevalence of tooling support for it on network
   devices, X.509 certificates are a convenient format to exchange
   public keys.  However, most of the meta-data that would use for
   revocation and aging will not be used and should be ignored by both
   the client and server.  In such cases the signature on the
   certificate conveys no value and the consumer of the certificate is
   expected to pin the end-entity key fingerprint (versus using a PKI
   and signature chain).

3.2.  Certificate Publication  Directory Server

   The certificate publication directory server contains a database of certificates.  If newly
   manufactured devices upload certificates the
   certificate publication directory server can
   simply publish these; if the devices provide the raw public keys and
   unique device identifier, the
   certificate publication directory server will need to wrap
   these in a certificate.

   The customers (e.g., Operator_A) 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 the certificate.
   This means that there is not a hard requirement on the reachability
   of the certificate publication directory server.

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

   Initial certificate generation and publication.

4.  Operator Role

4.1.  Administrative

   When purchasing a new device, the accounting department will need to
   get the unique device identifier (e.g., 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 fetches the certificate using a secure
   transport (e.g., HTTPS). that authenticates the source of the certificate, such as
   HTTPS (confidentiality protection can provide some privacy and
   metadata-leakage benefit, but is not key to the primary mechanism of
   this document).  The operator will then encrypt the initial
   configuration (for example, using SMIME [RFC5751]) using the key in
   the certificate, and place it on their configuration server.

   See Appendix B for examples.

                         +------------+
      +--------+         |Certificate         |           |
      |Operator|         |Publication         | Directory |
      +--------+         |   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), contacts the server
   listed in these DHCP options and downloads its configuration 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 configuration 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 configuration is encrypted or not is implementation
   dependent; 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.  If able, it will install the configuration, and
   start using it.  If it cannot decrypt the file, or if parsing the
   configuration fails, the device will either abort the auto-install
   process, or repeat this process until it succeeds.  When retrying,
   care should be taken to not overwhelm the server hosting the
   encrypted configuration files.  It is suggested that the device retry
   every 5 minutes for the first hour, and then every hour after that.
   As it is expected that devices may be installed well before the
   configuration file is ready, a maximum number of retries is not
   specified.

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

   Device boot, fetch and install configuration file

5.  Additional Considerations

5.1.  Key storage

   Ideally, the key pair 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 key pair 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
   operator's 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 of (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 configuration (or part of a configuration) 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 reference architecture is intended to incrementally improve upon
   commonly accepted "auto-install" practices used today that may
   transmit configurations unencrypted (e.g., unencrypted configuration
   files which can be downloaded connecting to unprotected ports in
   datacenters, mailing initial configuration files on flash drives, or
   emailing configuration files and asking a third-party to copy and
   paste them over a serial terminal) or allow unrestricted access to
   these configurations.

   This document describes an object level security design to provide
   confidentiality assurances for the configuration while it is in
   transit between the configuration server and the unprovisioned device
   even if the underly transport does not provide this security service.

   The architecture provides no assurances about the source of the
   encrypted configuration or protect against theft and reuse of
   devices.

   An attacker (e.g., a malicious datacenter employee, person in the
   supply chain, etc.) who has physical access to the device before it
   is connected to the network network, or who manages to exploit it once
   installed, may be able to extract the device private key (especially
   if it is not stored in a TPM), pretend to be the device when
   connecting to the network, and download and extract the (encrypted)
   configuration file.

   An attacker with access to the configuration server (or the ability
   to route traffic to configuration server under their control) and the
   device's public key could return a configuration of the attacker's
   choosing to the unprovisioned device.

   This mechanism does not protect against a malicious vendor.  While
   the key pair 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 key
   pair 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 bootstrap mechanism, security-conscious
   operators may wish to bootstrap devices with a minimal or less-
   sensitive configuration, 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, Mirja Kuehlewind, 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.

   Roman Danyliw and Benjamin Kaduk also provided helpful text text,
   especially around the certificate
   usage. usage and security considerations.

9.  Informative References

   [Cisco_AutoInstall]
              Cisco Systems, Inc., "Using AutoInstall to Remotely
              Configure Cisco Networking Devices", Jan 2018,
              <https://www.cisco.com/c/en/us/td/docs/ios-
              xml/ios/fundamentals/configuration/15mt/fundamentals-15-
              mt-book/cf-autoinstall.html>.

   [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-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>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

   [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 -09 to -10

   o  Typos - "lenghts" => "lengths", missed a reference to Acme.

   From -08 to -09

   o  Addressed Mirja's IETF LC comments.

   From -04 to -08

   o  Please see GitHub commit log (I forgot to put them in here :-P )

   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.  Proof of Concept

   This section contains a 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
   Certificate Signing Request (CSR), and then a self signed
   certificate.

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

       $ openssl genrsa ecparam -out key.pem 2048
   Generating RSA private key, 2048 bit long modulus
   .................................................
   .................................................
   ..........................+++
   ...................+++
   e is 65537 (0x10001) privatekey.key -name prime256v1 -genkey
       $

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 configuration.

   The operator now wants to deploy the new router.

   They generate the initial configuration (using whatever magic tool
   generates router configs!), fetch the router's certificate and
   encrypt the configuration 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 configuration file.

   S/MIME is used here 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 configuration to the configuration server.

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

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

   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
   configuration 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 configuration file
   (ending in .enc)).  It will then decrypt the configuration file, and
   install it.

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

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

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

   $ 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 configuration file:

   $ 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