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Secure Device Install
draft-wkumari-opsawg-sdi-02

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Author Warren "Ace" Kumari
Last updated 2018-07-16
Replaced by draft-ietf-opsawg-sdi, RFC 8886
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draft-wkumari-opsawg-sdi-02
Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Informational                             July 16, 2018
Expires: January 17, 2019

                         Secure Device Install
                      draft-wkumari-opsawg-sdi-02

Abstract

   Deploying a new network device often requires that an employee
   physically travel to a datacenter 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
   standard, secure way to initially provision the devices.

   This document extends existing auto-install / Zero-Touch Provisioning
   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 ]

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 https://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 17, 2019.

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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  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.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  Overview / Example Scenario . . . . . . . . . . . . . . . . .   4
   3.  Vendor Role / Requirements  . . . . . . . . . . . . . . . . .   4
     3.1.  CA Infrastructure . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Certificate Publication Server  . . . . . . . . . . . . .   5
     3.3.  Initial Device Boot . . . . . . . . . . . . . . . . . . .   5
     3.4.  Subsequent Boots  . . . . . . . . . . . . . . . . . . . .   5
   4.  Operator Role / Responsibilities  . . . . . . . . . . . . . .   6
     4.1.  Administrative  . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Technical . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Future enhancements / Discussion  . . . . . . . . . . . . . .   6
     5.1.  Key storage . . . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  Key replacement . . . . . . . . . . . . . . . . . . . . .   6
     5.3.  Device reinstall  . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Changes / Author Notes.  . . . . . . . . . . . . . .   8
   Appendix B.  Demo / proof of concept  . . . . . . . . . . . . . .   8
     B.1.  Step 1: Generating the certificate. . . . . . . . . . . .   8
       B.1.1.  Step 1.1: Generate the private key. . . . . . . . . .   8
       B.1.2.  Step 1.2: Generate the certificate signing request. .   8
       B.1.3.  Step 1.3: Generate the (self signed) certificate
               itself. . . . . . . . . . . . . . . . . . . . . . . .   9
     B.2.  Step 2: Generating the encrypted config.  . . . . . . . .   9
       B.2.1.  Step 2.1: Fetch the certificate.  . . . . . . . . . .   9
       B.2.2.  Step 2.2: Encrypt the config file.  . . . . . . . . .   9

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       B.2.3.  Step 2.3: Copy config to the config server. . . . . .  10
     B.3.  Step 3: Decrypting and using the config.  . . . . . . . .  10
       B.3.1.  Step 3.1: Fetch encrypted config file from config
               server. . . . . . . . . . . . . . . . . . . . . . . .  10
       B.3.2.  Step 3.2: Decrypt and use the config. . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   In a growing, global network, significant amounts of time and money
   are spent simply 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 to get an IP address and
   configuration server, and then fetch and install a configuration when
   they are first powered on.

   Network device configurations contain a significant amount of
   security related and / or proprietary information (for example,
   RADIUS or TACACS secrets).  Exposing these to a third party to load
   onto a new device (or using an auto-install techniques which fetch an
   (unencrypted) config file via something like TFTP) is simply not
   acceptable to many operators, and so they have to send employees to
   remote locations to perform the initial configuration work.  As well
   as having a significant monetary cost, it also takes significantly
   longer to install devices and is generally inefficient.

   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.

1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

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2.  Overview / Example Scenario

   Sirius Cybernetics Corp needs another peering router, and so they
   order another router from Acme Network Widgets, to be drop-shipped to
   a POP.  Acme begins assembling the new device, and tells Sirius what
   the new device's serial number will be (SN:17894321).  During the
   initial boot / testing, the router generates a public-private
   keypair, and publishes the public part to Acme's keyserver (in a
   certificate, for ease of use).

   While Acme is shipping the new device, Sirius begins generating the
   initial device configuration.  Once the config is ready, Sirius
   contacts the Acme keyserver, provides the serial number of the new
   device and fetches the device's public key.  Sirius then encrypts the
   device configuration and puts this encrypted config on a (local) TFTP
   server.

   When the POP receives the new device, they install it in Sirius'
   rack, and connect the cables as instructed.  The new device powers up
   and discovers that it has not yet been configured.  It enters its
   autoboot state, and begins DHCPing.  Sirius' DHCP server provides it
   with an IP address and the address of the configuration server.  The
   router uses TFTP to fetch a file named according to its serial number
   (acme_17894321.cfg).  It then uses its private key to decrypt this
   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.

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

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.  CA Infrastructure

   The vendor needs to run some (simple) CA infrastructure to sign and
   publish certificates.  When a device is initially powered on (in the
   factory) it will generate a public / private keypair and a

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   Certificate Signing Request (CSR), with the commonName being the
   Serial Number of the device.  The device sends this CSR to the CA,
   which signs the CSR, returns the certificate to the device and also
   sends it to a certificate publication server.

3.2.  Certificate Publication Server

   The certificate publication server contains a database of all signed
   certificates.  Customers (e.g Sirius Cybernetics Corp) query this
   server with a serial number, and retrieve the associated certificate.
   It is expected that operators will receive the serial numbers of
   newly purchased devices when they purchase them, and that some
   automated system 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.

   [ Ed: The vendor may not want to expose (for commercial reasons) how
   many devices it has made.  This can be mitigated by using non-
   contiguous serial numbers, and simply creating "fake devices", etc. ]

3.3.  Initial Device Boot

   When the device is powered on for the very first time, it will
   generate its keypair.  It then generates a CSR (including the device
   serial number) and sends it to the vendor's CA, which signs the
   certificate.  The device receives the signed certificate and stores
   it.

3.4.  Subsequent Boots

   After the initial boot, it the device has no (valid) configuration
   file, it will perform standard an auto-install type functionality.
   For example, it will perform DHCP Discovery until it gets a DHCP
   offer including DHCP option 66 or 150.  It will contact the server
   listed in these DHCP options and download a configuration file named
   config_<serial_number>.cfg.  This is all existing (often vendor
   proprietary) functionality.

   After retrieving the config file, Secure Device Install devices will
   attempt to decrypt the configuration file using its private key.  If
   it is able to decrypt and validate the file it will install the
   configuration, and start using it.

   [ Ed note: SDI will also allows additional functionality, like always
   storing the configs encrypted, having the device store its config
   encrypted in flash (so that e.g RMAing a routing engine will not leak
   config, etc.  I'm not describing this in detail because:

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   1.  I want to keep this document simple and focused and, more
       importantly

   2.  I left converting this into ID format until the draft cuff-off
       and have run out of time :-) ]

4.  Operator Role / Responsibilities

4.1.  Administrative

   When purchasing a new device, the accounting department will need to
   get the 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 serial number of the
   device).  They will then encrypt the initial configuration to that
   key, and place it on the TFTP server, named config_<SN>.enc.  See
   Appendix B for examples.

5.  Future enhancements / Discussion

   [ Ed note: Ed / RFC Editor to remove this section before publication.
   ]

5.1.  Key storage

   Currently most network devices will store the private key in NV
   storage (NVRAM / Flash / Disk), but some vendors are already planning
   on including a TPM module in their devices.  Ideally, the keypair
   would be stored in a 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.

5.2.  Key replacement

   It is anticipated that some operator may want to replace the (vendor
   provided) keys after installing the device.  This would remove (some)
   concerns that the vendor may have kept a copy of the private key, or
   that the device may have been intercepted during shipping and the
   private key duplicated.  This would also allow for the use of
   certificates signed by the operator's CA (e.g using RFC7030 -
   Enrollment over Secure Transport) this is a trivial operation, but is
   not described here (to avoid cluttering up the doc).

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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 too vendor
   specific) that vendors will allow the operator to e.g scp 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)).

6.  IANA Considerations

   This document contains no IANA considerations.Template: Fill this in!

7.  Security Considerations

   This needs to be completed, including:

   1.  We are trusting the vendor to have not kept a copy of the private
       key when the device initially generated its keypair.
       Unfortunately you are already trusting the vendor in many ways -
       it could have included a backdoor in it's code, etc.

   2.  Devices should be storing their keying information in something
       like a TPM, to help mitigate the private key being extracted (e.g
       read off disk) in shipping, when the device is first unpacked by
       smart-hands, etc).  A number of vendors are already discussing
       including TPM for other security functions.

8.  Acknowledgements

   The authors wish to thank some folk, including Benoit Claise and Sam
   Ribeiro.

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>.

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9.2.  Informative References

   [I-D.ietf-sidr-iana-objects]
              Manderson, T., Vegoda, L., and S. Kent, "RPKI Objects
              issued by IANA", draft-ietf-sidr-iana-objects-03 (work in
              progress), May 2011.

Appendix A.  Changes / Author Notes.

   [RFC Editor: Please remove this section before publication ]

   From -00 to -01

   o  Nothing changed in the template!

Appendix B.  Demo / proof of concept

   This section contains a rough demo / proof of concept of the system.
   It is only intended for illustration; presumably things like
   algorithms, key lengths, format / containers will provide much fodder
   for discussion.

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

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   $ 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.

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   $ 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 then decrypt the config file, and install it.

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

   $ tftp 192.0.2.1 -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

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Author's Address

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

   Email: warren@kumari.net

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