Internet DRAFT - draft-ietf-sidr-rtr-keying
draft-ietf-sidr-rtr-keying
Network Working Group R. Bush
Internet-Draft IIJ Lab / Dragon Research Lab
Intended status: Standards Track S. Turner
Expires: March 3, 2019 sn3rd
K. Patel
Arrcus, Inc.
August 30, 2018
Router Keying for BGPsec
draft-ietf-sidr-rtr-keying-16
Abstract
BGPsec-speaking routers are provisioned with private keys in order to
sign BGPsec announcements. The corresponding public keys are
published in the global Resource Public Key Infrastructure, enabling
verification of BGPsec messages. This document describes two methods
of generating the public-private key-pairs: router-driven and
operator-driven.
Requirements Language
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 16, 2017.
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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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Management / Router Communication . . . . . . . . . . . . . . 3
3. Exchange Certificates . . . . . . . . . . . . . . . . . . . . 4
4. Set-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Generate PKCS#10 . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Router-Generated Keys . . . . . . . . . . . . . . . . . . 5
5.2. Operator-Generated Keys . . . . . . . . . . . . . . . . . 5
5.2.1. Using PKCS#8 to Transfer Private Key . . . . . . . . . 5
6. Send PKCS#10 and Receive PKCS#7 . . . . . . . . . . . . . . . 6
7. Install Certificate . . . . . . . . . . . . . . . . . . . . . 6
8. Advanced Deployment Scenarios . . . . . . . . . . . . . . . . 7
9. Key Management . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Key Validity . . . . . . . . . . . . . . . . . . . . . . . 8
9.2. Key Roll-Over . . . . . . . . . . . . . . . . . . . . . . 9
9.3. Key Revocation . . . . . . . . . . . . . . . . . . . . . . 9
9.4. Router Replacement . . . . . . . . . . . . . . . . . . . . 10
10. Security Considerations . . . . . . . . . . . . . . . . . . . 10
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
12.1. Normative References . . . . . . . . . . . . . . . . . . 12
12.1. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Management/Router Channel Security . . . . . . . . . 15
Appendix B. The n00b Guide to BGPsec Key Management . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
BGPsec-speaking routers are provisioned with private keys, which
allow them to digitally sign BGPsec announcements. To verify the
signature, the public key, in the form of a certificate [RFC8209], is
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published in the Resource Public Key Infrastructure (RPKI). This
document describes provisioning of BGPsec-speaking routers with the
appropriate public-private key-pairs. There are two sub-methods,
router-driven and operator-driven.
These two sub-methods differ in where the keys are generated: on the
router in the router-driven method, and elsewhere in the operator-
driven method. Routers are required to support at least one of the
methods in order to work in various deployment environments. Some
routers may not allow the private key to be off-loaded while others
may. While off-loading private keys would ease swapping of routing
engines, exposure of private keys is a well known security risk.
In the operator-driven method, the operator generates the private/
public key-pair and sends it to the router.
In the router-driven method, the router generates its own public/
private key-pair.
The router-driven model mirrors the model used by traditional PKI
subscribers; the private key never leaves trusted storage (e.g.,
Hardware Security Module). This is by design and supports classic
PKI Certification Policies for (often human) subscribers which
require the private key only ever be controlled by the subscriber to
ensure that no one can impersonate the subscriber. For non-humans,
this model does not always work. For example, when an operator wants
to support hot-swappable routers the same private key needs to be
installed in the soon-to-be online router that was used by the the
soon-to-be offline router. This motivated the operator-driven model.
The remainder of this document describes how operators can use the
two methods to provision new and existing routers. The methods
described involve the operator configuring the two end points (i.e.,
the management station and the router) and acting as the
intermediary. Section 7 describes a method that requires more
capable routers.
Useful References: [RFC8205] describes gritty details, [RFC8209]
specifies the format for the PKCS#10 certification request, and
[RFC8208] specifies the algorithms used to generate the PKCS#10's
signature.
2. Management / Router Communication
Operators are free to use either the router-driven or operator-driven
method as supported by the platform. Regardless of the method
chosen, operators first establish a protected channel between the
management system and the router. How this protected channel is
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established is router-specific and is beyond scope of this document.
Though other configuration mechanisms might be used, e.g. NetConf
(see [RFC6470]); for simplicity, in this document, the protected
channel between the management platform and the router is assumed to
be an SSH-protected CLI. See Appendix A for security considerations
for this protected channel.
3. Exchange Certificates
A number of options exist for the operator management station to
exchange PKI-related information with routers and with the RPKI
including:
- Use application/pkcs10 media type [RFC5967] to extract certificate
requests and application/pkcs7-mime [I-D.lamps-rfc5751-bis] to return
the issued certificate,
- Use FTP or HTTP per [RFC2585], and
- Use Enrollment over Secure Transport (EST) protocol per [RFC7030].
4. Set-Up
To start, the operator uses the protected channel to install the
appropriate RPKI Trust Anchor's Certificate (TA Cert) in the router.
This will later enable the router to validate the router certificate
returned in the PKCS#7 certs-only message [I-D.lamps-rfc5751-bis].
The operator also configures the Autonomous System (AS) number to be
used in the generated router certificate. This may be the sole AS
configured on the router, or an operator choice if the router is
configured with multiple ASs. A router with multiple ASs can be
configured with multiple router certificates by following the process
of this document for each desired certificate.
The operator configures or extracts from the router the BGP
Identifier [RFC4271] to be used in the generated router certificate.
In the case where the operator has chosen not to use unique per-
router certificates, a BGP Identifier of 0 may be used.
5. Generate PKCS#10
The private key, and hence the PKCS#10 certification request, which
is sometimes referred to as a Certificate Signing Request (CSR), may
be generated by the router or by the operator.
The PKCS#10 request SHOULD be saved to enable verifying that the
returned public key in the certificate corresponds to the private
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used to generate the signature on the CSR.
NOTE: The PKCS#10 certification request does not include the AS
number or the BGP Identifier for the router certificate. Therefore,
the operator transmits the AS it has chosen or the router and the BGP
Identifier as well when it sends the CSR to the CA.
5.1. Router-Generated Keys
In the router-generated method, once the protected channel is
established and the initial Set-Up (Section 4) performed, the
operator issues a command or commands for the router to generate the
public/private key pair, to generate the PKCS#10 certification
request, and to sign the PKCS#10 certification request with the
private key. Once generated, the PKCS#10 certification request is
returned to the operator over the protected channel.
The operator includes the chosen AS number and the BGP Identifier
when it sends the CSR to the CA.
NOTE: If a router were to communicate directly with a CA to have the
CA certify the PKCS#10 certification request, there would be no way
for the CA to authenticate the router. As the operator knows the
authenticity of the router, the operator mediates the communication
with the CA.
5.2. Operator-Generated Keys
In the operator-generated method, the operator generates the
public/private key pair on a management station and installs the
private key into the router over the protected channel. Beware that
experience has shown that copy and paste from a management station to
a router can be unreliable for long texts.
The operator then creates and signs the PKCS#10 certification request
with the private key; the operator includes the chosen AS number and
the BGP Identifier when it sends the CSR to the CA.
Even if the operator cannot extract the private key from the router,
this signature still provides a linkage between a private key and a
router. That is the operator can verify the proof of possession
(POP), as required by [RFC6484].
5.2.1. Using PKCS#8 to Transfer Private Key
A private key can be encapsulated in a PKCS#8 Asymmetric Key Package
[RFC5958] and should be further encapsulated in Cryptographic Message
Syntax (CMS) SignedData [RFC5652] and signed with the AS's End Entity
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(EE) private key.
The router SHOULD verify the signature of the encapsulated PKCS#8 to
ensure the returned private key did in fact come from the operator,
but this requires that the operator also provision via the CLI or
include in the SignedData the RPKI CA certificate and relevant AS's
EE certificate(s). The router should inform the operator whether or
not the signature validates to a trust anchor; this notification
mechanism is out of scope.
6. Send PKCS#10 and Receive PKCS#7
The operator uses RPKI management tools to communicate with the
global RPKI system to have the appropriate CA validate the PKCS#10
certification request, sign the key in the PKCS#10 (i.e., certify it)
and generate a PKCS#7 certs-only message, as well as publishing the
certificate in the Global RPKI. External network connectivity may be
needed if the certificate is to be published in the Global RPKI.
After the CA certifies the key, it does two things:
1. Publishes the certificate in the Global RPKI. The CA must have
connectivity to the relevant publication point, which in turn
must have external network connectivity as it is part of the
Global RPKI.
2. Returns the certificate to the operator's management station,
packaged in a PKCS#7 certs-only message, using the corresponding
method by which it received the certificate request. It SHOULD
include the certificate chain below the TA Certificate so that
the router can validate the router certificate.
In the operator-generated method, the operator SHOULD extract the
certificate from the PKCS#7 certs-only message, and verify that the
private key it holds corresponds to the returned public key. If the
operator saved the PKCS#10 it can check this correspondence by
comparing the public key in the CSR to the public key in the returned
certificate. If the operator has not saved the PKCS#10, it can check
this correspondence by generating a signature on any data and then
verifying the signature using the returned certificate.
In the operator-generated method, the operator has already installed
the private key in the router (see Section 5.2).
7. Install Certificate
The operator provisions the PKCS#7 certs-only message into the router
over the protected channel.
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The router SHOULD extract the certificate from the PKCS#7 certs-ony
message and verify that the public key corresponds to the stored
private key. If the router stored the PKCS#10, it can check this
correspondence by comparing the public key in the CSR to the public
key in the returned certificate. If the router did not store the
PKCS#10, it can check this correspondence by generating a signature
on any data and then verifying the signature using the returned
certificate. The router SHOULD inform the operator whether it
successfully received the certificate and whether or not the keys
correspond; the mechanism is out of scope.
The router SHOULD also verify that the returned certificate validates
back to the installed TA Certificate, i.e., the entire chain from the
installed TA Certificate through subordinate CAs to the BGPsec
certificate validate. To perform this verification the CA
certificate chain needs to be returned along with the router's
certificate in the PKCS#7 certs-only message. The router SHOULD
inform the operator whether or not the signature validates to a trust
anchor; this notification mechanism is out of scope.
NOTE: The signature on the PKCS#8 and Certificate need not be made by
the same entity. Signing the PKCS#8, permits more advanced
configurations where the entity that generates the keys is not the
direct CA.
8. Advanced Deployment Scenarios
More PKI-capable routers can take advantage of this increased
functionality and lighten the operator's burden. Typically, these
routers include either pre-installed manufacturer-generated
certificates (e.g., IEEE 802.1 AR [802.1AR]) or pre-installed
manufacturer-generated Pre-Shared Keys (PSK) as well as PKI-
enrollment functionality and transport protocol, e.g., CMC's "Secure
Transport" [RFC7030] or the original CMC transport protocol's
[RFC5273]. When the operator first establishes a protected channel
between the management system and the router, this pre-installed key
material is used to authenticate the router.
The operator burden shifts here to include:
1. Securely communicating the router's authentication material to
the CA prior to operator initiating the router's CSR. CAs use
authentication material to determine whether the router is
eligible to receive a certificate. Authentication material at a
minimum includes the router's AS number and BGP Identifier as
well as the router's key material, but can also include
additional information. Authentication material can be
communicated to the CA (i.e., CSRs signed by this key material
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are issued certificates with this AS and BGP Identifier) or to
the router (i.e., the operator uses the vendor-supplied
management interface to include the AS number and BGP Identifier
in the router-generated CSR).
2. Enabling the router to communicate with the CA. While the
router-to-CA communications are operator-initiated, the
operator's management interface need not be involved in the
communications path. Enabling the router-to-CA connectivity MAY
require connections to external networks (i.e., through
firewalls, NATs, etc.).
Once configured, the operator can begin the process of enrolling the
router. Because the router is communicating directly with the CA,
there is no need for the operator to retrieve the PKCS#10
certification request from the router as in Section 5 or return the
PKCS#7 certs-only message to the router as in Section 6. Note that
the checks performed by the router in Section 7, namely extracting
the certificate from the PKCS#7 certs-only message, verifying the
public key corresponds to the private key, and that the returned
certificate validated back to an installed trust anchor, SHOULD be
performed. Likewise, the router SHOULD notify the operator if any of
these fail, but this notification mechanism is out of scope.
When a router is so configured the communication with the CA SHOULD
be automatically re-established by the router at future times to
renew or rekey the certificate automatically when necessary (See
Section 8). This further reduces the tasks required of the operator.
9. Key Management
Key management does not only include key generation, key
provisioning, certificate issuance, and certificate distribution. It
also includes assurance of key validity, key roll-over, and key
preservation during router replacement. All of these
responsibilities persist for as long as the operator wishes to
operate the BGPsec-speaking router.
9.1. Key Validity
It is critical that a BGPsec speaking router is signing with a valid
private key at all times. To this end, the operator needs to ensure
the router always has a non-expired certificate. I.e. the key used
to sign BGPsec announcements always has an associated certificate
whose expiry time is after the current time.
Ensuring this is not terribly difficult but requires that either:
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1. The router has a mechanism to notify the operator that the
certificate has an impending expiration, and/or
2. The operator notes the expiry time of the certificate and uses a
calendaring program to remind them of the expiry time, and/or
3. The RPKI CA warns the operator of pending expiration, and/or
4. The operator uses some other kind of automated process to search
for and track the expiry times of router certificates.
It is advisable that expiration warnings happen well in advance of
the actual expiry time.
Regardless of the technique used to track router certificate expiry
times, it is advisable to notify additional operators in the same
organization as the expiry time approaches thereby ensuring that the
forgetfulness of one operator does not affect the entire
organization.
Depending on inter-operator relationship, it may be helpful to notify
a peer operator that one or more of their certificates are about to
expire.
9.2. Key Roll-Over
Routers that support multiple private keys also greatly increase the
chance that routers can continuously speak BGPsec because the new
private key and certificate can be obtained and distributed prior to
expiration of the operational key. Obviously, the router needs to
know when to start using the new key. Once the new key is being
used, having the already distributed certificate ensures continuous
operation.
More information on how to proceed with a Key Roll-Over is described
in [I-D.sidrops-bgpsec-rollover].
9.3. Key Revocation
Certain unfortunate circumstances may occur causing a need to revoke
a router's BGPsec certificate. When this occurs, the operator needs
to use the RPKI CA system to revoke the certificate by placing the
router's BGPsec certificate on the Certificate Revocation List (CRL)
as well as re-keying the router's certificate.
When an active router key is to be revoked, the process of requesting
the CA to revoke, the process of the CA actually revoking the
router's certificate, and then the process of re-keying/renewing the
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router's certificate, (possibly distributing a new key and
certificate to the router), and distributing the status takes time
during which the operator must decide how they wish to maintain
continuity of operations, with or without the compromised private
key, or whether they wish to bring the router offline to address the
compromise.
Keeping the router operational and BGPsec-speaking is the ideal goal,
but if operational practices do not allow this then reconfiguring the
router to disable BGPsec is likely preferred to bringing the router
offline.
Routers which support more than one private key, where one is
operational and other(s) are soon-to-be-operational, facilitate
revocation events because the operator can configure the router to
make a soon-to-be-operational key operational, request revocation of
the compromised key, and then make a next generation soon-to-be-
operational key, all hopefully without needing to take offline or
reboot the router. For routers which support only one operational
key, the operators should create or install the new private key, and
then request revocation of the certificate corresponding to the
compromised private key.
9.4. Router Replacement
Currently routers often generate private keys for uses such as SSH,
and the private keys may not be seen or off-loaded from the router.
While this is good security, it creates difficulties when a routing
engine or whole router must be replaced in the field and all software
which accesses the router must be updated with the new keys. Also,
any network based initial contact with a new routing engine requires
trust in the public key presented on first contact.
To allow operators to quickly replace routers without requiring
update and distribution of the corresponding public keys in the RPKI,
routers SHOULD allow the private BGPsec key to inserted via a
protected channel, e.g., SSH, NetConf (see [RFC6470]), SNMP. This
lets the operator escrow the old private key via the mechanism used
for operator-generated keys, see Section 5.2, such that it can be re-
inserted into a replacement router. The router MAY allow the private
key to be to be off-loaded via the protected channel, but this SHOULD
be paired with functionality that sets the key into a permanent non-
exportable state to ensure that it is not off-loaded at a future time
by unauthorized operations.
10. Security Considerations
The router's manual will describe whether the router supports one,
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the other, or both of the key generation options discussed in the
earlier sections of this draft as well as other important security-
related information (e.g., how to SSH to the router). After
familiarizing one's self with the capabilities of the router, an
operator is encouraged to ensure that the router is patched with the
latest software updates available from the manufacturer.
This document defines no protocols so in some sense introduces no new
security considerations. However, it relies on many others and the
security considerations in the referenced documents should be
consulted; notably, those document listed in Section 1 should be
consulted first. PKI-relying protocols, of which BGPsec is one, have
many issues to consider so many in fact entire books have been
written to address them; so listing all PKI-related security
considerations is neither useful nor helpful; regardless, some boot-
strapping-related issues are listed here that are worth repeating:
Public-Private key pair generation: Mistakes here are for all
practical purposes catastrophic because PKIs rely on the pairing
of a difficult to generate public-private key pair with a signer;
all key pairs MUST be generated from a good source of non-
deterministic random input [RFC4086].
Private key protection at rest: Mistakes here are for all practical
purposes catastrophic because disclosure of the private key allows
another entity to masquerade as (i.e., impersonate) the signer;
all private keys MUST be protected when at rest in a secure
fashion. Obviously, how each router protects private keys is
implementation specific. Likewise, the local storage format for
the private key is just that, a local matter.
Private key protection in transit: Mistakes here are for all
practical purposes catastrophic because disclosure of the private
key allows another entity to masquerade as (i.e., impersonate) the
signer; transport security is therefore strongly RECOMMENDED. The
level of security provided by the transport layer's security
mechanism SHOULD be commensurate with the strength of the BGPsec
key; there's no point in spending time and energy to generate an
excellent public-private key pair and then transmit the private
key in the clear or with a known-to-be-broken algorithm, as it
just undermines trust that the private key has been kept private.
Additionally, operators SHOULD ensure the transport security
mechanism is up to date, in order to addresses all known
implementation bugs.
SSH key management is known, in some cases, to be lax
[I-D.ylonen-sshkeybcp]; employees that no longer need access to a
routers SHOULD be removed the router to ensure only those authorized
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have access to a router.
Though the CA's certificate is installed on the router and used to
verify that the returned certificate is in fact signed by the CA, the
revocation status of the CA's certificate is rarely checked as the
router may not have global connectivity or CRL-aware software. The
operator MUST ensure that the installed CA certificate is valid.
11. IANA Considerations
This document has no IANA Considerations.
12. References
12.1. Normative References
[I-D.sidrops-bgpsec-rollover]
Weis, B, R. Gagliano, and K. Patel, "BGPsec Router
Certificate Rollover", draft-ietf-sidrops-bgpsec-
rollover (work in progress), December 2017.
[I-D.lamps-rfc5751-bis]
Schaad, J., Ramsdell, B, S. Turner,
"Secure/Multipurpose Internet Mail Extension (S/MIME)
Version 4.0", draft-ietf-lamps-rfc5751-
bis (work in progress), July 2018.
[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>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005, <https://www.rfc-
editor.org/info/rfc4086>.
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, <https://www.rfc-editor.org/info/rfc4253>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI
10.17487/RFC4271, January 2006, <https://www.rfc-
editor.org/info/rfc4271>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
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<https://www.rfc-editor.org/info/rfc5652>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958, DOI
10.17487/RFC5958, August 2010, <https://www.rfc-
editor.org/info/rfc5958>.
[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>.
[RFC8208] Turner, S. and O. Borchert, "BGPsec Algorithms, Key
Formats, and Signature Formats", RFC 8208, DOI
10.17487/RFC8208, September 2017, <https://www.rfc-
editor.org/info/rfc8208>.
[RFC8209] Reynolds, M., Turner, S., and S. Kent, "A Profile for
BGPsec Router Certificates, Certificate Revocation Lists,
and Certification Requests", RFC 8209, DOI
10.17487/RFC8209, September 2017, <https://www.rfc-
editor.org/info/rfc8209>.
[802.1AR] IEEE SA-Standards Board, "IEEE Standard for Local and
metropolitan area networks - Secure Device Identity",
December 2009,
<http://standards.ieee.org/findstds/standard/802.1AR-
2009.html>.
12.1. Informative References
[I-D.ylonen-sshkeybcp]
Ylonen, T. and G. Kent, "Managing SSH Keys for Automated
Access - Current Recommended Practice", draft-ylonen-
sshkeybcp (work in progress), April 2013.
[RFC2585] Housley, R. and P. Hoffman, "Internet X.509 Public Key
Infrastructure Operational Protocols: FTP and HTTP",
RFC 2585, DOI 10.17487/RFC2585, May 1999,
<https://www.rfc-editor.org/info/rfc2585>.
[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For
Public Keys Used For Exchanging Symmetric Keys", BCP 86,
RFC 3766, DOI 10.17487/RFC3766, April 2004,
<https://www.rfc-editor.org/info/rfc3766>.
[RFC5273] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC): Transport Protocols", RFC 5273, DOI
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10.17487/RFC5273, June 2008, <https://www.rfc-
editor.org/info/rfc5273>.
[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, DOI 10.17487/RFC5480, March 2009,
<https://www.rfc-editor.org/info/rfc5480>.
[RFC5647] Igoe, K. and J. Solinas, "AES Galois Counter Mode for the
Secure Shell Transport Layer Protocol", RFC 5647, DOI
10.17487/RFC5647, August 2009, <https://www.rfc-
editor.org/info/rfc5647>.
[RFC5656] Stebila, D. and J. Green, "Elliptic Curve Algorithm
Integration in the Secure Shell Transport Layer",
RFC 5656, DOI 10.17487/RFC5656, December 2009,
<https://www.rfc-editor.org/info/rfc5656>.
[RFC5967] Turner, S., "The application/pkcs10 Media Type", RFC 5967,
DOI 10.17487/RFC5967, August 2010, <https://www.rfc-
editor.org/info/rfc5967>.
[RFC6187] Igoe, K. and D. Stebila, "X.509v3 Certificates for Secure
Shell Authentication", RFC 6187, DOI 10.17487/RFC6187,
March 2011, <https://www.rfc-editor.org/info/rfc6187>.
[RFC6470] Bierman, A., "Network Configuration Protocol (NETCONF)
Base Notifications", RFC 6470, DOI 10.17487/RFC6470,
February 2012, <https://www.rfc-editor.org/info/rfc6470>.
[RFC6484] Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate
Policy (CP) for the Resource Public Key Infrastructure
(RPKI)", BCP 173, RFC 6484, DOI 10.17487/RFC6484, February
2012, <https://www.rfc-editor.org/info/rfc6484>.
[RFC6668] Bider, D. and M. Baushke, "SHA-2 Data Integrity
Verification for the Secure Shell (SSH) Transport Layer
Protocol", RFC 6668, DOI 10.17487/RFC6668, July 2012,
<https://www.rfc-editor.org/info/rfc6668>.
[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>.
[RFC8205] Lepinski, M., Ed., and K. Sriram, Ed., "BGPsec Protocol
Specification", RFC 8205, DOI 10.17487/RFC8205, September
2017, <https://www.rfc-editor.org/info/rfc8205>.
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[SP800-57] National Institute of Standards and Technology (NIST),
Special Publication 800-57: Recommendation for Key
Management - Part 1 (Revised), March 2007.
Appendix A. Management/Router Channel Security
Encryption, integrity, authentication, and key exchange algorithms
used by the protected channel SHOULD be of equal or greater strength
than the BGPsec keys they protect, which for the algorithm specified
in [RFC8208] is 128-bit; see [RFC5480] and by reference [SP800-57]
for information about this strength claim as well as [RFC3766] for
"how to determine the length of an asymmetric key as a function of a
symmetric key strength requirement." In other words, for the
encryption algorithm, do not use export grade crypto (40-56 bits of
security), do not use Triple DES (112 bits of security). Suggested
minimum algorithms would be AES-128: aes128-cbc [RFC4253] and
AEAD_AES_128_GCM [RFC5647] for encryption, hmac-sha2-256 [RFC6668] or
AESAD_AES_128_GCM [RFC5647] for integrity, ecdsa-sha2-nistp256
[RFC5656] for authentication, and ecdh-sha2-nistp256 [RFC5656] for
key exchange.
Some routers support the use of public key certificates and SSH. The
certificates used for the SSH session are different than the
certificates used for BGPsec. The certificates used with SSH should
also enable a level of security commensurate with BGPsec keys;
x509v3-ecdsa-sha2-nistp256 [RFC6187] could be used for
authentication.
The protected channel must provide confidentiality, authentication,
and integrity and replay protection.
Appendix B. The n00b Guide to BGPsec Key Management
This appendix is informative. It attempts to explain all of the PKI
technobabble in plainer language.
BGPsec speakers send signed BGPsec updates that are verified by other
BGPsec speakers. In PKI parlance, the senders are referred to as
signers and the receivers are referred to as relying parties. The
signers with which we are concerned here are routers signing BGPsec
updates. Signers use private keys to sign and relying parties use
the corresponding public keys, in the form of X.509 public key
certificates, to verify signatures. The third party involved is the
entity that issues the X.509 public key certificate, the
Certification Authority (CA). Key management is all about making
these key pairs and the certificates, as well as ensuring that the
relying parties trust that the certified public keys in fact
correspond to the signers' private keys.
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The specifics of key management greatly depend on the routers as well
as management interfaces provided by the routers' vendor. Because of
these differences, it is hard to write a definitive "how to," but
this guide is intended to arm operators with enough information to
ask the right questions. The other aspect that makes this guide
informative is that the steps for the do-it-yourself (DIY) approach
involve arcane commands while the GUI-based vendor-assisted
management console approach will likely hide all of those commands
behind some button clicks. Regardless, the operator will end up with
a BGPsec-enabled router. Initially, we focus on the DIY approach and
then follow up with some information about the GUI-based approach.
The first step in the DIY approach is to generate a private key; but
in fact what you do is create a key pair; one part, the private key,
is kept very private and the other part, the public key, is given out
to verify whatever is signed. The two models for how to create the
key pair are the subject of this document, but it boils down to
either doing it on-router (router-driven) or off-router (operator-
driven).
If you are generating keys on the router (router-driven), then you
will need to access the router. Again, how you access the router is
router-specific, but generally the DIY approach uses the CLI and
accessing the router either directly via the router's craft port or
over the network on an administrative interface. If accessing the
router over the network be sure to do it securely (i.e., use SSHv2).
Once logged into the router, issue a command or a series of commands
that will generate the key pair for the algorithms referenced in the
main body of this document; consult your router's documentation for
the specific commands. The key generation process will yield
multiple files: the private key and the public key; the file format
varies depending on the arcane command you issued, but generally the
files are DER or PEM-encoded.
The second step is to generate the certification request, which is
often referred to as a certificate signing request (CSR) or PKCS#10
certification request, and to send it to the CA to be signed. To
generate the CSR, you issue some more arcane commands while logged
into the router; using the private key just generated to sign the
certification request with the algorithms referenced in the main body
of this document; the CSR is signed to prove to the CA that the
router has possession of the private key (i.e., the signature is the
proof-of-possession). The output of the command is the CSR file; the
file format varies depending on the arcane command you issued, but
generally the files are DER or PEM-encoded.
The third step is to retrieve the signed CSR from the router and send
it to the CA. But before sending it, you need to also send the CA
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the subject name and serial number for the router. The CA needs this
information to issue the certificate. How you get the CSR to the CA,
is beyond the scope of this document. While you are still connected
to the router, install the Trust Anchor (TA) for the root of the PKI.
At this point, you no longer need access to the router for BGPsec-
related initiation purposes.
The fourth step is for the CA to issue the certificate based on the
CSR you sent; the certificate will include the subject name, serial
number, public key, and other fields as well as being signed by the
CA. After the CA issues the certificate, the CA returns the
certificate, and posts the certificate to the RPKI repository. Check
that the certificate corresponds to the private key by verifying the
signature on the CSR sent to the CA; this is just a check to make
sure that the CA issued a certificate that includes a public key that
is the pair of the private key (i.e., the math will work when
verifying a signature generated by the private with the returned
certificate).
If generating the keys off-router (operator-driven), then the same
steps are used as the on-router key generation, (possibly with the
same arcane commands as those used in the on-router approach), but no
access to the router is needed the first three steps are done on an
administrative workstation: o Step 1: Generate key pair; o Step 2:
Create CSR and sign CSR with private key, and; o Step 3: Send CSR
file with the subject name and serial number to CA.
After the CA has returned the certificate and you have checked the
certificate, you need to put the private key and TA in the router.
Assuming the DIY approach, you will be using the CLI and accessing
the router either directly via the router's craft port or over the
network on an admin interface; if accessing the router over the
network make doubly sure it is done securely (i.e., use SSHv2)
because the private key is being moved over the network. At this
point, access to the router is no longer needed for BGPsec-related
initiation purposes.
NOTE: Regardless of the approach taken, the first three steps could
trivially be collapsed by a vendor-provided script to yield the
private key and the signed CSR.
Given a GUI-based vendor-assisted management console, then all of
these steps will likely be hidden behind pointing and clicking the
way through BGPsec-enabling the router.
The scenarios described above require the operator to access each
router, which does not scale well to large networks. An alternative
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would be to create an image, perform the necessary steps to get the
private key and trust anchor on the image, and then install the image
via a management protocol.
One final word of advice; certificates include a notAfter field that
unsurprisingly indicates when relying parties should no longer trust
the certificate. To avoid having routers with expired certificates
follow the recommendations in the Certification Policy (CP) [RFC6484]
and make sure to renew the certificate at least one week prior to the
notAfter date. Set a calendar reminder in order not to forget!
Authors' Addresses
Randy Bush
IIJ / Dragon Research Labs
5147 Crystal Springs
Bainbridge Island, Washington 98110
US
Email: randy@psg.com
Sean Turner
sn3rd
Email: sean@sn3rd.com
Keyur Patel
Arrcus, Inc.
Email: keyur@arrcus.com
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