draft-ietf-sidr-bgpsec-protocol-03.txt   draft-ietf-sidr-bgpsec-protocol-04.txt 
Network Working Group M. Lepinski, Ed. Network Working Group M. Lepinski, Ed.
Internet-Draft BBN Internet-Draft BBN
Intended status: Standards Track May 11, 2012 Intended status: Standards Track July 16, 2012
Expires: November 12, 2012 Expires: January 17, 2013
BGPSEC Protocol Specification BGPSEC Protocol Specification
draft-ietf-sidr-bgpsec-protocol-03 draft-ietf-sidr-bgpsec-protocol-04
Abstract Abstract
This document describes BGPSEC, an extension to the Border Gateway This document describes BGPSEC, an extension to the Border Gateway
Protocol (BGP) that provides security for the AS-PATH attribute in Protocol (BGP) that provides security for the AS-PATH attribute in
BGP update messages. BGPSEC is implemented via a new optional non- BGP update messages. BGPSEC is implemented via a new optional non-
transitive BGP path attribute that carries a digital signature transitive BGP path attribute that carries a digital signature
produced by each autonomous system on the AS-PATH. produced by each autonomous system on the AS-PATH.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [4]. document are to be interpreted as described in RFC 2119 [8].
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 12, 2012. This Internet-Draft will expire on January 17, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BGPSEC Negotiation . . . . . . . . . . . . . . . . . . . . . . 3 2. BGPSEC Negotiation . . . . . . . . . . . . . . . . . . . . . . 3
3. The BGPSEC_Path_Signatures Attribute . . . . . . . . . . . . . 6 3. The BGPSEC_Path_Signatures Attribute . . . . . . . . . . . . . 6
3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Additional_Info . . . . . . . . . . . . . . . . . . . . . 9 3.2. Additional_Info . . . . . . . . . . . . . . . . . . . . . 9
3.3. Signature_Block . . . . . . . . . . . . . . . . . . . . . 11 3.3. Signature_Block . . . . . . . . . . . . . . . . . . . . . 11
4. Generating a BGPSEC Update . . . . . . . . . . . . . . . . . . 12 4. Generating a BGPSEC Update . . . . . . . . . . . . . . . . . . 12
4.1. Originating a New BGPSEC Update . . . . . . . . . . . . . 13 4.1. Originating a New BGPSEC Update . . . . . . . . . . . . . 13
4.2. Propagating a Route Advertisement . . . . . . . . . . . . 16 4.2. Propagating a Route Advertisement . . . . . . . . . . . . 16
5. Processing a Received BGPSEC Update . . . . . . . . . . . . . 19 4.3. Reconstructing the AS_Path Attribute . . . . . . . . . . . 19
5.1. Validation Algorithm . . . . . . . . . . . . . . . . . . . 20 4.4. Processing Instructions for Confederation Members . . . . 19
6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 24 5. Processing a Received BGPSEC Update . . . . . . . . . . . . . 21
6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 24 5.1. Validation Algorithm . . . . . . . . . . . . . . . . . . . 22
6.2. Extensibility Considerations . . . . . . . . . . . . . . . 25 6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 26
7. Security Considerations . . . . . . . . . . . . . . . . . . . 26 6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 26
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 29 6.2. Extensibility Considerations . . . . . . . . . . . . . . . 27
8.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 29 7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 30 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 31
9. Normative References . . . . . . . . . . . . . . . . . . . . . 30 8.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 31
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 31 8.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 32
9. Normative References . . . . . . . . . . . . . . . . . . . . . 32
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 33
1. Introduction 1. Introduction
This document describes BGPSEC, a mechanism for providing path This document describes BGPSEC, a mechanism for providing path
security for Border Gateway Protocol (BGP) [1] route advertisements. security for Border Gateway Protocol (BGP) [1] route advertisements.
That is, a BGP speaker who receives a valid BGPSEC update has That is, a BGP speaker who receives a valid BGPSEC update has
cryptographic assurance that the advertised route has the following cryptographic assurance that the advertised route has the following
two properties: two properties:
1. The route was originated by an AS that has been explicitly 1. The route was originated by an AS that has been explicitly
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the AS_Path. the AS_Path.
This document specifies a new optional (non-transitive) BGP path This document specifies a new optional (non-transitive) BGP path
attribute, BGPSEC_Path_Signatures. It also describes how a BGPSEC- attribute, BGPSEC_Path_Signatures. It also describes how a BGPSEC-
compliant BGP speaker (referred to hereafter as a BGPSEC speaker) can compliant BGP speaker (referred to hereafter as a BGPSEC speaker) can
generate, propagate, and validate BGP update messages containing this generate, propagate, and validate BGP update messages containing this
attribute to obtain the above assurances. attribute to obtain the above assurances.
BGPSEC relies on the Resource Public Key Infrastructure (RPKI) BGPSEC relies on the Resource Public Key Infrastructure (RPKI)
certificates that attest to the allocation of AS number and IP certificates that attest to the allocation of AS number and IP
address resources. (For more information on the RPKI, see [7] and address resources. (For more information on the RPKI, see [6] and
the documents referenced therein.) Any BGPSEC speaker who wishes to the documents referenced therein.) Any BGPSEC speaker who wishes to
send BGP update messages to external peers (eBGP) containing the send BGP update messages to external peers (eBGP) containing the
BGPSEC_Path_Signatures must have an RPKI end-entity certificate (as BGPSEC_Path_Signatures must have an RPKI end-entity certificate (as
well as the associated private signing key) corresponding to the well as the associated private signing key) corresponding to the
BGPSEC speaker's AS number. Note, however, that a BGPSEC speaker BGPSEC speaker's AS number. Note, however, that a BGPSEC speaker
does not require such a certificate in order to validate update does not require such a certificate in order to validate update
messages containing the BGPSEC_Path_Signatures attribute. messages containing the BGPSEC_Path_Signatures attribute.
2. BGPSEC Negotiation 2. BGPSEC Negotiation
This document defines a new BGP capability [3]that allows a BGP This document defines a new BGP capability [4]that allows a BGP
speaker to advertise to its neighbors the ability to send and/or speaker to advertise to its neighbors the ability to send and/or
receive BGPSEC update messages (i.e., update messages containing the receive BGPSEC update messages (i.e., update messages containing the
BGPSEC_Path_Signatures attribute). BGPSEC_Path_Signatures attribute).
This capability has capability code : TBD This capability has capability code : TBD
The capability length for this capability MUST be set to 5. The capability length for this capability MUST be set to 5.
The three octets of the capability value are specified as follows. The three octets of the capability value are specified as follows.
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The fifth octet in the capability contains the 8-bit Subsequent The fifth octet in the capability contains the 8-bit Subsequent
Address Family Identifier (SAFI). This value is encoded as in the Address Family Identifier (SAFI). This value is encoded as in the
BGP multiprotocol extensions [2]. BGP multiprotocol extensions [2].
Note that if the BGPSEC speaker wishes to use BGPSEC with two Note that if the BGPSEC speaker wishes to use BGPSEC with two
different address families (i.e., IPv4 and IPv6) over the same BGP different address families (i.e., IPv4 and IPv6) over the same BGP
session, then the speaker must include two instances of this session, then the speaker must include two instances of this
capability (one for each address family) in the BGP OPEN message. A capability (one for each address family) in the BGP OPEN message. A
BGPSEC speaker SHOULD NOT advertise the capability of BGPSEC support BGPSEC speaker SHOULD NOT advertise the capability of BGPSEC support
for any <AFI, SAFI> combination unless it has also includes the for any <AFI, SAFI> combination unless it has also advertises the
multiprotocol extension capability for the same <AFI, SAFI> multiprotocol extension capability for the same <AFI, SAFI>
combination [2]. combination [2].
By indicating support for receiving BGPSEC update messages, a BGP By indicating support for receiving BGPSEC update messages, a BGP
speaker is, in particular, indicating that the following are true: speaker is, in particular, indicating that the following are true:
o The BGP speaker understands the BGPSEC_Path_Signatures attribute o The BGP speaker understands the BGPSEC_Path_Signatures attribute
(see Section 3). (see Section 3).
o The BGP speaker supports 4-byte AS numbers (see RFC 4893). o The BGP speaker supports 4-byte AS numbers (see RFC 4893).
Note that BGPSEC update messages can be quite large, therefore any Note that BGPSEC update messages can be quite large, therefore any
BGPSEC speaker announcing the capability to receive BGPSEC messages BGPSEC speaker announcing the capability to receive BGPSEC messages
SHOULD also announce support for the capability to receive BGP SHOULD also announce support for the capability to receive BGP
extended messages [5]. extended messages [9].
A BGP speaker MUST NOT send an update message containing the A BGP speaker MUST NOT send an update message containing the
BGPSEC_Path_Signatures attribute within a given BGP session unless BGPSEC_Path_Signatures attribute within a given BGP session unless
both of the following are true: both of the following are true:
o The BGP speaker indicated support for sending BGPSEC update o The BGP speaker indicated support for sending BGPSEC update
messages in its open message. messages in its open message.
o The peer of the BGP speaker indicated support for receiving BGPSEC o The peer of the BGP speaker indicated support for receiving BGPSEC
update messages in its open message. update messages in its open message.
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The BGPSEC_Path_Signatures attribute is a new optional (non- The BGPSEC_Path_Signatures attribute is a new optional (non-
transitive) BGP path attribute. transitive) BGP path attribute.
This document registers a new attribute type code for this attribute This document registers a new attribute type code for this attribute
: TBD : TBD
The BGPSEC_Path_Signatures algorithm carries the secured AS Path The BGPSEC_Path_Signatures algorithm carries the secured AS Path
information, including the digital signatures that protect this AS information, including the digital signatures that protect this AS
Path information. We refer to those update messages that contain the Path information. We refer to those update messages that contain the
BGPSEC_Path_Signatures attribute as "BGPSEC Update messages". The BGPSEC_Path_Signatures attribute as "BGPSEC Update messages". The
BGPSEC_Path_Signatures attribute replaces the AS_PATH attribute. BGPSEC_Path_Signatures attribute replaces the AS_PATH attribute, in a
Update messages that contain the BGPSEC_Path_Signatures attribute BGPSEC update message. That is, update messages that contain the
MUST NOT contain the AS_PATH or AS4_PATH attribute. BGPSEC_Path_Signatures attribute MUST NOT contain the AS_PATH
attribute.
The BGPSEC_Path_Signatures attribute is made up of several parts. The BGPSEC_Path_Signatures attribute is made up of several parts.
The following high-level diagram provides an overview of the The following high-level diagram provides an overview of the
structure of the BGPSEC_Path_Signatures attribute structure of the BGPSEC_Path_Signatures attribute:
High-Level Diagram of the BGPSEC_Path_Signatures Attribute High-Level Diagram of the BGPSEC_Path_Signatures Attribute
BGPSEC_Path_Signatures BGPSEC_Path_Signatures
+---------------------------------------------------------+ +---------------------------------------------------------+
| +-----------------+ | | +-----------------+ |
| | Secure Path | +-----------------+ | | | Secure Path | +-----------------+ |
| +-----------------+ | Additional Info | | | +-----------------+ | Additional Info | |
| | AS X | +-----------------+ | | | AS X | +-----------------+ |
| | pCount X | | Info Type | | | | pCount X | | Info Type | |
| | Flags X | | Info Length | | | | Flags X | | Info Length | |
| | AS Y | | Info Value | | | | AS Y | | Info Value | |
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+-------------------------------------------------------+ +-------------------------------------------------------+
| Secure_Path (variable) | | Secure_Path (variable) |
+-------------------------------------------------------+ +-------------------------------------------------------+
| Additional_Info (variable) | | Additional_Info (variable) |
+-------------------------------------------------------+ +-------------------------------------------------------+
| Sequence of one or two Signature_Blocks (variable) | | Sequence of one or two Signature_Blocks (variable) |
+-------------------------------------------------------+ +-------------------------------------------------------+
The Secure_Path contains AS Path information for the BGPSEC update The Secure_Path contains AS Path information for the BGPSEC update
message. This is logically equivalent to the information that would message. This is logically equivalent to the information that would
be contained in the AS4_PATH attribute. A BGPSEC udpate message be contained in the AS_PATH attribute. A BGPSEC update message
containing the BGPSEC_PATH_SIGNATURES attribute MUST NOT contain the containing the BGPSEC_PATH_SIGNATURES attribute MUST NOT contain the
AS_PATH or AS4_PATH attribute. The format of the Secure_Path is AS_PATH attribute. The format of the Secure_Path is described below
described below in Section 3.1. in Section 3.1.
The Additional_Info contains additional signed information about the The Additional_Info contains additional signed information about the
update message. Additional_Info is specified as a type-length-value update message. Additional_Info is specified as a type-length-value
field for future extensibility. However, this specification defines field for future extensibility. However, this specification defines
only a single (null) type of Additional Info which has zero length. only a single (null) type of Additional Info which has zero length.
It is anticipated that future specifications may specify semantics It is anticipated that future specifications may specify semantics
for Info Types other than zero. See Section 3.2 below for more for Info Types other than zero. See Section 3.2 below for more
detail. detail.
The BGPSEC_Path_Signatures attribute will contain one or two The BGPSEC_Path_Signatures attribute will contain one or two
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algorithm suite and one for the new algorithm suite) during the algorithm suite and one for the new algorithm suite) during the
transition period. (See Section 6.1 for more discussion of algorithm transition period. (See Section 6.1 for more discussion of algorithm
transitions.) The format of the Signature_Blocks is described below transitions.) The format of the Signature_Blocks is described below
in Section 3.3. in Section 3.3.
3.1. Secure_Path 3.1. Secure_Path
Here we provide a detailed description of the Secure_Path information Here we provide a detailed description of the Secure_Path information
in the BGPSEC_Path_Signatures attribute. in the BGPSEC_Path_Signatures attribute.
Signature_Path Secure_Path
+-----------------------------------------------+ +-----------------------------------------------+
| Secure_Path Length (2 octets) | | Secure_Path Length (2 octets) |
+-----------------------------------------------+ +-----------------------------------------------+
| One or More Secure_Path Segments (variable) | | One or More Secure_Path Segments (variable) |
+-----------------------------------------------+ +-----------------------------------------------+
The Secure_Path Length contains the length (in octets) of the The Secure_Path Length contains the length (in octets) of the
variable-length sequence of Secure_Path Segments. Note that this variable-length sequence of Secure_Path Segments. As explained
means the length is six times the number Secure_Path Segments (i.e., below, each Secure_Path segment is six octets long. Note that this
the number of AS numbers in the path). means the Secure_Path Length is six times the number Secure_Path
Segments (i.e., the number of AS numbers in the path).
The Secure_Path contains one Secure_Path segment for each (distinct) The Secure_Path contains one Secure_Path segment for each (distinct)
Autonomous System in the path to the NLRI specified in the update Autonomous System in the path to the NLRI specified in the update
message. message.
Secure_Path Segment Secure_Path Segment
+----------------------------+ +----------------------------+
| AS Number (4 octets) | | AS Number (4 octets) |
+----------------------------+ +----------------------------+
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The AS Number is the AS number of the BGP speaker that added this The AS Number is the AS number of the BGP speaker that added this
Secure_Path segment to the BGPSEC_Path_Signatures attribute. (See Secure_Path segment to the BGPSEC_Path_Signatures attribute. (See
Section 4 for more information on populating this field.) Section 4 for more information on populating this field.)
The pCount field contains the number of repetitions of the associated The pCount field contains the number of repetitions of the associated
autonomous system number that the signature covers. This field autonomous system number that the signature covers. This field
enables a BGPSEC speaker to mimic the semantics of adding multiple enables a BGPSEC speaker to mimic the semantics of adding multiple
copies of their AS to the AS_PATH without requiring the speaker to copies of their AS to the AS_PATH without requiring the speaker to
generate multiple signatures. generate multiple signatures.
The Flags field is reserved for future use. This octet is digitally The first bit of the Flags field is the Entering_Confed flag. The
signed. These octets MUST be set to zero by the sender. The Entering_Confed flag is set to one in the Secure_Path Segment
receiver uses this octet to verify the digital signature (regardless corresponding to the first Autonomous System in a confederation [3].
of what value they contain), but otherwise ignores the octet (see (That is, the Secure_Path Segment corresponding to the AS that would
Section 4 for sender instructions and Section 5 for reciever otherwise have created an AS_Path segment of type AS_Confed_Sequence
validation instructions). in a non-BGSPEC update message.) In all other cases the
Entering_Confed flag is set to zero.
EDITOR'S NOTE: The existence of a signed flags field provides the The remaining seven bits of the Flags field are reserved for future
possibility of adding in the future (in a backwards compatible use. These bits MUST be set to zero by the sender. The receiver
fashion) a new feature that requires per-AS signed bits. For uses the entire Flags octet to verify the digital signature
(regardless of what value the reserved bits contain), but otherwise
ignores the reserved flags (see Section 4 for sender instructions and
Section 5 for receiver validation instructions).
EDITOR'S NOTE: The unused portion of the signed flags field provides
the possibility of adding in the future (in a backwards compatible
fashion) a new feature that requires some per-AS signed bits. For
example, one could use a couple bits from this flag field to mark example, one could use a couple bits from this flag field to mark
some property of the connection between two ASes. some property of the connection between two ASes.
3.2. Additional_Info 3.2. Additional_Info
Here we provide a detailed description of the Additional_Info in the Here we provide a detailed description of the Additional_Info in the
BGPSEC_Path_Signatures attribute. BGPSEC_Path_Signatures attribute.
Signature-Block Additional_Info
+---------------------------------------------+ +---------------------------------------------+
| Info Type (1 octet) | | Info Type (1 octet) |
+---------------------------------------------+ +---------------------------------------------+
| Info Length (1 octet) | | Info Length (1 octet) |
+---------------------------------------------+ +---------------------------------------------+
| Info Value (variable) | | Info Value (variable) |
+---------------------------------------------+ +---------------------------------------------+
The Info Type field is a one-octet value that identifies the type of The Info Type field is a one-octet value that identifies the type of
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Expire Time that was used to provide protection against replay of old Expire Time that was used to provide protection against replay of old
(stale) digital signatures or failure to propagate a withdrawal (stale) digital signatures or failure to propagate a withdrawal
message. This mechanism was removed from the current version of the message. This mechanism was removed from the current version of the
document. Please see the SIDR mailing list for discussions related document. Please see the SIDR mailing list for discussions related
to protection against replay attacks. Depending on the result of to protection against replay attacks. Depending on the result of
discussions within the SIDR working group this Additional Info field discussions within the SIDR working group this Additional Info field
could at some future point be used to re-introduce Expire Time, or could at some future point be used to re-introduce Expire Time, or
some other octets used in a future replay protection mechanism. The some other octets used in a future replay protection mechanism. The
authors believe that the current instructions whereby the sender uses authors believe that the current instructions whereby the sender uses
a null Additional_Info type and the receiver ignores Additional_Info a null Additional_Info type and the receiver ignores Additional_Info
types that it does not understand provides an oportunity to use these types that it does not understand provides an opportunity to use
octets in the future in a backwards-compatible fashion. these octets in the future in a backwards-compatible fashion.
3.3. Signature_Block 3.3. Signature_Block
Here we provide a detailed description of the Signature_Blocks in the Here we provide a detailed description of the Signature_Blocks in the
BGPSEC_Path_Signatures attribute. BGPSEC_Path_Signatures attribute.
Signature_Block Signature_Block
+---------------------------------------------+ +---------------------------------------------+
| Algorithm Suite Identifier (1 octet) | | Algorithm Suite Identifier (1 octet) |
+---------------------------------------------+ +---------------------------------------------+
| Signature_Block Length (2 octets) | | Signature_Block Length (2 octets) |
+---------------------------------------------+ +---------------------------------------------+
| Sequence of Signature Segments (variable) | | Sequence of Signature Segments (variable) |
+---------------------------------------------+ +---------------------------------------------+
The Algorithm Suite Identifier is a one-octet identifier specifying The Algorithm Suite Identifier is a one-octet identifier specifying
the digest algorithm and digital signature algorithm used to produce the digest algorithm and digital signature algorithm used to produce
the digital signature in each Signature Segment. An IANA registry of the digital signature in each Signature Segment. An IANA registry of
algorithm identifiers for use in BGPSEC is created in the BGPSEC algorithm identifiers for use in BGPSEC is created in the BGPSEC
algorithms document[10]. algorithms document[12].
The Signature_Block Length is the total number of octets in all The Signature_Block Length is the total number of octets in all
Signature Segments (i.e., the total size of the variable-length Signature Segments (i.e., the total size of the variable-length
portion of the Signature_Block.) portion of the Signature_Block.)
A Signature_Block has exactly one Signature Segment for each A Signature_Block has exactly one Signature Segment for each
Secure_Path Segment in the Secure_Path portion of the Secure_Path Segment in the Secure_Path portion of the
BGPSEC_Path_Signatures Attribute. (That is, one Signature Segment BGPSEC_Path_Signatures Attribute. (That is, one Signature Segment
for each distinct AS on the path for the NLRI in the Update message.) for each distinct AS on the path for the NLRI in the Update message.)
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in the received update. If a BGPSEC speaker wishes to advertise in the received update. If a BGPSEC speaker wishes to advertise
routes to multiple NLRI, then it MUST generate a separate BGPSEC routes to multiple NLRI, then it MUST generate a separate BGPSEC
update message for each NLRI. update message for each NLRI.
Note that in order to create or add a new signature to a BGPSEC Note that in order to create or add a new signature to a BGPSEC
update message with a given algorithm suite, the BGPSEC speaker must update message with a given algorithm suite, the BGPSEC speaker must
possess a private key suitable for generating signatures for this possess a private key suitable for generating signatures for this
algorithm suite. Additionally, this private key must correspond to algorithm suite. Additionally, this private key must correspond to
the public key in a valid Resource PKI end-entity certificate whose the public key in a valid Resource PKI end-entity certificate whose
AS number resource extension includes the BGPSEC speaker's AS number AS number resource extension includes the BGPSEC speaker's AS number
[9]. Note also new signatures are only added to a BGPSEC update [11]. Note also that new signatures are only added to a BGPSEC
message when a BGPSEC speaker is generating an update message to send update message when a BGPSEC speaker is generating an update message
to an external peer (i.e., when the AS number of the peer is not to send to an external peer (i.e., when the AS number of the peer is
equal to the BGPSEC speaker's own AS number). Therefore, a BGPSEC not equal to the BGPSEC speaker's own AS number). Therefore, a
speaker who only sends BGPSEC update messages to peers within its own BGPSEC speaker who only sends BGPSEC update messages to peers within
AS, it does not need to possess any private signature keys. its own AS, it does not need to possess any private signature keys.
4.1. Originating a New BGPSEC Update 4.1. Originating a New BGPSEC Update
In an update message that originates a new route advertisement (i.e., In an update message that originates a new route advertisement (i.e.,
an update whose path will contain only a single AS number), the an update whose path will contain only a single AS number), when
BGPSEC speaker creates a new BGPSEC_Path_Signatures attribute as sending the route advertisement to an external, BGPSEC-speaking peer,
the BGPSEC speaker creates a new BGPSEC_Path_Signatures attribute as
follows. follows.
First, the BGPSEC speaker constructs the Secure_Path with a single First, the BGPSEC speaker constructs the Secure_Path with a single
Secure_Path Segment. The AS in this path is the BGPSEC speaker's own Secure_Path Segment. The AS in this path is the BGPSEC speaker's own
AS number. In particular, this AS number MUST match the AS number in AS number. In particular, this AS number MUST match the AS number in
the AS number resource extension field of the Resource PKI end-entity the AS number resource extension field of the Resource PKI end-entity
certificate(s) that will be used to verify the digital signature(s) certificate(s) that will be used to verify the digital signature(s)
constructed by this BGPSEC speaker. constructed by this BGPSEC speaker.
Note that the BGPSEC_Path_Signatures attribute and the AS4_Path Note that the BGPSEC_Path_Signatures attribute and the AS4_Path
attribute are mutually exclusive. That is, any update message attribute are mutually exclusive. That is, any update message
containing the BGPSEC_Path_Signatures attribute MUST NOT contain the containing the BGPSEC_Path_Signatures attribute MUST NOT contain the
AS4_Path attribute nor the AS_Path attribute. The information that AS4_Path attribute nor the AS_Path attribute. The information that
would be contained in the AS4_Path (or AS_Path) attribute is instead would be contained in the AS4_Path (or AS_Path) attribute is instead
conveyed in the Secure_Path portion of the BGPSEC_Path_Signatures conveyed in the Secure_Path portion of the BGPSEC_Path_Signatures
attribute. attribute.
Note that the Resource PKI enables the legitimate holder of IP Note that the Resource PKI enables the legitimate holder of IP
address prefix(es) to issue a signed object, called a Route address prefix(es) to issue a signed object, called a Route
Origination Authorization (ROA), that authorizes a given AS to Origination Authorization (ROA), that authorizes a given AS to
originate routes to a given set of prefixes (see [6]). Note that originate routes to a given set of prefixes (see [7]). Note that
validation of a BGPSEC update message will fail (i.e., the validation validation of a BGPSEC update message will fail (i.e., the validation
algorithm, specified in Section 5.1, returns 'Not Good') unless there algorithm, specified in Section 5.1, returns 'Not Good') unless there
exists a valid ROA authorizing the first AS in the Secure_Path exists a valid ROA authorizing the first AS in the Secure_Path
portion of the BGPSEC_Path_Signatures attribute to originate routes portion of the BGPSEC_Path_Signatures attribute to originate routes
to the prefix being advertised. Therefore, a BGPSEC speaker SHOULD to the prefix being advertised. Therefore, a BGPSEC speaker SHOULD
NOT originate a BGPSEC update advertising a route for a given prefix NOT originate a BGPSEC update advertising a route for a given prefix
unless there exists a valid ROA authorizing the BGPSEC speaker's AS unless there exists a valid ROA authorizing the BGPSEC speaker's AS
to originate routes to this prefix. to originate routes to this prefix.
The pCount field of the Secure_Path Segment is typically set to the The pCount field of the Secure_Path Segment is typically set to the
value 1. However, a BGPSEC speaker may set the pCount field to a value 1. However, a BGPSEC speaker may set the pCount field to a
value greater than 1. Setting the pCount field to a value greater value greater than 1. Setting the pCount field to a value greater
than one has the same semantics as repeating an AS number multiple than one has the same semantics as repeating an AS number multiple
times in the AS_PATH of a non-BGPSEC update message (e.g., for times in the AS_PATH of a non-BGPSEC update message (e.g., for
traffic engineering purposes). Setting the pCount field to a value traffic engineering purposes). Setting the pCount field to a value
greater than one permits this repetition without requiring a separate greater than one permits this repetition without requiring a separate
digital signature for each repetition. digital signature for each repetition.
The Flags field of the Secure_Path Segment MUST be set to zero. It If the BGPSEC speaker is not a member of an autonomous system
is anticipated that future specifications may instruct BGPSEC confederation [3], then the Flags field of the Secure_Path Segment
speakers to set the Flags field to values other than zero. MUST be set to zero. (Members of a confederation should follow the
Therefore, BGPSEC receivers compliant with this specification must be special processing instructions for confederation members in Section
able to accept values of the Flags field other than zero. Such 4.4.)
receivers will use the Flags field to verify digital signatures (see
Section 5) but will otherwise ignore non-zero values in the Flags
field.
The BGPSEC speaker next constructs the Additional_Info portion of the The BGPSEC speaker next constructs the Additional_Info portion of the
BGPSEC_Path_Signatures atttribute. The Info Type MUST be set to zero BGPSEC_Path_Signatures attribute. The Info Type MUST be set to zero
and the Info Length MUST also be set to zero. The Info Value field and the Info Length MUST also be set to zero. The Info Value field
is empty (has length zero). It is anticipated that future is empty (has length zero). It is anticipated that future
specifications may specify values of Info Type other than zero. specifications may specify values of Info Type other than zero.
Therefore, BGPSEC receivers compliant with this specification must be Therefore, BGPSEC receivers compliant with this specification must be
able to accept Additional_Info fields with non-zero Info Type. Such able to accept Additional_Info fields with non-zero Info Type. Such
receivers will use the Additional_Field to verify digital signatures receivers will use the Additional_Field to verify digital signatures
(see Section 5) but will otherwise ignore Additional_Field non-zero (see Section 5) but will otherwise ignore Additional_Field non-zero
Info Fields. Info Fields.
Typically, a BGPSEC speaker will use only a single algorithm suite, Typically, a BGPSEC speaker will use only a single algorithm suite,
skipping to change at page 16, line 8 skipping to change at page 16, line 7
o Apply to this digest value the signature algorithm, (for the o Apply to this digest value the signature algorithm, (for the
algorithm suite of this Signature_Block) to obtain the digital algorithm suite of this Signature_Block) to obtain the digital
signature. Then populate the Signature Field with this digital signature. Then populate the Signature Field with this digital
signature. signature.
The Signature Length field is populated with the length (in octets) The Signature Length field is populated with the length (in octets)
of the Signature field. of the Signature field.
4.2. Propagating a Route Advertisement 4.2. Propagating a Route Advertisement
EDITOR'S NOTE: There is a known issue in this section with regards to
confederations. BGPSEC update messages do not include the AS4_Path
or AS_Path attributes. Therefore, BGPSEC update messages can not use
AS_CONFED_SEQUENCE segments within AS4_Path (or AS_Path) to convey
confederation information (see RFC 5065). However, in this current
version of the BGPSEC specification there is no alternative mechanism
specified to convey confederation information. This needs to be
fixed in a future version of this document.
When a BGPSEC speaker receives a BGPSEC update message containing a When a BGPSEC speaker receives a BGPSEC update message containing a
BGPSEC_Path_Signatures attribute (with one or more signatures) from a BGPSEC_Path_Signatures attribute (with one or more signatures) from
(internal or external) peer, it may choose to propagate the route an (internal or external) peer, it may choose to propagate the route
advertisement by sending to its (internal or external) peers by advertisement by sending to its (internal or external) peers by
creating a new BGPSEC advertisement for the same prefix. creating a new BGPSEC advertisement for the same prefix.
If a BGPSEC router has received only non-BGPSEC update messages If a BGPSEC router has received only non-BGPSEC update messages
(without the BGPSEC_Path_Signatures attribute) from a peer for a (without the BGPSEC_Path_Signatures attribute), containing the
given prefix and if it chooses to propagate that peer's route for the AS_Path attribute, from a peer for a given prefix and if it chooses
prefix, then it MUST NOT attach any BGPSEC_Path_Signatures attribute to propagate that peer's route for the prefix, then it MUST NOT
to the corresponding update being propagated. attach any BGPSEC_Path_Signatures attribute to the corresponding
update being propagated. (Note that a BGPSEC router may also receive
a non-BGPSEC update message from an internal peer without the AS_Path
attribute, i.e., with just the NLRI in it. In that case, the prefix
is originating from that AS and hence the BGPSEC speaker SHOULD sign
and forward the update to its external peers, as specified in Section
4.1.)
Conversely, if a BGPSEC router has received a BGPSEC update message Conversely, if a BGPSEC router has received a BGPSEC update message
(with the BGPSEC_Path_Signatures attribute) from a peer for a given (with the BGPSEC_Path_Signatures attribute) from a peer for a given
prefix and it chooses to propagate that peer's route for the prefix, prefix and it chooses to propagate that peer's route for the prefix,
then it SHOULD propogate the route as a BGPSEC update message then it SHOULD propagate the route as a BGPSEC update message
containing the BGPSEC_Path_Signatures attribute. However, the BGPSEC containing the BGPSEC_Path_Signatures attribute. However, the BGPSEC
speaker MAY propogate the route as a (unsigned) BGP update message speaker MAY propagate the route as a (unsigned) BGP update message
without the BGPSEC_Path_Signatures attribute. without the BGPSEC_Path_Signatures attribute.
Note that removing BGPSEC signatures (i.e., propagating a route Note that removing BGPSEC signatures (i.e., propagating a route
advertisement without the BGPSEC_Path_Signatures attribute) has advertisement without the BGPSEC_Path_Signatures attribute) has
significant security ramifications. (See Section 7 for discussion of significant security ramifications. (See Section 7 for discussion of
the security ramifications of removing BGPSEC signatures.) the security ramifications of removing BGPSEC signatures.)
Therefore, when a route advertisement is received via a BGPSEC update Therefore, when a route advertisement is received via a BGPSEC update
message, propagating the route advertisement without the message, propagating the route advertisement without the
BGPSEC_Path_Signatures attribute is NOT RECOMMENDED. Furtherore, BGPSEC_Path_Signatures attribute is NOT RECOMMENDED. Furthermore,
note that when a BGPSEC speaker propagates a route advertisement with note that when a BGPSEC speaker propagates a route advertisement with
the BGPSEC_Path_Signatures attribute it is not attesting to the the BGPSEC_Path_Signatures attribute it is not attesting to the
validation state of the update message it received. (See Section 7 validation state of the update message it received. (See Section 7
for more discussion of the security semantics of BGPSEC signatures.) for more discussion of the security semantics of BGPSEC signatures.)
If the BGPSEC speaker is producing an update message which contains If the BGPSEC speaker is producing an update message which would, in
an AS_SET (e.g., the BGPSEC speaker is performing proxy aggregation), the absence of BGPSEC, contain an AS_SET (e.g., the BGPSEC speaker is
then the BGPSEC speaker MUST NOT include the BGPSEC_Path_Signatures performing proxy aggregation), then the BGPSEC speaker MUST NOT
attribute. In such a case, the BGPSEC speaker must remove any include the BGPSEC_Path_Signatures attribute. In such a case, the
existing BGPSEC_Path_Signatures in the received advertisement(s) for BGPSEC speaker must remove any existing BGPSEC_Path_Signatures in the
this prefix and produce a standard (non-BGPSEC) update message. received advertisement(s) for this prefix and produce a standard
(non-BGPSEC) update message. It should be noted that BCP 172 [5]
recommends against the use of AS_SET and AS_CONFED_SET in AS_PATH in
BGP updates.
To generate the BGPSEC_Path_Signatures attribute on the outgoing To generate the BGPSEC_Path_Signatures attribute on the outgoing
update message, the BGPSEC speaker first prepends a new Secure_Path update message, the BGPSEC speaker first prepends a new Secure_Path
Segment (places in first position) to the Secure_Path. The AS number Segment (places in first position) to the Secure_Path. The AS number
in this Secure_Path segment MUST match the AS number in the AS number in this Secure_Path segment MUST match the AS number in the AS number
resource extension field of the Resource PKI end-entity resource extension field of the Resource PKI end-entity
certificate(s) that will be used to verify the digital signature(s) certificate(s) that will be used to verify the digital signature(s)
constructed by this BGPSEC speaker. constructed by this BGPSEC speaker.
The pCount is typically set to the value 1. A BGPSEC speaker may set The pCount is typically set to the value 1. A BGPSEC speaker may set
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number into the Secure_Path segment, as this information is needed to number into the Secure_Path segment, as this information is needed to
validate the signature added by the route server. Note that the validate the signature added by the route server. Note that the
option of setting pCount to 0 is intended only for use by route option of setting pCount to 0 is intended only for use by route
servers that desire not to increase the effective AS-PATH length of servers that desire not to increase the effective AS-PATH length of
routes they advertise. The pCount field SHOULD NOT be set to 0 in routes they advertise. The pCount field SHOULD NOT be set to 0 in
other circumstances. BGPSEC speakers SHOULD drop incoming update other circumstances. BGPSEC speakers SHOULD drop incoming update
messages with pCount set to zero in cases where the BGPSEC speaker messages with pCount set to zero in cases where the BGPSEC speaker
does not expect its peer to set pCount to zero (i.e., cases where the does not expect its peer to set pCount to zero (i.e., cases where the
peer is not acting as a route server). peer is not acting as a route server).
The Flags field of the Secure_Path Segment MUST be set to zero. It If the BGPSEC speaker is not a member of an autonomous system
is anticipated that future specifications may instruct BGPSEC confederation [3], then the Flags field of the Secure_Path Segment
speakers to set the Flags field to values other than zero. MUST be set to zero. (Members of a confederation should follow the
Therefore, BGPSEC receivers compliant with this specification must be special processing instructions for confederation members in Section
able to accept values of the Flags field other than zero. Such 4.4.)
receivers will use the Flags field to verify digital signatures (see
Section 5) but will otherwise ignore non-zero values in the Flags
field.
The BGPSEC speaker next copies the Additional_Info portion of the The BGPSEC speaker next copies the Additional_Info portion of the
BGPSEC_Path_Signatures directly from the received update message to BGPSEC_Path_Signatures directly from the received update message to
the new update message (that it is constructing). Note that the the new update message (that it is constructing). Note that the
BGPSEC speaker MUST NOT change the Additional_Info as any change to BGPSEC speaker MUST NOT change the Additional_Info as any change to
Additional_Info will cause the new BGPSEC update message to fail Additional_Info will cause the new BGPSEC update message to fail
validation (see Section 5). validation (see Section 5).
If the received BGPSEC update message contains two Signature_ Blocks If the received BGPSEC update message contains two Signature_ Blocks
and the BGPSEC speaker supports both of the corresponding algorithms and the BGPSEC speaker supports both of the corresponding algorithms
suites, then the new update message generated by the BGPSEC speaker suites, then the new update message generated by the BGPSEC speaker
SHOULD include both of the Signature_Blocks. If the received BGPSEC SHOULD include both of the Signature_Blocks. If the received BGPSEC
update message contains two Signature_Blocks and the BGPSEC speaker update message contains two Signature_Blocks and the BGPSEC speaker
only supports one of the two corresponding algorithm suites, then the only supports one of the two corresponding algorithm suites, then the
BGPSEC speaker MUST remove the Signature_Block corresponding to the BGPSEC speaker MUST remove the Signature_Block corresponding to the
algorithm suite that it does not understand. If the BGPSEC speaker algorithm suite that it does not understand. If the BGPSEC speaker
does not support the algorithm suites in any of the Signature_Blocks does not support the algorithm suites in any of the Signature_Blocks
contained in the received update message, then the BGPSEC speaker contained in the received update message, then the BGPSEC speaker
MUST NOT propagate the route advertisement with the MUST NOT propagate the route advertisement with the
BGPSEC_Path_Signatures attribute (as an unsigned BGP update message). BGPSEC_Path_Signatures attribute (i.e., propagate it as an unsigned
BGP update message).
Note that in the case where there are two Signature_Blocks Note that in the case where there are two Signature_Blocks
(corresponding to different algorithm suites) that the validation (corresponding to different algorithm suites) that the validation
algorithm (see Section 5.1) deems a BGPSEC update message to be algorithm (see Section 5.1) deems a BGPSEC update message to be
'Good' if there is at least one supported algorithm suite (and 'Good' if there is at least one supported algorithm suite (and
corresponding Signature_Block) that is deemed 'Good'. This means corresponding Signature_Block) that is deemed 'Good'. This means
that a 'Good' BGPSEC update message may contain a Signature_Block that a 'Good' BGPSEC update message may contain a Signature_Block
which is not deemed 'Good' (e.g., contains signatures that the BGPSEC which is not deemed 'Good' (e.g., contains signatures that the BGPSEC
does not sucessfully verify). Nonetheless, such Signature_Blocks does not successfully verify). Nonetheless, such Signature_Blocks
MUST NOT be removed. (See Section 7 for a discussion of the security MUST NOT be removed. (See Section 7 for a discussion of the security
ramifications of this design choice.) ramifications of this design choice.)
For each Signature_Block corresponding to an algorithm suite that the For each Signature_Block corresponding to an algorithm suite that the
BGPSEC speaker does support, the BGPSEC speaker then adds a new BGPSEC speaker does support, the BGPSEC speaker then adds a new
Signature Segment to the Signature_Block. This Signature Segment is Signature Segment to the Signature_Block. This Signature Segment is
prepended to the list of Signature Segments (placed in the first prepended to the list of Signature Segments (placed in the first
position) so that the list of Signature Segments appears in the same position) so that the list of Signature Segments appears in the same
order as the corresponding Secure_Path segments numbers in the order as the corresponding Secure_Path segments in the Secure_Path
Secure_Path portion of the BGPSEC_Path_Signatures attribute. The portion of the BGPSEC_Path_Signatures attribute. The BGPSEC speaker
BGPSEC speaker populates the fields of this new signature segment as populates the fields of this new signature segment as follows.
follows.
The Subject Key Identifier field in the new segment is populated with The Subject Key Identifier field in the new segment is populated with
the identifier contained in the Subject Key Identifier extension of the identifier contained in the Subject Key Identifier extension of
the RPKI end-entity certificate used by the BGPSEC speaker. This the RPKI end-entity certificate used by the BGPSEC speaker. This
Subject Key Identifier will be used by recipients of the route Subject Key Identifier will be used by recipients of the route
advertisement to identify the proper certificate to use in verifying advertisement to identify the proper certificate to use in verifying
the signature. the signature.
The Signature field in the new segment contains a digital signature The Signature field in the new segment contains a digital signature
that binds the NLRI and BGPSEC_Path_Signatures attribute to the RPKI that binds the NLRI and BGPSEC_Path_Signatures attribute to the RPKI
end-entity certificate used by the BGPSEC speaker. The digital end-entity certificate used by the BGPSEC speaker. The digital
signature is computed as follows: signature is computed as follows:
o Construct a sequence of octets by concatenating the Target AS o Construct a sequence of octets by concatenating the Target AS
number, the Secure_Path segment is being added by the BGPSEC number, the Secure_Path segment that is being added by the BGPSEC
speaker constructing the signature, and the signature field of the speaker constructing the signature, and the signature field of the
most recent Signature Segment (the one corresponding to AS from most recent Signature Segment (the one corresponding to AS from
whom the BGPSEC speaker's AS received the announcement). Note whom the BGPSEC speaker's AS received the announcement). Note
that the Target AS number is the AS number announced by the peer that the Target AS number is the AS number announced by the peer
in the OPEN message of the BGP session within which the BGPSEC in the OPEN message of the BGP session within which the BGPSEC
update message is sent. update message is sent.
Sequence of Octets to be Signed Sequence of Octets to be Signed
+--------------------------------------+ +--------------------------------------+
| Target AS Number (4 octets) | | Target AS Number (4 octets) |
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algorithm suite of this Signature_Block) to obtain a digest value. algorithm suite of this Signature_Block) to obtain a digest value.
o Apply to this digest value the signature algorithm, (for the o Apply to this digest value the signature algorithm, (for the
algorithm suite of this Signature_Block) to obtain the digital algorithm suite of this Signature_Block) to obtain the digital
signature. Then populate the Signature Field with this digital signature. Then populate the Signature Field with this digital
signature. signature.
The Signature Length field is populated with the length (in octets) The Signature Length field is populated with the length (in octets)
of the Signature field. of the Signature field.
4.3. Reconstructing the AS_Path Attribute
EDITOR'S NOTE: This is a place-holder section. Given that BGPSEC
update messages do not contain the AS_Path attribute, this document
needs to include a clearly specified algorithm for reconstructing the
AS_Path attribute from the data in the BGPSEC_Path_Signatures
attribute. (For example, when propagating a path received via BGPSEC
to a non-BGPSEC peer.) This algorithm for reconstructing the AS_Path
will appear in the next version of this document. In essence, the
algorithm is: For each Secure_Path Segment put into the AS_Path
pCount copies of the AS number field of the segment --- and if you
see the Entering_Confed flag is set to one, then add an
AS_Confed_Sequence to the AS_Path.
4.4. Processing Instructions for Confederation Members
Members of autonomous system confederations [3] must additionally
follow the instructions in this section for processing BGPSEC update
messages.
When a confederation member sends a BGPSEC update message to a peer
who is a member of the same confederation, the confederation member
puts its (private) Member-AS Number (as opposed to the public AS
Confederation Identifier) in the AS Number field of the Secure_Path
Segment that it adds to the BGPSEC update message.
Furthermore, when sending a BGPSEC update message to a peer who is a
member of the same confederation, the first confederation member to
add a Secure_Path Segment to a BGPSEC update message sets the
Entering_Cofed flag in the Flags field to be one in the Secure_Path
Segment that it produces. In the case where the route advertisement
originates within a confederation, the member AS that originates the
route and sends it to a peer is the member AS that sets its
Entering_Confed flag to one. In the case where the route
advertisement is received from outside the confederation, it is the
member AS that receives the route advertisement from a peer outside
the confederation and propagates it to a peer inside the
confederation that sets its Entering_Confed flag to one. Note that
this is the same of the confederation member who would have added a
new AS_Path segment of type AS_Confed_Sequence to the AS_Path
attribute in a non-BGPSEC update message.
When a confederation member receives a BGPSEC update message from a
peer within the confederation and propagates it to a peer outside the
confederation, it must remove all of the Secure_Path Segments added
by confederation members as well as the corresponding Signature
Segments. To do this, the confederation member propagating the route
outside the confederation does the following:
o First, search through the Secure_Path, going from most recently
added segment to least recently added segment, and find first
Secure_Path Segment with the Entering_Confed flag to set to one.
(That is, of all the Secure_Path Segments with the Entering_Confed
flag set to one, find the one that was most recently added.)
o Second, remove the Secure_Path Segment found in previous step
along with all more recently added Secure_Path Segments. Keep a
count of the number of segments removed in this fashion.
o Third, starting with the most recently added Signature Segment,
remove a number of Signature Segments equal to the number of
Secure_Path Segments removed in the previous step. (That is,
remove the K most recently added signature segments, where K is
the number of Secure_Path Segments removed in the previous step.)
o Finally, add a Secure_Path Segment containing, in the AS field,
the AS Confederation Identifier (the public AS number of the
confederation) as well as a corresponding Signature Segment. Note
that all fields other that the AS field are populated as per
Sections 4.1 and 4.2.
When validating a received BGPSEC update message, confederation
members must make the following adjustment to the algorithm presented
in Section 5.1. That is, when a confederation member is processing
(validating) a Signature Segment and its corresponding Secure_Path
Segment, the confederation member must note that when a signature is
produced by a BGPSEC speaker outside of a confederation, the Target
AS will always be the AS Confederation Identifier (the public AS
number of the confederation) as opposed to the Member-AS Number. To
handle this case, when processing a current Secure_Path Segment, if
the next most recently added Secure_Path segment has the
Entering_Confed flag set then ,when computing the digest for the
current Secure_Path segment, take the Target AS Number to be the AS
Confederation Identifier of the validating BGPSEC speaker's own
confederation. (Note that the algorithm in Section 5.1 processes
Secure_Path Segments in order from most recently added to least
recently added, therefore the algorithm encounters the
Entering_Confed flag immediately before it encounters the Secure_Path
segment that requires using the AS Confederation Identifier to
validate.)
5. Processing a Received BGPSEC Update 5. Processing a Received BGPSEC Update
Validation of a BGPSEC update messages makes use of data from RPKI Validation of a BGPSEC update messages makes use of data from RPKI
certificates and signed Route Origination Authorizations (ROA). In certificates and signed Route Origination Authorizations (ROA). In
particular, to validate update messages containing the particular, to validate update messages containing the
BGPSEC_Path_Signatures attribute, it is necessary that the recipient BGPSEC_Path_Signatures attribute, it is necessary that the recipient
have access to the following data obtained from valid RPKI have access to the following data obtained from valid RPKI
certificates and ROAs: certificates and ROAs:
o For each valid RPKI end-entity certificate containing an AS Number o For each valid RPKI end-entity certificate containing an AS Number
extension, the AS Number, Public Key and Subject Key Identifier extension, the AS Number, Public Key and Subject Key Identifier
are required are required,
o For each valid ROA, the AS Number and the list of IP address o For each valid ROA, the AS Number and the list of IP address
prefixes prefixes.
Note that the BGPSEC speaker could perform the validation of RPKI Note that the BGPSEC speaker could perform the validation of RPKI
certificates and ROAs on its own and extract the required data, or it certificates and ROAs on its own and extract the required data, or it
could receive the same data from a trusted cache that performs RPKI could receive the same data from a trusted cache that performs RPKI
validation on behalf of (some set of) BGPSEC speakers. (The latter validation on behalf of (some set of) BGPSEC speakers. (The latter
case in analogous to the use of the RPKI-RTR protocol [11] for origin case in analogous to the use of the RPKI-RTR protocol [13] for origin
validation.) validation.)
To validate a BGPSEC update message containing the To validate a BGPSEC update message containing the
BGPSEC_Path_Signatures attribute, the recipient performs the BGPSEC_Path_Signatures attribute, the recipient performs the
validation steps specified in Section 5.1. The validation procedure validation steps specified in Section 5.1. The validation procedure
results in one of two states: 'Good' and 'Not Good'. results in one of two states: 'Good' and 'Not Good'.
It is expected that the output of the validation procedure will be It is expected that the output of the validation procedure will be
used as an input to BGP route selection. However, BGP route used as an input to BGP route selection. However, BGP route
selection and thus the handling of the two validation states is a selection and thus the handling of the two validation states is a
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Upon receiving a BGPSEC update message, a BGPSEC speaker SHOULD sum Upon receiving a BGPSEC update message, a BGPSEC speaker SHOULD sum
the pCount values within BGPSEC_Path_Signatures attribute to the pCount values within BGPSEC_Path_Signatures attribute to
determine the effective length of the AS Path. The BGPSEC speaker determine the effective length of the AS Path. The BGPSEC speaker
SHOULD use this sum of pCount values in precisely the same way as it SHOULD use this sum of pCount values in precisely the same way as it
uses the length of the AS Path in non-BGPSEC update messages. uses the length of the AS Path in non-BGPSEC update messages.
5.1. Validation Algorithm 5.1. Validation Algorithm
This section specifies an algorithm for validation of BGPSEC update This section specifies an algorithm for validation of BGPSEC update
messages. A conformant implementation MUST include an BGPSEC update messages. A conformant implementation MUST include a BGPSEC update
validation algorithm that is functionally equivalent to the external validation algorithm that is functionally equivalent to the external
behavior of this algorithm. behavior of this algorithm.
First, the recipient of a BGPSEC update message performs a check to First, the recipient of a BGPSEC update message performs a check to
ensure that the message is properly formed. Specifically, the ensure that the message is properly formed. Specifically, the
recipient performs the following checks: recipient performs the following checks:
o Check to ensure that the entire BGPSEC_Path_Signatures attribute o Check to ensure that the entire BGPSEC_Path_Signatures attribute
is syntactically correct (conforms to the specification in this is syntactically correct (conforms to the specification in this
document). document).
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recently added segment). Note that there is a one-to-one recently added segment). Note that there is a one-to-one
correspondence between Signature segments and Secure_Path segments correspondence between Signature segments and Secure_Path segments
within the BGPSEC_Path_Signatures attribute. The following steps within the BGPSEC_Path_Signatures attribute. The following steps
make use of this correspondence. make use of this correspondence.
o (Step I): Locate the public key needed to verify the signature (in o (Step I): Locate the public key needed to verify the signature (in
the current Signature segment). To do this, consult the valid the current Signature segment). To do this, consult the valid
RPKI end-entity certificate data and look up all valid (AS, SKI, RPKI end-entity certificate data and look up all valid (AS, SKI,
Public Key) triples in which the AS matches the AS number in the Public Key) triples in which the AS matches the AS number in the
corresponding Secure_Path segment. Of these triples that match corresponding Secure_Path segment. Of these triples that match
the AS number, check whether where is an SKI that matches the the AS number, check whether there is an SKI that matches the
value in the Subject Key Identifier field of the Signature value in the Subject Key Identifier field of the Signature
segment. If no such SKI value is found in the valid RPKI data segment. If this check finds no such matching SKI value, then
then mark the entire Signature-List Block as 'Not Good' and mark the entire Signature-List Block as 'Not Good' and proceed to
proceed to the next Signature-List Block. the next Signature-List Block.
o (Step II): Compute the digest function (for the given algorithm o (Step II): Compute the digest function (for the given algorithm
suite) on the appropriate data. If the segment is not the (least suite) on the appropriate data. If the segment is not the (least
recently added) segment corresponding to the origin AS, then the recently added) segment corresponding to the origin AS, then the
digest function should be computed on the following sequence of digest function should be computed on the following sequence of
octets: octets:
Sequence of Octets to be Hashed Sequence of Octets to be Hashed
+-------------------------------------------+ +-------------------------------------------+
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+-------------- ----------------------------+ +-------------- ----------------------------+
For the first segment to be processed (the most recently added For the first segment to be processed (the most recently added
segment), the 'AS Number of Target AS' is the AS number of the BGPSEC segment), the 'AS Number of Target AS' is the AS number of the BGPSEC
speaker validating the update message. Note that if a BGPSEC speaker speaker validating the update message. Note that if a BGPSEC speaker
uses multiple AS Numbers (e.g., the BGPSEC speaker is a member of a uses multiple AS Numbers (e.g., the BGPSEC speaker is a member of a
confederation), the AS number used here MUST be the AS number confederation), the AS number used here MUST be the AS number
announced in the OPEN message for the BGP session over which the announced in the OPEN message for the BGP session over which the
BGPSEC update was received. BGPSEC update was received.
For each other Signature-Segment, the 'AS Number of Target AS' is the For each other Signature Segment, the 'AS Number of Target AS' is the
AS number in the Secure_Path segment that corresponds to the AS number in the Secure_Path segment that corresponds to the
Signature segment added immediately after the one being processed. Signature Segment added immediately after the one being processed.
(That is, in the Secure_Path segment that corresponds to the (That is, in the Secure_Path segment that corresponds to the
Signature segment that the validator just finished processing.) Signature segment that the validator just finished processing.)
The AS Number, pCount and Flags fields are taken from the Secure_Path The AS Number, pCount and Flags fields are taken from the Secure_Path
segment that corresponds to the Signature segment currently being segment that corresponds to the Signature segment currently being
processed. The 'Signature Field in the Next Segment' is the processed. The 'Signature Field in the Next Segment' is the
Signature field found in the Signature segment that is next to be Signature field found in the Signature segment that is next to be
processed (that is, the next most recently added Signature segment). processed (that is, the next most recently added Signature Segment).
Alternatively, if the segment being processed corresponds to the Alternatively, if the segment being processed corresponds to the
origin AS (i.e., if it is the least recently added segment), then the origin AS (i.e., if it is the least recently added segment), then the
digest function should be computed on the following sequence of digest function should be computed on the following sequence of
octets: octets:
Sequence of Octets to be Hashed Sequence of Octets to be Hashed
+------------------------------------+ +------------------------------------+
| AS Number of Target AS (4 octets) | | AS Number of Target AS (4 octets) |
+------------------------------------+ +------------------------------------+
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| NLRI Length (1 octet) | | NLRI Length (1 octet) |
+------------------------------------+ +------------------------------------+
| NLRI Prefix (variable) | | NLRI Prefix (variable) |
+------------------------------------+ +------------------------------------+
The NLRI Length, NLRI Prefix, Additional_Info, and Algorithm Suite The NLRI Length, NLRI Prefix, Additional_Info, and Algorithm Suite
Identifier are all obtained in a straight forward manner from the Identifier are all obtained in a straight forward manner from the
NLRI of the update message or the BGPSEC_Path_Signatures attribute NLRI of the update message or the BGPSEC_Path_Signatures attribute
being validated. The Origin AS Number, pCount, and Flags fields are being validated. The Origin AS Number, pCount, and Flags fields are
taken from the Secure_Path segment corresponding to the Signature taken from the Secure_Path segment corresponding to the Signature
segment currently being processed. Segment currently being processed.
The 'AS Number of Target AS' is the AS Number from the Secure_Path The 'AS Number of Target AS' is the AS Number from the Secure_Path
segment that was added immediately after the Secure_Path segment segment that was added immediately after the Secure_Path segment
containing the Origin AS Number. (That is, the Secure_Path segment containing the Origin AS Number. (That is, the Secure_Path segment
corresponding to the Signature segment that the receiver just corresponding to the Signature segment that the receiver just
finished processing prior to the current Signature segment.) finished processing prior to the current Signature segment.)
o (Step III): Use the signature validation algorithm (for the given o (Step III): Use the signature validation algorithm (for the given
algorithm suite) to verify the signature in the current segment. algorithm suite) to verify the signature in the current segment.
That is, invoke the signature validation algorithm on the That is, invoke the signature validation algorithm on the
following three inputs: the value of the Signature field in the following three inputs: the value of the Signature field in the
current segment; the digest value computed in Step II above; and current segment; the digest value computed in Step II above; and
the public key obtained from the valid RPKI data in Step I above. the public key obtained from the valid RPKI data in Step I above.
If the signature validation algorithm determines that the If the signature validation algorithm determines that the
signature is invalid, then mark the entire Signature-List Block as signature is invalid, then mark the entire Signature-List Block as
'Not Good' and proceed to the next Signature_Block. If the 'Not Good' and proceed to the next Signature_Block. If the
signature validation algorithm determines that the signature is signature validation algorithm determines that the signature is
skipping to change at page 25, line 7 skipping to change at page 26, line 45
algorithm suite using BGP capabilities. This is because the algorithm suite using BGP capabilities. This is because the
algorithm suite used by the sender of a BGPSEC update message must be algorithm suite used by the sender of a BGPSEC update message must be
understood not only by the peer to whom he is directly sending the understood not only by the peer to whom he is directly sending the
message, but also by all BGPSEC speakers to whom the route message, but also by all BGPSEC speakers to whom the route
advertisement is eventually propagated. Therefore, selection of an advertisement is eventually propagated. Therefore, selection of an
algorithm suite cannot be a local matter negotiated by BGP peers, but algorithm suite cannot be a local matter negotiated by BGP peers, but
instead must be coordinated throughout the Internet. instead must be coordinated throughout the Internet.
To this end, a mandatory algorithm suites document will be created To this end, a mandatory algorithm suites document will be created
which specifies a mandatory-to-use 'current' algorithm suite for use which specifies a mandatory-to-use 'current' algorithm suite for use
by all BGPSEC speakers. Additionally, the document specifies an by all BGPSEC speakers [12]. Additionally, the document specifies an
additional 'new' algorithm suite that is recommended to implement. additional 'new' algorithm suite that is recommended to implement.
It is anticipated that in the future the mandatory algorithm suites It is anticipated that in the future the mandatory algorithm suites
document will be updated to specify a transition from the 'current' document will be updated to specify a transition from the 'current'
algorithm suite to the 'new' algorithm suite. During the period of algorithm suite to the 'new' algorithm suite. During the period of
transition (likely a small number of years), all BGPSEC update transition (likely a small number of years), all BGPSEC update
messages SHOULD simultaneously use both the 'current' algorithm suite messages SHOULD simultaneously use both the 'current' algorithm suite
and the 'new' algorithm suite. (Note that Sections 3 and 4 specify and the 'new' algorithm suite. (Note that Sections 3 and 4 specify
how the BGPSEC_Path_Signatures attribute can contain signatures, in how the BGPSEC_Path_Signatures attribute can contain signatures, in
parallel, for two algorithm suites.) Once the transition is parallel, for two algorithm suites.) Once the transition is
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BGPSEC_PATH_SIGNATURES attribute and the new BGPSEC_PATH_SIG_TWO BGPSEC_PATH_SIGNATURES attribute and the new BGPSEC_PATH_SIG_TWO
attribute. Once the transition is complete, the use of attribute. Once the transition is complete, the use of
BGPSEC_PATH_SIGNATURES could then be deprecated, at which point BGPSEC_PATH_SIGNATURES could then be deprecated, at which point
BGPSEC speakers SHOULD include only the new BGPSEC_PATH_SIG_TWO BGPSEC speakers SHOULD include only the new BGPSEC_PATH_SIG_TWO
attribute. Such a process could facilitate a transition to a new attribute. Such a process could facilitate a transition to a new
BGPSEC semantics in a backwards compatible fashion. BGPSEC semantics in a backwards compatible fashion.
7. Security Considerations 7. Security Considerations
For discussion of the BGPSEC threat model and related security For discussion of the BGPSEC threat model and related security
considerations, please see [8]. considerations, please see [10].
A BGPSEC speaker who receives a valid BGPSEC update message, A BGPSEC speaker who receives a valid BGPSEC update message,
containing a route advertisement for a given prefix, is provided with containing a route advertisement for a given prefix, is provided with
the following security guarantees: the following security guarantees:
o The origin AS number corresponds to an autonomous system that has o The origin AS number corresponds to an autonomous system that has
been authorized by the IP address space holder to originate route been authorized by the IP address space holder to originate route
advertisements for the given prefix. advertisements for the given prefix.
o For each AS number in the AS Path, a BGPSEC speaker authorized by o For each AS number in the AS Path, a BGPSEC speaker authorized by
the holder of the AS number intentionally chose (in aacordance the holder of the AS number intentionally chose (in accordance
with local policy) to propagate the route advertisement to the with local policy) to propagate the route advertisement to the
next AS in the Secure_Path. next AS in the Secure_Path.
That is, the recipient of a valid BGPSEC Update message is assured That is, the recipient of a valid BGPSEC Update message is assured
that the Secure_Path corresponds to a sequence of autonomous systems that the Secure_Path corresponds to a sequence of autonomous systems
who have all agreed in principle to forward packets to the given who have all agreed in principle to forward packets to the given
prefix along the indicated path. (It should be noted BGPSEC does not prefix along the indicated path. (It should be noted that BGPSEC
offer a precise guarantee that the data packets would propagate along does not offer a precise guarantee that the data packets would
the indicated path; it only guarantees that the BGP update conveying propagate along the indicated path; it only guarantees that the BGP
the path indeed propagated along the indicated path.) Furthermore, update conveying the path indeed propagated along the indicated
the recipient is assured that this path terminates in an autonomous path.) Furthermore, the recipient is assured that this path
system that has been authorized by the IP address space holder as a terminates in an autonomous system that has been authorized by the IP
legitimate destination for traffic to the given prefix. address space holder as a legitimate destination for traffic to the
given prefix.
Note that although BGPSEC provides a mechanism for an AS to validate Note that although BGPSEC provides a mechanism for an AS to validate
that a received update message has certain security properties, the that a received update message has certain security properties, the
use of such a mechanism to influence route selection is completely a use of such a mechanism to influence route selection is completely a
matter of local policy. Therefore, a BGPSEC speaker can make no matter of local policy. Therefore, a BGPSEC speaker can make no
assumptions about the validity of a route received from an external assumptions about the validity of a route received from an external
BGPSEC peer. That is, a compliant BGPSEC peer may (depending on the BGPSEC peer. That is, a compliant BGPSEC peer may (depending on the
local policy of the peer) send update messages that fail the validity local policy of the peer) send update messages that fail the validity
test in Section 5. Thus, a BGPSEC speaker MUST completely validate test in Section 5. Thus, a BGPSEC speaker MUST completely validate
all BGPSEC update messages received from external peers. (Validation all BGPSEC update messages received from external peers. (Validation
skipping to change at page 28, line 29 skipping to change at page 30, line 23
o The BGPSEC speaker received the given route advertisement with the o The BGPSEC speaker received the given route advertisement with the
indicated NLRI and Secure_Path; and indicated NLRI and Secure_Path; and
o The BGPSEC speaker chose to propagate an advertisement for this o The BGPSEC speaker chose to propagate an advertisement for this
route to the peer (implicitly) indicated by the 'Target AS' route to the peer (implicitly) indicated by the 'Target AS'
The BGPSEC update validation procedure is a potential target for The BGPSEC update validation procedure is a potential target for
denial of service attacks against a BGPSEC speaker. To mitigate the denial of service attacks against a BGPSEC speaker. To mitigate the
effectiveness of such denial of service attacks, BGPSEC speakers effectiveness of such denial of service attacks, BGPSEC speakers
should implement an update validation algorithm that performs should implement an update validation algorithm that performs
expensive checks (e.g., signature verification) after less expensive expensive checks (e.g., signature verification) after performing less
checks (e.g., syntax checks). The validation algorithm specified in expensive checks (e.g., syntax checks). The validation algorithm
Section 5.1 was chosen so as to perform checks which are likely to be specified in Section 5.1 was chosen so as to perform checks which are
expensive after checks that are likely to be inexpensive. However, likely to be expensive after checks that are likely to be
the relative cost of performing required validation steps may vary inexpensive. However, the relative cost of performing required
between implementations, and thus the algorithm specified in Section validation steps may vary between implementations, and thus the
5.1 may not provide the best denial of service protection for all algorithm specified in Section 5.1 may not provide the best denial of
implementations. service protection for all implementations.
The mechanism of setting the pCount field to zero is included in this The mechanism of setting the pCount field to zero is included in this
specification to enable route servers in the control path to specification to enable route servers in the control path to
participate in BGPSEC without increasing the effective length of the participate in BGPSEC without increasing the effective length of the
AS-PATH. However, entities other than route servers could AS-PATH. However, entities other than route servers could
conceivably use this mechanism (set the pCount to zero) to attract conceivably use this mechanism (set the pCount to zero) to attract
traffic (by reducing the effective length of the AS-PATH) traffic (by reducing the effective length of the AS-PATH)
illegitimately. This risk is largely mitigated if every BGPSEC illegitimately. This risk is largely mitigated if every BGPSEC
speaker drops incoming update messages that set pCount to zero but speaker drops incoming update messages that set pCount to zero but
come from a peer that is not a route server. However, note that a come from a peer that is not a route server. However, note that a
skipping to change at page 30, line 36 skipping to change at page 32, line 31
valuable input and review. valuable input and review.
9. Normative References 9. Normative References
[1] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border [1] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
Gateway Protocol 4", RFC 4271, January 2006. Gateway Protocol 4", RFC 4271, January 2006.
[2] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, [2] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January 2007. "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007.
[3] Scudder, J. and R. Chandra, "Capabilities Advertisement with [3] Traina, P., McPherson, D., and J. Scudder, "Autonomous System
Confederations for BGP", RFC 5065, August 2007.
[4] Scudder, J. and R. Chandra, "Capabilities Advertisement with
BGP-4", RFC 5492, February 2009. BGP-4", RFC 5492, February 2009.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement [5] Kumari, W. and K. Sriram, "Recommendation for Not Using AS_SET
Levels", BCP 14, RFC 2119, March 1997. and AS_CONFED_SET in BGP", RFC 6472, December 2011.
[5] Patel, K., Ward, D., and R. Bush, "Extended Message support for [6] Lepinski, M. and S. Kent, "Recommendation for Not Using AS_SET
BGP", March 2011. and AS_CONFED_SET in BGP", RFC 6480, February 2012.
[6] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route [7] Lepinski, M., Kent, S., and D. Kong, "Recommendation for Not
Origin Authorizations", February 2011. Using AS_SET and AS_CONFED_SET in BGP", RFC 6482,
February 2012.
[7] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure [8] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Internet Routing", February 2011. Levels", BCP 14, RFC 2119, March 1997.
[8] Kent, S., "Threat Model for BGP Path Security", June 2011. [9] Patel, K., Ward, D., and R. Bush, "Extended Message support for
BGP", March 2011.
[9] Reynolds, M., Turner, S., and S. Kent, "A Profile for BGPSEC [10] Kent, S., "Threat Model for BGP Path Security", February 2012.
[11] Reynolds, M., Turner, S., and S. Kent, "A Profile for BGPSEC
Router Certificates, Certificate Revocation Lists, and Router Certificates, Certificate Revocation Lists, and
Certification Requests", December 2011. Certification Requests", December 2011.
[10] Turner, S., "BGP Algorithms, Key Formats, & Signature Formats", [12] Turner, S., "BGP Algorithms, Key Formats, & Signature Formats",
December 2011. March 2012.
[11] Bush, R. and R. Austein, "The RPKI/Router Protocol", [13] Bush, R. and R. Austein, "The RPKI/Router Protocol",
October 2011. February 2012.
Author's Address Author's Address
Matthew Lepinski (editor) Matthew Lepinski (editor)
BBN BBN
10 Moulton St 10 Moulton St
Cambridge, MA 55409 Cambridge, MA 55409
US US
Phone: +1 617 873 5939 Phone: +1 617 873 5939
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