draft-ietf-sidr-bgpsec-protocol-05.txt   draft-ietf-sidr-bgpsec-protocol-06.txt 
Network Working Group M. Lepinski, Ed. Network Working Group M. Lepinski, Ed.
Internet-Draft BBN Internet-Draft BBN
Intended status: Standards Track September 7, 2012 Intended status: Standards Track October 22, 2012
Expires: March 11, 2013 Expires: April 25, 2013
BGPSEC Protocol Specification BGPSEC Protocol Specification
draft-ietf-sidr-bgpsec-protocol-05 draft-ietf-sidr-bgpsec-protocol-06
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 path of autonomous
BGP update messages. BGPSEC is implemented via a new optional non- systems through which a BGP update message passes. BGPSEC is
transitive BGP path attribute that carries a digital signature implemented via a new optional non-transitive BGP path attribute that
produced by each autonomous system on the AS-PATH. carries a digital signature produced by each autonomous system that
propagates the update message.
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", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in RFC 2119 [8]. "OPTIONAL" are to be interpreted as described in RFC 2119 [1] only
when they appear in all upper case. They may also appear in lower or
mixed case as English words, without normative meaning
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
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on March 11, 2013. This Internet-Draft will expire on April 25, 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.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BGPSEC Negotiation . . . . . . . . . . . . . . . . . . . . . . 3 2. BGPSEC Negotiation . . . . . . . . . . . . . . . . . . . . . . 3
3. The BGPSEC_Path_Signatures Attribute . . . . . . . . . . . . . 6 2.1. BGPSEC Send Capability . . . . . . . . . . . . . . . . . . 3
2.2. BGPSEC Receive Capability . . . . . . . . . . . . . . . . 4
2.3. Negotiating BGPSEC Support . . . . . . . . . . . . . . . . 5
3. The BGPSEC_Path Attribute . . . . . . . . . . . . . . . . . . 6
3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Additional_Info . . . . . . . . . . . . . . . . . . . . . 10 3.2. Signature_Block . . . . . . . . . . . . . . . . . . . . . 9
3.3. Signature_Block . . . . . . . . . . . . . . . . . . . . . 11 4. Generating a BGPSEC Update . . . . . . . . . . . . . . . . . . 11
4. Generating a BGPSEC Update . . . . . . . . . . . . . . . . . . 12 4.1. Originating a New BGPSEC Update . . . . . . . . . . . . . 12
4.1. Originating a New BGPSEC Update . . . . . . . . . . . . . 13 4.2. Propagating a Route Advertisement . . . . . . . . . . . . 14
4.2. Propagating a Route Advertisement . . . . . . . . . . . . 16 4.3. Processing Instructions for Confederation Members . . . . 18
4.3. Processing Instructions for Confederation Members . . . . 20 4.4. Reconstructing the AS_PATH Attribute . . . . . . . . . . . 20
4.4. Reconstructing the AS_PATH Attribute . . . . . . . . . . . 22 5. Processing a Received BGPSEC Update . . . . . . . . . . . . . 21
5. Processing a Received BGPSEC Update . . . . . . . . . . . . . 23 5.1. Overview of BGPSEC Validation . . . . . . . . . . . . . . 23
5.1. Overview of BGPSEC Validation . . . . . . . . . . . . . . 25 5.2. Validation Algorithm . . . . . . . . . . . . . . . . . . . 24
5.2. Validation Algorithm . . . . . . . . . . . . . . . . . . . 26 6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 28
6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 30 6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 28
6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 30 6.2. Extensibility Considerations . . . . . . . . . . . . . . . 28
6.2. Extensibility Considerations . . . . . . . . . . . . . . . 31 7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
7. Security Considerations . . . . . . . . . . . . . . . . . . . 31 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 35 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 35 9.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 36 9.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 34
9. Normative References . . . . . . . . . . . . . . . . . . . . . 36 10. Normative References . . . . . . . . . . . . . . . . . . . . . 34
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 37 11. Informative References . . . . . . . . . . . . . . . . . . . . 35
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 35
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) [2] 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
authorized by the holder of the IP address prefix to originate authorized by the holder of the IP address prefix to originate
route advertisements for that prefix. route advertisements for that prefix.
2. Every AS listed in the AS_Path attribute of the update explicitly 2. Every AS on the path of ASes through which the update message
authorized the advertisement of the route to the subsequent AS in passes has explicitly authorized the advertisement of the route
the AS_Path. to the subsequent AS in the 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. It also describes how a BGPSEC-compliant BGP
compliant BGP speaker (referred to hereafter as a BGPSEC speaker) can speaker (referred to hereafter as a BGPSEC speaker) can generate,
generate, propagate, and validate BGP update messages containing this propagate, and validate BGP update messages containing this attribute
attribute to obtain the above assurances. 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 [6] and address resources. (For more information on the RPKI, see [7] 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 needs to have the private key associated with an RPKI
well as the associated private signing key) corresponding to the router certificate [10] that corresponds to the BGPSEC speaker's AS
BGPSEC speaker's AS number. Note, however, that a BGPSEC speaker number. Note, however, that a BGPSEC speaker does not need such a
does not require such a certificate in order to validate update certificate in order to validate update messages containing the
messages containing the BGPSEC_Path_Signatures attribute. BGPSEC_Path attribute.
2. BGPSEC Negotiation 2. BGPSEC Negotiation
This document defines a new BGP capability [4]that allows a BGP This document defines two new BGP capabilities [6] that allow a BGP
speaker to advertise to its neighbors the ability to send and/or speaker to advertise to a neighbor the ability (respectively) to send
receive BGPSEC update messages (i.e., update messages containing the or to receive BGPSEC update messages (i.e., update messages
BGPSEC_Path_Signatures attribute). containing the BGPSEC_Path attribute).
2.1. BGPSEC Send Capability
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 3.
The three octets of the capability value are specified as follows. The three octets of the capability value are specified as follows.
Capability Value: BGPSEC Send Capability Value:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---------------------------------------+
| Send | Receive | Reserved | Version |
+---------------------------------------+ +---------------------------------------+
| AFI | | Version | Reserved |
+---------------------------------------+ +---------------------------------------+
| | | |
+---------------------------------------+ +------ AFI -----+
| Reserved | | |
+---------------------------------------+
| SAFI |
+---------------------------------------+ +---------------------------------------+
The high order bit (bit 0) of the first octet is set to 1 to indicate The first four bits of the first octet indicate the version of BGPSEC
that the sender is able to send BGPSEC update messages, and is set to for which the BGP speaker is advertising support. This document
zero otherwise. The next highest order bit (bit 1) of this octet is defines only BGPSEC version 0 (all four bits set to zero). Other
set to 1 to indicate that the sender is able to receive BGPSEC update versions of BGPSEC may be defined in future documents. A BGPSEC
messages, and is set to zero otherwise. The next two bits of the speaker MAY advertise support for multiple versions of BGPSEC by
capability value (bits 2 and 3) are reserved for future use. These including multiple versions of the BGPSEC capability in its BGP OPEN
reserved bits should be set to zero by the sender and ignored by the message.
receiver.
The four low order bits (4, 5, 6 and 7) of the first octet indicate The remaining four bits of the first octet are reserved for future
the version of BGPSEC for which the BGP speaker is advertising use. These bits are set to zero by the sender of the capability and
support. This document defines only BGPSEC version 0 (all four bits ignored by the receiver of the capability.
set to zero). Other versions of BGPSEC may be defined in future
documents. A BGPSEC speaker MAY advertise support for multiple
versions of BGPSEC by including multiple versions of the BGPSEC
capability in its BGP OPEN message.
If there does not exist at least one version of BGPSEC that is The second and third octets contain the 16-bit Address Family
supported by both peers in a BGP session, then the use of BGPSEC has Identifier (AFI) which indicates the address family for which the
not been negotiated. (That is, in such a case, messages containing BGPSEC speaker is advertising support for BGPSEC. This document only
the BGPSEC_Path_Signatures MUST NOT be sent.) specifies BGPSEC for use with two address families, IPv4 and IPv6,
AFI values 1 and 2 respectively. BGPSEC for use with other address
families may be specified in future documents.
If version 0 is the only version of BGPSEC for which both peers (in a 2.2. BGPSEC Receive Capability
BGP session) advertise support, then the use of BGPSEC has been
negotiated and the BGPSEC peers MUST adhere to the specification of This capability has capability code : TBD
BGPSEC provided in this document. (If there are multiple versions of
BGPSEC which are supported by both peers, then the behavior of those The capability length for this capability MUST be set to 3.
peers is outside the scope of this document.)
The three octets of the capability value are specified as follows.
BGPSEC Receive Capability Value:
0 1 2 3 4 5 6 7
+---------------------------------------+
| Version | Reserved |
+---------------------------------------+
| |
| AFI |
| |
+---------------------------------------+
The first four bits of the first octet indicate the version of BGPSEC
for which the BGP speaker is advertising support. This document
defines only BGPSEC version 0 (all four bits set to zero). Other
versions of BGPSEC may be defined in future documents. A BGPSEC
speaker MAY advertise support for multiple versions of BGPSEC by
including multiple versions of the BGPSEC capability in its BGP OPEN
message.
The remaining four bits of the first octet are reserved for future
use. These bits are set to zero by the sender of the capability and
ignored by the receiver of the capability.
The second and third octets contain the 16-bit Address Family The second and third octets contain the 16-bit Address Family
Identifier (AFI) which indicates the address family for which the Identifier (AFI) which indicates the address family for which the
BGPSEC speaker is advertising support for BGPSEC. This document only BGPSEC speaker is advertising BGPSEC support. This document only
specifies BGPSEC for use with two address families, IPv4 and IPv6, specifies BGPSEC for use with two address families, IPv4 and IPv6,
AFI values 1 and 2 respectively. BGPSEC for use with other address AFI values 1 and 2 respectively. BGPSEC for use with other address
families may be specified in future documents. families may be specified in future documents.
The fourth octet in the capability is reserved. It is anticipated 2.3. Negotiating BGPSEC Support
that this octet will not be used until such a time as the reserved
octet in the Multi-protocol extensions capability advertisement [2]
is specified for use. The reserved octet should be set to zero by
the sender and ignored by the receiver.
The fifth octet in the capability contains the 8-bit Subsequent A BGP speaker sends the BGPSEC Send Capability (see Section 2.1) in
Address Family Identifier (SAFI). This value is encoded as in the order to indicate that the speaker is willing to send BGP update
BGP multiprotocol extensions [2]. messages containing the BGPSEC_Path attribute (for a particular
address family). A BGP speaker sends the BGPSEC Receive Capability
(see Section 2.2) in order to indicate that the speaker is willing to
receive messages containing the BPGSEC_Path attribute.
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 includes two instances of this capability
capability (one for each address family) in the BGP OPEN message. A (one for each address family) in the BGP OPEN message. A BGPSEC
BGPSEC speaker SHOULD NOT advertise the capability of BGPSEC support speaker SHOULD NOT advertise the capability of BGPSEC support for a
for any <AFI, SAFI> combination unless it has also advertises the particular AFI unless it has also advertised the multiprotocol
multiprotocol extension capability for the same <AFI, SAFI> extension capability for the same AFI combination [3].
combination [2].
By indicating support for receiving BGPSEC update messages, a BGP In a session where BGP session, a peer is permitted to send update
speaker is, in particular, indicating that the following are true: messages containing the BGPSEC_Path attribute if, and only if:
o The BGP speaker understands the BGPSEC_Path_Signatures attribute o The given peer has sent the BGPSEC Send Capability for a
(see Section 3). particular version of BGPSEC and a particular address family; and
o The BGP speaker supports 4-byte AS numbers (see RFC 4893). o The other peer has sent the BGPSEC Receive Capability for the same
version of BGPSEC and the same address family.
In such a session, we say that the use of (the particular version of)
BGPSEC has been negotiated (for a particular address family). BGP
update messages without the BGPSEC_PATH attribute MAY be sent within
a session regardless of whether or not the use of BGPSEC is
successfully negotiated. However, if BGPSEC is not successfully
negotiated, then BGP update messages containing the BGPSEC_PATH
attribute MUST NOT be sent.
This document defines the behavior of implementations in the case
where BGPSEC version zero is the only version that has been
successfully negotiated. If there exist multiple versions have
BGPSEC that are negotiated for a particular session, the behavior of
the peers (e.g., which version of BGPSEC shall actually be used) will
be specified in a future document.
BGPSEC cannot provide meaningful security guarantees without support
for four-byte AS numbers. Therefore, any BGP speaker that announces
the capability to send BGPSEC messages, MUST also announce the
capability for four-byte AS support [4]. If a BGP speaker sends the
BGPSEC send capability but not the four-byte AS support capability
then BGPSEC has not been successfully negotiated, and update messages
containing the BGPSEC_Path attribute MUST NOT be sent within such a
session.
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 [9]. extended messages [9].
A BGP speaker MUST NOT send an update message containing the 3. The BGPSEC_Path Attribute
BGPSEC_Path_Signatures attribute within a given BGP session unless
both of the following are true:
o The BGP speaker indicated support for sending BGPSEC update
messages in its open message.
o The peer of the BGP speaker indicated support for receiving BGPSEC
update messages in its open message.
3. The BGPSEC_Path_Signatures Attribute
The BGPSEC_Path_Signatures attribute is a new optional (non- The BGPSEC_Path attribute is a new optional non-transitive BGP path
transitive) BGP path attribute. 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 attribute carries the secured information regarding
information, including the digital signatures that protect this AS the path of ASes through which an update message passes. This
Path information. We refer to those update messages that contain the includes the digital signatures used to protect this information. We
BGPSEC_Path_Signatures attribute as "BGPSEC Update messages". The refer to those update messages that contain the BGPSEC_Path attribute
BGPSEC_Path_Signatures attribute replaces the AS_PATH attribute, in a as "BGPSEC Update messages". The BGPSEC_Path attribute replaces the
BGPSEC update message. That is, update messages that contain the AS_PATH attribute in a BGPSEC update message. That is, update
BGPSEC_Path_Signatures attribute MUST NOT contain the AS_PATH messages that contain the BGPSEC_Path attribute MUST NOT contain the
attribute. AS_PATH attribute, and vice versa.
The BGPSEC_Path_Signatures attribute is made up of several parts. The BGPSEC_Path attribute is made up of several parts. The following
The following high-level diagram provides an overview of the high-level diagram provides an overview of the structure of the
structure of the BGPSEC_Path_Signatures attribute: BGPSEC_Path attribute:
High-Level Diagram of the BGPSEC_Path_Signatures Attribute High-Level Diagram of the BGPSEC_Path Attribute
BGPSEC_Path_Signatures
+---------------------------------------------------------+ +---------------------------------------------------------+
| +-----------------+ | | +-----------------+ |
| | Secure Path | +-----------------+ | | | Secure Path | |
| +-----------------+ | Additional Info | | | +-----------------+ |
| | AS X | +-----------------+ | | | AS X | |
| | pCount X | | Info Type | | | | pCount X | |
| | Flags X | | Info Length | | | | Flags X | |
| | AS Y | | Info Value | | | | AS Y | |
| | pCount Y | +-----------------+ | | | pCount Y | |
| | Flags Y | | | | Flags Y | |
| | ... | | | | ... | |
| +-----------------+ | | +-----------------+ |
| | | |
| +-----------------+ +-----------------+ | | +-----------------+ +-----------------+ |
| | Sig Block 1 | | Sig Block 2 | | | | Sig Block 1 | | Sig Block 2 | |
| +-----------------+ +-----------------+ | | +-----------------+ +-----------------+ |
| | Alg Suite 1 | | Alg Suite 2 | | | | Alg Suite 1 | | Alg Suite 2 | |
| | SKI X | | SKI X | | | | SKI X1 | | SKI X1 | |
| | Sig Length X | | Sig Length X | | | | Signature X1 | | Signature X1 | |
| | Signature X | | Signature X | | | | SKI Y1 | | SKI Y1 | |
| | SKI Length Y | | SKI Length Y | | | | Signature Y1 | | Signature Y1 | |
| | SKI Y | | SKI Y | |
| | Sig Length Y | | Sig Length Y | |
| | Signature Y | | Signature Y | |
| | ... | | .... | | | | ... | | .... | |
| +-----------------+ +-----------------+ | | +-----------------+ +-----------------+ |
| | | |
+---------------------------------------------------------+ +---------------------------------------------------------+
The following is a more detailed explanation of the format of the The following is the specification of the format for the BGPSEC_Path
BGPSEC_Path_Signatures attribute. attribute.
BGPSEC_Path_Signatures Attribute BGPSEC_Path Attribute
+-------------------------------------------------------+ +-------------------------------------------------------+
| Secure_Path (variable) | | Secure_Path (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 is
be contained in the AS_PATH attribute. A BGPSEC update message contained in a non-BGPSEC AS_PATH attribute. A BGPSEC update message
containing the BGPSEC_PATH_SIGNATURES attribute MUST NOT contain the containing the BGPSEC_PATH attribute MUST NOT contain the AS_PATH
AS_PATH attribute. The path information is used by BGPSEC speakers attribute. The Secure_Path is used by BGPSEC speakers in the same
in the same way that information from the AS_PATH is used by non- way that information from the AS_PATH is used by non-BGPSEC speakers.
BGPSEC speakers. The format of the Secure_Path is described below in The format of the Secure_Path is described below in Section 3.1.
Section 3.1.
The Additional_Info contains additional signed information about the
update message. Additional_Info is specified as a type-length-value
field for future extensibility. However, this specification defines
only a single (null) type of Additional Info which has zero length.
It is anticipated that future specifications may specify semantics
for Info Types other than zero. See Section 3.2 below for more
detail.
The BGPSEC_Path_Signatures attribute will contain one or two The BGPSEC_Path attribute will contain one or two Signature_Blocks,
Signature_Blocks, each of which corresponds to a different algorithm each of which corresponds to a different algorithm suite. Each of
suite. Each of the Signature_Blocks will contain a signature segment the Signature_Blocks will contain a signature segment for one AS
for each AS number (i.e, secure path segment) in the Secure_Path. In number (i.e, secure path segment) in the Secure_Path. In the most
the most common case, the BGPSEC_Path_Signatures attribute will common case, the BGPSEC_Path attribute will contain only a single
contain only a single Signature_Block. However, in order to enable a Signature_Block. However, in order to enable a transition from an
transition from an old algorithm suite to a new algorithm suite, it old algorithm suite to a new algorithm suite (without a flag day), it
will be necessary to include two Signature_Blocks (one for the old will be necessary to include two Signature_Blocks (one for the old
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 3.2.
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 attribute.
Secure_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 entire
variable-length sequence of Secure_Path Segments. As explained Secure_Path (including the two octets used to express this length
below, each Secure_Path segment is six octets long. Note that this field). As explained below, each Secure_Path segment is six octets
means the Secure_Path Length is six times the number Secure_Path long. Note that this means the Secure_Path Length is two greater
Segments (i.e., the number of AS numbers in the path). than 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 originating AS of the NLRI
message. specified in the update message.
Secure_Path Segment Secure_Path Segment
+----------------------------+ +----------------------------+
| AS Number (4 octets) | | AS Number (4 octets) |
+----------------------------+ +----------------------------+
| pCount (1 octet) | | pCount (1 octet) |
+----------------------------+ +----------------------------+
| Flags (1 octet) | | Flags (1 octet) |
+----------------------------+ +----------------------------+
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 attribute. (See Section 4 for
Section 4 for more information on populating this field.) 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 prepending
copies of their AS to the AS_PATH without requiring the speaker to multiple copies of their AS to the AS_PATH without requiring the
generate multiple signatures. speaker to generate multiple signatures.
The first bit of the Flags field is the Confed_Segment flag. The The first bit of the Flags field is the Confed_Segment flag. The
Confed_Segment flag is set to one to indicate that the BGPSEC speaker Confed_Segment flag is set to one to indicate that the BGPSEC speaker
that constructed this Secure_Path segment is sending the update that constructed this Secure_Path segment is sending the update
message to a peer AS within the same Autonomous System confederation message to a peer AS within the same Autonomous System confederation
[3]. (That is, the Confed_Segment flag is set in a BGPSEC update [5]. (That is, the Confed_Segment flag is set in a BGPSEC update
message whenever in a non-BGPSEC update message the BGP speaker's AS message whenever in a non-BGPSEC update message the BGP speaker's AS
would appear in a AS_PATH segment of type AS_CONFED_SEQUENCE.) In would appear in a AS_PATH segment of type AS_CONFED_SEQUENCE.) In
all other cases the Confed_Segment flag is set to zero. all other cases the Confed_Segment flag is set to zero.
The remaining seven bits of the Flags field are reserved for future The remaining seven bits of the Flags MUST be set to zero by the
use. These bits MUST be set to zero by the sender. The receiver sender, and ignored by the receiver. Note, however, that the
uses the entire Flags octet to verify the digital signature signature is computed over all eight bits of the flags field.
(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
some other property (besides being in the same confederation) of the
connection between two peer ASes.
3.2. Additional_Info
Here we provide a detailed description of the Additional_Info in the
BGPSEC_Path_Signatures attribute.
Additional_Info
+---------------------------------------------+
| Info Type (1 octet) |
+---------------------------------------------+
| Info Length (1 octet) |
+---------------------------------------------+
| Info Value (variable) |
+---------------------------------------------+
The Info Type field is a one-octet value that identifies the type of
additional information included in the Info Value field. This
specification defines a single (null) type of Additional_Info. The
Info Type for this null type is zero.
The Info Length field contains the length in octets of the Info Value
field. For the (null) Info Type zero specified in this document, the
Info Length MUST be zero.
The syntax and semantics contained in the Info Value field depends on
the type contained in the Info Type field. For the (null) Info Type
zero specified in this document, the Info Value field is empty (since
the Info Length field must be zero).
Implementations compliant with this specification MUST set the Info
Type to zero in BGPSEC update messages for route advertisements that
they originate (see Section 4.1 for more details). When an
implementation compliant with this specification receives a BGPSEC
update message with an Info Type field that it does not understand
(i.e., an Info Type other than zero), the implementation MUST use the
Additional_Info when it verifies digital signatures (as per Section
5.2). However, other than signature verification, the implementation
MUST ignore the Info Value field when it does not understand the Info
Type.
EDITOR'S NOTE: In a previous version of this document there was an
Expire Time that was used to provide protection against replay of old
(stale) digital signatures or failure to propagate a withdrawal
message. This mechanism was removed from the current version of the
document. Please see the SIDR mailing list for discussions related
to protection against replay attacks. Depending on the result of
discussions within the SIDR working group this Additional Info field
could at some future point be used to re-introduce Expire Time, or
some other octets used in a future replay protection mechanism. The
authors believe that the current instructions whereby the sender uses
a null Additional_Info type and the receiver ignores Additional_Info
types that it does not understand provides an opportunity to use
these octets in the future in a backwards-compatible fashion.
3.3. Signature_Block 3.2. 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 attribute.
Signature_Block Signature_Block
+---------------------------------------------+ +---------------------------------------------+
| Algorithm Suite Identifier (1 octet) |
+---------------------------------------------+
| Signature_Block Length (2 octets) | | Signature_Block Length (2 octets) |
+---------------------------------------------+ +---------------------------------------------+
| Algorithm Suite Identifier (1 octet) |
+---------------------------------------------+
| Sequence of Signature Segments (variable) | | Sequence of Signature Segments (variable) |
+---------------------------------------------+ +---------------------------------------------+
The Signature_Block Length is the total number of octets in the
Signature_Block (including the two octets used to express this length
field).
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[12]. algorithms document[11].
The Signature_Block Length is the total number of octets in all
Signature Segments (i.e., the total size of the variable-length
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
BGPSEC_Path_Signatures Attribute. (That is, one Signature Segment Attribute. (That is, one Signature Segment for each distinct AS on
for each distinct AS on the path for the NLRI in the Update message.) the path for the NLRI in the Update message.)
Signature Segments Signature Segments
+---------------------------------------------+ +---------------------------------------------+
| Subject Key Identifier (20 octets) | | Subject Key Identifier (20 octets) |
+---------------------------------------------+ +---------------------------------------------+
| Signature Length (2 octets) | | Signature Length (2 octets) |
+---------------------------------------------+ +---------------------------------------------+
| Signature (variable) | | Signature (variable) |
+---------------------------------------------+ +---------------------------------------------+
The Subject Key Identifier contains the value in the Subject Key The Subject Key Identifier contains the value in the Subject Key
Identifier extension of the RPKI end-entity certificate that is used Identifier extension of the RPKI router certificate [10] that is used
to verify the signature (see Section 5 for details on validity of to verify the signature (see Section 5 for details on validity of
BGPSEC update messages). BGPSEC update messages).
The Signature Length field contains the size (in octets) of the value The Signature Length field contains the size (in octets) of the value
in the Signature field of the Signature Segment. in the Signature field of the Signature Segment.
The Signature contains a digital signature that protects the NLRI and The Signature contains a digital signature that protects the NLRI and
the BGPSEC_Path_Signatures attribute (see Sections 4 and 5 for the BGPSEC_Path attribute (see Sections 4 and 5 for details on
details on generating and verifying this signature, respectively). signature generation and validation, respectively).
4. Generating a BGPSEC Update 4. Generating a BGPSEC Update
Sections 4.1 and 4.2 cover two cases in which a BGPSEC speaker may Sections 4.1 and 4.2 cover two cases in which a BGPSEC speaker may
generate an update message containing the BGPSEC_Path_Signatures generate an update message containing the BGPSEC_Path attribute. The
attribute. The first case is that in which the BGPSEC speaker first case is that in which the BGPSEC speaker originates a new route
originates a new route advertisement (Section 4.1). That is, the advertisement (Section 4.1). That is, the BGPSEC speaker is
BGPSEC speaker is constructing an update message in which the only AS constructing an update message in which the only AS to appear in the
to appear in the BGPSEC_Path_Signatures is the speaker's own AS. The BGPSEC_Path is the speaker's own AS. The second case is that in
second case is that in which the BGPSEC speaker receives a route which the BGPSEC speaker receives a route advertisement from a peer
advertisement from a peer and then decides to propagate the route and then decides to propagate the route advertisement to an external
advertisement to an external (eBGP) peer (Section 4.2). That is, the (eBGP) peer (Section 4.2). That is, the BGPSEC speaker has received
BGPSEC speaker has received a BGPSEC update message and is a BGPSEC update message and is constructing a new update message for
constructing a new update message for the same NLRI in which the the same NLRI in which the BGPSEC_Path attribute will contain AS
BGPSEC_Path_Signatures attribute will contain AS number(s) other than number(s) other than the speaker's own AS.
the speaker's own AS.
In the remaining case where the BGPSEC speaker is sending the update The remaining case is where the BGPSEC speaker sends the update
message to an internal (iBGP) peer, the BGPSEC speaker populates the message to an internal (iBGP) peer. When originating a new route
BGPSEC_Path_Signatures attribute by copying the advertisement and sending it to an internal peer, the BGPSEC speaker
BGPSEC_Path_Signatures attribute from the received update message. creates a new BGPSEC_Path attribute with zero Secure_Path segments
That is, the BGPSEC_Path_Signatures attribute is copied verbatim. and zero Signature Segments. When propagating a received route
Note that in the case that a BGPSEC speaker chooses to forward to an advertisement to an internal peer, the BGPSEC speaker populates the
iBGP peer a BGPSEC update message that has not been successfully BGPSEC_Path attribute by copying the BGPSEC_Path attribute from the
validated (see Section 5), the BGPSEC_Path_Signatures attribute received update message. That is, the BGPSEC_Path attribute is
copied verbatim. Note that in the case that a BGPSEC speaker chooses
to forward to an iBGP peer a BGPSEC update message that has not been
successfully validated (see Section 5), the BGPSEC_Path attribute
SHOULD NOT be removed. (See Section 7 for the security ramifications SHOULD NOT be removed. (See Section 7 for the security ramifications
of removing BGPSEC signatures.) of removing BGPSEC signatures.)
The information protected by the signature on a BGPSEC update message The information protected by the signature on a BGPSEC update message
includes the AS number of the peer to whom the update message is includes the AS number of the peer to whom the update message is
being sent. Therefore, if a BGPSEC speaker wishes to send a BGPSEC being sent. Therefore, if a BGPSEC speaker wishes to send a BGPSEC
update to multiple BGP peers, it MUST generate a separate BGPSEC update to multiple BGP peers, it MUST generate a separate BGPSEC
update message for each unique peer AS to which the update message is update message for each unique peer AS to which the update message is
sent. sent.
A BGPSEC update message MUST advertise a route to only a single NLRI. A BGPSEC update message MUST advertise a route to only a single NLRI.
This is because a BGPSEC speaker receiving an update message with This is because a BGPSEC speaker receiving an update message with
multiple NLRI would be unable to construct a valid BGPSEC update multiple NLRI would be unable to construct a valid BGPSEC update
message (i.e., valid path signatures) containing a subset of the NLRI message (i.e., valid path signatures) containing a subset of the NLRI
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 In order to create or add a new signature to a BGPSEC update message
update message with a given algorithm suite, the BGPSEC speaker must with a given algorithm suite, the BGPSEC speaker must possess a
possess a private key suitable for generating signatures for this private key suitable for generating signatures for this algorithm
algorithm suite. Additionally, this private key must correspond to suite. Additionally, this private key must correspond to the public
the public key in a valid Resource PKI end-entity certificate whose key in a valid Resource PKI end-entity certificate whose AS number
AS number resource extension includes the BGPSEC speaker's AS number resource extension includes the BGPSEC speaker's AS number [10]. Note
[11]. Note also that new signatures are only added to a BGPSEC also that new signatures are only added to a BGPSEC update message
update message when a BGPSEC speaker is generating an update message when a BGPSEC speaker is generating an update message to send to an
to send to an external peer (i.e., when the AS number of the peer is external peer (i.e., when the AS number of the peer is not equal to
not equal to the BGPSEC speaker's own AS number). Therefore, a the BGPSEC speaker's own AS number). Therefore, a BGPSEC speaker who
BGPSEC speaker who only sends BGPSEC update messages to peers within only sends BGPSEC update messages to peers within its own AS, it does
its own AS, it does not need to possess any private signature keys. 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), when an update whose path will contain only a single AS number), when
sending the route advertisement to an external, BGPSEC-speaking peer, sending the route advertisement to an external, BGPSEC-speaking peer,
the BGPSEC speaker creates a new BGPSEC_Path_Signatures attribute as the BGPSEC speaker creates a new BGPSEC_Path 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 an 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 router
certificate(s) that will be used to verify the digital signature(s) certificate(s) [10] that will be used to verify the digital
constructed by this BGPSEC speaker. signature(s) constructed by this BGPSEC speaker.
Note that the BGPSEC_Path_Signatures attribute and the AS4_Path The BGPSEC_Path attribute and the AS_Path attribute are mutually
attribute are mutually exclusive. That is, any update message exclusive. That is, any update message containing the BGPSEC_Path
containing the BGPSEC_Path_Signatures attribute MUST NOT contain the attribute MUST NOT contain the AS_Path attribute. The information
AS4_Path attribute nor the AS_Path attribute. The information that that would be contained in the AS_Path attribute is instead conveyed
would be contained in the AS4_Path (or AS_Path) attribute is instead in the Secure_Path portion of the BGPSEC_Path attribute.
conveyed in the Secure_Path portion of the BGPSEC_Path_Signatures
attribute.
Note that the Resource PKI enables the legitimate holder of IP The Resource PKI enables the legitimate holder of IP address
address prefix(es) to issue a signed object, called a Route prefix(es) to issue a signed object, called a Route Origination
Origination Authorization (ROA), that authorizes a given AS to Authorization (ROA), that authorizes a given AS to originate routes
originate routes to a given set of prefixes (see [7]). Note that to a given set of prefixes (see [8]). Note that validation of a
validation of a BGPSEC update message will fail (i.e., the validation BGPSEC update message will fail (i.e., the validation algorithm,
algorithm, specified in Section 5.2, returns 'Not Good') unless there specified in Section 5.2, returns 'Not Valid') unless there exists a
exists a valid ROA authorizing the first AS in the Secure_Path valid ROA authorizing the first AS in the Secure_Path portion of the
portion of the BGPSEC_Path_Signatures attribute to originate routes BGPSEC_Path attribute to originate routes to the prefix being
to the prefix being advertised. Therefore, a BGPSEC speaker SHOULD advertised. Therefore, a BGPSEC speaker SHOULD NOT originate a
NOT originate a BGPSEC update advertising a route for a given prefix BGPSEC update advertising a route for a given prefix unless there
unless there exists a valid ROA authorizing the BGPSEC speaker's AS exists a valid ROA authorizing the BGPSEC speaker's AS to originate
to originate routes to this prefix. 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.
If the BGPSEC speaker is not a member of an autonomous system If the BGPSEC speaker is not a member of an autonomous system
confederation [3], then the Flags field of the Secure_Path Segment confederation [5], then the Flags field of the Secure_Path Segment
MUST be set to zero. (Members of a confederation should follow the MUST be set to zero. (Members of a confederation should follow the
special processing instructions for confederation members in Section special processing instructions for confederation members in Section
4.4.) 4.4.)
The BGPSEC speaker next constructs the Additional_Info portion of the
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
is empty (has length zero). It is anticipated that future
specifications may specify values of Info Type other than zero.
Therefore, BGPSEC receivers compliant with this specification must be
able to accept Additional_Info fields with non-zero Info Type. Such
receivers will use the Additional_Field to verify digital signatures
(see Section 5) but will otherwise ignore Additional_Field non-zero
Info Fields.
Typically, a BGPSEC speaker will use only a single algorithm suite, Typically, a BGPSEC speaker will use only a single algorithm suite,
and thus create only a single Signature_Block in the and thus create only a single Signature_Block in the BGPSEC_Path
BGPSEC_Path_Signatures attribute. However, to ensure backwards attribute. However, to ensure backwards compatibility during a
compatibility during a period of transition from a 'current' period of transition from a 'current' algorithm suite to a 'new'
algorithm suite to a 'new' algorithm suite, it will be necessary to algorithm suite, it will be necessary to originate update messages
originate update messages that contain a Signature_Block for both the that contain a Signature_Block for both the 'current' and the 'new'
'current' and the 'new' algorithm suites (see Section 6.1). algorithm suites (see Section 6.1).
When originating a new route advertisement, each Signature_Block MUST When originating a new route advertisement, each Signature_Block MUST
consist of a single Signature Segment. The following describes how consist of a single Signature Segment. The following describes how
the BGPSEC speaker populates the fields of the Signature_Block. the BGPSEC speaker populates the fields of the Signature_Block.
The Subject Key Identifier field (see Section 3) is populated with The Subject Key Identifier field (see Section 3) 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 router certificate corresponding to the BGPSEC speaker[10].
Subject Key Identifier will be used by recipients of the route This 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 contains a digital signature that binds the NLRI The Signature field contains a digital signature that binds the NLRI
and BGPSEC_Path_Signatures attribute to the RPKI end-entity and BGPSEC_Path attribute to the RPKI router corresponding to the
certificate used by the BGPSEC speaker. The digital signature is BGPSEC speaker. The digital signature is computed as follows:
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 (Origin AS, pCount, and Flags), the Number, the Secure_Path (Origin AS, pCount, and Flags), Algorithm
Additional_Info (Info Type, Info Length, and Info Value), Suite Identifier, and NLRI. The Target AS Number is the AS to
Algorithm Suite Identifier, and NLRI. The Target AS Number is the whom the BGPSEC speaker intends to send the update message. (Note
AS to whom the BGPSEC speaker intends to send the update message. that the Target AS number is the AS number announced by the peer
(Note that the Target AS number is the AS number announced by the in the OPEN message of the BGP session within which the update is
peer in the OPEN message of the BGP session within which the sent.)
update is sent.)
Sequence of Octets to be Signed Sequence of Octets to be Signed
+------------------------------------+ +------------------------------------+
| Target AS Number (4 octets) | | Target AS Number (4 octets) |
+------------------------------------+ +------------------------------------+
| Origin AS Number (4 octets) | ---\ | Origin AS Number (4 octets) | ---\
+------------------------------------+ \ +------------------------------------+ \
| pCount (1 octet) | > Secure_Path | pCount (1 octet) | > Secure_Path
+------------------------------------+ / +------------------------------------+ /
| Flags (1 octet) | ---/ | Flags (1 octet) | ---/
+------------------------------------+ +------------------------------------+
| Info Type (1 octet) | ---\ | Algorithm Suite Id. (1 octet) |
+------------------------------------+ \ +------------------------------------+
| Info Length (1 octet) | > Additional_Info | NLRI Length (1 octet) |
+------------------------------------+ / +------------------------------------+
| Info Value (variable) | ---/ | NLRI Prefix (variable) |
+------------------------------------+ +------------------------------------+
| Algorithm Suite Id. (1 octet) |
+------------------------------------+
| NLRI Length (1 octet) |
+------------------------------------+
| NLRI Prefix (variable) |
+------------------------------------+
o Apply to this octet sequence the digest algorithm (for the o Apply to this octet sequence the digest algorithm (for the
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.
4.2. Propagating a Route Advertisement 4.2. Propagating a Route Advertisement
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 BGPSEC_Path attribute (with one or more signatures) from an (internal
an (internal or external) peer, it may choose to propagate the route or external) peer, it may choose to propagate the route advertisement
advertisement by sending to its (internal or external) peers by by sending to its (internal or external) peers by creating a new
creating a new BGPSEC advertisement for the same prefix. BGPSEC advertisement for the same prefix.
If a BGPSEC router has received only non-BGPSEC update messages If a BGPSEC router has received only a non-BGPSEC update message
(without the BGPSEC_Path_Signatures attribute), containing the (without the BGPSEC_Path attribute), containing the AS_Path
AS_Path attribute, from a peer for a given prefix and if it chooses attribute, from a peer for a given prefix and if it chooses to
to propagate that peer's route for the prefix, then it MUST NOT propagate that peer's route for the prefix, then it MUST NOT attach
attach any BGPSEC_Path_Signatures attribute to the corresponding any BGPSEC_Path attribute to the corresponding update being
update being propagated. (Note that a BGPSEC router may also receive propagated. (Note that a BGPSEC router may also receive a non-BGPSEC
a non-BGPSEC update message from an internal peer without the AS_Path update message from an internal peer without the AS_Path attribute,
attribute, i.e., with just the NLRI in it. In that case, the prefix i.e., with just the NLRI in it. In that case, the prefix is
is originating from that AS and hence the BGPSEC speaker SHOULD sign originating from that AS and hence the BGPSEC speaker SHOULD sign and
and forward the update to its external peers, as specified in Section forward the update to its external peers, as specified in Section
4.1.) 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 attribute) from a peer for a given prefix and
prefix and it chooses to propagate that peer's route for the prefix, it chooses to propagate that peer's route for the prefix, then it
then it SHOULD propagate the route as a BGPSEC update message SHOULD propagate the route as a BGPSEC update message containing the
containing the BGPSEC_Path_Signatures attribute. However, the BGPSEC BGPSEC_Path attribute. However, the BGPSEC speaker MAY propagate the
speaker MAY propagate the route as a (unsigned) BGP update message route as a (unsigned) BGP update message without the BGPSEC_Path
without the BGPSEC_Path_Signatures attribute. 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 attribute) has significant
significant security ramifications. (See Section 7 for discussion of security ramifications. (See Section 7 for discussion of the
the security ramifications of removing BGPSEC signatures.) security ramifications of removing BGPSEC signatures.) Therefore,
Therefore, when a route advertisement is received via a BGPSEC update when a route advertisement is received via a BGPSEC update message,
message, propagating the route advertisement without the propagating the route advertisement without the BGPSEC_Path attribute
BGPSEC_Path_Signatures attribute is NOT RECOMMENDED. Furthermore, is NOT RECOMMENDED, unless the message is sent to a peer that did not
note that when a BGPSEC speaker propagates a route advertisement with advertise the capability to receive BGPSEC update messages (see
the BGPSEC_Path_Signatures attribute it is not attesting to the Section 4.4).
validation state of the update message it received. (See Section 7
for more discussion of the security semantics of BGPSEC signatures.) Furthermore, note that when a BGPSEC speaker propagates a route
advertisement with the BGPSEC_Path attribute it is not attesting to
the validation state of the update message it received. (See Section
7 for more discussion of the security semantics of BGPSEC
signatures.)
If the BGPSEC speaker is producing an update message which would, in If the BGPSEC speaker is producing an update message which would, in
the absence of BGPSEC, contain an AS_SET (e.g., the BGPSEC speaker is the absence of BGPSEC, contain an AS_SET (e.g., the BGPSEC speaker is
performing proxy aggregation), then the BGPSEC speaker MUST NOT performing proxy aggregation), then the BGPSEC speaker MUST NOT
include the BGPSEC_Path_Signatures attribute. In such a case, the include the BGPSEC_Path attribute. In such a case, the BGPSEC
BGPSEC speaker must remove any existing BGPSEC_Path_Signatures in the speaker must remove any existing BGPSEC_Path in the received
received advertisement(s) for this prefix and produce a standard advertisement(s) for this prefix and produce a standard (non-BGPSEC)
(non-BGPSEC) update message. It should be noted that BCP 172 [5] update message. It should be noted that BCP 172 [12] recommends
recommends against the use of AS_SET and AS_CONFED_SET in AS_PATH in against the use of AS_SET and AS_CONFED_SET in AS_PATH in BGP
BGP updates. updates.
To generate the BGPSEC_Path_Signatures attribute on the outgoing To generate the BGPSEC_Path attribute on the outgoing update message,
update message, the BGPSEC speaker first prepends a new Secure_Path the BGPSEC speaker first prepends a new Secure_Path Segment (places
Segment (places in first position) to the Secure_Path. The AS number in first position) to the Secure_Path. The AS number in this
in this Secure_Path segment MUST match the AS number in the AS number 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 router certificate(s)
certificate(s) that will be used to verify the digital signature(s) that will be used to verify the digital signature(s) constructed by
constructed by this BGPSEC speaker. this BGPSEC speaker[10].
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
the pCount field to a value greater than 1. (See Section 4.1 for a the pCount field to a value greater than 1. (See Section 4.1 for a
discussion of setting pCount to a value greater than 1.) A route discussion of setting pCount to a value greater than 1.) A route
server that participates in the BGP control path, but does not act as server that participates in the BGP control path, but does not act as
a transit AS in the data plane, may choose to set pCount to 0. This a transit AS in the data plane, may choose to set pCount to 0. This
option enables the route server to participate in BGPSEC and obtain option enables the route server to participate in BGPSEC and obtain
the associated security guarantees without increasing the effective the associated security guarantees without increasing the effective
length of the AS path. (Note that BGPSEC speakers compute the length of the AS path. (Note that BGPSEC speakers compute the
effective length of the AS path by summing the pCount values in the effective length of the AS path by summing the pCount values in the
BGPSEC_Path_Signatures attribute, see Section 5.) However, when a BGPSEC_Path attribute, see Section 5.) However, when a route server
route server sets the pCount value to 0, it still inserts its AS sets the pCount value to 0, it still inserts its AS number into the
number into the Secure_Path segment, as this information is needed to Secure_Path segment, as this information is needed to validate the
validate the signature added by the route server. Note that the signature added by the route server. Note that the option of setting
option of setting pCount to 0 is intended only for use by route pCount to 0 is intended only for use by route servers that desire not
servers that desire not to increase the effective AS-PATH length of to increase the effective AS-PATH length of routes they advertise.
routes they advertise. The pCount field SHOULD NOT be set to 0 in The pCount field SHOULD NOT be set to 0 in other circumstances.
other circumstances. BGPSEC speakers SHOULD drop incoming update BGPSEC speakers SHOULD drop incoming update messages with pCount set
messages with pCount set to zero in cases where the BGPSEC speaker to zero in cases where the BGPSEC speaker does not expect its peer to
does not expect its peer to set pCount to zero (i.e., cases where the set pCount to zero (i.e., cases where the peer is not acting as a
peer is not acting as a route server). route server).
If the BGPSEC speaker is not a member of an autonomous system If the BGPSEC speaker is not a member of an autonomous system
confederation [3], then the Flags field of the Secure_Path Segment confederation [5], then the Confed_Segment bit of the Flags field of
MUST be set to zero. (Members of a confederation should follow the the Secure_Path Segment MUST be set to zero. (Members of a
special processing instructions for confederation members in Section confederation should follow the special processing instructions for
4.4.) confederation members in Section 4.3.)
The BGPSEC speaker next copies the Additional_Info portion of the
BGPSEC_Path_Signatures directly from the received update message to
the new update message (that it is constructing). Note that the
BGPSEC speaker MUST NOT change the Additional_Info as any change to
Additional_Info will cause the new BGPSEC update message to fail
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
BGPSEC_Path_Signatures attribute (i.e., propagate it as an unsigned attribute. (That is, if it chooses to propagate this route
BGP update message). advertisement at all, it must do so 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 5.2) deems a BGPSEC update message to be algorithm (see Section 5.2) deems a BGPSEC update message to be
'Good' if there is at least one supported algorithm suite (and 'Valid' 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 'Valid'. This means
that a 'Good' BGPSEC update message may contain a Signature_Block that a 'Valid' BGPSEC update message may contain a Signature_Block
which is not deemed 'Good' (e.g., contains signatures that the BGPSEC which is not deemed 'Valid' (e.g., contains signatures that the
does not successfully verify). Nonetheless, such Signature_Blocks BGPSEC does not successfully verify). Nonetheless, such
MUST NOT be removed. (See Section 7 for a discussion of the security Signature_Blocks MUST NOT be removed. (See Section 7 for a
ramifications of this design choice.) discussion of the security 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 in the Secure_Path order as the corresponding Secure_Path segments in the Secure_Path
portion of the BGPSEC_Path_Signatures attribute. The BGPSEC speaker portion of the BGPSEC_Path attribute. The BGPSEC speaker populates
populates the fields of this new signature segment as follows. the fields of this new signature segment as 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 router corresponding to the BGPSEC speaker[10]. 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 attribute to the RPKI router
end-entity certificate used by the BGPSEC speaker. The digital certificate corresponding to 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 that 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.
skipping to change at page 20, line 31 skipping to change at page 18, line 11
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. Processing Instructions for Confederation Members 4.3. Processing Instructions for Confederation Members
Members of autonomous system confederations [3] must additionally Members of autonomous system confederations [5] MUST additionally
follow the instructions in this section for processing BGPSEC update follow the instructions in this section for processing BGPSEC update
messages. messages.
When a confederation member sends a BGPSEC update message to a peer When a confederation member sends a BGPSEC update message to a peer
that is a member of the same confederation, the confederation member that is a member of the same confederation, the confederation member
puts its (private) Member-AS Number (as opposed to the public AS puts its (private) Member-AS Number (as opposed to the public AS
Confederation Identifier) in the AS Number field of the Secure_Path Confederation Identifier) in the AS Number field of the Secure_Path
Segment that it adds to the BGPSEC update message. Furthermore, when Segment that it adds to the BGPSEC update message. Furthermore, when
a confederation member sends a BGPSEC update message to a peer that a confederation member sends a BGPSEC update message to a peer that
is a member of the same confederation, the BGPSEC speaker that is a member of the same confederation, the BGPSEC speaker that
skipping to change at page 21, line 16 skipping to change at page 18, line 45
Signature_Segment that it generates to be zero (in lieu of Signature_Segment that it generates to be zero (in lieu of
calculating the correct digital signature as described in Sections calculating the correct digital signature as described in Sections
4.1 and 4.2). Note that if a confederation chooses not to verify 4.1 and 4.2). Note that if a confederation chooses not to verify
digital signatures within the confederation, then BGPSEC is able to digital signatures within the confederation, then BGPSEC is able to
provide no assurances about the integrity of the (private) Member-AS provide no assurances about the integrity of the (private) Member-AS
Numbers placed in Secure_Path segments where the Confed_Segment flag Numbers placed in Secure_Path segments where the Confed_Segment flag
is set to one. is set to one.
When a confederation member receives a BGPSEC update message from a When a confederation member receives a BGPSEC update message from a
peer within the confederation and propagates it to a peer outside the peer within the confederation and propagates it to a peer outside the
confederation, it must remove all of the Secure_Path Segments added confederation, it needs to remove all of the Secure_Path Segments
by confederation members as well as the corresponding Signature added by confederation members as well as the corresponding Signature
Segments. To do this, the confederation member propagating the route Segments. To do this, the confederation member propagating the route
outside the confederation does the following: outside the confederation does the following:
o First, starting with the least recently added Secure_Path o First, starting with the most recently added Secure_Path segments,
segments, remove all of the consecutive Secure_Path segments that remove all of the consecutive Secure_Path segments that have the
have the Confed_Segment flag set to one. Stop this process once a Confed_Segment flag set to one. Stop this process once a
Scure_Path segment is reached which has its Confed_Segment flag Scure_Path segment is reached which has its Confed_Segment flag
set to zero. Keep a count of the number of segments removed in set to zero. Keep a count of the number of segments removed in
this fashion. this fashion.
o Second, starting with the most recently added Signature Segment, o Second, starting with the most recently added Signature Segment,
remove a number of Signature Segments equal to the number of remove a number of Signature Segments equal to the number of
Secure_Path Segments removed in the previous step. (That is, Secure_Path Segments removed in the previous step. (That is,
remove the K most recently added signature segments, where K is remove the K most recently added signature segments, where K is
the number of Secure_Path Segments removed in the previous step.) the number of Secure_Path Segments removed in the previous step.)
o Finally, add a Secure_Path Segment containing, in the AS field, o Finally, add a Secure_Path Segment containing, in the AS field,
the AS Confederation Identifier (the public AS number of the the AS Confederation Identifier (the public AS number of the
confederation) as well as a corresponding Signature Segment. Note confederation) as well as a corresponding Signature Segment. Note
that all fields other that the AS field are populated as per that all fields other that the AS field are populated as per
Sections 4.1 and 4.2. Sections 4.1 and 4.2.
When validating a received BGPSEC update message, confederation When validating a received BGPSEC update message, confederation
members must make the following adjustment to the algorithm presented members need to make the following adjustment to the algorithm
in Section 5.2. When a confederation member processes (validates) a presented in Section 5.2. When a confederation member processes
Signature Segment and its corresponding Secure_Path Segment, the (validates) a Signature Segment and its corresponding Secure_Path
confederation member must note that for a signature produced by a Segment, the confederation member must note that for a signature
BGPSEC speaker outside of a confederation, the Target AS will always produced by a BGPSEC speaker outside of a confederation, the Target
be the AS Confederation Identifier (the public AS number of the AS will always be the AS Confederation Identifier (the public AS
confederation) as opposed to the Member-AS Number. number of the confederation) as opposed to the Member-AS Number.
To handle this case, when a BGPSEC speaker (that is a confederation To handle this case, when a BGPSEC speaker (that is a confederation
member) processes a current Secure_Path Segment that has the member) processes a current Secure_Path Segment that has the
Confed_Segment flag set to zero, if the next most recently added Confed_Segment flag set to zero, if the next most recently added
Secure_Path segment has the Confed_Segment flag set to one then, when Secure_Path segment has the Confed_Segment flag set to one then, when
computing the digest for the current Secure_Path segment, the BGPSEC computing the digest for the current Secure_Path segment, the BGPSEC
speaker takes the Target AS Number to be the AS Confederation speaker takes the Target AS Number to be the AS Confederation
Identifier of the validating BGPSEC speaker's own confederation. Identifier of the validating BGPSEC speaker's own confederation.
(Note that the algorithm in Section 5.2 processes Secure_Path (Note that the algorithm in Section 5.2 processes Secure_Path
Segments in order from most recently added to least recently added, Segments in order from most recently added to least recently added,
therefore this special case will apply to the first Secure_Path therefore this special case will apply to the first Secure_Path
segment that the algorithm encounters that has the Confed_Segment segment that the algorithm encounters that has the Confed_Segment
flag set to one.) flag set to zero.)
Finally, as discussed above, an AS confederation may optionally Finally, as discussed above, an AS confederation may optionally
decide that its members will not verify digital signatures added by decide that its members will not verify digital signatures added by
members. In such a federation, when a confederation member runs the members. In such a federation, when a confederation member runs the
algorithm in Section 5.2, when processing a Signature_Segment, the algorithm in Section 5.2, when processing a Signature_Segment, the
confederation member first checks whether the Confed_Sequence flag in confederation member first checks whether the Confed_Sequence flag in
the corresponding Secure_Path segment is set to one. If the the corresponding Secure_Path segment is set to one. If the
Confed_Sequence flag is set to one in the corresponding Secure_Path Confed_Sequence flag is set to one in the corresponding Secure_Path
segment, the confederation member does not perform any further checks segment, the confederation member does not perform any further checks
on the Signature_Segment and immediately moves on to the next on the Signature_Segment and immediately moves on to the next
skipping to change at page 22, line 36 skipping to change at page 20, line 17
segment with the Confed_Sequence flag set to one from a peer who is segment with the Confed_Sequence flag set to one from a peer who is
not a member of the same AS confederation. (Such an error is treated not a member of the same AS confederation. (Such an error is treated
in exactly the same way as receipt of a non-BGPSEC update message in exactly the same way as receipt of a non-BGPSEC update message
containing an AS_CONFED_SEQUENCE from a peer that is not a member of containing an AS_CONFED_SEQUENCE from a peer that is not a member of
the same AS confederation.) the same AS confederation.)
4.4. Reconstructing the AS_PATH Attribute 4.4. Reconstructing the AS_PATH Attribute
BGPSEC update messages do not contain the AS_PATH attribute. Note, BGPSEC update messages do not contain the AS_PATH attribute. Note,
however, that the AS_PATH attribute can be reconstructed from the however, that the AS_PATH attribute can be reconstructed from the
BGPSEC_Path_Signatures attribute. This is necessary in the case BGPSEC_Path attribute. This is necessary in the case where a route
where a route advertisement is received via a BGPSEC update message advertisement is received via a BGPSEC update message and then
and then propagated to a peer via a non-BGPSEC update message. There propagated to a peer via a non-BGPSEC update message. There may be
may be additional cases where an implementation finds it useful to additional cases where an implementation finds it useful to perform
perform this reconstruction. this reconstruction.
The AS_PATH attribute can be constructed from the The AS_PATH attribute can be constructed from the BGPSEC_Path
BGPSEC_Path_Signatures attribute as follows. Starting with an empty attribute as follows. Starting with an empty AS_PATH attribute,
AS_PATH attribute, process the Secure_Path segments in order from process the Secure_Path segments in order from least-recently added
least-recently added (corresponding to the origin) to most-recently (corresponding to the origin) to most-recently added. For each
added. For each Secure_Path segment perform the following steps: Secure_Path segment perform the following steps:
1. If the Confed_Segment flag in the Secure_Path segment is set to 1. If the Confed_Segment flag in the Secure_Path segment is set to
one, then look at the most-recently added segment in the AS_PATH. one, then look at the most-recently added segment in the AS_PATH.
* In the case where the AS_PATH is empty or in the case where * In the case where the AS_PATH is empty or in the case where
the most-recently added segment is of type AS_SEQUENCE then the most-recently added segment is of type AS_SEQUENCE then
add (prepend to the AS_PATH) a new AS_PATH segment of type add (prepend to the AS_PATH) a new AS_PATH segment of type
AS_CONFED_SEQUENCE. This segment of type AS_CONFED_SEQUENCE AS_CONFED_SEQUENCE. This segment of type AS_CONFED_SEQUENCE
shall contain a number of elements equal to the pCount field shall contain a number of elements equal to the pCount field
in the current Secure_Path segment. Each of these elements in the current Secure_Path segment. Each of these elements
shall be the AS number contained in the current Secure_Path shall be the AS number contained in the current Secure_Path
segment. (That is, if the pCount field is X, then the segment segment. (That is, if the pCount field is X, then the segment
of type AS_CONFED_SEQUENCE contains X copies of the of type AS_CONFED_SEQUENCE contains X copies of the
Secure_Path segment's AS Number field.) Secure_Path segment's AS Number field.)
* In the case where the most recently added segment in the * In the case where the most-recently added segment in the
AS_PATH is of type AS_CONFED_SEQUENCE then add (prepend to the AS_PATH is of type AS_CONFED_SEQUENCE then add (prepend to the
segment) a number of elements equal to the pCount field in the segment) a number of elements equal to the pCount field in the
current Secure_Path segment. The value of each of these current Secure_Path segment. The value of each of these
elements shall be the AS number contained in the current elements shall be the AS number contained in the current
Secure_Path segment. (That is, if the pCount field is X, then Secure_Path segment. (That is, if the pCount field is X, then
add X copies of the Secure_Path segment's AS Number field to add X copies of the Secure_Path segment's AS Number field to
the existing AS_CONFED_SEQUENCE.) the existing AS_CONFED_SEQUENCE.)
2. If the Confed_Segment flag in the Secure_Path segment is set to 2. If the Confed_Segment flag in the Secure_Path segment is set to
zero, then look at the most-recently added segment in the zero, then look at the most-recently added segment in the
AS_PATH. AS_PATH.
* In the case where the AS_PATH is empty then add (prepend to * In the case where the AS_PATH is empty, and the pCount field
the AS_PATH) a new AS_PATH segment of type AS_SEQUENCE. This in the Secure_Path segment is greater than zero, add (prepend
segment of type AS_SEQUENCE shall contain a number of elements to the AS_PATH) a new AS_PATH segment of type AS_SEQUENCE.
equal to the pCount field in the current Secure_Path segment. This segment of type AS_SEQUENCE shall contain a number of
Each of these elements shall be the AS number contained in the elements equal to the pCount field in the current Secure_Path
current Secure_Path segment. (That is, if the pCount field is segment. Each of these elements shall be the AS number
X, then the segment of type AS_SEQUENCE contains X copies of contained in the current Secure_Path segment. (That is, if
the Secure_Path segment's AS Number field.) the pCount field is X, then the segment of type AS_SEQUENCE
contains X copies of the Secure_Path segment's AS Number
field.)
* In the case where the most recently added segment in the * In the case where the most recently added segment in the
AS_PATH is of type AS_SEQUENCE then add (prepend to the AS_PATH is of type AS_SEQUENCE then add (prepend to the
segment) a number of elements equal to the pCount field in the segment) a number of elements equal to the pCount field in the
current Secure_Path segment. The value of each of these current Secure_Path segment. The value of each of these
elements shall be the AS number contained in the current elements shall be the AS number contained in the current
Secure_Path segment. (That is, if the pCount field is X, then Secure_Path segment. (That is, if the pCount field is X, then
add X copies of the Secure_Path segment's AS Number field to add X copies of the Secure_Path segment's AS Number field to
the existing AS_SEQUENCE.) the existing AS_SEQUENCE.)
5. Processing a Received BGPSEC Update 5. Processing a Received BGPSEC Update
Upon receiving a BGPSEC update message from an external (eBGP) peer, Upon receiving a BGPSEC update message from an external (eBGP) peer,
a BGPSEC speaker SHOULD validate the message to determine the a BGPSEC speaker SHOULD validate the message to determine the
authenticity of the AS PATH information contained in the authenticity of the path information contained in the BGPSEC_Path
BGPSEC_Path_Signatures attribute. Section 5.1 provides an overview attribute. Section 5.1 provides an overview of BGPSEC validation and
of BGPSEC validation and Section 5.2 provides a specific algorithm Section 5.2 provides a specific algorithm for performing such
for performing such validation. (Note that an implementation need validation. (Note that an implementation need not follow the
not follow the specific algorithm in Section 5.2 as long as the input specific algorithm in Section 5.2 as long as the input/output
output behavior of the validation is identical to that of the behavior of the validation is identical to that of the algorithm in
algorithm in Section 5.2.) During exceptional conditions (e.g., the Section 5.2.) During exceptional conditions (e.g., the BGPSEC
BGPSEC speaker receives an incredibly large number of update messages speaker receives an incredibly large number of update messages at
at once) a BGPSEC speaker MAY defer validation of incoming BGPSEC once) a BGPSEC speaker MAY temporarily defer validation of incoming
update messages. The treatment of such BGPSEC update messages, whose BGPSEC update messages. The treatment of such BGPSEC update
validation has been deferred, is a matter of local policy. messages, whose validation has been deferred, is a matter of local
Implementations that support such deferment of validation MUST policy.
perform validation of these messages as soon as possible (i.e., as
soon as resources are available to perform validation) and MUST re- The validity of BGPSEC update messages is a function of the current
run best path selection once the validation status of such update RPKI state. When a BGPSEC speaker learns that RPKI state has changed
messages is known. (e.g., from an RPKI validating cache via the RTR protocol), the
BGPSEC speaker MUST re-run validation on all affected update messages
stored in its ADJ-RIB-IN. That is, when a given RPKI certificate
ceases to be valid (e.g., it expires or revoked), all update messages
containing a signature whose SKI matches the SKI in the given
certificate must be re-assessed to determine if they are still valid.
Note that this reassessment determines that the validity state of an
update has changed then, depending on local policy, it may be
necessary to re-run best path selection.
BGPSEC update messages do not contain an AS_PATH attribute. BGPSEC update messages do not contain an AS_PATH attribute.
Therefore, a BGPSEC speaker MUST utilize the AS path information in Therefore, a BGPSEC speaker MUST utilize the AS path information in
the BGPSEC_Path_Signatures attribute in all cases where it would the BGPSEC_Path attribute in all cases where it would otherwise use
otherwise use the AS path information in the AS_PATH attribute. The the AS path information in the AS_PATH attribute. The only exception
only exception to this rule is when AS path information must be to this rule is when AS path information must be updated in order to
updated in order to propagate a route to a peer (in which case the propagate a route to a peer (in which case the BGPSEC speaker follows
BGPSEC speaker follows the instructions in Section 4). Section 4.4 the instructions in Section 4). Section 4.4 provides an algorithm
provides an algorithm for constructing an AS_PATH attribute from a for constructing an AS_PATH attribute from a BGPSEC_Path attribute.
BGPSEC_Path_Signatures attribute. Whenever the use of AS path Whenever the use of AS path information is called for (e.g., loop
information is called for (e.g., loop detection, or use of AS path detection, or use of AS path length in best path selection) the
length in best path selection) the externally visible behavior of the externally visible behavior of the implementation shall be the same
implementation shall be the same as if the implementation had run the as if the implementation had run the algorithm in Section 4.4 and
algorithm in Section 4.4 and used the resulting AS_PATH attribute as used the resulting AS_PATH attribute as it would for a non-BGPSEC
it would for a non-BGPSEC update message. However, in practice, it update message.
is expected that most implementations will not actually run the
algorithm from Section 4.4, and will instead transform the
BGPSEC_Path_Signatures attribute directly into some internal
representation of AS path.
Many signature algorithms are non-deterministic. That is, many Many signature algorithms are non-deterministic. That is, many
signature algorithms will produce different signatures each time they signature algorithms will produce different signatures each time they
are run (even when they are signing the same data with the same key). are run (even when they are signing the same data with the same key).
Therefore, if an implementation receives a BGPSEC update from a peer Therefore, if an implementation receives a BGPSEC update from a peer
and later receives a second BGPSEC update message from the same peer, and later receives a second BGPSEC update message from the same peer,
the implementation SHOULD treat the second message as a duplicate the implementation SHOULD treat the second message as a duplicate
update message if it differs from the first update message only in update message if it differs from the first update message only in
the Signature fields (within the BGPSEC_Path_Signatures attribute). the Signature fields (within the BGPSEC_Path attribute). That is, if
That is, if all the fields in the second update are identical to the all the fields in the second update are identical to the fields in
fields in the first update message, except for the Signature fields, the first update message, except for the Signature fields, then the
then the second update message should be treated as a duplicate of second update message should be treated as a duplicate of the first
the first update message. Note that if other fields (e.g., the update message. Note that if other fields (e.g., the Subject Key
Subject Key Identifier field) within a Signature segment differ Identifier field) within a Signature segment differ between two
between two update messages then the two updates are not duplicates. update messages then the two updates are not duplicates.
With regards to the processing of duplicate update messages, if the With regards to the processing of duplicate update messages, if the
first update message is valid, then an implementation SHOULD NOT run first update message is valid, then an implementation SHOULD NOT run
the validation procedure on the second, duplicate update message the validation procedure on the second, duplicate update message
(even if the bits of the signature field are different). If the (even if the bits of the signature field are different). If the
first update message is not valid, then an implementation SHOULD run first update message is not valid, then an implementation SHOULD run
the validation procedure on the second duplicate update message (as the validation procedure on the second duplicate update message (as
the signatures in the second update may be valid even though the the signatures in the second update may be valid even though the
first contained a signature that was invalid). first contained a signature that was invalid).
5.1. Overview of BGPSEC Validation 5.1. Overview of BGPSEC Validation
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
BGPSEC_Path_Signatures attribute, it is necessary that the recipient attribute, it is necessary that the recipient have access to the
have access to the following data obtained from valid RPKI 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 router 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. (For example,
case in analogous to the use of the RPKI-RTR protocol [13] for origin the trusted cache could deliver the necessary validity information to
validation.) the BGPSEC speaker using the router key PDU [15]for the RTR protocol
[14].)
To validate a BGPSEC update message containing the To validate a BGPSEC update message containing the BGPSEC_Path
BGPSEC_Path_Signatures attribute, the recipient performs the attribute, the recipient performs the validation steps specified in
validation steps specified in Section 5.2. The validation procedure Section 5.2. The validation procedure results in one of two states:
results in one of two states: 'Good' and 'Not Good'. 'Valid' and 'Not Valid'.
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
matter of local policy, and shall be handled using existing local matter of local policy, and shall be handled using local policy
policy mechanisms. It is expected that BGP peers will generally mechanisms. It is expected that BGP peers will generally prefer
prefer routes received via 'Good' BGPSEC update messages over routes routes received via 'Valid' BGPSEC update messages over routes
received via 'Not Good' BGPSEC update messages as well as routes received via 'Not Valid' BGPSEC update messages as well as routes
received via update messages that do not contain the received via update messages that do not contain the BGPSEC_Path
BGPSEC_Path_Signatures attribute. However, BGPSEC specifies no attribute. However, BGPSEC specifies no changes to the BGP decision
changes to the BGP decision process and leaves to the operator the process. (See [16] for related operational considerations.)
selection of an appropriate policy mechanism to achieve the
operator's desired results within the BGP decision process.
BGPSEC validation needs only be performed at eBGP edge. The BGPSEC validation needs only be performed at eBGP edge. The
validation status of a BGP signed/unsigned update MAY be conveyed via validation status of a BGP signed/unsigned update MAY be conveyed via
iBGP from an ingress edge router to an egress edge router. Local iBGP from an ingress edge router to an egress edge router via some
policy in the AS determines the specific means for conveying the mechanism, according to local policy within an AS. As discussed in
validation status through various pre-existing mechanisms (e.g., Section 4, when a BGPSEC speaker chooses to forward a (syntactically
modifying an attribute). As discussed in Section 4, when a BGPSEC correct) BGPSEC update message, it SHOULD be forwarded with its
speaker chooses to forward a (syntactically correct) BGPSEC update BGPSEC_Path attribute intact (regardless of the validation state of
message, it SHOULD be forwarded with its BGPSEC_Path_Signatures the update message). Based entirely on local policy, an egress
attribute intact (regardless of the validation state of the update router receiving a BGPSEC update message from within its own AS MAY
message). Based entirely on local policy settings, an egress router choose to perform its own validation.
MAY trust the validation status conveyed by an ingress router or it
MAY perform its own validation.
5.2. Validation Algorithm 5.2. 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 a 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
behavior of this algorithm. externally visible 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:
1. Check to ensure that the entire BGPSEC_Path_Signatures attribute 1. Check to ensure that the entire BGPSEC_Path attribute is
is syntactically correct (conforms to the specification in this syntactically correct (conforms to the specification in this
document). document).
2. Check that each Signature_Block contains one Signature segment 2. Check that each Signature_Block contains one Signature segment
for each Secure_Path segment in the Secure_Path portion of the for each Secure_Path segment in the Secure_Path portion of the
BGPSEC_Path_Signatures attribute. (Note that the entirety of BGPSEC_Path attribute. (Note that the entirety of each
each Signature_Block must be checked to ensure that it is well Signature_Block must be checked to ensure that it is well formed,
formed, even though the validation process may terminate before even though the validation process may terminate before all
all signatures are cryptographically verified.) signatures are cryptographically verified.)
3. Check that the update message does not contain both a 3. Check that the update message does not contain an AS_PATH
BGPSEC_Path_Signatures attribute and an AS_PATH attribute. attribute.
4. If the update message was received from a peer that is not a 4. If the update message was received from a peer that is not a
member of the BGPSEC speaker's AS confederation, check to ensure member of the BGPSEC speaker's AS confederation, check to ensure
that none of the Secure_Path segments contain a Flags field with that none of the Secure_Path segments contain a Flags field with
the Confed_Sequence flag set to one. the Confed_Sequence flag set to one.
5. If the update message was received from a peer that is not 5. If the update message was received from a peer that is not
expected to set pCount equal to zero (see Section 4.2) then check expected to set pCount equal to zero (see Section 4.2) then check
to ensure that the pCount field in the most-recently added to ensure that the pCount field in the most-recently added
Secure_Path segment is not equal to zero. Secure_Path segment is not equal to zero.
If there are two Signature_Blocks within the BGPSEC_Path_Signatures If any of these checks identify an error in the BGPSEC_Path
attribute and one of them is poorly formed (or contains the wrong attribute, then the implementation should notify the operator that an
number of Signature segments) , then the recipient should log that an error has occurred and treat the update in a manner consistent with
error occurred, strip off that particular Signature_Block and process other BGP errors (i.e., following RFC 4271[2] or any future updates
the update message as though it arrived with a single to that document).
Signature_Block. If the BGPSEC_Path_Signatures attribute contains an
error that is not local to one of two Signature_Blocks, then the
recipient should log that an error occurred and drop the update
message containing the error. (In particular, if any of checks 3-5
above fail, the recipient should log that an error occurred and drop
the update message containing the error.)
Next, the BGPSEC speaker verifies that the origin AS is authorized to Next, the BGPSEC speaker verifies that the origin AS is authorized to
advertise the prefix in question. To do this, consult the valid ROA advertise the prefix in question. To do this, consult the valid ROA
data to obtain a list of AS numbers that are associated with the data to obtain a list of AS numbers that are associated with the
given IP address prefix in the update message. Then locate the last given IP address prefix in the update message. Then locate the last
(least recently added) AS number in the Secure_Path portion of the (least recently added) AS number in the Secure_Path portion of the
BGPSEC_Path_Signatures attribute. If the origin AS in the BGPSEC_Path attribute. If the origin AS in the Secure_Path is not in
Secure_Path is not in the set of AS numbers associated with the given the set of AS numbers associated with the given prefix, then the
prefix, then the BGPSEC update message is 'Not Good' and the BGPSEC update message is 'Not Valid' and the validation algorithm
validation algorithm terminates. terminates.
Finally, the BGPSEC speaker examines the Signature_Blocks in the Finally, the BGPSEC speaker examines the Signature_Blocks in the
BGPSEC_Path_Signatures attribute. A Signature_Block corresponding to BGPSEC_Path attribute. A Signature_Block corresponding to an
an algorithm suite that the BGPSEC speaker does not support is not algorithm suite that the BGPSEC speaker does not support is not
considered in validation. If there does not exist a Signature_Block considered in validation. If there does not exist a Signature_Block
corresponding to an algorithm suite that the BGPSEC speaker supports, corresponding to an algorithm suite that the BGPSEC speaker supports,
then the BGPSEC speaker MUST treat the update message in the same then the BGPSEC speaker MUST treat the update message in the same
manner that the BGPSEC speaker would treat an (unsigned) update manner that the BGPSEC speaker would treat an (unsigned) update
message that arrived without a BGPSEC_Path_Signatures attribute. message that arrived without a BGPSEC_Path attribute.
For each remaining Signature_Block (corresponding to an algorithm For each remaining Signature_Block (corresponding to an algorithm
suite supported by the BGPSEC speaker), the BGPSEC speaker iterates suite supported by the BGPSEC speaker), the BGPSEC speaker iterates
through the Signature segments in the Signature_Block, starting with through the Signature segments in the Signature_Block, starting with
the most recently added segment (and concluding with the least the most recently added segment (and concluding with the least
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 attribute. The following steps make use of
make use of this correspondence. 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 router 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 there 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 this check finds no such matching SKI value, then segment. If this check finds no such matching SKI value, then
mark the entire Signature-List Block as 'Not Good' and proceed to mark the entire Signature_Block as 'Not Valid' and proceed to the
the next Signature-List Block. next Signature_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
+-------------------------------------------+ +-------------------------------------------+
skipping to change at page 29, line 11 skipping to change at page 27, line 6
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) |
+------------------------------------+ +------------------------------------+
| Origin AS Number (4 octets) | ---\ | Origin AS Number (4 octets) | ---\
+------------------------------------+ \ +------------------------------------+ \
| pCount (1 octet) | > Secure_Path | pCount (1 octet) | > Secure_Path
+------------------------------------+ / +------------------------------------+ /
| Flags (1 octet) | ---/ | Flags (1 octet) | ---/
+------------------------------------+ +------------------------------------+
| Info Type (1 octet) | ---\ | Algorithm Suite Id. (1 octet) |
+------------------------------------+ \ +------------------------------------+
| Info Length (1 octet) | > Additional_Info | NLRI Length (1 octet) |
+------------------------------------+ / +------------------------------------+
| Info Value (variable) | ---/ | NLRI Prefix (variable) |
+------------------------------------+ +------------------------------------+
| Algorithm Suite Id. (1 octet) |
+------------------------------------+
| NLRI Length (1 octet) |
+------------------------------------+
| NLRI Prefix (variable) |
+------------------------------------+
The NLRI Length, NLRI Prefix, Additional_Info, and Algorithm Suite The NLRI Length, NLRI Prefix, and Algorithm Suite Identifier are all
Identifier are all obtained in a straight forward manner from the obtained in a straight forward manner from the NLRI of the update
NLRI of the update message or the BGPSEC_Path_Signatures attribute message or the BGPSEC_Path attribute being validated. The Origin AS
being validated. The Origin AS Number, pCount, and Flags fields are Number, pCount, and Flags fields are taken from the Secure_Path
taken from the Secure_Path segment corresponding to the Signature segment corresponding to the Signature Segment currently being
Segment currently being processed. 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_Block as 'Not
'Not Good' and proceed to the next Signature_Block. If the Valid' and proceed to the next Signature_Block. If the signature
signature validation algorithm determines that the signature is validation algorithm determines that the signature is valid, then
valid, then continue processing Signature-Segments (within the continue processing Signature Segments (within the current
current Signature-List Block). Signature_Block).
If all Signature-Segments within a Signature-List Block pass If all Signature Segments within a Signature_Block pass validation
validation (i.e., all segments are processed and the Signature-List (i.e., all segments are processed and the Signature_Block has not yet
Block has not yet been marked 'Not Good'), then the Signature_Block been marked 'Not Valid'), then the Signature_Block is marked as
is marked as 'Good'. 'Valid'.
If at least one Signature_Block is marked as 'Good', then the If at least one Signature_Block is marked as 'Valid', then the
validation algorithm terminates and the BGPSEC update message is validation algorithm terminates and the BGPSEC update message is
deemed to be 'Good'. (That is, if a BGPSEC update message contains deemed to be 'Valid'. (That is, if a BGPSEC update message contains
two Signature_Blocks then the update message is deemed 'Good' if the two Signature_Blocks then the update message is deemed 'Valid' if the
first Signature_Block is marked 'Good' OR the second Signature_Block first Signature_Block is marked 'Valid' OR the second Signature_Block
is marked 'Good'.) is marked 'Valid'.)
6. Algorithms and Extensibility 6. Algorithms and Extensibility
6.1. Algorithm Suite Considerations 6.1. Algorithm Suite Considerations
Note that there is currently no support for bilateral negotiation Note that there is currently no support for bilateral negotiation
between BGPSEC peers to use of a particular (digest and signature) between BGPSEC peers to use of a particular (digest and signature)
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 [12]. Additionally, the document specifies an by all BGPSEC speakers [11].
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 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 a '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 attribute can contain signatures, in parallel,
parallel, for two algorithm suites.) Once the transition is for two algorithm suites.) Once the transition is complete, use of
complete, use of the old 'current' algorithm will be deprecated, use the old 'current' algorithm will be deprecated, use of the 'new'
of the 'new' algorithm will be mandatory, and a subsequent 'even algorithm will be mandatory, and a subsequent 'even newer' algorithm
newer' algorithm suite may be specified as recommend to implement. suite may be specified as recommend to implement. Once the
Once the transition has successfully been completed in this manner, transition has successfully been completed in this manner, BGPSEC
BGPSEC speakers SHOULD include only a single Signature_Block speakers SHOULD include only a single Signature_Block (corresponding
(corresponding to the 'new' algorithm). to the 'new' algorithm).
6.2. Extensibility Considerations 6.2. Extensibility Considerations
This section discusses potential changes to BGPSEC that would require This section discusses potential changes to BGPSEC that would require
substantial changes to the processing of the BGPSEC_Path_Signatures substantial changes to the processing of the BGPSEC_Path and thus
and thus necessitate a new version of BGPSEC. Examples of such necessitate a new version of BGPSEC. Examples of such changes
changes include: include:
o A new type of signature algorithm that produces signatures of o A new type of signature algorithm that produces signatures of
variable length variable length
o A new type of signature algorithm for which the number of o A new type of signature algorithm for which the number of
signatures in the Signature_Block is not equal to the number of signatures in the Signature_Block is not equal to the number of
ASes in the Secure_Path (e.g., aggregate signatures) ASes in the Secure_Path (e.g., aggregate signatures)
o Changes to the data that is protected by the BGPSEC signatures o Changes to the data that is protected by the BGPSEC signatures
(e.g., attributes other than the AS path) (e.g., attributes other than the AS path)
In the case that such a change to BGPSEC were deemed desirable, it is In the case that such a change to BGPSEC were deemed desirable, it is
expected that a subsequent version of BGPSEC would be created and expected that a subsequent version of BGPSEC would be created and
that this version of BGPSEC would specify a new BGP Path Attribute, that this version of BGPSEC would specify a new BGP path attribute,
let's call it BGPSEC_PATH_SIG_TWO, which is designed to accommodate let's call it BGPSEC_PATH_TWO, which is designed to accommodate the
the desired changes to BGPSEC. In such a case, the mandatory desired changes to BGPSEC. In such a case, the mandatory algorithm
algorithm suites document would be updated to specify algorithm suites document would be updated to specify algorithm suites
suites appropriate for the new version of BGPSEC. appropriate for the new version of BGPSEC.
At this point a transition would begin which is analogous to the At this point a transition would begin which is analogous to the
algorithm transition discussed in Section 6.2. During the transition algorithm transition discussed in Section 6.1. During the transition
period all BGPSEC speakers SHOULD simultaneously include both the period all BGPSEC speakers SHOULD simultaneously include both the
BGPSEC_PATH_SIGNATURES attribute and the new BGPSEC_PATH_SIG_TWO BGPSEC_PATH attribute and the new BGPSEC_PATH_TWO attribute. Once
attribute. Once the transition is complete, the use of the transition is complete, the use of BGPSEC_PATH could then be
BGPSEC_PATH_SIGNATURES could then be deprecated, at which point deprecated, at which point BGPSEC speakers SHOULD include only the
BGPSEC speakers SHOULD include only the new BGPSEC_PATH_SIG_TWO new BGPSEC_PATH_TWO attribute. Such a process could facilitate a
attribute. Such a process could facilitate a transition to a new transition to a new BGPSEC semantics in a backwards compatible
BGPSEC semantics in a backwards compatible fashion. 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 [10]. considerations, please see [13].
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, in the RPKI, by the IP address space holder to
advertisements for the given prefix. originate route advertisements for the given prefix.
o For each AS number in the AS Path, a BGPSEC speaker authorized by o For each AS in the path, a BGPSEC speaker authorized by the holder
the holder of the AS number intentionally chose (in accordance of the AS number intentionally chose (in accordance with local
with local policy) to propagate the route advertisement to the policy) to propagate the route advertisement to the subsequent AS
next AS in the Secure_Path. in the 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 portion of the BGPSEC_Path attribute corresponds
who have all agreed in principle to forward packets to the given to a sequence of autonomous systems who have all agreed in principle
prefix along the indicated path. (It should be noted that BGPSEC to forward packets to the given prefix along the indicated path. (It
does not offer a precise guarantee that the data packets would should be noted that BGPSEC does not offer any guarantee that the
propagate along the indicated path; it only guarantees that the BGP data packets would propagate along the indicated path; it only
update conveying the path indeed propagated along the indicated guarantees that the BGP update conveying the path indeed propagated
path.) Furthermore, the recipient is assured that this path along the indicated path.) Furthermore, the recipient is assured
terminates in an autonomous system that has been authorized by the IP that this path terminates in an autonomous system that has been
address space holder as a legitimate destination for traffic to the authorized by the IP address space holder as a legitimate destination
given prefix. 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
of update messages received from internal peers is a matter of local of update messages received from internal peers is a matter of local
policy, see Section 5). policy, see Section 5).
Note that there may be cases where a BGPSEC speaker deems 'Good' (as Note that there may be cases where a BGPSEC speaker deems 'Valid' (as
per the validation algorithm in Section 5.2) a BGPSEC update message per the validation algorithm in Section 5.2) a BGPSEC update message
that contains both a 'Good' and a 'Not Good' Signature_Block. That that contains both a 'Valid' and a 'Not Valid' Signature_Block. That
is, the update message contains two sets of signatures corresponding is, the update message contains two sets of signatures corresponding
to two algorithm suites, and one set of signatures verifies correctly to two algorithm suites, and one set of signatures verifies correctly
and the other set of signatures fails to verify. In this case, the and the other set of signatures fails to verify. In this case, the
protocol specifies that if the BGPSEC speaker propagates the route protocol specifies that if the BGPSEC speaker propagates the route
advertisement received in such an update message then the BGPSEC advertisement received in such an update message then the BGPSEC
speaker SHOULD add its signature to each of the Signature_Blocks speaker SHOULD add its signature to each of the Signature_Blocks
using both the corresponding algorithm suite. Thus the BGPSEC using both the corresponding algorithm suite. Thus the BGPSEC
speaker creates a signature using both algorithm suites and creates a speaker creates a signature using both algorithm suites and creates a
new update message that contains both the 'Good' and the 'Not Good' new update message that contains both the 'Valid' and the 'Not Valid'
set of signatures (from its own vantage point). set of signatures (from its own vantage point).
To understand the reason for such a design decision consider the case To understand the reason for such a design decision consider the case
where the BGPSEC speaker receives an update message with both a set where the BGPSEC speaker receives an update message with both a set
of algorithm A signatures which are 'Good' and a set of algorithm B of algorithm A signatures which are 'Valid' and a set of algorithm B
signatures which are 'Not Good'. In such a case it is possible signatures which are 'Not Valid'. In such a case it is possible
(perhaps even quite likely) that some of the BGPSEC speaker's peers (perhaps even quite likely) that some of the BGPSEC speaker's peers
(or other entities further 'downstream' in the BGP topology) do not (or other entities further 'downstream' in the BGP topology) do not
support algorithm A. Therefore, if the BGPSEC speaker were to remove support algorithm A. Therefore, if the BGPSEC speaker were to remove
the 'Not Good' set of signatures corresponding to algorithm B, such the 'Not Valid' set of signatures corresponding to algorithm B, such
entities would treat the message as though it were unsigned. By entities would treat the message as though it were unsigned. By
including the 'Not Good' set of signatures when propagating a route including the 'Not Valid' set of signatures when propagating a route
advertisement, the BGPSEC speaker ensures that 'downstream' entities advertisement, the BGPSEC speaker ensures that 'downstream' entities
have as much information as possible to make an informed opinion have as much information as possible to make an informed opinion
about the validation status of a BGPSEC update. about the validation status of a BGPSEC update.
Note also that during a period of partial BGPSEC deployment, a Note also that during a period of partial BGPSEC deployment, a
'downstream' entity might reasonably treat unsigned messages 'downstream' entity might reasonably treat unsigned messages
different from BGPSEC updates that contain a single set of 'Not Good' different from BGPSEC updates that contain a single set of 'Not
signatures. That is, by removing the set of 'Not Good' signatures Valid' signatures. That is, by removing the set of 'Not Valid'
the BGPSEC speaker might actually cause a downstream entity to signatures the BGPSEC speaker might actually cause a downstream
'upgrade' the status of a route advertisement from 'Not Good' to entity to 'upgrade' the status of a route advertisement from 'Not
unsigned. Finally, note that in the above scenario, the BGPSEC Valid' to unsigned. Finally, note that in the above scenario, the
speaker might have deemed algorithm A signatures 'Good' only because BGPSEC speaker might have deemed algorithm A signatures 'Valid' only
of some issue with RPKI state local to his AS (for example, his AS because of some issue with RPKI state local to his AS (for example,
might not yet have obtained a CRL indicating that a key used to his AS might not yet have obtained a CRL indicating that a key used
verify an algorithm A signature belongs to a newly revoked to verify an algorithm A signature belongs to a newly revoked
certificate). In such a case, it is highly desirable for a certificate). In such a case, it is highly desirable for a
downstream entity to treat the update as 'Not Good' (due to the downstream entity to treat the update as 'Not Valid' (due to the
revocation) and not as 'unsigned' (which would happen if the 'Not revocation) and not as 'unsigned' (which would happen if the 'Not
Good' Signature_Blocks were removed). Valid' Signature_Blocks were removed).
A similar argument applies to the case where a BGPSEC speaker (for A similar argument applies to the case where a BGPSEC speaker (for
some reason such as lack of viable alternatives) selects as his best some reason such as lack of viable alternatives) selects as his best
route to a given prefix a route obtained via a 'Not Good' BGPSEC route to a given prefix a route obtained via a 'Not Valid' BGPSEC
update message. (That is, a BGPSEC update containing only 'Not Good' update message. (That is, a BGPSEC update containing only 'Not
Signature-List Blocks.) In such a case, the BGPSEC speaker should Valid' Signature_Blocks.) In such a case, the BGPSEC speaker should
propagate a signed BGPSEC update message, adding his signature to the propagate a signed BGPSEC update message, adding his signature to the
'Not Good' signatures that already exist. Again, this is to ensure 'Not Valid' signatures that already exist. Again, this is to ensure
that 'downstream' entities are able to make an informed decision and that 'downstream' entities are able to make an informed decision and
not erroneously treat the route as unsigned. It may also be noted not erroneously treat the route as unsigned. It may also be noted
here that due to possible differences in RPKI data at different here that due to possible differences in RPKI data at different
vantage points in the network, a BGPSEC update that was deemed 'Not vantage points in the network, a BGPSEC update that was deemed 'Not
Good' at an upstream BGPSEC speaker may indeed be deemed 'Good' at Valid' at an upstream BGPSEC speaker may indeed be deemed 'Valid' at
another BGP speaker downstream. another BGP speaker downstream.
Therefore, it is important to note that when a BGPSEC speaker signs Therefore, it is important to note that when a BGPSEC speaker signs
an outgoing update message, it is not attesting to a belief that all an outgoing update message, it is not attesting to a belief that all
signatures prior to its are valid. Instead it is merely asserting signatures prior to its are valid. Instead it is merely asserting
that: that:
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
skipping to change at page 34, line 37 skipping to change at page 32, line 26
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
recipient of a BGPSEC update message in which an upstream entity that recipient of a BGPSEC update message in which an upstream entity that
is two or more hops away set pCount to zero is unable to verify for is two or more hops away set pCount to zero is unable to verify for
themselves whether pCount was set to zero legitimately. themselves whether pCount was set to zero legitimately.
Finally, BGPSEC does not provide protection against all attacks at Finally, BGPSEC does not provide protection against attacks at the
the transport layer. An adversary on the path between a BGPSEC transport layer. An adversary on the path between a BGPSEC speaker
speaker and its peer is able to perform attacks such as modifying and its peer is able to perform attacks such as modifying valid
valid BGPSEC updates to cause them to fail validation, injecting BGPSEC updates to cause them to fail validation, injecting (unsigned)
(unsigned) BGP update messages without BGPSEC_Path_Signature BGP update messages without BGPSEC_Path_Signature attributes, or
attributes, or injecting BGPSEC update messages with injecting BGPSEC update messages with BGPSEC_Path_Signature
BGPSEC_Path_Signature attributes that fail validation, or causing the attributes that fail validation, or causing the peer to tear-down the
peer to tear-down the BGP session. Therefore, BGPSEC implementations BGP session. Therefore, BGPSEC sessions SHOULD be protected by
MUST support appropriate transport security mechanisms. appropriate transport security mechanisms.
EDITOR'S NOTE: Do we want to mandate a specific transport security 8. IANA Considerations
mechanism (e.g., TCP-AO)?
8. Contributors TBD: Need IANA to assign numbers for the two capabilities and the
BGPSEC_PATH attribute.
8.1. Authors This document does not create any new IANA registries.
9. Contributors
9.1. Authors
Rob Austein Rob Austein
Dragon Research Labs Dragon Research Labs
sra@hactrn.net sra@hactrn.net
Steven Bellovin Steven Bellovin
Columbia University Columbia University
smb@cs.columbia.edu smb@cs.columbia.edu
Randy Bush Randy Bush
Internet Initiative Japan Internet Initiative Japan
randy@psg.com randy@psg.com
Russ Housley Russ Housley
Vigil Security Vigil Security
skipping to change at page 36, line 4 skipping to change at page 33, line 35
Google Google
warren@kumari.net warren@kumari.net
Doug Montgomery Doug Montgomery
USA National Institute of Standards and Technology USA National Institute of Standards and Technology
dougm@nist.gov dougm@nist.gov
Kotikalapudi Sriram Kotikalapudi Sriram
USA National Institute of Standards and Technology USA National Institute of Standards and Technology
kotikalapudi.sriram@nist.gov kotikalapudi.sriram@nist.gov
Samuel Weiler Samuel Weiler
Cobham Sparta
weiler+ietf@watson.org weiler+ietf@watson.org
8.2. Acknowledgements 9.2. Acknowledgements
The authors would like to thank Luke Berndt, Sharon Goldberg, Ed The authors would like to thank Luke Berndt, Sharon Goldberg, Ed
Kern, Chris Morrow, Doug Maughan, Pradosh Mohapatra, Russ Mundy, Kern, Chris Morrow, Doug Maughan, Pradosh Mohapatra, Russ Mundy,
Sandy Murphy, Keyur Patel, Mark Reynolds, Heather Schiller, Jason Sandy Murphy, Keyur Patel, Mark Reynolds, Heather Schiller, Jason
Schiller, John Scudder, Ruediger Volk and David Ward for their Schiller, John Scudder, Ruediger Volk and David Ward for their
valuable input and review. valuable input and review.
9. References 10. Normative References
[1] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] 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, [3] 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] Traina, P., McPherson, D., and J. Scudder, "Autonomous System [4] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS Number
Space", RFC 4893, May 2007.
[5] Traina, P., McPherson, D., and J. Scudder, "Autonomous System
Confederations for BGP", RFC 5065, August 2007. Confederations for BGP", RFC 5065, August 2007.
[4] Scudder, J. and R. Chandra, "Capabilities Advertisement with [6] Scudder, J. and R. Chandra, "Capabilities Advertisement with
BGP-4", RFC 5492, February 2009. BGP-4", RFC 5492, February 2009.
[5] Kumari, W. and K. Sriram, "Recommendation for Not Using AS_SET [7] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure
and AS_CONFED_SET in BGP", RFC 6472, December 2011.
[6] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure
Internet Routing", RFC 6480, February 2012. Internet Routing", RFC 6480, February 2012.
[7] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route [8] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)", RFC 6482, February 2012. Origin Authorizations (ROAs)", RFC 6482, February 2012.
[8] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[9] Patel, K., Ward, D., and R. Bush, "Extended Message support for [9] Patel, K., Ward, D., and R. Bush, "Extended Message support for
BGP", draft-ietf-idr-bgp-extended-messages, July 2012. BGP", July 2012.
[10] Kent, S., and A. Chi, "Threat Model for BGP Path Security",
draft-ietf-sidr-bgpsec-threats-02, February 2012.
[11] Reynolds, M., Turner, S., and S. Kent, "A Profile for BGPSEC [10] 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", Certification Requests", April 2012.
draft-ietf-sidr-bgpsec-pki-profiles-03, April 2012.
[12] Turner, S., "BGP Algorithms, Key Formats, & Signature Formats", [11] Turner, S., "BGP Algorithms, Key Formats, & Signature Formats",
draft-ietf-sidr-bgpsec-algs-02, March 2012. March 2012.
[13] Bush, R. and R. Austein, "The RPKI/Router Protocol", 11. Informative References
draft-ietf-sidr-rtr-26, February 2012.
[12] Kumari, W. and K. Sriram, "Recommendation for Not Using AS_SET
and AS_CONFED_SET in BGP", RFC 6472, December 2011.
[13] Kent, S., "Threat Model for BGP Path Security", February 2012.
[14] Bush, R. and R. Austein, "The RPKI/Router Protocol",
February 2012.
[15] Bush, R., Patel, K., and S. Turner, "Router Key PDU for RPKI-
Router Protocol", October 2012.
[16] Bush, R., "BGPsec Operational Considerations", May 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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