draft-ietf-sidr-bgpsec-protocol-10.txt   draft-ietf-sidr-bgpsec-protocol-11.txt 
Network Working Group M. Lepinski, Ed. Network Working Group M. Lepinski, Ed.
Internet-Draft BBN Internet-Draft BBN
Intended status: Standards Track October 27, 2014 Intended status: Standards Track January 19, 2015
Expires: April 27, 2015 Expires: July 19, 2015, 2015
BGPSEC Protocol Specification BGPsec Protocol Specification
draft-ietf-sidr-bgpsec-protocol-10 draft-ietf-sidr-bgpsec-protocol-11
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 path of autonomous Protocol (BGP) that provides security for the path of autonomous
systems through which a BGP update message passes. BGPSEC is systems through which a BGP update message passes. BGPsec is
implemented via a new optional non-transitive BGP path attribute that implemented via a new optional non-transitive BGP path attribute that
carries a digital signature produced by each autonomous system that carries a digital signature produced by each autonomous system that
propagates the update message. 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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" are to be interpreted as described in RFC 2119 [1] only "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 when they appear in all upper case. They may also appear in lower or
skipping to change at page 2, line 18 skipping to change at page 2, line 18
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BGPSEC Negotiation . . . . . . . . . . . . . . . . . . . . . . 3 2. BGPsec Negotiation . . . . . . . . . . . . . . . . . . . . . . 3
2.1. The BGPSEC Capability . . . . . . . . . . . . . . . . . . 3 2.1. The BGPsec Capability . . . . . . . . . . . . . . . . . . 3
2.2. Negotiating BGPSEC Support . . . . . . . . . . . . . . . . 4 2.2. Negotiating BGPsec Support . . . . . . . . . . . . . . . . 4
3. The BGPSEC_Path Attribute . . . . . . . . . . . . . . . . . . 5 3. The BGPsec_Path Attribute . . . . . . . . . . . . . . . . . . 5
3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Signature_Block . . . . . . . . . . . . . . . . . . . . . 8 3.2. Signature_Block . . . . . . . . . . . . . . . . . . . . . 8
4. Generating a BGPSEC Update . . . . . . . . . . . . . . . . . . 10 4. Generating a BGPsec Update . . . . . . . . . . . . . . . . . . 10
4.1. Originating a New BGPSEC Update . . . . . . . . . . . . . 11 4.1. Originating a New BGPsec Update . . . . . . . . . . . . . 11
4.2. Propagating a Route Advertisement . . . . . . . . . . . . 13 4.2. Propagating a Route Advertisement . . . . . . . . . . . . 13
4.3. Processing Instructions for Confederation Members . . . . 17 4.3. Processing Instructions for Confederation Members . . . . 17
4.4. Reconstructing the AS_PATH Attribute . . . . . . . . . . . 19 4.4. Reconstructing the AS_PATH Attribute . . . . . . . . . . . 19
5. Processing a Received BGPSEC Update . . . . . . . . . . . . . 20 5. Processing a Received BGPsec Update . . . . . . . . . . . . . 20
5.1. Overview of BGPSEC Validation . . . . . . . . . . . . . . 22 5.1. Overview of BGPsec Validation . . . . . . . . . . . . . . 22
5.2. Validation Algorithm . . . . . . . . . . . . . . . . . . . 23 5.2. Validation Algorithm . . . . . . . . . . . . . . . . . . . 23
6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 27 6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 27
6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 27 6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 27
6.2. Extensibility Considerations . . . . . . . . . . . . . . . 27 6.2. Extensibility Considerations . . . . . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28 7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
7.1 Security Guarantees . . . . . . . . . . . . . . . . . . . . 28 7.1 Security Guarantees . . . . . . . . . . . . . . . . . . . . 28
7.2 On the Removal of BGPSEC Signatures . . . . . . . . . . . . 29 7.2 On the Removal of BGPsec Signatures . . . . . . . . . . . . 29
7.3 Mitigation of Denial of Service Attacks . . . . . . . . . . 30 7.3 Mitigation of Denial of Service Attacks . . . . . . . . . . 30
7.4 Additional Security Considerations . . . . . . . . . . . . . 31 7.4 Additional Security Considerations . . . . . . . . . . . . . 31
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 32 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 32 9.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 32
10. Normative References . . . . . . . . . . . . . . . . . . . . 33 10. Normative References . . . . . . . . . . . . . . . . . . . . 33
11. Informative References . . . . . . . . . . . . . . . . . . . 33 11. Informative References . . . . . . . . . . . . . . . . . . . 33
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 34 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 34
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) [2] 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
property: Every AS on the path of ASes listed in the update message property: Every AS on the path of ASes listed in the update message
has explicitly authorized the advertisement of the route to the has explicitly authorized the advertisement of the route to the
subsequent AS in the path. 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. It also describes how a BGPSEC-compliant BGP attribute, BGPsec_Path. It also describes how a BGPsec-compliant BGP
speaker (referred to hereafter as a BGPSEC speaker) can generate, speaker (referred to hereafter as a BGPsec speaker) can generate,
propagate, and validate BGP update messages containing this attribute propagate, and validate BGP update messages containing this attribute
to obtain the above assurances. to obtain the above assurances.
BGPSEC is intended to be used to supplement BGP Origin Validation BGPsec is intended to be used to supplement BGP Origin Validation
[19] and when used in conjunction with origin validation, it is [19] and when used in conjunction with origin validation, it is
possible to prevent a wide variety of route hijacking attacks against possible to prevent a wide variety of route hijacking attacks against
BGP. BGP.
BGPSEC relies on the Resource Public Key Infrastructure (RPKI) BGPsec relies on the Resource Public Key Infrastructure (RPKI)
certificates that attest to the allocation of AS number and IP certificates that attest to the allocation of AS number and IP
address resources. (For more information on the RPKI, see [7] and address resources. (For more information on the RPKI, see [7] and
the documents referenced therein.) Any BGPSEC speaker who wishes to the documents referenced therein.) Any BGPsec speaker who wishes to
send, to external (eBGP) peers, BGP update messages containing the send, to external (eBGP) peers, BGP update messages containing the
BGPSEC_Path needs to possess a private key associated with an RPKI BGPsec_Path needs to possess a private key associated with an RPKI
router certificate [10] that corresponds to the BGPSEC speaker's AS router certificate [10] that corresponds to the BGPsec speaker's AS
number. Note, however, that a BGPSEC speaker does not need such a number. Note, however, that a BGPsec speaker does not need such a
certificate in order to validate received update messages containing certificate in order to validate received update messages containing
the BGPSEC_Path attribute. the BGPsec_Path attribute.
2. BGPSEC Negotiation 2. BGPsec Negotiation
This document defines a new BGP capability [6] that allows a BGP This document defines a new BGP capability [6] that allows a BGP
speaker to advertise to a neighbor the ability to send or to receive speaker to advertise to a neighbor the ability to send or to receive
BGPSEC update messages (i.e., update messages containing the BGPsec update messages (i.e., update messages containing the
BGPSEC_Path attribute). BGPsec_Path attribute).
2.1. The BGPSEC Capability 2.1. The BGPsec Capability
This capability has capability code : TBD This capability has capability code : TBD
The capability length for this capability MUST be set to 3. 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.
BGPSEC Send Capability Value: BGPsec Send Capability Value:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---------------------------------------+ +---------------------------------------+
| Version | Dir | Reserved | | Version | Dir | Reserved |
+---------------------------------------+ +---------------------------------------+
| | | |
+------ AFI -----+ +------ AFI -----+
| | | |
+---------------------------------------+ +---------------------------------------+
The first four bits of the first octet indicate the version of BGPSEC The first four bits of the first octet indicate the version of BGPsec
for which the BGP speaker is advertising support. This document for which the BGP speaker is advertising support. This document
defines only BGPSEC version 0 (all four bits set to zero). Other defines only BGPsec version 0 (all four bits set to zero). Other
versions of BGPSEC may be defined in future documents. A BGPSEC versions of BGPsec may be defined in future documents. A BGPsec
speaker MAY advertise support for multiple versions of BGPSEC by speaker MAY advertise support for multiple versions of BGPsec by
including multiple versions of the BGPSEC capability in its BGP OPEN including multiple versions of the BGPsec capability in its BGP OPEN
message. message.
The fifth bit of the first octet is a direction bit which indicates The fifth bit of the first octet is a direction bit which indicates
whether the BGP speaker is advertising the capability to send BGPSEC whether the BGP speaker is advertising the capability to send BGPsec
update messages or receive BGPSEC update messages. The BGP speaker update messages or receive BGPsec update messages. The BGP speaker
sets this bit to 0 to indicate the capability to receive BGPSEC sets this bit to 0 to indicate the capability to receive BGPsec
update messages. The BGP speaker sets this bit to 1 to indicate the update messages. The BGP speaker sets this bit to 1 to indicate the
capability to send BGPSEC update messages. capability to send BGPsec update messages.
The remaining three bits of the first octet are reserved for future The remaining three bits of the first octet are reserved for future
use. These bits are set to zero by the sender of the capability and use. These bits are set to zero by the sender of the capability and
ignored by the receiver of the capability. 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 support for BGPsec. 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.
2.2. Negotiating BGPSEC Support 2.2. Negotiating BGPsec Support
In order to indicate that a BGP speaker is willing to send BGPSEC In order to indicate that a BGP speaker is willing to send BGPsec
update messages (for a particular address family), a BGP speaker update messages (for a particular address family), a BGP speaker
sends the BGPSEC Capability (see Section 2.1) with the Direction bit sends the BGPsec Capability (see Section 2.1) with the Direction bit
(the fifth bit of the first octet) set to 1. In order to indicate (the fifth bit of the first octet) set to 1. In order to indicate
that the speaker is willing to receive BGP update messages containing that the speaker is willing to receive BGP update messages containing
the BGPSEC_Path attribute (for a particular address family), a BGP the BGPsec_Path attribute (for a particular address family), a BGP
speaker sends the BGPSEC capability with the Direction bit set to 0. speaker sends the BGPsec capability with the Direction bit set to 0.
In order to advertise the capability to both send and receive BGPSEC In order to advertise the capability to both send and receive BGPsec
update messages, the BGP speaker sends two copies of the BGPSEC update messages, the BGP speaker sends two copies of the BGPsec
capability (one with the direction bit set to 0 and one with the capability (one with the direction bit set to 0 and one with the
direction bit set to 1). direction bit set to 1).
Similarly, if a BGP speaker wishes to use BGPSEC with two different Similarly, if a BGP speaker wishes to use BGPsec with two different
address families (i.e., IPv4 and IPv6) over the same BGP session, address families (i.e., IPv4 and IPv6) over the same BGP session,
then the speaker includes two instances of this capability (one for then the speaker includes two instances of this capability (one for
each address family) in the BGP OPEN message. A BGP speaker SHOULD each address family) in the BGP OPEN message. A BGP speaker SHOULD
NOT advertise the capability of BGPSEC support for a particular AFI NOT advertise the capability of BGPsec support for a particular AFI
unless it has also advertised the multiprotocol extension capability unless it has also advertised the multiprotocol extension capability
for the same AFI combination [3]. for the same AFI combination [3].
In a session where BGP session, a peer is permitted to send update In a session where BGP session, a peer is permitted to send update
messages containing the BGPSEC_Path attribute if, and only if: messages containing the BGPsec_Path attribute if, and only if:
o The given peer sent the BGPSEC capability for a particular version o The given peer sent the BGPsec capability for a particular version
of BGPSEC and a particular address family with the Direction bit of BGPsec and a particular address family with the Direction bit
set to 1; and set to 1; and
o The other peer sent the BGPSEC capability for the same version of o The other peer sent the BGPsec capability for the same version of
BGPSEC and the same address family with the Direction bit set to BGPsec and the same address family with the Direction bit set to
0. 0.
In such a session, we say that the use of (the particular version of) In such a session, we say that the use of (the particular version of)
BGPSEC has been negotiated (for a particular address family). BGP BGPsec has been negotiated (for a particular address family). BGP
update messages without the BGPSEC_Path attribute MAY be sent within update messages without the BGPsec_Path attribute MAY be sent within
a session regardless of whether or not the use of BGPSEC is a session regardless of whether or not the use of BGPsec is
successfully negotiated. However, if BGPSEC is not successfully successfully negotiated. However, if BGPsec is not successfully
negotiated, then BGP update messages containing the BGPSEC_Path negotiated, then BGP update messages containing the BGPsec_Path
attribute MUST NOT be sent. attribute MUST NOT be sent.
This document defines the behavior of implementations in the case This document defines the behavior of implementations in the case
where BGPSEC version zero is the only version that has been where BGPsec version zero is the only version that has been
successfully negotiated. Any future document which specifies successfully negotiated. Any future document which specifies
additional versions of BGPSEC will need to specify behavior in the additional versions of BGPsec will need to specify behavior in the
case that support for multiple versions is negotiated. case that support for multiple versions is negotiated.
BGPSEC cannot provide meaningful security guarantees without support BGPsec cannot provide meaningful security guarantees without support
for four-byte AS numbers. Therefore, any BGP speaker that announces for four-byte AS numbers. Therefore, any BGP speaker that announces
the BGPSEC capability, MUST also announce the capability for four- the BGPsec capability, MUST also announce the capability for four-
byte AS support [4]. If a BGP speaker sends the BGPSEC capability but byte AS support [4]. If a BGP speaker sends the BGPsec capability but
not the four-byte AS support capability then BGPSEC has not been not the four-byte AS support capability then BGPsec has not been
successfully negotiated, and update messages containing the successfully negotiated, and update messages containing the
BGPSEC_Path attribute MUST NOT be sent within such a session. 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].
3. The BGPSEC_Path Attribute 3. The BGPsec_Path Attribute
The BGPSEC_Path attribute is a new optional non-transitive BGP path The BGPsec_Path attribute is a new optional non-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 attribute carries the secured information regarding The BGPsec_Path attribute carries the secured information regarding
the path of ASes through which an update message passes. This the path of ASes through which an update message passes. This
includes the digital signatures used to protect the path information. includes the digital signatures used to protect the path information.
We refer to those update messages that contain the BGPSEC_Path We refer to those update messages that contain the BGPsec_Path
attribute as "BGPSEC Update messages". The BGPSEC_Path attribute attribute as "BGPsec Update messages". The BGPsec_Path attribute
replaces the AS_PATH attribute in a BGPSEC update message. That is, replaces the AS_PATH attribute in a BGPsec update message. That is,
update messages that contain the BGPSEC_Path attribute MUST NOT update messages that contain the BGPsec_Path attribute MUST NOT
contain the AS_PATH attribute, and vice versa. contain the AS_PATH attribute, and vice versa.
The BGPSEC_Path attribute is made up of several parts. The following The BGPsec_Path attribute is made up of several parts. The following
high-level diagram provides an overview of the structure of the high-level diagram provides an overview of the structure of the
BGPSEC_Path attribute: BGPsec_Path attribute:
High-Level Diagram of the BGPSEC_Path Attribute High-Level Diagram of the BGPsec_Path Attribute
+---------------------------------------------------------+ +---------------------------------------------------------+
| +-----------------+ | | +-----------------+ |
| | Secure Path | | | | Secure Path | |
| +-----------------+ | | +-----------------+ |
| | AS X | | | | AS X | |
| | pCount X | | | | pCount X | |
| | Flags X | | | | Flags X | |
| | AS Y | | | | AS Y | |
| | pCount Y | | | | pCount Y | |
| | Flags Y | | | | Flags Y | |
skipping to change at page 6, line 50 skipping to change at page 6, line 50
| | Alg Suite 1 | | Alg Suite 2 | | | | Alg Suite 1 | | Alg Suite 2 | |
| | SKI X1 | | SKI X1 | | | | SKI X1 | | SKI X1 | |
| | Signature X1 | | Signature X1 | | | | Signature X1 | | Signature X1 | |
| | SKI Y1 | | SKI Y1 | | | | SKI Y1 | | SKI Y1 | |
| | Signature Y1 | | Signature Y1 | | | | Signature Y1 | | Signature Y1 | |
| | ... | | .... | | | | ... | | .... | |
| +-----------------+ +-----------------+ | | +-----------------+ +-----------------+ |
| | | |
+---------------------------------------------------------+ +---------------------------------------------------------+
The following is the specification of the format for the BGPSEC_Path The following is the specification of the format for the BGPsec_Path
attribute. attribute.
BGPSEC_Path Attribute BGPsec_Path Attribute
+-------------------------------------------------------+ +-------------------------------------------------------+
| Secure_Path (variable) | | Secure_Path (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 is message. This is logically equivalent to the information that is
contained in a non-BGPSEC AS_PATH attribute. A BGPSEC update message contained in a non-BGPsec AS_PATH attribute. The information in
containing the BGPSEC_Path attribute MUST NOT contain the AS_PATH Secure_Path is used by BGPsec speakers in the same way that
attribute. The Secure_Path is used by BGPSEC speakers in the same information from the AS_PATH is used by non-BGPsec speakers. The
way that information from the AS_PATH is used by non-BGPSEC speakers. format of the Secure_Path is described below in Section 3.1.
The format of the Secure_Path is described below in Section 3.1.
The BGPSEC_Path attribute will contain one or two Signature_Blocks, The BGPsec_Path attribute will contain one or two Signature_Blocks,
each of which corresponds to a different algorithm suite. Each of each of which corresponds to a different algorithm suite. Each of
the Signature_Blocks will contain a signature segment for one AS the Signature_Blocks will contain a signature segment for each AS
number (i.e, secure path segment) in the Secure_Path. In the most number (i.e., Secure_Path segment) in the Secure_Path. In the most
common case, the BGPSEC_Path attribute will contain only a single common case, the BGPsec_Path attribute will contain only a single
Signature_Block. However, in order to enable a transition from an Signature_Block. However, in order to enable a transition from an
old algorithm suite to a new algorithm suite (without a flag day), 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 3.2. 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 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 entire The Secure_Path Length contains the length (in octets) of the entire
skipping to change at page 8, line 22 skipping to change at page 8, line 21
+----------------------------+ +----------------------------+
| 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 attribute. (See Section 4 for Secure_Path segment to the BGPsec_Path attribute. (See 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 prepending enables a BGPsec speaker to mimic the semantics of prepending
multiple copies of their AS to the AS_PATH without requiring the multiple copies of their AS to the AS_PATH without requiring the
speaker to generate multiple signatures. (The pCount field is also speaker to generate multiple signatures. The pCount field is also
useful in managing AS Number migrations, see [18] for details.) useful in managing route servers (see Section 4.2) and AS Number
migrations, see [18] for details.
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
[5]. (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 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 AS 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 MUST be set to zero by the The remaining seven bits of the Flags MUST be set to zero by the
sender, and ignored by the receiver. Note, however, that the sender, and ignored by the receiver. Note, however, that the
signature is computed over all eight bits of the flags field. signature is computed over all eight bits of the flags field.
3.2. 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 attribute. BGPsec_Path attribute.
Signature_Block Signature_Block
+---------------------------------------------+ +---------------------------------------------+
| Signature_Block Length (2 octets) | | Signature_Block Length (2 octets) |
+---------------------------------------------+ +---------------------------------------------+
| Algorithm Suite Identifier (1 octet) | | 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 The Signature_Block Length is the total number of octets in the
Signature_Block (including the two octets used to express this length Signature_Block (including the two octets used to express this length
field). 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 specified in the BGPSEC algorithm identifiers for use in BGPsec is specified in the BGPsec
algorithms document [11]. algorithms document [11].
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 BGPSEC_Path Secure_Path Segment in the Secure_Path portion of the BGPsec_Path
Attribute. (That is, one Signature Segment for each distinct AS on Attribute. (That is, one Signature Segment 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 router certificate [10] 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 attribute (see Sections 4 and 5 for details on the BGPsec_Path attribute (see Sections 4 and 5 for details on
signature generation and validation, 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 attribute. The generate an update message containing the BGPsec_Path attribute. The
first case is that in which the BGPSEC speaker originates a new route first case is that in which the BGPsec speaker originates a new route
advertisement (Section 4.1). That is, the BGPSEC speaker is advertisement (Section 4.1). That is, the BGPsec speaker is
constructing an update message in which the only AS to appear in the constructing an update message in which the only AS to appear in the
BGPSEC_Path is the speaker's own AS. The second case is that in BGPsec_Path is the speaker's own AS. The second case is that in
which the BGPSEC speaker receives a route advertisement from a peer which the BGPsec speaker receives a route advertisement from a peer
and then decides to propagate the route advertisement to an external and then decides to propagate the route advertisement to an external
(eBGP) peer (Section 4.2). That is, the BGPSEC speaker has received (eBGP) peer (Section 4.2). That is, the BGPsec speaker has received
a BGPSEC update message and is constructing a new update message for a BGPsec update message and is constructing a new update message for
the same NLRI in which the BGPSEC_Path attribute will contain AS the same NLRI in which the BGPsec_Path attribute will contain AS
number(s) other than the speaker's own AS. number(s) other than the speaker's own AS.
The remaining case is where the BGPSEC speaker sends the update The remaining case is where the BGPsec speaker sends the update
message to an internal (iBGP) peer. When originating a new route message to an internal (iBGP) peer. When originating a new route
advertisement and sending it to an internal peer, the BGPSEC speaker advertisement and sending it to an internal peer, the BGPsec speaker
creates a new BGPSEC_Path attribute with zero Secure_Path segments omits the BGPsec_Path attribute. When propagating a received route
and zero Signature Segments. When propagating a received route advertisement to an internal peer, the BGPsec speaker populates the
advertisement to an internal peer, the BGPSEC speaker populates the BGPsec_Path attribute by copying the BGPsec_Path attribute from the
BGPSEC_Path attribute by copying the BGPSEC_Path attribute from the received update message. That is, the BGPsec_Path attribute is
received update message. That is, the BGPSEC_Path attribute is copied verbatim. Note that in the case that a BGPsec speaker chooses
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
to forward to an iBGP peer a BGPSEC update message that has not been successfully validated (see Section 5), the BGPsec_Path attribute
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.
In order to create or add a new signature to a BGPSEC update message In order to create or add a new signature to a BGPsec update message
with a given algorithm suite, the BGPSEC speaker must possess a with a given algorithm suite, the BGPsec speaker must possess a
private key suitable for generating signatures for this algorithm private key suitable for generating signatures for this algorithm
suite. Additionally, this private key must correspond to the public suite. Additionally, this private key must correspond to the public
key in a valid Resource PKI end-entity certificate whose AS number key in a valid Resource PKI end-entity certificate whose AS number
resource extension includes the BGPSEC speaker's AS number [10]. Note resource extension includes the BGPsec speaker's AS number [10]. Note
also that new signatures are only added to a BGPSEC update message also that new signatures are only added to a BGPsec update message
when a BGPSEC speaker is generating an update message to send to an when a BGPsec speaker is generating an update message to send to an
external peer (i.e., when the AS number of the peer is not equal to external peer (i.e., when the AS number of the peer is not equal to
the BGPSEC speaker's own AS number). Therefore, a BGPSEC speaker who the BGPsec speaker's own AS number). Therefore, a BGPsec speaker who
only sends BGPSEC update messages to peers within its own AS, it does only sends BGPsec update messages to peers within 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 Section 4.3 contains special processing instructions for members of
an autonomous system confederation [5]. A BGPsec speaker that is not
a member of such a confederation MUST set the Flags field of the
Secure_Path Segment to zero in all BGPsec update messages it sends.
Section 4.4 contains instructions for reconstructing the AS_Path
attribute in cases where a BGPsec speaker receives an update message
with a BGPsec_Path attribute and wishes to propagate the update
message to a peer who does not support BGPsec.
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 attribute as follows. the BGPsec speaker creates a new BGPsec_Path attribute as 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 an 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 router the AS number resource extension field of the Resource PKI router
certificate(s) [10] that will be used to verify the digital certificate(s) [10] that will be used to verify the digital
signature(s) constructed by this BGPSEC speaker. signature(s) constructed by this BGPsec speaker.
The BGPSEC_Path attribute and the AS_Path attribute are mutually The BGPsec_Path attribute and the AS_Path attribute are mutually
exclusive. That is, any update message containing the BGPSEC_Path exclusive. That is, any update message containing the BGPsec_Path
attribute MUST NOT contain the AS_Path attribute. The information attribute MUST NOT contain the AS_Path attribute. The information
that would be contained in the AS_Path attribute is instead conveyed that would be contained in the AS_Path attribute is instead conveyed
in the Secure_Path portion of the BGPSEC_Path attribute. in the Secure_Path portion of the BGPsec_Path attribute.
The Resource PKI enables the legitimate holder of IP address The Resource PKI enables the legitimate holder of IP address
prefix(es) to issue a signed object, called a Route Origination prefix(es) to issue a signed object, called a Route Origination
Authorization (ROA), that authorizes a given AS to originate routes Authorization (ROA), that authorizes a given AS to originate routes
to a given set of prefixes (see [8]). It is expected that most to a given set of prefixes (see [8]). It is expected that most
relying parties will utilize BGPSEC in tandem with origin validation relying parties will utilize BGPsec in tandem with origin validation
(see [19] and [20]). Therefore, it is RECOMMENDED that a BGPSEC (see [19] and [20]). Therefore, it is RECOMMENDED that a BGPsec
speaker only originate a BGPSEC update advertising a route for a speaker only originate a BGPsec update advertising a route for a
given prefix if there exists a valid ROA authorizing the BGPSEC given prefix if there exists a valid ROA authorizing the BGPsec
speaker's AS to originate routes to this prefix. speaker's AS to originate routes to this prefix.
The pCount field of the Secure_Path Segment is typically set to the The pCount field of the Secure_Path Segment is typically set to the
value 1. However, a BGPSEC speaker may set the pCount field to a value 1. However, a BGPsec speaker may set the pCount field to a
value greater than 1. Setting the pCount field to a value greater value greater than 1. Setting the pCount field to a value greater
than one has the same semantics as repeating an AS number multiple than one has the same semantics as repeating an AS number multiple
times in the AS_PATH of a non-BGPSEC update message (e.g., for times in the AS_PATH of a non-BGPsec update message (e.g., for
traffic engineering purposes). Setting the pCount field to a value traffic engineering purposes). Setting the pCount field to a value
greater than one permits this repetition without requiring a separate greater than one permits this repetition without requiring a separate
digital signature for each repetition. digital signature for each repetition.
If the BGPSEC speaker is not a member of an autonomous system Typically, a BGPsec speaker will use only a single algorithm suite,
confederation [5], then the Flags field of the Secure_Path Segment and thus create only a single Signature_Block in the BGPsec_Path
MUST be set to zero. (Members of a confederation should follow the
special processing instructions for confederation members in Section
4.4.)
Typically, a BGPSEC speaker will use only a single algorithm suite,
and thus create only a single Signature_Block in the BGPSEC_Path
attribute. However, to ensure backwards compatibility during a attribute. However, to ensure backwards compatibility during a
period of transition from a 'current' algorithm suite to a 'new' period of transition from a 'current' algorithm suite to a 'new'
algorithm suite, it will be necessary to originate update messages algorithm suite, it will be necessary to originate update messages
that contain a Signature_Block for both the 'current' and the 'new' that contain a Signature_Block for both the '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 router certificate corresponding to the BGPSEC speaker[10]. the RPKI router certificate corresponding to the BGPsec speaker[10].
This 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 attribute to the RPKI router corresponding to the and BGPsec_Path attribute to the RPKI router certificate
BGPSEC speaker. The digital signature is computed as follows: corresponding to the BGPsec speaker. The digital 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 (Origin AS, pCount, and Flags), Algorithm Number, the Secure_Path (Origin AS, pCount, and Flags), Algorithm
Suite Identifier, and NLRI. The Target AS Number is the AS to Suite Identifier, and NLRI. The Target AS Number is the AS to
whom the BGPSEC speaker intends to send the update message. (Note whom the BGPsec speaker intends to send the update message. (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 update is in the OPEN message of the BGP session within which the update is
sent.) 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
skipping to change at page 13, line 34 skipping to change at page 13, line 34
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 attribute (with one or more signatures) from an (internal BGPsec_Path attribute (with one or more signatures) from an (internal
or external) peer, it may choose to propagate the route advertisement or external) peer, it may choose to propagate the route advertisement
by sending to its (internal or external) peers by creating a new by sending to its (internal or external) peers by creating a new
BGPSEC advertisement for the same prefix. BGPsec advertisement for the same prefix.
If a BGPSEC router has received only a non-BGPSEC update message If a BGPsec router has received only a non-BGPsec update message
(without the BGPSEC_Path attribute), containing the AS_Path (without the BGPsec_Path attribute), containing the AS_Path
attribute, from a peer for a given prefix then it MUST NOT attach a attribute, from a peer for a given prefix then it MUST NOT attach a
BGPSEC_Path attribute when it propagates the update message. (Note BGPsec_Path attribute when it propagates the update message. (Note
that a BGPSEC router may also receive a non-BGPSEC update message that a BGPsec router may also receive a non-BGPsec update message
from an internal peer without the AS_Path attribute, i.e., with just from an internal peer without the AS_Path attribute, i.e., with just
the NLRI in it. In that case, the prefix is originating from that AS the NLRI in it. In that case, the prefix is originating from that AS
and hence the BGPSEC speaker SHOULD sign and forward the update to and hence the BGPsec speaker SHOULD sign and forward the update to
its external peers, as specified in Section 4.1.) its external peers, as specified in Section 4.1.)
Conversely, if a BGPSEC router has received a BGPSEC update message Conversely, if a BGPsec router has received a BGPsec update message
(with the BGPSEC_Path attribute) from a peer for a given prefix and (with the BGPsec_Path attribute) from a peer for a given prefix and
it chooses to propagate that peer's route for the prefix, then it it chooses to propagate that peer's route for the prefix, then it
SHOULD propagate the route as a BGPSEC update message containing the SHOULD propagate the route as a BGPsec update message containing the
BGPSEC_Path attribute. BGPsec_Path 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 attribute) has significant advertisement without the BGPsec_Path attribute) has significant
security ramifications. (See Section 7 for discussion of the security ramifications. (See Section 7 for discussion of the
security ramifications of removing BGPSEC signatures.) Therefore, security ramifications of removing BGPsec signatures.) Therefore,
when a route advertisement is received via a BGPSEC update message, when a route advertisement is received via a BGPsec update message,
propagating the route advertisement without the BGPSEC_Path attribute propagating the route advertisement without the BGPsec_Path attribute
is NOT RECOMMENDED, unless the message is sent to a peer that did not is NOT RECOMMENDED, unless the message is sent to a peer that did not
advertise the capability to receive BGPSEC update messages (see advertise the capability to receive BGPsec update messages (see
Section 4.4). Section 4.4).
Furthermore, note that when a BGPSEC speaker propagates a route Furthermore, note that when a BGPsec speaker propagates a route
advertisement with the BGPSEC_Path attribute it is not attesting to advertisement with the BGPsec_Path attribute it is not attesting to
the validation state of the update message it received. (See Section the validation state of the update message it received. (See Section
7 for more discussion of the security semantics of BGPSEC 7 for more discussion of the security semantics of BGPsec
signatures.) 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 attribute. In such a case, the BGPSEC include the BGPsec_Path attribute. In such a case, the BGPsec
speaker must remove any existing BGPSEC_Path in the received speaker must remove any existing BGPsec_Path in the received
advertisement(s) for this prefix and produce a traditional (non- advertisement(s) for this prefix and produce a traditional (non-
BGPSEC) update message. It should be noted that BCP 172 [13] BGPsec) update message. It should be noted that BCP 172 [13]
recommends against the use of AS_SET and AS_CONFED_SET in the AS_PATH recommends against the use of AS_SET and AS_CONFED_SET in the AS_PATH
of BGP updates. of BGP updates.
To generate the BGPSEC_Path attribute on the outgoing update message, To generate the BGPsec_Path attribute on the outgoing update message,
the BGPSEC speaker first prepends a new Secure_Path Segment (places the BGPsec speaker first prepends a new Secure_Path Segment (places
in first position) to the Secure_Path. The AS number in this in first position) to the Secure_Path. The AS number 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 router certificate(s) resource extension field of the Resource PKI router certificate(s)
that will be used to verify the digital signature(s) constructed by that will be used to verify the digital signature(s) constructed by
this BGPSEC speaker[10]. 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.) discussion of setting pCount to a value greater than 1.)
A route server that participates in the BGP control path, but does A route 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 not act as a transit AS in the data plane, may choose to set pCount
to 0. This option enables the route server to participate in BGPSEC to 0. This option enables the route server to participate in BGPsec
and obtain the associated security guarantees without increasing the and obtain the associated security guarantees without increasing the
effective length of the AS path. (Note that BGPSEC speakers compute effective 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 attribute, see Section 5.) However, when a route the BGPsec_Path attribute, see Section 5.) However, when a route
server sets the pCount value to 0, it still inserts its AS number server sets the pCount value to 0, it still inserts its AS number
into the Secure_Path segment, as this information is needed to into the Secure_Path segment, as this information is needed to
validate the signature added by the route server. (See [18] for a validate the signature added by the route server. (See [18] for a
discussion of setting pCount to 0 to facilitate AS Number Migration.) discussion of setting pCount to 0 to facilitate AS Number Migration.)
BGPSEC speakers SHOULD drop incoming update messages with pCount set BGPsec speakers SHOULD drop incoming update messages with pCount set
to zero in cases where the BGPSEC speaker does not expect its peer to to zero in cases where the BGPsec speaker does not expect its peer to
set pCount to zero. (That is, pCount is only to be set to zero in set pCount to zero. (That is, pCount is only to be set to zero in
cases such as route servers or AS Number Migration where the BGPSEC cases such as route servers or AS Number Migration where the BGPsec
speaker's peer expects pCount to be set to zero.) speaker's peer expects pCount to be set to zero.)
If the BGPSEC speaker is not a member of an autonomous system If the received BGPsec update message contains two Signature_ Blocks
confederation [5], then the Confed_Segment bit of the Flags field of and the BGPsec speaker supports both of the corresponding algorithms
the Secure_Path Segment MUST be set to zero. (Members of a suites, then the new update message generated by the BGPsec speaker
confederation should follow the special processing instructions for SHOULD include both of the Signature_Blocks. If the received BGPsec
confederation members in Section 4.3.) update message contains two Signature_Blocks and the BGPsec speaker
If the received BGPSEC update message contains two Signature_ Blocks
and the BGPSEC speaker supports both of the corresponding algorithms
suites, then the new update message generated by the BGPSEC speaker
SHOULD include both of the Signature_Blocks. If the received BGPSEC
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 BGPSEC_Path MUST NOT propagate the route advertisement with the BGPsec_Path
attribute. (That is, if it chooses to propagate this route attribute. (That is, if it chooses to propagate this route
advertisement at all, it must do so as an unsigned BGP update advertisement at all, it must do so as an unsigned BGP update
message). message).
Note that in the case where the BGPSEC_Path has two Signature_Blocks Note that in the case where the BGPsec_Path has two Signature_Blocks
(corresponding to different algorithm suites), the validation (corresponding to different algorithm suites), 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
'Valid' 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 'Valid'. This means corresponding Signature_Block) that is deemed 'Valid'. This means
that a 'Valid' BGPSEC update message may contain a Signature_Block that a 'Valid' BGPsec update message may contain a Signature_Block
which is not deemed 'Valid' (e.g., contains signatures that the which is not deemed 'Valid' (e.g., contains signatures that the
BGPSEC does not successfully verify). Nonetheless, such BGPsec does not successfully verify). Nonetheless, such
Signature_Blocks MUST NOT be removed. (See Section 7 for a Signature_Blocks MUST NOT be removed. (See Section 7 for a
discussion of the security 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 adds a new Signature BGPsec speaker does support, the BGPsec speaker adds a new Signature
Segment to the Signature_Block. This Signature Segment is prepended Segment to the Signature_Block. This Signature Segment is prepended
to the list of Signature Segments (placed in the first position) so to the list of Signature Segments (placed in the first position) so
that the list of Signature Segments appear in the same order as the that the list of Signature Segments appear in the same order as the
corresponding Secure_Path segments. The BGPSEC speaker populates the corresponding Secure_Path segments. The BGPsec speaker populates the
fields of this new signature segment as follows. 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 router corresponding to the BGPSEC speaker [10]. 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 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 attribute to the RPKI router that binds the NLRI and BGPsec_Path attribute to the RPKI router
certificate corresponding to 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.
Sequence of Octets to be Signed Sequence of Octets to be Signed
+--------------------------------------+ +--------------------------------------+
| Target AS Number (4 octets) | | Target AS Number (4 octets) |
+--------------------------------------+ +--------------------------------------+
| Signer's AS Number (4 octets) | ---\ | Signer's AS Number (4 octets) | ---\
+--------------------------------------+ \ +--------------------------------------+ \
| pCount (1 octet) | > Secure_Path | pCount (1 octet) | > Secure_Path
+--------- ----------------------------+ / +--------- ----------------------------+ /
skipping to change at page 17, line 8 skipping to change at page 17, line 8
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 [5] 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
generates the Secure_Path Segment sets the Confed_Segment flag to generates the Secure_Path Segment sets the Confed_Segment flag to
one. This means that in a BGPSEC update message, an AS number one. This means that in a BGPsec update message, an AS number
appears in a Secure_Path Segment with the Confed_Segment flag set appears in a Secure_Path Segment with the Confed_Segment flag set
whenever, in a non-BGPSEC update message, the AS number would appear whenever, in a non-BGPsec update message, the AS number would appear
in a segment of type AS_CONFED_SEQUENCE in a non-BGPSEC update in a segment of type AS_CONFED_SEQUENCE in a non-BGPsec update
message. message.
Within a confederation, the verification of BGPSEC signatures added Within a confederation, the verification of BGPsec signatures added
by other members of the confederation is optional. If a by other members of the confederation is optional. If a
confederation chooses not to have its members verify signatures added confederation chooses not to have its members verify signatures added
by other confederation members, then when sending a BGPSEC update by other confederation members, then when sending a BGPsec update
message to a peer that is a member of the same confederation, the message to a peer that is a member of the same confederation, the
confederation members MAY set the Signature field within the confederation members MAY set the Signature field within the
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 needs to remove all of the Secure_Path Segments confederation, it needs to remove all of the Secure_Path Segments
added 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 most recently added Secure_Path segments, o First, starting with the most recently added Secure_Path segment,
remove all of the consecutive Secure_Path segments that have the remove all of the consecutive Secure_Path segments that 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 need to make the following adjustment to the algorithm members need to make the following adjustment to the algorithm
presented in Section 5.2. When a confederation member processes presented in Section 5.2. When a confederation member processes
(validates) a Signature Segment and its corresponding Secure_Path (validates) a Signature Segment and its corresponding Secure_Path
Segment, the confederation member must note that for a signature Segment, the confederation member must note the following. For a
produced by a BGPSEC speaker outside of a confederation, the Target signature produced by a peer BGPsec speaker outside of a
AS will always be the AS Confederation Identifier (the public AS confederation, the Target AS will always be the AS Confederation
number of the confederation) as opposed to the Member-AS Number. Identifier (the public AS 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 zero.) 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, the confederation member, during processing algorithm in Section 5.2, the confederation member, during processing
of a Signature_Segment, first checks whether the Confed_Sequence flag of a Signature_Segment, first checks whether the Confed_Sequence flag
in the corresponding Secure_Path segment is set to one. If the in 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
Signature_Segment (and checks its corresponding Secure_Path segment). Signature_Segment (and checks its corresponding Secure_Path segment).
Note that as specified in Section 5.2, it is an error when a BGPSEC Note that as specified in Section 5.2, it is an error when a BGPsec
speaker receives from a peer, who is not in the same AS speaker receives from a peer, who is not in the same AS
confederation, a BGPSEC update containing a Confed_Sequence flag set confederation, a BGPsec update containing a Confed_Sequence flag set
to one. (As discussed in Section 5.2, any error in the BGPSEC_Path to one. (As discussed in Section 5.2, any error in the BGPsec_Path
attribute MUST be handled using the "treat-as-withdraw", approach as attribute MUST be handled using the "treat-as-withdraw", approach as
defined in RFC WXYZ [12].) defined in RFC WXYZ [12].)
4.4. Reconstructing the AS_PATH Attribute 4.4. Reconstructing the AS_PATH Attribute
BGPSEC update messages do not contain the AS_PATH attribute. However, BGPsec update messages do not contain the AS_PATH attribute. However,
the AS_PATH attribute can be reconstructed from the BGPSEC_Path the AS_PATH attribute can be reconstructed from the BGPsec_Path
attribute. This is necessary in the case where a route advertisement attribute. This is necessary in the case where a route advertisement
is received via a BGPSEC update message and then propagated to a peer is received via a BGPsec update message and then propagated to a peer
via a non-BGPSEC update message (e.g., because the latter peer does via a non-BGPsec update message (e.g., because the latter peer does
not support BGPSEC). Note that there may be additional cases where an not support BGPsec). Note that there may be additional cases where an
implementation finds it useful to perform this reconstruction. implementation finds it useful to perform this reconstruction.
The AS_PATH attribute can be constructed from the BGPSEC_Path The AS_PATH attribute can be constructed from the BGPsec_Path
attribute as follows. Starting with an empty AS_PATH attribute, attribute as follows. Starting with an empty AS_PATH attribute,
process the Secure_Path segments in order from least-recently added process the Secure_Path segments in order from least-recently added
(corresponding to the origin) to most-recently added. For each (corresponding to the origin) to most-recently 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
skipping to change at page 20, line 29 skipping to change at page 20, line 29
* 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 path information contained in the BGPSEC_Path authenticity of the path information contained in the BGPsec_Path
attribute. Section 5.1 provides an overview of BGPSEC validation and attribute. Typically, a BGPsec speaker will also wish to perform
Section 5.2 provides a specific algorithm for performing such origin validation (see [19] and [20]) on an incoming BGPsec update
validation. (Note that an implementation need not follow the message, but such validation is independent of the validation
specific algorithm in Section 5.2 as long as the input/output described in this section.
behavior of the validation is identical to that of the algorithm in
Section 5.2.) During exceptional conditions (e.g., the BGPSEC
speaker receives an incredibly large number of update messages at
once) a BGPSEC speaker MAY temporarily defer validation of incoming
BGPSEC update messages. The treatment of such BGPSEC update
messages, whose validation has been deferred, is a matter of local
policy.
The validity of BGPSEC update messages is a function of the current Section 5.1 provides an overview of BGPsec validation and Section 5.2
RPKI state. When a BGPSEC speaker learns that RPKI state has changed provides a specific algorithm for performing such validation. (Note
that an implementation need not follow the specific algorithm in
Section 5.2 as long as the input/output behavior of the validation is
identical to that of the algorithm in Section 5.2.) During
exceptional conditions (e.g., the BGPsec speaker receives an
incredibly large number of update messages at once) a BGPsec speaker
MAY temporarily defer validation of incoming BGPsec update messages.
The treatment of such BGPsec update messages, whose validation has
been deferred, is a matter of local policy.
The validity of BGPsec update messages is a function of the current
RPKI state. When a BGPsec speaker learns that RPKI state has changed
(e.g., from an RPKI validating cache via the RTR protocol), the (e.g., from an RPKI validating cache via the RTR protocol), the
BGPSEC speaker MUST re-run validation on all affected update messages BGPsec speaker MUST re-run validation on all affected update messages
stored in its ADJ-RIB-IN. That is, when a given RPKI certificate stored in its ADJ-RIB-IN. That is, when a given RPKI certificate
ceases to be valid (e.g., it expires or is revoked), all update ceases to be valid (e.g., it expires or is revoked), all update
messages containing a signature whose SKI matches the SKI in the messages containing a signature whose SKI matches the SKI in the
given certificate must be re-assessed to determine if they are still given certificate must be re-assessed to determine if they are still
valid. If this reassessment determines that the validity state of an valid. If this reassessment determines that the validity state of an
update has changed then, depending on local policy, it may be update has changed then, depending on local policy, it may be
necessary to re-run best path selection. 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 attribute in all cases where it would otherwise use the BGPsec_Path attribute in all cases where it would otherwise use
the AS path information in the AS_PATH attribute. The only exception the AS path information in the AS_PATH attribute. The only exception
to this rule is when AS path information must be updated in order to to this rule is when AS path information must be updated in order to
propagate a route to a peer (in which case the BGPSEC speaker follows propagate a route to a peer (in which case the BGPsec speaker follows
the instructions in Section 4). Section 4.4 provides an algorithm the instructions in Section 4). Section 4.4 provides an algorithm
for constructing an AS_PATH attribute from a BGPSEC_Path attribute. for constructing an AS_PATH attribute from a BGPsec_Path attribute.
Whenever the use of AS path information is called for (e.g., loop Whenever the use of AS path information is called for (e.g., loop
detection, or use of AS path length in best path selection) the detection, or use of AS path length in best path selection) the
externally visible behavior of the implementation shall be the same externally visible behavior of the implementation shall be the same
as if the implementation had run the algorithm in Section 4.4 and as if the implementation had run the algorithm in Section 4.4 and
used the resulting AS_PATH attribute as it would for a non-BGPSEC used the resulting AS_PATH attribute as it would for a non-BGPsec
update message. update message.
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 attribute). That is, if the Signature fields (within the BGPsec_Path attribute). That is, if
all the fields in the second update are identical to the fields in all the fields in the second update are identical to the fields in
the first update message, except for the Signature fields, then the the first update message, except for the Signature fields, then the
second update message should be treated as a duplicate of the first second update message should be treated as a duplicate of the first
update message. Note that if other fields (e.g., the Subject Key update message. Note that if other fields (e.g., the Subject Key
Identifier field) within a Signature segment differ between two Identifier field) within a Signature segment differ 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 BGPSEC_Path particular, to validate update messages containing the BGPsec_Path
attribute, it is necessary that the recipient have access to the attribute, it is necessary that the recipient have access to the
following data obtained from valid RPKI certificates and ROAs: following data obtained from valid RPKI certificates and ROAs:
o For each valid RPKI router certificate, the AS Number, Public Key o For each valid RPKI router certificate, the AS Number, Public Key
and Subject Key Identifier are required, and Subject Key Identifier 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. (For example, validation on behalf of (some set of) BGPsec speakers. (For example,
the trusted cache could deliver the necessary validity information to the trusted cache could deliver the necessary validity information to
the BGPSEC speaker using the router key PDU [16] for the RTR protocol the BGPsec speaker using the router key PDU [16] for the RTR protocol
[15].) [15].)
To validate a BGPSEC update message containing the BGPSEC_Path To validate a BGPsec update message containing the BGPsec_Path
attribute, the recipient performs the validation steps specified in attribute, the recipient performs the validation steps specified in
Section 5.2. The validation procedure results in one of two states: Section 5.2. The validation procedure results in one of two states:
'Valid' and 'Not Valid'. '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 is handled using local policy mechanisms. matter of local policy, and is handled using local policy mechanisms.
It is expected that BGP peers will generally prefer routes received It is expected that BGP peers will generally prefer routes received
via 'Valid' BGPSEC update messages over both routes received via 'Not via 'Valid' BGPsec update messages over both routes received via 'Not
Valid' BGPSEC update messages and routes received via update messages Valid' BGPsec update messages and routes received via update messages
that do not contain the BGPSEC_Path attribute. However, BGPSEC that do not contain the BGPsec_Path attribute. However, BGPsec
specifies no changes to the BGP decision process. (See [17] for specifies no changes to the BGP decision process. (See [17] for
related operational considerations.) related operational considerations.)
BGPSEC validation needs only be performed at the eBGP edge. The BGPsec validation needs only be performed at the 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 via some iBGP from an ingress edge router to an egress edge router via some
mechanism, according to local policy within an AS. As discussed in mechanism, according to local policy within an AS. As discussed in
Section 4, when a BGPSEC speaker chooses to forward a (syntactically Section 4, when a BGPsec speaker chooses to forward a (syntactically
correct) BGPSEC update message, it SHOULD be forwarded with its correct) BGPsec update message, it SHOULD be forwarded with its
BGPSEC_Path attribute intact (regardless of the validation state of BGPsec_Path attribute intact (regardless of the validation state of
the update message). Based entirely on local policy, an egress the update message). Based entirely on local policy, an egress
router receiving a BGPSEC update message from within its own AS MAY router receiving a BGPsec update message from within its own AS MAY
choose to perform its own validation. choose to 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 validation algorithm that is functionally equivalent to the
externally visible 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 attribute is 1. Check to ensure that the entire BGPsec_Path attribute 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 attribute. (Note that the entirety of each BGPsec_Path attribute. (Note that the entirety of each
Signature_Block must be checked to ensure that it is well formed, Signature_Block must be checked to ensure that it is well formed,
even though the validation process may terminate before all even though the validation process may terminate before all
signatures are cryptographically verified.) signatures are cryptographically verified.)
3. Check that the update message does not contain an AS_PATH 3. Check that the update message does not contain 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 any of these checks fail, it is an error in the BGPSEC_Path If any of these checks fail, it is an error in the BGPsec_Path
attribute. Any of these errors in the BGPSEC_Path attribute are attribute. Any of these errors in the BGPsec_Path attribute are
handled as per RFC WXYZ [12]. BGPSEC speakers MUST handle these handled as per RFC WXYZ [12]. BGPsec speakers MUST handle these
errors using the "treat-as-withdraw" approach as defined in RFC WXYZ errors using the "treat-as-withdraw" approach as defined in RFC WXYZ
[12]. [12].
Next, the BGPSEC speaker examines the Signature_Blocks in the Next, the BGPsec speaker examines the Signature_Blocks in the
BGPSEC_Path attribute. A Signature_Block corresponding to an BGPsec_Path attribute. A Signature_Block corresponding to 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 is no Signature_Block considered in validation. If there is no 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 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 attribute. The following steps make use of within the BGPsec_Path attribute. The following steps 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 router 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
skipping to change at page 25, line 20 skipping to change at page 25, line 20
| AS Number (4 octets) | ---\ | AS Number (4 octets) | ---\
+-------------------------------------------+ \ +-------------------------------------------+ \
| pCount (1 octet) | > Secure_Path | pCount (1 octet) | > Secure_Path
+-------------------------------------------+ / +-------------------------------------------+ /
| Flags (1 octet) | ---/ | Flags (1 octet) | ---/
+-------------------------------------------+ +-------------------------------------------+
| Sig Field in the Next Segment (variable) | | Sig Field in the Next Segment (variable) |
+-------------- ----------------------------+ +-------------- ----------------------------+
For the first segment to be processed (the most recently added For the first segment to be processed (the most recently added
segment), the 'AS Number of Target AS' is the AS number of the BGPSEC segment), the 'AS Number of Target AS' is the AS number of the BGPsec
speaker validating the update message. Note that if a BGPSEC speaker speaker validating the update message. Note that if a BGPsec speaker
uses multiple AS Numbers (e.g., the BGPSEC speaker is a member of a uses multiple AS Numbers (e.g., the BGPsec speaker is a member of a
confederation), the AS number used here MUST be the AS number confederation), the AS number used here MUST be the AS number
announced in the OPEN message for the BGP session over which the announced in the OPEN message for the BGP session over which the
BGPSEC update was received. BGPsec update was received.
For each other Signature Segment, the 'AS Number of Target AS' is the For each other Signature Segment, the 'AS Number of Target AS' is the
AS number in the Secure_Path segment that corresponds to the AS number in the Secure_Path segment that corresponds to the
Signature Segment added immediately after the one being processed. Signature Segment added immediately after the one being processed.
(That is, in the Secure_Path segment that corresponds to the (That is, in the Secure_Path segment that corresponds to the
Signature segment that the validator just finished processing.) Signature segment that the validator just finished processing.)
The AS Number, pCount and Flags fields are taken from the Secure_Path The AS Number, pCount and Flags fields are taken from the Secure_Path
segment that corresponds to the Signature segment currently being segment that corresponds to the Signature segment currently being
processed. The 'Signature Field in the Next Segment' is the processed. The 'Signature Field in the Next Segment' is the
skipping to change at page 26, line 24 skipping to change at page 26, line 24
+------------------------------------+ +------------------------------------+
| Algorithm Suite Id. (1 octet) | | Algorithm Suite Id. (1 octet) |
+------------------------------------+ +------------------------------------+
| NLRI Length (1 octet) | | NLRI Length (1 octet) |
+------------------------------------+ +------------------------------------+
| NLRI Prefix (variable) | | NLRI Prefix (variable) |
+------------------------------------+ +------------------------------------+
The NLRI Length, NLRI Prefix, and Algorithm Suite Identifier are all The NLRI Length, NLRI Prefix, and Algorithm Suite Identifier are all
obtained in a straight forward manner from the NLRI of the update obtained in a straight forward manner from the NLRI of the update
message or the BGPSEC_Path attribute being validated. The Origin AS message or the BGPsec_Path attribute being validated. The Origin AS
Number, pCount, and Flags fields are taken from the Secure_Path Number, pCount, and Flags fields are taken from the Secure_Path
segment corresponding to the Signature Segment currently being segment corresponding to the Signature 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.)
skipping to change at page 27, line 6 skipping to change at page 27, line 6
validation algorithm determines that the signature is valid, then validation algorithm determines that the signature is valid, then
continue processing Signature Segments (within the current continue processing Signature Segments (within the current
Signature_Block). Signature_Block).
If all Signature Segments within a Signature_Block pass validation If all Signature Segments within a Signature_Block pass validation
(i.e., all segments are processed and the Signature_Block has not yet (i.e., all segments are processed and the Signature_Block has not yet
been marked 'Not Valid'), then the Signature_Block is marked as been marked 'Not Valid'), then the Signature_Block is marked as
'Valid'. 'Valid'.
If at least one Signature_Block is marked as 'Valid', 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 'Valid'. (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 'Valid' if the two Signature_Blocks then the update message is deemed 'Valid' if the
first Signature_Block is marked 'Valid' OR the second Signature_Block first Signature_Block is marked 'Valid' OR the second Signature_Block
is marked 'Valid'.) 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
(using BGP capabilities) between BGPSEC peers to use of a particular (using BGP capabilities) between BGPsec peers to use of a particular
(digest and signature) algorithm suite. This is because the algorithm (digest and signature) algorithm suite. This is because the algorithm
suite used by the sender of a BGPSEC update message must be 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 [11]. by all BGPsec speakers [11].
It is anticipated that, in the future mandatory, the algorithm suites It is anticipated that, in the future mandatory, the 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 a '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 attribute can contain signatures, in parallel, how the BGPsec_Path attribute can contain signatures, in parallel,
for two algorithm suites.) Once the transition is complete, use of for two algorithm suites.) Once the transition is complete, use of
the old 'current' algorithm will be deprecated, use of the 'new' the old 'current' algorithm will be deprecated, use of the 'new'
algorithm will be mandatory, and a subsequent 'even newer' algorithm algorithm will be mandatory, and a subsequent 'even newer' algorithm
suite may be specified as recommend to implement. Once the suite may be specified as recommend to implement. Once the
transition has successfully been completed in this manner, BGPSEC transition has successfully been completed in this manner, BGPsec
speakers SHOULD include only a single Signature_Block (corresponding speakers SHOULD include only a single Signature_Block (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 and thus substantial changes to the processing of the BGPsec_Path and thus
necessitate a new version of BGPSEC. Examples of such changes necessitate a new version of BGPsec. Examples of such 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_TWO, which is designed to accommodate the let's call it BGPsec_PATH_TWO, which is designed to accommodate the
desired changes to BGPSEC. In such a case, the mandatory algorithm desired changes to BGPsec. In such a case, the mandatory algorithm
suites document would be updated to specify algorithm suites suites document would be updated to specify algorithm 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 6.1. 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 attribute and the new BGPSEC_PATH_TWO attribute. Once BGPsec_Path attribute and the new BGPsec_PATH_TWO attribute. Once
the transition is complete, the use of BGPSEC_Path could then be the transition is complete, the use of BGPsec_Path could then be
deprecated, at which point BGPSEC speakers SHOULD include only the deprecated, at which point BGPsec speakers SHOULD include only the
new BGPSEC_PATH_TWO attribute. Such a process could facilitate a new BGPsec_PATH_TWO attribute. Such a process could facilitate a
transition to a new BGPSEC semantics in a backwards compatible transition to a new 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 a discussion of the BGPsec threat model and related security
considerations, please see [14]. considerations, please see [14].
7.1 Security Guarantees 7.1 Security Guarantees
When used in conjunction with Origin Validation (see [19] and [20]), When used in conjunction with Origin Validation (see [19] and [20]),
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, in the RPKI, by the IP address space holder to been authorized, in the RPKI, by the IP address space holder to
originate route advertisements for the given prefix. originate route advertisements for the given prefix.
o For each AS in the path, a BGPSEC speaker authorized by the holder o For each AS in the path, a BGPsec speaker authorized by the holder
of the AS number intentionally chose (in accordance with local of the AS number intentionally chose (in accordance with local
policy) to propagate the route advertisement to the subsequent AS policy) to propagate the route advertisement to the subsequent AS
in the 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 portion of the BGPSEC_Path attribute corresponds that the Secure_Path portion of the BGPsec_Path attribute corresponds
to a sequence of autonomous systems who have all agreed in principle to a sequence of autonomous systems who have all agreed in principle
to forward packets to the given prefix along the indicated path. (It to forward packets to the given prefix along the indicated path. (It
should be noted that BGPSEC does not offer any guarantee that the should be noted that BGPsec does not offer any guarantee that the
data packets would flow along the indicated path; it only guarantees data packets would flow along the indicated path; it only guarantees
that the BGP update conveying the path indeed propagated along the that the BGP update conveying the path indeed propagated along the
indicated path.) Furthermore, the recipient is assured that this indicated path.) Furthermore, the recipient is assured that this
path terminates in an autonomous system that has been authorized by path terminates in an autonomous system that has been authorized by
the IP address space holder as a legitimate destination for traffic the IP address space holder as a legitimate destination for traffic
to the given prefix. 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).
7.2 On the Removal of BGPSEC Signatures 7.2 On the Removal of BGPsec Signatures
There may be cases where a BGPSEC speaker deems 'Valid' (as per the There may be cases where a BGPsec speaker deems 'Valid' (as per the
validation algorithm in Section 5.2) a BGPSEC update message that validation algorithm in Section 5.2) a BGPsec update message that
contains both a 'Valid' and a 'Not Valid' Signature_Block. That is, contains both a 'Valid' and a 'Not Valid' Signature_Block. That is,
the update message contains two sets of signatures corresponding to the update message contains two sets of signatures corresponding to
two algorithm suites, and one set of signatures verifies correctly 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 a BGPSEC speaker choosing to propagate the protocol specifies that a BGPsec speaker choosing to propagate the
route advertisement in such an update message SHOULD add its route advertisement in such an update message SHOULD add its
signature to each of the Signature_Blocks. Thus the BGPSEC speaker signature to each of the Signature_Blocks. Thus the BGPsec speaker
creates a signature using both algorithm suites and creates a new creates a signature using both algorithm suites and creates a new
update message that contains both the 'Valid' and the 'Not Valid' set update message that contains both the 'Valid' and the 'Not Valid' set
of signatures (from its own vantage point). 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 'Valid' and a set of algorithm B of algorithm A signatures which are 'Valid' and a set of algorithm B
signatures which are 'Not Valid'. In such a case it is possible signatures which are 'Not Valid'. In such a case it is possible
(perhaps even likely, depending on the state of the algorithm (perhaps even likely, depending on the state of the algorithm
transition) that some of the BGPSEC speaker's peers (or other transition) that some of the BGPsec speaker's peers (or other
entities further 'downstream' in the BGP topology) do not support entities further 'downstream' in the BGP topology) do not support
algorithm A. Therefore, if the BGPSEC speaker were to remove the 'Not algorithm A. Therefore, if the BGPsec speaker were to remove the 'Not
Valid' set of signatures corresponding to algorithm B, such entities Valid' set of signatures corresponding to algorithm B, such entities
would treat the message as though it were unsigned. By including the would treat the message as though it were unsigned. By including the
'Not Valid' set of signatures when propagating a route advertisement, 'Not Valid' set of signatures when propagating a route advertisement,
the BGPSEC speaker ensures that 'downstream' entities have as much the BGPsec speaker ensures that 'downstream' entities have as much
information as possible to make an informed opinion about the information as possible to make an informed opinion about the
validation status of a BGPSEC update. 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
differently from BGPSEC updates that contain a single set of 'Not differently from BGPsec updates that contain a single set of 'Not
Valid' signatures. That is, by removing the set of 'Not Valid' Valid' signatures. That is, by removing the set of 'Not Valid'
signatures the BGPSEC speaker might actually cause a downstream signatures the BGPsec speaker might actually cause a downstream
entity to 'upgrade' the status of a route advertisement from 'Not entity to 'upgrade' the status of a route advertisement from 'Not
Valid' to unsigned. Finally, note that in the above scenario, the Valid' to unsigned. Finally, note that in the above scenario, the
BGPSEC speaker might have deemed algorithm A signatures 'Valid' only BGPsec speaker might have deemed algorithm A signatures 'Valid' only
because of some issue with RPKI state local to his AS (for example, because of some issue with RPKI state local to his AS (for example,
his AS might not yet have obtained a CRL indicating that a key used his AS might not yet have obtained a CRL indicating that a key used
to 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 Valid' (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
Valid' 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
path (to a given prefix) a route obtained via a 'Not Valid' BGPSEC path (to a given prefix) a route obtained via a 'Not Valid' BGPsec
update message. In such a case, the BGPSEC speaker should propagate a update message. In such a case, the BGPsec speaker should propagate a
signed BGPSEC update message, adding his signature to the 'Not Valid' signed BGPsec update message, adding his signature to the 'Not Valid'
signatures that already exist. Again, this is to ensure that signatures that already exist. Again, this is to ensure that
'downstream' entities are able to make an informed decision and not 'downstream' entities are able to make an informed decision and not
erroneously treat the route as unsigned. It should also be noted erroneously treat the route as unsigned. It should also be noted
that due to possible differences in RPKI data observed at different that due to possible differences in RPKI data observed at different
vantage points in the network, a BGPSEC update deemed 'Not Valid' at vantage points in the network, a BGPsec update deemed 'Not Valid' at
an upstream BGPSEC speaker may be deemed 'Valid' by another BGP an upstream BGPsec speaker may be deemed 'Valid' by another BGP
speaker downstream. speaker downstream.
Indeed, when a BGPSEC speaker signs an outgoing update message, it is Indeed, when a BGPsec speaker signs an outgoing update message, it is
not attesting to a belief that all signatures prior to its are valid. not attesting to a belief that all signatures prior to its are valid.
Instead it is merely asserting that: Instead it is merely asserting 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
o The BGPSEC speaker chose to propagate an advertisement for this o The BGPsec speaker chose to propagate an advertisement for this
route to the peer (implicitly) indicated by the 'Target AS' route to the peer (implicitly) indicated by the 'Target AS'
7.3 Mitigation of Denial of Service Attacks 7.3 Mitigation of Denial of Service Attacks
The BGPSEC update validation procedure is a potential target for The BGPsec update validation procedure is a potential target for
denial of service attacks against a BGPSEC speaker. To mitigate the denial of service attacks against a BGPsec speaker. Here we consider
effectiveness of such denial of service attacks, BGPSEC speakers the mitigation only of denial of service attacks that are specific to
should implement an update validation algorithm that performs BGPsec.
expensive checks (e.g., signature verification) after performing less
expensive checks (e.g., syntax checks). The validation algorithm To mitigate the effectiveness of such denial of service attacks,
specified in Section 5.2 was chosen so as to perform checks which are BGPsec speakers should implement an update validation algorithm that
likely to be expensive after checks that are likely to be performs expensive checks (e.g., signature verification) after
inexpensive. However, the relative cost of performing required performing less expensive checks (e.g., syntax checks). The
validation steps may vary between implementations, and thus the validation algorithm specified in Section 5.2 was chosen so as to
algorithm specified in Section 5.2 may not provide the best denial of perform checks which are likely to be expensive after checks that are
service protection for all implementations. likely to be inexpensive. However, the relative cost of performing
required validation steps may vary between implementations, and thus
the algorithm specified in Section 5.2 may not provide the best
denial of service protection for all implementations.
Additionally, sending update messages with very long AS paths (and
hence a large number of signatures) is a potential mechanism to
conduct denial of service attacks. For this reason, it is important
that an implementation of the validation algorithm stops attempting
to verify signatures as soon as an invalid signature is found. (This
ensures that long sequences of invalid signatures cannot be used for
denial of service attacks.) Furthermore, implementations can mitigate
such attacks by only performing validation on update messages that,
if valid, would be selected as the best path. That is, if an update
message contains a route that would lose out in best path selection
for other reasons (e.g., a very long AS path) then it is not
necessary to determine the BGPsec-validity status of the route.
7.4 Additional Security Considerations 7.4 Additional Security Considerations
The mechanism of setting the pCount field to zero is included in this The mechanism of setting the pCount field to zero is included in this
specification to enable route servers in the control path to specification to enable route servers in the control path to
participate in BGPSEC without increasing the effective length of the participate in BGPsec without increasing the effective length of the
AS-PATH. However, entities other than route servers could AS-PATH. However, entities other than route servers could
conceivably use this mechanism (set the pCount to zero) to attract conceivably use this mechanism (set the pCount to zero) to attract
traffic (by reducing the effective length of the AS-PATH) traffic (by reducing the effective length of the AS-PATH)
illegitimately. This risk is largely mitigated if every BGPSEC illegitimately. This risk is largely mitigated if every BGPsec
speaker drops incoming update messages that set pCount to zero but speaker drops incoming update messages that set pCount to zero but
come from a peer that is not a route server. However, note that a come from a peer that is not a route server. However, note that a
recipient of a BGPSEC update message within which an upstream entity recipient of a BGPsec update message within which an upstream entity
two or more hops away has set pCount to zero is unable to verify for two or more hops away has 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.
BGPSEC does not provide protection against attacks at the transport BGPsec does not provide protection against attacks at the transport
layer. An adversary on the path between a BGPSEC speaker and its layer. As with any BGP session, an adversary on the path between a
peer is able to perform attacks such as modifying valid BGPSEC BGPsec speaker and its peer is able to perform attacks such as
updates to cause them to fail validation, injecting (unsigned) BGP modifying valid BGPsec updates to cause them to fail validation,
update messages without BGPSEC_Path_Signature attributes, or injecting (unsigned) BGP update messages without
injecting BGPSEC update messages with BGPSEC_Path_Signature BGPsec_Path_Signature attributes, injecting BGPsec update messages
attributes that fail validation, or causing the peer to tear-down the with BGPsec_Path_Signature attributes that fail validation, or
BGP session. Therefore, BGPSEC sessions SHOULD be protected by causing the peer to tear-down the BGP session. The use of BGPsec does
appropriate transport security mechanisms. nothing to increase the power of an on-path adversary -- in
particular, even an on-path adversary cannot cause a BGPsec speaker
to believe a BGPsec-invalid route is valid. However, as with any BGP
session, BGPsec sessions SHOULD be protected by appropriate transport
security mechanisms.
8. IANA Considerations 8. IANA Considerations
TBD: Need IANA to assign numbers for the two capabilities and the TBD: Need IANA to assign numbers for the two capabilities and the
BGPSEC_PATH attribute. BGPsec_PATH attribute.
This document does not create any new IANA registries. This document does not create any new IANA registries.
9. Contributors 9. Contributors
9.1. Authors 9.1. Authors
Rob Austein Rob Austein
Dragon Research Labs Dragon Research Labs
sra@hactrn.net sra@hactrn.net
skipping to change at page 33, line 36 skipping to change at page 34, line 36
BGP-4", RFC 5492, February 2009. BGP-4", RFC 5492, February 2009.
[7] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure [7] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure
Internet Routing", RFC 6480, February 2012. Internet Routing", RFC 6480, February 2012.
[8] 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.
[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 (work in progress), BGP", draft-ietf-idr-bgp-extended-messages (work in progress),
January 2014. January 2015.
[10] 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", draft-ietf-sidr-bgpsec-pki-profiles Certification Requests", draft-ietf-sidr-bgpsec-pki-profiles
(work in progress), March 2014. (work in progress), November 2014.
[11] Turner, S., "BGP Algorithms, Key Formats, & Signature Formats", [11] Turner, S., "BGP Algorithms, Key Formats, & Signature Formats",
draft-ietf-sidr-bgpsec-algs (work in progress), July 2014. draft-ietf-sidr-bgpsec-algs (work in progress), July 2014.
[12] Scudder, J., Chen, E., Mohapatra, P., and K. Patel, "Revised [12] Scudder, J., Chen, E., Mohapatra, P., and K. Patel, "Revised
Error Handling for BGP UPDATE Messages", draft-ietf-idr-error- Error Handling for BGP UPDATE Messages", draft-ietf-idr-error-
handling (work in progress), June 2014. handling (work in progress), December 2014.
11. Informative References 11. Informative References
[13] Kumari, W. and K. Sriram, "Recommendation for Not Using AS_SET [13] Kumari, W. and K. Sriram, "Recommendation for Not Using AS_SET
and AS_CONFED_SET in BGP", RFC 6472, December 2011. and AS_CONFED_SET in BGP", RFC 6472, December 2011.
[14] Kent, S., "Threat Model for BGP Path Security", draft-ietf- [14] Kent, S. and A. Chi, "Threat Model for BGP Path Security", RFC
sidr-bgpsec-threats (work in progress), December 2013. 7132, February 2014.
[15] Bush, R. and R. Austein, "The Resource Public Key [15] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol", RFC 6810, January Infrastructure (RPKI) to Router Protocol", RFC 6810, January
2013. 2013.
[16] Bush, R., Patel, K., and S. Turner, "Router Key PDU for RPKI- [16] Bush, R., Patel, K., and S. Turner, "Router Key PDU for RPKI-
Router Protocol", draft-ymbk-rpki-rtr-keys (work in progress), Router Protocol", draft-ymbk-rpki-rtr-keys (work in progress),
April 2013. April 2013.
[17] Bush, R., "BGPsec Operational Considerations", draft-ietf-sidr- [17] Bush, R., "BGPsec Operational Considerations", draft-ietf-sidr-
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