draft-ietf-sidr-bgpsec-protocol-14.txt   draft-ietf-sidr-bgpsec-protocol-15.txt 
Network Working Group M. Lepinski, Ed. Network Working Group M. Lepinski, Ed.
Internet-Draft NCF Internet-Draft NCF
Intended status: Standards Track December 6, 2015 Intended status: Standards Track K. Sriram, Ed.
Expires: May 6, 2016 Expires: September 16, 2016 NIST
March 16, 2016
BGPsec Protocol Specification BGPsec Protocol Specification
draft-ietf-sidr-bgpsec-protocol-14 draft-ietf-sidr-bgpsec-protocol-15
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.
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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 . . . . . . . . . . . . . . . . . . 6 3. The BGPsec_Path Attribute . . . . . . . . . . . . . . . . . . 6
3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Secure_Path . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Signature_Block . . . . . . . . . . . . . . . . . . . . . 8 3.2. Signature_Block . . . . . . . . . . . . . . . . . . . . . 8
4. BGPsec Update Messages . . . . . . . . . . . . . . . . . . . . 10 4. BGPsec Update Messages . . . . . . . . . . . . . . . . . . . . 10
4.1. General Guidance . . . . . . . . . . . . . . . . . . . . . 10 4.1. General Guidance . . . . . . . . . . . . . . . . . . . . . 10
4.2. Constructing the BGPsec_Path Attribute . . . . . . . . . . 12 4.2. Constructing the BGPsec_Path Attribute . . . . . . . . . . 12
4.3. Processing Instructions for Confederation Members . . . . 15 4.3. Processing Instructions for Confederation Members . . . . 16
4.4. Reconstructing the AS_PATH Attribute . . . . . . . . . . . 18 4.4. Reconstructing the AS_PATH Attribute . . . . . . . . . . . 18
5. Processing a Received BGPsec Update . . . . . . . . . . . . . 19 5. Processing a Received BGPsec Update . . . . . . . . . . . . . 19
5.1. Overview of BGPsec Validation . . . . . . . . . . . . . . 20 5.1. Overview of BGPsec Validation . . . . . . . . . . . . . . 21
5.2. Validation Algorithm . . . . . . . . . . . . . . . . . . . 22 5.2. Validation Algorithm . . . . . . . . . . . . . . . . . . . 22
6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 25 6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 25
6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 25 6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 25
6.2. Extensibility Considerations . . . . . . . . . . . . . . . 25 6.2. Extensibility Considerations . . . . . . . . . . . . . . . 26
7. Security Considerations . . . . . . . . . . . . . . . . . . . 26 7. Security Considerations . . . . . . . . . . . . . . . . . . . 27
7.1 Security Guarantees . . . . . . . . . . . . . . . . . . . . 26 7.1 Security Guarantees . . . . . . . . . . . . . . . . . . . . 27
7.2 On the Removal of BGPsec Signatures . . . . . . . . . . . . 27 7.2 On the Removal of BGPsec Signatures . . . . . . . . . . . . 28
7.3 Mitigation of Denial of Service Attacks . . . . . . . . . . 29 7.3 Mitigation of Denial of Service Attacks . . . . . . . . . . 29
7.4 Additional Security Considerations . . . . . . . . . . . . . 29 7.4 Additional Security Considerations . . . . . . . . . . . . . 30
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 30 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 30 9.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 31 9.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 31
10. Normative References . . . . . . . . . . . . . . . . . . . . 31 10. Normative References . . . . . . . . . . . . . . . . . . . . 32
11. Informative References . . . . . . . . . . . . . . . . . . . 32 11. Informative References . . . . . . . . . . . . . . . . . . . 32
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][20] 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 [12] and address resources. (For more information on the RPKI, see [12] 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 [9] that corresponds to the BGPsec speaker's AS router certificate [9] that corresponds to the BGPsec speaker's AS
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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 MUST each address family) in the BGP OPEN message. A BGP speaker MUST
support the BGP multiprotocol extension [3]. Additionally, a BGP support the BGP multiprotocol extension [3]. Additionally, a BGP
speaker MUST NOT advertise the capability of BGPsec support for a speaker MUST NOT advertise the capability of BGPsec support for a
particular AFI unless it has also advertised the multiprotocol particular AFI unless it has also advertised the multiprotocol
extension capability for the same AFI combination [3]. extension capability for the same AFI [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
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than six times the number Secure_Path Segments (i.e., the number of than six times the number Secure_Path Segments (i.e., the number of
AS numbers in the path). AS numbers in the path).
The Secure_Path contains one Secure_Path Segment for each (distinct) The Secure_Path contains one Secure_Path Segment for each (distinct)
Autonomous System in the path to the originating AS of the NLRI Autonomous System in the path to the originating AS of the NLRI
specified in the update message. specified in the update message.
Secure_Path Segment Secure_Path Segment
+----------------------------+ +----------------------------+
| AS Number (4 octets) |
+----------------------------+
| pCount (1 octet) | | pCount (1 octet) |
+----------------------------+ +----------------------------+
| Flags (1 octet) | | Flags (1 octet) |
+----------------------------+ +----------------------------+
| AS Number (4 octets) |
+----------------------------+
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
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BGPsec_Path attribute. BGPsec_Path attribute.
Section 4.2 specifies how a BGPsec speaker generates the BGPsec_Path Section 4.2 specifies how a BGPsec speaker generates the BGPsec_Path
attribute to include in a BGPsec Update message. attribute to include in a BGPsec Update message.
Section 4.3 contains special processing instructions for members of Section 4.3 contains special processing instructions for members of
an autonomous system confederation [5]. A BGPsec speaker that is not an autonomous system confederation [5]. A BGPsec speaker that is not
a member of such a confederation MUST set the Flags field of the 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. Secure_Path Segment to zero in all BGPsec update messages it sends.
Section 4.4 contains instructions for reconstructing the AS_Path Section 4.4 contains instructions for reconstructing the AS_PATH
attribute in cases where a BGPsec speaker receives an update message attribute in cases where a BGPsec speaker receives an update message
with a BGPsec_Path attribute and wishes to propagate the update with a BGPsec_Path attribute and wishes to propagate the update
message to a peer who does not support BGPsec. message to a peer who does not support BGPsec.
4.1. General Guidance 4.1. General Guidance
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
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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. Additionally, a BGPsec update message update message for each NLRI. Additionally, a BGPsec update message
MUST use the MP_REACH_NLRI [3] attribute to encode the NLRI. MUST use the MP_REACH_NLRI [3] attribute to encode the NLRI.
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.
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 [9]. Note resource extension includes the BGPsec speaker's AS number [9]. 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
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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 [7]). It is expected that most to a given set of prefixes (see [7]). 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.
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 BGPsec-speaking peers.) its external BGPsec-speaking peers.)
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.
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populates the BGPsec_Path attribute by copying the BGPsec_Path populates the BGPsec_Path attribute by copying the BGPsec_Path
attribute from the received update message. That is, the BGPsec_Path attribute from the received update message. That is, the BGPsec_Path
attribute is copied verbatim. However, in the case that the BGPsec attribute is copied verbatim. However, in the case that the BGPsec
speaker is performing an AS Migration, the BGPsec speaker may add an speaker is performing an AS Migration, the BGPsec speaker may add an
additional signature on ingress before copying the BGPsec_Path additional signature on ingress before copying the BGPsec_Path
attribute (see [18] for more details). Note that when a BGPsec attribute (see [18] for more details). Note that when a BGPsec
speaker chooses to forward a BGPsec update message to an iBGP peer, speaker chooses to forward a BGPsec update message to an iBGP peer,
the BGPsec attribute SHOULD NOT be removed, unless the peer doesn't the BGPsec attribute SHOULD NOT be removed, unless the peer doesn't
support BGPsec. In particular, the BGPsec attribute SHOULD NOT be support BGPsec. In particular, the BGPsec attribute SHOULD NOT be
removed even in the case where the BGPsec update message has not been removed even in the case where the BGPsec update message has not been
that has not successfully validated. (See Section 5 for more successfully validated. (See Section 5 for more information on
information on validation, and Section 7 for the security validation, and Section 7 for the security ramifications of removing
ramifications of removing BGPsec signatures.) BGPsec signatures.)
4.2. Constructing the BGPsec_Path Attribute 4.2. Constructing the BGPsec_Path Attribute
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. Similarly, when sending a BGPsec advertisement for the same prefix. Similarly, when sending a
new route advertisement to an external, BGPsec-speaking peer, the new route advertisement to an external, BGPsec-speaking peer, the
BGPsec speaker may send a BGPsec Update message by generating a new BGPsec speaker may send a BGPsec Update message by generating a new
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The AS number in this Secure_Path segment MUST match the AS number in The AS number in this Secure_Path segment MUST match the AS number in
the AS number resource extension field of the Resource PKI router the AS number resource extension field of the Resource PKI router
certificate(s) that will be used to verify the digital signature(s) certificate(s) that will be used to verify the digital signature(s)
constructed by this BGPsec speaker [9]. constructed by this BGPsec speaker [9].
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).
greater than one permits this repetition without requiring a separate
digital signature for each repetition. To prevent unnecessary processing load in the validation of BGPsec
signatures, a BGPsec speaker SHOULD NOT produce multiple consecutive
Secure_Path Segments with the same AS number. This means that to
achieve the semantics of prepending the same AS number k times, a
BGPsec speaker SHOULD produce a single Secure_Path Segment -- with
pCount of k -- and a single corresponding Signature Segment.
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
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SHOULD include both of the Signature_Blocks. If the received BGPsec SHOULD include both of the Signature_Blocks. If the received BGPsec
update message contains two Signature_Blocks and the BGPsec speaker update message contains two Signature_Blocks and the BGPsec speaker
only supports one of the two corresponding algorithm suites, then the only supports one of the two corresponding algorithm suites, then the
BGPsec speaker MUST remove the Signature_Block corresponding to the BGPsec speaker MUST remove the Signature_Block corresponding to the
algorithm suite that it does not understand. If the BGPsec speaker algorithm suite that it does not understand. If the BGPsec speaker
does not support the algorithm suites in any of the Signature_Blocks does not support the algorithm suites in any of the Signature_Blocks
contained in the received update message, then the BGPsec speaker contained in the received update message, then the BGPsec speaker
MUST NOT propagate the route advertisement with the 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. See Section 4.4 for more information on converting to an
unsigned BGP 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
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the RPKI router certificate corresponding to the BGPsec speaker [9]. the RPKI router certificate corresponding to the BGPsec speaker [9].
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 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 For clarity, let us number the Secure_Path and corresponding
Number, and the newly-created Secure_Path Segment (Origin AS, Signature Segments from 1 to N as follows. Let Secure_Path Segment
pCount, and Flags). Note that the Target AS Number is the AS 1 and Signature Segment 1 be the segments produced by the origin
Number of the BGPsec peer to whom the newly-created Update message AS. Let Secure_Path Segment 2 and Signature Segment 2 be the
is being sent. Then (if the BGPsec speaker is not the origin AS) segments added by the next AS after the origin. Continue this
append to this sequence previous Secure_Path and the previous method of numbering and ultimately let Secure_Path Segment N be
Signature_Block that were present on the received Update message. the Secure_Path segment that is being added by the current AS.
Finally, append the Address Family Identifier (AFI), Subsequent
Address Family Identifier (SAFI), and Network Layer Reachability
Information (NLRI) fields from the MP_REACH_NLRI attribute.
Additionally, in the Prefix field of the NLRI (from
MP_REACH_NLRI), all of the trailing bits MUST be set to zero when
constructing this sequence. In this sequence, the Target AS Number
is the AS to whom the BGPsec speaker intends to send the update
message. (Note 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 sent.)
Sequence of Octets to be Signed o In order to constructe the digital signature for Signature Segment
+-------------------------------------+ N (the signature segment being produced by the current AS), first
| Target AS Number (4 octets) | construct the following sequence of octets to be hashed.
+-------------------------------------+
| AS Number (4 octets) | Sequence of Octets to be Hashed
+-------------------------------------+ +------------------------------------+
| pCount (1 octet) | | Target AS Number |
+-------------------------------------+ +------------------------------------+ -\
| Flags (1 octet) | | Signature Segment : N-1 | \
+-------------------------------------+ +------------------------------------+ |
| Previous Secure_Path (variable) | | Secure_Path Segment : N | |
+-------------------------------------+ +------------------------------------+ \
| Previous Signature_Block (variable) | ... > For N Hops
+-------------------------------------+ +------------------------------------+ /
| AFI (2 octets) | ---\ | Signature Segment : 1 | |
+-------------------------------------+ \ +------------------------------------+ |
| SAFI (1 octet) | > MP_REACH_NLRI | Secure_Path Segment : 2 | /
+-------------------------------------+ / +------------------------------------+ -/
| NLRI (variable) | ---/ | Secure_Path Segment : 1 |
+-------------------------------------+ +------------------------------------+
| Algorithm Suite Identifier |
+------------------------------------+
| AFI |
+------------------------------------+
| SAFI |
+------------------------------------+
| NLRI |
+------------------------------------+
In this sequence, the Target AS Number is the AS to whom the
BGPsec speaker intends to send the update message. (Note 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 sent.)
The Secure_Path and Signature Segments (1 through N-1) are
obtained from the BGPsec_Path attribute. Finally, the Address
Family Identifier (AFI), Subsequent Address Family Identifier
(SAFI), and Network Layer Reachability Information (NLRI) fields
are obtained from the MP_REACH_NLRI attribute. Additionally, in
the Prefix field of the NLRI (from MP_REACH_NLRI), all of the
trailing bits MUST be set to zero when constructing this sequence.
In this sequence, the Target AS Number is the AS to whom the
BGPsec speaker intends to send the update message. (Note 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 sent.)
o Apply to this octet sequence the digest algorithm (for the o Apply to this octet sequence the digest algorithm (for the
algorithm suite of this Signature_Block) to obtain a digest value. algorithm suite of this Signature_Block) to obtain a digest value.
o Apply to this digest value the signature algorithm, (for the o Apply to this digest value the signature algorithm, (for the
algorithm suite of this Signature_Block) to obtain the digital algorithm suite of this Signature_Block) to obtain the digital
signature. Then populate the Signature Field with this digital signature. Then populate the Signature Field with this digital
signature. signature.
The Signature Length field is populated with the length (in octets) The Signature Length field is populated with the length (in octets)
of the Signature field. of the value in 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. Additionally, in
a confederation member sends a BGPsec update message to a peer that this case, the confederation member that generates the Secure_Path
is a member of the same confederation, the BGPsec speaker that Segment sets the Confed_Segment flag to one. This means that in a
generates the Secure_Path Segment sets the Confed_Segment flag to BGPsec update message, an AS number appears in a Secure_Path Segment
one. This means that in a BGPsec update message, an AS number with the Confed_Segment flag set whenever, in a non-BGPsec update
appears in a Secure_Path Segment with the Confed_Segment flag set message, the AS number would appear in a segment of type
whenever, in a non-BGPsec update message, the AS number would appear AS_CONFED_SEQUENCE.
in a segment of type AS_CONFED_SEQUENCE in a non-BGPsec update
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 Section
4.1 and 4.2). Note that if a confederation chooses not to verify 4.2). Note that if a confederation chooses not to verify digital
digital signatures within the confederation, then BGPsec is able to signatures within the confederation, then BGPsec is able to provide
provide no assurances about the integrity of the (private) Member-AS no assurances about the integrity of the (private) Member-AS Numbers
Numbers placed in Secure_Path segments where the Confed_Segment flag placed in Secure_Path segments where the Confed_Segment flag is set
is set to one. 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 segment, 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
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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 4.2.
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 the following. For a Segment, the confederation member must note the following. For a
signature produced by a peer BGPsec speaker outside of a signature produced by a peer BGPsec speaker outside of a
confederation, the Target AS will always be the AS Confederation confederation, the Target AS will always be the AS Confederation
Identifier (the public AS number of the confederation) as opposed to Identifier (the public AS number of the confederation) as opposed to
the Member-AS Number. the Member-AS Number.
skipping to change at page 17, line 51 skipping to change at page 18, line 19
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 [11].) defined in RFC 7606 [11].)
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. Before
attempting to reconstruct an AS_PATH for the purpose of forwarding an
unsigned (non-BGPsec) update to a peer, a BGPsec speaker MUST perform
the basic integrity checks listed in Section 5.2 to ensure that the
received BGPsec update is properly formed.
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.
skipping to change at page 19, line 44 skipping to change at page 20, line 18
exceptional conditions (e.g., the BGPsec speaker receives an exceptional conditions (e.g., the BGPsec speaker receives an
incredibly large number of update messages at once) a BGPsec speaker incredibly large number of update messages at once) a BGPsec speaker
MAY temporarily defer validation of incoming BGPsec update messages. MAY temporarily defer validation of incoming BGPsec update messages.
The treatment of such BGPsec update messages, whose validation has The treatment of such BGPsec update messages, whose validation has
been deferred, is a matter of local policy. However, an been deferred, is a matter of local policy. However, an
implementation SHOULD ensure that deferment of validation and status implementation SHOULD ensure that deferment of validation and status
of deferred messages is visible to the operator. of deferred messages is visible to the operator.
The validity of BGPsec update messages is a function of the current The validity of BGPsec update messages is a function of the current
RPKI state. When a BGPsec speaker learns that RPKI state has changed 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 RPKI-to-Router protocol
BGPsec speaker MUST re-run validation on all affected update messages [15]), the BGPsec speaker MUST re-run validation on all affected
stored in its ADJ-RIB-IN. That is, when a given RPKI certificate update messages stored in its ADJ-RIB-IN. That is, when a given RPKI
ceases to be valid (e.g., it expires or is revoked), all update certificate ceases to be valid (e.g., it expires or is revoked), all
messages containing a signature whose SKI matches the SKI in the update messages containing a signature whose SKI matches the SKI in
given certificate must be re-assessed to determine if they are still the given certificate must be re-assessed to determine if they are
valid. If this reassessment determines that the validity state of an still valid. If this reassessment determines that the validity state
update has changed then, depending on local policy, it may be of an 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.
skipping to change at page 20, line 49 skipping to change at page 21, line 22
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. In particular, it is necessary that the recipient have
particular, to validate update messages containing the BGPsec_Path access to the following data obtained from valid RPKI certificates:
attribute, it is necessary that the recipient have access to the the AS Number, Public Key and Subject Key Identifier from each valid
following data obtained from valid RPKI certificates and ROAs: RPKI router certificate.
o For each valid RPKI router certificate, the AS Number, Public Key
and Subject Key Identifier are required,
o For each valid ROA, the AS Number and the list of IP address
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 on its own and extract the required data, or it could
could receive the same data from a trusted cache that performs RPKI 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. That said, BGP route used as an input to BGP route selection. That said, BGP route
selection, and thus the handling of the validation states is a matter selection, and thus the handling of the validation states is a matter
of local policy, and is handled using local policy mechanisms. of local policy, and is handled using local policy mechanisms.
Implementations SHOULD enable operators to set such local policy on a Implementations SHOULD enable operators to set such local policy on a
per-session basis. (That is, we expect some operators will choose to per-session basis. (That is, we expect some operators will choose to
treat BGPSEC validation status differently for update messages treat BGPsec validation status differently for update messages
received over different BGP sessions.) received over different BGP sessions.)
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
skipping to change at page 22, line 42 skipping to change at page 23, line 8
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 [11]. BGPsec speakers MUST handle these handled as per RFC 7606 [11]. 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 7606
[11]. [11].
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 0): For clarity, let us number the Secure_Path and
corresponding Signature Segments from 1 to N as follows. Let
Secure_Path Segment 1 and Signature Segment 1 be the segments
produced by the origin AS. Let Secure_Path Segment 2 and Signature
Segment 2 be the segments added by the next AS after the origin.
Continue this method of numbering and ultimately let Signature
Segment N be the Signature Segment that is currently be verified
and let Secure_Path Segment N be the corresponding Secure_Path
Segment.
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
mark the entire Signature_Block as 'Not Valid' and proceed to the mark the entire Signature_Block as 'Not Valid' and proceed to the
next Signature_Block. next Signature_Block.
o (Step II): Compute the digest function (for the given algorithm o (Step II): Compute the digest function (for the given algorithm
suite) on the appropriate data. suite) on the appropriate data.
Sequence of Octets to be Hashed In order to verify the digital signature in Signature Segment N,
+-------------------------------------+ construct the following sequence of octets to be hashed.
| AS Number of Target (4 octets) |
+-------------------------------------+
| AS Number (4 octets) |
+-------------------------------------+
| pCount (1 octet) |
+-------------------------------------+
| Flags (1 octet) |
+-------------------------------------+
| Rest of Secure_Path (variable) |
+-------------------------------------+
| Rest of Signature_Block (variable) |
+-------------------------------------+
| AFI (2 octets) | ---\
+-------------------------------------+ \
| SAFI (1 octet) | > MP_REACH_NLRI
+-------------------------------------+ /
| NLRI (variable) | ---/
+-------------------------------------+
For the first segment to be processed (the most recently added Sequence of Octets to be Hashed
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 | Target AS Number |
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 | Signature Segment : N-1 | \
announced in the OPEN message for the BGP session over which the +------------------------------------+ |
BGPsec update was received. | Secure_Path Segment : N | |
+------------------------------------+ \
... > For N Hops
+------------------------------------+ /
| Signature Segment : 1 | |
+------------------------------------+ |
| Secure_Path Segment : 2 | /
+------------------------------------+ -/
| Secure_Path Segment : 1 |
+------------------------------------+
| Algorithm Suite Identifier |
+------------------------------------+
| AFI |
+------------------------------------+
| SAFI |
+------------------------------------+
| NLRI |
+------------------------------------+
For each other Signature Segment, the 'AS Number of Target AS' is the For the first segment to be processed (the most recently added
AS number in the Secure_Path segment that corresponds to the segment), the 'Target AS Number' is the AS number of the BGPsec
Signature Segment added immediately after the one being processed. speaker validating the update message. Note that if a BGPsec
(That is, in the Secure_Path segment that corresponds to the speaker uses multiple AS Numbers (e.g., the BGPsec speaker is a
Signature segment that the validator just finished processing.) member of a confederation), the AS number used here MUST be the AS
number announced in the OPEN message for the BGP session over
which the BGPsec update was received.
The AS Number, pCount and Flags fields are taken from the Secure_Path For each other Signature Segment, the 'Target AS Number' is the AS
segment that corresponds to the Signature segment currently being number in the Secure_Path segment that corresponds to the
processed. The 'Rest of Secure_Path' is obtained by removing from Signature Segment added immediately after the one being processed.
the Secure_Path the segment that is currently being processes. That (That is, in the Secure_Path segment that corresponds to the
is, 'Rest of Secure_Path' is what the Secure_Path would have Signature segment that the validator just finished processing.)
contained before the currently processed segment was added.
Similarly, the 'Rest of Signature_Block' is obtained by removing from
the Signature_Block the Signature Segment corresponding to the
current Secure_Path Segment. That is, 'Rest of Signature_Block' is
what the Signature_Block would have contained before the currently
processed segment was added.
The Address Family Identifier (AFI), Subsequent Address Family Additionally, the Secure_Path and Signature Segment are obtained
Identifier (SAFI), and Network Layer Reachability Information (NLRI) from the BGPsec_Path attribute. The Address Family Identifier
are obtained directly from the MP_REACH_NLRI attribute of the update (AFI), Subsequent Address Family Identifier (SAFI), and Network
message. However, in the Prefix field of the NLRI (from Layer Reachability Information (NLRI) fields are obtained from the
MP_REACH_NLRI), all of the trailing bits MUST be set to zero for the MP_REACH_NLRI attribute. Additionally, in the Prefix field of the
purpose of signature verification. NLRI (from MP_REACH_NLRI), all of the trailing bits MUST be set to
zero when constructing this sequence. In this sequence, the Target
AS Number is the AS to whom the BGPsec speaker intends to send the
update message. (Note 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 sent.)
o (Step III): Use the signature validation algorithm (for the given o (Step III): Use the signature validation algorithm (for the given
algorithm suite) to verify the signature in the current segment. algorithm suite) to verify the signature in the current segment.
That is, invoke the signature validation algorithm on the That is, invoke the signature validation algorithm on the
following three inputs: the value of the Signature field in the following three inputs: the value of the Signature field in the
current segment; the digest value computed in Step II above; and current segment; the digest value computed in Step II above; and
the public key obtained from the valid RPKI data in Step I above. the public key obtained from the valid RPKI data in Step I above.
If the signature validation algorithm determines that the If the signature validation algorithm determines that the
signature is invalid, then mark the entire Signature_Block as 'Not signature is invalid, then mark the entire Signature_Block as 'Not
Valid' and proceed to the next Signature_Block. If the signature Valid' and proceed to the next Signature_Block. If the signature
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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 exists which
which specifies a mandatory-to-use 'current' algorithm suite for use specifies a mandatory-to-use 'current' algorithm suite for use by all
by all BGPsec speakers [10]. BGPsec speakers [10].
We anticipate that, in the future, the mandatory algorithm suites We anticipate that, in the future, the mandatory algorithm suites
document will be updated to specify a transition from the 'current' document will be updated to specify a transition from the 'current'
algorithm suite to 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'
skipping to change at page 27, line 10 skipping to change at page 27, line 32
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 update propagated via the sequences ASes listed in the
to a sequence of autonomous systems who have all agreed in principle Secure_Path portion of the BGPsec_Path attribute. (It should be noted
to forward packets to the given prefix along the indicated path. (It that BGPsec does not offer any guarantee that the data packets would
should be noted that BGPsec does not offer any guarantee that the flow along the indicated path; it only guarantees that the BGP update
data packets would flow along the indicated path; it only guarantees conveying the path indeed propagated along the indicated path.)
that the BGP update conveying the path indeed propagated along the Furthermore, the recipient is assured that this path terminates in an
indicated path.) Furthermore, the recipient is assured that this autonomous system that has been authorized by the IP address space
path terminates in an autonomous system that has been authorized by holder as a legitimate destination for traffic to the given prefix.
the IP address space holder as a legitimate destination for traffic
to the given prefix.
Note that although BGPsec provides a mechanism for an AS to validate Note that although BGPsec provides a mechanism for an AS to validate
that a received update message has certain security properties, the that a received update message has certain security properties, the
use of such a mechanism to influence route selection is completely a use of such a mechanism to influence route selection is completely a
matter of local policy. Therefore, a BGPsec speaker can make no matter of local policy. Therefore, a BGPsec speaker can make no
assumptions about the validity of a route received from an external assumptions about the validity of a route received from an external
BGPsec peer. That is, a compliant BGPsec peer may (depending on the BGPsec peer. That is, a compliant BGPsec peer may (depending on the
local policy of the peer) send update messages that fail the validity local policy of the peer) send update messages that fail the validity
test in Section 5. Thus, a BGPsec speaker MUST completely validate test in Section 5. Thus, a BGPsec speaker MUST completely validate
all BGPsec update messages received from external peers. (Validation all BGPsec update messages received from external peers. (Validation
skipping to change at page 30, line 19 skipping to change at page 30, line 39
injecting (unsigned) BGP update messages without injecting (unsigned) BGP update messages without
BGPsec_Path_Signature attributes, injecting BGPsec update messages BGPsec_Path_Signature attributes, injecting BGPsec update messages
with BGPsec_Path_Signature attributes that fail validation, or with BGPsec_Path_Signature attributes that fail validation, or
causing the peer to tear-down the BGP session. The use of BGPsec does causing the peer to tear-down the BGP session. The use of BGPsec does
nothing to increase the power of an on-path adversary -- in nothing to increase the power of an on-path adversary -- in
particular, even an on-path adversary cannot cause a BGPsec speaker particular, even an on-path adversary cannot cause a BGPsec speaker
to believe a BGPsec-invalid route is valid. However, as with any BGP to believe a BGPsec-invalid route is valid. However, as with any BGP
session, BGPsec sessions SHOULD be protected by appropriate transport session, BGPsec sessions SHOULD be protected by appropriate transport
security mechanisms. security mechanisms.
One might be concerned about a potential attack in which an adversary
replays a valid signature on an origin Secure_Path segment as though
it were a signature on later Secure_Path segment (in a different
update message). The only way such an attack could succeed would be
if a structure of bits to be signed in Section 4.1 (origin segment)
could also be parsed as a valid sequence of bits to be signed in
Section 4.2 (later segment). This, in particular, would require that
the length of the two structures match exactly, which cannot happen
given the current choice of algorithms in [10]. We do not expect this
to be a problem with future signature algorithms, as it is likely
that signatures will get longer (instead of shorter) over time.
However, authors of future revisions of the algorithms document [10]
should take care to ensure that this attack remains infeasible.
8. IANA Considerations 8. IANA Considerations
This document registers a new capability in the registry of BGP This document registers a new capability in the registry of BGP
Capabilities. The description for the new capability is "BGPsec Capabilities. The description for the new capability is "BGPsec
Capability". The reference for the new capability is this document Capability". The reference for the new capability is this document
(i.e., the RFC that replaces draft-ietf-sidr-bgpsec-protocol). (i.e., the RFC that replaces draft-ietf-sidr-bgpsec-protocol).
This document registers a new path attribute in the registry of BGP This document registers a new path attribute in the registry of BGP
Path Attributes. The code for this new attribute is "BGPsec_PATH". Path Attributes. The code for this new attribute is "BGPsec_PATH".
The reference for the new capability is this document (i.e., the RFC The reference for the new capability is this document (i.e., the RFC
skipping to change at page 31, line 44 skipping to change at page 31, line 51
Kotikalapudi Sriram Kotikalapudi Sriram
USA National Institute of Standards and Technology USA National Institute of Standards and Technology
kotikalapudi.sriram@nist.gov kotikalapudi.sriram@nist.gov
Samuel Weiler Samuel Weiler
Parsons Parsons
weiler+ietf@watson.org weiler+ietf@watson.org
9.2. Acknowledgements 9.2. Acknowledgements
The authors would like to thank Michael Baer, Luke Berndt, Sharon The authors would like to thank Michael Baer, Luke Berndt, Oliver
Goldberg, Ed Kern, David Mandelberg, Doug Maughan, Pradosh Mohapatra, Borchet, Wes George, Jeff Haas, Sharon Goldberg, Ed Kern, David
Chris Morrow, Russ Mundy, Sandy Murphy, Keyur Patel, Mark Reynolds, Mandelberg, Doug Maughan, Pradosh Mohapatra, Chris Morrow, Russ
Heather Schiller, Jason Schiller, John Scudder, Ruediger Volk and Mundy, Sandy Murphy, Keyur Patel, Mark Reynolds, Heather Schiller,
David Ward for their valuable input and review. Jason Schiller, John Scudder, Ruediger Volk and David Ward for their
valuable input and review.
10. Normative References 10. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border [2] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
Gateway Protocol 4", RFC 4271, January 2006. Gateway Protocol 4", RFC 4271, January 2006.
[3] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, [3] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
skipping to change at page 32, line 28 skipping to change at page 32, line 34
Confederations for BGP", RFC 5065, August 2007. Confederations for BGP", RFC 5065, August 2007.
[6] Scudder, J. and R. Chandra, "Capabilities Advertisement with [6] Scudder, J. and R. Chandra, "Capabilities Advertisement with
BGP-4", RFC 5492, February 2009. BGP-4", RFC 5492, February 2009.
[7] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route [7] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)", RFC 6482, February 2012. Origin Authorizations (ROAs)", RFC 6482, February 2012.
[8] Patel, K., Ward, D., and R. Bush, "Extended Message support for [8] 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 2015. July 2015.
[9] Reynolds, M., Turner, S., and S. Kent, "A Profile for BGPsec [9] 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), November 2014. (work in progress), November 2015.
[10] Turner, S., "BGP Algorithms, Key Formats, & Signature Formats", [10] 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), November 2015.
[11] Scudder, J., Chen, E., Mohapatra, P., and K. Patel, "Revised [11] 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), December 2014. handling (work in progress), August 2015.
11. Informative References 11. Informative References
[12] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure [12] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure
Internet Routing", RFC 6480, February 2012. Internet Routing", RFC 6480, February 2012.
[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. and A. Chi, "Threat Model for BGP Path Security", RFC [14] Kent, S. and A. Chi, "Threat Model for BGP Path Security", RFC
7132, February 2014. 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. November 2015.
[17] Bush, R., "BGPsec Operational Considerations", draft-ietf-sidr- [17] Bush, R., "BGPsec Operational Considerations", draft-ietf-sidr-
bgpsec-ops (work in progress), May 2012. bgpsec-ops (work in progress), December 2015.
[18] George, W. and S. Murphy, "BGPsec Considerations for AS [18] George, W. and S. Murphy, "BGPsec Considerations for AS
Migration", draft-ietf-sidr-as-migration (work in progress), Migration", draft-ietf-sidr-as-migration (work in progress),
July 2014. October 2015.
[19] Huston, G. and G. Michaelson, "Validation of Route Origination [19] Huston, G. and G. Michaelson, "Validation of Route Origination
Using the Resource Certificate Public Key Infrastructure (PKI) Using the Resource Certificate Public Key Infrastructure (PKI)
and Route Origin Authorizations (ROAs)", RFC 6483, February and Route Origin Authorizations (ROAs)", RFC 6483, February
2013. 2013.
[20] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. Austein, [20] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. Austein,
"BGP Prefix Origin Validation", RFC 6811, January 2013. "BGP Prefix Origin Validation", RFC 6811, January 2013.
Author's Address Author's Address
Matthew Lepinski (editor) Matthew Lepinski (editor)
New College of Florida New College of Florida
5800 Bay Shore Road 5800 Bay Shore Road
Sarasota, FL 34243 Sarasota, FL 34243
US USA
Phone: +1 941 487 5000
Email: mlepinski@ncf.edu Email: mlepinski@ncf.edu
Kotikalapudi Sriram (editor)
National Institute of Standards and Technology
100 Bureau Drive
Gaithersburg, MD 20899
USA
Email: kotikalapudi.sriram@nist.gov
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