Simplified Local internet nUmber Resource Management with the RPKI (SLURM)

The Resource Public Key Infrastructure (RPKI) is a global authorization infrastructure that allows the holder of Internet Number Resources (INRs) to make verifiable statements about those resources. For example, the holder of a block of IP(v4 or v6) addresses can issue a Route Origin Authorization (ROA) to authorize an Autonomous System (AS) to originate routes for that block. Internet Service Providers (ISPs) can then use the RPKI to validate BGP routes. (Validation of the origin of a route is described in , and validation of the path of a route is described in .) However, an "RPKI relying party" (RP) may want to override some of the information expressed via configured Trust Anchors (TAs) and the certificates downloaded from the RPKI repository system. For instances, recommends the creation of ROAs that would invalidate public routes for reserved and unallocated address space, yet some ISPs might like to use BGP and the RPKI with private address space (, , ) or private AS numbers (, ). Local use of private address space and/or AS numbers is consistent with the RFCs cited above, but such use cannot be verified by the global RPKI. This motivates creation of mechanisms that enable a network operator to publish exception to the RPKI in the form of filters and additions (for its own use and that of its customers) at its discretion. Additionally, a network operator might wish to make use of a local override capability to protect routes from adverse actions , until the results of such actions have been addressed. The mechanisms developed to provide this capability to network operators are hereby called Simplified Local internet nUmber Resource Management with the RPKI (SLURM). SLURM allows an operator to create a local view of the global RPKI by generating sets of assertions. For Origin Validation , an assertion is a tuple of {IP prefix, prefix length, maximum length, AS number (ASN)} as used by rpki-rtr (the RPKI to Router Protocol) version 0 and rpki-rtr version 1 . For BGPsec , an assertion is a tuple of {ASN, subject key identifier, router public key} as used by rpki-rtr version 1. (For the remainder of this document, these assertions are called ROA Prefix Assertions and BGPsec Assertions, respectively.)

The key words "MUST", "MUST NOT","REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

SLURM provides a simple way to enable an RP to establish a local, customized view of the RPKI, by overriding RPKI repository data if needed. To that end, an RP with SLURM filters out (removes from consideration for routing decisions) any assertions in the RPKI that are overridden by local ROA Prefix Assertions and BGPsec Assertions. In general, the primary output of an RP is the data it sends to routers over the rpki-rtr protocol . The rpki-rtr protocol enables routers to query an RP for all assertions it knows about (Reset Query) or for an update of only the changes in assertions (Serial Query). The mechanisms specified in this document are to be applied to the result set for a Reset Query, and to both the old and new sets that are compared for a Serial Query. RP software may modify other forms of output in comparable ways, but that is outside the scope of this document.

Local cache of RPKI objects+---> Validation | | | | | | | +--------------+ +---------------------------+ +-----+------+ | +-------------------------------------------------+ | +------v-------+ +------------+ +----------+ +-------------+ | | | | | | | | | SLURM +---> SLURM +---> rpki-rtr +---> BGP Speakers| | Filters | | Assertions | | | | | +--------------+ +------------+ +----------+ +-------------+ ]]>

SLURM filters and assertions are specified in JSON format. JSON members that are not defined here MUST NOT be used in SLURM Files. An RP MUST consider any deviations from the specification errors. Future additions to the specifications in this document MUST use an incremented value for the "slurmVersion" member.

A SLURM file consists of a single JSON object containing the following members: A "slurmVersion" member that MUST be set to 1, encoded as a number A "validationOutputFilters" member (), whose value is an object. The object MUST contain exactly two members: A "prefixFilters" member, whose value is described in . A "bgpsecFilters" member, whose value is described in . A "locallyAddedAssertions" member (), whose value is an object. The object MUST contain exactly two members: A "prefixAssertions" member, whose value is described in . A "bgpsecAssertions" member, whose value is described in . In the envisioned typical use case, an RP uses both Validation Output Filters and Locally Added Assertions. In this case, the resulting assertions MUST be the same as if output filtering were performed before locally adding assertions. i.e. locally added assertions MUST NOT be removed by output filtering. The following JSON structure with JSON members represents a SLURM file that has no filters or assertions:

The RP can configure zero or more Validated ROA Prefix Filters (Prefix Filters in short). Each Prefix Filter can contain either an IPv4 or IPv6 prefix and/or an ASN. It is RECOMMENDED that an explanatory comment is included with each Prefix Filter, so that it can be shown to users of the RP software. The above is expressed as a value of the "prefixFilters" member, as an array of zero or more objects. Each object MUST contain one of either, or one each of both following members: A "prefix" member, whose value is string representing either an IPv4 prefix (Section 3.1 of ) or an IPv6 prefix (). An "asn" member, whose value is a number. In addition, each object MAY contain one optional "comment" member, whose value is a string. The following example JSON structure represents a "prefixFilters" member with an array of example objects for each use case listed above:

Any Validated ROA Prefix (VRP, ) that matches any configured Prefix Filter MUST be removed from the RP's output. A VRP is considered to match with a Prefix Filter if one of the following cases applies: If the Prefix Filter contains an IPv4 or IPv6 Prefix only, the VRP is considered to match the filter if the VRP prefix is equal to or covered by the Prefix Filter prefix. If Prefix Filter contains an ASN only, the VRP is considered to match the filter if the VRP ASN matches the Prefix Filter ASN. If Prefix Filter contains both an IPv4 or IPv6 prefix and an ASN, the VRP is considered to match if the VRP prefix is equal to or covered by the Prefix Filter prefix and the VRP ASN matches the Prefix Filter ASN.

The RP can configure zero or more BGPsec Assertion Filters (BGPsec Filters in short). Each BGPsec Filter can contain an ASN and/or the Base64 encoding of a Router Subject Key Identifier (SKI), as described in and . It is RECOMMENDED that an explanatory comment is also included with each BGPSec Filter, so that it can be shown to users of the RP software. The above is expressed as a value of the "bgpsecFilters" member, as an array of zero or more objects. Each object MUST contain one of either, or one each of both following members: An "asn" member, whose value is a number An "SKI" member, whose value is the Base64 encoding without trailing ‘=‘ (Section 5 of ) of the certificate’s Subject Public Key as described in Section 4.8.2. of (This is the value of the ASN.1 OCTET STRING without the ASN.1 tag or length fields.) In addition, each object MAY contain one optional "comment" member, whose value is a string. The following example JSON structure represents a "bgpsecFilters" member with an array of example objects for each use case listed above:

", "comment": "Key matching Router SKI" }, { "asn": 64497, "SKI": "", "comment": "Key for ASN 64497 matching Router SKI" } ] ]]> Any BGPsec Assertion that matches any configured BGPsec Filter MUST be removed from the RP's output. A BGPsec Assertion is considered to match with a BGPsec Filter if one of the following cases applies: If the BGPsec Filter contains an ASN only, a BGPsec Assertion is considered to match if the Assertion ASN matches the Filter ASN. If the BGPsec Filter contains an SKI only, a BGPsec Assertion is considered to match if the Assertion Router SKI matches the Filter SKI. If the BGPsec Filter contains both an ASN and a Router SKI, then a BGPsec Assertion is considered to match if both the Assertion ASN matches the Filter ASN and the Assertion Router SKI matches the Filter Router SKI.

Each RP is locally configured with a (possibly empty) array of ROA Prefix Assertions (Prefix Assertion in short). Each ROA Prefix Assertion MUST contain an IPv4 or IPv6 prefix and an ASN. It MAY include a value for the maximum length. It is RECOMMENDED that an explanatory comment is also included with each, so that it can be shown to users ofthe RP software. The above is expressed as a value of the "prefixAssertions" member, as an array of zero or more objects. Each object MUST contain one each of both following members: A "prefix" member, whose value is string representing either an IPv4 prefix (Section 3.1 of ) or an IPv6 prefix (). An "asn" member, whose value is a number. In addition, each object MAY contain one of each of the following members: A "maxPrefixLength" member, whose value is a number. A "comment" member, whose value is a string. The following example JSON structure represents a "prefixAssertions" member with an array of example objects for each use case listed above:

Note that the combination of the prefix, ASN and optional maximum length describes a VRP as described in . The RP MUST add all Prefix Assertions found this way to the VRP found through RPKI validation, and ensure that it sends the complete set of PDUs, excluding duplicates when using the rpki-rtr protocol, see Section 5.6 and 5.7 of .

Each RP is locally configured with a (possibly empty) array of BGPsec Assertions. Each BGPsec Assertion MUST contain an AS number, a Router SKI, and the Router Public Key. It is RECOMMENDED that an explanatory comment is also included, so that it can be shown to users of the RP software. The above is expressed as a value of the "bgpsecAssertions" member, as an array of zero or more objects. Each object MUST contain one each of all of the following members: An "asn" member, whose value is a number. An "SKI" member, whose value is the Base64 encoding without trailing ‘=‘ (Section 5 of RFC4648 ) of the router’s public key equivalent to a certificate’s Subject Public Key as described in Section 4.8.2. of . This is the value of the ASN.1 OCTET STRING without the ASN.1 tag or length fields. A "routerPublicKey" member, whose value is is the Base64 encoding without trailing ‘=‘ (Section 5 of ) of the equivalent to a router certificate’s public key's subjectPublicKeyInfo value, as described in . This is the full ASN.1 DER encoding of the subjectPublicKeyInfo, including the ASN.1 tag and length values of the subjectPublicKeyInfo SEQUENCE. The following JSON structure represents an array of "bgpsecAssertions" with one element as described above:

", "publicKey": "", "comment": "My known key for my important ASN" } ] ]]> Note that a bgpsecAssertion matches the syntax of the Router Key PDU described in section 5.10 of . Relying Parties MUST add any bgpsecAssertion thus found to the set of Router PDUs, excluding duplicates, when using the RPKI-RTR protocol .

The following JSON structure represents an example of a SLURM file that uses all the elements described in the previous sections:

", "publicKey": "" } ] } } ]]>

To ensure local consistency, the effect of SLURM MUST be atomic. That is, the output of the RP MUST be either the same as if SLURM file were not used, or it MUST reflect the entire SLURM configuration. For an example of why this is required, consider the case of two local routes for the same prefix but different origin ASNs. Both routes are configured with Locally Added Assertions. If neither addition occurs, then both routes could be in the unknown state . If both additions occur then both routes would be in the valid state. However, if one addition occurs and the other does not, then one could be invalid while the other is valid.

An implementation MAY support the concurrent use of multiple SLURM files. In this case, the resulting inputs to Validation Output Filters and Locally Added Assertions are the respective unions of the inputs from each file. The envisioned typical use case for multiple files is when the files have distinct scopes. For instance, operators of two distinct networks may resort to one RP system to frame routing decisions. As such, they probably deliver SLURM files to this RP respectively. Before an RP configures SLURM files from different sources it MUST make sure there is no internal conflict among the INR assertions in these SLURM files. To do so, the RP SHOULD check the entries of SLURM file with regard to overlaps of the INR assertions and report errors to the sources that created these SLURM files in question. The RP gets multiple SLURM files as a set, and the whole set MUST be rejected in case of any overlaps among SLURM files. If a problem is detected with the INR assertions in these SLURM files, the RP MUST NOT use them, and SHOULD issue a warning as error report in the following cases: There may be conflicting changes to ROA Prefix Assertions if there exists an IP address X and distinct SLURM files Y, Z such that X is contained by any prefix in any <prefixAssertions> or <prefixFilters> in file Y and X is contained by any prefix in any <prefixAssertions> or <prefixFilters> in file Z. There may be conflicting changes to BGPsec Assertions if there exists an ASN X and distinct SLURM files Y, Z such that X is used in any <bgpsecAssertions> or <bgpsecFilters> in file Y and X is used in any <bgpsecAssertions> or <bgpsecFilters> in file Z.

None

The mechanisms described in this document provide a network operator with additional ways to control use of RPKI data while preserving autonomy in address space and ASN management. These mechanisms are applied only locally; they do not influence how other network operators interpret RPKI data. Nonetheless, care should be taken in how these mechanisms are employed. Note that it also is possible to use SLURM to (locally) manipulate assertions about non-private INRs, e.g., allocated address space that is globally routed. For example, a SLURM file may be used to override RPKI data that a network operator believes has been corrupted by an adverse action. Network operators who elect to use SLURM in this fashion should use extreme caution. The goal of the mechanisms described in this document is to enable an RP to create its own view of the RPKI, which is intrinsically a security function. An RP using a SLURM file is trusting the assertions made in that file. Errors in the SLURM file used by an RP can undermine the security offered by the RPKI, to that RP. It could declare as invalid ROAs that would otherwise be valid, and vice versa. As a result, an RP MUST carefully consider the security implications of the SLURM file being used, especially if the file is provided by a third party. Additionally, each RP using SLURM MUST ensure the authenticity and integrity of any SLURM file that it uses. Initially, the SLURM file may be pre-configured out of band, but if the RP updates its SLURM file over the network, it MUST verify the authenticity and integrity of the updated SLURM file. Yet the mechanism to update SLURM file to guarantee authenticity and integrity is out of the scope of this document.

The authors would like to thank Stephen Kent for his guidance and detailed reviews of this document. Thanks go to to Richard Hansen for his careful reviews, to Hui Zou and Chunlin An for their editorial assistance.