RFC 8416

Simplified Local Internet Number Resource Management with the RPKI (SLURM)

📅 published August 2018, from ietf

RFC 8416: Simplified Local Internet Number Resource Management with the RPKI (SLURM) 🎀 Authors: D. Ma (ZDNS), D. Mandelberg (Unaffiliated), and T. Bruijnzeels (NLnet Labs) 💖 Category: Standards Track ✨ | Date: August 2018 📅 | ISSN: 2070-1721 Obsoletes or updates: the title block doesn't list anything it obsoletes or updates 🙈

Abstract 🌈

The Resource Public Key Infrastructure (RPKI) is a global authorization infrastructure, and it lets whoever holds Internet Number Resources (INRs) make verifiable statements about those resources 🔐. Network operators, like Internet Service Providers (ISPs), can use the RPKI to validate BGP route origin assertions 💅. ISPs can also use it to validate the path of a BGP route 🛣️. But ISPs might want a local view with their own exceptions to the RPKI data, in the form of local filters and additions 🧚. This document describes simple mechanisms that let INR holders build a local, customized view of the RPKI, overriding global RPKI repository data whenever they need to 👑.

Status of This Memo 📜

This is an Internet Standards Track document. ✨

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community, and it went through public review and got approved for publication by the Internet Engineering Steering Group (IESG) 🎉. For more on Internet Standards, check Section 2 of RFC 7841 📚.

You can find info about the current status of this document, any errata, and how to give feedback at https://www.rfc-editor.org/info/rfc8416 💌.

Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. 🦋

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as they stand on the date this document was published. Please actually read these, bestie, because they describe your rights and restrictions for this document 🙏. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as described in the Simplified BSD License ⚖️.

Table of Contents 🗂️

   1. Introduction ....................................................3
      1.1. Terminology ................................................4
   2. RP with SLURM ...................................................4
   3. SLURM Files and Mechanisms ......................................5
      3.1. Use of JSON ................................................5
      3.2. SLURM File Overview ........................................5
      3.3. Validation Output Filters ..................................6
           3.3.1. Validated ROA Prefix Filters ........................6
           3.3.2. BGPsec Assertion Filters ............................7
      3.4. Locally Added Assertions ...................................9
           3.4.1. ROA Prefix Assertions ...............................9
           3.4.2. BGPsec Assertions ..................................10
      3.5. Example of a SLURM File with Filters and Assertions .......11
   4. SLURM File Configuration .......................................13
      4.1. SLURM File Atomicity ......................................13
      4.2. Multiple SLURM Files ......................................13
   5. IANA Considerations ............................................14
   6. Security Considerations ........................................14
   7. References .....................................................14
      7.1. Normative References ......................................14
      7.2. Informative References ....................................16
   Acknowledgments ...................................................17
   Authors' Addresses ................................................17

1. Introduction 🌸

Okay so the RPKI is a global authorization infrastructure 🌐 that lets whoever holds Internet Number Resources (INRs) make verifiable statements about them. For example, if you hold a block of IP(v4 or v6) addresses, you can issue a Route Origin Authorization (ROA) [RFC6482] that authorizes an Autonomous System (AS) to originate routes for that block 🦋. ISPs can then use the RPKI to validate BGP routes 💅. (Origin validation is covered in [RFC6811], and path validation is covered in [RFC8205].)

But here's the tea ☕: an RPKI Relying Party (RP) may want to override some of the information from configured Trust Anchors (TAs) and the certificates it downloads from the RPKI repository system 🙈. For instance, [RFC6491] recommends creating ROAs that would invalidate public routes for reserved and unallocated address space, yet some ISPs might want to use BGP and the RPKI with private address space (see [RFC1918], [RFC4193], and [RFC6598]) or private AS numbers (see [RFC1930] and [RFC6996]) 🔒. Local use of private address space and/or AS numbers is consistent with the RFCs cited above, but the global RPKI can't verify that kind of use 🤷‍♀️. So this motivates mechanisms that let a network operator publish, at its discretion, an exception to the RPKI in the form of filters and additions, for its own use and for its customers 💜. An operator might also want a local override to protect routes from adverse actions [RFC8211] until those actions have been dealt with 🛡️. The mechanisms built for this are called "Simplified Local Internet Number Resource Management with the RPKI (SLURM)" ✨.

SLURM lets an operator create a local view of the global RPKI by generating sets of assertions 🧩. For origin validation [RFC6811], an assertion is a tuple of {IP prefix, prefix length, maximum length, Autonomous System Number (ASN)}, as used by the RPKI-Router protocol, version 0 [RFC6810] and version 1 [RFC8210]. For BGPsec [RFC8205], an assertion is a tuple of {ASN, subject key identifier, router public key}, as used by version 1 of the RPKI-Router protocol 🔐. (For the rest of this document, these assertions are called "ROA Prefix Assertions" and "BGPsec Assertions", respectively 🏷️.)

1.1. Terminology 📖

The BCP 14 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are interpreted as described in BCP 14 [RFC2119] [RFC8174], but only when, and only when, they appear in all capitals, as shown here 🧠.

2. RP with SLURM 💅

SLURM gives an RP a simple way to build a local, customized view of the RPKI, overriding RPKI repository data when needed 🎀. To do that, an RP with SLURM filters out (that is, 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 main output of an RP is the data it sends to routers over the RPKI-Router protocol [RFC8210] 🚀. That protocol lets routers ask an RP for all the assertions it knows about (a Reset Query) or just for an update of the changes in assertions (a Serial Query) 🔄. The mechanisms in this document get applied to the result set for a Reset Query, and to both the old and new sets that get compared for a Serial Query 🧃. RP software might modify other forms of output in comparable ways, but that's outside the scope of this document 🫶.

+--------------+   +---------------------------+   +------------+
|              |   |                           |   |            |
| Repositories +--->Local cache of RPKI objects+---> Validation |
|              |   |                           |   |            |
+--------------+   +---------------------------+   +-----+------+
                                                        |
      +-------------------------------------------------+
      |
+------v-------+   +------------+   +-----------+   +-------------+
|              |   |            |   |           |   |             |
|    SLURM     +--->   SLURM    +--->RPKI-Router+---> BGP Speakers|
|   Filters    |   | Assertions |   | Protocol  |   |             |
+--------------+   +------------+   +-----------+   +-------------+

Figure 1: SLURM's Position in the RP Stack 📊

3. SLURM Files and Mechanisms 🦋

3.1. Use of JSON 🧾

SLURM filters and assertions are written in JSON format [RFC8259] 💖. JSON members that aren't defined here MUST NOT be used in SLURM files 🙅. An RP MUST treat any deviation from the specifications as an error 💀. And if the specifications get extended later, the additions MUST use an incremented value for the slurmVersion member 🔢.

3.2. SLURM File Overview 🗺️

A SLURM file is one single JSON object, and it holds these members:

  • A slurmVersion member that MUST be set to 1, encoded as a number 🔢
  • A validationOutputFilters member (Section 3.3), whose value is an object. The object MUST contain exactly two members:
    • A prefixFilters member, whose value is described in Section 3.3.1 🧹
    • A bgpsecFilters member, whose value is described in Section 3.3.2 🧹
  • A locallyAddedAssertions member (Section 3.4), whose value is an object. The object MUST contain exactly two members:
    • A prefixAssertions member, whose value is described in Section 3.4.1 ✍️
    • A bgpsecAssertions member, whose value is described in Section 3.4.2 ✍️

In the envisioned typical use case, an RP uses both Validation Output Filters and Locally Added Assertions 🌟. In that case, the resulting assertions MUST be the same as if output filtering happened before the local assertions were added. Put another way, Locally Added Assertions MUST NOT be removed by output filtering 🛡️.

The following JSON structure represents a SLURM file with no filters or assertions 🫧:

{
  "slurmVersion": 1,
  "validationOutputFilters": {
    "prefixFilters": [],
    "bgpsecFilters": []
  },
  "locallyAddedAssertions": {
    "prefixAssertions": [],
    "bgpsecAssertions": []
  }
}

Figure 2: Empty SLURM File 🌷

3.3. Validation Output Filters 🌸

3.3.1. Validated ROA Prefix Filters 🎀

okay so the RP can set up zero or more Validated ROA Prefix Filters ("Prefix Filters" for short) 💖 Each one can hold an IPv4 or IPv6 prefix and/or an ASN. It is RECOMMENDED that every Prefix Filter gets an explanatory comment so the RP software can show it to users 🫶

All of this goes in the value of the prefixFilters member, which is an array of zero or more objects. Each object MUST contain either 1) one of the following members or 2) one of each of the following members ✨

  • A prefix member, whose value is a string representing either an IPv4 prefix (see Section 3.1 of [RFC4632]) or an IPv6 prefix (see [RFC5952]).
  • An asn member, whose value is a number.

In addition, each object MAY contain one optional comment member, whose value is a string 💅

Here's an example prefixFilters member with one object for each use case above 🧚

"prefixFilters": [
  {
    "prefix": "192.0.2.0/24",
    "comment": "All VRPs encompassed by prefix"
  },
  {
    "asn": 64496,
    "comment": "All VRPs matching ASN"
  },
  {
    "prefix": "198.51.100.0/24",
    "asn": 64497,
    "comment": "All VRPs encompassed by prefix, matching ASN"
  }
]

Figure 3: "prefixFilters" Examples

Any Validated ROA Payload (VRP) [RFC6811] that matches any configured Prefix Filter MUST be removed from the RP's output. Ate and left no crumbs 💀

A VRP counts as matching a Prefix Filter if one of these cases applies 👑

  1. If the Prefix Filter only contains an IPv4 or IPv6 prefix, the VRP is considered to match the filter if the VRP prefix is equal to or covered by the Prefix Filter prefix.
  2. If the Prefix Filter only contains an ASN, the VRP is considered to match the filter if the VRP ASN matches the Prefix Filter ASN.
  3. If the 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.

3.3.2. BGPsec Assertion Filters 🌸

The RP can configure zero or more BGPsec Assertion Filters ("BGPsec Filters" for short). Each BGPsec Filter can contain an ASN and/or the Base64 [RFC4648] encoding of a Router Subject Key Identifier (SKI), as described in [RFC8209] and [RFC6487]. It is RECOMMENDED that an explanatory comment is also included with each BGPsec Filter, so it can be shown to users of the RP software 🦋

All of this is the value of the bgpsecFilters member, 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 [RFC4648]) of the certificate's Subject Key Identifier as described in Section 4.8.2 of [RFC6487]. (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 ✨

Here's an example bgpsecFilters member with one object for each use case above 💜

"bgpsecFilters": [
  {
    "asn": 64496,
    "comment": "All keys for ASN"
  },
  {
    "SKI": "<Base 64 of some SKI>",
    "comment": "Key matching Router SKI"
  },
  {
    "asn": 64497,
    "SKI": "<Base 64 of some SKI>",
    "comment": "Key for ASN 64497 matching Router SKI"
  }
]

Figure 4: "bgpsecFilters" Examples

Any BGPsec Assertion that matches any configured BGPsec Filter MUST be removed from the RP's output. A BGPsec Assertion is considered to match a BGPsec Filter if one of these cases applies 🌈

  1. If the BGPsec Filter only contains an ASN, a BGPsec Assertion is considered to match if the Assertion ASN matches the Filter ASN.
  2. If the BGPsec Filter only contains an SKI, a BGPsec Assertion is considered to match if the Assertion Router SKI matches the Filter SKI.
  3. 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 SKI.

3.4. Locally Added Assertions 🧁

3.4.1. ROA Prefix Assertions 💖

Each RP is locally configured with a (possibly empty) array of ROA Prefix Assertions ("Prefix Assertions" for 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 it can be shown to users of the RP software 🎀

All of this is expressed as the value of the prefixAssertions member, an array of zero or more objects. Each object MUST contain one of each of the following members 👑

  • A prefix member, whose value is a string representing either an IPv4 prefix (see Section 3.1 of [RFC4632]) or an IPv6 prefix (see [RFC5952]).
  • 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.

Here's an example prefixAssertions member with one object for each use case above 🦋

"prefixAssertions": [
  {
    "asn": 64496,
    "prefix": "198.51.100.0/24",
    "comment": "My other important route"
  },
  {
    "asn": 64496,
    "prefix": "2001:DB8::/32",
    "maxPrefixLength": 48,
    "comment": "My other important de-aggregated routes"
  }
]

Figure 5: "prefixAssertions" Examples

Note that the combination of the prefix, ASN, and optional maximum length describes a VRP as described in [RFC6811]. 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 Protocol Data Units (PDUs), excluding duplicates when using the RPKI-Router protocol (see Sections 5.6 and 5.7 of [RFC8210]). This part is lowkey the most important bit 🔥

3.4.2. BGPsec Assertions 🌸

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 it can be shown to users of the RP software 💅

The above is expressed as the value of the bgpsecAssertions member, 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 certificate's Subject Key Identifier as described in Section 4.8.2 of [RFC6487] (This is the value of the ASN.1 OCTET STRING without the ASN.1 tag or length fields.)
  • A routerPublicKey member, whose value is the Base64 encoding without trailing '=' (Section 5 of [RFC4648]) of the equivalent to the subjectPublicKeyInfo value of the router certificate's public key, as described in [RFC8208]. This is the full ASN.1 DER encoding of the subjectPublicKeyInfo, including the ASN.1 tag and length values of the subjectPublicKeyInfo SEQUENCE.

Here's an example bgpsecAssertions member with one object 🧚

"bgpsecAssertions": [
  {
    "asn": 64496,
    "SKI": "<some base64 SKI>",
    "routerPublicKey": "<some base64 public key>",
    "comment": "My known key for my important ASN"
  }
]

Figure 6: "bgpsecAssertions" Examples

Note that a bgpsecAssertions member matches the syntax of the Router Key PDU described in Section 5.10 of [RFC8210]. Relying Parties MUST add any bgpsecAssertions member thus found to the set of Router Key PDUs, excluding duplicates, when using the RPKI-Router protocol [RFC8210]. 🌈

3.5. Example of a SLURM File with Filters and Assertions ✨

The following JSON structure is an example of a SLURM file that uses all the elements from the previous sections 🎀

{
  "slurmVersion": 1,
  "validationOutputFilters": {
    "prefixFilters": [
      {
        "prefix": "192.0.2.0/24",
        "comment": "All VRPs encompassed by prefix"
      },
      {
        "asn": 64496,
        "comment": "All VRPs matching ASN"
      },
      {
        "prefix": "198.51.100.0/24",
        "asn": 64497,
        "comment": "All VRPs encompassed by prefix, matching ASN"
      }
    ],
    "bgpsecFilters": [
      {
        "asn": 64496,
        "comment": "All keys for ASN"
      },
      {
        "SKI": "Zm9v",
        "comment": "Key matching Router SKI"
      },
      {
        "asn": 64497,
        "SKI": "YmFy",
        "comment": "Key for ASN 64497 matching Router SKI"
      }
    ]
  },
  "locallyAddedAssertions": {
    "prefixAssertions": [
      {

        "asn": 64496,
        "prefix": "198.51.100.0/24",
        "comment": "My other important route"
      },
      {
        "asn": 64496,
        "prefix": "2001:DB8::/32",
        "maxPrefixLength": 48,
        "comment": "My other important de-aggregated routes"
      }
    ],
    "bgpsecAssertions": [
      {
        "asn": 64496,
        "comment" : "My known key for my important ASN",
        "SKI": "<some base64 SKI>",
        "routerPublicKey": "<some base64 public key>"
      }
    ]
  }
}

Figure 7: Example of Full SLURM File

4. SLURM File Configuration 🦋

4.1. SLURM File Atomicity 💜

To keep things locally consistent, the effect of SLURM MUST be atomic 🫶 That means the output of the RP either MUST be the same as if a SLURM file were not used, or MUST reflect the entire SLURM configuration. Here's why this matters 👀 Imagine two local routes for the same prefix but with different origin ASNs, and both are set up with Locally Added Assertions. If neither addition happens, both routes could be in the NotFound state [RFC6811]. If both additions happen, both routes would be in the Valid state. But if only one addition happens, one route could be Invalid while the other is Valid 😭 that's a whole mess, bestie 💀

4.2. Multiple SLURM Files ✨

okay bestie, so an implementation MAY support using multiple SLURM files at the same time 🦋 When it does, the inputs to Validation Output Filters and Locally Added Assertions are the unions of the inputs from each file. 💖

The envisioned typical use case is when the files have distinct scopes. Like, operators of two different networks might share one RP system to frame their routing decisions, so they end up delivering SLURM files to that RP independently 🌸

Before an RP configures SLURM files from different sources, it MUST make sure there is no internal conflict among the INR assertions in those files. 🔥 To do that, the RP SHOULD check the entries of each SLURM file for overlaps of the INR assertions and report errors to the sources that created the files in question. The RP gets multiple SLURM files as a set, and the whole set MUST be rejected if there are any overlaps among the SLURM files. No cap, that's strict but it keeps things clean 💅

If a problem is detected with the INR assertions in these SLURM files, the RP MUST NOT use them, and it SHOULD issue a warning as error report in the following cases:

  1. There may be conflicting changes to ROA Prefix Assertions if an IP address X and distinct SLURM files Y and Z exist 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. 🙈
  2. There may be conflicting changes to BGPsec Assertions if an ASN X and distinct SLURM files Y and Z exist 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. 🧚

5. IANA Considerations 🌈

This document has no IANA actions. Nothing to register this time, bestie 💜

6. Security Considerations 🔥

okay, this section is seriously important, so pay attention 😭 The mechanisms in this document give a network operator extra ways to control how RPKI data gets used, while still keeping their autonomy over address space and ASN management. These mechanisms are only applied 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's also 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. 💀 This is giving "handle with care" energy, periodt.

The goal of the mechanisms in this document is to let an RP 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, so errors in the SLURM file can undermine the security the RPKI offers to that RP. A SLURM file could declare as invalid ROAs that would otherwise be valid, and vice versa. 😵 So an RP MUST carefully consider the security implications of the SLURM file being used, especially if the file is provided by a third party. Not me trusting a random file without checking 🙅‍♀️

Also, each RP using SLURM MUST ensure the authenticity and integrity of any SLURM file that it uses. The SLURM file may be preconfigured out of band at first, but if the RP updates its SLURM file over the network, it MUST verify the authenticity and integrity of the updated SLURM file. The mechanism to update the SLURM file in a way that guarantees authenticity and integrity is out of the scope of this document. ✨ That's a different story for another day, bestie.

7. References

7.1. Normative References 📚

7.2. Informative References 🦋

Acknowledgments 💜

Huge shoutout to the authors 🫶 They want to thank Stephen Kent for his guidance and detailed reviews of this document. They also thank Richard Hansen for his careful reviews, and Hui Zou and Chunlin An for their editorial assistance. Everyone who makes these docs better deserves a crown 👑

Authors' Addresses 🎀

Di Ma
ZDNS
4 South 4th St. Zhongguancun
Haidian, Beijing  100190
China

Email: madi@zdns.cn


David Mandelberg
Unaffiliated

Email: david@mandelberg.org
URI:   https://david.mandelberg.org


Tim Bruijnzeels
NLnet Labs
Science Park 400
Amsterdam  1098 XH
The Netherlands

Email: tim@nlnetlabs.nl

That's the whole thing, bestie! Slay 🌈✨💅

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