]> Zhongguancun Lab

Beijing China lingst@zgclab.edu.cn

Tsinghua University

Beijing China xuke@tsinghua.edu.cn

Tsinghua University

Beijing China qli01@tsinghua.edu.cn

Tsinghua University

Beijing China zhuotaoliu@tsinghua.edu.cn

Capital Normal University

Beijing China wangxiaoliang@cnu.edu.cn

Security SIDROPS RPKI, ROV, BGP, security This document defines a Cryptographic Message Syntax (CMS) protected content type for ROV Deployment Transparency (ROV_TAG) objects for use with the Resource Public Key Infrastructure (RPKI). An ROV_TAG is a digitally signed object through which an Autonomous System (AS) that has deployed Route Origin Validation (ROV) can declare its ROV deployment status. When validated, an ROV_TAG's eContent can be used by ASes to identify which ASes have deployed ROV, enabling path selection decisions when hijacked routes are detected (see Section 3).

Introduction Route Origin Validation (ROV) is a critical security mechanism for BGP routing that uses the Resource Public Key Infrastructure (RPKI) to verify the legitimacy of route announcements. However, ROV deployment is currently partial, with a significant portion of ASes not yet having deployed ROV. In partial ROV deployment scenarios, the main security concern is: When an AS has deployed ROV and performs ROV validation, it may detect a hijacked route announcement that was propagated by an upstream AS. This indicates that the upstream AS has not deployed ROV or is not properly performing ROV validation. If the AS continues using paths through that upstream AS, its traffic may be hijacked. However, the AS cannot determine which alternative paths go through upstream ASes that have deployed ROV, making it difficult to make informed path selection decisions to avoid the compromised upstream AS. This document defines a profile for ROV Deployment Transparency (ROV_TAG) objects that allows ASes to register their ROV deployment status in RPKI. This provides transparency about which ASes have deployed ROV. When an AS detects a hijacked route announcement from an upstream AS, it can use ROV_TAG information to identify alternative paths where the immediate upstream AS has deployed ROV, enabling it to avoid paths through upstream ASes that have propagated hijacked routes (see Section 3). This CMS protected content type definition conforms to the template for RPKI signed objects. This document defines the object identifier (OID), ASN.1 syntax, and validation steps for ROV_TAG objects.

Requirements Language 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.

Terminology This document uses the following terminology: Origin AS: The Autonomous System (AS) that originates a BGP route announcement. The Origin AS is defined as the last AS in the AS_PATH attribute of the BGP route announcement, as specified in . Non-origin AS: Any AS in the AS_PATH of a BGP route announcement that is not the Origin AS. In an AS_PATH containing multiple ASes, all ASes except the last one (the Origin AS) are non-origin ASes.

The ROV_TAG

The ROV_TAG Content Type The content-type for an ROV_TAG is defined as id-ct-ROVTAG, which has the numerical value of 1.2.840.113549.1.9.16.1.TBD. This OID MUST appear both within the eContentType in the encapContentInfo structure as well as the content-type signed attribute within the signerInfo structure (see ).

The ROV_TAG eContent The content of an ROV_TAG identifies the AS that has deployed ROV. The eContent of an ROV_TAG is an instance of ROVDeploymentAttestation, formally defined by the following ASN.1 module:

Note that this content appears as the eContent within the encapContentInfo as specified in .

version The version number of the ROVDeploymentAttestation that complies with this specification MUST be 0 and MUST be explicitly encoded.

asID The asID field contains the AS number of the Autonomous System that is declaring its ROV deployment status.

rovDeployed The rovDeployed field is a BOOLEAN that indicates whether the AS has deployed ROV. Since only ASes that have deployed ROV register ROV_TAG objects, this field MUST be set to TRUE. For ASes that provide transit services (i.e., ASes that forward traffic for other ASes) that have deployed ROV, it is RECOMMENDED that they register an ROV_TAG object with rovDeployed set to TRUE. Stub ASes (end networks, content providers, etc. that do not provide transit services) are NOT RECOMMENDED to register ROV_TAG objects, as they typically appear as Origin ASes in BGP route announcements.

ROV_TAG Validation To validate an ROV_TAG, a relying party MUST perform all the validation checks specified in as well as the following additional ROV_TAG-specific validation steps: The Autonomous System Identifier Delegation Extension MUST be present in the end-entity (EE) certificate contained within the ROV_TAG. The asID in the ROV_TAG eContent MUST match the ASId specified by the EE certificate's Autonomous System Identifier Delegation Extension. The Autonomous System Identifier Delegation Extension MUST contain exactly one "id" element (Section 3.2.3.6 of ) and MUST NOT contain any "inherit" elements (Section 3.2.3.3 of ) or "range" elements (Section 3.2.3.7 of ). The IP Address Delegation Extension MUST be absent. The rovDeployed field MUST be present and MUST be set to TRUE. Since only ASes that have deployed ROV register ROV_TAG objects, this field MUST always be TRUE. If any of the above checks fail, the ROV_TAG in its entirety MUST be considered invalid and an error SHOULD be logged.

Use Case: Secure Path Selection In partial ROV deployment scenarios, when an AS filters a hijacked route announcement received from an upstream AS through ROV validation, this indicates that the upstream AS has accepted and propagated the hijacked route. This may occur because the upstream AS has not deployed ROV or is not properly performing ROV validation. In this situation, the AS SHOULD avoid using paths through that upstream AS for traffic destined to the affected prefix. This use case describes a defensive mechanism that is triggered when an AS detects a security problem. Specifically: The AS performs ROV validation and detects a hijacked route announcement. The AS identifies that the hijacked route was propagated by an upstream AS (the immediate upstream AS). The AS recognizes that the current path it is using also goes through this same immediate upstream AS that propagated the hijacked route. At this point, if the AS continues using the current path through that upstream AS, the data plane traffic will go through the hijacked upstream AS, leading to the same hijacking. As a defensive measure, the AS can use ROV_TAG information obtained from its RPKI Relying Party (RP) to identify alternative paths from the BGP route announcements it has already received. An alternative path is one where the immediate upstream AS has deployed ROV (i.e., has registered an ROV_TAG object with rovDeployed set to TRUE). The AS checks the ROV deployment status of upstream ASes in the AS_PATH of received route announcements against the ROV_TAG information. If such alternative paths exist, the AS MAY prefer them over the path through the upstream AS that propagated the hijacked route. This approach is based on the following reasoning: If an upstream AS has deployed ROV, it will filter invalid route announcements and will not propagate hijacked routes. If an upstream AS has deployed ROV, it may also implement secure path selection (i.e., avoid paths through upstream ASes that have propagated hijacked route announcements when it detects such announcements). This creates a mechanism where ASes can prefer paths through upstream ASes that have deployed ROV. The logic is straightforward: if an AS detects that an upstream AS has propagated a hijacked route announcement (by filtering it through ROV validation), it SHOULD select an alternative secure path. Conversely, if no hijacked route announcements are detected from an upstream AS, that upstream AS is considered secure, and there is no need to select an alternative path. Therefore, if an alternative path exists where the immediate upstream AS has deployed ROV, that path is more likely to be secure from that point forward, reducing the risk that traffic will be hijacked. The decision to use alternative paths is a matter of local policy. An AS MAY: Continue using normal BGP path selection when no hijacked route announcements are detected. When an AS filters a hijacked route announcement received from an upstream AS, consider alternative paths (where the immediate upstream AS has deployed ROV) as a defensive measure to avoid the path through the upstream AS that propagated the hijacked route. This defensive measure is triggered only when a security problem is detected. Fall back to normal BGP path selection if no alternative paths with ROV-deployed upstream ASes are available. This addresses the security vulnerability problem by enabling ASes to avoid paths through upstream ASes that have propagated hijacked routes. Such paths are identified through ROV validation. When alternative secure paths are available, this reduces the risk of route hijacking even in partial ROV deployment scenarios. Note: This is a heuristic defensive mechanism and does not provide cryptographic security guarantees. The use of alternative paths is OPTIONAL and subject to local policy.

Operational Considerations This section discusses operational aspects of ROV_TAG deployment and usage.

Querying ROV_TAG Information ROV_TAG objects are stored in the RPKI repository alongside other RPKI objects (e.g., ROAs, ASPAs). Relying Parties (RPs) process ROV_TAG objects as part of their standard RPKI repository synchronization and validation procedures, as specified in . ASes obtain ROV_TAG information from their RPKI Relying Party (RP) (e.g., through RPKI-to-Router protocols such as or ). ASes can query this information efficiently to determine whether upstream ASes have deployed ROV. Real-time queries to the RPKI repository or RP are not required during BGP path selection.

Performance Considerations The number of ASes that provide transit services is relatively small compared to the total number of ASes, which means the total number of ROV_TAG objects is expected to be manageable. This results in minimal storage and query overhead compared to other RPKI objects such as ROAs. Query operations for ROV_TAG information can be performed efficiently using standard data structures (e.g., hash tables keyed by AS number), enabling fast lookups during BGP path selection.

Deployment Recommendations For ASes that provide transit services and have deployed ROV, it is RECOMMENDED that they register an ROV_TAG object with rovDeployed set to TRUE. This provides transparency about ROV deployment. It also enables downstream ASes to make informed path selection decisions when hijacked routes are detected. Stub ASes (end networks, content providers, etc.) are NOT RECOMMENDED to register ROV_TAG objects, as they typically appear as Origin ASes in BGP route announcements.

Implementation Considerations This section provides guidance for implementers of ROV_TAG support. ROV_TAG is a new RPKI object type. Existing RPKI RP implementations that do not support ROV_TAG will simply ignore ROV_TAG objects during repository synchronization, as per the RPKI validation rules specified in . This ensures backward compatibility: ROV_TAG objects do not interfere with existing RPKI operations, and ASes that have not deployed ROV_TAG support can continue to operate normally. RP implementations that support ROV_TAG SHOULD: Validate ROV_TAG objects according to the validation steps specified in Section 2.6. Make validated ROV_TAG information available to ASes (e.g., through RPKI-to-Router protocols such as or ). The number of ROV_TAG objects is expected to be relatively small compared to other RPKI objects such as ROAs. This is because only ASes that provide transit services are expected to register ROV_TAG objects. Implementers that choose to implement the secure path selection described in Section 3 SHOULD: Obtain ROV_TAG information from the RPKI Relying Party (RP) (e.g., through RPKI-to-Router protocols such as or ). Implement efficient ROV_TAG lookup mechanisms, such as hash tables keyed by AS number, to quickly determine whether upstream ASes in the AS_PATH have deployed ROV by querying the ROV_TAG information. Implement logic to detect when a hijacked route announcement is received from an upstream AS and identify alternative paths where the immediate upstream AS has deployed ROV. Provide configuration options to enable or disable secure path selection. This allows operators to make informed decisions based on their operational requirements and risk tolerance. Log secure path selection decisions (e.g., when alternative paths are selected) to facilitate troubleshooting and security auditing. Handle cases where ROV_TAG information is unavailable gracefully by falling back to normal BGP path selection.

Security Considerations The security considerations of , , and also apply to ROV_TAG objects. There is no assumption of confidentiality for the data in an ROV_TAG; it is anticipated that ROV_TAG objects will be stored in repositories that are accessible to all ISPs, and perhaps to all Internet users. The integrity of an ROV_TAG MUST be established through cryptographic signing and validation according to . A fundamental limitation of ROV_TAG is that the information is self-asserted: an AS may register an ROV_TAG with rovDeployed set to TRUE but not actually perform ROV validation. ROV_TAG does not provide cryptographic verification that ROV validation is actually being performed. A malicious AS could register an ROV_TAG to attract traffic when other ASes are looking for alternative paths. However, several factors mitigate this risk: The secure path selection mechanism is defensive in nature - it is triggered only when a security problem is detected (hijacked route), not used for general path selection. This reduces the opportunity for exploitation. Registering an ROV_TAG in RPKI creates a public record. ASes generally care about their reputation in the routing community, and false claims about ROV deployment could damage that reputation. While this does not provide cryptographic verification, it does provide some level of accountability. ASes could maintain local violation records (not in RPKI) to track when upstream ASes that have registered ROV_TAG propagate invalid route announcements. Such mechanisms are non-standardized and implementation-specific, but they demonstrate that ROV_TAG can enable accountability even without cryptographic verification of actual ROV deployment. These factors reduce the risk of exploitation, though they do not eliminate it entirely.

IANA Considerations This document will require IANA to assign values in several registries. The specific assignments will be determined during the IETF review process. The following registrations are anticipated: An OID for the RPKI-ROV-TAG-2026 ASN.1 module in the "SMI Security for S/MIME Module Identifier" registry. An OID for the ROV_TAG content type in the "SMI Security for S/MIME CMS Content Type" registry. An entry for ROV_TAG in the "RPKI Signed Object" registry.

In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This document discusses the Border Gateway Protocol (BGP), which is an inter-Autonomous System routing protocol. The primary function of a BGP speaking system is to exchange network reachability information with other BGP systems. This network reachability information includes information on the list of Autonomous Systems (ASes) that reachability information traverses. This information is sufficient for constructing a graph of AS connectivity for this reachability from which routing loops may be pruned, and, at the AS level, some policy decisions may be enforced. BGP-4 provides a set of mechanisms for supporting Classless Inter-Domain Routing (CIDR). These mechanisms include support for advertising a set of destinations as an IP prefix, and eliminating the concept of network "class" within BGP. BGP-4 also introduces mechanisms that allow aggregation of routes, including aggregation of AS paths. This document obsoletes RFC 1771. [STANDARDS-TRACK] RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document defines two X.509 v3 certificate extensions. The first binds a list of IP address blocks, or prefixes, to the subject of a certificate. The second binds a list of autonomous system identifiers to the subject of a certificate. These extensions may be used to convey the authorization of the subject to use the IP addresses and autonomous system identifiers contained in the extensions. [STANDARDS-TRACK] This document describes the Cryptographic Message Syntax (CMS). This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content. [STANDARDS-TRACK] This document defines a profile for the structure of the Resource Public Key Infrastructure (RPKI) distributed repository. Each individual repository publication point is a directory that contains files that correspond to X.509/PKIX Resource Certificates, Certificate Revocation Lists and signed objects. This profile defines the object (file) naming scheme, the contents of repository publication points (directories), and a suggested internal structure of a local repository cache that is intended to facilitate synchronization across a distributed collection of repository publication points and to facilitate certification path construction. [STANDARDS-TRACK] This document specifies the algorithms, algorithms' parameters, asymmetric key formats, asymmetric key size, and signature format for the Resource Public Key Infrastructure (RPKI) subscribers that generate digital signatures on certificates, Certificate Revocation Lists, and signed objects as well as for the relying parties (RPs) that verify these digital signatures. [STANDARDS-TRACK] This document defines a generic profile for signed objects used in the Resource Public Key Infrastructure (RPKI). These RPKI signed objects make use of Cryptographic Message Syntax (CMS) as a standard encapsulation format. [STANDARDS-TRACK] In order to verifiably validate the origin Autonomous Systems of BGP announcements, routers need a simple but reliable mechanism to receive Resource Public Key Infrastructure (RFC 6480) prefix origin data from a trusted cache. This document describes a protocol to deliver validated prefix origin data to routers. [STANDARDS-TRACK] To help reduce well-known threats against BGP including prefix mis- announcing and monkey-in-the-middle attacks, one of the security requirements is the ability to validate the origination Autonomous System (AS) of BGP routes. More specifically, one needs to validate that the AS number claiming to originate an address prefix (as derived from the AS_PATH attribute of the BGP route) is in fact authorized by the prefix holder to do so. This document describes a simple validation mechanism to partially satisfy this requirement. [STANDARDS-TRACK] In order to verifiably validate the origin Autonomous Systems and Autonomous System Paths of BGP announcements, routers need a simple but reliable mechanism to receive Resource Public Key Infrastructure (RFC 6480) prefix origin data and router keys from a trusted cache. This document describes a protocol to deliver them. This document describes version 1 of the RPKI-Router protocol. RFC 6810 describes version 0. This document updates RFC 6810. ITU-T ITU-T The Cryptographic Message Syntax (CMS) format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates some auxiliary ASN.1 modules to conform to the 2008 version of ASN.1; the 1988 ASN.1 modules remain the normative version. There are no bits- on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes.

Example ROV_TAG eContent Payload Below is an example of a DER-encoded ROV_TAG eContent with annotation following the '#' character. Example: Transit AS with ROV deployed $ echo 30080201000203000D050201FF | xxd -r -ps | openssl asn1parse \ -inform DER -dump -i 0:d=0 hl=2 l= 8 cons: SEQUENCE 2:d=1 hl=2 l= 1 prim: INTEGER :00 # version = 0 5:d=1 hl=2 l= 3 prim: INTEGER :0D05 # asID = 3333 10:d=1 hl=2 l= 1 prim: BOOLEAN :FF # rovDeployed = TRUE