--- 1/draft-ietf-dtn-bpsec-03.txt 2017-03-12 12:13:23.027127415 -0700 +++ 2/draft-ietf-dtn-bpsec-04.txt 2017-03-12 12:13:23.095129025 -0700 @@ -1,18 +1,18 @@ Delay-Tolerant Networking E. Birrane Internet-Draft K. McKeever Intended status: Standards Track JHU/APL -Expires: May 3, 2017 October 30, 2016 +Expires: September 13, 2017 March 12, 2017 Bundle Protocol Security Specification - draft-ietf-dtn-bpsec-03 + draft-ietf-dtn-bpsec-04 Abstract This document defines a security protocol providing end to end data integrity and confidentiality services for the Bundle Protocol. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. @@ -20,714 +20,752 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on May 3, 2017. + This Internet-Draft will expire on September 13, 2017. Copyright Notice - Copyright (c) 2016 IETF Trust and the persons identified as the + Copyright (c) 2017 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to 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 are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Supported Security Services . . . . . . . . . . . . . . . 3 1.3. Specification Scope . . . . . . . . . . . . . . . . . . . 4 1.4. Related Documents . . . . . . . . . . . . . . . . . . . . 5 1.5. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 - 2. Key Properties . . . . . . . . . . . . . . . . . . . . . . . 7 - 2.1. Block-Level Granularity . . . . . . . . . . . . . . . . . 7 + 2. Key Properties . . . . . . . . . . . . . . . . . . . . . . . 6 + 2.1. Block-Level Granularity . . . . . . . . . . . . . . . . . 6 2.2. Multiple Security Sources . . . . . . . . . . . . . . . . 7 - 2.3. Mixed Security Policy . . . . . . . . . . . . . . . . . . 8 - 2.4. User-Selected Ciphersuites . . . . . . . . . . . . . . . 8 - 2.5. Deterministic Processing . . . . . . . . . . . . . . . . 9 - 3. Security Block Definitions . . . . . . . . . . . . . . . . . 9 - 3.1. Block Identification . . . . . . . . . . . . . . . . . . 10 - 3.2. Block Representation . . . . . . . . . . . . . . . . . . 10 - 3.3. Block Integrity Block . . . . . . . . . . . . . . . . . . 13 - 3.4. Block Confidentiality Block . . . . . . . . . . . . . . . 14 - 3.5. Block Interactions . . . . . . . . . . . . . . . . . . . 16 - 3.6. Parameters and Result Fields . . . . . . . . . . . . . . 17 - 3.7. BSP Block Example . . . . . . . . . . . . . . . . . . . . 18 - 4. Canonical Forms . . . . . . . . . . . . . . . . . . . . . . . 20 - 4.1. Technical Notes . . . . . . . . . . . . . . . . . . . . . 20 - 4.2. Primary Block Canonicalization . . . . . . . . . . . . . 21 - 4.3. Non-Primary-Block Canonicalization . . . . . . . . . . . 22 - 5. Security Processing . . . . . . . . . . . . . . . . . . . . . 22 - 5.1. Bundles Received from Other Nodes . . . . . . . . . . . . 23 - 5.1.1. Receiving BCB Blocks . . . . . . . . . . . . . . . . 23 - 5.1.2. Receiving BIB Blocks . . . . . . . . . . . . . . . . 23 - 5.2. Bundle Fragmentation and Reassembly . . . . . . . . . . . 24 - 6. Key Management . . . . . . . . . . . . . . . . . . . . . . . 25 - 7. Policy Considerations . . . . . . . . . . . . . . . . . . . . 25 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 26 - 8.1. Attacker Capabilities and Objectives . . . . . . . . . . 27 - 8.2. Attacker Behaviors and BPSec Mitigations . . . . . . . . 28 - 8.2.1. Eavesdropping Attacks . . . . . . . . . . . . . . . . 28 - 8.2.2. Modification Attacks . . . . . . . . . . . . . . . . 28 - 8.2.3. Topology Attacks . . . . . . . . . . . . . . . . . . 29 - 8.2.4. Message Injection . . . . . . . . . . . . . . . . . . 30 - 9. Ciphersuite Authorship Considerations . . . . . . . . . . . . 30 - 10. Defining Other Security Blocks . . . . . . . . . . . . . . . 31 - 11. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 32 - 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 - 12.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 32 - 12.2. Cipher Suite Flags . . . . . . . . . . . . . . . . . . . 32 - 12.3. Parameters and Results . . . . . . . . . . . . . . . . . 33 + 2.3. Mixed Security Policy . . . . . . . . . . . . . . . . . . 7 + 2.4. User-Selected Cipher Suites . . . . . . . . . . . . . . . 8 + 2.5. Deterministic Processing . . . . . . . . . . . . . . . . 8 + 3. Security Blocks . . . . . . . . . . . . . . . . . . . . . . . 8 + 3.1. Block Definitions . . . . . . . . . . . . . . . . . . . . 9 + 3.2. Uniqueness . . . . . . . . . . . . . . . . . . . . . . . 9 + 3.3. Target Multiplicity . . . . . . . . . . . . . . . . . . . 10 + 3.4. Target Identification . . . . . . . . . . . . . . . . . . 10 + 3.5. Block Representation . . . . . . . . . . . . . . . . . . 11 + 3.6. Abstract Security Block . . . . . . . . . . . . . . . . . 11 + 3.7. Block Integrity Block . . . . . . . . . . . . . . . . . . 14 + 3.8. Block Confidentiality Block . . . . . . . . . . . . . . . 15 + 3.9. Block Interactions . . . . . . . . . . . . . . . . . . . 16 + 3.10. Parameters and Result Types . . . . . . . . . . . . . . . 17 + 3.11. BSP Block Example . . . . . . . . . . . . . . . . . . . . 20 + 4. Canonical Forms . . . . . . . . . . . . . . . . . . . . . . . 22 + 4.1. Technical Notes . . . . . . . . . . . . . . . . . . . . . 22 + 4.2. Primary Block Canonicalization . . . . . . . . . . . . . 23 + 4.3. Non-Primary-Block Canonicalization . . . . . . . . . . . 23 + 5. Security Processing . . . . . . . . . . . . . . . . . . . . . 24 + 5.1. Bundles Received from Other Nodes . . . . . . . . . . . . 24 + 5.1.1. Receiving BCB Blocks . . . . . . . . . . . . . . . . 24 + 5.1.2. Receiving BIB Blocks . . . . . . . . . . . . . . . . 25 + 5.2. Bundle Fragmentation and Reassembly . . . . . . . . . . . 26 + 6. Key Management . . . . . . . . . . . . . . . . . . . . . . . 26 + 7. Security Policy Considerations . . . . . . . . . . . . . . . 26 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . 27 + 8.1. Attacker Capabilities and Objectives . . . . . . . . . . 28 + 8.2. Attacker Behaviors and BPSec Mitigations . . . . . . . . 29 + 8.2.1. Eavesdropping Attacks . . . . . . . . . . . . . . . . 29 + 8.2.2. Modification Attacks . . . . . . . . . . . . . . . . 29 + 8.2.3. Topology Attacks . . . . . . . . . . . . . . . . . . 31 + 8.2.4. Message Injection . . . . . . . . . . . . . . . . . . 31 + 9. Cipher Suite Authorship Considerations . . . . . . . . . . . 32 + 10. Defining Other Security Blocks . . . . . . . . . . . . . . . 33 + 11. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 34 + 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34 + 12.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 34 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 13.1. Normative References . . . . . . . . . . . . . . . . . . 34 - 13.2. Informative References . . . . . . . . . . . . . . . . . 34 + 13.2. Informative References . . . . . . . . . . . . . . . . . 35 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 35 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35 1. Introduction - This document defines security features for the Bundle Protocol - [BPBIS] intended for use in delay-tolerant networks, in order to - provide Delay-Tolerant Networking (DTN) security services. + This document defines security features for the Bundle Protocol (BP) + [BPBIS]. This BP Security Specification (BPSec) is intended for use + in Delay Tolerant Networks (DTNs) to provide end-to-end security + services. 1.1. Motivation - The Bundle Protocol is used in DTNs that overlay multiple networks, - some of which may be challenged by limitations such as intermittent - and possibly unpredictable loss of connectivity, long or variable - delay, asymmetric data rates, and high error rates. The purpose of - the Bundle Protocol is to support interoperability across such - stressed networks. + The Bundle Protocol specification [BPBIS] defines DTN as referring to + "a networking architecture providing communications in and/or through + highly stressed environments" where "BP may be viewed as sitting at + the application layer of some number of constituent networks, forming + a store-carry-forward overlay network". The term "stressed" + environment refers to multiple challenging conditions including + intermittent connectivity, large and/or variable delays, asymmetric + data rates, and high bit error rates. - The stressed environment of the underlying networks over which the - Bundle Protocol operates makes it important for the DTN to be - protected from unauthorized use, and this stressed environment poses - unique challenges for the mechanisms needed to secure the Bundle - Protocol. Furthermore, DTNs may be deployed in environments where a - portion of the network might become compromised, posing the usual - security challenges related to confidentiality and integrity. + There is a reasonable expectation that BP may be deployed in such a + way that a portion of the network might become compromised, posing + the usual security challenges related to confidentiality and + integrity. However, the stressed nature of the BP operating + environment imposes unique requirements such that the usual security + mechanisms to usual security challenges may not apply. For example, + the store-carry-forward nature of the network may require protecting + data at rest while also preventing unauthorized consumption of + critical resources such as storage space. The heterogeneous nature + of the networks comprising the BP overlay, and/or associated timing, + might prevent the establishment of an end-to-end session to provide a + context for a security service. The partitionability of a DTN might + prevent regular contact with a centralized security oracle (such as a + certificate authority). + + An end-to-end security service is needed that operates in all of the + environments where the BP operates. 1.2. Supported Security Services - This specification supports end-to-end integrity and confidentiality - services associated with BP bundles. + BPSec provides end-to-end integrity and confidentiality services for + BP bundles. Integrity services ensure data within a bundle are not changed. Data changes may be caused by processing errors, environmental conditions, or intentional manipulation. An integrity service is one that provides sufficient confidence to a data receiver that data has not changed since its value was last asserted. - Confidentiality services ensure that the values of some data within a - bundle can only be determined by authorized receivers of the data. - When a bundle traverses a DTN, many nodes in the network other than - the destination node MAY see the contents of a bundle. A - confidentiality service allows a destination node to generate data - values from otherwise encrypted contents of a bundle. + Confidentiality services ensure that only authorized receivers can + view those data within a bundle identified as needing to be private + amongst the data source and data receivers. A confidentiality + services is one that provides confidence to a data receiver that + private data was not viewed by other nodes as the bundle traversed + the DTN. NOTE: Hop-by-hop authentication is NOT a supported security service in this specification, for three reasons. 1. The term "hop-by-hop" is ambiguous in a BP overlay, as nodes that are adjacent in the overlay may not be adjacent in physical connectivity. This condition is difficult or impossible to predict in the overlay and therefore makes the concept of hop-by- hop authentication difficult or impossible to enforce at the overlay. 2. Networks in which BPSec may be deployed may have a mixture of security-aware and not-security-aware nodes. Hop-by-hop authentication cannot be deployed in a network if adjacent nodes in the network have different security capabilities. 3. Hop-by-hop authentication can be viewed as a special case of data - integrity. As such, it is possible to develop policy that - provides a version of authentication using the integrity - mechanisms defined in this specification. + integrity. As such, a version of authentication can be achieved + by using the integrity mechanisms defined in this specification. 1.3. Specification Scope - This document describes the Bundle Protocol Security Specification - (BPSec), which provides security services for blocks within a bundle. - This includes the data specification for individual BP extension - blocks and the processing instructions for those blocks. + This document defines the security services provided by the BPSec. + This includes the data specification for representing these services + as BP extension blocks, and the rules for adding, removing, and + processing these blocks at various points in the bundle's traversal + of the DTN. - BPSec applies, by definition, only to those nodes that implement it, - known as "security-aware" nodes. There MAY be other nodes in the DTN - that do not implement BPSec. All nodes can interoperate with the - exception that BPSec security operations can only happen at BPSec - security-aware nodes. + BPSec applies only to those nodes that implement it, known as + "security-aware" nodes. There might be other nodes in the DTN that + do not implement BPSec. While all nodes in a BP overlay can exchange + bundles, BPSec security operations can only happen at BPSec security- + aware nodes. This specification does not address individual cipher suite - implementations. The definition and enumeration of cipher suites - should be undertaken in separate specification documents. + implementations. Different networking conditions and operational + considerations require varying strengths of security mechanism such + that mandating a cipher suite in this specification may result in too + much security for some networks and too little security in others. + The definition and enumeration of cipher suites is assumed to be + undertaken in other, separate specification documents. This specification does not address the implementation of security - policy and does not provide a security policy for the BPSec. - Security policies are typically based on the nature and capabilities - of individual networks and network operational concepts. However, - this specification does recommend policy considerations when building - a security policy. + policy and does not provide a security policy for the BPSec. Similar + to cipher suites, security policies are based on the nature and + capabilities of individual networks and network operational concepts. + This specification does provide policy considerations when building a + security policy. This specification does not address how to combine the BPSec security blocks with other protocols, other BP extension blocks, or other best practices to achieve security in any particular network implementation. 1.4. Related Documents This document is best read and understood within the context of the following other DTN documents: "Delay-Tolerant Networking Architecture" [RFC4838] defines the - architecture for delay-tolerant networks, but does not discuss - security at any length. + architecture for DTNs and identifies certain security assumptions + made by existing Internet protocols that are not valid in a DTN. - The DTN Bundle Protocol [BPBIS] defines the format and processing of - the blocks used to implement the Bundle Protocol, excluding the - security-specific blocks defined here. + The Bundle Protocol [BPBIS] defines the format and processing of the + bundles that both carry the data and the security services operating + on those data. This document also defines the extension block format + used to capture BPSec security blocks. - The Bundle Security Protocol [RFC6257] and Streamlind Bundle Security - Protocol [SBSP] introduce the concepts of security blocks for - security services. BPSec is based off of these documents. + The Bundle Security Protocol [RFC6257] and Streamlined Bundle + Security Protocol [SBSP] documents introduced the concepts of BP + security blocks for security services in a DTN. The BPSec is a + continuation and refinement of these documents. 1.5. Terminology 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 [RFC2119]. - This section defines those terms whose definition is important to the - understanding of concepts within this specification. - - o Source - the bundle node from which a bundle originates. - - o Destination - the bundle node to which a bundle is ultimately - destined. + This section defines terminology either unique to the BPSec or + otherwise necessary for understanding the concepts defined in this + specification. - o Forwarder - the bundle node that forwarded the bundle on its most - recent hop. + o Forwarder - any node that transmits a bundle in the DTN. The Node + ID of the Bundle Protocol Agent (BPA) that sent the bundle on its + most recent hop. - o Intermediate Receiver, Waypoint, or "Next Hop" - the neighboring - bundle node to which a forwarder forwards a bundle. + o Intermediate Receiver, Waypoint, or "Next Hop" - any node that + receives a bundle from a Forwarder that is not the Destination. + The Node ID of the BPA at any such node. o Path - the ordered sequence of nodes through which a bundle passes - on its way from source to destination. The path is not - necessarily known by the bundle, or any bundle-aware nodes. - - The application of these terms applied to a sample network topology - is shown in Figure 1. This figure shows four bundle nodes (BN1, BN2, - BN3, BN4) residing above some transport layer(s). Three distinct - transport and network protocols (T1/N1, T2/N2, and T3/N3) are also - shown. - - +---------v-| +->>>>>>>>>>v-+ +->>>>>>>>>>v-+ +-^---------+ - | BN1 v | | ^ BN2 v | | ^ BN3 v | | ^ BN4 | - +---------v-+ +-^---------v-+ +-^---------v-+ +-^---------+ - | T1 v | + ^ T1/T2 v | + ^ T2/T3 v | | ^ T3 | - +---------v-+ +-^---------v-+ +-^---------v + +-^---------+ - | N1 v | | ^ N1/N2 v | | ^ N2/N3 v | | ^ N3 | - +---------v-+ +-^---------v + +-^---------v-+ +-^---------+ - | >>>>>>>>^ >>>>>>>>>>^ >>>>>>>>^ | - +-----------+ +------------+ +-------------+ +-----------+ - | | | | - |<-- An Internet --->| |<--- An Internet --->| - | | | | - - Figure 1: Bundle Nodes Sitting Above the Transport Layer. - - Consider the case where BN1 originates a bundle that it forwards to - BN2. BN2 forwards the bundle to BN3, and BN3 forwards the bundle to - BN4. BN1 is the source of the bundle and BN4 is the destination of - the bundle. BN1 is the first forwarder, and BN2 is the first - intermediate receiver; BN2 then becomes the forwarder, and BN3 the - intermediate receiver; BN3 then becomes the last forwarder, and BN4 - the last intermediate receiver, as well as the destination. + on its way from Source to Destination. The path is not + necessarily known in advance by the bundle or any BPAs in the DTN. - If node BN2 originates a bundle (for example, a bundle status report - or a custodial signal), which is then forwarded on to BN3, and then - to BN4, then BN2 is the source of the bundle (as well as being the - first forwarder of the bundle) and BN4 is the destination of the - bundle (as well as being the final intermediate receiver). + o Security Block - a BPSec extension block in a bundle. - The following security-specific terminology is also defined to - clarify security operations in this specifiation. + o Security Operation - the application of a security service to a + security target, notated as OP(security service, security target). + For example, OP(confidentiality, payload). Every security + operation in a bundle MUST be unique, meaning that a security + service can only be applied to a security target once in a bundle. + A security operation is implemented by a security block. o Security Service - the security features supported by this specification: integrity and confidentiality. o Security Source - a bundle node that adds a security block to a bundle. o Security Target - the block within a bundle that receives a security-service as part of a security-operation. - o Security Block - a BPSec extension block in a bundle. - - o Security Operation - the application of a security service to a - security target, notated as OP(security service, security target). - For example, OP(confidentiality, payload). Every security - operation in a bundle MUST be unique, meaning that a security - service can only be applied to a security target once in a bundle. - A security operation is implemented by a security block. + o Source - the node which originates a bundle. The Node ID of the + BPA originating the bundle. 2. Key Properties The application of security services in a DTN is a complex endeavor that must consider physical properties of the network, policies at - each node, and various application security requirements. Rather - than enumerate all potential security implementations in all - potential DTN topologies, this specification defines a set of key - properties of a security system. The security primitives outlined in - this document MUST enable the realization of these properties in a - DTN deploying the Bundle Protocol. + each node, and various application security requirements. This + section identifies and defines the key properties guiding design + decisions for the security services provided by this specification. 2.1. Block-Level Granularity + Security services within this specification MUST allow different + blocks within a bundle to have different security services applied to + them. As such, each security block within a bundle MUST be + associated with a specific security operation. + Blocks within a bundle represent different types of information. The primary block contains identification and routing information. The payload block carries application data. Extension blocks carry a variety of data that may augment or annotate the payload, or otherwise provide information necessary for the proper processing of a bundle along a path. Therefore, applying a single level and type of security across an entire bundle fails to recognize that blocks in a bundle may represent different types of information with different security needs. - Security services within this specification MUST provide block level - granularity where applicable such that different blocks within a - bundle may have different security services applied to them. - - For example, within a bundle, a payload might be encrypted to protect - its contents, whereas an extension block containing summary - information related to the payload might be integrity signed but - otherwise unencrypted to provide certain nodes access to payload- - related data without providing access to the payload. - - Each security block in a bundle will be associated with a specific - security operation. + For example, a payload block might be encrypted to protect its + contents and an extension block containing summary information + related to the payload might be integrity signed but unencrypted to + provide waypoints access to payload-related data without providing + access to the payload. 2.2. Multiple Security Sources A bundle MAY have multiple security blocks and these blocks MAY have different security sources. The Bundle Protocol allows extension blocks to be added to a bundle - at any time during its existence in the DTN. When a waypoint node - adds a new extension block to a bundle, that extension block may have + at any time during its existence in the DTN. When a waypoint adds a + new extension block to a bundle, that extension block may have security services applied to it by that waypoint. Similarly, a - waypoint node may add a security service to an existing extension - block, consistent with its security policy. For example, a node + waypoint may add a security service to an existing extension block, + consistent with its security policy. For example, a node representing a boundary between a trusted part of the network and an untrusted part of the network may wish to apply payload encryption for bundles leaving the trusted portion of the network. - In each case, a node other than the bundle originator may add a - security service to the bundle and, as such, the source for the - security service will be different than the source of the bundle - itself. Security services MUST track their orginating node so as to - properly apply policy and key selection associated with processing - the security service at the bundle destination. - - Referring to Figure 1, if the bundle that originates at BN1 is given - security blocks by BN1, then BN1 is the security source for those - blocks as well as being the source of the bundle. If the bundle that - originates at BN1 is then given a security block by BN2, then BN2 is - the security source for that block even though BN1 remains the bundle - source. + When a waypoint adds a security service to the bundle, the waypoint + is the security source for that service. The security block(s) which + represent that service in the bundle may need to record this security + source as the bundle destination might need this information for + processing. For example, a destination node might interpret policy + as it related to security blocks as a function of the security source + for that block. 2.3. Mixed Security Policy - Different nodes in a DTN may have different security related - capabilities. Some nodes may not be security aware and will not - understand any security related extension blocks. Other nodes may - have security policies that require evaluation of security services - at places other than the bundle destination (such as verifying - integrity signatures at certain waypoint nodes). Other nodes may - ignore any security processing if they are not the destination of the - bundle. The security services described in this specification must - allow each of these scenarios. + The security policy enforced by nodes in the DTN MAY differ. - Extension blocks representing security services MUST have their block + Some waypoints may not be security aware and will not be able to + process security blocks. Therefore, security blocks MUST have their processing flags set such that the block will be treated - appropriately by non-security-aware nodes. + appropriately by non-security-aware waypoints + Some waypoints will have security policies that require evaluating + security services even if they are not the bundle destination or the + final intended destination of the service. For example, a waypoint + may choose to verify an integrity service even though the waypoint is + not the bundle destination and the integrity service will be needed + by other node along the bundle's path. - Extension blocks providing integrity services within a bundle MUST - support options to allow waypoint nodes to evaluate these signatures - if such nodes have the proper configuraton to do so. + Some waypoints will determine, through policy, that they are the + intended recipient of the security service and terminate the security + service in the bundle. For example, a gateway node may determine + that, even though it is not the destination of the bundle, it should + verify and remove a particular integrity service or attempt to + decrypt a confidentiality service, before forwarding the bundle along + its path. -2.4. User-Selected Ciphersuites + Some waypoints may understand security blocks but refuse to process + them unless they are the bundle destination. + +2.4. User-Selected Cipher Suites The security services defined in this specification rely on a variety - of cipher suites providing integrity signatures, ciphertext, and - other information necessary to populate security blocks. Users may - wish to select different cipher suites to implement different - security services. For example, some users may wish to use a SHA-256 - based hash for integrity whereas other users may require a SHA-384 - hash instead. The security services defined in this specification - MUST provide a mechanism for identifying what cipher suite has been - used to populate a security block. + of cipher suites providing integrity signatures, cipher-text, and + other information necessary to populate security blocks. Users MAY + select different cipher suites to implement security services. For + example, some users might prefer a SHA-256 based hash for integrity + whereas other users may prefer a SHA-384 hash instead. The security + services defined in this specification MUST provide a mechanism for + identifying what cipher suite has been used to populate a security + block. 2.5. Deterministic Processing - In all cases, the processing order of security services within a - bundle must avoid ambiguity when evaluating security at the bundle - destination. This specification MUST provide determinism in the - application and evaluation of security services, even when doing so - results in a loss of flexibility. + Whenever a node determines that it must process more than one + security block in a received bundle (either because the policy at a + waypoint states that it should process security blocks or because the + node is the bundle destination) the order in which security blocks + are processed MUST be deterministic. All nodes MUST impose this same + deterministic processing order for all security blocks. This + specification provides determinism in the application and evaluation + of security services, even when doing so results in a loss of + flexibility. -3. Security Block Definitions +3. Security Blocks +3.1. Block Definitions - There are two types of security blocks that may be included in a - bundle. These are the Block Integrity Block (BIB) and the Block - Confidentiality Block (BCB). + This specification defines two types of security block: the Block + Integrity Block (BIB) and the Block Confidentiality Block (BCB). The BIB is used to ensure the integrity of its security target(s). - The integrity information in the BIB MAY (when possible) be - verified by any node in between the BIB security source and the - bundle destination. BIBs MAY be added to, and removed from, - bundles as a matter of security policy. + The integrity information in the BIB MAY be verified by any node + in between the BIB security source and the bundle destination. + Security-aware waypoints may add or remove BIBs from bundles in + accordance with their security policy. The BCB indicates that the security target(s) has been encrypted, in whole or in part, at the BCB security source in order to protect its content while in transit. The BCB may be decrypted by - appropriate nodes in the network, up to and including the bundle - destination, as a matter of security policy. + security-aware nodes in the network, up to and including the + bundle destination, as a matter of security policy. - A security operation MUST NOT be applied more than once in a bundle. - For example, the two security operations: OP(integrity, payload) and - OP(integrity, payload) are considered redundant and MUST NOT appear - together in a bundle. However, the two security operations - OP(integrity, payload) and OP(integrity, extension_block_1) MAY both - be present in the bundle. Also, the two security operations - OP(integrity, extension_block_1) and OP(integrity, extension_block_2) - are unique and may both appear in the same bundle. +3.2. Uniqueness - If the same security service is to be applied to multiple security - targets, and cipher suite parameters for each security service are - identical, then the set of security operations can be represented as - a single security block with multiple security targets. In such a - case, all security operations represented in the security block MUST - be applied/evaluated together. + Security operations in a bundle MUST be unique - the same security + service MUST NOT be applied to a security target more than once in a + bundle. Since a security operation is represented as a security + block, this limits what security blocks may be added to a bundle: if + adding a security block to a bundle would cause some other security + block to no longer represent a unique security operation then the new + block MUST NOT be added. -3.1. Block Identification + If multiple security blocks representing the same security operation + were allowed in a bundle at the same time, there would exist + ambiguity regarding block processing order and the property of + deterministic processing blocks would be lost. - This specification requires that every target block of a security - operation be uniquely identifiable. The definition of the extension - block header from [BPBIS] provides such a mechanism in the "Block - Number" field, which provides a unique identifier for a block within - a bundle. Within this specification, a security target will be - identified by its unique Block Number. + Using the notation OP(service,target), several examples illustrate + this uniqueness requirement. - A security block MAY apply to multiple security targets if and only - if all cipher suite parameters, security source, and key information - are common for the security operation. In such a case, the security - block MUST contain security results for each covered security target. - The use of multiple security targets in a security block provides an - efficiency mechanism so that identical ciphersuite information does - not need to be repeated across multiple security blocks. + o Signing the payload twice: The two operations OP(integrity, + payload) and OP(integrity, payload) are redundant and cannot both + be present in the same bundle at the same time. -3.2. Block Representation + o Signing different blocks: The two operations OP(integrity, + payload) and OP(integrity, extension_block_1) are not redundant + and both may be present in the same bundle at the same time. + Similarly, the two operations OP(integrity, extension_block_1) and + OP(integrity,extension_block_2) are also not redundant and may + both be present in the bundle at the same time. + + o Different Services on same block: The two operations + OP(integrity,payload) and OP(confidentiality, payload) are not + inherently redundant and may both be present in the bundle at the + same time, pursuant to other processing rules in this + specification. + +3.3. Target Multiplicity + + Under special circumstances, a single security block can represent + multiple security operations as a way of reducing the overall number + of security blocks present in a bundle. In these circumstances, + reducing the number of security blocks in the bundle reduces the + amount of redundant information in the bundle. + + A set of security operations may be represented by a single security + block if and only if the following conditions are true. + + o The security operations apply the same security service. For + example, they are all integrity operations or all confidentiality + operations. + + o The cipher suite parameters and key information for the security + operations are identical. + + o The security source for the security operations is the same. + Meaning the set of operations are being added/removed by the same + node. + + o No security operations have the same security target, as that + would violate the need for security operations to be unique. + + o None of the security operations conflict with security operations + already present in the bundle. + + When representing multiple security operations in a single security + block, the information that is common across all operations is + represented once in the security block, and the information which is + different (e.g., the security targets) are represented individually. + When the security block is processed all security operations + represented by the security block MUST be applied/evaluated at that + time. + +3.4. Target Identification + + A security target is a block in the bundle to which a security + service applies. This target MUST be uniquely and unambiguously + identifiable when processing a security block. The definition of the + extension block header from [BPBIS] provides a "Block Number" field + for exactly this purpose. Therefore, a security target in a security + block MUST be represented as the Block Number of the target block. + +3.5. Block Representation Each security block uses the Canonical Bundle Block Format as defined in [BPBIS]. That is, each security block is comprised of the following elements: o Block Type Code o Block Number o Block Processing Control Flags - o CRC Type and CRC Field + o CRC Type and CRC Field (if present) o Block Data Length o Block Type Specific Data Fields - The structure of the BIB and BCB Block Type Specific Data fields are - identifcal and illustrated in Figure 2. In this figure, field names - prefaced with an '*' are optional and their inclusion in the block is - indicated by the Cipher Suite Flags field. - - +================================================= - | Field Name | Field Data Type | - +================================================= - | # Security Targets | Unsigned Integer | - +---------------------+--------------------------+ - | Security Targets | Array (Unsigned Integer) | - +---------------------+--------------------------+ - | Cipher Suite ID | Unsigned Integer | - +---------------------+--------------------------+ - | Cipher Suite Flags | Unsigned Integer | - +---------------------+--------------------------+ - | Security Source | URI - OPTIONAL | - +---------------------+--------------------------+ - | Cipher Parameters | Byte Array - OPTIONAL | - +---------------------+--------------------------+ - | Security Result | Byte Array | - +---------------------+--------------------------+ - - Figure 2: BIB and BCB Block Structure - - Where the block fields are identified as follows. - - o # Security Targets - The number of security targets for this - security block. This value MUST be at least 1. - - o Security Targets - This array contains the unique identifier of - the blocks targetted by this security operation. Each security - target MUST represent a block present in the bundle. A security - target MUST NOT be repeated in this array. - - o Cipher suite ID - Identifies the cipher suite used to implement - the security service represented by this block and applied to each - security target. - - o Cipher suite flags - Identifies which optional security block - fields are present in the block. The structure of the Cipher - Suite Flags field is shown in Figure 3. The presence of an - optional field is indicated by setting the value of the - corresponding flag to one. A value of zero indicates the - corresponding optional field is not present. The BPSEC Cipher - Suite Flags are defined as follows. + Security-specific information for a security block is captured in the + "Block Type Specific Data Fields". - Bit Bit Bit Bit Bit Bit Bit Bit - 7 6 5 4 3 2 1 0 - +-----------------------------------+-----+-----+ - | reserved | src |parm | - +-----------------------------------+-----+-----+ - MSB LSB +3.6. Abstract Security Block - Figure 3: Cipher Suite Flags + The structure of the security-specific portions of a security block + is identical for both the BIB and BCB Block Types. Therefore, this + section defines an Abstract Security Block (ASB) data structure and + discusses the definition, processing, and other constraints for using + this structure. An ASB is never directly instantiated within a + bundle, it is only a mechanism for discussing the common aspects of + BIB and BCB security blocks. - Where: + The fields of the ASB SHALL be as follows, listed in the order in + which they MUST appear. - * bits 7-2 are reserved for future use. + Security Targets: + This field identifiers the block or blocks that are the target + of the security operation(s) represented by this security + block. Each security target is identified as the Block Number + of the target block. This field SHALL be represented by a CBOR + array of data items. Each target within this CBOR array SHALL + be represented by a CBOR unsigned integer. This array MUST + have at least 1 item. - * src - bit 1 indicates whether the Security Source is present in - the block. + Cipher Suite Id: + This field identifies the cipher suite used to implement the + security service represented by this block and applied to each + security target. This field SHALL be represented by a CBOR + unsigned integer. - * parm - bit 0 indicates whether or not the Cipher Suite - Parameters field is present in the block. + Cipher Suite Flags: + This field identifiers which optional fields are present in the + security block. This field SHALL be represented as a CBOR + unsigned integer containing a bit field of 5 bits indicating + the presence or absence of other security block fields, as + follows. - o (OPTIONAL) Security Source (URI) - This identifies the node that - inserted the security service in the bundle. If the security - source is not present then the source MAY be inferred from the - bundle source, the previous hop, or some other node as defined by - security policy. + Bit 1 (the most-significant bit, 0x10): reserved. - o (OPTIONAL) Parameters (Byte Array) - Compound field of the - following two items. + Bit 2 (0x08): reserved. - * Length (Unsigned Integer) - specifies the length of the next - field, which captures the parameters data. + Bit 3 (0x04): reserved. - * Data (Byte Array) - A byte array encoding one or more cipher - suite parameters, with each parameter represented as a Type- - Length-Value (TLV) triplet, defined as follows. + Bit 4 (0x02): Security Source Present Flag. - + Type (Byte) - The parameter type. + Bit 5 (the least-significant bit, 0x01): Cipher Suite + Parameters Present Flag. - + Length (Unsigned Integer) - The length of the parameter. + In this field, a value of 1 indicates that the associated + security block field MUST be included in the security block. A + value of 0 indicates that the associated security block field + MUST NOT be in the security block. - + Value (Byte Array) - The parameter value. + Security Source (Optional Field): + This field identifies the Endpoint that inserted the security + block in the bundle. If the security source field is not + present then the source MAY be inferred from other information, + such as the bundle source or the previous hop, as defined by + security policy. This field SHALL be represented by a CBOR + array in accordance with [BPBIS] rules for representing + Endpoint Identifiers (EIDs). - See Section 3.6 for a list of parameter types that MUST be - supported by BPSEC implementations. BPSEC cipher suite - specifications MAY define their own parameters to be - represented in this byte array. + Cipher Suite Parameters (Optional Field): + This field captures one or more cipher suite parameters that + should be provided to security-aware nodes when processing the + security service described by this security block. This field + SHALL be represented by a CBOR array. Each entry in this array + is a single cipher suite parameter. A single cipher suite + parameter SHALL also be represented as a CBOR array comprising + a 2-tuple of the type and value of the parameter, as follows. - o Security Result (Byte Array) - A security result is the output of - an appropriate cipher suite specific calculation (e.g., a - signature, Message Authentication Code (MAC), or cipher-text block - key). There MUST exist one security result for each security - target in the security block. A security result is a multi-field - component, described as follows. + * Parameter Type. This field identifiers which cipher suite + parameter is being specified. This field SHALL be + represented as a CBOR unsigned integer. Potential parameter + types are described in Section 3.10. Other specifications + MAY define additional parameter types for use in this field. - * Total Length (Unsigned Integer) - specifies the length, in - bytes, of the remaining security result information. + * Parameter Value. This field captures the value associated + with this parameter. This field SHALL be represented by the + applicable CBOR representation of the parameter type. These + specifications are given in Section 3.10 for parameter types + defined in this specification. Other specifications that + define other parameter types MUST include the appropriate + CBOR encoding of the parameter value. - * Results (Byte Array) - This field captures each of the security - results, catenated together, one for each security target - covered by the security block. Each result is captured by the - four-tuple of (Target, Type, Len, Value). The meaning of each - is given below. + Therefore, this field SHALL be represented as a CBOR array of + CBOR arrays. - + Target (Optional) (Unsigned Integer) - If the security block - has multiple security targets, the target field is the Block - Number of the security target to which this result field - applies. If the security block only has a single security - target, this field is omitted. + Security Results: + This field captures the results of applying a security service + to the security targets in this security block. This field + SHALL be represented as a CBOR array. Each entry in this array + represents a "target list" of security results for a specific + security target. There MUST be one "target list" for each + entry in the Security Targets field and target lists in the + Security Results field MUST be in the same order as the + Security Targets field (e.g., the first "target list" MUST hold + results for the first entry in the Security Targets field, and + so on). - + Type (Unsigned Integer) - The type of security result field. + A "target list" is also represented as a CBOR array of + individual security results for that target. An individual + security result is also represented as a CBOR array comprising + the 2-tuple of the result type and result value, defined as + follows. - + Length (Unsigned Integer) - The length of the result field. + * Result Type. This field captures the type of security + result. Some security result types capture the primary + output of a cipher suite. Other security results contain + additional annotative information from the cipher suite + processing. This field SHALL be represented as a CBOR + unsigned integer. Potential result types are described in + Section 3.10. Other specifications MAY define additional + result types for use in this field. - + Value (Byte Array) - The results of the cipher suite - specific calculation. + * Result Value. This field captures the value associated with + this result for this target. This field SHALL be + represented by the applicable CBOR representation of the + result type. These specifications are given in Section 3.10 + for result types defined in this specification. Other + specifications that define other result types MUST include + the appropriate CBOR encoding of the result value. -3.3. Block Integrity Block +3.7. Block Integrity Block - A BIB is an ASB with the following characteristics: + A BIB is a bundle extension block with the following characteristics. - The Block Type Code value MUST be 0x02. + o The Block Type Code value is as specified in Section 12.1. - The Block Processing Control flags value can be set to whatever - values are required by local policy. Cipher suite designers - should carefully consider the effect of setting flags that either - discard the block or delete the bundle in the event that this - block cannot be processed. + o The Block Type Specific Data Fields follow the structure of the + ASB. - A security target for a BIB MUST NOT reference a security block - defined in this specification (e.g., a BIB or a BCB). + o A security target listed in the Security Targets field MUST NOT + reference a security block defined in this specification (e.g., a + BIB or a BCB). - The cipher suite ID MUST be documented as an end-to-end + o The Cipher Suite Id MUST be documented as an end-to-end authentication-cipher suite or as an end-to-end error-detection- cipher suite. - An EID-reference to the security source MAY be present. If this + o An EID-reference to the security source MAY be present. If this field is not present, then the security source of the block SHOULD be inferred according to security policy and MAY default to the bundle source. The security source may also be specified as part - of key information described in Section 3.6. - - The security result captures the result of applying the cipher - suite calculation (e.g., the MAC or signature) to the relevant - parts of the security target, as specified in the cipher suite - definition. This field MUST be present. + of key information described in Section 3.10. - The cipher suite MAY process less than the entire security target. + o The cipher suite MAY process less than the entire security target. If the cipher suite processes less than the complete, original security target, the cipher suite parameters MUST specify which bytes of the security target are protected. Notes: + o It is RECOMMENDED that cipher suite designers carefully consider + the effect of setting flags that either discard the block or + delete the bundle in the event that this block cannot be + processed. + o Since OP(integrity, target) is allowed only once in a bundle per target, it is RECOMMENDED that users wishing to support multiple integrity signatures for the same target define a multi-signature cipher suite. o For some cipher suites, (e.g., those using asymmetric keying to produce signatures or those using symmetric keying with a group key), the security information MAY be checked at any hop on the way to the destination that has access to the required keying - information, in accordance with Section 3.5. + information, in accordance with Section 3.9. o The use of a generally available key is RECOMMENDED if custodial transfer is employed and all nodes SHOULD verify the bundle before accepting custody. -3.4. Block Confidentiality Block +3.8. Block Confidentiality Block - A BCB is an ASB with the following characteristics: + A BCB is a bundle extension block with the following characteristics. - The Block Type Code value MUST be 0x03. + The Block Type Code value is as specified in Section 12.1. The Block Processing Control flags value can be set to whatever values are required by local policy, except that this block MUST have the "replicate in every fragment" flag set if the target of the BCB is the Payload Block. Having that BCB in each fragment indicates to a receiving node that the payload portion of each - fragment represents cipher-text. Cipher suite designers should - carefully consider the effect of setting flags that either discard - the block or delete the bundle in the event that this block cannot - be processed. + fragment represents cipher-text. - A security target for a BCB MAY reference the payload block, a - non-security extension block, or a BIB block. A security target - in a BCB MUST NOT be another BCB. + The Block Type Specific Data Fields follow the structure of the + ASB. - The cipher suite ID MUST be documented as a confidentiality cipher + A security target listed in the Security Targets field MAY + reference the payload block, a non-security extension block, or a + BIB block. A BCB MUST NOT include another BCB as a security + target. A BCB MUST NOT target the primary block. + + The Cipher Suite Id MUST be documented as a confidentiality cipher suite. - Any additional bytes generated as a result of encryption and/or - authentication processing of the security target SHOULD be placed - in an "integrity check value" field (see Section 3.6) or other - such appropriate area in the security result of the BCB. + Any additional bytes generated from applying the cipher suite to a + security target (such as additional authenticated text) MAY be + placed in an appropriate security result (e.g., an Integrity Check + Value) in accordance with cipher suite and security policy. An EID-reference to the security source MAY be present. If this field is not present, then the security source of the block SHOULD be inferred according to security policy and MAY default to the bundle source. The security source may also be specified as part - of key information described in Section 3.6. - - The security result MUST be present in the BCB. This compound - field normally contains fields such as an encrypted bundle - encryption key and/or authentication tag. + of key information described in Section 3.10. - The BCB modifies the contents of its security target. When a BCB is - applied, the security target body data are encrypted "in-place". - Following encryption, the security target body data contains cipher- - text, not plain-text. Other security target block fields (such as - type, processing control flags, and length) remain unmodified. + The BCB modifies the contents of its security target(s). When a BCB + is applied, the security target body data are encrypted "in-place". + Following encryption, the security target Block Type Specific Data + Fields contains cipher-text, not plain-text. Other block fields + remain unmodified, with the exception of the Block Data Length field, + which may be changed if the BCB is allowed to change the length of + the block (see below). Fragmentation, reassembly, and custody transfer are adversely - affected by a change in size of the payload due to ambiguity about - what byte range of the block is actually in any particular fragment. - Therefore, when the security target of a BCB is the bundle payload, - the BCB MUST NOT alter the size of the payload block body data. - Cipher suites SHOULD place any block expansion, such as - authentication tags (integrity check values) and any padding - generated by a block-mode cipher, into an integrity check value item - in the security result field (see Section 3.6) of the BCB. This "in- - place" encryption allows fragmentation, reassembly, and custody - transfer to operate without knowledge of whether or not encryption - has occurred. + affected by a change in size of the payload block due to ambiguity + about what byte range of the block is actually in any particular + fragment. Therefore, when the security target of a BCB is the bundle + payload, the BCB MUST NOT alter the size of the payload block body + data. This "in-place" encryption allows fragmentation, reassembly, + and custody transfer to operate without knowledge of whether or not + encryption has occurred. + + If a BCB cannot alter the size of the security target (e.g., the + security target is the payload block or block length modifications + are disallowed by policy) then differences in the size of the cipher- + text and plain-text MUST be handled in the following way. If the + cipher-text is shorter in length than the plain-text, padding must be + used in accordance with the cipher suite policy. If the cipher-text + is larger than the plain-text, overflow bytes MUST be placed in + overflow parameters in the Security Result field. Notes: + o It is RECOMMENDED that cipher suite designers carefully consider + the effect of setting flags that either discard the block or + delete the bundle in the event that this block cannot be + processed. + o The cipher suite MAY process less than the entire original security target body data. If the cipher suite processes less than the complete, original security target body data, the BCB for that security target MUST specify, as part of the cipher suite parameters, which bytes of the body data are protected. - o The BCB's "discard" flag may be set independently from its - security target's "discard" flag. Whether or not the BCB's - "discard" flag is set is an implementation/policy decision for the - encrypting node. (The "discard" flag is more properly called the - "Discard if block cannot be processed" flag.) + o The BCB block processing control flags MAY be set independently + from the processing control flags of the security target(s). The + setting of such flags SHOULD be an implementation/policy decision + for the encrypting node. o A BCB MAY include information as part of additional authenticated - data to address parts of the target block, such as EID references, - that are not converted to cipher-text. + data to address parts of the target block that are not converted + to cipher-text. -3.5. Block Interactions +3.9. Block Interactions The security block types defined in this specification are designed to be as independent as possible. However, there are some cases where security blocks may share a security target creating processing dependencies. If confidentiality is being applied to a target that already has integrity applied to it, then an undesirable condition occurs where a - security aware intermediate node would be unable to check the - integrity result of a block because the block contents have been - encrypted after the integrity signature was generated. To address - this concern, the following processing rules MUST be followed. + security aware waypoint would be unable to check the integrity result + of a block because the block contents have been encrypted after the + integrity signature was generated. To address this concern, the + following processing rules MUST be followed. o If confidentiality is to be applied to a target, it MUST also be applied to any integrity operation already defined for that target. This means that if a BCB is added to encrypt a block, another BCB MUST also be added to encrypt a BIB also targeting that block. o An integrity operation MUST NOT be applied to a security target if a BCB in the bundle shares the same security target. This prevents ambiguity in the order of evaluation when receiving a BIB @@ -736,284 +774,271 @@ o An integrity value MUST NOT be evaluated if the BIB providing the integrity value is the security target of an existing BCB block in the bundle. In such a case, the BIB data contains cipher-text as it has been encrypted. o An integrity value MUST NOT be evaluated if the security target of the BIB is also the security target of a BCB in the bundle. In such a case, the security target data contains cipher-text as it has been encrypted. - o As mentioned in Section 3.3, a BIB MUST NOT have a BCB as its + o As mentioned in Section 3.7, a BIB MUST NOT have a BCB as its security target. BCBs may embed integrity results as part of - cipher suite parameters. + security results. These restrictions on block interactions impose a necessary ordering when applying security operations within a bundle. Specifically, for a given security target, BIBs MUST be added before BCBs. This ordering MUST be preserved in cases where the current BPA is adding all of the security blocks for the bundle or whether the BPA is a waypoint adding new security blocks to a bundle that already contains security blocks. -3.6. Parameters and Result Fields +3.10. Parameters and Result Types - Various cipher suites include several items in the cipher suite - parameters and/or security result fields. Which items MAY appear is - defined by the particular cipher suite description. A cipher suite - MAY support several instances of the same type within a single block. + Cipher suite parameters and security results may capture multiple + types of information in a security block. This section identifies a + set of parameters and results that are available in any BPSec + implementation for use by any cipher suite. Individual cipher suites + MAY define additional parameters and results. A cipher suite MAY + include multiple instances of the same type of parameter or result in + a security block. - Each item is represented as a type-length-value. Type is a single - byte indicating the item. Length is the count of data bytes to - follow, and is an Unsigned Integer. Value is the data content of the - item. + Parameters and results are represented using CBOR, and any + identification of a new parameter or result type MUST include how the + value of the type will be represented using the CBOR specification. + Types themselves are always represented as a CBOR unsigned integer. - Item types, name, and descriptions are defined as follows. + Cipher suite parameter types, as defined by this specification, are + as follows. - Cipher suite parameters and result fields. + Cipher Suite Parameter Types. - +-------+----------------+-----------------------------+------------+ - | Type | Name | Description | Field | - +-------+----------------+-----------------------------+------------+ - | 0 | Reserved | | | - +-------+----------------+-----------------------------+------------+ - | 1 | Initialization | A random value, typically | Cipher | - | | Vector (IV) | eight to sixteen bytes. | Suite | - | | | | Parameters | - +-------+----------------+-----------------------------+------------+ - | 2 | Reserved | | | - +-------+----------------+-----------------------------+------------+ - | 3 | Key | Material encoded or | Cipher | - | | Information | protected by the key | Suite | - | | | management system and used | Parameters | - | | | to transport an ephemeral | | - | | | key protected by a long- | | - | | | term key. | | - +-------+----------------+-----------------------------+------------+ - | 4 | Content Range | Pair of Unsigned Integers | Cipher | - | | | (offset,length) specifying | Suite | - | | | the range of payload bytes | Parameters | - | | | to which an operation | | - | | | applies. The offset MUST be | | - | | | the offset within the | | + +------+----------------+--------------------------+----------------+ + | Type | Name | Description | CBOR | + | | | | Representation | + +------+----------------+--------------------------+----------------+ + | 0 | Initialization | A random value, | Byte String | + | | Vector | typically eight to | | + | | | sixteen bytes. | | + +------+----------------+--------------------------+----------------+ + | 1 | Key | Material encoded or | Byte String | + | | Information | protected by the key | | + | | | management system and | | + | | | used to transport an | | + | | | ephemeral key protected | | + | | | by a long-term key. | | + +------+----------------+--------------------------+----------------+ + | 2 | Content Range | Pair of Unsigned | CBOR Array | + | | | Integers (offset,length) | comprising a | + | | | specifying the range of | 2-tuple of | + | | | payload bytes to which | CBOR unsigned | + | | | an operation applies. | integers. | + | | | The offset MUST be the | | + | | | offset within the | | | | | original bundle, even if | | | | | the current bundle is a | | | | | fragment. | | - +-------+----------------+-----------------------------+------------+ - | 5 | Integrity | Result of BIB digest or | Security | - | | Signatures | other signing operation. | Results | - +-------+----------------+-----------------------------+------------+ - | 6 | Unassigned | | | - +-------+----------------+-----------------------------+------------+ - | 7 | Salt | An IV-like value used by | Cipher | - | | | certain confidentiality | Suite | - | | | suites. | Parameters | - +-------+----------------+-----------------------------+------------+ - | 8 | BCB Integrity | Output from certain | Security | - | | Check Value | confidentiality cipher | Results | - | | (ICV) / | suite operations to be used | | - | | Authentication | at the destination to | | - | | Tag | verify that the protected | | - | | | data has not been modified. | | - | | | This value MAY contain | | - | | | padding if required by the | | - | | | cipher suite. | | - +-------+----------------+-----------------------------+------------+ - | 9-255 | Reserved | | | - +-------+----------------+-----------------------------+------------+ + +------+----------------+--------------------------+----------------+ + | 3 | Salt | An IV-like value used by | Byte Array | + | | | certain confidentiality | | + | | | suites. | | + +------+----------------+--------------------------+----------------+ + | 4-31 | Reserved | Reserve for future BPSec | | + | | | protocol expansion | | + +------+----------------+--------------------------+----------------+ + | >= | Unassigned | Unassigned by this | | + | 32 | | specification. Can be | | + | | | assigned by cipher suite | | + | | | specifications. | | + +------+----------------+--------------------------+----------------+ Table 1 -3.7. BSP Block Example + Security result parameter types, as defined by this specification, + are as follows. + + Security Result Types. + + +------+----------------+--------------------------+----------------+ + | Type | Name | Description | CBOR | + | | | | Representation | + +------+----------------+--------------------------+----------------+ + | 0 | Integrity | Result of BIB digest or | Byte String | + | | Signatures | other signing operation. | | + +------+----------------+--------------------------+----------------+ + | 1 | BCB Integrity | Output from certain | Byte String | + | | Check Value | confidentiality cipher | | + | | (ICV) / | suite operations to be | | + | | Authentication | used at the destination | | + | | Tag | to verify that the | | + | | | protected data has not | | + | | | been modified. This | | + | | | value MAY contain | | + | | | padding if required by | | + | | | the cipher suite. | | + +------+----------------+--------------------------+----------------+ + | 2-31 | Reserved | Reserve for future BPSec | | + | | | protocol expansion | | + +------+----------------+--------------------------+----------------+ + | >= | Unassigned | Unassigned by this | | + | 32 | | specification. Can be | | + | | | assigned by cipher suite | | + | | | specifications. | | + +------+----------------+--------------------------+----------------+ + + Table 2 + +3.11. BSP Block Example An example of BPSec blocks applied to a bundle is illustrated in - Figure 4. In this figure the first column represents blocks within a - bundle and the second column represents a unique identifier for each - block, suitable for use as the security target of a BPSec security - block. Since the mechanism and format of a security target is not - specified in this document, the terminology B1...Bn is used to - identify blocks in the bundle for the purposes of illustration. + Figure 1. In this figure the first column represents blocks within a + bundle and the second column represents the Block Number for the + block, using the terminology B1...Bn for the purpose of illustration. Block in Bundle ID +===================================+====+ | Primary Block | B1 | +-----------------------------------+----+ | BIB | B2 | | OP(integrity, target=B1) | | +-----------------------------------+----+ | BCB | B3 | | OP(confidentiality, target=B4) | | +-----------------------------------+----+ | Extension Block | B4 | +-----------------------------------+----+ | BIB | B5 | | OP(integrity, target=B6) | | +-----------------------------------+----+ | Extension Block | B6 | +-----------------------------------+----+ | BCB | B7 | - | OP(confidentiality,target=B8,B9) | | + | OP(confidentiality,targets=B8,B9) | | +-----------------------------------+----+ | BIB (encrypted by B7) | B8 | | OP(integrity, target=B9) | | +-----------------------------------+----| | Payload Block | B9 | +-----------------------------------+----+ - Figure 4: Sample Use of BSP Blocks + Figure 1: Sample Use of BPSec Blocks In this example a bundle has four non-security-related blocks: the - primary block (B1), three extension blocks (B4,B6), and a payload - block (B9). The following security applications are applied to this + primary block (B1), two extension blocks (B4,B6), and a payload block + (B9). The following security applications are applied to this bundle. o An integrity signature applied to the canonicalized primary block. This is accomplished by a single BIB (B2). o Confidentiality for the first extension block (B4). This is accomplished by a BCB block (B3). o Integrity for the second extension block (B6). This is accomplished by a BIB block (B5). NOTE: If the extension block B6 contains a representation of the serialized bundle (such as a hash over all blocks in the bundle at the time of its last transmission) then the BIB block is also providing an - authentication service from the prior BPSEC-BPA to this BPSEC-BPA. + authentication service. o An integrity signature on the payload (B10). This is accomplished by a BIB block (B8). o Confidentiality for the payload block and it's integrity signature. This is accomplished by a BCB block, B7, encrypting B8 - and B9. + and B9. In this case, the security source, key parameters, and + service are identical, so a single security block MAY be used for + this purpose, rather than requiring two BCBs one to encrypt B8 and + one to encrypt B9. 4. Canonical Forms By definition, an integrity service determines whether any aspect of a block was changed from the moment the security service was applied - at the security source until the point of current evaluation. To + at the security source until the point of evaluation. To successfully verify the integrity of a block, the data passed to the verifying cipher suite MUST be the same bits, in the same order, as those passed to the signature-generating cipher suite at the security source. - However, [BPBIS] does not specify a single on-the-wire encoding of - bundles. In cases where a security source generates a different - encoding than that used at a receiving node, care MUST be taken to - ensure that the inputs to cipher suites at the receiving node is a - bitwise match to inputs provided at the security source. - This section provides guidance on how to create a canonical form for each type of block in a bundle. This form MUST be used when generating inputs to cipher suites for use by BPSec blocks. - This specification does not define any security operation over the - entire bundle and, therefore, provides no canonical form for a - serialized bundle. - 4.1. Technical Notes The following technical considerations hold for all canonicalizations in this section. o Any numeric fields defined as variable-length MUST be expanded to - their "unpacked" form. For example, a 32-bit integer value MUST - be unpacked to a four-byte representation. - - o Each block encoding MUST follow the CBOR encodings provided in - [BPBISCBOR]. + their largest unpacked form before being used by a cipher suite. + If a field does not specify a maximum size, a maximum size of 32 + bits for integer and 64 bits for floating point values SHALL be + assumed. o Canonical forms are not transmitted, they are used to generate - input to a cipher suite for secuity processing at a security-aware - node. + input to a cipher suite for security processing at a security- + aware node. o Reserved flags MUST NOT be included in any canonicalization as it - is not known if those flags will chaneg in transit. + is not known if those flags will change in transit. - o These canonicalization algorithms assume that endpoint IDs - themselves are immutable and they are unsuitable for use in - environments where that assumption might be violated. + o These canonicalization algorithms assume that Endpoint IDs do not + change from the time at which a security source adds a security + block to a bundle and the time at which a node processes that + security block. o Cipher suites MAY define their own canonicalization algorithms and require the use of those algorithms over the ones provided in this specification. In the event of conflicting canonicalization algorithms, cipher suite algorithms take precedence over this specification. 4.2. Primary Block Canonicalization - The primary block canonical form is the same as the CBOR encoding of - the block, with certain modifications to account for allowed block - changes as the bundle traverses the DTN. The fields that compromise - the primary block, and any special considerations for their - representation in a canonical form, are as follows. - - o The Version field is included, without modification. + The canonicalization of the primary block is as specified in [BPBIS] + with the following exceptions. - o The Bundle Processing Flags field is used, with modification. - Certain bundle processing flags MAY change as a bundle transits - the DTN without indicating an integrity error. These flags, which - are identified below, MUST NOT be represented in the canonicalized - form of the bundle processing flags and, instead, be represented - by the bit 0. + o The following Bundle Processing Control Flags MAY change as a + bundle transits the DTN without indicating an integrity error and, + therefore, MUST NOT be included in the canonicalization of the + primary block. - * Reserved flags. + * Bundle is a fragment. (Bit 15, 0x0001) - * Bundle is a Fragment flag. + * Custody transfer requested for this bundle. (Bit 12, 0x0008) - o The CRC Type, Destination EID, Source Node ID, Report-To EID, - Creation Timestamp, and Lifetime fields are included, without - modification. + * Reserved (Bits 0-2, 0xE000) - o The fragment ID field MAY change if the bundle is fragmented in - transit and, as such, this field MUST NOT be included in the - canonicalization. + Regardless of the value of these flags in the primary block, they + MUST be set to 0 when canonicalized for security processing. o The CRC field MAY change at each hop - for example, if a bundle becomes fragmented, each fragment will have a different CRC value from the original signed primary block. As such, this field MUST NOT be included in the canonicalization. 4.3. Non-Primary-Block Canonicalization - All non-primary blocks (NPBs) in [BPBIS] share the same block - structure and should be canonicalized in the same way. - - Canonicalization for NPBs is dependent on whether the security - operation being performed is integrity or confidentiality. Integrity - operations consider every field in the block, whereas confidentiality - operations only consider the block-type-specific data. Since - confidentiality is applied to hide information (replacing plaintext - with ciphertext) it provides no benefit to include in the - confidentiality calculation information that MUST remain readable, - such as block fields other than the block-type-specific data. - - The fields that comprise a NPB, and any special considerations for - their representation in a canonical form, are as follows. - - o The Block Type Code field is included, without modification, for - integrity operations and omitted for confidentiality operations. - - o The Block Number field is included, without modification, for - integrity operations and omitted for confidentiality operations. - - o The Block Processing Control Flags field is included, without - modification, for integrity operations and omitted for - confidentiality operations, with the exception of reserved flags - which are treated as 0 in both cases. + All non-primary blocks (NPBs) share the same block structure and are + canonicalized as specified in [BPBIS] with the following exceptions. - o The CRC type and CRC fields are included, without modification, - for integrity operations and omitted for confidentiality - operations. + o If the service being applied is a confidentiality service, then + the Block Type Code, Block Number, Block Processing Control Flags, + CRC Type and CRC Field (if present), and Block Data Length fields + MUST NOT be included in the canonicalization. Confidentiality + services are used to convert the Block Type Specific Data Fields + from plain-text to cipher-text. - o The Block Type Specific Data field is included, without - modification, for both integrity and confidentiality operations, + o The Block Type Specific Data Field is included, without + modification, for both integrity and confidentiality services, with the exception that in some cases only a portion of the payload data is to be processed. In such a case, only those bytes are included in the canonical form and additional cipher suite parameters are required to specify which part of the field is included. 5. Security Processing This section describes the security aspects of bundle processing. @@ -1031,196 +1056,209 @@ If a received bundle contains a BCB, the receiving node MUST determine whether it has the responsibility of decrypting the BCB security target and removing the BCB prior to delivering data to an application at the node or forwarding the bundle. If the receiving node is the destination of the bundle, the node MUST decrypt any BCBs remaining in the bundle. If the receiving node is not the destination of the bundle, the node MAY decrypt the BCB if directed to do so as a matter of security policy. + If the security policy of a security-aware node specifies that a + bundle should have applied confidentiality to a specific security + target and no such BCB is present in the bundle, then the node MUST + process this security target in accordance with the security policy. + This MAY involve removing the security target from the bundle. If + the removed security target is the payload block, the bundle MAY be + discarded. + If the relevant parts of an encrypted payload block cannot be decrypted (i.e., the decryption key cannot be deduced or decryption fails), then the bundle MUST be discarded and processed no further. If an encrypted security target other than the payload block cannot be decrypted then the associated security target and all security blocks associated with that target MUST be discarded and processed no further. In both cases, requested status reports (see [BPBIS]) MAY be generated to reflect bundle or block deletion. When a BCB is decrypted, the recovered plain-text MUST replace the - cipher-text in the security target body data + cipher-text in the security target Block Type Specific Data Fields. + If the Block Data Length field was modified at the time of encryption + it MUST be updated to reflect the decrypted block length. If a BCB contains multiple security targets, all security targets - MUST be processed if the BCB is processed by the Node. The effect of - this is to be the same as if each security target had been + MUST be processed when the BCB is processed. Errors and other + processing steps SHALL be made as if each security target had been represented by an individual BCB with a single security target. 5.1.2. Receiving BIB Blocks If a received bundle contains a BIB, the receiving node MUST - determine whether it has the responsibility of verifying the BIB - security target and whether to remove the BIB prior to delivering - data to an application at the node or forwarding the bundle. + determine whether it has the final responsibility of verifying the + BIB security target and removing it prior to delivering data to an + application at the node or forwarding the bundle. If a BIB check + fails, the security target has failed to authenticate and the + security target SHALL be processed according to the security policy. + A bundle status report indicating the failure MAY be generated. + Otherwise, if the BIB verifies, the security target is ready to be + processed for delivery. A BIB MUST NOT be processed if the security target of the BIB is also the security target of a BCB in the bundle. Given the order of operations mandated by this specification, when both a BIB and a BCB share a security target, it means that the security target MUST have been encrypted after it was integrity signed and, therefore, the BIB cannot be verified until the security target has been decrypted by processing the BCB. If the security policy of a security-aware node specifies that a bundle should have applied integrity to a specific security target and no such BIB is present in the bundle, then the node MUST process this security target in accordance with the security policy. This MAY involve removing the security target from the bundle. If the removed security target is the payload or primary block, the bundle MAY be discarded. This action may occur at any node that has the ability to verify an integrity signature, not just the bundle destination. - If the bundle has a BIB and the receiving node is the destination for - the bundle, the node MUST verify the security target in accordance - with the cipher suite specification. If a BIB check fails, the - security target has failed to authenticate and the security target - SHALL be processed according to the security policy. A bundle status - report indicating the failure MAY be generated. Otherwise, if the - BIB verifies, the security target is ready to be processed for - delivery. - - If the bundle has a BIB and the receiving node is not the bundle - destination, the receiving node MAY attempt to verify the value in - the security result field. If the check fails, the node SHALL - process the security target in accordance to local security policy. - It is RECOMMENDED that if a payload integrity check fails at a - waypoint that it is processed in the same way as if the check fails - at the destination. + If a receiving node does not have the final responsibility of + verifying the BIB it MAY still attempt to verify the BIB to prevent + the needless forwarding of corrupt data. If the check fails, the + node SHALL process the security target in accordance to local + security policy. It is RECOMMENDED that if a payload integrity check + fails at a waypoint that it is processed in the same way as if the + check fails at the destination. If the check passes, the node MUST + NOT remove the BIB prior to forwarding. If a BIB contains multiple security targets, all security targets - MUST be processed if the BIB is processed by the Node. The effect of - this is to be the same as if each security target had been - represented by an individual BIB with a single security target. + MUST be processed if the BIB is processed by the Node. Errors and + other processing steps SHALL be made as if each security target had + been represented by an individual BIB with a single security target. 5.2. Bundle Fragmentation and Reassembly - If it is necessary for a node to fragment a bundle and security - services have been applied to that bundle, the fragmentation rules - described in [BPBIS] MUST be followed. As defined there and repeated - here for completeness, only the payload may be fragmented; security - blocks, like all extension blocks, can never be fragmented. + If it is necessary for a node to fragment a bundle payload, and + security services have been applied to that bundle, the fragmentation + rules described in [BPBIS] MUST be followed. As defined there and + summarized here for completeness, only the payload block may be + fragmented; security blocks, like all extension blocks, can never be + fragmented. - Due to the complexity of bundle fragmentation, including the - possibility of fragmenting bundle fragments, integrity and + Due to the complexity of payload block fragmentation, including the + possibility of fragmenting payload block fragments, integrity and confidentiality operations are not to be applied to a bundle - representing a fragment (i.e., a bundle whose "bundle is a Fragment" - flag is set in the Bundle Processing Control Flags field). - Specifically, a BCB or BIB MUST NOT be added to a bundle fragment, - even if the security target of the security block is not the payload. - When integrity and confidentiality must be applied to a fragment, we - RECOMMEND that encapsulation be used instead. + representing a fragment. Specifically, a BCB or BIB MUST NOT be + added to a bundle if the "Bundle is a Fragment" flag is set in the + Bundle Processing Control Flags field. + + Security processing in the presence of payload block fragmentation + MAY be handled by other mechanisms outside of the BPSec protocol or + by applying BPSec blocks in coordination with an encapsulation + mechanism. 6. Key Management - Key management in delay-tolerant networks is recognized as a - difficult topic and is one that this specification does not attempt - to solve. + There exist a myriad of ways to establish, communicate, and otherwise + manage key information in a DTN. Certain DTN deployments might + follow established protocols for key management whereas other DTN + deployments might require new and novel approaches. BPSec assumes + that key management is handled as a separate part of network design + and this specification neither defines nor requires a specific key + management strategy. -7. Policy Considerations +7. Security Policy Considerations When implementing BPSec, several policy decisions must be considered. This section describes key policies that affect the generation, forwarding, and receipt of bundles that are secured using this - specification. + specification. No single set of policy decisions is envisioned to + work for all secure DTN deployments. o If a bundle is received that contains more than one security operation, in violation of BPSec, then the BPA must determine how to handle this bundle. The bundle may be discarded, the block affected by the security operation may be discarded, or one security operation may be favored over another. o BPAs in the network MUST understand what security operations they should apply to bundles. This decision may be based on the source of the bundle, the destination of the bundle, or some other information related to the bundle. - o If an intermediate receiver has been configured to add a security - operation to a bundle, and the received bundle already has the - security operation applied, then the receiver MUST understand what - to do. The receiver may discard the bundle, discard the security - target and associated BPSec blocks, replace the security - operation, or some other action. + o If a waypoint has been configured to add a security operation to a + bundle, and the received bundle already has the security operation + applied, then the receiver MUST understand what to do. The + receiver may discard the bundle, discard the security target and + associated BPSec blocks, replace the security operation, or some + other action. o It is recommended that security operations only be applied to the - payload block, the primary block, and any block-types specifically - identified in the security policy. If a BPA were to apply - security operations such as integrity or confidentiality to every - block in the bundle, regardless of the block type, there could be - downstream errors processing blocks whose contents must be - inspected at every hop in the network path. + blocks that absolutely need them. If a BPA were to apply security + operations such as integrity or confidentiality to every block in + the bundle, regardless of need, there could be downstream errors + processing blocks whose contents must be inspected or changed at + every hop along the path. o Adding a BIB to a security target that has already been encrypted - by a BCB is not allowed. Therefore, we recommend three methods to - add an integrity signature to an encrypted security target. + by a BCB is not allowed. If this condition is likely to be + encountered, there are (at least) three possible policies that + could handle this situation. 1. At the time of encryption, an integrity signature may be generated and added to the BCB for the security target as additional information in the security result field. 2. The encrypted block may be replicated as a new block and integrity signed. 3. An encapsulation scheme may be applied to encapsulate the security target (or the entire bundle) such that the encapsulating structure is, itself, no longer the security target of a BCB and may therefore be the security target of a BIB. 8. Security Considerations - Given the nature of delay-tolerant networking applications, it is - expected that bundles may traverse a variety of environments and - devices which each pose unique security risks and requirements on the - implementation of security within BPSEC. For these reasons, it is - important to introduce key threat models and describe the roles and - responsibilities of the BPSEC protocol in protecting the - confidentiality and integrity of the data against those threats - throughout the DTN. This section provides additional discussion on - security threats that BPSEC will face and describe in additional - detail how BPSEC security mechanisms operate to mitigate these - threats. + Given the nature of DTN applications, it is expected that bundles may + traverse a variety of environments and devices which each pose unique + security risks and requirements on the implementation of security + within BPSec. For these reasons, it is important to introduce key + threat models and describe the roles and responsibilities of the + BPSec protocol in protecting the confidentiality and integrity of the + data against those threats. This section provides additional + discussion on security threats that BPSec will face and describes how + BPSec security mechanisms operate to mitigate these threats. It should be noted that BPSEC addresses only the security of data traveling over the DTN, not the underlying DTN itself. Additionally, - BPSEC addresses neither the fitness of externally-defined + BPSec addresses neither the fitness of externally-defined cryptographic methods nor the security of their implementation. It - is the responsibility of the BPSEC implementer that appropriate - algorithms and methods are chosen. Furthermore, the BPSEC protocol + is the responsibility of the BPSec implementer that appropriate + algorithms and methods are chosen. Furthermore, the BPSec protocol does not address threats which share computing resources with the DTN - and/or BPSEC software implementations. These threats may be + and/or BPSec software implementations. These threats may be malicious software or compromised libraries which intend to intercept data or recover cryptographic material. Here, it is the - responsibility of the BPSEC implementer to ensure that any + responsibility of the BPSec implementer to ensure that any cryptographic material, including shared secret or private keys, is protected against access within both memory and storage devices. The threat model described here is assumed to have a set of capabilities identical to those described by the Internet Threat - Model in [RFC3552], but the BPSEC threat model is scoped to - illustrate threats specific to BPSEC operating within DTN + Model in [RFC3552], but the BPSec threat model is scoped to + illustrate threats specific to BPSec operating within DTN environments and therefore focuses on man-in-the-middle (MITM) attackers. 8.1. Attacker Capabilities and Objectives - BPSEC was designed to protect against MITM threats which may have + BPSec was designed to protect against MITM threats which may have access to a bundle during transit from its source, Alice, to its destination, Bob. A MITM node, Mallory, is a non-cooperative node operating on the DTN between Alice and Bob that has the ability to receive bundles, examine bundles, modify bundles, forward bundles, and generate bundles at will in order to compromise the confidentiality or integrity of data within the DTN. For the purposes of this section, any MITM node is assumed to effectively be security-aware even if it does not implement the BPSec protocol. There are three classes of MITM nodes which are differentiated based on their access to cryptographic material: @@ -1283,21 +1322,21 @@ will also be able to modify the received bundle, including non-BPSec data such as the primary block, payload blocks, or block processing control flags as defined in [BPBIS]. Mallory will be able to undertake activities which include modification of data within the blocks, replacement of blocks, addition of blocks, or removal of blocks. Within BPSec, both the BIB and BCB provide integrity protection mechanisms to detect or prevent data manipulation attempts by Mallory. The BIB provides that protection to another block which is its - security target. The cryptographic mechansims used to generate the + security target. The cryptographic mechanisms used to generate the BIB should be strong against collision attacks and Mallory should not have access to the cryptographic material used by the originating node to generate the BIB (e.g., K_A). If both of these conditions are true, Mallory will be unable to modify the security target or the BIB and lead Bob to validate the security target as originating from Alice. Since BPSec security operations are implemented by placing blocks in a bundle, there is no in-band mechanism for detecting or correcting certain cases where Mallory removes blocks from a bundle. If Mallory @@ -1368,21 +1407,21 @@ BPSec relies on cipher suite capabilities to prevent replay or forged message attacks. A BCB used with appropriate cryptographic mechanisms (e.g., a counter-based cipher mode) may provide replay protection under certain circumstances. Alternatively, application data itself may be augmented to include mechanisms to assert data uniqueness and then protected with a BIB, a BCB, or both along with other block data. In such a case, the receiving node would be able to validate the uniqueness of the data. -9. Ciphersuite Authorship Considerations +9. Cipher Suite Authorship Considerations Cipher suite developers or implementers should consider the diverse performance and conditions of networks on which the Bundle Protocol (and therefore BPSec) will operate. Specifically, the delay and capacity of delay-tolerant networks can vary substantially. Cipher suite developers should consider these conditions to better describe the conditions when those suites will operate or exhibit vulnerability, and selection of these suites for implementation should be made with consideration to the reality. There are key differences that may limit the opportunity to leverage existing @@ -1401,37 +1440,52 @@ time may be extremely large. This may limit the utility of session key generation mechanisms, such as Diffie-Hellman, as a two-way handshake may not be feasible or reliable. o Opportunistic Access: Depending on the application environment, a given endpoint may not be guaranteed to be accessible within a certain amount of time. This may make asymmetric cryptographic architectures which rely on a key distribution center or other trust center impractical under certain conditions. + When developing new cipher suites for use with BPSec, the following + information SHOULD be considered for inclusion in these + specifications. + + o New Parameters. Cipher suites MAY define new parameter types that + may appear in security blocks and used to configure the cipher + suite. + + o New Results. Cipher suites MAY define new security result types + that may appear in security blocks and capture the outputs of the + cipher suite. + + o New Canonicalizations. Cipher suites MAY define new + canonicalization algorithms as necessary. + 10. Defining Other Security Blocks Other security blocks (OSBs) may be defined and used in addition to the security blocks identified in this specification. Both the usage of BIB, BCB, and any future OSBs MAY co-exist within a bundle and MAY be considered in conformance with BPSec if each of the following requirements are met by any future identified security blocks. o Other security blocks (OSBs) MUST NOT reuse any enumerations identified in this specification, to include the block type codes for BIB and BCB. o An OSB definition MUST state whether it can be the target of a BIB or a BCB. The definition MUST also state whether the OSB can target a BIB or a BCB. - o An OSB definition MUST provide a deterinistic processing order in + o An OSB definition MUST provide a deterministic processing order in the event that a bundle is received containing BIBs, BCBs, and OSBs. This processing order MUST NOT alter the BIB and BCB processing orders identified in this specification. o An OSB definition MUST provide a canonicalization algorithm if the default non-primary-block canonicalization algorithm cannot be used to generate a deterministic input for a cipher suite. This requirement MAY be waived if the OSB is defined so as to never be the security target of a BIB or a BCB. @@ -1460,122 +1514,59 @@ 11. Conformance All implementations are strongly RECOMMENDED to provide some method of hop-by-hop verification by generating a hash to some canonical form of the bundle and placing an integrity signature on that form using a BIB. 12. IANA Considerations - This protocol has fields that have been registered by IANA. + Registries of Cipher Suite IDs, Cipher Suite Flags, Cipher Suite + Parameter Types, and Security Result Types will be required. 12.1. Bundle Block Types - This specification allocates three block types from the existing + This specification allocates two block types from the existing "Bundle Block Types" registry defined in [RFC6255] . Additional Entries for the Bundle Block-Type Codes Registry: +-------+-----------------------------+---------------+ | Value | Description | Reference | +-------+-----------------------------+---------------+ - | 2 | Block Integrity Block | This document | - | 3 | Block Confidentiality Block | This document | + | TBD | Block Integrity Block | This document | + | TBD | Block Confidentiality Block | This document | +-------+-----------------------------+---------------+ - Table 2 - -12.2. Cipher Suite Flags - - This protocol has a cipher suite flags field and certain flags are - defined. An IANA registry has been set up as follows. - - The registration policy for this registry is: Specification Required - - The Value range is: Variable Length - Cipher Suite Flag Registry: - - +--------------------------+-------------------------+--------------+ - | Bit Position (right to | Description | Reference | - | left) | | | - +--------------------------+-------------------------+--------------+ - | 0 | Block contains result | This | - | | | document | - | 1 | Block Contains | This | - | | parameters | document | - | 2 | Source EID ref present | This | - | | | document | - | >3 | Reserved | This | - | | | document | - +--------------------------+-------------------------+--------------+ - Table 3 -12.3. Parameters and Results - - This protocol has fields for cipher suite parameters and results. - The field is a type-length-value triple and a registry is required - for the "type" sub-field. The values for "type" apply to both the - cipher suite parameters and the cipher suite results fields. Certain - values are defined. An IANA registry has been set up as follows. - - The registration policy for this registry is: Specification Required - - The Value range is: 8-bit unsigned integer. - - Cipher Suite Parameters and Results Type Registry: - - +---------+-------------------------------------------+-------------+ - | Value | Description | Reference | - +---------+-------------------------------------------+-------------+ - | 0 | reserved | Section 3.6 | - | 1 | initialization vector (IV) | Section 3.6 | - | 2 | reserved | Section 3.6 | - | 3 | key information | Section 3.6 | - | 4 | content-range (pair of Unsigned Integers) | Section 3.6 | - | 5 | integrity signature | Section 3.6 | - | 6 | unassigned | Section 3.6 | - | 7 | salt | Section 3.6 | - | 8 | BCB integrity check value (ICV) | Section 3.6 | - | 9-191 | reserved | Section 3.6 | - | 192-250 | private use | Section 3.6 | - | 251-255 | reserved | Section 3.6 | - +---------+-------------------------------------------+-------------+ - - Table 4 - 13. References 13.1. Normative References [BPBIS] Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol", - draft-ietf-dtn-bpbis-04 (work in progress), July 2016. + draft-ietf-dtn-bpbis-06 (work in progress), July 2016. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on Security Considerations", BCP 72, RFC 3552, DOI 10.17487/RFC3552, July 2003, . [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol IANA Registries", RFC 6255, May 2011. 13.2. Informative References - [BPBISCBOR] - Burleigh, S., "Bundle Protocol CBOR Representation - Specification", draft-burleigh-dtn-rs-cbor-01 (work in - progress), April 2016. - [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant Networking Architecture", RFC 4838, April 2007. [RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell, "Bundle Security Protocol Specification", RFC 6257, May 2011. [SBSP] Birrane, E., "Streamlined Bundle Security Protocol", draft-birrane-dtn-sbsp-01 (work in progress), October