--- 1/draft-ietf-dtn-bpsec-00.txt 2016-03-20 00:17:33.432618693 -0700 +++ 2/draft-ietf-dtn-bpsec-01.txt 2016-03-20 00:17:33.596622760 -0700 @@ -1,115 +1,114 @@ Delay-Tolerant Networking E. Birrane Internet-Draft JHU/APL Intended status: Experimental J. Mayer -Expires: July 1, 2016 INSYEN AG +Expires: September 20, 2016 INSYEN AG D. Iannicca NASA GRC - December 29, 2015 + March 19, 2016 Bundle Protocol Security Specification - draft-ietf-dtn-bpsec-00 + draft-ietf-dtn-bpsec-01 Abstract - This document defines a security protocol providing data - authentication, integrity, and confidentiality services for the - Bundle Protocol. Capabilities are provided to protect blocks in a - bundle along a single path through a network. + This document defines a security protocol providing data integrity + and confidentiality services for the Bundle Protocol. Capabilities + are provided to protect blocks in a bundle along a single path + through a network. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 July 1, 2016. + This Internet-Draft will expire on September 20, 2016. Copyright Notice - Copyright (c) 2015 IETF Trust and the persons identified as the + Copyright (c) 2016 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. Related Documents . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. Key Properties . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Block-Level Granularity . . . . . . . . . . . . . . . . . 6 - 2.2. Multiple Security Sources . . . . . . . . . . . . . . . . 7 - 2.3. Single Security Destinations . . . . . . . . . . . . . . 7 - 2.4. Mixed Security Policy . . . . . . . . . . . . . . . . . . 8 - 2.5. User-Selected Ciphersuites . . . . . . . . . . . . . . . 8 - 2.6. Deterministic Processing . . . . . . . . . . . . . . . . 8 - 3. Security Block Definitions . . . . . . . . . . . . . . . . . 9 - 3.1. Block Identification . . . . . . . . . . . . . . . . . . 10 - 3.2. Abstract Security Block . . . . . . . . . . . . . . . . . 11 - 3.3. Block Ordering . . . . . . . . . . . . . . . . . . . . . 14 - 3.4. Bundle Authentication Block . . . . . . . . . . . . . . . 15 - 3.5. Block Integrity Block . . . . . . . . . . . . . . . . . . 16 - 3.6. Block Confidentiality Block . . . . . . . . . . . . . . . 17 - 3.7. Cryptographic Message Syntax Block . . . . . . . . . . . 19 - 3.8. Block Interactions . . . . . . . . . . . . . . . . . . . 20 - 3.9. Parameters and Result Fields . . . . . . . . . . . . . . 22 - 3.10. BSP Block Example . . . . . . . . . . . . . . . . . . . . 24 - 4. Security Processing . . . . . . . . . . . . . . . . . . . . . 27 - 4.1. Canonical Forms . . . . . . . . . . . . . . . . . . . . . 27 - 4.1.1. Bundle Canonicalization . . . . . . . . . . . . . . . 27 - 4.1.2. Block Canonicalization . . . . . . . . . . . . . . . 28 - 4.1.3. Considerations . . . . . . . . . . . . . . . . . . . 31 - 4.2. Endpoint ID Confidentiality . . . . . . . . . . . . . . . 32 - 4.3. Bundles Received from Other Nodes . . . . . . . . . . . . 32 - 4.3.1. Receiving BAB Blocks . . . . . . . . . . . . . . . . 32 - 4.3.2. Receiving BCB Blocks . . . . . . . . . . . . . . . . 33 - 4.3.3. Receiving BIB Blocks . . . . . . . . . . . . . . . . 33 - 4.4. Receiving CMSB Blocks . . . . . . . . . . . . . . . . . . 34 - 4.5. Bundle Fragmentation and Reassembly . . . . . . . . . . . 34 - 4.6. Reactive Fragmentation . . . . . . . . . . . . . . . . . 35 - 5. Key Management . . . . . . . . . . . . . . . . . . . . . . . 35 - 6. Policy Considerations . . . . . . . . . . . . . . . . . . . . 35 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 36 - 8. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 37 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 - 9.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 37 - 9.2. Cipher Suite Flags . . . . . . . . . . . . . . . . . . . 37 - 9.3. Parameters and Results . . . . . . . . . . . . . . . . . 38 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 39 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 39 - 10.2. Informative References . . . . . . . . . . . . . . . . . 39 - Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 40 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 + 2.2. Multiple Security Sources . . . . . . . . . . . . . . . . 6 + 2.3. Mixed Security Policy . . . . . . . . . . . . . . . . . . 7 + 2.4. User-Selected Ciphersuites . . . . . . . . . . . . . . . 8 + 2.5. Deterministic Processing . . . . . . . . . . . . . . . . 8 + 3. Security Block Definitions . . . . . . . . . . . . . . . . . 8 + 3.1. Block Identification . . . . . . . . . . . . . . . . . . 9 + 3.2. Block Representation . . . . . . . . . . . . . . . . . . 9 + 3.2.1. CMS Block Type-Specific Data Fields . . . . . . . . . 10 + 3.2.2. BIB and BCB Block Type-Specific Data Fields . . . . . 10 + 3.3. Block Ordering . . . . . . . . . . . . . . . . . . . . . 11 + 3.4. Block Integrity Block . . . . . . . . . . . . . . . . . . 12 + 3.5. Block Confidentiality Block . . . . . . . . . . . . . . . 13 + 3.6. Cryptographic Message Syntax Block . . . . . . . . . . . 15 + 3.7. Block Interactions . . . . . . . . . . . . . . . . . . . 16 + 3.8. Parameters and Result Fields . . . . . . . . . . . . . . 17 + 3.9. BSP Block Example . . . . . . . . . . . . . . . . . . . . 19 + 4. Security Processing . . . . . . . . . . . . . . . . . . . . . 22 + 4.1. Canonical Forms . . . . . . . . . . . . . . . . . . . . . 22 + 4.1.1. Block Canonicalization . . . . . . . . . . . . . . . 22 + 4.1.2. Considerations . . . . . . . . . . . . . . . . . . . 25 + 4.2. Endpoint ID Confidentiality . . . . . . . . . . . . . . . 25 + 4.3. Bundles Received from Other Nodes . . . . . . . . . . . . 26 + 4.3.1. Receiving BCB Blocks . . . . . . . . . . . . . . . . 26 + 4.3.2. Receiving BIB Blocks . . . . . . . . . . . . . . . . 26 + 4.4. Receiving CMSB Blocks . . . . . . . . . . . . . . . . . . 27 + 4.5. Bundle Fragmentation and Reassembly . . . . . . . . . . . 27 + 4.6. Reactive Fragmentation . . . . . . . . . . . . . . . . . 28 + 5. Key Management . . . . . . . . . . . . . . . . . . . . . . . 28 + 6. Policy Considerations . . . . . . . . . . . . . . . . . . . . 28 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 29 + 8. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 29 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 + 9.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 30 + 9.2. Cipher Suite Flags . . . . . . . . . . . . . . . . . . . 30 + 9.3. Parameters and Results . . . . . . . . . . . . . . . . . 31 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 31 + 10.2. Informative References . . . . . . . . . . . . . . . . . 32 + + Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 32 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 1. Introduction This document defines security features for the Bundle Protocol - [RFC5050] intended for use in delay-tolerant networks, in order to + [BPBIS] intended for use in delay-tolerant networks, in order to provide Delay-Tolerant Networking (DTN) security services. 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 stressed environment of the underlying networks over which the @@ -117,46 +116,45 @@ 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, integrity, and availability. This document describes the Bundle Protocol Security Specification (BPSec), which provides security services for blocks within a bundle from the bundle source to the bundle destination. Specifically, - BPSec provides authentication, integrity, and confidentiality for - bundles along a path through a DTN. + BPSec provides integrity and confidentiality for bundles along a path + through a 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. 1.1. 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. - The DTN Bundle Protocol [RFC5050] defines the format and processing - of the blocks used to implement the Bundle Protocol, excluding the + 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 Security Protocol [RFC6257] and Streamlind Bundle Security Protocol [SBSP] introduce the concepts of security blocks for - authentication, confidentiality, and integrity. BPSec is based off - of this document. + security services. BPSec is based off of these documents. 1.2. 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]. We introduce the following terminology for purposes of clarity. @@ -168,40 +166,40 @@ o Forwarder - the bundle node that forwarded 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 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. - Figure 1 below is adapted from [RFC5050] and shows four bundle nodes + Figure 1 below is adapted from [BPBIS] and shows four bundle nodes (denoted BN1, BN2, BN3, and BN4) that reside above some transport layer(s). Three distinct transport and network protocols (denoted 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 Sit at the Application Layer of the Internet - Model + Figure 1: Bundle Nodes Sitting at the Application Layer of the + Internet Model 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. If node BN2 originates a bundle (for example, a bundle status report @@ -211,26 +209,20 @@ bundle (as well as being the final intermediate receiver). We introduce the following security-specific DTN terminology. o Security-Service - the security features supported by this specification: authentication, integrity, and confidentiality. o Security-Source - a bundle node that adds a security block to a bundle. - o Security-Destination - a bundle node that evaluates a security - block from a bundle. When a security-service is applied hop-by- - hop, the security-destination is the next intermediate receiver. - Otherwise, the security-destination is the same as the bundle - destination. - o Security-Target - the portion of a bundle (e.g., the primary block, payload block, extension block, or entire bundle) that receives a security-service as part of a security-operation. o Security Block - a single instance of a BPSec extension block in a bundle. o Security-Operation - the application of a security-service to a specific security-target, notated as OP(security-service, security-target). For example, OP(authentication, bundle) or @@ -294,459 +286,271 @@ 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. A bundle MAY have multiple security blocks and these blocks MAY have different security-sources. Each security block in a bundle will be associated with a specific security-operation. All security blocks - comprising a security-operation MUST have the same security-source - and security-destination. + comprising a security-operation MUST have the same security-source. - As required in [RFC5050], forwarding nodes MUST transmit blocks in a + As required in [BPBIS], forwarding nodes MUST transmit blocks in a bundle in the same order in which they were received. This requirement applies to all DTN nodes, not just ones that implement security processing. Blocks in a bundle MAY be added or deleted according to the applicable specification, but those blocks that are both received and transmitted MUST be transmitted in the same order that they were received. -2.3. Single Security Destinations - - The destination of all security blocks in a bundle MUST be the bundle - destination, with the exception of authentication security blocks, - whose destination is the next hop along the bundle path. In a DTN, - there is typically no guarantee that a bundle will visit a particular - intermediate receiver during its journey, or that a particular series - of intermediate receivers will be visited in a particular order. - - Security-destinations different from bundle destinations would place - a tight (and possibly intractable) coupling between security and - routing services in an overlay network. - -2.4. Mixed Security Policy +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. Extension blocks representing security services MUST have their block processing flags set such that the block (and bundle, where applicable) will be treated appropriately by non-security-aware nodes. - Extension blocks providing integrity and authentication 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. + 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. -2.5. User-Selected Ciphersuites +2.4. User-Selected Ciphersuites The security services defined in this specification rely on a a variety of ciphersuites providing integrity signatures, ciphertext, and other information necessary to populate security blocks. Users may wish to select differing ciphersuites to implement different security services. For example, some users may wish to use a SHA-1 based hash for integrity whereas other users may require a SHA-2 hash instead. The security services defined in this specification MUST provide a mechanism for identifying what ciphersuite has been used to populate a security block. -2.6. Deterministic Processing +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. 3. Security Block Definitions - There are four types of security blocks that MAY be included in a - bundle. These are the Bundle Authentication Block (BAB), the Block - Integrity Block (BIB), the Block Confidentiality Block (BCB), and the - Cryptographic Messaging Syntax Block (CMSB). - - The BAB is used to ensure the authenticity and integrity of the - bundle along a single hop from forwarder to intermediate receiver. - As such, BABs operate between topologically adjacent nodes. - Security-aware nodes MAY choose to require BABs from a given - neighbor in the network in order to receive and process a received - bundle. + There are three types of security blocks that MAY be included in a + bundle. These are the Block Integrity Block (BIB), the Block + Confidentiality Block (BCB), and the Cryptographic Messaging Syntax + Block (CMSB). - The BIB is used to ensure the authenticity and integrity of its - security-target from the BIB security-source, which creates the - BIB, to the bundle destination, which verifies the BIB - authenticator. The authentication information in the BIB MAY - (when possible) be verified by any node in between the BIB - security-source and the bundle destination. + The BIB is used to ensure the integrity of its security-target. + 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 BCB indicates that the security-target has been encrypted, in whole or in part, at the BCB security-source in order to protect - its content while in transit to the bundle destination. + 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. The CMSB contains a Cryptographic Message Syntax (CMS) payload used to describe a security service applied to another extension block. NOTE: Applications may choose to simply place CMS text as the payload to the bundle. In such cases, security is considered to be implemented at the application layer and CMSBs are not required in that case. Certain cipher suites may allow or require multiple instances of a - block to appear in the bundle. For example, an authentication cipher + block to appear in the bundle. For example, an integrity cipher suite may require two security blocks, one before the payload block and one after. Despite the presence of two security blocks, they - both comprise the same security-operation - OP(authentication,bundle) - in this example. + both comprise the same security-operation - OP(integirty, target) in + this example. 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. Many of the fields in these block definitions use the Self-Delimiting Numeric Value (SDNV) type whose format and encoding is as defined in - [RFC5050]. + [BPBIS]. 3.1. Block Identification This specification requires that every target block of a security - operation be uniquely identifiable. In cases where there can only be - a single instance of a block in the bundle (as is the case with the - primary block and the payload block) then the unique identifier is - simply the block type. These blocks are described as "singleton - blocks". It is possible that a bundle may contain multiple instances - of a block type. In such a case, each instance of the block type - must be uniquely identifiable and the block type itself is not - sufficient for this identification. These blocks are described as - "non-singleton blocks". - - The definition of the extension block header from [RFC5050] does not - provide additional identifying information for a block beyond the - block type. The addition of an occurrence number to the block is - necessary to identify the block instance in the bundle. This section - describes the use of an Artificial EID (AEID) reference in a block - header to add unique identification for non-singleton blocks. - - Figure 7 of [RFC5050] illustrates that an EID reference in a block - header is the 2-tuple of the reference scheme and the reference - scheme specific part (SSP), each of which are encoded as SDNVs. The - AEID MUST encode the occurrence number in the reference scheme SDNV - and MUST set the reference SSP to 0. A reference SSP value of 0 is - an invalid offset for an SSP in the bundle dictionary and, therefore, - the use of 0 in this field identifies the reference as an AEID. - - The occurrence number MAY be any positive value that is not already - present as an occurrence number for the same block type in the - bundle. These numbers are independent of relative block position - within the bundle, and whether blocks of the same type have been - added or removed from the bundle. Once an AEID has been added to a - block instance, it MUST NOT be changed until all security operations - that target the block instance have been removed from the bundle. - - If a node wishes to apply a security operation to a target block it - MUST determine whether the target block is a singleton block or a - non-singleton block. If the target block is non-singleton, then the - node MUST find the AEID for the target. If an AEID is not present in - the target block header then the node MAY choose to either cancel the - security operation or add an AEID to the block, in accordance with - security policy. - - If a node chooses to add an AEID to a target block header it MUST - perform the following activities. - - o The "Block contains an EID reference field" flag MUST be set for - the target block, if it is not already set. - - o The EID reference count for the block MUST be updated to reflect - the addition of the AEID. - - o The scheme offset of the AEID MUST be a value greater than 0. The - scheme offset MUST NOT be the same as any other AEID of any other - block in the bundle sharing the same block type. - - o The SSP offset of the AEID MUST be the value 0. There MUST NOT be - any other EID in the block header that has a value of 0 for the - SSP offset. - - If there is no AEID present in a block, and if a node is unable to - add an AEID by following the above process, then the block MUST NOT - have an BPSec security operation applied to it. - - It is RECOMMENDED that every block in a bundle other than the primary - and payload blocks be treated as a non-singleton block. However, the - identification of singleton blocks SHOULD be in accordance with the - security policy of a node. + operation be uniquely identifiable. The definition of the extension + block header from [BPBIS] provides such a mechanism in the "block + number", which provides a unique identifier for a block within a + bundle. Within this specification, a target block will be identified + by its unique block number. -3.2. Abstract Security Block +3.2. Block Representation Each security block uses the Canonical Bundle Block Format as defined - in [RFC5050]. That is, each security block is comprised of the + in [BPBIS]. That is, each security block is comprised of the following elements: o Block Type Code - o Block Processing Control Flags + o Block Number - o Block EID Reference List (OPTIONAL) + o Block Processing Control Flags o Block Data Length o Block Type Specific Data Fields - Since the four security block types have most fields in common, we - can shorten the description of the block type specific data fields if - we first define an abstract security block (ASB) and then specify - each of the real blocks in terms of the fields that are present/ - absent in an ASB. Note that no bundle ever contains an actual ASB, - which is simply a specification artifact. - - The structure of an Abstract Security Block is given in Figure 2. - Although the diagram hints at a fixed-format layout, this is purely - for the purpose of exposition. Except for the "type" field, all - fields are variable in length. - - +-----------------------------+----------------------------------+ - | Block Type Code (BYTE) | Processing Control Flags (SDNV) | - +-----------------------------+----------------------------------+ - | EID Reference Count and List (Compound List) | - +-----------------------------+----------------------------------+ - | Block Length (SDNV) | Security Target (Compound) | - +-----------------------------+----------------------------------+ - | Cipher suite ID (SDNV) | Cipher suite Flags (SDNV) | - +-----------------------------+----------------------------------+ - | Params Length (SDNV) | Params Data (Compound) | - +-----------------------------+----------------------------------+ - | Result Length (SDNV) | Result Data (Compound) | - +-----------------------------+----------------------------------+ - - Figure 2: Abstract Security Block Structure - - An ASB consists of the following fields, some of which are optional. - - o Block-Type Code (Byte) - as described in [RFC5050]. The block- - type codes for security blocks are: - - * BundleAuthenticationBlock - BAB: 0x02 - - * BlockIntegrityBlock - BIB: 0x03 - - * BlockConfidentialityBlock - BCB: 0x04 - - o Block Processing Control Flags (SDNV) - as described in [RFC5050]. - There are no general constraints on the use of the block - processing control flags, and some specific requirements are - discussed later. - - o (OPTIONAL) EID Reference Count and List - as described in - [RFC5050]. Presence of the EID reference field is indicated by - the setting of the "Block contains an EID reference field" - (EID_REF) bit of the block processing control flags. If no EID - fields are present, then the composite field itself MUST be - omitted entirely and the EID_REF bit MUST be unset. A count field - of zero is not permitted. The possible EIDs are: - - (OPTIONAL) Security-source - specifies the security-source for - the block. If this is omitted, then the source of the bundle - is assumed to be the security-source unless otherwise indicated - by policy or associated cipher suite definition. When present, - the security-source MUST be the first EID in the list. +3.2.1. CMS Block Type-Specific Data Fields - (OPTIONAL) AEID - specifies an identifier that can be used to - uniquely identify an instance of a non-singleton block. This - field MUST be present for non-singleton blocks. This field - MUST NOT be present for singleton blocks, such as the primary - block and the payload block. The construction of the AEID is - discussed in Section 3.1. + The contents of the CMS block is a single field of CMS data whose + length is specified by the BLock Data Length parameter. - o Block Length (SDNV) - as described in [RFC5050]. +3.2.2. BIB and BCB Block Type-Specific Data Fields - o Block type specific data fields as follows: + The structure of the BIB and BCB type-specific data fields are + identifcal and given in Figure 2. Although the diagram hints at a + fixed-format layout, this is purely for the purpose of exposition. + Except for the "type" field, all fields are variable in length. + Fields annotated with an '*' are optional, with their inclusion in + the block indicated by the cipher suite flags field. - * Security-Target (Compound) - Uniquely identifies the target of - the associated security-operation. + +---------------------------+-------------------------+ + | Security Target (SDNV) | Cipher suite ID (SDNV) | + +---------------------------+-------------------------+ + | Cipher suite Flags (SDNV) | *Source EID (Compound) | + +---------------------------+-------------------------+ + | *Parameters (Compound) | *Sec. Result (Compound) | + +---------------------------+-------------------------+ - As discussed in Section 3.1 a singleton block is identified by - its block type and a non-singleton block is identified by the - combination of its block type and an occurrence number. The - security-target is a compound field that contains the block - type (as a byte) and occurrence number (as an SDNV). + Figure 2: BIB and BCB Block Structure - The occurrence number of a singleton block MUST be set to 0. - The occurrence number of a non-singleton block MUST be set to - the scheme offset of the AEID associated with the block being - targeted by the security operation. + The BIB and BCB type-specific data fields consist of the following + fields, some of which are optional. - * (OPTIONAL) Cipher suite ID (SDNV) + o Security-Target (SDNV) - Uniquely identifies the target of the + associated security-operation. This MUST be the block number of a + block in the bundle. - * (OPTIONAL) Cipher suite flags (SDNV) + o Cipher suite ID (SDNV) - Identifies the ciphersuite used to + implement the security service reprsented by this block. - * (OPTIONAL) Cipher Suite Parameters - compound field of the next - two items. + o Cipher suite flags (SDNV) - 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. - + Cipher suite parameters length (SDNV) - specifies the length - of the next field, which is the cipher suite-parameters data - field. + * bits 6-3 are reserved for future use. - + Cipher suite parameters data - parameters to be used with - the cipher suite in use, e.g., a key identifier or - initialization vector (IV). See Section 3.9 for a list of - potential parameters and their encoding rules. The - particular set of parameters that is included in this field - is defined as part of a cipher suite specification. + * src - bit 2 indicates whether the security source EID is + present in the block. This identifief the EID that inserted + the security service in the bundle. If the security source is + not present then the souce of the block MAY be taken to be the + bundle source, the previous hop, or some other EID as defined + by security policy. - * (OPTIONAL) Security Result - compound field of the next two - items. + * parm - bit 1 indicates whether or not the cipher suite + parameters fields are present in the block. - + Security result length (SDNV) - contains the length of the - next field, which is the security-result data field. + * res - bit 0 indicates whether or not the security result fields + are present in the block. - + Security result data - contains the results of the - appropriate cipher suite specific calculation (e.g., a - signature, Message Authentication Code (MAC), or cipher-text - block key). + Bit Bit Bit Bit Bit Bit Bit + 6 5 4 3 2 1 0 + +-----+-----+-----+-----+-----+-----+-----+ + | reserved | src |parm | res | + +-----+-----+-----+-----+-----+-----+-----+ - The structure of the cipher suite flags field is shown in Figure 3. - In each case, 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 missing. Presently, - there are three flags defined for the field; for convenience, these - are shown as they would be extracted from a single-byte SDNV. Future - additions may cause the field to grow to the left so, as with the - flags fields defined in [RFC5050], the description below numbers the - bit positions from the right rather than the standard RFC definition, - which numbers bits from the left. + Figure 3: Cipher suite flags - bits 6-3 are reserved for future use. + o (OPTIONAL) Parameters - compound field of the following two items. - src - bit 2 indicates whether the EID-reference field of the ASB - contains the optional reference to the security-source. + * Length (SDNV) - specifies the length of the next field, which + captures the parameters data. - parm - bit 1 indicates whether or not the cipher suite parameters - length and cipher suite parameters data fields are present. + * Data - A byte array encoding one or more cipher suite + parameters, with each parameter represented as a Type-Length- + Value (TLV) triplet. In this triplet, the type and length are + represented as SDNVs and the value is a byte array holding the + parmeter. See Section 3.8 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. - res - bit 0 indicates whether or not the ASB contains the - security-result length and security-result data fields. + o (OPTIONAL) Security Result - compound field of the next two items. - Bit Bit Bit Bit Bit Bit Bit - 6 5 4 3 2 1 0 - +-----+-----+-----+-----+-----+-----+-----+ - | reserved | src |parm | res | - +-----+-----+-----+-----+-----+-----+-----+ + * Length (SDNV) - specifies the length of the next field, which + is the security-result data. - Figure 3: Cipher Suite Flags + * Data - A byte array containing the results of the appropriate + cipher suite specific calculation (e.g., a signature, Message + Authentication Code (MAC), or cipher-text block key). 3.3. Block Ordering A security-operation may be implemented in a bundle using either one - or two security blocks. For example, the operation - OP(authentication, bundle) MAY be accomplished by a single BAB block - in the bundle, or it MAY be accomplished by two BAB blocks in the - bundle. To avoid confusion, we use the following terminology to - identify the block or blocks comprising a security-operation. + or two security blocks. For example, the operation OP(integrity, + block) MAY be accomplished by a single BIB block in the bundle, or it + MAY be accomplished by two BIB blocks in the bundle. To avoid + confusion, we use the following terminology to identify the block or + blocks comprising a security-operation. The terms "First" and "Last" are used ONLY when describing multiple security blocks comprising a single security-operation. A "First" block refers to the security block that is closest to the primary block in the canonical form of the bundle. A "Last" block refers to the security block that is furthest from the primary block in the canonical form of the bundle. If a single security block implements the security-operation, then it is referred to as a "Lone" block. For example, when a bundle - authentication cipher suite requires a single BAB block we refer to + authentication cipher suite requires a single BIB block we refer to it as a Lone BAB. When a bundle authentication cipher suite requires - two BAB blocks we refer to them as the First BAB and the Last BAB. + two BIB blocks we refer to them as the First BIB and the Last BIB. This specification and individual cipher suites impose restrictions on what optional fields must and must not appear in First blocks, Last blocks, and Lone blocks. -3.4. Bundle Authentication Block - - This section describes typical field values for the BAB, which is - solely used to implement OP(authentication, bundle). - - The block-type code field value MUST be 0x02. - - 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. - - The security-target MUST be the entire bundle, which MUST be - represented by a of <0x00><0x00>. - - The cipher suite ID MUST be documented as a hop-by-hop - authentication cipher suite. When a Lone BAB is used, the cipher - suite MUST be documented as requiring one instance of the BAB. - When a First BAB and Last BAB are used, the cipher suite MUST be - documented as requiring two instances of the BAB. - - The cipher suite parameters field MAY be present, if so specified - in the cipher suite specification. - - An EID-reference to the security-source MAY be present in either a - First BAB or a Lone BAB. An EID-reference to the security-source - MUST NOT be present in a Last BAB. - - The security-result captures the result of applying the cipher - suite calculation (e.g., the MAC or signature) to the relevant - parts of the bundle, as specified in the cipher suite definition. - This field MUST be present in either a Lone BAB or a Last BAB. - This field MUST NOT be present in a First BAB. - - Notes: - - o When multiple BAB blocks are used, the mandatory fields of the - Last BAB must match those of the First BAB. - - o The First BAB or Lone BAB, when present, SHOULD immediately follow - the primary block. - - o A Last BAB, when present, SHOULD be the last block in the bundle. - - o Since OP(authentication, bundle) is allowed only once in a bundle, - it is RECOMMENDED that users wishing to support multiple - authentication signatures define a multi-target cipher suite, - capturing multiple security results in cipher suite parameters. - -3.5. Block Integrity Block +3.4. Block Integrity Block A BIB is an ASB with the following additional restrictions: - The block-type code value MUST be 0x03. + The block-type code value MUST be 0x02. 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. - The security-target MUST uniquely identify a block within the - bundle. The reserved block type 0x01 specifies the singleton - payload block. The reserved type 0x00 specifies the singleton - primary block. The security-target for a BIB MUST NOT reference a - security block defined in this specification (BAB, BIB, or BCB). + The security-target MUST match the BLock Number of a block within + the bundle. The security-target for a BIB MUST NOT reference a + security block defined in this specification (BIB, BCB, or CMSB). 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. The cipher suite parameters field MAY be present in either a Lone BIB or a First BIB. This field MUST NOT be present in a Last BIB. An EID-reference to the security-source MAY be present in either a Lone BIB or a First BIB. This field MUST NOT be present in a Last @@ -768,66 +572,63 @@ 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, capturing multiple security results in cipher suite parameters. 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 3.8. + information, in accordance with Section 3.7. 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. -3.6. Block Confidentiality Block +3.5. Block Confidentiality Block A BCB is an ASB with the following additional restrictions: - The block-type code value MUST be 0x04. + The block-type code value MUST be 0x03. The block processing control flags value can be set to whatever values are required by local policy, except that a Lone BCB or First BCB MUST have the "replicate in every fragment" flag set. This indicates to a receiving node that the payload portion in - each fragment represents cipher-tex - - t. This flag SHOULD NOT be set otherwise. 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. + each fragment represents cipher-text. This flag SHOULD NOT be set + otherwise. 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. - The security-target MUST uniquely identify a block within the - bundle. The security-target for a BCB MAY reference the payload - block, a non-security extension block, or a BIB block. The - reserved type 0x01 specifies the singleton payload block. + The security-target MUST match the BLock Number of a block within + the bundle. The security-target for a BCB MAY reference the + payload block, a non-security extension block, or a BIB block. The cipher suite ID MUST be documented as a confidentiality cipher suite. Key-information, if available, MUST appear only in a Lone BCB or a First BCB. 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 3.9) in the + in an "integrity check value" field (see Section 3.8) in the security-result of the Lone BCB or Last BCB. The cipher suite parameters field MAY be present in either a Lone BCB or a First BCB. This field MUST NOT be present in a Last BCB. An EID-reference to the security-source MAY be present in either a Lone BCB or a First BCB. This field MUST NOT be present in a Last BCB. The security-source can also be specified as part of key- - information described in Section 3.9. + information described in Section 3.8. The security-result MAY be present in either a Lone BCB or a Last BCB. This field MUST NOT be present in a First BCB. This compound field normally contains fields such as an encrypted bundle encryption key and/or authentication tag. The BCB is the only security block that 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 @@ -835,21 +636,21 @@ and length) remain unmodified. 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 3.9) of the BCB. This "in- + in the security-result field (see Section 3.8) of the BCB. This "in- place" encryption allows fragmentation, reassembly, and custody transfer to operate without knowledge of whether or not encryption has occurred. Notes: 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 @@ -858,28 +659,28 @@ 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 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. -3.7. Cryptographic Message Syntax Block +3.6. Cryptographic Message Syntax Block A CMSB is an ASB with the following additional restrictions: - The block-type code value MUST be 0x05. + The block-type code value MUST be 0x04. The content of the block must contain valid CMS data, as defined - in RFC 5652, and encoded in X.690 BER or DER encoding. + in [RFC5652] , and encoded in X.690 BER or DER encoding. The block processing control flags value can be set to whatever values are required by local policy. This flag SHOULD NOT be set otherwise. 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. The security-target MUST uniquely identify a block within the bundle. The reserved block type 0x01 specifies the singleton payload block. @@ -908,26 +709,26 @@ Multiple CMS operations may be nested within a single CMSB block to allow more than one security operation to be performed upon a security-target. CMS Operations can be considered to have BPSec parallels: CMSB Enveloped-Data content type SHALL be considered as equivalent to a BPSec BCB block, and a CMSB Signed-Data type SHALL be considered as equivalent to a BPSec BIB block. -3.8. Block Interactions +3.7. Block Interactions - The four 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. + 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. o If confidentiality is to be applied to a target, it MUST also be applied to every integrity operation already defined for that @@ -943,63 +744,56 @@ 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 3.6, a BIB MUST NOT have a BCB as its + o As mentioned in Section 3.5, a BIB MUST NOT have a BCB as its security target. BCBs may embed integrity results as part of cipher suite parameters. o As mentioned in Section 4.4, CMS operations are considered to have operational parallels. When a CMSB is used, these parallels MUST be considered for block interactions (e.g., a Signed-Data structure MUST NOT be evaluated if the security-target of the operation is also the security-target of a BCB) o If a single bundle is going to contain a CMSB as well as other security blocks, the CMS operations MUST be performed and the CMSB MUST be created before any other security operation is applied. - o On reception of a bundle containing a CMSB and other security - blocks, the CMSB must be decoded last. - Additionally, since the CMSB block may contain either integrity or confidentiality information in its encapsulated CMS, there is no way to evaluate conflicts when a BIB/BCB and a CMSB have the same security target. To address this concern, the following processing rules MUST be followed. o If an extension block is the target of a BIB or a BCB, then the extension block MUST NOT also be the target of a CMSB, and vice- versa. - o If a bundle is the target of a BAB block, then the bundle MUST NOT - also be the target of a CMSB, and vice-versa. - o Generally, a CMSB MUST be processed before any BIB or BCB blocks are processed. 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, and BABs - MUST be added after all other security blocks. 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. + 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. -3.9. Parameters and Result Fields +3.8. Parameters and Result Fields 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. 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 SDNV-encoded integer. Value is the data content of the item. @@ -1043,90 +837,85 @@ | | (ICV) / | the destination to verify that the | | | Authentication | protected data has not been modified. | | | Tag | This value MAY contain padding if | | | | required by the cipher suite. | +-------+----------------+------------------------------------------+ | 9-255 | Reserved | | +-------+----------------+------------------------------------------+ Table 1 -3.10. BSP Block Example +3.9. 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. Block in Bundle ID +=================================+====+ | Primary Block | B1 | +---------------------------------+----+ - | First BAB | B2 | - | OP(authentication, Bundle) | | - +---------------------------------+----+ - | Lone BIB | B3 | + | Lone BIB | B2 | | OP(integrity, target=B1) | | +---------------------------------+----+ - | Lone BCB | B4 | - | OP(confidentiality, target=B5) | | - +---------------------------------+----+ - | Extension Block | B5 | - +---------------------------------+----+ - | Lone BIB | B6 | - | OP(integrity, target=B7) | | + | Lone BCB | B3 | + | OP(confidentiality, target=B4) | | +---------------------------------+----+ - | Extension Block | B7 | + | Extension Block | B4 | +---------------------------------+----+ - | Lone BCB | B8 | - | OP(confidentiality, target=B9) | | + | Lone BIB | B5 | + | OP(integrity, target=B6) | | +---------------------------------+----+ - | Lone BIB (encrypted by B8) | B9 | - | OP(integrity, target=B11) | | + | Extension Block | B6 | +---------------------------------+----+ - | Lone BCB |B10 | - | OP(confidentiality, target=B11) | | + | Lone BCB | B7 | + | OP(confidentiality, target=B8) | | +---------------------------------+----+ - | Payload Block |B11 | + | Lone BIB (encrypted by B7) | B8 | + | OP(integrity, target=B10) | | + +---------------------------------+----| + | Lone BCB | B9 | + | OP(confidentiality, target=B10) | | +---------------------------------+----+ - | Last BAB |B12 | - | OP(authentication, Bundle) | | + | Payload Block |B10 | +---------------------------------+----+ Figure 4: Sample Use of BSP Blocks - In this example a bundle has four non-security-related blocks: the - primary block (B1), two extension blocks (B5,B7), and a payload block - (B11). The following security applications are applied to this + In this example a bundle has five non-security-related blocks: the + primary block (B1), three extension blocks (B4,B6,B9), and a payload + block (B11). The following security applications are applied to this bundle. - o Authentication over the bundle. This is accomplished by two BAB - blocks: B2 and B12. - o An integrity signature applied to the canonicalized primary block. - This is accomplished by a single BIB, B3. + This is accomplished by a single BIB (B2). - o Confidentiality for the first extension block. This is - accomplished by a single BCB block, B4. + o Confidentiality for the first extension block (B4). This is + accomplished by a single BCB block (B3). - o Integrity for the second extension block. This is accomplished by - a single BIB block, B6. + o Integrity for the second extension block (B6). This is + accomplished by a single 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. - o An integrity signature on the payload. This is accomplished by a - single BIB block, B9. + o An integrity signature on the payload (B10). This is accomplished + by a single BIB block (B8). o Confidentiality for the payload block and it's integrity - signature. This is accomplished by two Lone BCB blocks: B8 - encrypting B9, and B10 encrypting B11. + signature. This is accomplished by two Lone BCB blocks: B7 + encrypting B8, and B9 encrypting B10. Block in Bundle ID +=========================================+====+ | Primary Block | B1 | +-----------------------------------------+----+ | First BAB | B2 | | OP(authentication, Bundle) | | +-----------------------------------------+----+ | Lone CMSB | B3 | | security-target=0x01 | | @@ -1168,89 +957,39 @@ security-result field. The payload block's data is subsequently removed now that the original data has been encoded within the CMSB block. 4. Security Processing This section describes the security aspects of bundle processing. 4.1. Canonical Forms - In order to verify a signature of a bundle, the exact same bits, in + In order to verify a signature of a block, the exact same bits, in the exact same order, MUST be input to the calculation upon verification as were input upon initial computation of the original - signature value. Consequently, a node MUST NOT change the encoding - of any URI [RFC3986] in the dictionary field, e.g., changing the DNS - part of some HTTP URL from lower case to upper case. Because bundles - MAY be modified while in transit (either correctly or due to - implementation errors), canonical forms of security-targets MUST be - defined. + signature value. Many fields in various blocks are stored as variable-length SDNVs. These are canonicalized into an "unpacked form" as eight-byte fixed- - width fields in network byte order. The size of eight bytes is - chosen because implementations MAY handle larger SDNV values as - invalid, as noted in [RFC5050]. - -4.1.1. Bundle Canonicalization - - Bundle canonicalization permits no changes at all to the bundle - between the security-source and the destination, with the exception - of one of the Block Processing Control Flags, as described below. It - is intended for use in BAB cipher suites. This algorithm - conceptually catenates all blocks in the order presented, but omits - all security-result data fields in security blocks having the bundle - as their security-target. For example, when a BAB cipher suite - specifies this algorithm, we omit the BAB security-result from the - catenation. The inclusion of security-result length fields is as - determined by the specified cipher suite. A security-result length - field MAY be present even when the corresponding security-result data - fields are omitted. - - Notes: - - o In the Block Processing Control Flags field the unpacked SDNV is - ANDed with mask 0xFFFF FFFF FFFF FFDF to zero the flag at bit 5 - ("Block was forwarded without being processed"). If this flag is - not zeroed out, then a bundle passing through a non-security aware - node will set this flag which will change the message digest and - the BAB block will fail to verify. - - o In the above, we specify that security-result data is omitted. - This means that no bytes of the security-result data are input. - - If the security-result length is included in the catenation, we - assume that the security-result length will be known to the module - that implements the cipher suite before the security-result is - calculated, and require that this value be in the security-result - length field even though the security-result data itself will be - omitted. - - o The 'res' bit of the cipher suite ID, which indicates whether or - not the security-result length and security-result data field are - present, is part of the canonical form. - - o The value of the block data length field, which indicates the - length of the block, is also part of the canonical form. Its - value indicates the length of the entire block when the block - includes the security-result data field. + width fields in network byte order. -4.1.2. Block Canonicalization +4.1.1. Block Canonicalization This algorithm protects those parts of a block that SHOULD NOT be changed in transit. There are three types of blocks that may undergo block canonicalization: the primary block, the payload block, or an extension block. -4.1.2.1. Primary Block Canonicalization +4.1.1.1. Primary Block Canonicalization The canonical form of the primary block is shown in Figure 6. Essentially, it de-references the dictionary block, adjusts lengths where necessary, and ignores flags that may change in transit. +----------------+----------------+----------------+----------------+ | Version | Processing flags (incl. COS and SRR) | +----------------+----------------+---------------------------------+ | Canonical primary block length | +----------------+----------------+---------------------------------+ @@ -1303,38 +1042,38 @@ o The unpacked SDNVs for the creation timestamp and lifetime are copied from the primary block. o Fragment offset and total application data unit length are ignored, as is the case for the "bundle is a fragment" bit mentioned above. If the payload data to be canonicalized is less than the complete, original bundle payload, the offset and length are specified in the cipher suite parameters. -4.1.2.2. Payload Block Canonicalization +4.1.1.2. Payload Block Canonicalization When canonicalizing the payload block, the block processing control flags value used for canonicalization is the unpacked SDNV value with reserved and mutable bits masked to zero. The unpacked value is ANDed with mask 0x0000 0000 0000 0077 to zero reserved bits and the "last block" bit. The "last block" bit is ignored because BABs and other security blocks MAY be added for some parts of the journey but not others, so the setting of this bit might change from hop to hop. Payload blocks are canonicalized as-is, with the exception that, in some instances, only a portion of the payload data is to be protected. 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 payload is protected, as discussed further below. -4.1.2.3. Extension Block Canonicalization +4.1.1.3. Extension Block Canonicalization When canonicalizing an extension block, the block processing control flags value used for canonicalization is the unpacked SDNV value with reserved and mutable bits masked to zero. The unpacked value is ANDed with mask 0x0000 0000 0000 0057 to zero reserved bits, the "last block" flag and the "Block was forwarded without being processed" bit. The "last block" flag is ignored because BABs and other security blocks MAY be added for some parts of the journey but not others, so the setting of this bit might change from hop to hop. @@ -1353,46 +1092,31 @@ terminator is used in EID canonicalization, a separator token MUST be used to determine when one EID ends and another begins. When multiple EIDs are canonicalized together, the character "," SHALL be placed between adjacent instances of EID text. The block-length is canonicalized as its unpacked SDNV value. If the data to be canonicalized is less than the complete, original block data, this field contains the size of the data being canonicalized (the "effective block") rather than the actual size of the block. -4.1.3. Considerations +4.1.2. Considerations o The canonical forms for the bundle and various extension blocks is not transmitted. It is simply an artifact used as input to digesting. o We omit the reserved flags because we cannot determine if they will change in transit. The masks specified above will have to be revised if additional flags are defined and they need to be protected. - o Our URI encoding does not preserve the null-termination convention - from the dictionary field, nor do we canonicalize the scheme and - scheme-specific part (SSP) separately. Instead, the byte array < - scheme name > : < scheme-specific part (SSP)> is used in the - canonicalization. - - o The URI encoding will cause errors if any node rewrites the - dictionary content (e.g., changing the DNS part of an HTTP URL - from lower case to upper case). This could happen transparently - when a bundle is synched to disk using one set of software and - then read from disk and forwarded by a second set of software. - Because there are no general rules for canonicalizing URIs (or - IRIs), this problem may be an unavoidable source of integrity - failures. - o All SDNV fields here are canonicalized as eight-byte unpacked values in network byte order. Length fields are canonicalized as four-byte values in network byte order. Encoding does not need optimization since the values are never sent over the network. 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 Cipher suites MAY define their own canonicalization algorithms and @@ -1409,75 +1133,43 @@ Similarly, confidentiality requirements MAY also apply to other parts of the primary block (e.g., the current-custodian), and that is supported in the same manner. 4.3. Bundles Received from Other Nodes Security blocks MUST be processed in a specific order when received by a security-aware node. The processing order is as follows. - o All BAB blocks in the bundle MUST be evaluated prior to evaluating - any other block in the bundle. - o All BCB blocks in the bundle MUST be evaluated prior to evaluating any BIBs in the bundle. When BIBs and BCBs share a security- target, BCBs MUST be evaluated first and BIBs second. -4.3.1. Receiving BAB Blocks - - Nodes implementing this specification SHALL consult their security - policy to determine whether or not a received bundle is required by - policy to include a BAB. - - If the bundle is not required to have a BAB then BAB processing on - the received bundle is complete, and the bundle is ready to be - further processed for BIB/BCB handling or delivery or forwarding. - Security policy may provide a means to override this default behavior - and require processing of a BAB if it exists. - - If the bundle is required to have a BAB but does not, then the bundle - MUST be discarded and processed no further. If the bundle is - required to have a BAB but the key information for the security- - source cannot be determined or the security-result value check fails, - then the bundle has failed to authenticate, and the bundle MUST be - discarded and processed no further. - - If the bundle is required to have a BAB, and a BAB exists, and the - BAB information is verified, then the BAB processing on the received - bundle is complete, and the bundle is ready to be further processed - for BIB/BCB handling or delivery or forwarding. - - A BAB received in a bundle MUST be stripped before the bundle is - forwarded. A new BAB MAY be added as required by policy. This MAY - require correcting the "last block" field of the to-be-forwarded - bundle. - -4.3.2. Receiving BCB Blocks +4.3.1. Receiving BCB Blocks If the bundle has a BCB and the receiving node is the destination for the bundle, the node MUST decrypt the relevant parts of the security- target in accordance with the cipher suite specification. If the relevant parts of an encrypted payload cannot be decrypted (i.e., the decryption key cannot be deduced or decryption fails), then the bundle MUST be discarded and processed no further; in this - case, a bundle deletion status report (see [RFC5050]) indicating the + case, a bundle deletion status report (see [BPBIS]) indicating the decryption failure MAY be generated. If any other encrypted security-target cannot be decrypted then the associated security- target and all security blocks associated with that target MUST be discarded and processed no further. When a BCB is decrypted, the recovered plain-text MUST replace the cipher-text in the security-target body data -4.3.3. Receiving BIB Blocks +4.3.2. Receiving BIB Blocks 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 @@ -1502,61 +1194,54 @@ 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. 4.4. Receiving CMSB Blocks A CMSB MUST NOT be processed if its security target is also the - security target of any BAB, BIB, or BCB in the bundle. + security target of any BIB or BCB in the bundle. The security services provided by a CMSB will be considered successful if all services in the CMSB are validated. If any one service encapsulated in the CMSB fails to validate, then the CMSB MUST be considered as having failed to validate and MUST be dispositioned in accordance with security policy. 4.5. 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 [RFC5050] 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. - In addition, the following security-specific processing is REQUIRED: + 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. In + addition, the following security-specific processing is REQUIRED: o Due to the complexity of bundle fragmentation, including the possibility of fragmenting bundle fragments, integrity and confidentiality operations are not to be applied to a bundle fragment. 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. o The authentication security policy requirements for a bundle MUST be applied individually to all the bundles resulting from a fragmentation event. - o A BAB cipher suite MAY specify that it only applies to non- - fragmented bundles and not to bundle fragments. - o The decision to fragment a bundle MUST be made prior to adding authentication to the bundle. The bundle MUST first be fragmented and authentication applied to each individual fragment. - o If a bundle with a BAB is fragmented by a non-security-aware node, - then the entire bundle must be re-assembled before being processed - to allow for the proper verification of the BAB. - 4.6. Reactive Fragmentation When a partial bundle has been received, the receiving node SHALL consult its security policy to determine if it MAY fragment the bundle, converting the received portion into a bundle fragment for further forwarding. Whether or not reactive fragmentation is permitted SHALL depend on the security policy and the cipher suite used to calculate the BAB authentication information, if required. Specifically, if the security policy does not require authentication, @@ -1626,42 +1311,42 @@ generated and added to the BCB for the security-target as additional information in the security-result field. Second, the encrypted block may be replicated as a new block and integrity signed. Third, 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. Conformance - All implementations are strongly RECOMMENDED to provide at least a - BAB cipher suite. A relay node, for example, might not deal with - end-to-end confidentiality and data integrity, but it SHOULD exclude - unauthorized traffic and perform hop-by-hop bundle verification. + 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. 9. IANA Considerations This protocol has fields that have been registered by IANA. 9.1. Bundle Block Types This specification allocates three 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 | Bundle Authentication Block | This document | - | 3 | Block Integrity Block | This document | - | 4 | Block Confidentiality Block | This document | + | 2 | Block Integrity Block | This document | + | 3 | Block Confidentiality Block | This document | + | 4 | CMS Block | This document | +-------+-----------------------------+---------------+ Table 2 9.2. 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 @@ -1715,47 +1401,39 @@ | 192-250 | private use | This document | | 251-255 | reserved | This document | +---------+---------------------------------+---------------+ Table 4 10. References 10.1. Normative References + [BPBIS] Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol", + draft-ietf-dtn-bpbis-03 (work in progress), March 2016. + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. - [RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol - Specification", RFC 5050, November 2007. - [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009, . [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol IANA Registries", RFC 6255, May 2011. 10.2. Informative References - [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform - Resource Identifier (URI): Generic Syntax", STD 66, - RFC 3986, January 2005. - [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. - [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet - Mail Extensions (S/MIME) Version 3.2 Message - Specification", RFC 5751, January 2010. - [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 2015. Appendix A. Acknowledgements