--- 1/draft-ietf-dtn-bpsec-02.txt 2016-10-30 16:15:57.309429296 -0700 +++ 2/draft-ietf-dtn-bpsec-03.txt 2016-10-30 16:15:57.381431078 -0700 @@ -1,18 +1,18 @@ Delay-Tolerant Networking E. Birrane Internet-Draft K. McKeever -Intended status: Experimental JHU/APL -Expires: January 7, 2017 July 6, 2016 +Intended status: Standards Track JHU/APL +Expires: May 3, 2017 October 30, 2016 Bundle Protocol Security Specification - draft-ietf-dtn-bpsec-02 + draft-ietf-dtn-bpsec-03 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. @@ -20,21 +20,21 @@ 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 January 7, 2017. + This Internet-Draft will expire on May 3, 2017. Copyright Notice 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 @@ -57,52 +57,52 @@ 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. Multi-Target Block Definitions . . . . . . . . . . . . . 17 - 3.7. Parameters and Result Fields . . . . . . . . . . . . . . 17 - 3.8. BSP Block Example . . . . . . . . . . . . . . . . . . . . 18 + 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. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 31 - 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 - 11.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 31 - 11.2. Cipher Suite Flags . . . . . . . . . . . . . . . . . . . 31 - 11.3. Parameters and Results . . . . . . . . . . . . . . . . . 32 - 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 - 12.1. Normative References . . . . . . . . . . . . . . . . . . 33 - 12.2. Informative References . . . . . . . . . . . . . . . . . 33 - Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 34 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34 + 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 + 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 + 13.1. Normative References . . . . . . . . . . . . . . . . . . 34 + 13.2. Informative References . . . . . . . . . . . . . . . . . 34 + 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. 1.1. Motivation The Bundle Protocol is used in DTNs that overlay multiple networks, @@ -260,36 +260,36 @@ 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). The following security-specific terminology is also defined to clarify security operations in this specifiation. - o Security-Service - the security features supported by this + 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 + 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 + 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. + 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. 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 @@ -312,56 +312,56 @@ 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. + security operation. 2.2. Multiple Security Sources A bundle MAY have multiple security blocks and these blocks MAY have - different security-sources. + 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 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 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 + 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 + the security source for that block even though BN1 remains the bundle source. 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 + 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 will be treated appropriately by non-security-aware nodes. @@ -389,57 +389,65 @@ 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 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). - The BIB is used to ensure the integrity of its security-target(s). + 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 + 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(s) has been encrypted, - in whole or in part, at the BCB security-source in order to + 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. - A security-operation MUST NOT be applied more than once in a bundle. - For example, the two security-operations: OP(integrity, payload) and + 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. - If the same security-service is to be applied to multiple security- + 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 + 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. 3.1. Block Identification 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 + a bundle. Within this specification, a security target will be identified by its unique Block Number. + 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. + 3.2. 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 @@ -474,28 +482,28 @@ | 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- + 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. + 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. Bit Bit Bit Bit Bit Bit Bit Bit @@ -504,114 +512,116 @@ | reserved | src |parm | +-----------------------------------+-----+-----+ MSB LSB Figure 3: Cipher Suite Flags Where: * bits 7-2 are reserved for future use. - * src - bit 1 indicates whether the Security Source EID is - present in the block. + * src - bit 1 indicates whether the Security Source is present in + the block. * parm - bit 0 indicates whether or not the Cipher Suite Parameters field is present in the block. - o (OPTIONAL) Security Source (URI) - This identifies the EID that + 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 souce of the block MAY be taken to - be the bundle source, the previous hop, or some other EID as - defined by security policy. + 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. o (OPTIONAL) Parameters (Byte Array) - Compound field of the following two items. * Length (Unsigned Integer) - specifies the length of the next field, which captures the parameters data. * 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. + Type (Byte) - The parameter type. + Length (Unsigned Integer) - The length of the parameter. + Value (Byte Array) - The parameter value. - See Section 3.7 for a list of parameter types that MUST be + 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. - o Security Result (Byte Array) - Compound field of the next two - items. + 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. - * Length (Unsigned Integer) - specifies the length of the next - field, which is the security-result data. + * Total Length (Unsigned Integer) - specifies the length, in + bytes, of the remaining security result information. - * Data (Byte Array) - A byte array encoding a security result for - each security-target covered by the security-block, with each - entry represented as a TLV and optionally prepended with - information on which security-target is referenced by the - result, as follows. + * 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. - + 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 (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. - + Type (Unsigned Integer)(Byte) - The type of security result - field. + + Type (Unsigned Integer) - The type of security result field. + Length (Unsigned Integer) - The length of the result field. - + Value (Byte Array) - The results of the appropriate cipher - suite specific calculation (e.g., a signature, Message - Authentication Code (MAC), or cipher-text block key). + + Value (Byte Array) - The results of the cipher suite + specific calculation. 3.3. Block Integrity Block A BIB is an ASB with the following characteristics: 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. - A security-target for a BIB MUST NOT reference a security-block + A security target for a BIB 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 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 - field is not present, then the security-source of the block SHOULD + 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 3.7. + 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 + 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 + parts of the security target, as specified in the cipher suite definition. This field MUST be present. - The cipher suite MAY process less than the entire security-target. + 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. + security target, the cipher suite parameters MUST specify which + bytes of the security target are protected. Notes: 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 @@ -632,147 +642,130 @@ 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. - A security-target for a BCB MAY reference the payload block, a - non-security extension block, or a BIB block. A security-target + 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 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 3.7) or other - such appropriate area in the security-result of the BCB. + 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. - An EID-reference to the security-source MAY be present. If this - field is not present, then the security-source of the block SHOULD + 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 3.7. + 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 + 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. - 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 + 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. 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, + 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 3.7) of the BCB. This "in- + 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. 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 + 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 + 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. 3.5. Block Interactions - The security-block types defined in this specification are designed + 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 + 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 + 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 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 + 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 - and a BCB for a given security-target. + and a BCB for a given security target. 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 + 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 security target. BCBs may embed integrity results as part of cipher suite parameters. 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 + 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. Multi-Target Block Definitions - - A security-block MAY target multiple security-targets if and only if - all cipher suite parameters, security source, and key information are - common for each security operation. The following processing - directives apply for these multi-target blocks. - - o If a security-block has more than one security-target, then each - type identifier in the security result TLV MUST be interpretted as - a tuple with the first entry being the security-target for which - the security result applies and the second entry being the type - value enumeration of the security result value. - - o If the security-block has a single security-target, the type field - of every entry in the security result array MUST simply be the - type field and MUST NOT be a tuple as described above. - -3.7. Parameters and Result Fields +3.6. 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 + 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 Unsigned Integer. Value is the data content of the item. Item types, name, and descriptions are defined as follows. @@ -799,22 +792,22 @@ | 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 | | | | | original bundle, even if | | | | | the current bundle is a | | | | | fragment. | | +-------+----------------+-----------------------------+------------+ - | 5 | Integrity | Result of BAB or BIB digest | Security | - | | Signatures | or other signing operation. | Results | + | 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 | | @@ -823,27 +816,27 @@ | | | data has not been modified. | | | | | This value MAY contain | | | | | padding if required by the | | | | | cipher suite. | | +-------+----------------+-----------------------------+------------+ | 9-255 | Reserved | | | +-------+----------------+-----------------------------+------------+ Table 1 -3.8. BSP Block Example +3.7. 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 + 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 | +-----------------------------------+----+ | BIB | B2 | | OP(integrity, target=B1) | | +-----------------------------------+----+ @@ -1023,171 +1016,171 @@ 5. Security Processing This section describes the security aspects of bundle processing. 5.1. 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 BCB blocks in the bundle MUST be evaluated prior to evaluating - any BIBs in the bundle. When BIBs and BCBs share a security- + any BIBs in the bundle. When BIBs and BCBs share a security target, BCBs MUST be evaluated first and BIBs second. 5.1.1. Receiving BCB Blocks 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 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 + 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 body data - If a BCB contains multiple security-targets, all security-targets + 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 - represented by an individual BCB with a single security-target. + this is to be the same 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. - 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 + 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 + 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 + 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 + 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 + 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 + 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 + 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 + 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. + 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 BIB contains multiple security-targets, all security-targets + 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. + this is to be the same 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. 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 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. + 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. 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. 7. 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. - o If a bundle is received that contains more than one security- + 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. + 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 + 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- + 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- + 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. - o Adding a BIB to a security-target that has already been encrypted + 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. + add an integrity signature to an encrypted security target. 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. + 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 + 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 @@ -1264,21 +1257,21 @@ from one of the endpoints. 8.2. Attacker Behaviors and BPSec Mitigations 8.2.1. Eavesdropping Attacks Once Mallory has received a bundle, she is able to examine the contents of that bundle and attempt to recover any protected data or cryptographic keying material from the blocks contained within. The protection mechanism that BPSec provides against this action is the - BCB, which encrypts the contents of its security-target, providing + BCB, which encrypts the contents of its security target, providing confidentiality of the data. Of course, it should be assumed that Mallory is able to attempt offline recovery of encrypted data, so the cryptographic mechanisms selected to protect the data should provide a suitable level of protection. When evaluating the risk of eavesdropping attacks, it is important to consider the lifetime of bundles on a DTN. Depending on the network, bundles may persist for days or even years. If a bundle does persist on the network for years and the cipher suite used for a BCB provides inadequate protection, Mallory may be able to recover the protected @@ -1290,56 +1283,56 @@ 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 mechansims 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 + 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 - removes a BCB block, but keeps the security-target, the security- + removes a BCB block, but keeps the security target, the security target remains encrypted and there is a possibility that there may no longer be sufficient information to decrypt the block at its - destination. If Mallory removes both a BCB (or BIB) and its - security-target there is no evidence left in the bundle of the - security operation. Similarly, if Mallory removes the BIB but not - the security-target there is no evidence left in the bundle of the + destination. If Mallory removes both a BCB (or BIB) and its security + target there is no evidence left in the bundle of the security + operation. Similarly, if Mallory removes the BIB but not the + security target there is no evidence left in the bundle of the security operation. In each of these cases, the implementation of BPSec MUST be combined with policy configuration at endpoints in the network which describe the expected and required security operations that must be applied on transmission and are expected to be present on receipt. This or other similar out-of-band information is required to correct for removal of security information in the bundle. A limitation of the BIB may exist within the implementation of BIB validation at the destination node. If Mallory is a legitimate node within the DTN, the BIB generated by Alice with K_A can be replaced with a new BIB generated with K_M and forwarded to Bob. If Bob is only validating that the BIB was generated by a legitimate user, Bob will acknowledge the message as originating from Mallory instead of Alice. In order to provide verifiable integrity checks, both a BIB and BCB should be used. Alice creates a BIB with the protected data - block as the security-target and then creates a BCB with both the BIB - and protected data block as its security-targets. In this + block as the security target and then creates a BCB with both the BIB + and protected data block as its security targets. In this configuration, since Mallory is only a legitimate node and does not have access to Alice's key K_A, Mallory is unable to decrypt the BCB and replace the BIB. 8.2.3. Topology Attacks If Mallory is in a MITM position within the DTN, she is able to influence how any bundles that come to her may pass through the network. Upon receiving and processing a bundle that must be routed elsewhere in the network, Mallory has three options as to how to @@ -1408,48 +1401,98 @@ 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. -10. Conformance +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 + 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. + + o An OSB definition MAY NOT require any behavior of a BPSEC-BPA that + is in conflict with the behavior identified in this specification. + In particular, the security processing requirements imposed by + this specification MUST be consistent across all BPSEC-BPAs in a + network. + + o The behavior of an OSB when dealing with fragmentation MUST be + specified and MUST NOT lead to ambiguous processing states. In + particular, an OSB definition should address how to receive and + process an OSB in a bundle fragment that may or may not also + contain its security target. An OSB definition should also + address whether an OSB may be added to a bundle marked as a + fragment. + + Additionally, policy considerations for the management, monitoring, + and configuration associated with blocks SHOULD be included in any + OSB definition. + + NOTE: The burden of showing compliance with processing rules is + placed upon the standards defining new security blocks and the + identification of such blocks shall not, alone, require maintenance + of this specification. + +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. -11. IANA Considerations +12. IANA Considerations This protocol has fields that have been registered by IANA. -11.1. Bundle Block Types +12.1. 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 | Block Integrity Block | This document | | 3 | Block Confidentiality Block | This document | +-------+-----------------------------+---------------+ Table 2 -11.2. Cipher Suite Flags +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: +--------------------------+-------------------------+--------------+ @@ -1461,72 +1504,72 @@ | 1 | Block Contains | This | | | parameters | document | | 2 | Source EID ref present | This | | | | document | | >3 | Reserved | This | | | | document | +--------------------------+-------------------------+--------------+ Table 3 -11.3. Parameters and Results +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 3.7 | - | 1 | initialization vector (IV) | Section 3.7 | - | 2 | reserved | Section 3.7 | - | 3 | key-information | Section 3.7 | - | 4 | content-range (pair of Unsigned Integers) | Section 3.7 | - | 5 | integrity signature | Section 3.7 | - | 6 | unassigned | Section 3.7 | - | 7 | salt | Section 3.7 | - | 8 | BCB integrity check value (ICV) | Section 3.7 | - | 9-191 | reserved | Section 3.7 | - | 192-250 | private use | Section 3.7 | - | 251-255 | reserved | Section 3.7 | + | 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 -12. References +13. References -12.1. Normative 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. [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. -12.2. Informative References +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.