One document matched: draft-irtf-dtnrg-sbsp-01.xml
<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM 'rfc2629.dtd' [
<!ENTITY RFC4838 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4838.xml">
<!ENTITY RFC5050 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5050.xml">
<!ENTITY RFC6257 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6257.xml">
<!ENTITY RFC2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">
<!ENTITY RFC6255 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6255.xml">
<!ENTITY RFC3986 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3986.xml">
<!ENTITY RFC5751 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5751.xml">
]>
<?rfc toc="yes"?> <!-- generate a table of contents -->
<?rfc symrefs="yes"?> <!-- use anchors instead of numbers for references -->
<?rfc sortrefs="yes" ?> <!-- alphabetize the references -->
<?rfc compact="yes" ?> <!-- conserve vertical whitespace -->
<?rfc subcompact="no" ?> <!-- but keep a blank line between list items -->
<rfc category="exp" ipr="trust200902" docName='draft-irtf-dtnrg-sbsp-01'>
<front>
<title>
Streamlined Bundle Security Protocol Specification
</title>
<author initials='E.J.'
surname='Birrane'
fullname='Edward J. Birrane, III'>
<organization abbrev='JHU/APL'>
The Johns Hopkins University Applied Physics Laboratory
</organization>
<address>
<postal>
<street>11100 Johns Hopkins Rd.</street>
<city>Laurel</city>
<region>MD</region>
<code>20723</code>
<country>US</country>
</postal>
<phone>+1 443 778 7423</phone>
<email>Edward.Birrane@jhuapl.edu</email>
</address>
</author>
<date month='May' year='2014'/>
<!-- Meta-data -->
<area>General</area>
<workgroup>Delay-Tolerant Networking Research Group</workgroup>
<keyword>security</keyword>
<keyword>bundle</keyword>
<keyword>integrity</keyword>
<keyword>authentication</keyword>
<keyword>confidentiality</keyword>
<abstract>
<t>
This document defines a streamlined bundle security protocol, which provides
data authentication, integrity, and confidentiality services for the Bundle Protocol.
Capabilities are provided to protect the bundle payload, and additional data that
may be included within the bundle, along a single path through a network.
</t>
</abstract>
</front>
<middle>
<section anchor='intro' title='Introduction'>
<t>
This document defines security features for the Bundle Protocol <xref target="RFC5050"/>
intended for use in delay-tolerant networks, in order to provide Delay-Tolerant
Networking (DTN) security services.
</t>
<t>
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.
</t>
<t>
The stressed environment of
the underlying networks over which the Bundle Protocol operates makes it
important for the DTN to be protected from unauthorized use, and this stressed
environment poses unique challenges for the mechanisms needed to secure the Bundle
Protocol. Furthermore, DTNs may be deployed in environments where a
portion of the network might become compromised, posing the usual security challenges
related to confidentiality, integrity, and availability.
</t>
<t>
This document describes the Streamlined Bundle Security Protocol (SBSP), which provides
security services for blocks within a bundle from the bundle source to the bundle
destination. Specifically, the SBSP provides authentication, integrity, and
confidentiality for bundles along a path through a DTN.
</t>
<t>
SBSP 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 SBSP. All nodes can interoperate with
the exception that SBSP security operations can only happen at SBSP security-aware nodes.
</t>
<section anchor="reldoc" title="Related Documents">
<t>
This document is best read and understood within the context of the following
other DTN documents:
</t>
<t>
"Delay-Tolerant Networking Architecture" <xref target='RFC4838'/> defines the architecture
for delay-tolerant networks, but does not discuss security at any length.
</t>
<t>
The DTN Bundle Protocol <xref target='RFC5050'/> defines the format and processing of the blocks
used to implement the Bundle Protocol, excluding the security-specific blocks defined here.
</t>
<t>
The Bundle Security Protocol <xref target='RFC6257'/> introduces the concepts
of security blocks for authentication, confidentiality, and integrity. The SBSP is based off of
this document.
</t>
</section>
<section anchor="term" title="Terminology">
<t>
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 <xref target='RFC2119'/>.
</t>
<t>
We introduce the following terminology for purposes of clarity.
<list style="symbols">
<t>Source - the bundle node from which a bundle originates. </t>
<t>Destination - the bundle node to which a bundle is ultimately destined. </t>
<t>Forwarder - the bundle node that forwarded the bundle on its most recent hop. </t>
<t>Intermediate Receiver, Waypoint, or "Next Hop" - the neighboring bundle node to which a forwarder forwards a bundle.</t>
<t>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.</t>
</list>
</t>
<t>
<xref target="bundle_example"/> below is adapted from <xref target='RFC5050'/> 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.
</t>
<figure anchor="bundle_example" title="Bundle Nodes Sit at the Application Layer of the Internet Model">
<artwork><![CDATA[
+---------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 --->|
| | | |
]]></artwork>
</figure>
<t>
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.
</t>
<t>
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).
</t>
<t>
We introduce the following security-specific DTN terminology.
<list style="symbols">
<t>Security-Service - the security features supported by
this specification: authentication, integrity, and
confidentiality.
</t>
<t>Security-Source - a bundle node that adds a security
block to a bundle.
</t>
<t>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.
</t>
<t>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.
</t>
<t>Security Block - a single instance of a SBSP extension
block in a bundle.
</t>
<t>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 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 MAY be implemented by one or more security blocks.
</t>
</list>
</t>
<t>
Referring to <xref target="bundle_example"/> again:
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
As required in <xref target="RFC5050"/>, 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.
</t>
<t>
If a node is not security-aware, then it forwards the security blocks
in the bundle unchanged unless the bundle's block processing flags
specify otherwise. If a network has some nodes that are not
security-aware, then the block processing flags SHOULD be set such
that security blocks are not discarded at those nodes solely because
they cannot be processed there. Except for this, the non-security-aware
nodes are transparent relay points and are invisible as far as security
processing is concerned.
</t>
</section>
</section>
<section anchor="blockdef" title="Security Block Definitions">
<t>
There are three types of security blocks that MAY be included in a
bundle. These are the Bundle Authentication Block (BAB), the Block
Integrity Block (BIB), and the Block Confidentiality Block (BCB).
<list>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
<t>
Certain cipher suites may allow or require multiple instances of a
block to appear in the bundle. For example, an authentication
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.
</t>
<t>
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.
</t>
<t>
Many of the fields in these block definitions use the Self-Delimiting Numeric Value
(SDNV) type whose format and encoding is as defined in <xref target='RFC5050'/>.
</t>
<section anchor="OP_ID" title="Block Identification">
<t>
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".
</t>
<t>
The definition of the extension block header from <xref target='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.
</t>
<t>
Figure 7 of <xref target='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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
If a node chooses to add an AEID to a target block header it MUST perform the following activities.
<list style="symbols">
<t>
The "Block contains an EID reference field" flag MUST be set for the target block, if
it is not already set.
</t>
<t>
The EID reference count for the block MUST be updated to reflect the addition of the AEID.
</t>
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
<t>
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 SBSP security operation applied to it.
</t>
<t>
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.
</t>
</section>
<section anchor="ASB" title="Abstract Security Block">
<t>
Each security block uses the Canonical Bundle
Block Format as defined in <xref target="RFC5050"/>.
That is, each security block is comprised of the following elements:
<list style='symbols'>
<t>Block Type Code</t>
<t>Block Processing Control Flags</t>
<t>Block EID Reference List (OPTIONAL)</t>
<t>Block Data Length</t>
<t>Block Type Specific Data Fields</t>
</list>
</t>
<t>
Since the three 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.
</t>
<t>
The structure of an Abstract Security Block is given in <xref target="asb"/>.
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.
</t>
<figure anchor="asb" title="Abstract Security Block Structure">
<artwork><![CDATA[
+-----------------------------+----------------------------------+
| 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) |
+-----------------------------+----------------------------------+
]]></artwork>
</figure>
<t>
An ASB consists of the following fields, some of which are
optional.
<list style="symbols">
<t>
Block-Type Code (Byte) - as described in <xref target="RFC5050"/>. The block-type
codes for security blocks are:
<list>
<t>BundleAuthenticationBlock - BAB: 0x02</t>
<t>BlockIntegrityBlock - BIB: 0x03</t>
<t>BlockConfidentialityBlock - BCB: 0x04</t>
</list>
</t>
<t>
Block Processing Control Flags (SDNV) - as described in
<xref target="RFC5050"/>. There are no general constraints on
the use of the block processing control flags, and some
specific requirements are discussed later.
</t>
<t>
(OPTIONAL) EID Reference Count and List - as described in
<xref target="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:
<list style="symbol">
<t>
(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.
</t>
<t>
(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 <xref target="OP_ID"/>.
</t>
</list>
</t>
<t>
Block Length (SDNV) - as described in <xref target="RFC5050"/>.
</t>
<t>
Block type specific data fields as follows:
<list style="symbols">
<t>
Security-Target (Compound) - Uniquely identifies the target of
the associated security-operation.
<vspace/><vspace/>
As discussed in <xref target="OP_ID"/> 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).
<vspace/><vspace/>
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.
</t>
<t>Cipher suite ID (SDNV)</t>
<t>Cipher suite flags (SDNV)</t>
<t>
(OPTIONAL) Cipher Suite Parameters - compound field of
the next two items.
<list style="symbols">
<t>
Cipher suite parameters length (SDNV) - specifies the
length of the next field, which is the cipher suite-parameters
data field.
</t>
<t>
Cipher suite parameters data - parameters to be
used with the cipher suite in use, e.g., a key
identifier or initialization vector (IV). See
<xref target="parmresult" /> 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.
</t>
</list>
</t>
<t>
(OPTIONAL) Security Result - compound field of the next
two items.
<list style="symbols">
<t>
Security result length (SDNV) - contains the length of
the next field, which is the security-result data field.
</t>
<t>
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).
</t>
</list>
</t>
</list>
</t>
</list>
</t>
<t>
The structure of the cipher suite flags field is shown
in <xref target="cs_flags"/>. 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 <xref target="RFC5050"/>, the description below numbers the bit positions
from the right rather than the standard RFC definition, which
numbers bits from the left.
<list>
<t> bits 6-3 are reserved for future use.</t>
<t> src - bit 2 indicates whether the EID-reference field of
the ASB contains the optional reference to the security-source.</t>
<t> parm - bit 1 indicates whether or not the
cipher suite parameters length and cipher suite parameters
data fields are present.</t>
<t> res - bit 0 indicates whether or not the ASB contains the
security-result length and security-result data fields.</t>
</list>
</t>
<figure anchor="cs_flags" title="Cipher Suite Flags">
<artwork><![CDATA[
Bit Bit Bit Bit Bit Bit Bit
6 5 4 3 2 1 0
+-----+-----+-----+-----+-----+-----+-----+
| reserved | src |parm | res |
+-----+-----+-----+-----+-----+-----+-----+
]]></artwork>
</figure>
</section>
<section anchor="enum" title="Block Ordering">
<t>
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.
</t>
<t>
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.
</t>
<t>
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 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.
</t>
<t>
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.
</t>
</section>
<section anchor="BAB" title="Bundle Authentication Block">
<t>
This section describes typical field values for the BAB, which
is solely used to implement OP(authentication, bundle).
<list>
<t>
The block-type code field value MUST be 0x02.
</t>
<t>
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.
</t>
<t>
The security-target MUST be the entire bundle,
which MUST be represented by a <block type><occurrence number>
of <0x00><0x00>.
</t>
<t>
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.
</t>
<t>
The cipher suite parameters field MAY be present, if so
specified in the cipher suite specification.
</t>
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
<t>
Notes:
<list style="symbols">
<t>
When multiple BAB blocks are used, the mandatory fields of
the Last BAB must match those of the First BAB.
</t>
<t>
The First BAB or Lone BAB, when present, SHOULD immediately
follow the primary block.
</t>
<t>
A Last BAB, when present, SHOULD be the last block in the bundle.
</t>
<t>
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.
</t>
</list>
</t>
</section>
<section anchor="BIB" title="Block Integrity Block">
<t>
A BIB is an ASB with the following additional restrictions:
<list>
<t>
The block-type code value MUST be 0x03.
</t>
<t>
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.
</t>
<t>
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).
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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 BIB.
</t>
<t>
The security-result captures
the result of applying the cipher suite calculation (e.g., the
MAC or signature) to the relevant parts of the
security-target, as specified in the cipher suite definition. This
field MUST be present in either a Lone BIB or a Last BIB. This field
MUST NOT be present in a First BIB.
</t>
<t>
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.
</t>
</list>
</t>
<t>
Notes:
<list style="symbols">
<t>
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.
</t>
<t>
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 <xref target="interact"/>.
</t>
<t>
The use of a generally available key is RECOMMENDED if custodial
transfer is employed and all nodes SHOULD verify the bundle before
accepting custody.
</t>
</list>
</t>
</section>
<section anchor="BCB" title="Block Confidentiality Block">
<t>
A BCB is an ASB with the following additional restrictions:
<list>
<t>
The block-type code value MUST be 0x04.
</t>
<t>
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-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.
</t>
<t>
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.
</t>
<t>
The cipher suite ID MUST be documented as a
confidentiality cipher suite.
</t>
<t>
Key-information, if available, MUST appear only in a Lone BCB or a First BCB.
</t>
<t>
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 <xref target="parmresult" />) in the security-result of
the Lone BCB or Last BCB.
</t>
<t>
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.
</t>
<t>
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 <xref target="parmresult" />.
</t>
<t>
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.
</t>
</list>
</t>
<t>
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 security-target block fields (such
as type, processing control flags, and length) remain unmodified.
</t>
<t>
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
<xref target="parmresult" />) of the BCB. This "in-place"
encryption allows fragmentation, reassembly, and custody transfer
to operate without knowledge of whether or not encryption has occurred.
</t>
<t>
Notes:
<list style="symbols">
<t>
The cipher suite MAY process less than the entire original
security-target body data. If the cipher suite processes less than the
complete, original security-target body data, the BCB for that security-target
MUST specify, as part of the cipher suite parameters, which bytes
of the body data are protected.
</t>
<t>
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.)
</t>
<t>
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.
</t>
</list>
</t>
</section>
<section anchor="interact" title="Block Interactions">
<t>
The three 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.
</t>
<t>
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.
</t>
<t>
<list style="symbols">
<t>
If confidentiality is to be applied to a target, it MUST also be applied to
every 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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
As mentioned in <xref target="BCB"/>, a BIB MUST NOT have a BCB as its security target. BCBs may embed integrity
results as part of cipher suite parameters.
</t>
</list>
</t>
<t>
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.
</t>
</section>
<section anchor="parmresult" title="Parameters and Result Fields">
<t>
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.
</t>
<t>
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.
</t>
<t>
Item types, name, and descriptions are defined as follows.
</t>
<texttable style="all" anchor="type_code_table">
<preamble>
Cipher suite parameters and result fields.
</preamble>
<ttcol align='center'> Type </ttcol>
<ttcol align='center'> Name </ttcol>
<ttcol align='left'> Description </ttcol>
<c>0</c>
<c>Reserved</c>
<c> </c>
<c>1</c>
<c>Initialization Vector (IV)</c>
<c> A random value, typically eight to sixteen bytes.</c>
<c>2</c>
<c>Reserved</c>
<c> </c>
<c>3</c>
<c>Key Information</c>
<c>Material encoded or protected by the key management system and used to transport
an ephemeral key protected by a long-term key.</c>
<c>4</c>
<c>Content Range</c>
<c>Pair of SDNV values (offset,length) specifying the range of payload bytes to which
an operation applies. The offset MUST be the offset within the original bundle, even if the
current bundle is a fragment.</c>
<c>5</c>
<c>Integrity Signatures</c>
<c>Result of BAB or BIB digest or other signing operation. </c>
<c>6</c>
<c>Unassigned</c>
<c> </c>
<c>7</c>
<c>Salt</c>
<c>An IV-like value used by certain confidentiality suites.</c>
<c>8</c>
<c>BCB Integrity Check Value (ICV) / Authentication Tag</c>
<c>Output from certain confidentiality cipher suite operations to be used at
the destination to verify that the protected data has
not been modified. This value MAY contain padding if
required by the cipher suite.</c>
<c>9-255</c>
<c>Reserved</c>
<c> </c>
</texttable>
</section>
<section anchor="bsp_example" title="BSP Block Example">
<t>
An example of SBSP blocks applied to a bundle is illustrated in <xref target="bsp_bundle_fig"/>. 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 SBSP 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.
</t>
<figure anchor="bsp_bundle_fig" title="Sample Use of BSP Blocks">
<artwork><![CDATA[
Block in Bundle ID
+=================================+====+
| Primary Block | B1 |
+---------------------------------+----+
| First BAB | B2 |
| OP(authentication, Bundle) | |
+---------------------------------+----+
| Lone BIB | B3 |
| OP(integrity, target=B1) | |
+---------------------------------+----+
| Lone BCB | B4 |
| OP(confidentiality, target=B5) | |
+---------------------------------+----+
| Extension Block | B5 |
+---------------------------------+----+
| Lone BIB | B6 |
| OP(integrity, target=B7) | |
+---------------------------------+----+
| Extension Block | B7 |
+---------------------------------+----+
| Lone BCB | B8 |
| OP(confidentiality, target=B9) | |
+---------------------------------+----+
| Lone BIB (encrypted by B8) | B9 |
| OP(integrity, target=B11) | |
+---------------------------------+----+
| Lone BCB |B10 |
| OP(confidentiality, target=B11) | |
+---------------------------------+----+
| Payload Block |B11 |
+---------------------------------+----+
| Last BAB |B12 |
| OP(authentication, Bundle) | |
+---------------------------------+----+
]]></artwork>
</figure>
<t>
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 bundle.
<list style="symbols">
<t>
Authentication over the bundle. This is accomplished by two BAB blocks: B2 and B12.
</t>
<t>
An integrity signature applied to the canonicalized primary block. This is accomplished by a single BIB, B3.
</t>
<t>
Confidentiality for the first extension block. This is accomplished by a single BCB block, B4.
</t>
<t>
Integrity for the second extension block. This is accomplished by a single BIB block, B6.
</t>
<t>
An integrity signature on the payload. This is accomplished by a single BIB block, B9.
</t>
<t>
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.
</t>
</list>
</t>
</section>
</section>
<section anchor="SecProc" title="Security Processing">
<t>
This section describes the security aspects of bundle processing.
</t>
<section anchor="CanonBundle" title="Canonical Forms">
<t>
In order to verify a signature of a bundle, 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.
</t>
<t>
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 <xref target="RFC5050"/>.
</t>
<section anchor="BundleCanon" title="Bundle Canonicalization">
<t>
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.
</t>
<t>
Notes:
<list style="symbols">
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
</section>
<section anchor="BlockCanon" title="Block Canonicalization">
<t>
This algorithm protects those parts of a block
that SHOULD NOT be changed in transit.
</t>
<t>
There are three types of blocks that may undergo block
canonicalization: the primary block, the payload block,
or an extension block.
</t>
<section anchor="PrimaryCanon" title="Primary Block Canonicalization">
<t>
The canonical form of the primary block is shown in
<xref target="pblock"/>. Essentially, it de-references the dictionary
block, adjusts lengths where necessary, and ignores
flags that may change in transit.
</t>
<figure anchor="pblock" title="The Canonical Form of the Primary Bundle Block">
<artwork><![CDATA[
+----------------+----------------+----------------+----------------+
| Version | Processing flags (incl. COS and SRR) |
+----------------+----------------+---------------------------------+
| Canonical primary block length |
+----------------+----------------+---------------------------------+
| Destination endpoint ID length |
+----------------+----------------+---------------------------------+
| Destination endpoint ID |
+----------------+----------------+---------------------------------+
| Source endpoint ID length |
+----------------+----------------+----------------+----------------+
| Source endpoint ID |
+----------------+----------------+---------------------------------+
| Report-to endpoint ID length |
+----------------+----------------+----------------+----------------+
| Report-to endpoint ID |
+----------------+----------------+----------------+----------------+
+ Creation Timestamp (2 x SDNV) +
+---------------------------------+---------------------------------+
| Lifetime |
+----------------+----------------+----------------+----------------+
]]></artwork>
</figure>
<t>
The fields shown in <xref target="pblock"/> are as follows:
<list style="symbols">
<t>
The version value is the single-byte value in
the primary block.
</t>
<t>
The processing flags value in the primary block
is an SDNV, and includes the class-of-service
(COS) and status report request (SRR) fields.
For purposes of canonicalization, the unpacked SDNV is
ANDed
with mask 0x0000 0000 0007 C1BE to set to zero
all reserved bits and the "bundle is a fragment"
bit.
</t>
<t>
The canonical primary block length value is a
four-byte value containing the length (in bytes)
of this structure, in network byte order.
</t>
<t>
The destination endpoint ID length and value are
the length (as a four-byte value in network byte
order) and value of the destination endpoint ID
from the primary bundle block. The URI is simply
copied from the relevant part(s) of the dictionary
block and is not itself canonicalized. Although
the dictionary entries contain "null-terminators",
the null-terminators are not included in the
length or the canonicalization.
</t>
<t>
The source endpoint ID length and value are handled
similarly to the destination.
</t>
<t>
The report-to endpoint ID length and value are
handled similarly to the destination.
</t>
<t>
The unpacked SDNVs for the creation timestamp and lifetime
are copied from the primary block.
</t>
<t>
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.
</t>
</list>
</t>
</section>
<section anchor="PayloadCanon" title="Payload Block Canonicalization">
<t>
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.
</t>
<t>
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.
</t>
</section>
<section anchor="ESBCanon" title="Extension Block Canonicalization">
<t>
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.
</t>
<t>
The "Block was forwarded without being processed"
flag is ignored because the bundle may pass through
nodes that do not understand that extension block
and this flag would be set.
</t>
<t>
Endpoint ID references in blocks are canonicalized
using the de-referenced text form in place of the
reference pair. The reference count is not included,
nor is the length of the endpoint ID text. The EID
reference is, therefore, canonicalized as <scheme>:<SSP>, which
includes the ":" character.
</t>
<t>
Since neither the length of the canonicalized EID text nor a
null-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.
</t>
<t>
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.
</t>
</section>
</section>
<section anchor="notesCanon" title="Considerations">
<t>
<list style="symbols">
<t>
The canonical forms for the bundle and various extension blocks is
not transmitted. It is simply an artifact used as
input to digesting.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
These canonicalization algorithms assume that endpoint
IDs themselves are immutable and they are unsuitable for use in
environments where that assumption might be violated.
</t>
<t>
Cipher suites MAY define their own canonicalization algorithms and
require the use of those algorithms over the ones provided in this
specification.
</t>
</list>
</t>
</section>
</section>
<section anchor="EIDConf" title="Endpoint ID Confidentiality">
<t>
Every bundle has a primary block that contains the
source and destination endpoint IDs, and possibly other EIDs
(in the dictionary field) that cannot be encrypted. If
endpoint ID confidentiality is required, then bundle-in-bundle
encapsulation can solve this problem in some instances.
</t>
<t>
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.
</t>
</section>
<section anchor="BundleRX" title="Bundles Received from Other Nodes">
<t>
Security blocks MUST be processed in a specific order when received by a security-aware node.
The processing order is as follows.
<list style="symbols">
<t>
All BAB blocks in the bundle MUST be evaluated prior to evaluating any other block in the bundle.
</t>
<t>
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.
</t>
</list>
</t>
<section title="Receiving BAB Blocks">
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
</section>
<section title="Receiving BCB Blocks">
<t>
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.
</t>
<t>
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 <xref target="RFC5050"/>) 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.
</t>
<t>
When a BCB is decrypted, the recovered plain-text MUST replace
the cipher-text in the security-target body data
</t>
</section>
<section title="Receiving BIB Blocks">
<t>
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.
</t>
<t>
If the security policy of a security-aware node specifies that a bundle SHOULD
apply integrity to a specific security-target and no such BIB is present in the
bundle, then the node MUST process this security-target in accordance with the security
policy. This MAY involve removing the security-target from the bundle. If the removed
security-target is the payload or primary block, the bundle MAY be discarded. This action
may occur at any node that has the ability to verify an integrity signature, not just the
bundle destination.
</t>
<t>
If the bundle has a BIB and the receiving node is the
destination for the bundle, the node MUST verify the security-target
in accordance with the cipher suite specification. If a BIB check fails, the
security-target has failed to authenticate and the
security-target SHALL be processed according to the security
policy. A bundle status report indicating the failure MAY
be generated. Otherwise, if the BIB verifies, the
security-target is ready to be processed for delivery.
</t>
<t>
If the bundle has a BIB and the receiving node is not the
bundle destination, the receiving node MAY attempt to verify
the value in the security-result field. If the check fails, the node SHALL process the
security-target in accordance to local security policy. It
is RECOMMENDED that if a payload integrity check fails at a waypoint that it is processed
in the same way as if the check fails at the destination.
</t>
</section>
</section>
<section anchor="FragRe" title="Bundle Fragmentation and Reassembly">
<t>
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 <xref target="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:
<list style="symbols">
<t>
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.
</t>
<t>
The authentication security policy requirements for a bundle MUST be
applied individually to all the bundles resulting from
a fragmentation event.
</t>
<t>
A BAB cipher suite MAY specify that it only applies to
non-fragmented bundles and not to bundle fragments.
</t>
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
</section>
<section anchor="React" title="Reactive Fragmentation">
<t>
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.
</t>
<t>
Specifically, if the security policy does not require authentication, then
reactive fragmentation MAY be permitted. If the security policy does require authentication,
then reactive fragmentation MUST NOT be permitted if the partial bundle is not sufficient to
allow authentication.
</t>
<t>
If reactive fragmentation is allowed, then all BAB blocks must be removed from created fragments.
</t>
</section>
</section>
<section anchor="KeyMgmt" title="Key Management">
<t>
Key management in delay-tolerant networks is recognized as a difficult
topic and is one that this specification does not attempt to solve.
</t>
</section>
<section anchor="PolCons" title="Policy Considerations">
<t>
When implementing the SBSP, 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.
<list style="symbols">
<t>
If a bundle is received that contains more than one security-operation, in violation of the
SBSP, 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.
</t>
<t>
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.
</t>
<t>
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 SBSP
blocks, replace the security-operation, or some other action.
</t>
<t>
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.
</t>
</list>
</t>
</section>
<section anchor="SecCons" title="Security Considerations">
<t>
Certain applications of DTN need to both sign and encrypt a message,
and there are security issues to consider with this.
<list style="symbols">
<t>
To provide an assurance that a security-target came from a specific source and has not
been changed, then it should be signed with a BIB.
</t>
<t>
To ensure that a security-target cannot be inspected during transit, it should be encrypted
with a BCB.
</t>
<t>
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. First, 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. 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.
</t>
</list>
</t>
</section>
<section anchor="Conf" title="Conformance">
<t>
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.
</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>
This protocol has fields that have been registered by IANA.
</t>
<section anchor="BlockType" title="Bundle Block Types">
<t>
This specification allocates three block types from the existing
"Bundle Block Types" registry defined in [RFC6255].
</t>
<texttable anchor="iana_table">
<preamble>
Additional Entries for the Bundle Block-Type Codes Registry:
</preamble>
<ttcol align='center'> Value </ttcol>
<ttcol align='center'> Description </ttcol>
<ttcol align='center'> Reference </ttcol>
<c>2</c>
<c>Bundle Authentication Block</c>
<c>This document</c>
<c>3</c>
<c>Block Integrity Block</c>
<c>This document</c>
<c>4</c>
<c>Block Confidentiality Block</c>
<c>This document</c>
</texttable>
</section>
<section anchor="CipherFlag" title="Cipher Suite Flags">
<t>
This protocol has a cipher suite flags field and certain flags are
defined. An IANA registry has been set up as follows.
</t>
<t>
The registration policy for this registry is: Specification Required
</t>
<t>
The Value range is: Variable Length
</t>
<texttable anchor="cflag_table">
<preamble>
Cipher Suite Flag Registry:
</preamble>
<ttcol align='center'> Bit Position (right to left) </ttcol>
<ttcol align='center'> Description </ttcol>
<ttcol align='center'> Reference </ttcol>
<c>0</c>
<c>Block contains result</c>
<c>This document</c>
<c>1</c>
<c>Block Contains parameters</c>
<c>This document</c>
<c>2</c>
<c>Source EID ref present</c>
<c>This document</c>
<c>>3</c>
<c>Reserved</c>
<c>This document</c>
</texttable>
</section>
<section anchor="ParmAndResult" title="Parameters and Results">
<t>
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.
</t>
<t>
The registration policy for this registry is: Specification Required
</t>
<t>
The Value range is: 8-bit unsigned integer.
</t>
<texttable anchor="pr_table">
<preamble>
Cipher Suite Parameters and Results Type Registry:
</preamble>
<ttcol align='center'> Value </ttcol>
<ttcol align='center'> Description </ttcol>
<ttcol align='center'> Reference </ttcol>
<c>0</c> <c>reserved</c> <c>This document</c>
<c>1</c> <c>initialization vector (IV)</c> <c>This document</c>
<c>2</c> <c>reserved</c> <c>This document</c>
<c>3</c> <c>key-information</c> <c>This document</c>
<c>4</c> <c>content-range (pair of SDNVs)</c> <c>This document</c>
<c>5</c> <c>integrity signature</c> <c>This document</c>
<c>6</c> <c>unassigned</c> <c>This document</c>
<c>7</c> <c>salt</c> <c>This document</c>
<c>8</c> <c>BCB integrity check value (ICV)</c> <c>This document</c>
<c>9-191</c> <c>reserved</c> <c>This document</c>
<c>192-250</c> <c>private use</c> <c>This document</c>
<c>251-255</c> <c>reserved</c> <c>This document</c>
</texttable>
</section>
</section>
</middle>
<back>
<references title="Normative References">
&RFC5050;
&RFC2119;
&RFC6255;
</references>
<references title="Informative References">
&RFC4838;
&RFC3986;
&RFC6257;
&RFC5751;
</references>
<section anchor="contr" title="Acknowledgements">
<t>
The following participants contributed technical material, use cases,
and useful thoughts on the overall approach to this security
specification: Scott Burleigh of the Jet Propulsion Laboratory,
Amy Alford and Angela Hennessy of the Laboratory for
Telecommunications Sciences, and Angela Dalton and Cherita Corbett
of the Johns Hopkins University Applied Physics Laboratory.
</t>
</section>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 10:09:32 |