Network Working Group M. StJohns Internet-Draft R. Atkinson, Extreme Networks draft-stjohns-sipso-02.txt G. Thomas, US Dept of Defense Expires: 11 MAY 2008 11 November 2007 Common Architecture Label IPv6 Security Option (CALIPSO) Status of this Memo This is an Internet-Draft. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. ABSTRACT This document describes an optional method for encoding explicit packet Sensitivity Labels on IPv6 packets. It is intended for use only within multi-level secure (MLS) networking environments that are both trusted and trustworthy. StJohns & others [Page 1]
Internet-Draft 11 NOV 2007 1. INTRODUCTION The original IPv4 specification in RFC-791 includes an option for labeling the sensitivity of IP packets. That option was revised by RFC-1038 and later by RFC-1108. [RFC-791][RFC-1038][RFC-1108] One or another IP Sensitivity Label option has been in limited deployment for about two decades, most usually in governmental or military internal networks. There are also some commercial sector deployments where corporate security policies require mandatory access controls be applied to sensitive data. For example, some banks use MLS technology to compartment information known to their investment banking staff so that their trading staff is unaware of that information. This document specifies the explicit packet labeling extensions for IPv6 packets. 1.1 History This document is a direct descendent of RFC-1038 and RFC-1108 and is a close cousin to the work done in the Commercial IP Security Option (CIPSO) Working Group of the Trusted Systems Interoperability Group (TSIG). [FIPS-188] The IP Security options defined by 1038 and 1108 were designed with one specific purpose in mind: to support the fielding of an IPv4 packet encryption device called a BLACKER. Because of this, the definitions and assumptions in those documents were necessarily focused on the US Department of Defense and the BLACKER device. Today, packet Sensitivity Labeling is most commonly deployed within multi-level secure (MLS) environments, often composed of Compartmented Mode Workstations (CMWs) connected via a Local Area Network (LAN). So the mechanism defined here is accordingly more general than RFC-1038 or RFC-1108 were. Also, the deployment of Compartmented Mode Workstations ran into operational constraints caused by the limited, and relatively small, space available for IPv4 options. This caused one non-IETF specification for IPv4 packet labeling to have a large number of sub-options. A very unfortunate side-effect of having sub-options within an IPv4 label option was that it became much more challenging to implement Intermediate System support for mandatory access controls (e.g. in a router or MLS guard system) and still be able to forward traffic at or near wire-speed. In the last decade, typical Ethernet link speeds have changed from 10 Mbps half-duplex to 1 Gbps full-duplex. A 10 Gbps full- duplex Ethernet standard is widely available today. The IEEE is actively developing a standard for 100 Gbps Ethernet as of this writing. Forwarding at those speeds typically requires support from ASICs; StJohns & others [Page 2]
Internet-Draft 11 NOV 2007 supporting more complex packet formats usually require significantly more gates than simpler packet formats. So the pressure to have a single simple option format has only increased in the past decade. When IPv6 was initially being developed, it was anticipated that the availability of IP Security, in particular the Encapsulating Security Payload (ESP) and the IP Authentication Header (AH), would obviate the need for explicit packet Sensitivity Labels with IPv6. [RFC-1825, IPSEC, AH, ESP] For MLS IPv6 deployments where the use of AH or ESP is practical, use of AH and/or ESP is recommended. However, some application architectures, most often those not designed for use with Compartmented Mode Workstations or other Multi-Level Secure (MLS) computers, multiplex transactions at different sensitivity levels and/or with different privileges over a single transport-layer communications session. In order to maintain data Sensitivity Labeling for such applications, in order to be able to implement routing and mandatory access control decisions in routers and guards on a per-IP-packet basis, and for other reasons, there is a need to have a mechanism for explicitly labeling the sensitivity information for each IPv6 packet. 1.2. Intent This document describes a generic way of labeling IPv6 datagrams to reflect their particular sensitivity. Provision is made for separating data based on domain of interpretation (e.g. an agency, a country, an alliance, or a coalition), relative sensitivity (i.e. sensitivity levels), and need-to-know or formal access programs (i.e. compartments or categories). A commonly used method of encoding Releasabilities as if they were Compartments is also described. This usage does not have precisely the same semantics as formal Releasability policies, but existing multi-level secure operating systems do not contain operating system support for releasabilities as a separate concept from compartments. In particular, the authors believe that this mechanism is suitable for deployment in UN peace-keeping operations, in NATO operations, in all current US Government MLS environments, and for deployment in other similar commercial or governmental environments. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119.[RFC-2119] StJohns & others [Page 3]
Internet-Draft 11 NOV 2007 2. DEFINITIONS This section defines several terms that are important to understanding and correctly implementing this specification. Because of historical variations in terminology in different communities, several terms have defined synonyms. 2.1. Domain of Interpretation A Domain of Interpretation (DOI) is a shorthand way of identifying the use of a particular labeling, classification and handling system with respect to data, the computers and people who process it, and the networks that carry it. The DOI policies, combined with a particular Sensitivity Label (which is defined to have meaning within that DOI) applied to a datum or collection of data, dictates which systems, and ultimately which persons may receive that data. In other words, a label of "SECRET" by itself is not meaningful; you also have to know the document or data belongs to the US Department of Defense (or some specific commercial firm, some other government, or some multi-national organisation) before you can decide on who is allowed to receive the data. An CALIPSO DOI is an opaque identifier that is used as a pointer to a particular set of policies which define the Sensitivity Levels and Compartments present within the DOI, and by inference, to the "real world" (e.g. used on paper documents) equivalent labels (See "Sensitivity Label" below). Registering or defining a set of real world security policies as a CALIPSO DOI results in a standard way of labeling IP data originating from End Systems "accredited" or "approved" to operate within that DOI and the constraints of those security policies. For example, if one did this for the US Department of Defense, you would list all the acceptable labels such as "Secret" and "Top Secret", and one would link the CALIPSO DOI to the DOD 5200.28 and DOD 5200.1R documents which define how to mark and protect data with the US Department of Defense (DoD).[DoD 5200.28] [DoD 5200.1-R] The scope of the DOI is dependent on the organization creating it. For example, the US might establish a DOI with specific meanings which correspond to the normal way it labels classified documents and which would apply primarily to the DOD, but might also apply to other associated agencies. A company or other organisation might establish a DOI which applies only to itself. Note well: A CALIPSO Domain of Interpretation is different from,and disjoint from, an ISAKMP/IKE Domain of Interpretation. StJohns & others [Page 4]
Internet-Draft 11 NOV 2007 It is important not to confuse the two different concepts, even though the terms might superficially appear similar. 2.2. Sensitivity Level A Sensitivity Level represents a mandatory separation of data based on relative sensitivity. Sensitivity Levels ALWAYS have a specific ordering within a DOI. Clearance to access a specific level of data also implies access to all levels whose sensitivity is less than that level. For example, if the A, B and C are levels, and A is more sensitive than B which is in turn more sensitive than C (A > B > C), access to data at the B level implies access to C as well. As an example, common UK terms for a Sensitivity Level include (from low to high) "Unclassified", "Restricted", "Confidential", "Secret", and "Most Secret". Note well: A Sensitivity Level is only one component of a Sensitivity Label. It is important not to confuse the two terms. The term "Sensitivity Level" has the same meaning as the term "Security Level". 2.3. Compartment A Compartment represents a mandatory segregation of data based on formal information categories, formal information compartments, or formal access programs for specific types of data. For example, a small startup company creates "Finance" and "R&D" compartments to protect data critical to its success -- only employees with a specific need to know (e.g. the accountants and controller for "Finance", specific engineers for "R&D") are given access to each compartment. Each Compartment is separate and distinct. Access to one Compartment does not imply access to any other Compartment. Data may be protected in multiple compartments (e.g. "Finance" data about a new "R&D" project) at the same time, in which case access to ALL of those compartments is required to access the data. Employees only possessing clearance for a given sensitivity level (i.e. without having clearance for any specific compartments at that sensitivity level) do not have access to any data classified in any compartments (e.g. SECRET FINANCE dominates SECRET). Note Well: The term "category" has the same meaning as "compartment". StJohns & others [Page 5]
Internet-Draft 11 NOV 2007 2.4 Releasability A Releasability represents a mandatory segregation of data based on a formal decision to release information to others. For example, two companies (ACME and ACE) are engaging in a technical alliance. ACME labels all information present within its enterprise that is to be shared as part of the alliance as REL ACE (e.g.COMPANY CONFIDENTIAL REL ACE). However, unlike the compartment example above, COMPANY CONFIDENTIAL dominates COMPANY CONFIDENTIAL REL ACE. This means that ACE employees granted a COMPANY CONFIDENTIAL REL ACE clearance can only access releasable material, while ACME employees with a COMPANY CONFIDENTIAL clearance can access all information. If REL ACE were managed as a compartment, then users granted a COMPANY CONFIDENTIAL REL ACE clearance would have access to all of ACME's COMPANY CONFIDENTIAL material, which is undesirable. Releasabilities can be combined (e.g. COMPANY CONFIDENTIAL REL ACE/ABLE). In this case, users possessing a clearance of either COMPANY CONFIDENTIAL, COMPANY CONFIDENTIAL REL ACE, COMPANY CONFIDENTIAL REL ABLE, or COMPANY CONFIDENTIAL REL ACE/ABLE can access this information. Historically, most MLS deployments handled Releasability as if it were an inverted Compartment. Strictly speaking, this can be problematic, because the formal semantics of a compartment are different from the formal semantics of a Releasability. In practice, for some years now some relatively large MLS deployments have been encoding Releasabilities as if they were inverted Compartments. The results have been generally acceptable and those deployments are generally considered successful by their respective user communities. 2.5. Sensitivity Label A Sensitivity Label is a quadruple consisting of a DOI, a Sensitivity Level, a Compartment Set, and a Releasability Set. The Compartment Set may be the empty set if and only if no compartments apply. A Releasability Set may be the empty set if and only if no releasabilities apply. A DOI used within a end system may be implicit or explicit depending on its use. CALIPSO Sensitivity Labels always have an explicit DOI. A CALIPSO Sensitivity Label consists of a Sensitivity Label in a particular format (defined below). A CALIPSO Sensitivity Label ALWAYS contains an explicit DOI value. In a CALIPSO Sensitivity Label, the Compartment Bitmap field is used to encode both the logical Compartment Set and also the logical Releasability Set. StJohns & others [Page 6]
Internet-Draft 11 NOV 2007 A system which does not store a DOI as part of its internal Sensitivity Labels must be considered to have an implicit DOI -- usually that of its primary Accrediting Authority; all objects on such a system inherit this implicit DOI. Note Well: The term "Security Marking" has the same meaning as "Sensitivity Label". 2.5.1 Sensitivity Label Comparison Two Sensitivity Labels (A and B) can be compared. Indeed, the only real reason that Sensitivity Labels exist is so that they may be compared as part of an access control decision. Comparison is critical to determining if a subject (a person, network, etc.) operating at one Sensitivity Label (A) should be allowed to access an object (file, packet,route, etc) classified at another Sensitivity Label (B). The comparison of two labels (A and B) can return one (and only one) of the following results: 1) A can dominate B (e.g. A=SECRET, B=UNCLASSIFIED); A can read B 2) B can dominate A (e.g. A=UNCLASSIFIED, B=SECRET); A cannot access B 3) A equals B (e.g. A=SECRET, B=SECRET); A can read/write B 4) A is incomparable to B (e.g. A=SECRET R&D, B=SECRET FINANCE); A cannot access B By definition, if A and B are members of different DOIs, the result of comparison is always incomparable. It is possible to overcome this if and only if A and/or B can be promoted such that the labels are interpretable within a single DOI. 2.5.2 Range A range is a pair of Sensitivity Labels which indicate both a minimum and a maximum acceptable Sensitivity Label for objects compared against it. A range is usually expressed as "<minimum> : <maximum>" and always has the property that the minimum Sensitivity Label is less than or equal to the maximum Sensivitity Label. In turn, this requires that the two Sensitivity Labels MUST be comparable. A range where <minimum> equals <maximum> may be expressed simply as "<minimum>"; in this case, the only acceptable Sensitivity Label is <minimum>. StJohns & others [Page 7]
Internet-Draft 11 NOV 2007 2.6. Import The act of receiving a datagram and translating the CALIPSO Sensitivity Label of that packet into the appropriate internal (i.e. End System specific) Sensitivity Label. 2.7. Export The act of selecting an appropriate DOI for an outbound datagram, translating the internal (End System specific) label into an CALIPSO Sensitivity Label based on that DOI, and sending the datagram. The selection of the appropriate DOI may be based on many factors including, but not necessarily limited to: Source Port Destination Port Transport Protocol Application Protocol Application Information End System Subnetwork Network Sending Interface System Implicit/Default DOI Regardless of the DOI selected, the Sensitivity Label of the outbound datagram must be consistent with the security policy monitor of the originating system and also with the DOI definition used by all other devices cognisant of that DOI. 2.8. End System An End System (ES) is a host or router from which a datagram originates or to which a datagram is ultimately delivered. The IPv6 community often uses the term Node for what is here called an End System. 2.9. Intermediate System An Intermediate System (IS) is a node that receives and transmits a particular datagram without being either the source or destination of that datagram. An IPv6 router is an example of an Intermediate System. A firewall or security guard device that applies security policies and forwards packets that comply with those security policies is another example of an intermediate system. An intermediate system may handle ("forward") a datagram without necessarily importing or exporting the datagram to/from itself. StJohns & others [Page 8]
Internet-Draft 11 NOV 2007 NOTE WELL: Any given system can be both an end system and an intermediate system -- which role the system assumes at any given time depends on the address(es) of the datagram you are considering and the address(es) associated with that system. 2.10 System Security Policy A system security policy (SSP) consists of a Sensitivity Label and the organizational security policies associated with content labeled with a given security policy. The SSP acts as a bridge between how the organization's Mandatory Access Control (MAC) policy is stated and managed and how the network implements that policy. 3. ARCHITECTURE This document describes a convention for labeling an IPv6 datagram within a particular system security policy. The labels are designed for use within a Mandatory Access Control (MAC) system. A real world example is the security classification system in use within the UK Government. Some data held by the government is "classified", and is therefore restricted by law to those people who have the appropriate "clearances". Commercial examples also exist. For example, one global electrical equipment company has a formal security policy that defines 6 different Sensitivity Levels for its internal data, ranging from "Class 1" to "Class 6" information. Some financial institutions use multiple compartments to restrict access to certain information (e.g. "mergers & acquisitions", "trading") to those working directly on those projects and to deny access to other groups within the company (e.g. equity trading). A CALIPSO Sensitivity Label is the network instantiation of a particular information security policy, and its related labels, classifications, compartments, and releasabilities. Some years ago, the Mandatory Access Control (MAC) policy for US Government classified information was specified formally in mathematical notation.[BL73] As it happens, many other organisations or governments have the same basic Mandatory Access Control (MAC) policy for information with differing ("vertical") Sensitivity Levels. This document builds upon the formal definitions of Bell-LaPadula.[BL73] There are two basic principles "no write down" and "no read up". The first rule means that an entity having minimum Sensitivity Level X must not be able to write information that is marked with a Sensitivity Level below X. The second rule means that an entity having maximum Sensitivity Level X must not be able to read information having a Sensitivity Level above X. In a normal deployment, information downgrading ("write down") must not occur StJohns & others [Page 9]
Internet-Draft 11 NOV 2007 automatically, and is permitted if and only if a person with appropriate "downgrade" privilege manually verifies the information is permitted to be downgraded before the s/he manually re-labels (i.e. "downgrades") the information. Subsequent to the original work by Bell and LaPadula in this area, this formal model was extended to also support ("horizontal") Compartments of information. This document extends Bell-LaPadula to accommodate the notion of separate Domains of Interpretation (DOI). Each DOI constitutes a single comparable domain of Sensitivity Labels as stated by Bell-LaPadula. Sensitivity Labels from different domains cannot be directly compared using Bell-LaPadula semantics. This document is focused on providing standards for encoding Sensitivity Labels in packets, as well as certain standards for how these labels are to be interpreted and enforced at the IP layer. This document recognizes that there are several kinds of application processing that occur above the IP layer that significantly impact end-to-end system security policy enforcement, but are out of scope for this document. In particular, how the network labeling policy is enforced within processing in an end system is critical, but is beyond the scope of a network (IP) layer Sensitivity Label encoding standard. Other specifications exist which discuss such details. [TCSEC] [CMW] [ISO-15408] [CC] [DoD MLOS PP] This standard does not preclude an End System capable of providing labeled packets across some range of Sensitivity Labels. A Compartmented Mode Workstation (CMW) is an example of such an End System.[CMW] This is useful if the End System is capable of and accredited to separate processing across some range of Sensitivity Labels. Such an node would have a range associated with it within the network interface connecting the node to the network. As an example, an End System has the range "SECRET:TOP SECRET" associated with it in the Intermediate System to which the node is attached. SECRET processing on the node is allowed to traverse the network to other SECRET:SECRET segments of the network, ultimately to a SECRET:SECRET node. Likewise, TOP SECRET processing on the node is allowed to traverse a network through TOP SECRET:TOP SECRET segments, ultimately to a TOP SECRET:TOP SECRET node. The node in this case can allow a user on this node to access SECRET and TOP SECRET resources, provided the user holds the appropriate clearances and has been correctly configured. With respect to a given network, each distinct Sensitivity Label represents a separate virtual network which shares the same physical network. There are rules for moving information between the various virtual networks. The model we use within this document is based on the Bell-LaPadula model, but is extended to cover the concept of StJohns & others [Page 10]
Internet-Draft 11 NOV 2007 differing Domains of Interpretation. Nodes that implement this protocol MUST enforce this mandatory separation of data. CALIPSO provides for both horizontal ("Compartment") and vertical ("Sensitivity Level") separation of information, as well as separation based on DOI. The basic rule is that data MUST NOT be delivered to a user or system that is not approved to receive it. NOTE WELL: wherever we say "not approved", we also mean "not cleared", "not certified", and/or "not accredited" as applicable in one's operational community. This specification does not enable AUTOMATIC relabeling of information, within a DOI or to a different DOI. That is, neither automatic "upgrading" nor automatic "downgrading" of information are enabled by this specification. Local security policies might allow some limited downgrading, but this normally requires the intervention of some human entity and is usually done within an End System with respect to the internal Sensitivity Label, rather than on a network or in a intermediate-system (e.g. router, guard). Automatic downgrading is not suggested operational practice; further discussion of downgrading is outside the scope of this protocol specification. Implementers of this specification MUST NOT permit automatic upgrading or downgrading of information in the default configuration of their implementation. Implementers MAY add a configuration knob that would permit a System Security Officer holding appropriate privilege to enable automatic upgrading or downgrading of information. If an implementation supports such a knob, the existence of the configuration knob must be clearly documented and the default knob setting MUST be that automatic upgrading or downgrading is DISABLED. Automatic information upgrading and downgrading is not recommended operational practice. Some existing MLS deployments already use more than one DOI concurrently. User feedback from early drafts of this specification indicates that it is not uncommon at present for a single network link (i.e. IP subnetwork) to carry traffic for both a particular "coalition" (or joint-venture) activity and also for the government (or other organisation) that owns and operates that particular network link. On such a link, one CALIPSO DOI would typically be used for the "coalition" traffic and a different CALIPSO DOI would typically be used for non-coalition traffic (i.e. traffic that is specific to the government that owns and operates that particular network link). Additionally, operational experience with existing MLS systems has shown that if a system only supports a single DOI at a given time, StJohns & others [Page 11]
Internet-Draft 11 NOV 2007 then it is impossible for a deployment to migrate from using one DOI value to a different DOI value in a smooth, lossless manner. Therefore, a node that implements this specification MUST be able to support at least 2 CALIPSO DOIs concurrently. Support for more than 2 concurrent CALIPSO DOIs is encouraged. This requirement to support at least 2 CALIPSO DOIs concurrently is not necessarily an implementation constraint upon portions of the MLS system that are unrelated to the network. Indeed, use of multiple DOIs is also operationally useful in deployments having a single administration that also have very large numbers of compartments. For example, such a deployment might have one set of related compartments in one CALIPSO DOI and a different set of compartments in a different CALIPSO DOI. Some compartments might be present in both DOIs, possibly at different bit positions of the compartment bitmap in different DOIs. While this might make some implementations more complex, it might also be used to reduce the typical size of the IPv6 CALIPSO option in data packets. Moving information between any two DOIs is permitted if and only if the owners of the DOIs: 1) Agree to the exchange, 2) Publish a table of equivalencies which maps the CALIPSO values of one DOI into the other and make that table available within the scope of those two DOIs The owners of two DOIs may choose to permit the exchange on or between any of their systems, or may restrict exchange to a small subset of the systems they own/accredit. One way agreements are permissible, as are agreements which are a subset of the full table of equivalences. Actual administration of inter-DOI agreements is outside the scope of this document. When data leaves an end system it is "exported" to the network, and marked with a particular DOI, Sensitivity Level, and Compartment Set. (This quadruple is collectively termed a Sensitivity Label). This Sensitivity Label is derived from the internal Sensitivity Label (the End System specific implementation of a given Sensitivity Label), and the export DOI. The export DOI is selected based on a range of parameters described in detail later in this document. When data arrives at an end system, it is "imported" from the network to the End System. The data from the datagram takes on an internal Sensitivity Label based on the Sensitivity Label contained StJohns & others [Page 12]
Internet-Draft 11 NOV 2007 in the datagram. This assumes the datagram is marked with a recognizable DOI, there is a corresponding internal Sensitivity Label equivalent to the CALIPSO Sensitivity Label, and the datagram is "within range" for the receiving logical interface. An host or router has one or more physical interfaces. Each physical interface is associated with a physical network segment used to connect the node, router, LAN, or WAN. Each physical interface has one or more Sensitivity Label ranges associated with it. Sensitivity Label ranges from multiple DOIs must be enumerated separately. Multiple ranges from the same DOI are permissible. Each host or router also might have one or more logical network interfaces. A given logical interface is associated with one and only one physical interface. A given physical interface might have more than one associated logical interface. For example, a single Ethernet port might have multiple [IEEE 802.1Q] Virtual LANs (VLANs) associated with it, where each VLAN could be a separate logical interface. Each logical interface has one or more Sensitivity Label ranges associated with it. Sensitivity Label ranges from multiple DOIs must be enumerated separately. Multiple ranges from the same DOI are permissible. Each range associated with a logical interface must fall within a range separately defined for the corresponding physical interface. There is specific user interest in having IPv6 routers that can apply per-logical-interface mandatory access controls based on the contents of the CALIPSO Sensitivity Labels in IPv6 packets. In transit, a datagram is handled based on its CALIPSO Sensitivity Label, and is usually neither imported to or exported from the various intermediate systems it transits. There also is the concept of "CALIPSO Gateways" which import data from one DOI and export it to another DOI such that the effective Sensitivity Label is NOT changed, but is merely represented using a different DOI. In other words, such devices would be trustworthy, trusted, and authorised to provide on-the-fly re-labeling of packets at the boundaries between complete systems of hosts within a single DOI. Typically, such systems require specific certification(s) and accreditation(s) before deployment or use. 4. DEFAULTS Each Intermediate System or End System is responsible for properly interpreting and enforcing the mandatory access control policy. Practically, this means that each node must evaluate the label on the inbound packet, ensure that this Sensitivity Label is valid (i.e. within range) for the receiving interface, and at a minimum only StJohns & others [Page 13]
Internet-Draft 11 NOV 2007 forward the packet to an interface and node where the Sensitivity Label of the packet falls within the assigned range of that node's receiving interface. Packets arriving at a node with an invalid (e.g. out of range) Sensitivity Label MUST be dropped. A Sensitivity Label is valid if and only if the Sensitivity Label falls within the range assigned to the transmitting interface on the sending system and within the range assigned to the receiving interface on the receiving system. These rules need to be applied on each hop a CALIPSO-labelled packet traverses, not merely at the end points of a labelled IP session. If a packet is received from an node which is not aware of CALIPSO Sensitivity Labels (i.e. unaware to assign Sensitivity Labels itself) and the packet is destined for an node which is sensitivity label aware, the receiving node will insert a Sensitivity Label. This Sensitivity Label will be equal to the maximum Sensitivity Label assigned to the originating node if that is known. If the receiving node does not know which Sensitivity Label is assigned to the originating node, the maximum Sensitivity Label of the interface the packet was received upon will be inserted. If a packet is to be sent to an node which is defined to not be Sensitivity Label aware, from an node which is label aware, then the Sensitivity Label MAY be removed upon transmission if and only if local security policy explicitly permits this. The originating node is still responsible for ensuring that the Sensitivity Label on the packet falls within the Sensitivity Label range associated with the receiving node. 5. FORMAT This section describes the format of the CALIPSO option for use with IPv6 datagrams. CALIPSO is an IPv6 hop-by-hop option to ensure that a security gateway or router could apply access controls to IPv6 packets based on the CALIPSO label carried by the packet. An IPv6 datagram MUST NOT ever contain more than one CALIPSO label. This option format is designed with intermediate systems in mind. It is now common for a MLS network deployment to contain an intermediate systems acting as a guard (sometimes several acting as guards). Such a guard device needs to be able to very rapidly parse the sensitivity label in each packet, apply ingress interface MAC policy, forward the packet while aware of the packet's Sensitivity Label, and then apply egress interface MAC policy. At least one prior IP Sensitivity Label option used a syntax that was unduly complex to implement in IP routers. So there is a deliberate effort to choose a streamlined packet syntax that is easy to parse, to encode, and to implement generally. StJohns & others [Page 14]
Internet-Draft 11 NOV 2007 5.1. Option Format ------------------------------------------------------------ | Option Type | Option Length | Cmpt Length | Sens Level | +-------------+---------------+-------------+--------------+ | CALIPSO Domain of Interpretation | +-------------+---------------+-------------+--------------+ | Checksum (CRC-32) | ------------------------------------------------------------ | Compartment Bitmap (Optional; variable length) | +-------------+---------------+-------------+--------------+ 5.1.1. OPTION TYPE field This field contains an unsigned 8-bit value. Its value is (to be assigned by IANA). In the event the IPv6 packet is fragmented by the sending system, this option must be copied on fragmentation. The CALIPSO option is an IPv6 Hop-by-Hop Option. Following the nomenclature of RFC-2460, Section 4.2, the Option Data field of this option must have 4n+2 alignment.[RFC-2460] The Option Data MUST not change en-route. If the option type is not recognised by an intermediate system examining the packet, the option MAY be ignored. If the option type is not recognised by an End System receiving the packet, then the packet MUST be dropped. 5.1.2. OPTION LENGTH field This field contains an unsigned integer 1 octet in size. It has minimum value is 10. This field specifies the Length of the option data field of this option in octets. The Option Type and Option Length fields are not included in the length calculation. 5.1.3 COMPARTMENT LENGTH field This field contains an unsigned 8-bit integer. The field specifies the size of the COMPARTMENT BITMAP field in 64-bit words. The minimum value is zero, which is only when the information in this packet is not in any compartment. Because this specification represents Releasabilities on the wire as inverted Compartments, the size of the COMPARTMENT BITMAP field needs to be large enough to hold not only the set of logical Compartments, but instead to hold the sum of the set of logical Compartments and the set of logical Releasabilities. StJohns & others [Page 15]
Internet-Draft 11 NOV 2007 5.1.5 DOMAIN OF INTERPRETATION field This field contains an unsigned 32-bit integer. IANA maintains a registry with assignments of the DOI values used in this field. The DOI identifies the rules under which this datagram must be handled and protected. NOTE WELL: The DOMAIN OF INTERPRETATION where all 4 octets contain zero is defined to be the NULL DOI. The NULL DOI has no compartments and has a single level whose value and CALIPSO representation are each zero. The NULL DOI MUST NOT ever appear on the wire. If a packet is received containing the NULL DOI, that packet MUST be dropped and the event SHOULD be logged as a security fault. 5.1.6. SENSITIVITY LEVEL field This contains an unsigned 8-bit value. This field contains an opaque octet whose value indicates the relative sensitivity of the data contained in this datagram in the context of the indicated DOI. The values of this field MUST be ordered, with 00000000 being the lowest sensitivity level and 11111111 being the highest sensitivity level. However, in a typical deployment, not all 256 sensitivity levels will be in use. So the set of valid Sensitivity Level values depends upon the CALIPSO DOI in use. This sensitivity ordering rule is necessary so that intermediate systems (e.g. routers or MLS guards) will be able to apply MAC policy with minimal per-packet computation and minimal configuration. 5.1.7 RESERVED field This field is reserved. It MUST be set to all zeros by the originating node. Receiving systems MUST zero this field upon receipt in order to reduce the potential bandwidth of network-derived covert channels. 5.1.8. CRC-32 Checksum Field This field contains an unsigned 32-bit integer containing the CRC-32 checksum calculated over the entire CALIPSO option in this packet. The checksum algorithm is the 32-bit CRC defined by ITU. [ITU-T V.42] For processing simplicity, this is always present, even when AH is used. 5.1.9. Compartment Bitmap This contains a variable number of 64-bit words. Each bit represents one compartment within the DOI. Each "1" bit within an octet in the "Compartment Bitmap" field represents a separate compartment StJohns & others [Page 16]
Internet-Draft 11 NOV 2007 under whose rules the data in this packet must be protected. Hence, each "0" bit indicates that the compartment corresponding with that bit is not applicable to the data in this packet. The assignment of identity to individual bits within a Compartment Bitmap for a given DOI is left to the owner of that DOI. This specification represents a Releasability on the wire as if it were an inverted Compartment. So the Compartment Bitmap holds the sum of both logical Releasabilities and also logical Compartments for a given DOI value. When encoding a Releasability on the wire, a "1" in the corresponding bit of the Compartment Bitmap indicates that the data is not releasable to the indicated Release Group and a "0" in the corresponding bit of the Compartment Bitmap indicates the data is releasable to the indicated Release Group. This permits the Compartment Bitmap evaluation to occur without the evaluator necessarily knowing the human semantic associated with each bit in the Compartment Bitmap. In turn, this facilitates implementation and configuration of mandatory access controls based on the Compartment Bitmap within IPv6 routers or guard devices. 5.2. Packet Word Alignment considerations The basic option is variable length, due to the variable length Compartment Bitmap field. Intermediate Systems and most End Systems perform best when processing fixed length, fixed location items. So the IPv6 base specification levies certain requirements on IPv6 optional headers. So the Compartment Bitmap field must have length in quanta of 64-bit words (e.g. 0 bits, 64 bits, 128 bits) 6. USAGE This section describes specific protocol processing steps required for systems that claim to implement or conform with this specification. 6.1. Sensitivity Label Comparisons This section describes how comparisons are made between two Sensitivity Labels. Implementing this comparison correctly is critical to the MLS system providing the intended Mandatory Access Controls (MAC) to network traffic entering or leaving the system. A Sensitivity Label consists of a DOI, a Sensitivity Level, and zero or more Compartments. The following notation will be used: StJohns & others [Page 17]
Internet-Draft 11 NOV 2007 A.DOI = the DOI portion of Sensitivity Label A A.LEV = the Sensitivity Level portion of Sensitivity Label A A.COMP = the Compartments portion of Sensitivity Label A A:IGNOR = Sensitivity Label A, less the compartment bits represented in IGNOR 6.1.1. "Within Range" A Sensitivity Label, "M", is "within range" for a particular range "LO:HI:IGNOR" while considering a set of ignorable compartments IGNOR, if and only if: 1. M, LO, and HI are members of the same DOI. (M.DOI == LO.DOI == HI.DOI) 2. The range is a valid range. A given range LO:HI:IGNOR is valid if and only if HI:IGNOR is greater than LO:IGNOR. (LO.LEV <= HI.LEV) && ((LO.COMP & ^IGNOR) <= (HI.COMP & ^IGNOR)) 3. The Sensitivity Label M has a Sensitivity Level which is greater than or equal to the Sensitivity Level contained in the low-end Sensitivity Label (LO) from the range and which is less than equal to the Sensitivity Level contained in the high-end Sensitivity Label (HI) from the range. (LO.LEV <= M.LEV <= HI.LEV) AND 4. The Sensitivity Label M has a Compartment set which is a superset (proper or otherwise) of the compartment set contained in the Sensitivity Label from the low-end range (LO) and which is a subset (proper or otherwise) of the compartment set contained in the high end sensitivity label (HI) from the range. ((LO.COMP & ^IGNOR) <= (M.COMP & ^IGNOR) <= (HI.COMP & ^IGNOR)) 6.1.2. "Less Than" or "Below Range" A Sensitivity Label "M" is "less than" a Sensitivity Label "LO" while considering a set of ignorable compartments IGNOR, if and only if: 1. The DOI for the Sensitivity Label M is identical to the StJohns & others [Page 18]
Internet-Draft 11 NOV 2007 DOI for both the low-end and high-end of the range. (M.DOI == LO.DOI == HI.DOI) 2. The sensitivity level of M is less than the sensitivity level of A. (M.LEV < LO.LEV) 3. M.COMP is a subset (proper or otherwise) of A.COMP, excluding compartments specified in IGNOR. (M.COMP & ^IGNOR) <= (LO.COMP & ^IGNOR) A Sensitivity Label "M" is "below range" for a Sensitivity Label "LO:HI:IGNOR", if M:IGNOR is less than LO:IGNOR. 6.1.3. "Greater Than" or "Above Range" A Sensitivity Label, "M" is "greater than" a Sensitivity Label "HI" while considering a set of ignorable compartments IGNOR if and only if: 1. Their DOI's are identical. (M.DOI == HI.DOI) 2A. The Sensitivity Label M's sensitivity level is greater than B's level while M's compartment set is a superset (proper or otherwise) of B's compartment set (M.LEV > HI.LEV) && ((M.COMP & ^IGNOR) >= (HI.COMP & ^IGNOR)) XOR 2B. M's level is greater than or equal to A's level, while M's compartment set is a proper superset of A's compartment set. (M.LEV >= HI.LEV) && ((M.COMP & ^IGNOR) >= (HI.COMP & ^IGNOR)) A Sensitivity Label, "M", is "above range" for a Sensitivity Label, "LO:HI:IGNOR", if M:IGNOR is greater than B:IGNOR. 6.1.4. "Equal To" A Sensitivity Label "A" is "equal to" another Sensitivity Label "B" while considering a set of ignorable compartments IGNOR if and only if: StJohns & others [Page 19]
Internet-Draft 11 NOV 2007 1. They have the exact same DOI. (A.DOI == B.DOI) 2. They have identical sensitivity levels. (A.LEV == B.LEV) 3. Their compartment sets are identical, while considering a set of ignorable compartment bits IGNOR. ((A.COMP & ^IGNOR) == (B.COMP & ^IGNOR)) 6.1.5. "Disjoint" or "Incomparable" A Sensitivity Label "A" is disjoint from another Sensitivity Label "B" while considering a set of ignorable compartments IGNOR if any of these conditions are true: 1. Their DOI's differ. (A.DOI <> B.DOI) 2. They are neither less than, nor greater than, nor equal to each other. (^((A < B) | (A > B) | (A == B))) 3. Their compartment sets are disjoint from each other (^( ((A.COMP & ^IGNOR) <= (B.COMP & ^IGNOR)) | ((A.COMP & ^IGNOR) => (B.COMP & ^IGNOR)) )) 6.2. End System Processing This section describes CALIPSO-related processing for IPv6 packets imported or exported from an End System claiming to implement or conform with this specification. Nothing in this document applies to an IPv6 End System that does not claim to implement or conform with this specification. 6.2.1 Export An end system which sends data to the network is said to "export" it to the network. Before a datagram can leave an end system and be transmitted over a network the following ordered steps must occur: StJohns & others [Page 20]
Internet-Draft 11 NOV 2007 1. Selection of the export DOI: a) If the system implements or permits only one DOI, that DOI is the export DOI. b) elseIf the upper level protocol selects a DOI, that DOI is the one used. Note Well: A connection-oriented transport-layer protocol session (e.g. TCP session, SCTP session) MUST have the same DOI and Sensitivity Label for the life of the connection. The DOI is selected at connection initiation and MUST NOT change during the session. A trusted multi-level application that possesses appropriate privilege MAY use multiple connection-oriented transport-layer protocol sessions with differing Sensitivity Labels concurrently. c) elseIf there are tables defining a specific default DOI for the specific destination End System address or for the network address, then that DOI is selected. d) elseIf there is a specific DOI associated with the sending logical interface (i.e. IP address), then that DOI is selected. e) Else the default DOI for the system is selected. Note Well: In the event the End System selects and uses a specific DOI and that DOI is not recognised by the originating End System's first-hop router, the packet MUST be dropped by the first-hop router. In such a case, the networking API should indicate the connection failure (e.g. with some appropriate error, such as ENOTREACH). This represents either incorrect configuration of either the Intermediate System or of the End System -- xor correct operation for a node that is not permitted to send IPv6 packets with that DOI through that Intermediate System. When an MLS End System is connected to an MLS LAN, it is possible that there would be more than one first-hop Intermediate System concurrently, with different Intermediate Systems having different valid sensitivity-label ranges. Thoughtful use of the IEEE 802 Virtual LAN standard (e.g. with different VLAN IDs corresponding to different sensitivity ranges) might ease proper system configuration in this respect. 2. Export Labeling: StJohns & others [Page 21]
Internet-Draft 11 NOV 2007 Once the DOI is selected, the CALIPSO Sensitivity Label and values are determined based on the internal sensitivity label and the DOI. In the event the internal sensitivity level does not map to a valid CALIPSO Sensitivity Label, then an error SHOULD be returned to the upper level protocol and MAY be logged. No further attempt to send this datagram should be made. 3. Access Control: Once the datagram is marked and the sending logical interface is selected (by the routing code), the datagram's Sensitivity Label is compared against the sensitivity label range(s) associated with that logical interface. For the datagram to be sent, the interface must list the DOI of the datagram Sensitivity Label as one of the permissible DOI's and the datagram Sensitivity Label must be within range for the range associated with that DOI. If the datagram fails this access test an error SHOULD be returned to the upper level protocol and MAY be logged. No further attempt to send this datagram should be made. 6.2.2. Import When a datagram arrives at an interface on an end system, the end system MUST: 1. Verify the CALIPSO checksum. Datagrams with invalid checksums MUST be silently dropped. Such a drop event SHOULD be logged as a security fault. 2. Verify the CALIPSO has a known and valid DOI. Datagrams with unrecognized or illegal DOIs MUST be silently dropped. Such an event SHOULD be logged as a security fault. 3. Verify the DOI is a permitted one for the receiving interface. Datagrams with prohibited DOI values MUST be silently dropped. Such an event SHOULD be logged as a security fault. 4. Verify the CALIPSO Sensitivity Label is within the permitted range for the receiving interface: NOTE WELL: EACH permitted DOI on an interface has a separate table describing the permitted range for that DOI. StJohns & others [Page 22]
Internet-Draft 11 NOV 2007 A datagram which has a Sensitivity Label within the permitted range is accepted for further processing. A datagram which has a Sensitivity Label disjoint with the permitted range MUST be silently dropped. Such an event SHOULD be logged as a security fault, with an indication that the packet was dropped because of a disjoint Sensitivity Label. An ICMP error message MUST NOT be sent in this case. datagram which has a Sensitivity Label below the permitted range MUST be dropped. This event SHOULD be logged as a security fault. An ICMP error message MUST NOT be sent in this case. A datagram with a Sensitivity Label above the permitted range MUST be dropped. This event SHOULD be logged. An ICMP error message MUST NOT be sent in this case. 5. Once the datagram has been accepted, the import Sensitivity Label and DOI are used to associate the appropriate internal Sensitivity Label with the data contained in the datagram. This information MUST be carried as part of the information returned to the upper-layer protocol. 6.3. Intermediate System Rules This section describes CALIPSO-related processing for IPv6 packets transiting an IPv6 Intermediate System that claims to implement and comply with this specification. Nothing in this document applies to an IPv6 Intermediate System that does not claim to comply with this specification. The CALIPSO packet format has been designed so that one can configure an intermediate system with the minimum sensitivity level, maximum sensitivity level, minimum compartment bitmap, and maximum compartment bitmap -- and then deploy that system without forcing the system to know the detailed human meaning of each sensitivity level or compartment bit value. Instead, once the minimum and maximum labels have been configured, the intermediate system can apply a simple algorithm to determine whether or not a packet is within range for a given interface. This design should be straight-forward to implement in ASIC or FPGA hardware because the option format is simple and easy to parse, and because only a single comparison algorithm (defined in this RFC, hence known in advance) is needed. StJohns & others [Page 23]
Internet-Draft 11 NOV 2007 6.3.1. Input Intermediate Systems have slightly different rules for processing marked datagrams than do end systems. Primarily, Intermediate Systems do not IMPORT or EXPORT transit datagrams, they just forward them. Also, in most deployments intermediate systems are used to provide Mandatory Access Controls to packets traversing more than one subnetwork. The following checks MUST occur before any other processing. Upon receiving a CALIPSO-labeled packet, an intermediate system must: 1. Determine whether or not this datagram is destined for (addressed to) this Intermediate System. If so, then the Intermediate System becomes an End System for the purposes of receiving this particular datagram and the rules for IMPORTing described above are followed. 2. Verify the CALIPSO checksum. Datagrams with invalid checksums MUST be silently dropped. The drop event SHOULD be logged as a security fault and MAY additionally be logged as a network fault. NOTE WELL: A checksum failure could indicate a general network problem (e.g. noise on a radio link) that is unrelated to the presence of a CALIPSO option, but it also could indicate an attempt by an adversary to tamper with the value of a CALIPSO label. 3. Verify the CALIPSO has a known and valid DOI. Datagrams with unrecognized or illegal DOIs MUST be silently dropped. Such an event SHOULD be logged as a security fault. 4. Verify the DOI is a permitted one for the receiving interface. Datagrams with prohibited DOIs MUST be silently dropped. Such a drop SHOULD be logged as a security fault. 5. Verify the Sensitivity Label within the CALIPSO is within the permitted range for the receiving interface: Note Well: Each permitted DOI on an interface has a separate table describing the permitted range for that DOI. StJohns & others [Page 24]
Internet-Draft 11 NOV 2007 A rejected datagram which has a Sensitivity Label below or disjoint with the permitted range MUST be silently dropped. Such an event SHOULD be logged as a security fault, including details about the fault. An ICMP error message MUST NOT be sent in this case. A rejected datagram with a Sensitivity Label above the permitted range MUST be dropped. The drop event SHOULD be logged as a security fault. An ICMP error message MUST NOT be sent in this case. If and only if all the above conditions are met is the datagram accepted by the IPv6 Intermediate System for further processing and forwarding. At this point, the datagram is within the permitted range for the Intermediate System, so appropriate ICMP error messages MAY be created by the IP module back to the originating End System regarding the forwarding of the datagram. These ICMP messages MUST be created with the exact same Sensitivity Label as the datagram causing the error. Standard rules about generating ICMP error messages (e.g. never generate an ICMP error message in response to a received ICMP error message) continue to apply. Note that these locally-generated ICMP messages must go through the same outbound checks (including MAC checks) as any other forwarded datagram as described in the following paragraphs. 6.3.2. Translation It is at this point that TRANSLATION of the CALIPSO takes place if at all. Please see Section 6.4 for a discussion of the appropriate processing for Translation. 6.3.3. Output Once the forwarding code has selected the interface through which the datagram will be transmitted the following takes place: 1. Verify the DOI is a permitted one for the sending interface and that the datagram is within the permitted range for the DOI and for the interface. 2. Datagrams with prohibited DOIs or with out of range Sensitivity Labels MUST be dropped. Any drop event SHOULD be logged as a security fault, including appropriate details about which datagram was dropped and why. StJohns & others [Page 25]
Internet-Draft 11 NOV 2007 3. Datagrams with prohibited DOIs or out of range Sensitivity Labels MAY result in an appropriate ICMP error message, depending upon the security configuration of the system. If an ICMP Error Message is sent, it MUST be sent with the same Sensitivity Label as the rejected datagram. The choice of whether or not to send an ICMP message, if sending an ICMP message for this case is implemented, MUST be configurable, and SHOULD default to OFF. Standard conditions about generating ICMP error messages (e.g. never send an ICMP error message about a received ICMP error message) apply. 6.4. Translation A system which provides on-the-fly re-labeling is said to "translate" from one DOI to another. There are basically two ways a datagram can be relabeled: EITHER the Sensitivity Label can be converted from a CALIPSO Sensitivity Label, to an internal Sensitivity Label, and then back to a new CALIPSO Sensitivity Label, XOR a CALIPSO Sensitivity Label can be directly remapped into a new CALIPSO Sensitivity Label. The first of these methods is the functional equivalent of "importing" the datagram then "exporting" it and is covered in detail in the "Import" and "Export" sections above. This section describes direct relabeling. The choice of which method to use for relabeling is an implementation decision outside the scope of this document. A system which provides on-the-fly relabeling without importing or exporting is basically a special case of the Intermediate System rules listed above. Translation or relabeling takes place AFTER all input checks take place, but before any output checks are done. Once a datagram has been accepted (passing all the appropriate checks described in section 5.3), it may be relabeled. To determine the new Sensitivity Label, first determine the new DOI. The selection of the new DOI may be based on any of DESTINATION END SYSTEM, DESTINATION NETWORK, DESTINATION SUBNET, SENDING INTERFACE, or RECEIVING INTERFACE or combinations thereof. Exact details on how the output DOI is selected are implementation dependent, with the caveat that it should be consistent and reversible. If a datagram from End System A to End System B with DOI X maps into DOI Y, then a datagram from B to A with DOI Y should map into DOI X. StJohns & others [Page 26]
Internet-Draft 11 NOV 2007 Once the output DOI is selected, the output Sensitivity Label is determined based on (1) the input DOI and input Sensitivity Label and (2) the output DOI. In the event the input Sensitivity Label does not map to a valid output Sensitivity Label for the output DOI, then the datagram MUST be silently dropped and the drop event SHOULD be logged as a security fault. Once the datagram is re-labeled, the output procedures under Section 5.3 "Intermediate Systems" are followed, with the exception that any error that would cause a ICMP error message to be generated back to the originating End System instead MUST drop the datagram. Such a drop SHOULD be logged as a security fault. 7. IMPLEMENTATION ISSUES AND HINTS The following are "hints" not "requirements". Implementation experience could eventually turn some of them into implementation requirements. 7.1. Intermediate Systems Performance is optimised if there is hardware support for applying the mandatory access controls based on this label option. 7.2. End Systems It is possible to create two DOIs with different overlapping compartment ranges. This can be used to reduce the size of the IPv6 Sensitivity Label option in some deployments. 7.3. Upper-Level Protocols As CALIPSO is an IP option, this document focuses upon the network-layer handling of packets containing CALIPSO options. This section provides some discussion of upper-layer protocol issues. This section is not a complete specification for how an MLS host handles information internally after the decision has been made to accept a received IPv6 packet containing a CALIPSO option. Implementers of MLS systems might wish also to consult [TCSEC], [CMW], [CC], [ISO-15408], and [DoD MLOS PP]. In a typical MLS host, the information received from the network (i.e. information not dropped by the network-layer as a result of the CALIPSO processing described in this document) is assigned an internal Sensitivity Label while inside the host operating system. The MLS host uses the Bell-LaPadula Mandatory Access Control policy [BL73] to determine how that information StJohns & others [Page 27]
Internet-Draft 11 NOV 2007 is processed, including to which transport-layer sessions or to which applications the information is delivered. Within this section, we use one additional notation, in an attempt to be both clear and concise. Here, the string "W:XY" defines a Sensitivity Label where the sensitivity level is W && where X and Y are the only compartments enabled, while the string "W::" defines a Sensitivity Label where the sensitivity level is W and there are no compartments enabled. 7.3.1. TCP-related issues With respect to a network, each distinct Sensitivity Label represents a separate virtual network which shares the same physical network. The above statement taken from section 3 has a non-obvious, but critical, corollary. If there are separate virtual networks then it is possible for a system which exists in multiple virtual networks to have identical TCP connections, each one existing in a different virtual network. TCP connections are normally identified by source and destination port, and source and destination address. If a system labels datagrams with the CALIPSO option (which it must do if it exists in multiple virtual networks - e.g. a "multi-level secure" system), then TCP connections are identified by source and destination port, source and destination address, and a Sensitivity Label (optionally, a Sensitivity Label range). CALIPSO-labelled TCP data that is received should be sent to all TCP listeners for that particular TCP connection where the Sensitivity Label of the received TCP data is within range for that listener. 7.3.2. UDP-related Issues Unlike TCP or SCTP, UDP is a stateless protocol, at least conceptually. However, many implementations of UDP have some session state (e.g. Protocol Control Blocks in 4.4 BSD), although the UDP protocol specifications do not require any state. One consequence of this is that in widely used host implementations of UDP and IPv6, a UDP listener might be bound only to a particular UDP port on its host -- without binding to a particular remote IP address or local IP address. Datagrams addressed to a UDP port SHOULD be delivered to all listeners on that destination UDP port whose Sensitivity Label range StJohns & others [Page 28]
Internet-Draft 11 NOV 2007 includes the Sensitivity Label of the received UDP datagram. For example, if a listener on UDP port X has a Sensitivity Label range with a minimum of "S:AB" and a maximum of "S:AB", then only datagrams with a destination of UDP port X and a Sensitivity Label of "S:AB" will be delivered to that listener. For example, if a listener on UDP port Y has a Sensitivity Label range with a minimum of "W::" and a maximum of "X:ABC" (where X dominates W), then a datagram addressed to UDP port Y with a Sensitivity Label of "W:A" normally would be delivered to that listener. 7.3.3. SCTP-related Issues With respect to a network, each distinct Sensitivity Label represents a separate virtual network which shares the same physical network. The above statement taken from section 3 has a non-obvious, but critical, corollary. If there are separate virtual networks then it is possible for a system which exists in multiple virtual networks to have identical SCTP connections, each one existing in a different virtual network. As with TCP, SCTP is a connection-oriented transport protocol and has substantial session state. In single-level hosts, this state includes the set of remote IP addresses, the set of local IP addresses, the remote SCTP port number, and the local SCTP port number. In MLS hosts, the SCTP session state also includes the Sensitivity Label (or, optionally, the Sensitivity Label range) for each SCTP session. Unlike TCP, SCTP has the ability to shift an existing SCTP session from one endpoint IP address to a different IP address that belongs to the same endpoint. CALIPSO-labelled SCTP data that is received should be sent to all SCTP listeners for that particular SCTP connection where the Sensitivity Label of the received SCTP data is within range for that listener's Sensitivity Label range. Further, although a node might be multi-homed, it is entirely possible that only one of those interfaces is reachable for a given Sensitivity Label value. For example, one network interface on a node might have a Sensitivity Label range from "A::" to "B:XY" (where B dominates A), while a different network interface on the same node might have a Sensitivity Label range from "U::" "U::" (where A dominates U). In that example, if a packet has a CALIPSO label of "A:X", then that packet will not be able to use the "U"-only network interface. This StJohns & others [Page 29]
Internet-Draft 11 NOV 2007 might lead to novel operational issues with SCTP sessions. Implementers ought to give special attention to this SCTP-specific issue. SECURITY CONSIDERATIONS This document describes a mechanism for adding explicit Sensitivity Labels to IPv6 datagrams. The primary purpose of these labels is to facilitate application of Mandatory Access Controls (MAC) in End Systems or Intermediate Systems that implement this specification. As such, correct implementation of this mechanism is very critical to the overall security of the systems and networks where this mechanisms is deployed. Use of high-assurance development techniques is encouraged. A concern is that since this label is used for mandatory access controls, some method of binding the Sensitivity Label option to the rest of the packet is needed. Without such binding, malicious modification of the Sensitivity Label in a packet would go undetected. So, implementations of this Sensitivity Label option MUST also implement support for the IP Authentication Header. Implementations MUST permit the system administrator to configure whether AH is used or not. This mechanism is only intended for deployment in very limited circumstances where a set of systems and networks are in a well-protected operating environment and the threat of external or internal attack on this mechanism is considered acceptable to the accreditor of those systems and networks. Accreditors of a given deployment should consider not only personnel clearances and physical security issues, but also electronic security (e.g. TEMPEST), network security (NETSEC), communications security (COMSEC), and other issues. IANA CONSIDERATIONS IANA is requested to assign an IPv6 Hop-by-Hop option number to the CALIPSO option described in this specification. This option is immutable during transit. Also, IANA is requested to create a registry for CALIPSO DOI values. The initial values for this registry, shown in dotted-quad format, are as follows: DOI Value Organisation or Use 0.0.0.0 Null DOI; must not be used on the network 0.0.0.1 to 0.255.255.255 For private use among consenting parties For the CALIPSO DOI values registry, IANA is requested to issue StJohns & others [Page 30]
Internet-Draft 11 NOV 2007 a new DOI value to any organisation that requests it. Assignment information normally should be made available on the IANA website. A commercial organisation will normally only be assigned one or two DOI values. A national government or multi-national treaty organisation may be assigned a range of values if that is requested. Different departments within a given national government each may independently request a range of values. ACKNOWLEDGEMENTS This document is directly derived from an Internet-Draft titled "Son of IPSO (SIPSO)" written by the first author circa 1992. Packet format changes have been made since that draft, primarily to comply with IPv6 syntax rules. Steve Brenneman, L.C. Bruzenak, Jarrett Lu, Paul Moore, and Bill Sommerfeld (in alphabetical order) provided feedback on earlier versions of this document. We also would like to thank the several anonymous reviewers, particularly for sharing their insights into operational considerations with MLS networking. INFORMATIVE REFERENCES [BL73] Bell, D.E. & LaPadula, L.J., "Secure Computer Systems: Mathematical Foundations and Model", Technical Report M74-244, The MITRE Corporation, Bedford, MA, May 1973. [CMW] US Defense Intelligence Agency, "Compartmented Mode Workstation Evaluation Criteria", Technical Report DDS-2600-6243-91, Washington, DC. [DOD 5200.1] US Department of Defense, "DoD Information Security Program", Directive 5200.1, 13 December 1996. [DOD 5200.1-R] US Department of Defense, "Information Security Program Regulation", DoD 5200.1-R, 17 January 1997. [DoD 5200.28] US Department of Defense, "Security Requirements for Automated Information Systems," Directive 5200.28, 21 March 1988. [DoD MLOS PP] US Department of Defense, "Protection Profile for Multi-level Operating Systems in Environments requiring Medium Robustness, Version 1.22, 23 May 2001 [ISO-15408] International Stanards Organisation, "Evaluation Criteria for IT Security", ISO/IEC 15408, 2005. StJohns & others [Page 31]
Internet-Draft 11 NOV 2007 [CC] "Common Criteria for Information Technology Security Evaluation", Version 3.1, Revision 1, CCMB-2006-09-001, September 2006. [TCSEC] US Department of Defense, "Trusted Computer System Evaluation Criteria", DoD 5200.28-STD, 26 December 1985. [DoD 8500.1] US Department of Defense, "Information Assurance", Directive 8500.1, 24 October 2002. [FIPS-188] US National Institute of Standards & Technology, "Standard Security Labels for Information Transfer", Federal Information Processing Standard (FIPS) 188, September 1994. [RFC-791] J. Postel, Internet Protocol, RFC-791, September 1981. [RFC-1038] M. StJohns, Draft Revised IP Security Option, RFC-1038, January 1988. [RFC-1108] S. Kent, US DoD Security Options for the Internet Protocol, RFC-1108, November 1991. [RFC-1825] R. Atkinson, Security Architecture for the Internet Protocol, RFC-1825, August 1995. [RFC-2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", RFC-2119, March 1997. [IPSEC] S. Kent, "Security Architecture for the Internet Protocol", RFC-4301, December 2005. [AH] S. Kent, "IP Authentication Header", RFC-4302, December 2005. [ESP] S. Kent, "IP Encapsulating Security Payload", RFC-4303, December 2005. NORMATIVE REFERENCES [RFC-2460] S. Deering & R. Hinden, Internet Protocol Version 6 Specification, RFC-2460, December 1998. [ITU-T V.42] ITU-T, modem standard V.42 (for CRC-32 definition) XXX [Is this the correct reference ?] StJohns & others [Page 32]
Internet-Draft 11 NOV 2007 AUTHORS: M. StJohns Germantown, MD R. Atkinson Extreme Networks 3585 Monroe Street Santa Clara, CA USA 95051 rja@extremenetworks.com +1 (408)579-2800 G. Thomas US Department of Defense Washington, DC USA IETF IPR Clause The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. COPYRIGHT Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained StJohns & others [Page 33]
Internet-Draft 11 NOV 2007 in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Draft Expires: 11 MAY 2008 StJohns & others [Page 34]
