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Versions: (draft-pinkerton-rddp-security) 00 01 02 03 04 05 06 07 08 09 10 RFC 5042

Internet Draft                            James Pinkerton
draft-ietf-rddp-security-01.txt             Microsoft Corporation
Expires: September, 2004                  Ellen Deleganes
                                            Intel Corporation
                                          Allyn Romanow
                                            Cisco Systems
                                          Sara Bitan
                                            Microsoft Corporation
                                          February 2004



                           DDP/RDMAP Security

1  Status of this Memo

   This document is an Internet-Draft and is in full conformance
   with all provisions of Section 10 of RFC2026.

   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/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

2  Abstract

   This document analyzes security issues around implementation and
   use of the Direct Data Placement Protocol(DDP) and Remote Direct
   Memory Access Protocol (RDMAP). It first defines an architectural
   model for an RDMA Network Interface Card (RNIC), which can
   implement DDP or RDMAP and DDP. The document reviews various
   attacks against the resources defined in the architectural model
   and the countermeasures that can be used to protect the system.
   Attacks are grouped into spoofing, tampering, information
   disclosure, denial of service, and elevation of privilege.
   Finally, the document concludes with a summary of security
   services for RDDP, such as IPSec.





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   Table of Contents

   1    Status of this Memo.........................................1
   2    Abstract....................................................1
   2.1  Issues......................................................3
   2.2  Revision History............................................4
   2.2.1  Changes from the -00 to -01 version........................4
   3    Introduction................................................6
   4    Architectural Model.........................................8
   4.1  Components..................................................9
   4.2  Resources..................................................11
   4.2.1  Stream Context Memory.....................................11
   4.2.2  Data Buffers..............................................11
   4.2.3  Page Translation Tables...................................11
   4.2.4  STag Namespace............................................12
   4.2.5  Completion Queues.........................................12
   4.2.6  Asynchronous Event Queue..................................12
   4.2.7  RDMA Read Request Queue...................................13
   4.2.8  RNIC Interactions.........................................13
   4.2.8.1   Privileged Control Interface Semantics................13
   4.2.8.2   Non-Privileged Data Interface Semantics...............13
   4.2.8.3   Privileged Data Interface Semantics...................14
   4.2.9  Initialization of RNIC Data Structures for Data Transfer..14
   4.2.10  RNIC Data Transfer Interactions.........................15
   5    Trust and Resource Sharing.................................17
   6    Attacker Capabilities......................................18
   7    Attacks and Countermeasures................................19
   7.1  Tools for Countermeasures..................................19
   7.1.1  Protection Domain (PD)....................................19
   7.1.2  Limiting STag Scope.......................................20
   7.1.3  Access Rights.............................................21
   7.1.4  Limiting the Scope of the Completion Queue................21
   7.1.5  Limiting the Scope of an Error............................21
   7.2  Spoofing...................................................21
   7.2.1  Impersonation.............................................22
   7.2.2  Stream Hijacking..........................................22
   7.2.3  Man in the Middle Attack..................................22
   7.2.4  Using an STag on a Different Stream.......................23
   7.3  Tampering..................................................24
   7.3.1  Buffer Overrun - RDMA Write or Read Response..............24
   7.3.2  Modifying a Buffer After Indication.......................25
   7.3.3  Multiple STags to access the same buffer..................25
   7.3.4  Network based modification of buffer content..............25
   7.4  Information Disclosure.....................................25
   7.4.1  Probing memory outside of the buffer bounds...............26
   7.4.2  Using RDMA Read to Access Stale Data......................26
   7.4.3  Accessing a Buffer After the Transfer.....................26
   7.4.4  Accessing Unintended Data With a Valid STag...............26
   7.4.5  RDMA Read into an RDMA Write Buffer.......................27
   7.4.6  Using Multiple STags to Access One Buffer.................27
   7.4.7  Remote Node Loading Firmware onto the RNIC................28
   7.4.8  Controlling Access to PTT & STag Mapping..................28


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   7.4.9  Network based eaves dropping..............................28
   7.5  Denial of Service (DOS)....................................28
   7.5.1  RNIC Resource Consumption.................................29
   7.5.2  Resource Consumption By Active Applications...............30
   7.5.2.1   Multiple Streams Sharing Receive Buffers..............30
   7.5.2.2   Local Peer Attacking a Shared CQ......................31
   7.5.2.3   Remote Peer Attacking a Shared CQ.....................32
   7.5.2.4   RDMA Read Request Queue...............................34
   7.5.3  Resource Consumption by Idle Applications.................35
   7.5.4  Exercise of non-optimal code paths........................35
   7.5.5  RI an STag Shared on Multiple Streams.....................36
   7.5.6  Remote Peer Consumes Untagged Receive Buffers.............36
   7.6  Elevation of Privilege.....................................36
   8    Security Services for RDDP.................................38
   8.1  Introduction to Security Options...........................38
   8.1.1  Introduction to IPsec.....................................39
   8.1.2  Introduction to SSL Limitations on RDMAP..................40
   8.1.3  Applications Which Provide Security.......................40
   8.2  Recommendations for IPsec Encapsulation of RDDP............40
   8.2.1  Transforms................................................41
   8.2.2  IPsec modes...............................................41
   8.2.3  IKE.......................................................41
   8.2.4  Security Policy Configuration.............................43
   9    Security considerations....................................45
   10   References.................................................46
   10.1   Normative References......................................46
   10.2   Informative References....................................47
   11   Appendix A: Implementing Client/Server Protocols...........48
   12   Appendix B: Summary Table of Attacks.......................51
   12.1   Spoofing..................................................52
   12.2   Tampering.................................................52
   12.3   Information Disclosure....................................52
   12.4   Denial of Service.........................................52
   13   Appendix C: Partial Trust Taxonomy.........................54
   14   AuthorÆs Addresses.........................................56
   15   Acknowledgments............................................57
   16   Full Copyright Statement...................................58


   Table of Figures

   Figure 1 - RDMA Security Model....................................9
   Figure 2 - Summary Attacks and Trust Model Table.................53



2.1  Issues

   This section is temporary and will go away when all issues have
   been resolved.




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   Note: this is far from a complete list of issues; as more are
   raised, they will be added to this list until some sort of
   consensus is reached.  They are in the order found in the
   specification.

   <TBD û remove this section: this section was deleted because it
   was a duplicate of Section 7.5.2.1 Multiple Streams Sharing
   Receive Buffers on page 30) Thus comments on this section were
   added to that section.>..........................................36
   Issue: The spec currently makes specific IPsec SHOULD
   recommendations. Should this be relaxed to not be normative,
   since the protocol is just a transport protocol, not an
   application protocol?............................................38
   Issue: Guidance for application protocols like NFS which
   implement security <TBD>.........................................40
   Issue: I think we should refer to IPS security considerations.
   Most of the issues discussed there are relevant for RDDP/RDMA as
   well (exceptions are the discussion on user certificates).<TBD>..45
   Issue: Finish Summary table of Attacks/Trust Models <TBD>........51


2.2  Revision History

2.2.1  Changes from the -00 to -01 version

       *   Added two pages to the architectural model to describe
           the Asynchronous Event Queue, and the types of
           interactions that can occur between the RNIC and the
           modules above it.

       *   Addressed Mike Krauses comments submitted on 12/8/2003

       *   Moved "Trust Models" from the body of the document to an
           appendix. Removed references to it throughout the
           document (including use of "partial trust". Document now
           assumes Remote Peer is untrusted. Thus the key issue is
           whether local resources are shared, and what the resource
           is.

       *   Misc cleanup throughout the document.

       *   The Summary of Attacks at the end of the document is now
           an Appendix. It also now provides a summary. Cleared
           change bars because became unreadable. Also shortened
           section names for attacks to fit in table.

       *   Added a new concept of "Partial Mutual Trust" between a
           collection of Streams to better characterize a set of
           attacks in a client/server environment.

       *   Filled in Security Services for RDDP section (almost all
           is new, except IPsec overview).


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       *   Globally tried to change "connection" to "Stream". In
           some cases it can be either a connection or stream.




















































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3  Introduction

   RDMA enables new levels of flexibility when communicating between
   two parties compared to current conventional networking practice
   (e.g. a stream-based model or datagram model). This flexibility
   brings new security issues that must be carefully understood when
   designing application protocols utilizing RDMA and when
   implementing RDMA-aware NICs (RNICs). Note that for the purposes
   of this security analysis, an RNIC may implement RDMAP and DDP,
   or just DDP.

   The specification first develops an architectural model that is
   relevant for the security analysis - it details components,
   resources, and system properties that may be attacked in Section
   4.

   It then defines what resources a ULP may share locally across
   Streams and what resources the ULP may share with the Remote Peer
   across Streams in Section 5. In general, intentional sharing of
   resources between multiple Streams implies a trust model between
   the Streams. This is defined as:

        Partial Mutual Trust û a collection of RDMAP/DDP Streams,
        which represent the local and remote end points of the
        Stream, are willing to assume that the Streams from the
        collection will not perform malicious attacks against any of
        the Streams in the collection. Applications have explicit
        control of which collection of endpoints is in the
        collection through tools discussed in Section 7.1 Tools for
        Countermeasures on page 19.

   An untrusted peer relationship is appropriate when an application
   wishes to ensure that it will be robust and uncompromised even in
   the face of a deliberate attack by its peer. For example, a
   single application that concurrently supports multiple unrelated
   sessions (e.g. a server) would presumably treat each of its peers
   as an untrusted peer. For a collection of Streams which share
   Partial Mutual Trust, the assumption is that any Stream not in
   the collection is untrusted. For the untrusted peer, a brief list
   of capabilities is enumerated in Section 6.

   The rest of the specification is focused on analyzing attacks.
   First, the tools for mitigating attacks are listed (Section 7.1),
   and then a series of attacks on components, resources, or system
   properties is enumerated in the rest of Section 7. For each
   attack, possible countermeasures are reviewed. If all recommended
   mitigations are in place the implemented usage models, the
   RDMAP/DDP protocol can be shown to not expose any new security
   vulnerabilities.

   Applications within a host are divided into two categories -
   Privileged and Non-Privileged. Both application types can send


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   and receive data and request resources. The key differences
   between the two are:

        The Privileged Application is trusted by the system to not
        maliciously attack the operating environment, but it is not
        trusted to optimize resource allocation globally. For
        example, the Privileged Application could be a kernel
        application, thus the kernel presumably has in some way
        vetted the application before allowing it to execute.

        A Non-Privileged ApplicationÆs capabilities are a logical
        sub-set of the Privileged ApplicationÆs. It is assumed by
        the local system that a Non-Privileged Application is
        untrusted. All Non-Privileged Application interactions with
        the RNIC Engine that could affect other applications need to
        be done through a trusted intermediary that can verify the
        Non-Privileged Application requests.





































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4  Architectural Model

   This section describes an RDMA architectural reference model that
   is used as security issues are examined. It introduces the
   components of the model, the resources that can be attacked, the
   types of interactions possible between components and resources,
   and the system properties, which should be preserved when under
   attack.

   Figure 1 shows the components comprising the architecture and the
   interfaces where potential security attacks could be launched.
   External attacks can be injected into the system from an
   application that sits above the RI or from the Internet.

   The intent here is to describe high level components and
   capabilities which affect threat analysis, and not focus on
   specific implementation options. Also note that the architectural
   model is an abstraction, and an actual implementation may choose
   to subdivide its components along different boundary lines than
   defined here. For example, the Privileged Resource Manager may be
   partially or completely encapsulated in the Privileged
   Application. Regardless, it is expected that the security
   analysis of the potential threats and countermeasures still
   apply.






























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          +-------------+
          |  Privileged |
          |  Resource   |
 Admin<-+>|  Manager    |     App Control Interface
        | |             |<------+-------------------+
        | +-------------+       |                   |
        |       ^               v                   v
        |       |         +-------------+   +-----------------+
        |---------------->| Privileged  |   |  Non-Privileged |
                |         | Application |   |  Application    |
                |         +-------------+   +-----------------+
                |               ^                   ^
                |Privileged     |Privileged         |Non-Privileged
                |Control        |Data               |Data
                |Interface      |Interface          |Interface
RNIC            |               |                   |
Interface(RI)   v               v                   v
=================================================================

              +--------------------------------------+
              |                                      |
              |               RNIC Engine            | <-- Firmware
              |                                      |
              +--------------------------------------+
                                ^
                                |
                                v
                             Internet

                     Figure 1 - RDMA Security Model

4.1  Components

   The components shown in Figure 1 - RDMA Security Model are:

       *   RNIC Engine - the component that implements the RDMA
           protocol and/or DDP protocol.

       *   Privileged Resource Manager - the component responsible
           for managing and allocating resources associated with the
           RNIC Engine. The Resource Manager does not send or
           receive data. Note that whether the Resource Manager is
           an independent component, part of the RNIC, or part of
           the application is implementation dependent. If a
           specific implementation does not wish to address security
           issues resolved by the Resource Manager, there may in
           fact be no resource manager at all.

       *   Privileged Application - See Section 3 Introduction for a
           definition of Privileged Application. The local host
           infrastructure can enable the Privileged Application to


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           map a data buffer directly from the RNIC Engine to the
           host through the RNIC Interface, but it does not allow
           the Privileged Application to directly consume RNIC
           Engine resources.

       *   Non-Privileged Application - See Section 3 Introduction
           for a definition of Non-Privileged Application. All Non-
           Privileged Application interactions with the RNIC Engine
           that could affect other applications MUST be done using
           the Privileged Resource Manager as a proxy.

   A design goal of the DDP and RDMAP protocols is to allow, under
   constrained conditions, Non-Privileged applications to send and
   receive data directly to/from the RDMA Engine without Privileged
   Resource Manager intervention - while ensuring that the host
   remains secure. Thus, one of the primary goals of this paper is
   to analyze this usage model for the enforcement that is required
   in the RNIC Engine to ensure the system remains secure.

   The host interfaces that could be exercised include:

       *   Privileged Control Interface - A Privileged Resource
           Manager uses the RI to allocate and manage RNIC Engine
           resources, control the state within the RNIC Engine, and
           monitor various events from the RNIC Engine. It also uses
           this interface to act as a proxy for some operations that
           a Non-Privileged Application may require (after
           performing appropriate countermeasures).

       *   Application Control Interface û An application uses this
           interface to the Privileged Resource Manager to allocate
           RNIC Engine resources. The Privileged Resource Manager
           implements countermeasures to ensure that if the Non-
           Privileged Application launches an attack it can prevent
           the attack from affecting other applications.

       *   Non-Privileged Data Transfer Interface - A Non-Privileged
           Application uses this interface to initiate and to check
           the status of data transfer operations.

       *   Privileged Data Transfer Interface - A superset of the
           functionality provided by the Non-Privileged Data
           Transfer Interface. The application is allowed to
           directly manipulate RNIC Engine mapping resources to map
           an STag to an application data buffer.

       *   Figure 1 also shows the ability to load new firmware in
           the RNIC Engine. Not all RNICs will support this, but it
           is shown for completeness and is also reviewed under
           potential attacks.




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   If Internet control messages, such as ICMP, ARP, RIPv4, etc. are
   processed by the RNIC Engine, the threat analyses for those
   protocols is also applicable, but outside the scope of this
   paper.

4.2  Resources

   This section describes the primary resources in the RNIC Engine
   that could be affected if under attack. For RDMAP, all of the
   defined resources apply. For DDP, all of the resources except the
   RDMA Read Queue apply.

4.2.1  Stream Context Memory

   The state information for each Stream is maintained in memory,
   which could be located in a number of places - on the NIC, inside
   RAM attached to the NIC, in host memory, or in any combination of
   the three, depending on the implementation.

   Stream Context Memory includes state associated with Data
   Buffers. For Tagged Buffers, this includes how STag names, Data
   Buffers, and Page Translation Tables inter-relate. It also
   includes the FIFO list of Untagged Data Buffers posted for
   reception of Untagged Messages (referred to in some contexts as
   the Receive Queue), and a list of operations to perform to send
   data (referred to in some contexts as the Send Queue).

4.2.2  Data Buffers

   There are two different ways to expose a data buffer; a buffer
   can be exposed for receiving RDMAP Send Type Messages (a.k.a. DDP
   Untagged Messages) on DDP Queue zero or the buffer can be exposed
   for remote access through STags (a.k.a. DDP Tagged Messages).
   This distinction is important because the attacks and the
   countermeasures used to protect against the attack are different
   depending on the method for exposing the buffer to the Internet.

   For the purposes of the security discussion, a single logical
   Data Buffer is exposed with a single STag. Actual implementations
   may support scatter/gather capabilities to enable multiple
   physical data buffers to be accessed with a single STag, but from
   a threat analysis perspective it is assumed that a single STag
   enables access to a single logical Data Buffer.

   In any event, it is the responsibility of the RI to ensure that
   no STag can be created that exposes memory that the consumer had
   no authority to expose.

4.2.3  Page Translation Tables

   Page Translation Tables are the structures used by the RNIC to be
   able to access application memory for data transfer operations.


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   Even though these structures are called "Page" Translation
   Tables, they may not reference a page at all - conceptually they
   are used to map an application address space representation of a
   buffer to the physical addresses that are used by the RNIC Engine
   to move data. If on a specific system, a mapping is not used,
   then a subset of the attacks examined may be appropriate.

4.2.4  STag Namespace

   The DDP specification defines a 32-bit namespace for the STag.
   Implementations may vary in terms of the actual number of STags
   that are supported. In any case, this is a bounded resource that
   can come under attack. Depending upon STag namespace allocation
   algorithms, the actual name space to attack may be significantly
   less than 2^32.

4.2.5  Completion Queues

   Completion Queues are used in this specification to conceptually
   represent how the RNIC Engine notifies the Application about the
   completion of the transmission of data, or the completion of the
   reception of data through the Data Transfer Interface. Because
   there could be many transmissions or receptions in flight at any
   one time, completions are modeled as a queue rather than a single
   event. An implementation may also use the Completion Queue to
   notify the application of other activities, for example, the
   completion of a mapping of an STag to a specific application
   buffer. Completion Queues may be shared by a group of Streams, or
   may be designated to handle a specific Stream's traffic.

   Some implementations may allow this queue to be manipulated
   directly by both Non-Privileged and Privileged applications.

4.2.6  Asynchronous Event Queue

   The Asynchronous Event Queue is a queue from the RNIC to the
   Privileged Resource Manager of bounded size. It is used by the
   RNIC to notify the host of various events which might require
   management action, including protocol violations, Stream state
   changes, local operation errors, low water marks on receive
   queues, and possibly other events.

   The Asynchronous Event Queue is a resource that can be attacked
   because Remote or Local  Peers can cause events to occur which
   have the potential of overflowing the queue.

   Note that an implementation is at liberty to implement the
   functions of the Asynchronous Event Queue in a variety of ways,
   including multiple queues or even simple callbacks. All
   vulnerabilities identified are intended to apply regardless of
   the implementation of the Asynchronous Event Queue. For example,
   a callback function is simply a very short queue.


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4.2.7  RDMA Read Request Queue

   The RDMA Read Request Queue is the memory that holds state
   information for one or more RDMA Read Request Messages that have
   arrived, but for which the RDMA Read Response Messages have not
   yet been completely sent. Because potentially more than one RDMA
   Read Request can be outstanding at one time, the memory is
   modeled as a queue of bounded size.

4.2.8  RNIC Interactions

   With RNIC resources and interfaces defined, it is now possible to
   examine the interactions supported by the generic RNIC functional
   interfaces through each of the 3 interfaces - Privileged Control
   Interface, Privileged Data Interface, and Non-Privileged Data
   Interface.

4.2.8.1  Privileged Control Interface Semantics

   Generically, the Privileged Control Interface controls the RNICÆs
   allocation, deallocation, and initialization of RNIC global
   resources. This includes allocation and deallocation of Stream
   Context Memory, Page Translation Tables, STag names, Completion
   Queues, RDMA Read Request Queues, and Asynchronous Event Queues.

   The Privileged Control Interface is also typically used for
   managing Non-Privileged Application resources for the Non-
   Privileged Application (and possibly for the Privileged
   Application as well). This includes initialization and removal of
   Page Translation Table resources, and managing RNIC events
   (possibly managing all events for the Asynchronous Event Queue).

4.2.8.2  Non-Privileged Data Interface Semantics

   The Non-Privileged Data Interface enables data transfer (transmit
   and receive) but does not allow initialization of the Page
   Translation Table resources. However, once the Page Translation
   Table resources have been initialized, the interface may enable a
   specific STag mapping to be enabled and disabled by directly
   communicating with the RNIC, or create an STag mapping for a
   buffer that has been previously initialized in the RNIC.

   For RDMAP, transmitting data means sending RDMAP Send Type
   Messages, RDMA Read Requests, and RDMA Writes. For data
   reception, for RDMAP it can receive Send Type Messages into
   buffers that have been posted on the Receive Queue or Shared
   Receive Queue. It can also receive RDMA Write and RDMA Read
   Response Messages into buffers that have previously been exposed
   for external write access through advertisement of an STag.

   For DDP, transmitting data means sending DDP Tagged or Untagged
   Messages. For data reception, for DDP it can receive Untagged


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   Messages into buffers that have been posted on the Receive Queue
   or Shared Receive Queue. It can also receive Tagged DDP Messages
   into buffers that have previously been exposed for external write
   access through advertisement of an STag.

   Completion of data transmission or reception generally entails
   informing the application of the completed work by placing
   completion information on the Completion Queue.

4.2.8.3  Privileged Data Interface Semantics

   The Privileged Data Interface semantics are a superset of the
   Non-Privileged Data Transfer semantics. The interface can do
   everything defined in the prior section, as well as
   create/destroy buffer to STag mappings directly. This generally
   entails initialization  or clearing of Page Translation Table
   state in the RNIC.

4.2.9  Initialization of RNIC Data Structures for Data Transfer

   Initialization of the mapping between an STag and a Data Buffer
   can be viewed in the abstract as two separate opertions:

       a.  Initialization of the allocated Page Translation Table
           entries with the location of the Data Buffer, and

       b.  Initialization of a mapping from an allocated STag name
           to a set of Page Translation Table entry(s) or partial-
           entries.

   Note that an implementation may not have a Page Translation Table
   (i.e. it may support a direct mapping between an STag and a Data
   Buffer). In this case threats and mitigations associated with the
   Page Translation Table are not relevant.

   Initialization of the contents of the Page Translation Table can
   be done by either the Privileged Application or by the Privileged
   Resource Manager as a proxy for the Non-Privileged Application.
   By definition the Non-Privileged Application is not trusted to
   directly manipulate the Page Translation Table. In general the
   concern is that the Non-Privileged application may try to
   maliciously initialize the Page Translation Table to access a
   buffer for which it does not have permission.

   The exact resource allocation algorithm for the Page Translation
   Table is outside the scope of this specification. It may be
   allocated for a specific Data Buffer, or be allocated as a pooled
   resource to be consumed by potentially multiple Data Buffers, or
   be managed in some other way. This paper attempts to abstract
   implementation dependent issues, and focus on higher level
   security issues such as resource starvation and sharing of
   resources between Streams.


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   The next issue is how an STag name is associated with a Data
   Buffer. For the case of an Untagged Data Buffer, there is no wire
   visible mapping between an STag name and a Data Buffer. Note that
   there may, in fact, be a mapping that is not visible from the
   wire, but this is a local host specific issue which should be
   analyzed in the context of local host implementation specific
   security analysis, and thus is outside the scope of this paper.

   For a Tagged Data Buffer, either the Privileged Application, the
   Non-Privileged Application, or the  Privileged Resource Manager
   acting on behalf of the Non-Privileged Resource Manager may
   initialize a mapping from an STag to a Page Translation Table, or
   may have the ability to simply enable/disable an existing STag to
   Page Translation Table mapping. There may also be multiple STag
   names which map to a specific group of Page Translation Table
   entries (or sub-entries). Specific security issues with this
   level of flexibility are examined later.

   There are a variety of implementation options for initialization
   of Page Translation Table entries and mapping an STag to a group
   of Page Translation Table entries which have security
   repercussions. This includes support for separation of Mapping an
   STag verses mapping a set of Page Translation Table entries, and
   support for Applications directly manipulating STag to Page
   Translation Table entry mappings (verses requiring access through
   the Privileged Resource Manager).

4.2.10 RNIC Data Transfer Interactions

   RNIC Data Transfer operations can be subdivided into send
   operations and receive operations.

   For send operations, there is typically a queue that enables the
   Application to post multiple operations. Depending upon the
   implementation, Data Buffers used in the operations may or may
   not have Page Translation Table entries associated with them, and
   may or may not have STags associated with them. Because this is a
   local host specific implementation issue rather than a protocol
   issue, the security analysis of threats and mitigations is left
   to the host implementation.

   Receive operations are different for Tagged Data Buffers verses
   Untagged Data Buffers. If more than one Untagged Data Buffer can
   be posted by the Application, the DDP specification requires that
   they be consumed in FIFO order. Thus the most general
   implementation is that there is a FIFO queue of receive Untagged
   Data Buffers. Some implementations may also support sharing of
   the FIFO queue between multiple Streams. In this case defining
   "FIFO" becomes non-trivial - in general the buffers for a single
   stream are consumed from the queue in the order that they were
   placed on the queue, but there is no order guarantee between
   streams.


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   For receive Tagged Data Buffers, at some time prior to data
   transfer, the mapping of the STag to specific Page Translation
   Table entries (if present) and the mapping from the Page
   Translation Table entries to the Data Buffer must have been
   initialized (see the prior section for interaction details).

















































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5  Trust and Resource Sharing

   It is assumed that in general the Local and Remote Peer are
   untrusted, and thus attacks by either should have mitigations in
   place.

   A separate, but related issue is resource sharing between
   multiple streams. If local resources are not shared, the
   resources are dedicated on a per Stream basis. Resources are
   defined in Section 4.2 - Resources on page 10. The advantage of
   not sharing resources between Streams is that it reduces the
   types of attacks that are possible. The disadvantage is that
   applications might run out of resources.

   It is assumed in this paper that the component that implements
   the mechanism to control sharing of RNIC Engine resources is the
   Privileged Resource Manager. The RNIC Engine exposes its
   resources through the RI to the Privileged Resource Manager. All
   Privileged and Non-Privileged applications request resources from
   the Resource Manager. The Resource Manager implements resource
   management policies to ensure fair access to resources. The
   Resource Manager should be designed to take into account security
   attacks detailed in this specification. Note that for some
   systems the Privileged Resource Manager may be implemented within
   the Privileged Application.

   The sharing of resources across Streams should be under the
   control of the application, both in terms of the trust model the
   application wishes to operate under, as well as the level of
   resource sharing the application wishes to give Local Peer
   processes. For more discussion on types of trust models which
   combine partial trust and sharing of resources, see Appendix C:
   Partial Trust Taxonomy on page 54.





















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6  Attacker Capabilities

   An attackerÆs capabilities delimit the types of attacks that
   attacker is able to launch. RDMAP and DDP require that the
   initial LLP Stream (and connection) be set up prior to
   transferring RDMAP/DDP Messages. For the attacker to actively
   generate an RDMAP/DDP protocol attack, it must have the
   capability to both send and receive messages. Attackers with send
   only capabilities should be addressed by the LLP, not by
   RDMAP/DDP.












































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7  Attacks and Countermeasures

   This section describes the attacks that are possible against the
   RDMA system defined in Figure 1 - RDMA Security Model and the
   RNIC Engine resources defined in Section 4.2. The analysis
   includes a detailed description of each attack, what is being
   attacked, and a description of the countermeasures that can be
   taken to thwart the attack.

   Note that connection setup and teardown is presumed to be done in
   stream mode (i.e. no RDMA encapsulation of the payload), so there
   are no new attacks related to connection setup/teardown beyond
   what is already present in the LLP (e.g. TCP or SCTP).
   Consequently, any existing analysis of Spoofing, Tampering,
   Repudiation, Information Disclosure, Denial of Service, or
   Elevation of Privilege continues to apply. Thus, the analysis in
   this section focuses on attacks that are present regardless of
   the LLP Stream type.

   The attacks are classified into five categories: Spoofing,
   Tampering, Information Disclosure, Denail of Service (DoS)
   attacks, and Elevation of Privileges. Tampering is any
   modification of the legitimate traffic (machine internal or
   network). Spoofing attack is a special case of tempering; where
   the attacker falsifies an identity of the Remote Peer (identity
   can be an IP address, machine name, ULP level identity etc.).

7.1  Tools for Countermeasures

   The tools described in this section are the primary mechanisms
   that can be used to provide countermeasures to potential attacks.

7.1.1  Protection Domain (PD)

   Protection Domains are associated with two of the resources of
   concern, Stream Context Memory and STags associated with Page
   Translation Table entries and data buffers. Protection Domains
   are used mainly to ensure that an STag can only be used to access
   the associated data buffer through Streams in the same Protection
   Domain as that STag.

   If an implementation chooses to not share resources between
   Streams, it is recommended that each Stream be associated with
   its own, unique Protection Domain. If an implementation chooses
   to allow resource sharing, it is recommended that Protection
   Domain be limited to the number of Streams that have Partial
   Mutual Trust.

   Note that an application (either Privileged or Non-Privileged)
   can potentially have multiple Protection Domains. This could be
   used, for example, to ensure that multiple clients of a server do
   not have the ability to corrupt each other. The server would


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   allocate a Protection Domain per client to ensure that resources
   covered by the Protection Domain could not be used by another
   (untrusted) client.

7.1.2  Limiting STag Scope

   The key to protecting a local data buffer is to limit the scope
   of its STag to the level appropriate for the Streams which share
   Partial Mutual Trust. The scope of the STag can be measured in
   multiple ways.

       *   Number of Connections and/or Streams on which the STag is
           valid. One way to limit the scope of the STag is to limit
           the connections and/or Streams that are allowed to use
           the STag. As noted in the previous section, use of
           Protection Domains appropriately can limit the scope of
           the STag. The analysis presented in this document assumes
           two mechanisms for limiting the scope of Streams for
           which the STag is valid:

           *   Protection Domain scope. The STag is valid if used on
               any Stream within a specific Protection Domain, and
               is invalid if used on any Stream that is not a member
               of the Protection Domain.

           *   Single Stream scope. The STag is valid on a single
               Stream, regardless of what the Stream association is
               to a Protection Domain. If used on any other Stream,
               it is invalid.

       *   Limit the time an STag is valid. By Invalidating an
           Advertised STag (e.g., revoking remote access to the
           buffers described by an STag when done with the
           transfer), an entire class of attacks can be eliminated.

       *   Limit the buffer the STag can reference. Limiting the
           scope of an STag access to *just* the intended
           application buffers to be exposed is critical to prevent
           certain forms of attacks.

       *   Allocating STag numbers in an unpredictable way. If STags
           are allocated using an algorithm which makes it hard for
           the Remote Peer to guess which STag(s) are currently in
           use, it makes it more difficult for an attacker to guess
           the correct value. As stated in the RDMAP specification
           [RDMAP], an invalid STag will cause the RDMAP Stream to
           be terminated. For the case of [DDP], at a minimum it
           must signal an error to the ULP, and commonly this will
           cause the DDP stream to be terminated.





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7.1.3  Access Rights

   Access Rights associated with a specific Advertised STag or
   RDMAP/DDP Stream provide another mechanism for applications to
   limit the attack capabilities of the Remote Peer. The Local Peer
   can control whether a data buffer is exposed for local only, or
   local and remote access, and assign specific access privileges
   (read, write, read and write) on a per stream or session basis.

   For DDP, when an STag is advertised, the Remote Peer is
   presumably given write access rights to the data (otherwise there
   was not much point to the advertisement). For RDMAP, when an
   application advertises an STag, it can enable write-only, read-
   only, or both write and read access rights.

   Similarly, some applications may wish to provide a single buffer
   with different access rights on a per-Stream or per-Stream basis.
   For example, some Streams may have read-only access, some may
   have remote read and write access, while on other Streams only
   the Local Peer is allowed access.

7.1.4  Limiting the Scope of the Completion Queue

   Completions associated with sending and receiving data, or
   setting up buffers for sending and receiving data, could be
   accumulated in a shared Completion Queue for a group of RDMAP/DDP
   Streams, or a specific RDMAP/DDP Stream could have a dedicated
   Completion Queue. Limiting Completion Queue association to one,
   or a small number of RDMAP/DDP Streams can prevent several forms
   of Denial of Service attacks.

7.1.5  Limiting the Scope of an Error

   To prevent a variety of attacks, it is important that an
   RDMAP/DDP implementation be robust in the face of errors. If an
   error on a specific Stream can cause other unrelated Streams to
   fail, then a broad class of attacks are enabled against the
   implementation.

   For example, an error on a specific RDMAP stream should not cause
   the RNIC to stop processing incoming packets, or corrupt a
   receive queue for an unrelated stream.

7.2  Spoofing

   Spoofing attacks can be launched by the Remote Peer, or by a
   network based attacker. A network based spoofing attack applies
   to all Remote Peers.

   Because the RDMAP Stream is only offloaded if it is in the
   ESTABLISHED state, certain types of traditional forms of wire
   attacks do not apply -- an end-to-end handshake must have


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   occurred to establish the RDMAP Stream. So, the only form of
   spoofing that applies is one when a remote node can both send and
   receive packets. Yet even with this limitation the Stream is
   still exposed to the following spoofing attacks.

7.2.1  Impersonation

   A network based attacker can impersonate a legal RDMA/RDDP peer
   (by spoofing a legal IP address), and establish an RDMA/RDDP
   Stream with the victim. End to end authentication (i.e. IPsec,
   SSL or ULP authentication) provides protection against this
   attack. For additional information see Section 8, Security
   Services for RDDP, on page 38.

7.2.2  Stream Hijacking

   Stream Hijacking happens when a network based attacker follows
   the session establishment phase, and waits until the
   authentication phase (if such a phase exists) is completed
   successfully. He can then spoof the IP address and re-direct the
   Stream from the victim to its own machine. For example, an
   attacker can wait until an iSCSI authentication is completed
   successfully, and hijack the iSCSI Stream.

   The best protection against this form of attack is end-to-end
   session level integrity protection and authentication, such as
   IPsec (see Section 8, Security Services for RDDP, on page 38), to
   prevent spoofing. Another option is to provide physical security.
   Discussion of physical security is out of scope for this
   document.

   Because the connection and/or Stream itself is established by the
   LLP, some LLPs are more difficult to hijack than others. Please
   see the relevant LLP documentation on security issues around
   connection and/or Stream hijacking <TBD: references for SCTP and
   TCP on connection hijacking>.

7.2.3  Man in the Middle Attack

   If a network based attacker has the ability to delete, inject
   replay, or modify packets which will still be accepted by the LLP
   (e.g., TCP sequence number is correct) then the Stream can be
   exposed to a man in the middle attack. One style of attack is for
   the man-in-the-middle to send Tagged Messages (either RDMAP or
   DDP). If it can discover a buffer that has been exposed for STag
   enabled access, then the man-in-the-middle can use an RDMA Read
   operation to read the contents of the associated data buffer,
   perform an RDMA Write Operation to modify the contents of the
   associated data buffer, or invalidate the STag to disable further
   access to the buffer. The only countermeasure for this form of
   attack is to either secure the RDMAP/DDP Stream (i.e. integrity



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   protect) or attempt to provide physical security to prevent man-
   in-the-middle type attacks.

   The best protection against this form of attack is end-to-end
   integrity protection and authentication, such as IPsec (see
   Section 8 Security Services for RDDP on page 38), to prevent
   spoofing or tampering. If Stream or session level authentication
   and integrity protection are not used, then a man-in-the-middle
   attack can occur, enabling spoofing and tampering.

   Because the connection/Stream itself is established by the LLP,
   some LLPs are more exposed to man-in-the-middle attack then
   others. Please see the relevant LLP documentation on security
   issues around connection and/or Stream hijacking <TBD: references
   for SCTP and TCP on connection hijacking>.

   Another approach is to restrict access to only the local
   subnet/link, and provide some mechanism to limit access, such as
   physical security or 802.1.x. This model is an extremely limited
   deployment scenario, and will not be further examined here.

7.2.4  Using an STag on a Different Stream

   One style of attack from the Remote Peer is for it to attempt to
   use STag values that it is not authorized to use. Note that if
   the Remote Peer sends an invalid STag to the Local Peer, per the
   DDP and RDMAP specifications, the Stream must be torn down. Thus
   the threat exists if a STag has been enabled for Remote Access on
   one Stream and a Remote Peer is able to use it on an unrelated
   Stream. If the attack is successful, the attacker could
   potentially be able to perform either RDMA Read Operations to
   read the contents of the associated data buffer, perform RDMA
   Write Operations to modify the contents of the associated data
   buffer, or to Invalidate the STag to disable further access to
   the buffer.

   An attempt by a Remote Peer to access a buffer with an STag on a
   different Stream in the same Protection Domain may or may not be
   an attack depending on whether resource sharing is intended
   (i.e. whether the Streams shared Partial Mutual Trust or not).
   For some applications using an STag on multiple Streams within
   the same Protection Domain could be desired behavior. For other
   applications attempting to use an STag on a different Stream
   could be considered to be an attack. Since this varies by
   application, an application typically would need to be able to
   control the scope of the STag.

   In the case where an implementation does not share resources
   between Streams (including STags), this attack can be defeated by
   assigning each Stream to a different Protection Domain. Before
   allowing remote access to the buffer, the Protection Domain of
   the Stream where the access attempt was made is matched against


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   the Protection Domain of the STag. If the Protection Domains do
   not match, access to the buffer is denied, an error is generated,
   and the RDMAP Stream associated with the attacking Stream should
   be terminated.

   For implementations that share resources between multiple
   Streams, it may not be practical to separate each Stream into its
   own Protection Domain. In this case, the application can still
   limit the scope of any of the STags to a single Stream (if it is
   enabling it for remote access). If the STag scope has been
   limited to a single Stream, any attempt to use that STag on a
   different Stream will result in an error, and the RDMA Stream
   should be terminated.

   Thus for implementations that do not share STags between Streams
   it is RECOMMENDED that either each Stream be in a separate
   Protection Domain or the scope of an STag be limited to a single
   Stream.

   An additional issue may be unintended sharing of STags (i.e. a
   bug in the application) or a bug in the Remote Peer which causes
   an off-by-one STag to be used. For additional protection, it is
   RECOMMENDED that the allocation of STags be done in such a
   fashion that it is difficult to predict the next allocated STag
   number. Allocation methods which deterministically allocate the
   next STag should be avoided (e.g. a method which always starts
   with STag equal to one and monotonically increases it for each
   new allocation).

7.3  Tampering

   A Remote Peer or a network based attacker can attempt to tamper
   with the contents of data buffers on a Local Peer that have been
   enabled for remote write access. The types of tampering attacks
   that are possible are outlined in the sections that follow.

7.3.1  Buffer Overrun - RDMA Write or Read Response

   This attack is an attempt by the Remote Peer to perform an RDMA
   Write or RDMA Read Response to memory outside of the valid length
   range of the data buffer enabled for remote write access. This
   attack can occur even when no resources are shared across
   Streams. This issue can also arise if the application has a bug.

   The countermeasure for this type of attack must be in the RNIC
   implementation, using the STag. When the Local Peer specifies to
   the RI the base address and the number of bytes in the buffer
   that it wishes to make accessible, the RI must ensure that the
   base and bounds check are applied to any access to the buffer
   referenced by the STag before the STag is enabled for access.
   When an RDMA data transfer operation (which includes an STag)
   arrives on a Stream, a base and bounds byte granularity access


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   check must be performed to ensure the operation accesses only
   memory locations within the buffer described by that STag.

   Thus, it is RECOMMENDED that an RI implementation ensure that a
   Remote Peer will not be able to access memory outside of the
   buffer specified when the STag was enabled for remote access.

7.3.2  Modifying a Buffer After Indication

   This attack occurs if a Remote Peer attempts to modify the
   contents by performing an RDMA Write or an RDMA Read Response
   after it had indicated to the Local Peer that the data buffer
   contents were ready for use.

   This attack can occur even when no resources are shared across
   Streams. Note that a bug in a Remote Peer, or network based
   tampering, could also result in this problem.

   The Local Peer can protect itself from this type of attack by
   revoking remote access when the original data transfer has
   completed and before it validates the contents of the buffer. The
   Local Peer can either do this by explicitly revoking remote
   access rights for the STag when the Remote Peer indicates the
   operation has completed, or by checking to make sure the Remote
   Peer Invalidated the STag through the RDMAP Invalidate
   capability, and if it did not, the Local Peer then explicitly
   revokes the STag remote access rights.

   It is RECOMMENDED that the Local Peer follow the above procedure
   to protect the buffer before it validates the contents of the
   buffer (or uses the buffer in any way).

7.3.3  Multiple STags to access the same buffer

   See section 7.4.6 on page 27 for this analysis.

7.3.4  Network based modification of buffer content

   This is actually a man in the middle attack û but only on the
   content of the buffer, as opposed to the man in the middle attack
   presented above, where both the signaling and content can be
   modified. See Section 7.2.3 Man in the Middle Attack on page 22.

7.4  Information Disclosure

   The main potential source for information disclosure is through a
   local buffer that has been enabled for remote access. If the
   buffer can be probed by a Remote Peer on another Stream, then
   there is potential for information disclosure.





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   The potential attacks that could result in unintended information
   disclosure and countermeasures are detailed in the following
   sections.

7.4.1  Probing memory outside of the buffer bounds

   This is essentially the same attack as described in Section
   7.3.1, except an RDMA Read Request is used to mount the attack.
   The same countermeasure applies.

7.4.2  Using RDMA Read to Access Stale Data

   If a buffer is being used for a combination of reads and writes
   (either remote or local), and is exposed to the Remote Peer with
   at least remote read access rights, the Remote Peer may be able
   to examine the contents of the buffer before they are initialized
   with the correct data. In this situation, whatever contents were
   present in the buffer before the buffer is initialized can be
   viewed by the Remote Peer, if the Remote Peer performs an RDMA
   Read.

   Because of this, it is RECOMMENDED that the Local Peer ensure
   that no stale data is contained in the buffer before remote read
   access rights are granted (this can be done by zeroing the
   contents of the memory, for example).

7.4.3  Accessing a Buffer After the Transfer

   If the Remote Peer has remote read access to a buffer, and by
   some mechanism tells the Local Peer that the transfer has been
   completed, but the Local Peer does not disable remote access to
   the buffer before modifying the data, it is possible for the
   Remote Peer to retrieve the new data.

   This is similar to the attack defined in Section 7.3.2 Modifying
   a Buffer After Indicati on page 25. The same countermeasures
   apply. In addition, it is RECOMMENDED that the Local Peer should
   grant remote read access rights only for the amount of time
   needed to retrieve the data.

7.4.4  Accessing Unintended Data With a Valid STag

   If the Local Peer enables remote access to a buffer using an STag
   that references the entire buffer, but intends only a portion of
   the buffer to be accessed, it is possible for the Remote Peer to
   access the other parts of the buffer anyway.

   To prevent this attack, it is RECOMMENDED that the Local Peer set
   the base and bounds of the buffer when the STag is initialized to
   expose only the data to be retrieved.




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7.4.5  RDMA Read into an RDMA Write Buffer

   One form of disclosure can occur if the access rights on the
   buffer enabled remote read, when only remote write access was
   intended. If the buffer contained application data, or data from
   a transfer on an unrelated Stream, the Remote Peer could retrieve
   the data through an RDMA Read operation.

   The most obvious countermeasure for this attack is to not grant
   remote read access if the buffer is intended to be write-only.
   Then the Remote Peer would not be able to retrieve data
   associated with the buffer. An attempt to do so would result in
   an error and the RDMAP Stream associated with the Stream would be
   terminated.

   Thus, it is RECOMMENDED that if an application only intends a
   buffer to be exposed for remote write access, it set the access
   rights to the buffer to only enable remote write access.

7.4.6  Using Multiple STags to Access One Buffer

   Multiple STags accessing the same buffer at the same time can
   result in unintentional information disclosure if the STags are
   used by different, mutually untrusted, Remote Peers. This model
   applies specifically to client/server communication, where the
   server is communicating with multiple clients, each of which do
   not mutually trust each other.

   If only read access is enabled, then the Local Peer has complete
   control over information disclosure.  Thus a server which
   intended to expose the same data (i.e. buffer) to multiple
   clients by using multiple STags to the same buffer creates no new
   security issues beyond what has already been described in this
   document. Note that if the server did not intend to expose the
   same data to the clients, it should use separate buffers for each
   client (and separate STags).

   When one STag has remote read access enabled and a different STag
   has remote write access enabled to the same buffer, it is
   possible for one Remote Peer to view the contents that have been
   written by another Remote Peer.

   If both STags have remote write access enabled and the two Remote
   Peers do not mutually trust each other, it is possible for one
   Remote Peer to overwrite the contents that have been written by
   the other Remote Peer.

   Thus it is RECOMMENDED that multiple Remote Peers which do not
   share Partial Mutual Trust not be granted write access to the
   same buffer through different STags. A buffer should be exposed
   to only one untrusted Remote Peer at a time to ensure that no



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   information disclosure or information tampering occurs between
   peers.

7.4.7  Remote Node Loading Firmware onto the RNIC

   If the Remote Peer can cause firmware to be loaded onto the RNIC,
   there is an opportunity for information disclosure. See Elevation
   of Privilege in Section 7.6 for this analysis.

7.4.8  Controlling Access to PTT & STag Mapping

   If a Non-Privileged application is able to directly manipulate
   the RNIC Page Translation Tables (which translate from an STag to
   a host address), it is possible that the Non-Privileged
   application could point the Page Translation Table at an
   unrelated applicationÆs buffers and thereby be able to gain
   access to information in the unrelated application.

   As discussed in Section 4 Architectural Model on page 8,
   introduction of a Privileged Resource Manager to arbitrate the
   mapping requests is an effective countermeasure. This enables the
   Privileged Resource Manager to ensure an application can only
   initialize the Page Translation Table (PTT)to point to its own
   buffers.

   Thus it is RECOMMENDED that the Privileged Resource Manager
   verify that the Non-Privileged application has the right to
   access a specific Data Buffer before allowing an STag for which
   the application has access rights to be associated with a
   specific Data Buffer.  This can be done when the Page Translation
   Table is initialized to access the Data Buffer or when the STag
   is initialized to point to a group of Page Translation Table
   entries, or both.

7.4.9  Network based eaves dropping

   An attacker, eaves dropping the network, can read the content of
   all read and write access to the peerÆs buffers. To prevent
   information disclosure, the read/written data must be encrypted.
   The encryption can be done either by the ULP, or by a protocol
   that provides security services to the LLP (e.g. IPsec or SSL).
   Refer to section 8 for discussion of security services for
   RDDP/RDMA.

7.5  Denial of Service (DOS)

   A DOS attack is one of the primary security risks of RDMAP. This
   is because RNIC resources are valuable and scarce, and many
   application environments require communication with untrusted
   Remote Peers. If the remote application can be authenticated or
   encrypted, clearly, the DOS profile can be reduced. For the
   purposes of this analysis, it is assumed that the RNIC must be


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   able to operate in untrusted environments, which are open to DOS
   style attacks.

   Denial of service attacks against RI resources are not the
   typical unknown party spraying packets at a random host (such as
   a TCP SYN attack). Because the connection/Stream must be fully
   established, the attacker must be able to both send and receive
   messages over that connection/Stream, or be able to guess a valid
   packet on an existing RDMAP Stream.

   This section outlines the potential attacks and the
   countermeasures available for dealing with each attack.

7.5.1  RNIC Resource Consumption

   This section covers attacks that fall into the general category
   of a Local Peer attempting to unfairly allocate scarce RNIC
   resources. The Local Peer may be attempting to allocate resources
   on its own behalf, or on behalf of a Remote Peer. Resources that
   fall into this category include: Protection Domains, Stream
   Context Memory, Translation and Protection Tables, and STag
   namespace. These can be attacks by currently active Local Peers
   or ones that allocated resources earlier, but are now idle.

   This type of attack can occur regardless of whether resources are
   shared across Streams.

   It is RECOMMENDED that the allocation of all scarce resources be
   placed under the control of a Privileged Resource Manager. This
   allows the Privileged Resource Manager to:

       *   prevent a Local Peer from allocating more than its fair
           share of resources.

       *   detect if a Remote Peer is attempting to launch a DOS
           attack by attempting to create an excessive number of
           Streams and take corrective action (such as refusing the
           request or applying network layer filters against the
           Remote Peer).

   This analysis assumes that the Resource Manager is responsible
   for handing out Protection Domains, and RNIC implementations will
   provide enough Protection Domains to allow the Resource Manager
   to be able to assign a unique Protection Domain for each
   unrelated, untrusted Local Peer (for a bounded, reasonable number
   of Local Peers). This analysis further assumes that the Resource
   Manager implements policies to ensure that untrusted Local Peers
   are not able to consume all of the Protection Domains through a
   DOS attack. Note that Protection Domain consumption cannot result
   from a DOS attack launched by a Remote Peer, unless a Local Peer
   is acting on the Remote PeerÆs behalf.



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7.5.2  Resource Consumption By Active Applications

   This section describes DOS attacks from Local and Remote Peers
   that are actively exchanging messages. Attacks on each RDMA NIC
   resource are examined and specific countermeasures are
   identified. Note that attacks on Stream Context Memory, Page
   Translation Tables, and STag namespace are covered in Section
   7.5.1 RNIC Resource Consumption, so are not included here.

7.5.2.1  Multiple Streams Sharing Receive Buffers

   The Remote Peer can attempt to consume more than its fair share
   of receive data buffers (Untagged DDP buffers or for RDMAP
   buffers consumed with Send Type Messages) if receive buffers are
   shared across multiple Streams.

   If resources are not shared across multiple Streams, then this
   attack is not possible because the Remote Peer will not be able
   to consume more buffers than were allocated to the Stream. The
   worst case scenario is that the Remote Peer can consume more
   receive buffers than the Local Peer allowed, resulting in no
   buffers to be available, which could cause the Remote PeerÆs
   Stream to the Local Peer to be torn down.

   If local receive data buffers are shared among multiple Streams,
   then the Remote Peer can attempt to consume more than its fair
   share of the receive buffers, causing a different Stream to be
   short of receive buffers, thus possibly causing the other Stream
   to be torn down. For example, if the Remote Peer sent enough one
   byte Untagged Messages, they might be able to consume all local
   shared receive queue resources with little effort on their part.

   One method the Local Peer could use is to recognize that a Remote
   Peer is attempting to use more than its fair share of resources
   and terminate the Stream. However, if the Local Peer is
   sufficiently slow, it may be possible for the Remote Peer to
   still mount a denial of service attack. One countermeasure that
   can protect against this attack is implementing a low-water
   notification. The low-water notification alerts the application
   if the number of buffers in the receive queue is less than a
   threshold.

   If all of the following conditions are true, then the Local Peer
   can size the amount of local receive buffers posted on the
   receive queue to ensure a DOS attack can be stopped.

       *   a low-water notification is enabled, and

       *   the Local Peer is able to bound the amount of time that
           it takes to replenish receive buffers, and




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       *   the Local Peer maintains statistics to determine which
           Remote Peer is consuming buffers.

   The above conditions enable the low-water notification to arrive
   before resources are depleted and thus the Local Peer can take
   corrective action (e.g., terminate the Stream of the attacking
   Remote Peer).

   A different, but similar attack is if the Remote Peer sends a
   significant number of out-of-order packets and the RNIC has the
   ability to use the application buffer as a reassembly buffer. In
   this case the Remote Peer can consume a significant number of
   application buffers, but never send enough data to enable the
   application buffer to be completed to the application.

   An effective countermeasure is to create a high-water
   notification which alerts the application if there is more than a
   specified number of receive buffers "in process" (partially
   consumed, but not completed). The notification is generated when
   more than the specified number of buffers are in process
   simultaneously on a specific Stream (i.e., packets have started
   to arrive for the buffer, but the buffer has not yet been
   delivered to the ULP).

   A different countermeasure is for the RNIC Engine to provide the
   capability to limit the Remote PeerÆs ability to consume receive
   buffers on a per Stream basis. Unfortunately this requires a
   large amount of state to be tracked in each RNIC on a per Stream
   basis.

   Thus, if an RNIC Engine provides the ability to share receive
   buffers across multiple Streams, it is RECOMMENDED that it enable
   the Local Peer to detect if the Remote Peer is attempting to
   consume more than its fair share of resources so that the
   application can apply countermeasures to detect and prevent the
   attack.

7.5.2.2  Local Peer Attacking a Shared CQ

   DOS attacks against a Shared Completion Queue (CQ) can be caused
   by either the Local Peer or the Remote Peer if either attempts to
   cause more completions than its fair share of the number of
   entries, thus potentially starving another unrelated Stream such
   that no Completion Queue entries are available.

   A Completion Queue entry can potentially be consumed by a
   completion from the send queue or a receive completion. In the
   former, the attacker is the Local Peer. In the later, the
   attacker is the Remote Peer.

   A form of attack can occur where the Local Peers can consume
   resources on the CQ. A Local Peer that is slow to free resources


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   on the CQ by not reaping the completion status quickly enough
   could stall all other Local Peers attempting to use that CQ.

   One of two countermeasures can be used to avoid this kind of
   attack. The first is to only share a CQ between Streams that
   share Partial Mutual Trust. The other is to use a trusted Local
   Peer to act as a third party to free resources on the CQ and
   place the status in intermediate storage until the untrusted
   Local Peer reaps the status information. For these reason,
   sharing a CQ across Streams that belong to different Protection
   Domains is NOT RECOMMENDED.

7.5.2.3  Remote Peer Attacking a Shared CQ

   For an overview of the Shared CQ attack model, see Section
   7.5.2.2.

   The Remote Peer can attack a CQ by consuming more than its fair
   share of CQ entries by using one of the following methods:

       *   The ULP protocol allows the Remote Peer to reserve a
           specified number of CQ entries, possibly leaving
           insufficient entries for other Streams that are sharing
           the CQ.

       *   If the Remote Peer or Local Peer (or both) can attack the
           CQ by overwhelming the CQ with completions, then
           completion processing on other Streams sharing that
           Completion Queue can be affected (e.g. the Completion
           Queue overflows and stops functioning).

   The first method of attack can be avoided if the ULP does not
   allow a Remote Peer to reserve CQ entries or there is a trusted
   intermediary such as a Privileged Resource Manager. Unfortunately
   it is often unrealistic to not allow a Remote Peer to reserve CQ
   entries û particularly if the number of completion entries is
   dependent on other ULP negotiated parameters, such as the amount
   of buffering required by the ULP. Thus it is RECOMMENDED that an
   implementation require a Privileged Resource Manager to control
   the allocation of CQ entries.

   One way that a Local or Remote Peer can attempt to overwhelm a CQ
   with completions is by sending minimum length RDMAP/DDP Messages
   to cause as many completions (receive completions for the Remote
   Peer, send completions for the Local Peer) per second as
   possible. If it is the Remote Peer attacking, and we assume that
   the Local Peer does not run out of receive buffers (if they do,
   then this is a different attack, documented in Section 7.5.2.1
   Multiple Streams Sharing Receive Buffers on page 30), then it
   might be possible for the Remote Peer to consume more than its
   fair share of Completion Queue entries. Depending upon the CQ
   implementation, this could either cause the CQ to overflow (if it


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   is not large enough to handle all of the completions generated)
   or for another Stream to not be able to generate CQ entries (if
   the RNIC had flow control on generation of CQ entries into the
   CQ). In either case, the CQ will stop functioning correctly and
   any Streams expecting completions on the CQ will stop
   functioning.

   This attack can occur regardless of whether all of the Streams
   associated with the CQ are in the same Protection Domain or are
   in different Protection Domains û the key issue is that the
   number of Completion Queue entries is less than the number of all
   outstanding operations that can cause a completion.

   The Local Peer can protect itself from this type of attack using
   either of the following methods:

       *   Resize the CQ to the appropriate level(note that resizing
           the CQ can fail, so the CQ resize should be done before
           sizing the Send Queue and Receive Queue on the Stream),
           OR

       *   Grant fewer resources than the Remote Peer requested (not
           supplying the number of Receive Data Buffers requested).

   The proper sizing of the CQ is dependent on whether the Local
   Peer will post as many resources to the various queues as the
   size of the queue enables or not. If the Local Peer can be
   trusted to post a number of resources that is smaller than the
   size of the specific resourceÆs queue, then a correctly sized CQ
   means that the CQ is large enough to hold completion status for
   all of the outstanding Data Buffers (both send and receive
   buffers), or:

   CQ_MIN_SIZE = SUM(MaxPostedOnEachRQ)
                + SUM(MaxPostedOnEachS-RQ)
                + SUM(MaxPostedOnEachSQ)

   If the local peer must be able to completely fill the queues, or
   can not be trusted to observe a limit smaller than the queues,
   then the CQ must be sized to accommodate the maximum number of
   operations that it is possible to post at any one time. Thus the
   equation becomes:

            CQ_MIN_SIZE = SUM(SizeOfEachRQ)
                          + SUM(SizeOfEachS-RQ)
                          + SUM(SizeOfEachSQ)

   Where MaxPosted*OnEach*Q and SizeOfEach*Q varies on a per Stream
   or per Shared Receive Queue basis.

   It is RECOMMENDED that the Local Peer implement a mechanism to
   ensure that the Completion Queue can not overflow. Note that it


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   is possible to share CQs even if the Remote Peers accessing the
   CQs are untrusted if either of the above two formulas are
   implemented. If the Local Peer can be trusted to not post more
   than MaxPostedOnEachRQ, MaxPostedOnEachS-RQ, and
   MaxPostedOnEachSQ, then the first formula applies. If the Local
   Peer can not be trusted to obey the limit, then the second
   formula applies.

7.5.2.4  RDMA Read Request Queue

   If RDMA Read Request Queue resources are pooled across multiple
   Streams, one attack is if the Local Peer attempts to unfairly
   allocate RDMA Read Request Queue resources for its Streams. For
   example, the Local Peer attempts to allocate all available
   resources on a specific RDMA Read Request Queue for its Streams,
   thereby denying the resource to applications sharing the RDMA
   Read Request Queue. The same type of argument applies even if the
   RDMA Read Request is not shared û but a Local Peer attempts to
   allocate all of the RNICs resource when the queue is created.

   Thus it is RECOMMENDED that access to interfaces that allocate
   RDMA Read Request Queue entries be restricted to a trusted Local
   Peer, such as a Privileged Resource Manager. The Privileged
   Resource Manager should prevent a Local Peer from allocating more
   than its fair share of resources.

   Another form of attack is if the Remote Peer sends more RDMA Read
   Requests than the depth of the RDMA Read Request Queue at the
   Local Peer. If the RDMA Read Request Queue is a shared resource,
   this could corrupt the queue. If the queue is not shared, then
   the worst case is that the current Stream is disabled. One
   approach to solving the shared RDMA Read Request Queue would be
   to create thresholds, similar to those described in Section
   7.5.2.1 Multiple Streams Sharing Receive Buffers on page 30. A
   simpler approach is to not share RDMA Read Request Queue
   resources amoung Streams or enforce hard limits of consumption
   per Stream. Thus it is RECOMMENDED that RDMA Read Request Queue
   resource consumption be controlled such that RDMAP/DDP Streams
   which do not share Partial Mutual Trust do not share RDMA Read
   Request Queue resources.

   If the issue is a bug in the Remote PeerÆs implementation, and
   not a malicious attack, the issue can be solved by requiring the
   Remote PeerÆs RNIC to throttle RDMA Read Requests. By properly
   configuring the Stream at the Remote Peer through a trusted
   agent, the RNIC can be made to not transmit RDMA Read Requests
   that exceed the depth of the RDMA Read Request Queue at the Local
   Peer. If the Stream is correctly configured, and if the Remote
   Peer submits more requests than the Local PeerÆs RDMA Read
   Request Queue can handle, the requests would be queued at the
   Remote PeerÆs RNIC until previous requests complete. If the
   Remote PeerÆs Stream is not configured correctly, the RDMAP


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   Stream is terminated when more RDMA Read Requests arrive at the
   Local Peer than the Local Peer can handle (assuming the prior
   paragraphÆs recommendation is implemented).

7.5.3  Resource Consumption by Idle Applications

   The simplest form of a DOS attack given a fixed amount of
   resources is for the Remote Peer to create a RDMAP Stream to a
   Local Peer, and request dedicated resources then do no actual
   work. This allows the Remote Peer to be very light weight (i.e.
   only negotiate resources, but do no data transfer) and consumes a
   disproportionate amount of resources in the server.

   A general countermeasure for this style of attack is to monitor
   active RDMAP Streams and if resources are getting low, reap the
   resources from RDMAP Streams that are not transferring data and
   possibly terminate the Stream. This would presumably be under
   administrative control.

   Refer to Section 7.5.1 for the analysis and countermeasures for
   this style of attack on the following RNIC resources: Stream
   Context Memory, Page Translation Tables and STag namespace.

   Note that some RNIC resources are not at risk of this type of
   attack from a Remote Peer because an attack requires the Remote
   Peer to send messages in order to consume the resource. Receive
   Data Buffers, Completion Queue, and RDMA Read Request Queue
   resources are examples. These resources are, however, at risk
   from a Local Peer that attempts to allocate resources, then goes
   idle. This could also be created if the ULP negotiates the
   resource levels with the Remote Peer, which causes the Local Peer
   to consume resources, however the Remote Peer never sends data to
   consume them. The general countermeasure described in this
   section can be used to free resources allocated by an idle Local
   Peer.

7.5.4  Exercise of non-optimal code paths

   Another form of DOS attack is to attempt to exercise data paths
   that can consume a disproportionate amount of resources. An
   example might be if error cases are handled on a "slow path"
   (consuming either host or RNIC computational resources), and an
   attacker generates excessive numbers of errors in an attempt to
   consume these resources.

   It is RECOMMENDED that an implementation provide the ability to
   detect the above condition and allow an administrator to act,
   including potentially administratively tearing down the RDMAP
   Stream associated with the Stream exercising data paths consuming
   a disproportionate amount of resources.




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7.5.5  RI an STag Shared on Multiple Streams

   If a Local Peer has enabled an STag for remote access, the Remote
   Peer could attempt to remote invalidate (RI) the STag by using
   the RDMAP Send with Invalidate or Send with SE and Invalidate
   Message. If the STag is only valid on the current Stream, then
   the only side effect is that the Remote Peer can no longer use
   the STag; thus there are no security issues.

   If the STag is valid across multiple Streams, then the Remote
   Peer can prevent other Streams from using that STag by using the
   remote invalidate functionality.

   Thus if RDDP Streams do not share Partial Mutual Trust (i.e. the
   Remote Peer may attempt to invalidate the STag prematurely), it
   is NOT RECOMMENDED that the application allow an STag to be valid
   across multiple Streams.

7.5.6  Remote Peer Consumes Untagged Receive Buffers

   <TBD û remove this section: this section was deleted because it
   was a duplicate of Section 7.5.2.1 Multiple Streams Sharing
   Receive Buffers on page 30) Thus comments on this section were
   added to that section.>


7.6  Elevation of Privilege

   The RDMAP/DDP Security Architecture explicitly differentiates
   between three levels of privilege - Non-Privileged, Privileged,
   and the Privileged Resource Manager. If a Non-Privileged
   Application is able to elevate its privilege level to a
   Privileged Application, then mapping a physical address list to
   an STag can provide local and remote access to any physical
   address location on the node. If a Privileged Mode Application is
   able to promote itself to be a Resource Manager, then it is
   possible for it to perform denial of service type attacks where
   substantial amounts of local resources could be consumed.

   In general, elevation of privilege is a local implementation
   specific issue and thus outside the scope of this specification.

   There is one issue worth noting, however. If the RI
   implementation, by some insecure mechanism (or implementation
   defect), can enable a Remote Peer or un-trusted Local Peer to
   load firmware into the RNIC Engine, it is possible to use the
   RNIC to attack the host. Thus, it is RECOMMENDED that an
   implementation not enable firmware to be loaded on the RNIC
   Engine directly from a Remote Peer, unless the Remote Peer is
   properly authenticated (by a mechanism outside the scope of this
   specification), and the update is done via a secure protocol,
   such as IPsec (See Section 8 Security Services for RDDP on page


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   38). It is RECOMMENDED that an implementation not allow a Non-
   Privileged Local Peer to update firmware in the RNIC Engine.




















































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8  Security Services for RDDP

   Issue: The spec currently took the IPSec requirements for iSCSI
   and made them a SHOULD recommendation. A different approach would
   be to simply outline the issues in this section, but leave IPSec
   implementation requirements to be specified by ULP/Application
   requirements. The argument here is that RDDP is a transport, and
   security requirements û particularly authentication and
   confidentiality requirements, are dictated by application
   concerns, not transport protocol concerns. Which approach should
   be taken?


   RDMA and RDDP are used to control, read and write data buffers
   over IP networks. Therefore, the control and the data packets of
   these protocols are vulnerable to the spoofing, tampering and
   information disclosure attacks listed in Section 7.

   Generally speaking, session confidentiality protects against
   eaves dropping. Session authentication and integrity protection
   is a counter measurement against various spoofing and tampering
   attacks. The effectiveness of authentication and integrity
   against a specific attack, depend on whether the authentication
   is machine level authentication (as the one provided by IPsec and
   SSL), or ULP authentication.



8.1  Introduction to Security Options

   The following security services can be applied to an RDDP/RDMA
   session:

   1.  Session confidentiality - protects against eaves dropping
       (section 7.4.9).

   2.  Per-packet data source authentication - protects against the
       following spoofing attacks: network based impersonation
       (section 7.2.1), Stream hijacking (section 7.2.2), and man in
       the middle (section 7.2.3).

   3.  Per-packet integrity - protects against tampering done by
       network based modification of buffer content (section 7.3.4)

   4.  Packet sequencing - protects against replay attacks, which is
       a special case of the above tampering attack.

   If RDDP/RDMA session may be subject to impersonation attacks, or
   Stream hijacking attacks, it is RECOMMENDED that the session be
   authenticated, integrity protected, and protected from replay
   attacks; it MAY use confidentiality protection to protect from



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   eaves dropping (in case the RDDP/RDMA session traverses a public
   network).

   Both IPsec and SSL are capable of providing the above security
   services for IP and TCP traffic respectively. ULP protocols are
   able to provide only part of the above security services. The
   next sections describe the different security options.

8.1.1  Introduction to IPsec

   IPsec is a protocol suite which is used to secure communication
   at the network layer between two peers.  The IPsec protocol suite
   is specified within the IP Security Architecture [RFC2401], IKE
   [RFC2409], IPsec Authentication Header (AH) [RFC2402] and IPsec
   Encapsulating Security Payload (ESP) [RFC2406] documents.  IKE is
   the key management protocol while AH and ESP are used to protect
   IP traffic.

   An IPsec SA is a one-way security association, uniquely
   identified by the 3-tuple: Security Parameter Index (SPI),
   protocol (ESP) and destination IP.  The parameters for an IPsec
   security association are typically established by a key
   management protocol. These include the encapsulation mode,
   encapsulation type, session keys and SPI values.

   IKE is a two phase negotiation protocol based on the modular
   exchange of messages defined by ISAKMP [RFC2408],and the IP
   Security Domain of Interpretation (DOI) [RFC2407]. IKE has two
   phases, and accomplishes the following functions:

   1.  Protected cipher suite and options negotiation - using keyed
       MACs and encryption and anti-replay mechanisms.

   2.  Master key generation - via Diffie-Hellman calculations.

   3.  Authentication of end-points (usually machine level
       authentication).

   4.  IPsec SA management (selector negotiation, options
       negotiation, create, delete, and rekeying).

   Items 1 through 3 are accomplished in IKE Phase 1, while item 4
   is handled in IKE Phase 2.

   IKE phase 1 defines four authentication methods; three of them
   require both sides to have certified signature or encryption
   public keys; the forth require the side to exchange out-of-band a
   secret random string û called pre-shared-secret (PSS).

   An IKE Phase 2 negotiation is performed to establish both an
   inbound and an outbound IPsec SA.  The traffic to be protected by
   an IPsec SA is determined by a selector which has been proposed


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   by the IKE initiator and accepted by the IKE Responder.  The
   IPsec SA selector can be a "filter" or traffic classifier,
   defined as the 5-tuple: <Source IP address, Destination IP
   address, transport protocol (e.g. UDP/SCTP/TCP), Source port,
   Destination port>.  The successful establishment of a IKE Phase-2
   SA results in the creation of two uni-directional IPsec SAs fully
   qualified by the tuple <Protocol (ESP/AH), destination address,
   SPI>.

   The session keys for each IPsec SA are derived from a master key,
   typically via a MODP Diffie-Hellman computation.  Rekeying of an
   existing IPsec SA pair is accomplished by creating two new IPsec
   SAs, making them active, and then optionally deleting the older
   IPsec SA pair.  Typically the new outbound SA is used
   immediately, and the old inbound SA is left active to receive
   packets for some locally defined time, perhaps 30 seconds or 1
   minute. Optionally, rekeying can use Diffie-Helman for keying
   material generation.

8.1.2  Introduction to SSL Limitations on RDMAP

   SSL and TLS [RFC 2246] provide session authentication, integrity
   and confidentiality for TCP based applications. SSL supports one-
   way (server only) or mutual certificates based authentication.

   There are at least two limitations that make SSL less appropriate
   then IPsec for RDDP/RDMA security:

   1. The maximum length supported by the TLS record layer protocol
      is 2^14 bytes, longer packets must be fragmented (as a
      comparison, the maximal length of an IPsec packet, is
      determined by the maximum length of an IP packet).

   2. SSL is a connection oriented protocol. If a stream cipher or
      block cipher in CBC mode is used for bulk encryption, then a
      packet can be decrypted only after all the packets preceding
      it have already arrived. If SSL is used to protect RDDP/RDMA
      traffic, then RDDP/RDMA must gather all out-of-order packets
      before placing them into the ULP buffer, which might cause a
      significant decrease in its efficiency.

8.1.3  Applications Which Provide Security

   Issue: Guidance for application protocols like NFS which
   implement security <TBD>.


8.2  Recommendations for IPsec Encapsulation of RDDP

   Since iSCSI is expected to be one of the ULPs running on top of
   RDDP, the recommendations in this section follow the lines of
   [IPSSEC].


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8.2.1  Transforms

   All RDDP/RDMA security compliant implementations SHOULD support

   IPsec ESP [RFC2406] to provide security for both control packets
   and data packets, as well as the replay protection mechanisms of
   IPsec. When ESP is utilized, per-packet data origin
   authentication, integrity and replay protection MUST be used.

   To provide confidentiality with ESP, ESP with 3DES in CBC mode
   [RFC2451] SHOULD be supported, and AES in Counter mode, as
   described in [AESCTR], SHOULD be supported.  To provide data
   origin authentication and integrity with ESP, HMAC-SHA1 [RFC2404]
   SHOULD be supported, and AES in CBC MAC mode with XCBC extensions
   [AESXCBC] SHOULD be supported. DES in CBC mode SHOULD NOT be used
   due to its inherent weakness.  ESP with NULL encryption SHOULD be
   supported for authentication.

8.2.2  IPsec modes

   Conformant IP RDDP/RDMA security implementations SHOULD support
   ESP [RFC2406] in tunnel mode and MAY implement IPsec with ESP in
   transport mode.

8.2.3  IKE

   Conformant RDDP/RDMA security implementations SHOULD support IKE
   [RFC2409] for peer authentication, negotiation of security
   associations, and key management, using the IPsec DOI [RFC2407].
   Manual keying MUST NOT be used since it does not provide the
   necessary rekeying support.

   Conformant RDDP/RDMA security implementations SHOULD support peer
   authentication using a pre-shared secret, and MAY support
   certificate-based peer authentication using digital signatures.
   Peer authentication using the public key encryption methods
   outlined in IKE's sections 5.2 and 5.3 [RFC2409] SHOULD NOT be
   used.

   Conformant RDDP/RDMA security implementations SHOULD support IKE
   Main Mode and Aggressive Mode.  IKE Main Mode with pre-shared key
   authentication SHOULD NOT be used when either of the peers uses a
   dynamically assigned IP address. While Main Mode with pre-shared
   key authentication offers good security in many cases, situations
   where dynamically assigned addresses are used force use of a
   group pre-shared key, which is vulnerable to man-in-the-middle
   attack.  Since IKE Aggressive mode with pre-shared secret
   authentication is exposed to off-line dictionary attack if it is
   used then the selected pre-shared secrets must be random (or
   pseudo-random) strings not shorter than 128 bits.




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   When digital signatures are used for authentication, either IKE
   Main Mode or IKE Aggressive Mode MAY be used.  In all cases,
   access to locally stored secret information (pre-shared key, or
   private key for digital signing) must be suitably restricted,
   since compromise of the secret information nullifies the security
   properties of the IKE/IPsec protocols.

   When digital signatures are used to achieve authentication, an
   IKE negotiator SHOULD use IKE Certificate Request Payload(s) to
   specify the certificate authority (or authorities) that are
   trusted in accordance with its local policy.  IKE negotiators
   SHOULD check the pertinent Certificate Revocation List (CRL)
   before accepting a PKI certificate for use in IKE's
   authentication procedures.

   The IPsec DOI [RFC2407] provides for several types of
   identification data. Within IKE Phase 1, for use within the IDii
   and IDir payloads, conformant RDDP/RDMA security implementations
   SHOULD support the ID_IPV4_ADDR, ID_IPV6_ADDR (if the protocol
   stack supports IPv6) and ID_FQDN Identity Payloads. Identities
   other than ID_IPV4_ADDR and ID_IPV6_ADDR (such as ID_FQDN) SHOULD
   be employed in situations where Aggressive mode is utilized along
   with pre-shared keys and IP addresses are dynamically assigned.
   The IP Subnet, IP Address Range, ID_DER_ASN1_DN, ID_DER_ASN1_GN,
   and ID_USER_FQDN formats SHOULD NOT be used for RDDP/RDMA
   protocol security; The ID_KEY_ID Identity Payload MUST NOT be
   used.  As described in [RFC2407], within Phase 1 the ID port and
   protocol fields MUST be set to zero or to UDP port 500. Also, as
   noted in [RFC2407]: When an IKE exchange is authenticated using
   certificates (of any format), any ID's used for input to local
   policy decisions SHOULD be contained in the certificate used in
   the authentication of the exchange.

   The Phase 2 Quick Mode exchanges used by RDDP/RDMA protocol
   implementations SHOULD explicitly carry the Identity Payload
   fields (IDci and IDcr).  Each Phase 2 IDci and IDcr Payload
   SHOULD carry a single IP address (ID_IPV4_ADDR, ID_IPV6_ADDR) and
   SHOULD NOT use the IP Subnet or IP Address Range formats. Other
   ID payload formats MUST NOT be used.

   To support iSCSI PFS requirements [IPSSEC}, conformant RDDP/RDMA
   security implementation SHOULD support PFS in the rekeying
   process (i.e. in the Quick Mode exchange).

   Since IPsec acceleration hardware may only be able to handle a
   limited number of active IKE Phase 2 SAs, Phase 2 delete messages
   may be sent for idle SAs, as a means of keeping the number of
   active Phase 2 SAs to a minimum. The receipt of an IKE Phase 2
   delete message MUST NOT be interpreted as a reason for tearing
   down an RDDP/RDMA Stream. Rather, it is preferable to leave the
   Stream up, and if additional traffic is sent on it, to bring up



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   another IKE Phase 2 SA to protect it. This avoids the potential
   for continually bringing Streams up and down.

8.2.4  Security Policy Configuration

   One of the goals of this specification is to enable a high level
   of interoperability without requiring extensive configuration.
   This section provides guidelines on setting of IKE parameters so
   as to enhance the probability of a successful negotiation. It
   also describes how information on security policy configuration
   can be provided so as to further enhance the chances of success.

   To enhance the prospects for interoperability, some of the
   actions to consider include:

   [1]  Transform restriction. Since support for 3DES-CBC and HMAC-
   SHA1 is required of all implementations, offering these
   transforms enhances the probability of a successful negotiation.
   If AES-CTR [AESCTR] with XCBC-MAC [AESXCBC] is supported, this
   transform combination will typically be preferred, with 3DES-
   CBC/HMAC-SHA1 as a secondary offer.

   [2]  Group Restriction. If 3DES-CBC/HMAC-SHA1 is offered, and DH
   groups are offered, then it is recommended that a DH group of at
   least 1024 bits be offered along with it. If AES-CTR/XCBC-MAC is
   the preferred offer, and DH groups are offered, then it is
   recommended that a DH group of at least 2048 bits be offered
   along with it, as noted in [KeyLen]. If perfect forward secrecy
   is required in Quick Mode, then it is recommended that the QM PFS
   DH group be the same as the IKE Phase 1 DH group.  This reduces
   the total number of combinations, enhancing the chances for
   interoperability.

   [3]  Key lifetimes. If a key lifetime is offered that is longer
   than desired, then rather than causing the IKE negotiation to
   fail, it is recommended that the Responder consider the offered
   lifetime as a maximum, and accept it. The key can then use a
   lesser value for the lifetime, and utilize a Lifetime Notify in
   order to inform the other peer of lifetime expiration.

   Even when the above advice is taken, it still may be useful to be
   able to provide additional configuration information in order to
   enhance the chances of success, and it is useful to be able to
   manage security configuration regardless of the scale of the
   deployment.

   For example, it may be desirable to configure the security policy
   of an RDDP/RDMA device. This can be done manually or
   automatically via a security policy distribution mechanism.
   Alternatively, if the ULP supports a distribution mechanism such
   as iSCSI with iSNS or SLPv2, those mechanism can be used to
   supply security policy. If an IP block storage endpoint can


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   obtain the required security policy by other means (manually, or
   automatically via a security policy distribution mechanism) then
   it need not request this information through the ULP specific
   mechanism. However, if the required security policy configuration
   is not available via other mechanisms, those mechanismm can be
   used.

   It may also be helpful to obtain information about the
   preferences of the peer prior to initiating IKE.  While it is
   generally possible to negotiate security parameters within IKE,
   there are situations in which incompatible parameters can cause
   the IKE negotiation to fail.  The following information can be
   provided via ULP specific or other mechanisms:

   [4]  IPsec or cleartext support. The minimum piece of peer
   configuration required is whether an RDDP/RDMA endpoint requires
   IPsec or cleartext. This cannot be determined from the IKE
   negotiation alone without risking a long timeout, which is highly
   undesirable for the RDMA/DDP protocol.

   [5]  Perfect Forward Secrecy (PFS) support. It is helpful to know
   whether a peer allows PFS, since an IKE Phase 2 Quick Mode can
   fail if an initiator proposes PFS to a Responder that does not
   allow it.

   [6]  Preference for tunnel mode. While it is legal to propose
   both transport and tunnel mode within the same offer, not all IKE
   implementations will support this. As a result, it is useful to
   know whether a peer prefers tunnel mode or transport mode, so
   that it is possible to negotiate the preferred mode on the first
   try.

   [7]  Main Mode and Aggressive Mode support. Since the IKE
   negotiation can fail if a mode is proposed to a peer that doesn't
   allow it, it is helpful to know which modes a peer allows, so
   that an allowed mode can be negotiated on the first try.

   Since iSNS or SLPv2 can be used to distribute IPsec security
   policy and configuration information for use with IP block
   storage protocols and RDDP/RDMA, these discovery protocols would
   constitute a 'weak link' were they not secured at least as well
   as the protocols whose security they configure. Since the major
   vulnerability is packet modification and replay, when iSNS or

   SLPv2 are used to distribute security policy or configuration
   information, at a minimum, per-packet data origin authentication,
   integrity and replay protection MUST be used to protect the
   discovery protocol.






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9  Security considerations

   Issue: I think we should refer to IPS security considerations.
   Most of the issues discussed there are relevant for RDDP/RDMA as
   well (exceptions are the discussion on user certificates).<TBD>

















































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10 References

10.1 Normative References

   [RFC2828] Shirley, R., "Internet Security Glossary", FYI 36, RFC
       2828, May 2000.

   [DDP] Shah, H., J. Pinkerton, R.Recio, and P. Culley, "Direct
       Data Placement over Reliable Transports", Internet-Draft
       draft-ietf-rddp-ddp-01.txt, February 2003.

   [RDMAP] Recio, R., P. Culley, D. Garcia, J. Hilland, "An RDMA
       Protocol Specification", Internet-Draft draft-ietf-rddp-
       rdmap-01.txt, February 2003.

   [SEC-CONS] Rescorla, E., B. Korver, IAB, "Guidelines for Writing
       RFC Text on Security Considerations", Internet-Draft draft-
       ab-sec-cons-03.txt, January 2003.

   [RFC2246] T. Dierks, C. Allen, "The TLS Protocol Version 1.0",
   RFC 2246, January 1999.

   [RFC2401] Atkinson, R. and Kent, S., "Security Architecture for
       the Internet Protocol", RFC 2401, November 1998

   [RFC2402] Kent, S., Atkinson, R., "IP Authentication Header", RFC
       2402, November 1998

   [RFC2404] Madson, C., Glenn, R., "The Use of HMAC-SHA-1-96 within
       ESP and AH", RFC 2404, November 1998

   [RFC2406] Kent, S., Atkinson, R., "IP Encapsulating Security
       Payload (ESP)", RFC 2406, November 1998

   [RFC2407] Piper, D., "The Internet IP Security Domain of
       Interpretation of ISAKMP", RFC 2407, November 1998

   [RFC2408] Maughan, D., Schertler, M., Schneider, M., Turner, J.,
       "Internet Security Association and Key Management Protocol
       (ISAKMP), RFC 2408, November 1998

   [RFC2409] Harkins, D., Carrel, D., "The Internet Key Exchange
       (IKE)", RFC 2409, November 1998

   [AESCTR] Housley, R., "Using AES Counter Mode With IPsec
       ESP",Internet draft (work in progress), draft-ietf-ipsec-
       ciph-aes-ctr-05.txt, July 2003

   [KeyLen] Orman, H., Hoffman, P., "Determining Strengths For
       Public Keys Used For Exchanging Symmetric Keys", Internet
       draft (work in progress), draft-orman-public-key-lengths-
       07.txt, January 2004


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   [AESXCBC]   Frankel, S., Herbert, H., "The AES-XCBC-MAC-96
       Algorithm and Its Use with IPsec", Internet draft (work in
       progress), draft-ietf-ipsec-ciph-aes-xcbc-mac-02.txt, June
       2002

   [IPSSEC] Aboba B., et al, "Securing Block Storage Protocols over
       IP", Internet draft (work in progress), draft-ietf-ips-
       security-19.txt, January 2003

   [SCTP] R. Stewart et al., "Stream Control Transmission Protocol",
       RFC 2960, October 2000.

   [TCP] Postel, J., "Transmission Control Protocol - DARPA Internet
       Program Protocol Specification", RFC 793, September 1981.

10.2 Informative References

   [IPv6-Trust] Nikander, P., J.Kempf, E. Nordmark, "IPv6 Neighbor
       Discovery trust modelsTrust Models and threats", Internet-
       Draft draft-ietf-send-psreq-01.txt, January 2003.


































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11 Appendix A: Implementing Client/Server Protocols

   The prior sections outlined specific attacks and their
   countermeasures. This section summarizes the attacks and
   countermeasures defined in the prior section which are applicable
   to creation of a secure application server. An application server
   is defined as an application which must be able to communicate
   with many clients which do not trust each other and ensure that
   each client can not attack another client through server
   interactions.  Further, the server may wish to use multiple
   Streams to communicate with a specific client, and those Streams
   may share mutual trust.

   All of the prior section's details on attacks and countermeasures
   to protect a single Stream apply to the server. This section
   focuses on security issues where multiple clients are talking
   with a single server.

   The following list summarizes the relevent attacks that clients
   can mount on the shared server, by re-stating the previous
   RECOMMENDations to be client/server specific (the following are
   just restatements of the prior RECOMMENDations):

       *   Spoofing

           *   Section 7.2.4 Using an STag on a Different  on page
               23. To ensure that one client can not access another
               client's data via use of their STag, it is
               RECOMMENDED that the server either scope an STag to a
               single Stream or use a Protection Domain per client,
               or a combination of the two approaches.

       *   Tampering

           *   7.3.3 Multiple STags to access the same buffer on
               page 25. See the following bullet's discussion of
               Section 7.4.6.

       *   Information Disclosure

           *   7.4.2 Using RDMA Read to Access Stale Data on page
               26. It is RECOMMENDED that the server ensure that no
               stale data is contained in a buffer before remote
               read access rights are granted to a client (this can
               be done by zeroing the contents of the memory, for
               example).

           *   7.4.5 RDMA Read into an RDMA Write Buffer on page 27.
               It is RECOMMENDED that if a server only intends a
               buffer to be exposed for remote write access, it set
               the access rights to the buffer to only enable remote
               write access.


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           *   7.4.6 Using Multiple STags to Access One Buffer on
               page 27. It is RECOMMENDED that separate clients not
               be granted write access to the same buffer through
               different STags. A buffer should be exposed to only
               one client at a time to ensure that no information
               disclosure or information tampering occurs between
               peers.

       *   Denial of Service

           *   7.5.1 RNIC Resource Consumption on page 29. It is
               RECOMMENDED that the server place the allocation of
               all scarce resources be placed under the control of a
               Privileged Resource Manager.

           *   7.5.2.1 Multiple Streams Sharing Receive Buffers on
               page 30. If an RNIC Engine provides the ability to
               share receive buffers across multiple Streams, it is
               RECOMMENDED that it enable the server to detect if
               the client is attempting to consume more than its
               fair share of resources so that the server can apply
               countermeasures to detect and prevent the attack.

           *   7.5.2.2 Local Peer Attacking a Shared CQ on page 31.
               Sharing a CQ across Streams that belong to different
               Protection Domains is NOT RECOMMENDED.

           *   7.5.2.3 Remote Peer Attacking a Shared CQ on page 32.
               If a server allows the client to influence CQ entry
               resource allocation, then it is RECOMMENDED that the
               CQ be isolated to Streams within a single Protection
               Domain (i.e. streams that share Partial Mutual
               Trust).

               It is RECOMMENDED that the Local Peer implement a
               mechanism to ensure that the Completion Queue can not
               overflow.

           *   7.5.2.4 RDMA Read Request Queue on page 34. It is
               RECOMMENDED that access to interfaces that allocate
               RDMA Read Request Queue entries be restricted to a
               trusted Local Peer, such as a Privileged Resource
               Manager.

               It is RECOMMENDED that RDMA Read Request Queue
               resource consumption be controlled such that
               RDMAP/DDP Streams which do not share Partial Mutual
               Trust do not share RDMA Read Request Queue resources.

           *   7.5.3 Resource Consumption by Idle Applications on
               page 35. Refer to Section 7.5.1.



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           *   7.5.5 RI an STag Shared on Multiple Streams on page
               36. If RDDP Streams do not share Partial Mutual Trust
               (i.e. the client may attempt to invalidate the STag
               prematurely), it is NOT RECOMMENDED that the server
               allow an STag to be valid across multiple Streams.

















































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12 Appendix B: Summary Table of Attacks

   Issue: Finish Summary table of Attacks/Trust Models <TBD>


   <editor: This section is under construction, and will be
   completed in a future version of this document>

   Rows are the attack (grouped into categories)

   Columns are the:

       *   Sec - Section the attack is discussed

       *   Attack Name - short name for the attack

       *   Threat - threat type (Spoof (Spoofing), Tamp (Tampering),
           ID (Information Disclosure), and DOS (Denial of Service))

       *   SH û Does the threat assume there are shared resources
           (yes/no/NA û not applicable)?

       *   TR û Does the threat assume there is Partial Mutual Trust
           between Streams (MT), no trust between Streams (NT), or
           is this parameter not applicable (NA)?





























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12.1 Spoofing

+--------+---------------------------------------------+-----+--+--+
|  Sec   | Attack Name                                 |Sh|TR|
+--------+---------------------------------------------+-----+--+--+
| 7.2.1  | Impersonation                               |NA|NA|
+--------+---------------------------------------------+-----+--+--+
| 7.2.2  | Stream Hijacking                            |NA|NA|
+--------+---------------------------------------------+-----+--+--+
| 7.2.3  | Man in the Middle Attack                    |NA|NA|
+--------+---------------------------------------------+-----+--+--+
| 7.2.4  | Using an STag on a Different                |Y |NT|
+--------+---------------------------------------------+-----+--+--+

12.2 Tampering

+--------+---------------------------------------------+-----+--+--+
| 7.3.1  | Buffer Overrun - RDMA Write or Read Response|NA|NT|
+--------+---------------------------------------------+-----+--+--+
| 7.3.2  | Modifying a Buffer After Indication         |NA|NT|
+--------+---------------------------------------------+-----+--+--+
| 7.3.3  | Multiple STags to access the same buffer    |Y |NT|
+--------+---------------------------------------------+-----+--+--+
| 7.3.4  | Network based modification of buffer content|NA|NA|
+--------+---------------------------------------------+-----+--+--+

12.3 Information Disclosure

+--------+---------------------------------------------+-----+--+--+
| 7.4.1  | Probing memory outside of the buffer bounds |NA|NT|
+--------+---------------------------------------------+-----+--+--+
| 7.4.2  | Using RDMA Read to Access Stale Data        |
+--------+---------------------------------------------+-----+--+--+
| 7.4.3  | Accessing a Buffer After the Transfer       |
+--------+---------------------------------------------+-----+--+--+
| 7.4.4  | Accessing Unintended Data With a Valid STag |
+--------+---------------------------------------------+-----+--+--+
| 7.4.5  | RDMA Read into an RDMA Write Buffer         |
+--------+---------------------------------------------+-----+--+--+
| 7.4.6  | Using Multiple STags to Access One Buffer   |
+--------+---------------------------------------------+-----+--+--+
| 7.4.7  | Remote Node Loading Firmware onto the RNIC  |
+--------+---------------------------------------------+-----+--+--+
| 7.4.8  | Controlling Access to PTT & STag Mapping    |
+--------+---------------------------------------------+-----+--+--+
| 7.4.9  | Network based eaves dropping                |
+--------+---------------------------------------------+-----+--+--+

12.4 Denial of Service

+--------+---------------------------------------------+-----+--+--+
| 7.5.1  | RNIC Resource Consumption                   |


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+--------+---------------------------------------------+-----+--+--+
| 7.5.2.1| Multiple Streams Sharing Receive Buffers    |
+--------+---------------------------------------------+-----+--+--+
| 7.5.2.2| Local Peer Attacking a Shared CQ            |Error!
Reference source not found.
+--------+---------------------------------------------+-----+--+--+
| 7.5.2.3| Remote Peer Attacking a Shared CQ           |
+--------+---------------------------------------------+-----+--+--+
| 7.5.2.4| RDMA Read Request Queue                     |
+--------+---------------------------------------------+-----+--+--+
| 7.5.3 | Resource Consumption by Idle Applications    |
+--------+---------------------------------------------+-----+--+--+
| 7.5.4 | Exercise of non-optimal code paths           |
+--------+---------------------------------------------+-----+--+--+
| 7.5.5 | RI an STag Shared on Multiple Streams        |
+--------+---------------------------------------------+-----+--+--+
| 7.5.6 | Remote Peer Consumes Untagged Receive Buffers|
+--------+---------------------------------------------+-----+--+--+

                 Figure 2 - Summary Attacks and Trust Model Table


































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13 Appendix C: Partial Trust Taxonomy

   Partial Trust is defined as when one party is willing to assume
   that another party will refrain from a specific attack or set of
   attacks, the parties are said to be in a state of Partial Trust.
   Note that the partially trusted peer may attempt a different set
   of attacks. This may be appropriate for many applications where
   any adverse effects of the betrayal is easily confined and does
   not place other clients or applications at risk.

   The Trust Models described in this section have three primary
   distinguishing characteristics. The Trust Model refers to a Local
   Peer and Remote Peer, which are the local and remote application
   instances communicating via RDMA/DDP.

       *   Local Resource Sharing (yes/no) - When local resources
           are shared, they are shared across a grouping of
           RDMAP/DDP Streams. If local resources are not shared, the
           resources are dedicated on a per Stream basis. Resources
           are defined in Section 4.2 - Resources on page 11. The
           advantage of not sharing resources between Streams is
           that it reduces the types of attacks that are possible.
           The disadvantage is that applications might run out of
           resources.

       *   Local Partial Trust (yes/no) - Local Partial Trust is
           determined based on whether the local grouping of
           RDMAP/DDP Streams (which typically equates to one
           application or group of applications) mutually trust each
           other to not perform a specific set of attacks.

       *   Remote Partial Trust (yes/no) - The Remote Partial Trust
           level is determined based on whether the Local Peer of a
           specific RDMAP/DDP Stream partially trusts the Remote
           Peer of the Stream (see the definition of Partial Trust
           in Section 3 Introduction).

   Not all of the combinations of the trust characteristics are
   expected to be used by applications. This paper specifically
   analyzes five application Trust Models that are expected to be in
   common use. The Trust Models are as follows:

   1.  NS-NT - Non-Shared Local Resources, no Local Trust, no Remote
       Trust - typically a server application that wants to run in
       the safest mode possible. All attack mitigations are in place
       to ensure robust operation.

   2.  NS-RT - Non-Shared Local Resources, no Local Trust, Remote
       Partial Trust - typically a peer-to-peer application, which
       has, by some method outside of the scope of this
       specification, authenticated the Remote Peer. Note that
       unless some form of key based authentication is used on a per


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       RDMA/DDP session basis, it may not be possible be possible
       for man-in-the-middle attacks to occur. See section 8,
       Security Services for RDDP on page 38.

   3.  S-NT - Shared Local Resources, no Local Trust, no Remote
       Trust - typically a server application that runs in an
       untrusted environment where the amount of resources required
       is either too large or too dynamic to dedicate for each
       RDMAP/DDP Stream.

   4.  S-LT - Shared Local Resources, Local Partial Trust, no Remote
       Trust - typically an application, which provides a session
       layer and uses multiple Streams, to provide additional
       throughput or fail-over capabilities. All of the Streams
       within the local application partially trust each other, but
       do not trust the Remote Peer. This trust model may be
       appropriate for embedded environments.

   5.  S-T - Shared Local Resources, Local Partial Trust, Remote
       Partial Trust - typically a distributed application, such as
       a distributed database application or a High Performance
       Computer (HPC) application, which is intended to run on a
       cluster. Due to extreme resource and performance
       requirements, the application typically authenticates with
       all of its peers and then runs in a highly trusted
       environment. The application peers are all in a single
       application fault domain and depend on one another to be
       well-behaved when accessing data structures. If a trusted
       Remote Peer has an implementation defect that results in poor
       behavior, the entire application could be corrupted.

   Models NS-NT and S-NT above are typical for Internet networking -
   neither Local Peers nor the Remote Peer is trusted. Sometimes
   optimizations can be done that enable sharing of Page Translation
   Tables across multiple Local Peers, thus Model S-LT can be
   advantageous. Model S-T is typically used when resource scaling
   across a large parallel application makes it infeasible to use
   any other model. Resource scaling issues can either be due to
   performance around scaling or because there simply are not enough
   resources. Model NS-RT is probably the least likely model to be
   used, but is presented for completeness.













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14 AuthorÆs Addresses

   James Pinkerton

   Microsoft Corporation

   One Microsoft Way
   Redmond, WA. 98052 USA
   Phone: +1 (425) 705-5442
   Email: jpink@windows.microsoft.com

   Ellen Deleganes

   Intel Corporation

   MS JF5-355
   2111 NE 25th Ave.
   Hillsboro, OR 97124 USA
   Phone: +1 (503) 712-4173
   Email: ellen.m.deleganes@intel.com

   Allyn Romanow
   Cisco Systems
   170 W Tasman Drive
   San Jose, CA 95134 USA
   Phone: +1 408 525 8836
   Email: allyn@cisco.com



   Sara Bitan
   Microsoft Corporation
   Email: sarab@microsoft.com





















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15 Acknowledgments

   Catherine Meadows
   Naval Research Laboratory
   Code 5543
   Washington, DC 20375
   Email: meadows@itd.nrl.navy.mil

   Patricia Thaler
   Agilent Technologies, Inc.
   1101 Creekside Ridge Drive, #100
   M/S-RG10
   Roseville, CA 95678
   Phone: +1-916-788-5662
   email: pat_thaler@agilent.com

   James Livingston
   NEC Solutions (America), Inc.
   7525 166th Ave. N.E., Suite D210
   Redmond, WA 98052-7811
   Phone: +1 (425) 897-2033
   Email: james.livingston@necsam.com

   John Carrier
   Adaptec, Inc.
   691 S. Milpitas Blvd.
   Milpitas, CA 95035 USA
   Phone: +1 (360) 378-8526
   Email: john_carrier@adaptec.com

   Caitlin Bestler
   Email: cait@asomi.com

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA. 98052 USA
   Phone: +1 (425) 706-6606
   Email: bernarda@windows.microsoft.com















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16 Full Copyright Statement

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

   This document and translations of it may be copied and furnished
   to others, and derivative works that comment on or otherwise
   explain it or assist in its implementation may be prepared,
   copied, published and distributed, in whole or in part, without
   restriction of any kind, provided that the above copyright notice
   and this paragraph are included on all such copies and derivative
   works.  However, this document itself may not be modified in any
   way, such as by removing the copyright notice or references to
   the Internet Society or other Internet organizations, except as
   needed for the purpose of developing Internet standards in which
   case the procedures for copyrights defined in the Internet
   Standards process must be followed, or as required to translate
   it into languages other than English.

   The limited permissions granted above are perpetual and will not
   be revoked by the Internet Society or its successors or assigns.

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   J. Pinkerton, et al.    Expires - September 2004         [Page 58]


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