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rfc:rfc6680

Internet Engineering Task Force (IETF) N. Williams Request for Comments: 6680 Cryptonector, LLC Category: Standards Track L. Johansson ISSN: 2070-1721 SUNET

                                                            S. Hartman
                                                     Painless Security
                                                          S. Josefsson
                                                                SJD AB
                                                           August 2012
Generic Security Service Application Programming Interface (GSS-API)
                         Naming Extensions

Abstract

 The Generic Security Service Application Programming Interface
 (GSS-API) provides a simple naming architecture that supports name-
 based authorization.  This document introduces new APIs that extend
 the GSS-API naming model to support name attribute transfer between
 GSS-API peers.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6680.

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of

Williams, et al. Standards Track [Page 1] RFC 6680 GSS-API Naming Extensions August 2012

 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
 3.  Name Attribute Authenticity  . . . . . . . . . . . . . . . . .  4
 4.  Name Attributes/Values as ACL Subjects . . . . . . . . . . . .  4
 5.  Naming Contexts  . . . . . . . . . . . . . . . . . . . . . . .  4
 6.  Representation of Attribute Names  . . . . . . . . . . . . . .  6
 7.  API  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   7.1.  SET OF OCTET STRING  . . . . . . . . . . . . . . . . . . .  7
   7.2.  Const Types  . . . . . . . . . . . . . . . . . . . . . . .  8
   7.3.  GSS_Display_name_ext() . . . . . . . . . . . . . . . . . .  8
     7.3.1.  C-Bindings . . . . . . . . . . . . . . . . . . . . . .  9
   7.4.  GSS_Inquire_name() . . . . . . . . . . . . . . . . . . . .  9
     7.4.1.  C-Bindings . . . . . . . . . . . . . . . . . . . . . . 10
   7.5.  GSS_Get_name_attribute() . . . . . . . . . . . . . . . . . 10
     7.5.1.  C-Bindings . . . . . . . . . . . . . . . . . . . . . . 11
   7.6.  GSS_Set_name_attribute() . . . . . . . . . . . . . . . . . 12
     7.6.1.  C-Bindings . . . . . . . . . . . . . . . . . . . . . . 13
   7.7.  GSS_Delete_name_attribute()  . . . . . . . . . . . . . . . 14
     7.7.1.  C-Bindings . . . . . . . . . . . . . . . . . . . . . . 14
   7.8.  GSS_Export_name_composite()  . . . . . . . . . . . . . . . 14
     7.8.1.  C-Bindings . . . . . . . . . . . . . . . . . . . . . . 15
 8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
 9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   10.1. Normative References . . . . . . . . . . . . . . . . . . . 17
   10.2. Informative References . . . . . . . . . . . . . . . . . . 17

Williams, et al. Standards Track [Page 2] RFC 6680 GSS-API Naming Extensions August 2012

1. Introduction

 As described in [RFC4768], the GSS-API's naming architecture suffers
 from certain limitations.  This document attempts to overcome these
 limitations.
 A number of extensions to the GSS-API [RFC2743] and its C-bindings
 [RFC2744] are described herein.  The goal is to make information
 modeled as "name attributes" available to applications.  Such
 information MAY, for instance, be used by applications to make
 authorization decisions.  For example, Kerberos V authorization data
 elements, both in their raw forms as well as mapped to more useful
 value types, can be made available to GSS-API applications through
 these interfaces.
 The model is that GSS names have attributes.  The attributes of a
 name may be authenticated (e.g., an X509 attribute certificate or
 signed Security Assertion Markup Language (SAML) attribute assertion)
 or may have been set on a GSS name for the purpose of locally
 "asserting" the attribute during credential acquisition or security
 context exchange.  Name attributes' values are network
 representations thereof (e.g., the actual value octets of the
 contents of an X.509 certificate extension, for example) and are
 intended to be useful for constructing portable access control
 facilities.  Applications may often require language- or platform-
 specific data types, rather than network representations of name
 attributes, so a function is provided to obtain objects of such types
 associated with names and name attributes.
 Future updates of this specification may involve adding an attribute
 namespace for attributes that only have application-specific
 semantics.  Note that mechanisms will still need to know how to
 transport such attributes.  The IETF may also wish to add functions
 by which to inquire whether a mechanism(s) understands a given
 attribute name or namespace and to list which attributes or attribute
 namespaces a mechanism understands.  Finally, the IETF may want to
 consider adding a function by which to determine the name of the
 issuer of a name attribute.

2. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

Williams, et al. Standards Track [Page 3] RFC 6680 GSS-API Naming Extensions August 2012

3. Name Attribute Authenticity

 An attribute is "authenticated" if and only if there is a secure
 association between the attribute (and its values) and the trusted
 source of the peer credential.  Examples of authenticated attributes
 are (any part of) the signed portion of an X.509 certificate or
 AD-KDCIssued authorization data elements (Section 5.2.6.2 of
 [RFC4120]) in Kerberos V Tickets, provided, of course, that the
 authenticity of the respective security associations (e.g.,
 signatures) has been verified.
 Note that the fact that an attribute is authenticated does not imply
 anything about the semantics of the attribute nor that the trusted
 credential source was authorized to assert the attribute.  Such
 interpretations SHOULD be the result of applying local policy to the
 attribute.
 An unauthenticated attribute is called _asserted_ in what follows.
 This is not to be confused with other uses of the words "asserted" or
 "assertion" such as "SAML attribute assertion", the attributes of
 which may be authenticated in the sense of this document, for
 instance, if the SAML attribute assertion was signed by a key trusted
 by the peer.

4. Name Attributes/Values as ACL Subjects

 To facilitate the development of portable applications that make use
 of name attributes to construct and evaluate portable Access Control
 Lists (ACLs), the GSS-API makes name attribute values available in
 canonical network encodings thereof.

5. Naming Contexts

 Several factors influence the context in which a name attribute is
 interpreted.  One is the trust context.
 As discussed previously, applications apply local policy to determine
 whether a particular peer credential issuer is trusted to make a
 given statement.  Different GSS-API mechanisms and deployments have
 different trust models surrounding attributes they provide about a
 name.
 For example, Kerberos deployments in the enterprise typically trust a
 Key Distribution Center (KDC) to make any statement about principals
 in a realm.  This includes attributes such as group membership.

Williams, et al. Standards Track [Page 4] RFC 6680 GSS-API Naming Extensions August 2012

 In contrast, in a federated SAML environment, the identity provider
 typically exists in a different organization than the acceptor.  In
 this case, the set of group memberships or entitlements that the IDP
 is permitted to make needs to be filtered by the policy of the
 acceptor and federation.
 So even an attribute containing the same information, such as email
 address, would need to be treated differently by the application in
 the context of an enterprise deployment from the context of a
 federation.
 Another aspect related to trust is the role of the credential issuer
 in providing the attribute.  Consider Public Key Cryptography for
 Initial Authentication in Kerberos (PKINIT) [RFC4556].  In this
 protocol, a public key and associated certificate are used to
 authenticate to a Kerberos KDC.  Consider how attributes related to a
 PKINIT certificate should be made available in GSS-API
 authentications based on the Kerberos ticket.  In some deployments,
 the certificate may be fully trusted; by including the certificate
 information in the ticket, the KDC permits the acceptor to trust the
 information in the certificate just as if the KDC itself had made
 these statements.  In other deployments, the KDC may have authorized
 a hash of the certificate without evaluating the content of the
 certificate or generally trusting the issuing certification
 authority.  In this case, if the certificate were included in the
 issued ticket, the KDC would only be making the statement that the
 certificate was used in the authentication.  This statement would be
 authenticated but would not imply that the KDC asserted that
 particular attributes of the certificate accurately described the
 initiator.
 Another aspect of context is encoding of the attribute information.
 An attribute containing an ASCII [ANSI.X3-4.1986] or UTF-8 [RFC3629]
 version of an email address could not be interpreted the same as an
 ASN.1 Distinguished Encoding Rules email address in a certificate.
 All of these contextual aspects of a name attribute affect whether
 two attributes can be treated the same by an application and thus
 whether they should be considered the same name attribute.  In the
 GSS-API naming extensions, attributes that have different contexts
 MUST have different names so they can be distinguished by
 applications.  As an unfortunate consequence of this requirement,
 multiple attribute names will exist for the same basic information.
 That is, there is no single attribute name for the email address of
 an initiator.  Other aspects of how mechanisms describe information
 about subjects would already make this true.  For example, some
 mechanisms use OIDs to name attributes; others use URIs.

Williams, et al. Standards Track [Page 5] RFC 6680 GSS-API Naming Extensions August 2012

 Local implementations or platforms are likely to have sufficient
 policy and information to know when contexts can be treated as the
 same.  For example, the GSS-API implementation may know that a
 particular certification authority can be trusted in the context of a
 PKINIT authentication.  The local implementation may have sufficient
 policy to know that a particular credential issuer is trusted to make
 a given statement.  In order to take advantage of this local
 knowledge within the GSS-API implementation, naming extensions
 support the concept of local attributes in addition to standard
 attributes.  For example, an implementation might provide a local
 attribute for email address.  The implementation would specify the
 encoding and representation of this attribute; mechanism-specific
 standards attributes would be re-encoded if necessary to meet this
 representation.  Only email addresses in contexts that meet the
 requirements of local policy would be mapped into this local
 attribute.
 Such local attributes inherently expose a trade-off between
 interoperability and usability.  Using a local attribute in an
 application requires knowledge of the local implementation.  However,
 using a standardized attribute in an application requires more
 knowledge of policy and more validation logic in the application.
 Sharing this logic in the local platform provides more consistency
 across applications as well as reduces implementation costs.  Both
 options are needed.

6. Representation of Attribute Names

 Different underlying mechanisms (e.g., SAML or X.509 certificates)
 provide different representations for the names of their attributes.
 In X.509 certificates, most objects are named by object identifiers
 (OIDs).  The type of object (certificate extension, name constraint,
 keyPurposeID, etc.) along with the OID is sufficient to identify the
 attribute.  By contrast, according to Sections 8.2 and 2.7.3.1 of
 [OASIS.saml-core-2.0-os], the name of an attribute has two parts.
 The first is a URI describing the format of the name.  The second
 part, whose form depends on the format URI, is the actual name.  In
 other cases, an attribute might represent a certificate that plays
 some particular role in a GSS-API mechanism; such attributes might
 have a simple mechanism-defined name.
 Attribute names MUST support multiple components.  If there is more
 than one component in an attribute name, the more significant
 components define the semantics of the less significant components.

Williams, et al. Standards Track [Page 6] RFC 6680 GSS-API Naming Extensions August 2012

 Attribute names are represented as OCTET STRING elements in the API
 described below.  These attribute names have syntax and semantics
 that are understood by the application and by the lower-layer
 implementations (some of which are described below).
 If an attribute name contains a space (ASCII 0x20), the first space
 separates the most significant or primary component of the name from
 the remainder.  We may refer to the primary component of the
 attribute name as the attribute name's "prefix".  If there is no
 space, the primary component is the entire name; otherwise, it
 defines the interpretation of the remainder of the names.
 If the primary component contains a ":" (ASCII 0x3a), then the
 primary component is a URI.  Otherwise, the attribute is a local
 attribute and the primary component has meaning to the implementation
 of GSS-API or to the specific configuration of the application.
 Local attribute names with an "at" sign ("@") in them are reserved
 for future allocation by the IETF.
 Since attribute names are split at the first space into prefix and
 suffix, there is a potential for ambiguity if a mechanism blindly
 passes through a name attribute whose name it does not understand.
 In order to prevent such ambiguities, the mechanism MUST always
 prefix raw name attributes with a prefix that reflects the context of
 the attribute.
 Local attribute names under the control of an administrator or a
 sufficiently trusted part of the platform need not have a prefix to
 describe context.

7. API

7.1. SET OF OCTET STRING

 The construct "SET OF OCTET STRING" occurs once in RFC 2743
 [RFC2743], where it is used to represent a set of status strings in
 the GSS_Display_status call.  The Global Grid Forum has defined SET
 OF OCTET STRING as a buffer set type in GFD.024 [GFD.024], which also
 provides one API for memory management of these structures.  The
 normative reference to GFD.024 [GFD.024] is for the buffer set
 functions defined in Section 2.5 and the associated buffer set C
 types defined in Section 6 (namely gss_buffer_set_desc,
 gss_buffer_set_t, gss_create_empty_buffer_set,
 gss_add_buffer_set_member, gss_release_buffer_set).  Nothing else
 from GFD.024 is required to implement this document.  In particular,
 that document specifies changes to the behavior of existing GSS-API

Williams, et al. Standards Track [Page 7] RFC 6680 GSS-API Naming Extensions August 2012

 functions in Section 3: implementing those changes are not required
 to implement this document.  Any implementation of SET OF OCTET
 STRING for use by this specification MUST preserve order.

7.2. Const Types

 The C-bindings for the new APIs use some types from [RFC5587] to
 avoid issues with the use of "const".  The normative reference to
 [RFC5587] is for the C types specified in Figure 1 of Section 3.4.6.
 Nothing else from that document is required to implement this
 document.

7.3. GSS_Display_name_ext()

 Inputs:
 o  name INTERNAL NAME
 o  display_as_name_type OBJECT IDENTIFIER
 Outputs:
 o  major_status INTEGER
 o  minor_status INTEGER
 o  display_name OCTET STRING -- caller must release with
    GSS_Release_buffer()
 Return major_status codes:
 o  GSS_S_COMPLETE indicates no error.
 o  GSS_S_UNAVAILABLE indicates that the given name could not be
    displayed using the syntax of the given name type.
 o  GSS_S_FAILURE indicates a general error.
 This function displays a given name using the given name syntax, if
 possible.  This operation may require mapping Mechanism Names (MNs)
 to generic name syntaxes or generic name syntaxes to mechanism-
 specific name syntaxes.  Such mappings may not always be feasible and
 MAY be inexact or lossy; therefore, this function may fail.

Williams, et al. Standards Track [Page 8] RFC 6680 GSS-API Naming Extensions August 2012

7.3.1. C-Bindings

 The display_name buffer is de-allocated by the caller with
 gss_release_buffer.
 OM_uint32 gss_display_name_ext(
   OM_uint32                     *minor_status,
   gss_const_name_t              name,
   gss_const_OID                 display_as_name_type,
   gss_buffer_t                  display_name
 );

7.4. GSS_Inquire_name()

 Inputs:
 o  name INTERNAL NAME
 Outputs:
 o  major_status INTEGER
 o  minor_status INTEGER
 o  name_is_MN BOOLEAN
 o  mn_mech OBJECT IDENTIFIER
 o  attrs SET OF OCTET STRING -- the caller is responsible for de-
    allocating memory using GSS_Release_buffer_set
 Return major_status codes:
 o  GSS_S_COMPLETE indicates no error.
 o  GSS_S_FAILURE indicates a general error.
 This function outputs the set of attributes of a name.  It also
 indicates if a given name is an Mechanism Name (MN) or not and, if it
 is, the mechanism of which it's an MN.

Williams, et al. Standards Track [Page 9] RFC 6680 GSS-API Naming Extensions August 2012

7.4.1. C-Bindings

 OM_uint32 gss_inquire_name(
   OM_uint32                     *minor_status,
   gss_const_name_t              name,
   int                           *name_is_MN,
   gss_OID                       *MN_mech,
   gss_buffer_set_t              *attrs
 );
 The gss_buffer_set_t is used here as the C representation of SET OF
 OCTET STRING.  This type is used to represent a set of attributes and
 is a NULL-terminated array of gss_buffer_t.  The gss_buffer_set_t
 type and associated API is defined in GFD.024 [GFD.024].  The "attrs"
 buffer set is de-allocated by the caller using
 gss_release_buffer_set().

7.5. GSS_Get_name_attribute()

 Inputs:
 o  name INTERNAL NAME
 o  attr OCTET STRING
 Outputs:
 o  major_status INTEGER
 o  minor_status INTEGER
 o  authenticated BOOLEAN -- TRUE if and only if authenticated by the
    trusted peer credential source
 o  complete BOOLEAN -- TRUE if and only if this represents a complete
    set of values for the name
 o  values SET OF OCTET STRING -- the caller is responsible for de-
    allocating memory using GSS_Release_buffer_set
 o  display_values SET OF OCTET STRING -- the caller is responsible
    for de-allocating memory using GSS_Release_buffer_set
 Return major_status codes:
 o  GSS_S_COMPLETE indicates no error.

Williams, et al. Standards Track [Page 10] RFC 6680 GSS-API Naming Extensions August 2012

 o  GSS_S_UNAVAILABLE indicates that the given attribute OID is not
    known or set.
 o  GSS_S_FAILURE indicates a general error.
 This function outputs the value(s) associated with a given GSS name
 object for a given name attribute.
 The complete flag denotes that (if TRUE) the set of values represents
 a complete set of values for this name.  The peer being an
 authoritative source of information for this attribute is a
 sufficient condition for the complete flag to be set by the peer.
 In the federated case, when several peers may hold some of the
 attributes about a name, this flag may be highly dangerous and SHOULD
 NOT be used.
 NOTE: This function relies on the GSS-API notion of "SET OF" allowing
 for order preservation; this has been discussed on the KITTEN WG
 mailing list, and the consensus seems to be that, indeed, that was
 always the intention.  It should be noted, however, that the order
 presented does not always reflect an underlying order of the
 mechanism-specific source of the attribute values.

7.5.1. C-Bindings

 The C-bindings of GSS_Get_name_attribute() require one function call
 per attribute value for multi-valued name attributes.  This is done
 by using a single gss_buffer_t for each value and an input/output
 integer parameter to distinguish initial and subsequent calls and to
 indicate when all values have been obtained.
 The "more" input/output parameter should point to an integer variable
 whose value, on first call to gss_get_name_attribute(), MUST be -1
 and whose value upon function call return will be non-zero to
 indicate that additional values remain or zero to indicate that no
 values remain.  The caller should not modify this parameter after the
 initial call.  The status of the complete and authenticated flags
 MUST NOT change between multiple calls to iterate over values for an
 attribute.
 The output buffers "value" and "display_value" are de-allocated by
 the caller using gss_release_buffer().

Williams, et al. Standards Track [Page 11] RFC 6680 GSS-API Naming Extensions August 2012

 OM_uint32 gss_get_name_attribute(
   OM_uint32                     *minor_status,
   gss_const_name_t              name,
   gss_const_buffer_t            attr,
   int                           *authenticated,
   int                           *complete,
   gss_buffer_t                  value,
   gss_buffer_t                  display_value,
   int                           *more
 );

7.6. GSS_Set_name_attribute()

 Inputs:
 o  name INTERNAL NAME
 o  complete BOOLEAN -- TRUE if and only if this represents a complete
    set of values for the name
 o  attr OCTET STRING
 o  values SET OF OCTET STRING
 Outputs:
 o  major_status INTEGER
 o  minor_status INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates no error.
 o  GSS_S_UNAVAILABLE indicates that the given attribute NAME is not
    known or could not be set.
 o  GSS_S_FAILURE indicates a general error.
 When the given NAME object is an MN, this function MUST fail (with
 GSS_S_FAILURE) if the mechanism for which the name is an MN does not
 recognize the attribute name or the namespace it belongs to.  This is
 because name attributes generally have some semantics that mechanisms
 must understand.
 On the other hand, when the given name is not an MN, this function
 MAY succeed even if none of the available mechanisms understand the
 given attribute, in which subsequent credential acquisition attempts

Williams, et al. Standards Track [Page 12] RFC 6680 GSS-API Naming Extensions August 2012

 (via GSS_Acquire_cred() or GSS_Add_cred()) with the resulting name
 MUST fail for mechanisms that do not understand any one or more name
 attributes set with this function.  Applications may wish to use a
 non-MN, then acquire a credential with that name as the desired name.
 The acquired credentials will have elements only for the mechanisms
 that can carry the name attributes set on the name.
 Note that this means that all name attributes are locally critical:
 the mechanism(s) must understand them.  The reason for this is that
 name attributes must necessarily have some meaning that the mechanism
 must understand, even in the case of application-specific attributes
 (in which case the mechanism must know to transport the attribute to
 any peer).  However, there is no provision to ensure that peers
 understand any given name attribute.  Individual name attributes may
 be critical with respect to peers, and the specification of the
 attribute will have to indicate whether the mechanism's protocol or
 the application is expected to enforce criticality.
 The complete flag denotes that (if TRUE) the set of values represents
 a complete set of values for this name.  The peer being an
 authoritative source of information for this attribute is a
 sufficient condition for the complete flag to be set by the peer.
 In the federated case, when several peers may hold some of the
 attributes about a name, this flag may be highly dangerous and SHOULD
 NOT be used.
 NOTE: This function relies on the GSS-API notion of "SET OF" allowing
 for order preservation; this has been discussed on the KITTEN WG
 mailing list, and the consensus seems to be that, indeed, that was
 always the intention.  It should be noted that underlying mechanisms
 may not respect the given order.

7.6.1. C-Bindings

 The C-bindings of GSS_Set_name_attribute() requires one function call
 per attribute value for multi-valued name attributes.  Each call adds
 one value.  To replace an attribute's every value, delete the
 attribute's values first with GSS_Delete_name_attribute().
 OM_uint32 gss_set_name_attribute(
   OM_uint32                     *minor_status,
   gss_const_name_t              name,
   int                           complete,
   gss_const_buffer_t            attr,
   gss_const_buffer_t            value
 );

Williams, et al. Standards Track [Page 13] RFC 6680 GSS-API Naming Extensions August 2012

7.7. GSS_Delete_name_attribute()

 Inputs:
 o  name INTERNAL NAME
 o  attr OCTET STRING
 Outputs:
 o  major_status INTEGER
 o  minor_status INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates no error.
 o  GSS_S_UNAVAILABLE indicates that the given attribute NAME is not
    known.
 o  GSS_S_UNAUTHORIZED indicates that a forbidden delete operation was
    attempted, such as deleting a negative attribute.
 o  GSS_S_FAILURE indicates a general error.
 Deletion of negative authenticated attributes from NAME objects MUST
 NOT be allowed and must result in a GSS_S_UNAUTHORIZED.

7.7.1. C-Bindings

 OM_uint32 gss_delete_name_attribute(
   OM_uint32                     *minor_status,
   gss_const_name_t              name,
   gss_const_buffer_t            attr
 );

7.8. GSS_Export_name_composite()

 Inputs:
 o  name INTERNAL NAME
 Outputs:
 o  major_status INTEGER
 o  minor_status INTEGER

Williams, et al. Standards Track [Page 14] RFC 6680 GSS-API Naming Extensions August 2012

 o  exp_composite_name OCTET STRING -- the caller is responsible for
    de-allocating memory using GSS_Release_buffer
 Return major_status codes:
 o  GSS_S_COMPLETE indicates no error.
 o  GSS_S_FAILURE indicates a general error.
 This function outputs a token that can be imported with
 GSS_Import_name(), using GSS_C_NT_COMPOSITE_EXPORT as the name type
 and that preserves any name attribute information (including the
 authenticated/complete flags) associated with the input name (which
 GSS_Export_name() may well not).  The token format is not specified
 here as this facility is intended for inter-process communication
 only; however, all such tokens MUST start with a two-octet token ID,
 hex 04 02, in network byte order.
 The OID for GSS_C_NT_COMPOSITE_EXPORT is 1.3.6.1.5.6.6.

7.8.1. C-Bindings

 The "exp_composite_name" buffer is de-allocated by the caller with
 gss_release_buffer.
 OM_uint32 gss_export_name_composite(
   OM_uint32                     *minor_status,
   gss_const_name_t              name,
   gss_buffer_t                  exp_composite_name
 );

8. IANA Considerations

 IANA has registered a new name-type OID in "SMI Security for Name
 System Designators Codes (nametypes)":
    6  gss-composite-export [RFC6680]
 (The absolute OID is 1.3.6.1.5.6.6.)
 This document creates a namespace of GSS-API name attributes.
 Attributes are named by URIs, so no single authority is technically
 needed for allocation.  However, future deployment experience may
 indicate the need for an IANA registry for URIs used to reference
 names specified by IETF standards.  It is expected that this will be
 a registry of URNs, but this document provides no further guidance on
 this registry.

Williams, et al. Standards Track [Page 15] RFC 6680 GSS-API Naming Extensions August 2012

9. Security Considerations

 This document extends the GSS-API naming model to include support for
 name attributes.  The intention is that name attributes are to be
 used as a basis for (among other things) authorization decisions or
 personalization for applications relying on GSS-API security
 contexts.
 The security of the application may be critically dependent on the
 security of the attributes.  This document classifies attributes as
 asserted or authenticated.  Asserted (non-authenticated) attributes
 MUST NOT be used if the attribute has security implications for the
 application (e.g., authorization decisions) since asserted attributes
 may easily be controlled by the peer directly.
 It is important to understand the meaning of "authenticated" in this
 setting.  Authenticated does not imply that any semantic of the
 attribute is claimed to be true.  The only implication is that a
 trusted third party has asserted the attribute as opposed to the
 attribute being asserted by the peer itself.  Any additional
 semantics are always the result of applying policy.  For instance, in
 a given deployment, the mail attribute of the subject may be
 authenticated and sourced from an email system where "authoritative"
 values are kept.  In another situation, users may be allowed to
 modify their mail addresses freely.  In both cases, the "mail"
 attribute may be authenticated by virtue of being included in signed
 SAML attribute assertions or by other means authenticated by the
 underlying mechanism.
 When the underlying security mechanism does not provide a permanent
 unique identity (e.g., anonymous Kerberos), GSS-API naming extensions
 may be used to provide a permanent unique identity attribute.  This
 may be a globally unique identifier, a value unique within the
 namespace of the attribute issuer, or a "directed" identifier that is
 unique per peer acceptor identity.  SAML, to use one example
 technology, offers a number of built-in constructs for this purpose,
 such as a <NameID> with a Format of
 "urn:oasis:names:tc:SAML:2.0:nameid-format:persistent".  SAML
 deployments also typically make use of domain-specific attribute
 types that can serve as identifiers.

Williams, et al. Standards Track [Page 16] RFC 6680 GSS-API Naming Extensions August 2012

10. References

10.1. Normative References

 [GFD.024]  Meder, S., Welch, V., Tuecke, S., and D. Engert, "GSS-API
            Extensions", Global Grid Forum GFD.024, June 2004,
            <http://www.ggf.org/documents/GFD.24.pdf>.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2743]  Linn, J., "Generic Security Service Application Program
            Interface Version 2, Update 1", RFC 2743, January 2000.
 [RFC2744]  Wray, J., "Generic Security Service API Version 2 :
            C-bindings", RFC 2744, January 2000.
 [RFC5587]  Williams, N., "Extended Generic Security Service Mechanism
            Inquiry APIs", RFC 5587, July 2009.

10.2. Informative References

 [ANSI.X3-4.1986]
            American National Standards Institute, "Coded Character
            Set - 7-bit American Standard Code for Information
            Interchange", ANSI X3.4, 1986.
 [OASIS.saml-core-2.0-os]
            Cantor, S., Kemp, J., Philpott, R., and E. Maler,
            "Assertions and Protocol for the OASIS Security Assertion
            Markup Language (SAML) V2.0", OASIS Standard saml-core-
            2.0-os, March 2005.
 [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, November 2003.
 [RFC4120]  Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
            Kerberos Network Authentication Service (V5)", RFC 4120,
            July 2005.
 [RFC4556]  Zhu, L. and B. Tung, "Public Key Cryptography for Initial
            Authentication in Kerberos (PKINIT)", RFC 4556, June 2006.
 [RFC4768]  Hartman, S., "Desired Enhancements to Generic Security
            Services Application Program Interface (GSS-API) Version 3
            Naming", RFC 4768, December 2006.

Williams, et al. Standards Track [Page 17] RFC 6680 GSS-API Naming Extensions August 2012

Authors' Addresses

 Nicolas Williams
 Cryptonector, LLC
 EMail: nico@cryptonector.com
 Leif Johansson
 Swedish University Network
 Thulegatan 11
 Stockholm
 Sweden
 EMail: leifj@sunet.se
 URI:   http://www.sunet.se
 Sam Hartman
 Painless Security
 EMail: hartmans-ietf@mit.edu
 Simon Josefsson
 SJD AB
 Johan Olof Wallins Vaeg 13
 171 64 Solna
 Sweden
 EMail: simon@josefsson.org
 URI:   http://josefsson.org/

Williams, et al. Standards Track [Page 18]

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