NETWORK WORKING GROUP N. Williams Internet-Draft Sun Expires:
August 28,September 22, 2008 February 25,March 21, 2008 Extended Generic Security Service Mechanism Inquiry APIs draft-ietf-kitten-extended-mech-inquiry-03.txtdraft-ietf-kitten-extended-mech-inquiry-04.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 28,September 22, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document introduces new application programming interfaces (APIs) to the Generic Security Services API (GSS-API) for extended mechanism attribute inquiry. These interfaces are primarily intended to reduce instances of hardcoding of mechanism identifiers in GSS applications. These interfaces include: mechanism attributes and attribute sets, a function for inquiring the attributes of a mechanism, a function for indicating mechanisms that posses given attributes, and a function for displaying mechanism attributes. Table of Contents 1. Conventions used in this document . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3 3. New GSS-API Interfaces . . . . . . . . . . . . . . . . . . 3 3.1. Mechanism Attributes and Attribute Sets . . . . . . . . . 3 3.2. List of Known Mechanism Attributes . . . . . . . . . . . . 4 3.3. Mechanism Attribute Sets of Existing Mechs . . . . . . . . 6 3.4. New GSS-API Function Interfaces . . . . . . . . . . . . . 7 3.4.1. Mechanism Attribute Criticality . . . . . . . . . . . . . 8 3.4.2. GSS_Indicate_mechs_by_attr() . . . . . . . . . . . . . . . 8 188.8.131.52.4.3. GSS_Inquire_attrs_for_mech() . . . . . . . . . . . . . . . 8 184.108.40.206 3.4.4. GSS_Display_mech_attr() . . . . . . . . . . . . . . . . . 9 220.127.116.11.4.5. New Major Status Values . . . . . . . . . . . . . . . . . 9 18.104.22.168 3.4.6. C-Bindings . . . . . . . . . . . . . . . . . . . . . . . . 910 4. Requirements for Mechanism Designers . . . . . . . . . . . 1011 5. IANA Considerations . . . . . . . . . . . . . . . . . . . 1011 6. Security considerations . . . . . . . . . . . . . . . . . 1011 7. References . . . . . . . . . . . . . . . . . . . . . . . . 1112 7.1. Normative References . . . . . . . . . . . . . . . . . . . 1112 7.2. Informative References . . . . . . . . . . . . . . . . . . 1112 Author's Address . . . . . . . . . . . . . . . . . . . . . 1112 Intellectual Property and Copyright Statements . . . . . . 1213 1. 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]. 2. Introduction GSS-API [RFC2743] mechanisms have a number of properties that may be of interest to applications. The lack of APIs for inquiring about available mechanisms' properties has meant that many GSS-API applications must hardcode mechanism OIDs. Ongoing work may result in a variety of new GSS-API mechanisms. Applications should not have to hardcode their OIDs. For example, the SSHv2 protocol [RFC4251] supports the use of GSS-API mechanisms for authentication [RFC4462], but it explicitly prohibits the use of SPNEGO [RFC4178]. Future mechanisms that negotiate mechanisms would have to be forbidden as well, but there is no way to implement applications that inquire what mechanisms are available and then programmatically exclude mechanisms "like SPNEGO". 3. New GSS-API Interfaces We introduce a new concept: that of mechanism attributes. By allowing applications to query the set of attributes associated with individual mechanisms and to find out which mechanisms support a given set of attributes we allow applications to select mechanisms based on their attributes yet without having to hardcode mechanism OIDs. Section 3.1 describes the mechanism attributes concept. Sections 3.4.1, 3.4.2 and3.4.2, 3.4.3 and 3.4.4 describe three new interfaces that deal in mechanisms and attribute sets: o GSS_Indicate_mechs_by_attrs() o GSS_Inquire_attrs_for_mech() o GSS_Display_mech_attr() 3.1. Mechanism Attributes and Attribute Sets An abstraction for the features provided by pseudo-mechanismsmechanisms and pseudo- mechanisms is needed in order to facilitate the programmatic selection of mechanisms. Pseudo-mechanisms are mechanisms which make reference to other mechanisms in order to provide their services. For example, SPNEGO is a pseudo-mechanism, for without other mechanisms SPNEGO is useless. Two data types are needed: one for individual mechanism attributes and one for mechanism attribute sets. To simplify the mechanism attributes interfaces we reuse the 'OID' and 'OID set' data types and model individual mechanism attribute types as OIDs. To this end we define an open namespace of mechanism attributes and assign them arcs off of this OID: <TBD> [22.214.171.124.5.5.12<TBA by IANA> [126.96.36.199.5.5.13 appears to be available]available; see http://www.iana.org/assignments/smi-numbers] Each mechanism has a set of mechanism attributes that it supports as described in its specification. 3.2. List of Known Mechanism Attributes +-------------------------+---------+-------------------------+ | Mech Attr Name | OID Arc | Arc Name | +-------------------------+---------+-------------------------+ | GSS_C_MA_MECH_CONCRETE | (1) | concrete-mech | | GSS_C_MA_MECH_PSEUDO | (2) | pseudo-mech | | GSS_C_MA_MECH_COMPOSITE | (3) | composite-mech | | GSS_C_MA_MECH_NEGO | (4) | mech-negotiation-mech | | GSS_C_MA_MECH_GLUE | (5) | mech-glue | | GSS_C_MA_NOT_MECH | (6) | not-mech | | GSS_C_MA_DEPRECATED | (7) | mech-deprecated | | GSS_C_MA_NOT_DFLT_MECH | (8) | mech-not-default | | GSS_C_MA_ITOK_FRAMED | (9) | initial-is-framed | | GSS_C_MA_AUTH_INIT | (10) | auth-init-princ | | GSS_C_MA_AUTH_TARG | (11) | auth-targ-princ | | GSS_C_MA_AUTH_INIT_INIT | (12) | auth-init-princ-initial | | GSS_C_MA_AUTH_TARG_INIT | (13) | auth-targ-princ-initial | | GSS_C_MA_AUTH_INIT_ANON | (14) | auth-init-princ-anon | | GSS_C_MA_AUTH_TARG_ANON | (15) | auth-targ-princ-anon | | GSS_C_MA_DELEG_CRED | (16) | deleg-cred | | GSS_C_MA_INTEG_PROT | (17) | integ-prot | | GSS_C_MA_CONF_PROT | (18) | conf-prot | | GSS_C_MA_MIC | (19) | mic | | GSS_C_MA_WRAP | (20) | wapwrap | | GSS_C_MA_PROT_READY | (21) | prot-ready | | GSS_C_MA_REPLAY_DET | (22) | replay-detection | | GSS_C_MA_OOS_DET | (23) | oos-detection | | GSS_C_MA_CBINDINGS | (24) | channel-bindings | | GSS_C_MA_PFS | (25) | pfs | | GSS_C_MA_COMPRESS | (26) | compress | | GSS_C_MA_CTX_TRANS | (27) | context-transfer | | <reserved> | (28..) | | +-------------------------+---------+-------------------------+ Table 1 +-------------------------+-----------------------------------------+ | Mech Attr Name | Purpose | +-------------------------+-----------------------------------------+ | GSS_C_MA_MECH_CONCRETE | Indicates that a mech is neither a | | | pseudo- mechanism nor a composite | | | mechanism. | | GSS_C_MA_MECH_PSEUDO | Indicates that a mech is a | | | pseudo-mechanism. | | GSS_C_MA_MECH_COMPOSITE | Indicates that a mech is a composite of | | | other mechanisms. This is reserved for | | | a specification of "stackable" | | | pseudo-mechanisms. | | GSS_C_MA_MECH_NEGO | Indicates that a mech negotiates other | | | mechs (e.g., SPNEGO has this | | | attribute). | | GSS_C_MA_MECH_GLUE | Indicates that the OID is not for a | | | mechanism but for the GSS-API itself. | | GSS_C_MA_NOT_MECH | Indicates that the OID is known, yet | | | also known not to be the OID of any | | | GSS-API mechanism (or the GSS-API | | | itself). | | GSS_C_MA_DEPRECATED | Indicates that a mech (or its OID) is | | | deprecated and MUST NOT be used as a | | | default mechanism. | | GSS_C_MA_NOT_DFLT_MECH | Indicates that a mech (or its OID) MUST | | | NOT be used as a default mechanism. | | GSS_C_MA_ITOK_FRAMED | Indicates that the given mechanism's | | | initial context tokens are properly | | | framed as per-section 3.1 of rfc2743. | | GSS_C_MA_AUTH_INIT | Indicates support for authentication of | | | initiator to acceptor. | | GSS_C_MA_AUTH_TARG | Indicates support for authentication of | | | acceptor to initiator. | | GSS_C_MA_AUTH_INIT_INIT | Indicates support for "initial" | | | authentication of initiator to | | | acceptor. "Initial authentication" | | | refers to the use of passwords, or keys | | | stored on tokens, for authentication. | | | Whether a mechanism supports initial | | | authentication may depend on IETF | | | consensus (see Security | | | Considerations). | | GSS_C_MA_AUTH_TARG_INIT | Indicates support for initial | | | authentication of acceptor to | | | initiator. | | GSS_C_MA_AUTH_INIT_ANON | Indicates support for | | | GSS_C_NT_ANONYMOUS as an initiator | | | principal name. | | GSS_C_MA_AUTH_TARG_ANON | Indicates support for | | | GSS_C_NT_ANONYMOUS as a target | | | principal name. | | GSS_C_MA_DELEG_CRED | Indicates support for credential | | | delegation. | | GSS_C_MA_INTEG_PROT | Indicates support for per-message | | | integrity protection. | | GSS_C_MA_CONF_PROT | Indicates support for per-message | | | confidentiality protection. | | GSS_C_MA_MIC | Indicates support for MIC tokens. | | GSS_C_MA_WRAP | Indicates support for WRAP tokens. | | GSS_C_MA_PROT_READY | Indicates support for per-message | | | protection prior to full context | | | establishment. | | GSS_C_MA_REPLAY_DET | Indicates support for replay detection. | | GSS_C_MA_OOS_DET | Indicates support for out-of-sequence | | | detection. | | GSS_C_MA_CBINDINGS | Indicates support for channel bindings. | | GSS_C_MA_PFS | Indicates support for Perfect Forward | | | Security. | | GSS_C_MA_COMPRESS | Indicates support for compression of | | | data inputs to GSS_Wrap(). | | GSS_C_MA_CTX_TRANS | Indicates support for security context | | | export/import. | +-------------------------+-----------------------------------------+ Table 2 3.3. Mechanism Attribute Sets of Existing Mechs The Kerberos V mechanism [RFC1964] provides the following mechanism attributes: o GSS_C_MA_MECH_CONCRETE o GSS_C_MA_ITOK_FRAMED o GSS_C_MA_AUTH_INIT o GSS_C_MA_AUTH_TARG o GSS_C_MA_DELEG_CRED o GSS_C_MA_INTEG_PROT o GSS_C_MA_CONF_PROT o GSS_C_MA_MIC o GSS_C_MA_WRAP o GSS_C_MA_PROT_READY o GSS_C_MA_REPLAY_DET o GSS_C_MA_OOS_DET o GSS_C_MA_CBINDINGS o GSS_C_MA_CTX_TRANS (some implementations, using implementation- specific exported context token formats) The Kerberos V mechanism also has a deprecated OID which has the same mechanism attributes as above, and GSS_C_MA_DEPRECATED. The mechanism attributes of the SPKM [RFC2025] family of mechanisms will be provided in a separate document as SPKM is current being reviewed for possibly significant changes due to problems in its specifications. The LIPKEY mechanism [RFC2847] offers the following attributes: o GSS_C_MA_MECH_CONCRETE o GSS_C_MA_ITOK_FRAMED o GSS_C_MA_AUTH_INIT_INIT o GSS_C_MA_AUTH_TARG (from SPKM-3) o GSS_C_MA_AUTH_TARG_ANON (from SPKM-3) o GSS_C_MA_INTEG_PROT o GSS_C_MA_CONF_PROT o GSS_C_MA_REPLAY_DET o GSS_C_MA_OOS_DET o GSS_C_MA_CTX_TRANS (some implementations, using implementation- specific exported context token formats) (LIPKEY should also provide GSS_C_MA_CBINDINGS, but SPKM-3 requires clarifications on this point.) The SPNEGO mechanism [RFC4178] provides the following attributes: o GSS_C_MA_MECH_NEGO o GSS_C_MA_ITOK_FRAMED The attributes of mechanisms negotiated by SPNEGO are not modified by the use of SPNEGO.All other mechanisms' attributes will be described elsewhere. 3.4. New GSS-API Function Interfaces Several new interfaces are given by which, for example, GSS-API applications may determine what features are provided by a given mechanism and what mechanisms provide what features. These new interfaces are all OPTIONAL. Applications should use GSS_Indicate_mechs_by_attr() instead of GSS_Indicate_mechs() wherever possible. Applications can use GSS_Indicate_mechs_by_attr() to determine what, if any, mechanisms provide a given set of features. GSS_Indicate_mechs_by_attr() can also be used to indicate (as in GSS_Indicate_mechs()) the set of available mechanisms of each type (concrete, mechanism negotiation pseudo-mechanism, etc.). 3.4.1. Mechanism Attribute Criticality Mechanism attributes may be added at any time. Not only may attributes be added to the list of known mechanism attributes at any time, but the set of mechanism attributes supported by a mechanism can be changed at any time. For example, new attributes might be added to reflect whether a mechanism's initiator must contact online infrastructure, and/or whether the acceptor must do so. In this example the Kerberos V mechanism would gain a new attribute even though the mechanism itself is not modified. Applications making use of attributes not defined herein then would have no way of knowing whether a GSS-API implementation and its mechanisms know about new mechanism attributes. To address this problem GSS_Indicate_mechs_by_attr() and GSS_Indicate_mechs_by_attr() support a notion of critical mechanism attributes. Applications can search for mechanisms that understand mechanism attributes that are critical to the application, and the application may ask what mechanism attributes are understood by a given mechanism. 3.4.2. GSS_Indicate_mechs_by_attr() Inputs: o desired_mech_attrs SET OF OBJECT IDENTIFIER -- set of GSS_C_MA_* OIDs that the mechanisms indicated in the mechs output parameter MUST offer.offer o except_mech_attrs SET OF OBJECT IDENTIFIER -- set of GSS_C_MA_* OIDs that the mechanisms indicated in the mechs output parameter MUST NOT offer.offer o critical_mech_attrs SET OF OBJECT IDENTIFIER -- set of GSS_C_MA_* OIDs that the mechanisms indicated in the mechs output parameter MUST understand (i.e., mechs must know whether critical attributes are or are not supported) Outputs: o major_status INTEGER,INTEGER o minor_status INTEGER,INTEGER o mechs SET OF OBJECT IDENTIFIER -- set of mechanisms that support --the given desired_mech_attrs but not the except_mech_attrs.except_mech_attrs, and all of which understand the given critical_mech_attrs Return major_status codes: o GSS_S_COMPLETE indicates success; the output mechs parameter MAY be the empty set (GSS_C_NO_OID_SET). o GSS_BAD_MECH_ATTR indicates that at least one mechanism attribute OID in desired_mech_attrs or except_mech_attrs is unknown to the implementation. oGSS_S_FAILURE indicates that the request failed for some other reason. GSS_Indicate_mechs_by_mech_attrs()GSS_Indicate_mechs_by_attrs() returns the set of mechanismOIDs corresponding to mechanisms that offer at least the desired_mech_attrs but none of the except_mech_attrs. When desired_mech_attrsexcept_mech_attrs, and except_mech_attrswhich understand all of the attributes listed in critical_mech_attrs. When all three set of OID input parameters are the empty set this function acts as a version of GSS_indicate_mechs() that outputs the set of all supported mechanisms of all types. By setting the desired_mechs input parameter to a set of a single GSS_C_MA_MECH* feature applications can obtain the list of all supported mechanisms of a given type (concrete, etc...). 3.4.2.mechanisms. 3.4.3. GSS_Inquire_attrs_for_mech() Inputs: o mech OBJECT IDENTIFIER -- mechanism OID Outputs: o major_status INTEGER,INTEGER o minor_status INTEGER,INTEGER o mech_attrs SET OF OBJECT IDENTIFIER -- set of mech_attrs OIDs (GSS_C_MA_*) supported by the mechanism o known_mech_attrs SET OF OBJECT IDENTIFIER -- set of mech_attrs OIDs known to the mechanism implementation. Return major_status codes: o GSS_S_COMPLETE indicates success; the output mech_attrs parameter MAY be the empty set (GSS_C_NO_OID_SET). o GSS_S_BAD_MECH indicates that the mechanism named by the mech parameter does not exist or that mech is GSS_C_NO_OID and no default mechanism could be determined. o GSS_S_FAILURE indicates that the request failed for some other reason. GSS_Inquire_mech_attrs_for_mech() indicates the set of mechanism attributes supported by a given mechanism. 188.8.131.52.4.4. GSS_Display_mech_attr() Inputs: o mech_attr OBJECT IDENTIFIER -- mechanism attribute OID Outputs: o major_status INTEGER,INTEGER o minor_status INTEGER,INTEGER o name OCTET STRING, -- name of mechanism attribute (e.g., GSS_C_MA_*) o short_desc OCTET STRING, -- a short description of the mechanism attribute o long_desc OCTET STRING -- a longer description of the mechanism attribute Return major_status codes: o GSS_S_COMPLETE indicates success. o GSS_S_BAD_MECH_ATTR indicates that the mechanism attribute referenced by the mech_attr parameter is unknown to the implementation. o GSS_S_FAILURE indicates that the request failed for some other reason. This function can be used to obtain human-readable descriptions of GSS-API mechanism attributes. 184.108.40.206.4.5. New Major Status Values A single new major status code is added for GSS_Display_mech_attr(): o GSS_S_BAD_MECH_ATTR roughly corresponding to GSS_S_BAD_MECH, but applicable to mechanism attribute OIDs, rather than to mechanism OIDs. For the C-bindings of the GSS-API [RFC2744] GSS_S_BAD_MECH_ATTR shall have a routine error number of 19 (this is shifted to the left by GSS_C_ROUTINE_ERROR_OFFSET). 220.127.116.11.4.6. C-Bindings #define GSS_S_BAD_MECH_ATTR (19ul << GSS_C_ROUTINE_ERROR_OFFSET) OM_uint32 gss_inquire_mechs_for_mech_attrs(gss_inquire_mechs_for_attrs( OM_uint32 *minor_status, const gss_OID_set desired_mech_attrs, const gss_OID_set except_mech_attrs, const gss_OID_set critical_mech_attrs, gss_OID_set *mechs); OM_uint32 gss_inquire_mech_attrs_for_mech(gss_inquire_attrs_for_mech( OM_uint32 *minor_status, const gss_OID mech, gss_OID_set *mech_attrs);*mech_attrs, gss_OID_set *known_mech_attrs); OM_uint32 gss_display_mech_attr( OM_uint32 *minor_status, const gss_OID mech_attr, gss_buffer_t name, gss_buffer_t short_desc, gss_buffer_t long_desc); Figure 1 4. Requirements for Mechanism Designers All future GSS-API mechanism specifications MUST: o list the set of GSS-API mechanism attributes associated with them 5. IANA Considerations The namsepace of programming language symbols with names beginning with GSS_C_MA_* is reserved for allocation by IESG Protocol Action (probably inAction. The IANA should allocate a base OID, as an arc of 18.104.22.168.5.5, for the specificationsset of future GSS-API mechanisms).GSS_C_MA_* described herein, and it should register all of the GSS_C_MA_* values described in Section 3.2 6. Security considerations This document specifies extensions to a security-related API. It imposes new requirements on future GSS-API mechanisms, and the specification of future protocols that use the GSS-API should make reference to this document where applicable. The ability to inquire about specific properties of mechanisms should improve security. The semantics of each mechanism attribute may include a security component. Application developers must understand that mechanism attributes may be added at any time, both, to the set of known mechanism attributes, as well as to existing mechanism's sets of supported mechanism attributes. Therefore application developers using the APIs described herein must understand what mechanism attributes their applications depend critically on, and must use the mechanism attribute criticality features of these APIs. 7. References 7.1. Normative References [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. 7.2. Informative References [RFC1964] Linn, J., "The Kerberos Version 5 GSS-API Mechanism", RFC 1964, June 1996. [RFC2025] Adams, C., "The Simple Public-Key GSS-API Mechanism (SPKM)", RFC 2025, October 1996. [RFC2847] Eisler, M., "LIPKEY - A Low Infrastructure Public Key Mechanism Using SPKM", RFC 2847, June 2000. [RFC4178] Zhu, L., Leach, P., Jaganathan, K., and W. Ingersoll, "The Simple and Protected Generic Security Service Application Program Interface (GSS-API) Negotiation Mechanism", RFC 4178, October 2005. [RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) Protocol Architecture", RFC 4251, January 2006. [RFC4462] Hutzelman, J., Salowey, J., Galbraith, J., and V. Welch, "Generic Security Service Application Program Interface (GSS-API) Authentication and Key Exchange for the Secure Shell (SSH) Protocol", RFC 4462, May 2006. Author's Address Nicolas Williams Sun Microsystems 5300 Riata Trace Ct Austin, TX 78727 US Email: Nicolas.Williams@sun.com Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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