Internet Engineering Task Force (IETF) L. Hornquist Astrand
Request for Comments: 5896 Apple, Inc.
Updates: 4120 S. Hartman
Category: Standards Track Painless Security, LLC
ISSN: 2070-1721 June 2010
Internet Engineering Task Force (IETF) L. Hornquist Astrand
Request for Comments: 5896 Apple, Inc.
Updates: 4120 S. Hartman
Category: Standards Track Painless Security, LLC
ISSN: 2070-1721 June 2010
Generic Security Service Application Program Interface (GSS-API): Delegate if Approved by Policy
通用安全服务应用程序接口（GSS-API）：经政策批准后委派
Abstract
摘要
Several Generic Security Service Application Program Interface (GSS-API) applications work in a multi-tiered architecture, where the server takes advantage of delegated user credentials to act on behalf of the user and contact additional servers. In effect, the server acts as an agent on behalf of the user. Examples include web applications that need to access e-mail or file servers, including CIFS (Common Internet File System) file servers. However, delegating the user credentials to a party who is not sufficiently trusted is problematic from a security standpoint. Kerberos provides a flag called OK-AS-DELEGATE that allows the administrator of a Kerberos realm to communicate that a particular service is trusted for delegation. This specification adds support for this flag and similar facilities in other authentication mechanisms to GSS-API (RFC 2743).
多个通用安全服务应用程序接口（GSS-API）应用程序在多层体系结构中工作，其中服务器利用委派的用户凭据代表用户行事并联系其他服务器。实际上，服务器充当代表用户的代理。示例包括需要访问电子邮件或文件服务器的web应用程序，包括CIFS（通用Internet文件系统）文件服务器。但是，从安全角度来看，将用户凭据委托给不充分信任的一方是有问题的。Kerberos提供了一个名为OK-AS-DELEGATE的标志，该标志允许Kerberos领域的管理员通信某个特定服务是否受信任以进行委派。本规范向GSS-API（RFC 2743）添加了对该标志和其他身份验证机制中类似设施的支持。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
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.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。
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/rfc5896.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc5896.
Copyright Notice
版权公告
Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2010 IETF信托基金和确定为文件作者的人员。版权所有。
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 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . . 3
3. GSS-API flag, C binding . . . . . . . . . . . . . . . . . . . . 3
4. GSS-API Behavior . . . . . . . . . . . . . . . . . . . . . . . 3
5. Kerberos GSS-API Behavior . . . . . . . . . . . . . . . . . . . 4
6. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . . 3
3. GSS-API flag, C binding . . . . . . . . . . . . . . . . . . . . 3
4. GSS-API Behavior . . . . . . . . . . . . . . . . . . . . . . . 3
5. Kerberos GSS-API Behavior . . . . . . . . . . . . . . . . . . . 4
6. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Several GSS-API applications work in a multi-tiered architecture, where the server takes advantage of delegated user credentials to act on behalf of the user and contact additional servers. In effect, the server acts as an agent on behalf of the user. Examples include web applications that need to access e-mail or file servers, including CIFS file servers. However, delegating user credentials to a party who is not sufficiently trusted is problematic from a security standpoint.
多个GSS-API应用程序在多层体系结构中工作，其中服务器利用委派的用户凭据代表用户行事并联系其他服务器。实际上，服务器充当代表用户的代理。示例包括需要访问电子邮件或文件服务器（包括CIFS文件服务器）的web应用程序。但是，从安全角度来看，将用户凭据委托给不充分信任的一方是有问题的。
Today, GSS-API [RFC2743] leaves the determination of whether delegation is desired to the client application. An application requests delegation by setting the deleg_req_flag when calling init_sec_context. This requires client applications to know what services should be trusted for delegation.
如今，GSS-API[RFC2743]将委托是否需要委托给客户机应用程序的确定权留给了客户机应用程序。应用程序在调用init_secu上下文时，通过设置deleg_req_标志来请求委派。这要求客户机应用程序知道应该信任哪些服务进行委托。
However, blindly delegating to services for applications that do not need delegation is problematic. In some cases, a central authority is in a better position than the client application to know what services should receive delegation. Some GSS-API mechanisms have a
然而，盲目地将服务委托给不需要委托的应用程序是有问题的。在某些情况下，中央机构比客户机应用程序更能了解哪些服务应该接受委托。一些GSS-API机制具有
facility to allow an administrator to communicate that a particular service is an appropriate target for delegation. For example, a Kerberos [RFC4121] KDC can set the OK-AS-DELEGATE flag in issued tickets as such an indication. It is desirable to expose this knowledge to the GSS-API client so the client can request delegation if and only if central policy recommends delegation to the given service.
允许管理员传达特定服务是委派的适当目标的功能。例如，Kerberos[RFC4121]KDC可以在发出的票据中设置OK-AS-DELEGATE标志作为指示。希望将此知识公开给GSS-API客户机，以便客户机可以在且仅在中央策略建议委托给给定服务时请求委托。
This specification adds a new input flag to gss_init_sec_context() to request delegation when approved by central policy. In addition, a constant value to be used in the GSS-API C bindings [RFC2744] is defined. Finally, the behavior for the Kerberos mechanism [RFC4121] is specified.
此规范向gss_init_sec_context（）添加一个新的输入标志，以在中央策略批准时请求委派。此外，还定义了GSS-API C绑定[RFC2744]中使用的常量值。最后，指定Kerberos机制[RFC4121]的行为。
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].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
The gss_init_sec_context API is extended to gain a new input flag, deleg_policy_req_flag, and a new output flag, deleg_policy_state BOOLEAN. If the deleg_policy_req_flag is set, then delegation SHOULD be performed if recommended by central policy. When delegation was recommended by the central policy and when delegation was done, the output flag deleg_policy_state will be set.
扩展gss_init_sec_上下文API以获得新的输入标志deleg_policy_req_标志和新的输出标志deleg_policy_state BOOLEAN。如果设置了deleg_policy_req_标志，则应在中央策略建议的情况下执行委派。当中央策略建议委派时以及委派完成时，将设置输出标志deleg_policy_state。
In addition, the C bindings are extended to define the following constant to represent both deleg_policy_req_flag and deleg_policy_state (just like GSS_C_DELEG_FLAG maps to two flags).
此外，C绑定被扩展以定义以下常量来表示deleg_policy_req_标志和deleg_policy_状态（就像GSS_C_deleg_标志映射到两个标志一样）。
#define GSS_C_DELEG_POLICY_FLAG 32768
#定义GSS_C_DELEG_策略_标志32768
As before, if the deleg_req_flag is set, the GSS-API mechanism will attempt delegation of user credentials. When delegation is successful, deleg_state will return TRUE in both the initiator and acceptor output state (gss_init_sec_context and gss_accept_sec_context, respectively).
与前面一样，如果设置了deleg_req_标志，GSS-API机制将尝试委派用户凭据。当委派成功时，deleg_状态将在发起方和接受方输出状态（分别为gss_init_sec_上下文和gss_accept_sec_上下文）中返回TRUE。
Similarly, if the deleg_policy_req_flag is set, then the GSS-API mechanism will attempt delegation if the mechanism-specific policy recommends to do so. When delegation is allowed and successful, deleg_state will return TRUE in both initiator and acceptor output
类似地，如果设置了deleg_policy_req_标志，那么如果特定于机制的策略建议这样做，那么GSS-API机制将尝试委派。当允许委派且委派成功时，deleg_状态将在启动器和接收器输出中返回TRUE
state. In addition, deleg_policy_state will be set in the initiator output state.
状态此外，deleg_策略_状态将设置为启动器输出状态。
If the initiator sets both the deleg_req_flag and deleg_policy_req_flag, delegation will be attempted unconditionally. When delegation is successful, deleg_state will return TRUE in the initiator and acceptor. When delegation was successful, the deleg_state will return TRUE in the initiator and acceptor. Additionally, if the mechanism-specific policy recommended delegation, the deleg_policy_state will additionally return TRUE for the initiator (only).
如果启动器同时设置了deleg_req_标志和deleg_policy_req_标志，则将无条件尝试委派。当委派成功时，deleg_状态将在发起方和接受方中返回TRUE。当委派成功时，deleg_状态将在发起方和接受方中返回TRUE。此外，如果特定于机制的策略建议委派，则deleg_策略_状态将另外为启动器返回TRUE（仅限）。
Note that deleg_policy_req_flag and deleg_policy_state apply the initiator only. Their state is never sent over the wire.
请注意，deleg_policy_req_标志和deleg_policy_状态仅应用于启动器。他们的状态永远不会通过电线发送。
If the initiator sets the deleg_policy_req_flag (and not deleg_req_flag), the Kerberos GSS-API mechanism MUST only delegate if OK-AS-DELEGATE is set [RFC4120] in the service ticket. Other policy checks MAY be applied. If the initiator sets deleg_req_flag (and not deleg_policy_req_flag), the behavior will be as defined by [RFC2743]. If the initiator set both the deleg_req_flag and deleg_policy_req_flag, delegation will be attempted unconditionally.
如果启动器设置了deleg_策略_req_标志（而不是deleg_req_标志），则只有在服务票证中设置了[RFC4120]OK-AS-delegate时，Kerberos GSS-API机制才能进行委托。可以应用其他策略检查。如果发起方设置了deleg_req_标志（而不是deleg_策略_req_标志），则行为将如[RFC2743]所定义。如果启动器同时设置了deleg_req_标志和deleg_policy_req_标志，则将无条件尝试委派。
[RFC4120] does not adequately describe the behavior of the OK-AS-DELEGATE flag in a cross realm environment. This document clarifies that behavior. If the initiator sets the deleg_policy_req_flag, the GSS-API Kerberos mechanism MUST examine the OK-AS-DELEGATE flag in the service ticket, and it MUST examine all cross realm tickets in the traversal from the user's initial ticket-granting-ticket (TGT) to the service ticket. If any of the intermediate cross realm TGTs do not have the OK-AS-DELEGATE flag set, the mechanism MUST NOT delegate credentials.
[RFC4120]没有充分描述跨领域环境中OK-AS-DELEGATE标志的行为。本文件澄清了这种行为。如果启动器设置了deleg_policy_req_标志，那么GSS-API Kerberos机制必须检查服务票证中的OK-AS-DELEGATE标志，并且必须检查从用户的初始票证授予票证（TGT）到服务票证的遍历中的所有跨域票证。如果任何中间跨领域TGT未设置OK-AS-DELEGATE标志，则该机制不得委托凭据。
Strictly speaking, the deleg_req_flag behavior in [RFC2743] could be interpreted the same as deleg_policy_req_flag is described in this document. However, in practice, the new flag is required because existing applications and user expectations depend upon GSS-API mechanism implementations without the described behavior, i.e., they do not respect OK-AS-DELEGATE.
严格来说，[RFC2743]中的deleg_req_标志行为可以解释为与本文档中描述的deleg_policy_req_标志相同。然而，在实践中，需要使用新标志，因为现有应用程序和用户期望依赖于GSS-API机制实现，而没有描述的行为，即它们不尊重OK-AS-DELEGATE。
In hind sight, the deleg_req_flag should not have been implemented to mean unconditional delegation. Such promiscuous delegation reduces overall security by unnecessarily exposing user credentials, including to hosts and services that the user has no reason to trust.
事后看来，deleg_req_标志不应该被实现为意味着无条件的委托。这种杂乱的委托会不必要地公开用户凭据，包括用户没有理由信任的主机和服务，从而降低总体安全性。
Today there are Kerberos implementations that do not support the OK-AS-DELEGATE flag in the Kerberos database. If the implementation of the deleg_req_flag were changed to honor the OK-AS-DELEGATE flag, users who deploy new client software would never achieve credential delegation because the KDC would never issue a ticket with the OK-AS-DELEGATE flag set. Changing the client software behavior in this way would cause a negative user experience for those users. This is compounded by the fact that users often deploy new software without coordinating with site administrators.
今天，有一些Kerberos实现不支持Kerberos数据库中的OK-AS-DELEGATE标志。如果deleg_req_标志的实现被更改为遵守OK-AS-DELEGATE标志，部署新客户端软件的用户将永远无法实现凭证委派，因为KDC永远不会发出设置了OK-AS-DELEGATE标志的票证。以这种方式更改客户端软件行为会给这些用户带来负面的用户体验。用户经常在没有与站点管理员协调的情况下部署新软件，这一事实使情况更加复杂。
This document introduces a flag that allows the client to get help from the KDC in determining to which servers one should delegate credentials, and the servers to which the client can delegate.
本文档引入了一个标志，允许客户机从KDC获得帮助，以确定应将凭据委托给哪些服务器，以及客户机可以委托给哪些服务器。
The new flag deleg_policy_req_flag is not communicated over the wire, and thus does not present a new opportunity for spoofing or downgrading policy in and of itself.
新标志deleg_policy_req_标志不会通过线路进行通信，因此不会为欺骗或降级策略本身提供新的机会。
Mechanisms should use a trusted/authenticated means of determining delegation policy, and it must not be spoofable on the network.
机制应该使用可信/认证的方法来确定委派策略，并且在网络上不能伪造。
Delegating the user's TGT is still too powerful and dangerous. Ideally, one would delegate specific service tickets, but this is out of scope of this document.
授权用户的TGT仍然太强大和危险。理想情况下，可以委托特定的服务票证，但这超出了本文档的范围。
A client's failure to specify deleg_policy_req_flag can at worst result in NOT delegating credentials. This means that the client does not expand its trust, which is generally safer than the alternative.
客户机未能指定Delegu_policy_req_标志在最坏的情况下可能会导致不委派凭据。这意味着客户不会扩大其信任，这通常比替代方案更安全。
Thanks to Disco Vince Giffin, Thomas Maslen, Ken Raeburn, Martin Rex, Alexey Melnikov, Jacques Vidrine, Tom Yu, Hilarie Orman, and Shawn Emery for reviewing the document and providing suggestions for improvements.
感谢迪斯科·文斯·吉芬、托马斯·马斯伦、肯·雷伯恩、马丁·雷克斯、阿列克谢·梅尔尼科夫、雅克·维德林、汤姆·余、希拉里·奥曼和肖恩·埃默里对文件进行了审查，并提出了改进建议。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC2743] Linn, J., "Generic Security Service Application Program Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC2743]Linn，J.，“通用安全服务应用程序接口版本2，更新1”，RFC 2743，2000年1月。
[RFC2744] Wray, J., "Generic Security Service API Version 2 : C-bindings", RFC 2744, January 2000.
[RFC2744]Wray，J.，“通用安全服务API第2版：C-绑定”，RFC 2744，2000年1月。
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The Kerberos Network Authentication Service (V5)", RFC 4120, July 2005.
[RFC4120]Neuman，C.，Yu，T.，Hartman，S.，和K.Raeburn，“Kerberos网络身份验证服务（V5）”，RFC41202005年7月。
[RFC4121] Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos Version 5 Generic Security Service Application Program Interface (GSS-API) Mechanism: Version 2", RFC 4121, July 2005.
[RFC4121]Zhu，L.，Jaganathan，K.，和S.Hartman，“Kerberos版本5通用安全服务应用程序接口（GSS-API）机制：版本2”，RFC 41212005年7月。
Authors' Addresses
作者地址
Love Hornquist Astrand Apple, Inc.
爱霍恩奎斯特阿斯特兰苹果公司。
EMail: lha@apple.com
EMail: lha@apple.com
Sam Hartman Painless Security, LLC
山姆·哈特曼无痛安全有限责任公司
EMail: hartmans-ietf@mit.edu
EMail: hartmans-ietf@mit.edu