Internet Engineering Task Force Maureen Stillman(editor) INTERNET DRAFT Ram Gopal Senthil Sengodan Nokia Erik Guttman Sun Microsystems Matt Holdrege Strix Systems 5 September 2007 expires March 5, 2008 Threats Introduced by Rserpool and Requirements for Security in response to Threats 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 March 5, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). All Rights Reserved. Abstract Rserpool is an architecture and set of protocols for the management and access to server pools supporting highly reliable applications and for client access mechanisms to a server pool. This Internet draft describes security threats to the Rserpool architecture and presents requirements for security to thwart these threats. Stillman, et al. [Page 1] Internet Draft Threats Introduced by Rserpool 5 September 2007 Contents Status of This Memo 1 Abstract 1 1. Introduction 3 1.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . 3 2. Threats 4 2.1 PE Registration/Deregistration flooding . . . . . . . . . 4 2.2 PE Registration/Deregistration flooding . . . . . . . . . 4 2.3 PE Registration/Deregistration spoofing . . . . . . . . . 4 2.4 PE Registration/Deregistration unauthorized . . . . . . . 5 2.5 Malicious ENRP server joins the group of legitimate ENRP servers . . . . . . . . . . . . . . . . . 5 2.6 Registration/deregistration with malicious ENRP servers . 5 2.7 Malicious ENRP Handlespace Resolution . . . . . . . . . . 5 2.8 Malicious node performs a replay attack.. . . . . . . . . 6 2.9 Re-establishing PU-PE security during failover. . . . . . 6 2.10 Integrity . . . . . . . . . . . . . . . . . . . . . . . . 6 2.11 Data Confidentiality . . . . . . . . . . . . . . . . . . 6 2.12 ENRP Server Discovery . . . . . . . . . . . . . . . . . . 7 2.13 Flood of endpoint unreachable messages . . . . . . . . . 7 2.14 Flood of endpoint keep alive messages . . . . . . . . . . 7 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 3.1 Database security . . . . . . . . . . . . . . . . . . . . 10 3.2 Cookie security . . . . . . . . . . . . . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 11 5. Normative References . . . . . . . . . . . . . . . . . . . . . 11 6. Informative References. . . . . . . . . . . . . . . . . . . . . 11 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11 8. Intellectual Property Statement . . . . . . . . . . . . . . . . 12 9. Author's addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Stillman, et al. [Page 2] Internet Draft Threats Introduced by Rserpool 5 September 2007 1. Introduction RSERPOOL provides a session layer for robustness. The session layer function may redirect communication transparently to upper layers. This alters the direct one-to-one association between communicating endpoints which typically exists between clients and servers. In particular, secure operation of protocols often relies on assumptions at different layers regarding the identity of the communicating party and the continuity of the communication between endpoints. Further, the operation of RSERPOOL itself has security implications and risks. The session layer operates dynamically which imposes additional concerns for the overall security of the end-to-end application. This document explores the security implications of RSERPOOL, both due to its own functions and due to its being interposed between applications and transport interfaces. 1.1 Definitions This document uses the following terms: ENRP Endpoint Name Resolution Protocol (ENRP): Within the operational scope of Rserpool, ENRP defines the procedures and message formats of a distributed fault-tolerant registry service for storing, bookkeeping, retrieving, and distributing pool operation and membership information. ASAP Aggregate Server Access Protocol: A session layer protocol which uses ENRP to provide a high availability handlespace. ASAP is responsible for the abstraction of the underlying transport technologies, load distribution management,fault management, as well as the presentation to the upper layer (i.e., the ASAP user) a unified primitive interface. Operational scope: The part of the network visible to pool users by a specific instance of the reliable server pooling protocols. Pool (or server pool): A collection of servers providing the same application functionality. Pool handle: A logical pointer to a pool. Each server pool will be identifiable in the operational scope of the system by a unique pool handle. ENRP handlespace (or handlespace): A cohesive structure of pool names and relations that may be queried by an internal or external agent. Stillman, et al. [Page 3] Internet Draft Threats Introduced by Rserpool 5 September 2007 Pool element (PE): A server entity that runs ASAP and has registered to a pool. Pool user (PU): A server pool user that runs ASAP. Note, a PU can also be a PE if it has registered itself to a pool. ENRP server: Entity which runs ENRP and is responsible for managing and maintaining the handlespace within the operation scope. 2. Threats 2.1 PE Registration/Deregistration flooding -- non-existent PE Threat: A malicious node could send a stream of false registrations/deregistrations on behalf of non-existent PEs to ENRP servers at a very rapid rate and thereby create unnecessary state in an ENRP server. Effect: Corrupting the pool registrar database and/or disabling the Rserpool discovery and database function. Requirement: An ENRP server that receives a registration/deregistration should not create or update state information until it has authenticated the PE. 2.2 PE Registration/Deregistration flooding -- unauthorized PE Threat: A malicious node or PE could send a stream of registrations/deregistrations that are unauthorized to register/deregister - to ENRP servers at a very rapid rate and thereby create unnecessary state in an ENRP server. Effect: Corrupting the pool registrar database and/or disabling the Rserpool discovery and database function. Requirement: An ENRP server that receives a registration/deregistration should not create or update state information until the authorization of the registering/de-registering entity is verified. 2.3 PE Registration/Deregistration spoofing Threat: A malicious node could send false registrations/deregistrations to ENRP servers concerning a legitimate PE thereby creating false state information in the ENRP servers. Effect: Misinformation in the ENRP server concerning a PE would get propagated to other ENRP servers thereby corrupting the ENRP database. Requirement: An ENRP server that receives a registration/deregistration should not create or update state information until it has authenticated the PE. Stillman, et al. [Page 4] Internet Draft Threats Introduced by Rserpool 5 September 2007 2.4 PE Registration/Deregistration unauthorized Threat: A PE who is not authorized to join a pool could send registrations/deregistrations to ENRP servers thereby creating false state information in the ENRP servers. Effect: Misinformation in the ENRP server concerning a PE would get propagated to other ENRP servers thereby corrupting the ENRP database. Requirement: An ENRP server that receives a registration/deregistration should not create or update state information until it has authorized the requesting entity. 2.5 Malicious ENRP server joins the group of legitimate ENRP servers Threat: Malicious ENRP server joins the group of legitimate ENRP servers with the intent of propagating inaccurate updates to corrupt the ENRP database. Effect: Inconsistent ENRP database state. Requirement: Mutual authentication of ENRP servers. 2.6 Registration/deregistration with malicious ENRP server Threat: A PE unknowingly registers/deregisters with malicious ENRP server. Effect: Registration might not be properly processed or ignored. Requirement: PE needs to authenticate the ENRP server. 2.7 Malicious ENRP Handlespace Resolution Threat: The ASAP protocol receives a handlespace resolution response from an ENRP server, but the ENRP server is malicious and returns random IP addresses or an inaccurate list in response to the pool handle. Effect: PU application communicates with the wrong PE or is unable to locate the PE since the response is incorrect in saying that a PE with that handle did not exist. Requirement: ASAP needs to authenticate the ENRP server. Stillman, et al. [Page 5] Internet Draft Threats Introduced by Rserpool 5 September 2007 2.8 Malicious node performs a replay attack Threat: A malicious node could replay the entire message previously sent by a legitimate entity. This could create false/unnecessary state in the ENRP servers when the replay is for registration/de-registration or update. Effect: False/extra state is maintained by ENRP servers Requirement: Care should be taken to prevent replay attacks. 2.9 Re-establishing PU-PE security during failover Threat: PU fails over from PE A to PE B. In the case that the PU had a trusted relationship with PE A, then the PU will likely not have the same relationship established with PE B. Effect: If there was a trust relationship involving security context between PU and PE A, the equivalent trust relationship will not exist between PU and PE B. This will violate security policy. Requirement: Either notify the application when fail over occurs so the application can take appropriate action to establish a trusted relationship with PE B OR reestablish the security context transparently. 2.10 Integrity Threats: a) ENRP response to pool handle resolution is corrupted during transmission b) ENRP peer messages are corrupted during transmission c) PE sends update for values and that information is corrupted during transmission Effect: ASAP receives corrupt information for pool handle resolution which the PU believes to be accurate. Requirement: Integrity mechanism needed. 2.11 Data Confidentiality Threat: An eavesdropper capable of snooping on fields within messages in transit, may be able to garner information such as topology/location/IP addresses etc. that may not be desirable to divulge. Effect: Information that an administrator does not wish to divulge are divulged. Requirement: Provision for data confidentiality service. Stillman, et al. [Page 6] Internet Draft Threats Introduced by Rserpool 5 September 2007 2.12 ENRP Server Discovery Threat A: Thwarting successful discovery: When a PE wishes to register with an ENRP server, it needs to discover an ENRP server. An attacker could thwart the successful discovery of ENRP server(s) thereby inducing the PE to believe that no ENRP server is available. For instance, the attacker could reduce the returned set of ENRP servers to null or a small set of inactive ENRP servers. Threat B: A similar thwarting scenario also applies when an ENRP server or ASAP on behalf of a PU needs to discover ENRP servers. Threat C: Spoofing successful discovery: An attacker could spoof the discovery by claiming to be a legitimate ENRP server. When a PE wishes to register, it finds the spoofed ENRP server. Threat D: A similar spoofing scenario also applies when an ENRP server or ASAP on behalf of a PU needs to discover ENRP servers. Effect A: A PE that could have been in an application server pool does not become part of a pool. The PE does not complete discovery operation. This is a DOS attack. Effect B: An ENRP server that could have been in an ENRP server pool does not become part of a pool. A PU is unable to utilize services of ENRP servers. Effect C,D: This malicious ENRP would either misrepresent, ignore or otherwise hide or distort information about the PE to subvert RSERPOOL operation. Requirement: Discovery phase needs to be authenticated. 2.13 Flood of endpoint unreachable messages from the PU to the ENRP server These messages are sent by ASAP to the ENRP server when it is unable to contact a PE. There is the potential that a PU could flood the ENRP server intentionally or unintentionally with these messages. Effect: DOS attack on the ENRP server Requirement: Need to limit the number of endpoint unreachable messages sent to the ENRP server from the PU. 2.14 Flood of endpoint keep alive messages from the ENRP server to a PE These messages would be sent in response to a flood of endpoint unreachable messages from the PUs to the ENRP server. Effect: Unintentional DOS attack on the PE Requirement: ENRP must limit the frequency of keep alive messages to a given PE to prevent overwhelming the PE. Stillman, et al. [Page 7] Internet Draft Threats Introduced by Rserpool 5 September 2007 3. Security Considerations for Rserpool This informational document characterizes potential security threats targeting the Rserpool architecture. The security mechanisms required to mitigate these threats are summarized for each architectural component. It will be noted which mechanisms are required and which are optional. From the threats described in this document, the security services required for the Rserpool protocol are enumerated below. Threat 2.1, 2.2, 2.3, 2.4) PE registration/deregistration flooding and/or spoofing. Security mechanism in response: ENRP server authenticates the PE Threat 2.6) PE registers with a malicious ENRP server Security mechanism in response: PE authenticates the ENRP server These combined threats result in a requirement for mutual authentication of the ENRP server and the PE. Threat 2.5) Malicious ENRP server joins the ENRP server pool Security mechanism in response: ENRP servers mutually authenticate Threat 2.7, 2.12) A PU communicates with a malicious ENRP server for handlespace resolution Security mechanism in response: The PU authenticates the ENRP server. If the authentication fails, it looks for another ENRP server. Threat 2.8) Replay attack Security mechanism in response: Security protocol which has protection from replay attacks Threat 2.9) Re-establishing PU-PE security during failover Requirement: Either notify the application when fail over occurs so the application can take appropriate action to establish a trusted relationship with PE B OR reestablish the security context transparently. Threat 2.10) Corrupted data which causes a PU to have misinformation concerning a pool handle resolution Security mechanism in response: Security protocol which supports integrity protection Threat 2.11) Eavesdropper snooping on handlespace information Security mechanism in response: Security protocol which supports data confidentiality To summarize the threats 2.1-2.12 require security mechanisms which support authentication, integrity, data confidentiality and protection from replay attacks. Stillman, et al. [Page 8] Internet Draft Threats Introduced by Rserpool 5 September 2007 For Rserpool we need to authenticate the following: PU -----> ENRP Server (PU authenticates the ENRP server) PE <----> ENRP Server (mutual authentication) ENRP server <-----> ENRP Server (mutual authentication) Summary by component: Rserpool client -- mandatory to implement authentication of the ENRP server is required for accurate pool handle resolution. This is to protect against threats from rogue ENRP servers. In addition, confidentiality, integrity and preventing replay attack are also mandatory to implement to protect from eavesdropping and data corruption or false data transmission. Confidentiality is mandatory to implement and is used when privacy is required. PE to ENRP communications -- mandatory to implement mutual authentication, integrity and protection from replay attack is required for PE to ENRP communications. This is to protect the integrity of the ENRP handle space database. Confidentiality is mandatory to implement and is used when privacy is required. ENRP to ENRP communications -- mandatory to implement mutual authentication, integrity and protection from replay attack is required for ENRP to ENRP communications. This is to protect the integrity of the ENRP handle space database. Confidentiality is mandatory to implement and is used when privacy is required. Threat 2.13) Flood of Endpoint_Unreachable messages from the PU to ENRP server Security mechanism in response: ASAP must control the number of endpoint unreachable messages transmitted from the PU to the ENRP server. Threat 2.14) Flood of Endpoint_KeepAlive messages to the PE from the ENRP server Security mechanism in response: ENRP server must control the number of Endpoint_KeepAlive messages to the PE Stillman, et al. [Page 9] Internet Draft Threats Introduced by Rserpool 5 September 2007 3.1 Security of the ENRP Database Another consideration involves the security characteristics of the ENRP database. Suppose that some of the PEs register with an ENRP server using security and some do not. In this case, when a client requests handle space resolution information from ENRP, it would have to be informed which entries are "secure" and which are not. This would not only complicate the protocol, but actually bring into question the security and integrity of such a database. What can be asserted about the security of such a database is a very thorny question. Due to these two facts it was decided that either the entire ENRP server database is secure, that is, it has registrations exclusively from PEs that have used security mechanisms or the entire database is insecure, that is, registrations are from PEs that have used no security mechanisms. ENRP servers that support security are required to reject any PE server registration that does not use the security mechanisms. Likewise, ENRP servers that support security should not accept updates from other ENRP servers that do not use security mechanisms. 3.2 Cookie mechanism security The application layer is out of scope for Rserpool. However, some questions have been raised about the security of the cookie mechanism which will be addressed. Cookies are passed via the ASAP control channel. If TCP is selected as the transport, the data and control channel must always be multiplexed. Therefore, the cases: a) control channel is secured; data channel is not b) data channel is secured; control channel is not are not allowed. It is even hard to understand what this really means from a security point of view. The multiplexing requirement results in the following cases: 1) the multiplexed control channel-data channel is secure OR 2) the multiplexed control channel-data channel is not secured This applies to cookies in the sense that if you choose to secure your control-data channel, then the cookies are secured. A second issue is that the PE could choose to sign and/or encrypt the cookie. In this case, it must share keys and other information with other PEs. This application level state sharing is out of scope of Rserpool. Stillman, et al. [Page 10] Internet Draft Threats Introduced by Rserpool 5 September 2007 4. IANA Considerations This document introduces no additional considerations for IANA. 5. Normative References [Rserarch] M. Tuexen, et. al., "Architecture for Reliable Server Pooling", draft-ietf-reserpool-arch-10.txt, July, 2005, work in progress. 6. Informative References [RFC2026] S. Bradner, "The Internet Standards Process -- Revision 3", RFC 2026, October 1996. [RFC3365] RFC 3365, Strong Security Requirements for IETF Standard Protocols, August, 2002. 7. Acknowledgements Thanks to the Rserpool security design team and others that provided valuable comments: Lyndon Ong, Randy Stewart, Melinda Shore, Qiaobing Xie, Michael Tuexen, Aron Silverton, Sohrab Modi, Javier Pastor-Balbas, Xingang Guo, M. Piramanayagam, Bernard Aboba and Dhooria Manoj. Funding for the RFC Editor function is currently provided by the Internet Society. Stillman, et al. [Page 11] Internet Draft Threats Introduced by Rserpool 5 September 2007 7. Intellectual Property Statement Full Copyright Statement Copyright (C) The Internet Society (2007). 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. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Stillman, et al. [Page 12] Internet Draft Threats Introduced by Rserpool 5 September 2007 expires 5 March 2008 8. Author's Addresses Ram Gopal Nokia Research Center 5 Wayside Road Burlington, MA 01803 USA email: ram.gopal@nokia.com Erik Guttman Sun Microsystems Eichhoelzelstr. 7 74915 Waibstadt Germany Email: Erik.Guttman@sun.com Matt Holdrege Strix Systems 26610 Agoura Road, Suite 110 Calabasas, CA, 91302 matt@strixsystems.com Senthil Sengodan Nokia Research Center 5 Wayside Road Burlington, MA 01803 USA email: Senthil.sengodan@nokia.com Maureen Stillman Nokia 35 Woodcrest Ave. Ithaca, NY 14850 USA email: maureen.stillman@nokia.com Stillman, et al. [Page 13]