Network Working Group E. Ertekin Internet-Draft M. Casey Expires:
February 28,July 3, 2008 J. Pezeshki C. Christou Booz Allen Hamilton August 27,December 31, 2007 IPsec Extensions to Support Robust Header Compression over IPsec (RoHCoIPsec) draft-ietf-rohc-ipsec-extensions-hcoipsec-00draft-ietf-rohc-ipsec-extensions-hcoipsec-01 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 February 28,July 3, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract Integrating RoHC with IPsec (RoHCoIPsec) offers the combined benefits of IP security services and efficient bandwidth utilization. Before this can be realized, however, several extensions to the Security Policy Database (SPD), the Security Association Database (SAD), and the IPsec process are required. This document describes the IPsec extensions required to support RoHCoIPsec. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Extensions to IPsec Databases . . . . . . . . . . . . . . . . .3 2.1. Security Policy Database (SPD) . . . . . . . . . . . . . . 3 2.2. Security Association Database (SAD) . . . . . . . . . . . .4 3. Extensions to IPsec Processing . . . . . . . . . . . . . . . . 5 3.1. Addition to the IANA Protocol Numbers Registry . . . . . . 5 3.2. Nested IPComp and RoHCoIPsec Processing . .Verifying the Integrity of Decompressed Packet Headers . . 5 3.2.1. ICV Computation and Integrity Verification . . . . . . 5 3.3. CID Reuse . . . . . . . . . . . . . . . .Nested IPComp and RoHCoIPsec Processing . . . . . . . . . 56 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 56 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 67 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 67 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 67 7.1. Normative References . . . . . . . . . . . . . . . . . . . 67 7.2. Informative References . . . . . . . . . . . . . . . . . . 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 78 Intellectual Property and Copyright Statements . . . . . . . . . . 910 1. Introduction Using IPsec ([IPSEC]) protection offers various security services for IP traffic. However, for tunnel-mode security associations, these benefits come at the cost of additional packet headers, which increase packet overhead. As described in [ROHCOIPSEC], Robust Header Compression (RoHC [ROHC]) can be used with IPsec to reduce the overhead associated with IPsec-protected packets. IPsec-protected traffic is carried between peers by Security Associations (SAs), whose parameters are negotiated on a case-by-case basis. The Security Policy Database (SPD) specifies the services that are to be offered to IP datagrams, and the parameters associated with SAs that have been established are stored in the Security Association Database (SAD). To fully integrate RoHC and IPsec, various extensions to the SPD and SAD that incorporate RoHC-relevant parameters are required. In addition, twothree extensions to the IPsec processing methodology are required. First, a mechanism for identifying RoHC packets must be defined. Second, a mechanism is required to ensure the integrity of the decompressed packet. Finally, the order of the inbound and outbound processing must be enumerated when nesting IP Compression (IPComp [IPCOMP]), RoHC, and IPsec processing. 2. Extensions to IPsec Databases The following subsections specify extensions to the SPD and the SAD to support RoHCoIPsec. 2.1. Security Policy Database (SPD) In general, the SPD is responsible for specifying the security services that are offered to IP datagrams. Entries in the SPD specify how to derive the corresponding values for SAD entries. To support RoHC, the SPD must be extended to include per-channel RoHC parameters. Together, the existing IPsec SPD parameters and the RoHC parameters will dictate packet disposition for traffic that is to be compressed, and subsequently protected by IPsec. The fields contained within each SPD entry are defined in [IPSEC], Section 188.8.131.52. To support RoHC, several processing info fields must be added to the SPD; these fields contain information regarding the RoHC profiles and channel parameters supported by the local RoHC instance. In addition, a field within the SPD entry is required to store a list of integrity algorithms, supported by the RoHCoIPsec instance. This field will be used to negotiate an integrity algorithm to ensure that packet headers are properly decompressed (see Section 3.2). The per-channel configuration parameters required for RoHC in the SPD are as follows (note that this information must only be included in the SPD if the processing info field is set to PROTECT, and if the IPsec mode is set to tunnel mode): MAX_CID: The highest context ID number to be used by the compressor. MAX_CID must be at least 0 and at most 16383 (The value 0 implies having one context). The suggested value for MAX_CID is 15. PROFILES: This indicates the RoHC profiles supported by the decompressor. The list of possible values this field may assume is defined in the [ROHCPROF] registry. MRRU: The size of the largest reconstructed unit that the decompressor is expected to reassemble from segments. In general, is not anticipated that a RoHC over IPsec instance will use RoHC segmentation features. Consequently, the suggested value for MRRU is 0. MAX_HEADER: The largest header size (in octets) that can be compressed. Note that the four RoHC profiles defined in RFC 3095 do not provide for a MAX_HEADER parameter. The parameter MAX_HEADER is therefore without consequence in these profiles. Other profiles (e.g., ones based on RFC 2507) can make use of the parameter by explicitly referencing it. Note: The RoHC LARGE_CIDS channel parameter is set implicitly, based on the value of MAX_CID. Furthermore, the RoHC FEEDBACK_FOR channel parameter is set implicitly to the RoHC channel associated with the SA in the reverse direction. Because both of these RoHC channel parameters are set implicitly, they are not stored in the SPD or SAD.SPD. 2.2. Security Association Database (SAD) Each entry within the SAD defines the parameters associated with each established SA. Unless if the "populate from packet" (PFP) flag is asserted for a particular field, SAD entries are determined by the corresponding SPD entries during the creation of the SA. The data items contained within the SAD are defined in [IPSEC], Section 184.108.40.206. To support RoHC, this list of data items is augmented to include a "RoHC Data Item" field that defines the RoHC parameters. These parameters (i.e., MAX_CID, PROFILES, MRRU, and MAX_HEADER) are enumerated above in Section 2.1. In addition, the FEEDBACK_FOR parameter is also included, which is associated with the SA in the reverse direction. The RoHC parametersFurthermore, two additional datas items are required to store the Integrity Algorithm and respective key that is to be used for a given SAto ensure that packets are properly decompressed (see Section 3.2). These "RoHC Data Item" values may be initialized manually (i.e., administratively configured for manual SAs), or initialized via a key exchange protocol (e.g. IKEv2 [IKEV2]) that has been extended to support the negotiation of RoHC parameters [IKEV2EXT]. 3. Extensions to IPsec Processing 3.1. Addition to the IANA Protocol Numbers Registry In order to demultiplex header-compressed from uncompressed traffic on a RoHC-enabled SA, a "RoHC" value must be reserved in the IANA Protocol Numbers registry. If an outbound packet has a compressed header, the Next Header field of the security protocol header (e.g., AH [AH], ESP [ESP]) must be set to the "RoHC" protocol identifer. If the packet header has not been compressed, the Next Header field remains unaltered. Conversely, for an inbound packet, the value of the security protocol Next Header field is checked to determine if the packet maintains a RoHC header. 3.2. Verifying the Integrity of Decompressed Packet Headers In order to ensure that the RoHC compressed packet is decompressed correctly, RoHCoIPsec will use an Integrity Algorithm (and respective key) to compute a second Integrity Check Value (ICV) for the uncompressed packet. This ICV will be prepended to the header- compressed RoHC-compressed packet. At the decompresser, the decompressed packet will be used with the Integrity Algorithm (and its respective key) to compute a value that will be compared to the ICV. If these values are not identical, the decompressed packet must be dropped by the decompressor. 3.2.1. ICV Computation and Integrity Verification In order to correctly verify the integrity of the decompressed packets, the processing steps for RoHCoIPsec must be implemented in a specific order, as given below. For outbound packets that are to be processed by RoHC: o An ICV is computed for the uncompressed packet via RoHCoIPsec's Integrity Algorithm (and respective key) o The packet is compressed by the RoHC process o The ICV is prepended to the beginning of the compressed packet (in front of the RoHC header) o The security protocol is applied to the packet For inbound packets that are to be decompressed by RoHC: o A packet received on a RoHC-enabled SA is IPsec-processed o The packet is decompressed by the RoHC process o The decompressed packet is used with the Integrity Algorithm (and its respective key) to compute a value that is compared to the ICV (if these two values differ, the packet is dropped) 3.3. Nested IPComp and RoHCoIPsec Processing IPComp ([IPCOMP]) is another mechanism that can be implemented to reduce the size of an IP datagram. If IPComp and RoHCoIPsec are implemented in a nested fashion, the order of the outbound and inbound processing steps must be carefully enumerated. For outbound packets that are to be processed by IPcomp and RoHC: o The ICV is computed for the uncompressed packet, and the appropriate RoHC compression profile is applied to the packet o IPComp is applied, and the packet is sent to the IPsec process o The security protocol is applied to the packet Conversely, for inbound packets that are to be both RoHC- and IPcomp- decompressed: o A packet received on a RoHC-enabled SA is IPsec-processed o The datagram is decompressed based on the appropriate IPComp algorithm o The packet is sent to the RoHC module for header decompression 3.3. CID Reuse All RoHCoIPsec implementations that intend to reuse CIDs (i.e. remap a previously used but now retired CID value in order to conserve CID space) must support the ROHC-DOWN profile, as defined in [ROHC-DOWN]. This profile must be used to shut down the CID value before is can be remapped.and integrity verification 4. Security Considerations A malfunctioning RoHC compressor (i.e., the compressor located at the ingress of the IPsec tunnel) has the ability to send packets to the decompressor (i.e., the decompressor located at the egress of the IPsec tunnel) that do not match the original packets emitted from the end-hosts. Such a scenario will result in a decreased efficiency between compressor and decompressor. Furthermore, this may result in Denial of Service, as the decompression of a significant number of invalid packets may drain the resources of an IPsec device. In addition, some RoHCoIPsec implementations may allow an attacker to identify new traffic flows by monitoring the relative size of the encrypted packets (i.e. a group of "long" packets, followed by a long series of "short" packets may indicate a new flow for some RoHCoIPsec implementations). To mitigate this concern, RoHC padding mechanisms may be used to arbitrarily add padding to transmitted packets to randomize packet sizes. 5. IANA Considerations IANA is requested to allocate one value within the "Protocol Numbers" registry [PROTOCOL] for "RoHC". This value will be used to indicate that the next level protocol header is a RoHC header. 6. Acknowledgments The authors would like to thank Mr. Sean O'Keeffe, Mr. James Kohler, Ms. Linda Noone of the Department of Defense, and Mr. A. Rich Espy of OPnet for their contributions and support for developing this document. In addition, the authors would like to thank Mr. Rohan Jasani for his valuable assistance. Finally, the authors would like to thank the following for their numerous reviews and comments to this document: o Dr. Stephen Kent o Dr. Carsten Bormann o Mr. Lars-Erik Jonnson o Mr. Pasi Eronen 7. References 7.1. Normative References [IPSEC] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [ROHCOIPSEC] Ertekin, E. and C. Christou, "Integration of Header Compression over IPsec Security Associations", work in progress , February 2007. [ROHC] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H., Hannu, H., Jonsson, L., Hakenberg, R., Koren, T., Le, K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K., Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and uncompressed", RFC 3095, July 2001. [IPCOMP] Shacham, A., Monsour, R., Pereira, and Thomas, "IP Payload Compression Protocol (IPComp)", RFC 3173, September 2001. [IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [IKEV2EXT] Pezeshki, J., Ertekin, E., and C. Christou, "Extensions to IKEv2 to Support Robust Header Compression over IPsec (RoHCoIPsec)", work in progress , February 2007. [AH] Kent, S., "IP Authentication Header", RFC 4302, December 2005. [ESP] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [ROHC-DOWN] Bormann, C., "A ROHC Profile for CID shutdown (ROHC- DOWN)", work in progress , July 2007.7.2. Informative References [ROHCOIPSEC] Ertekin, E., Christou, C., Jasani, R., and J. Pezeshki, "Integration of Robust Header Compression (ROHC) over IPsec Security Associations", work in progress , August 2007.[ROHCPROF] IANA, ""RObust"RObust Header Compression (ROHC) Profile Identifiers", IANA registry at: http://www.iana.org/assignments/rohc-pro-ids".www.iana.org/assignments/rohc-pro-ids , October 2005. [PROTOCOL] IANA, ""Assigned Internet Protocol Numbers", IANA registry at: http://www.iana.org/assignments/protocol-numbers". Authors' Addresses Emre Ertekin Booz Allen Hamilton 13200 Woodland Park Dr. Herndon, VA 20171 US Email: firstname.lastname@example.org Michele Casey Booz Allen Hamilton 13200 Woodland Park Dr. Herndon, VA 20171 US Email: email@example.com Jonah Pezeshki Booz Allen Hamilton 13200 Woodland Park Dr. Herndon, VA 20171 US Email: firstname.lastname@example.org Chris Christou Booz Allen Hamilton 13200 Woodland Park Dr. Herndon, VA 20171 US Email: email@example.com Full Copyright Statement Copyright (C) The IETF Trust (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. 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