Patent Application
20140181967
This invention relates generally to the field of secure communications and more particularly to a method and apparatus for detecting undesired packets in a networked environment.
As it is known in the art, Internet Protocol Security (IPsec) is a security protocol that provides security services at the IP layer by enabling a system to select required security protocols, determine the algorithm(s) to use for services, and put in place any cryptographic keys required to provide the requested services. IPsec can be used to protect one or more paths between a pair of hosts, between a pair of secure gateways, or between a secure gateway and a host. The set of security services that IPsec can provide includes access control, connectionless integrity, data origin authentication, limited traffic flow confidentiality, and anti-replay checks.
In IPsec, two protocols are used to provide traffic security. These protocols utilize the Authentication Header (AH) and Encapsulating Security Payload (ESP). The IP Authentication Header is used to provide connectionless integrity and data origin authentication for IP datagrams, and to provide protection against replays. The ESP protocol may provide confidentiality (encryption) and limited traffic flow confidentiality. It also may provide connectionless integrity, data origin authentication, and an anti-replay service. The AH and ESP protocols may be applied alone or in combination with each other to provide a desired set of security services in IPv4 and IPv6.
IPsec offers, via AH or ESP protocol, a form of partial sequence integrity referred to as anti-replay integrity, which detects the arrival of duplicate IP datagrams (or packets) within a constrained window to help counter denial of service (DoS) attacks. A DoS attack is a type of attack on a network that is designed to bring the network to its knees by flooding it with useless traffic. Many DoS attacks, such as the Ping of Death and Teardrop attacks, exploit limitations in the TCP/IP protocols. The anti-replay mechanism seeks to overcome DoS attacks by assigning the sequence number of received packets, and dropping any packets having duplicate sequence numbers within a predefined window.
While the IPSec anti-replay mechanism is effective in many peer to peer environments, there are network architectures that generally cannot benefit from its application. One example of such a system is Provider Provisioned Virtual Private Networks (PPVPNs) such as those described in RFC 2547, incorporated herein by reference. Another such network is described in METHOD AN APPARATUS FOR PROVIDING A SCALABLE AND SECURE NETWORK WITHOUT POINT TO POINT ASSOCIATION, Ser. No. 10/661,959 (attorney docket number 120-142), filed on Sep. 12, 2003 by Fedyk et al, (hereinafter referred to as the Group Security Association (GSA) architecture).
Both the PPVPNs and the GSA architecture use group keys to efficiently secure data communications between edge devices. The GSA architecture incorporates the concepts of group key management protocol with a modification of security boundary positioning to provide a network that is both readily scalable and secure. Trusted ingress points and a trusted egress points in the network are identified. The trusted ingress point may be, for example, a gateway station, which attaches a source station (which is part of a local area network) to the internet, and it is assumed that the gateway station provides firewall protection to any communication behind the gateway. Similarly, the trusted egress station is any station that is coupled to a destination station, and wherein communication between the trusted egress station and destination station is protected. IPSec processing would also be performed at the egress station.
According to GSA architecture each station that is to be part of a private network registers with a key table. A group security association associated with the private network is forwarded to each trusted ingress and egress point that communicates with each member of the private network. When a member of the private network seeks to communicate with another member, it simply forwards the communication to the trusted ingress point with a Virtual Private Network (VPN) group address associated with the other member. The trusted ingress point uses the group security association associated with the private network to transform the communication and forwards the transformed communication through other intermediate stations in the network, until it reaches the trusted egress point. The trusted egress point uses the stored group security association corresponding to the Virtual Private Network (VPN) group address to decode the transformed communication and forwards the communication to the appropriate destination.
Thus, the GSA architecture provides a scalable means for securing communication between two end-points. However, the GSA architecture cannot easily support the use of sequence number for anti-replay handling, because multiple users share the same Security Association (SA), and the multiple users cannot easily synchronize the sequence number of the SA. It would be desirable to identify an anti-replay mechanism for use in the GSA architecture.
In accordance with an aspect there is a method of processing packets in an edge device of a network comprising a group of devices, the method comprising, at the edge device: associating a unique respective transform identifier with each other device of the group of devices, the group of devices using at least one group security association for communication between the devices in the group of devices, each unique transform identifier being determined by the at least one group security association; associating a respective expected sequence number with each other device of the group of devices; receiving a packet from a first device of the group of devices; using the unique respective transform identifier associated with the first device to extract a sequence number from the packet received from the first device; and comparing the extracted sequence number with the respective expected sequence number associated with the first device to determine validity of the packet received from the first device.
In accordance with another aspect an edge device for a network comprises a group of devices, the edge device comprising: a storage medium configured to store: data associating a unique respective transform identifier with each other device of the group of devices, the group of devices using at least one group security association for communication between the devices in the group of devices, each unique transform identifier being determined by the at least one group security association; and data associating a respective expected sequence number with each other device of the group of devices; and logic configured to: receive a packet from a first device of the group of devices; use the unique respective transform identifier associated with the first device to extract a sequence number from the packet received from the first device; and compare the extracted sequence number with the respective expected sequence number associated with the first device to determine validity of the packet received from the first device.
According to one aspect of the invention, a method is provided for detecting undesired packets received at an edge device in a network, where the edge device is a member of a group of devices in the network. The method includes the steps of receiving a transform identifier for each member of the group and decoding a packet received from one of the members of the group using the transform identifier associated with the one of the members, including extracting a sequence number from the packet. The method further includes the step of comparing the sequence number against an expected sequence number for the one of the members, and discarding the packet if the sequence number indicates that the packet is an undesired packet. With such an arrangement, a method is provided that permits anti-replay mechanisms to be used in a group keyed network by enabling receiving members of the group to distinguish between sending members of the group. Because the receiving group member can distinguish between sending group members, it can correlate received sequence numbers with each expected sequence numbers for the different members of the group. In one embodiment, the transform identifier is a security association used to transform communications transmitted by an associated group member. In another embodiment, a common group security association is used for communicating between all group members, and the transform identifier for each member is the Security Protocol Index (SPI) of the associated member.
According to another aspect of the invention, a network device includes a table for storing a plurality of transform identifiers, each one of the plurality of transform identifiers associated with a different one of a plurality of members of a group of which the network device is also a member. The network device also includes a table for storing a sequence number for each one of the plurality of members of the group. In another embodiment, the network device further comprises a means for transforming a communication received from one of the members of the group using the corresponding transform identifier to determine whether a sequence number extracted from the communication is an expected sequence number for the member, and means for discarding packets received with unexpected sequence numbers.
According to another aspect of the invention, a network device includes means for storing, for each group in which the device is a member, a transform identifier for each member of each group and an expected sequence number for each member of each group; and means for determining whether a packet received at the network device is an undesired packet by comparing an extracted serial number, extracted from a communication by a given member of a group using the transform identifier associated with the given member, against an expected serial number stored for the given member, to determine whether the extracted sequence number correlates to the expected sequence number.
According to another aspect of the invention, a network includes a registration table for storing registration information associated with a plurality of members of a group, wherein the registration information includes a transform identifier for each member of the group, the transform identifier for use by the corresponding member of the group for transforming communications issued by the corresponding member. The network further includes means for forwarding the transform identifiers for each member of a group to all members of the group.
According to a further aspect of the invention, a method for detecting replayed packets in a network including the steps of registering each member of a group of members at a device in the network, including associating, with each member of the group, a different transform identifier to be used by the member of the group when transmitting communications to other members of the group; and forwarding transform identifiers for each member of the group to all members of the group to enable each member of the group to distinguish between communications received at the each member for the purposes of detecting replayed packets. With such an arrangement, group members can correlate a received packet with a transmitting group member, and thereby associate certain information in the packet (such as the sequence number) with the sending member for the purposes of detecting undesired packets.
Exemplary methods and apparatus by which the present invention uses unidirectional Security Associations to enable anti-replay mechanisms to be used in networks that use Group Security Associations to secure data between endpoints will now be described with reference to the attached figures.
Referring now to
Group key management protocols help to ensure that only members of a secure group can gain access to and authenticate group data. The main goal of group key management protocol is to securely provide the group members with an up to date Security Association (SA) containing the information need to secure group communication. Generally speaking, a Security Association (SA) is a set of policy and cryptographic keys that provide security services to network traffic that matches that policy. A SA typically includes selectors, properties, cryptographic policy, and keys. The selectors include source and destination transport addresses. The properties include, for example, a security parameter index or cookie pair, and identities. Cryptographic policy includes the algorithms, modes, key lifetimes, and key lengths used for authentication or confidentiality. The keys include the authentication, encryption and signing keys. It should be noted that the present invention may utilize any type of SA, and thus should not be limited to only the SAs used below to describe the exemplary embodiments.
Group Security Associations (GSAs) are a bundling of SAs that together define how a group communicates securely. The GSA may include, for example, a registration SA, a rekey protocol SA, and one more data security protocol SAs. A GSA includes all of the attributes identified above with regard to SAs, but also include several additional attributes. For example, GSAs have group policy attributes, such as the kind of signed credential needed for group membership, if group members will be given new keys when a member is added, or whether group members will be given new keys when a member is removed from the group. A GSA is comprised of multiple SAs, and these SAs may be used for independent purposes. For example, three types of SAs which are generally needed for group communication are Registrations SAs, allowing a group member to register with the GCKS, Re-Key SAs, allowing the GCKS to forward new keys to all group members, and Data Security SAs, which protect data between sending and receiving members of the group.
One element of group key management which is used in the present invention is the Group Controller and Key Server (GCKS) 30. GCKS 30 is shown in
The GCKS 30 is shown to include various representative components, including a key table 32, a registration table 34 and a policy server 35. It should be noted that although the components are shown as separate entities, the below described functionality of each may be merged or further divided, and the functionality may be implemented in software, hardware, or some combination thereof. The key table 32 includes a number of entries, such as entry 33, which stores a key for each group ID. The key is used by the group for encryption and decryption of packets that are transferred between group members, and thus provides at least one SA for the group.
The registration table 34 is used to identify members of each group (or VPN in this example). As CEs enter and leave the VPN, the registration table is updated to reflect the current VPN members. In the event of a key change or the like, the registration table provides member identification data for transmitting the change to each member of the respective group.
According to one aspect of the present invention, the registration table also stores a transform identifier 38 for each member 37 of a group. The transform identifier is associated with each CE, and is used to relate a packet, received at a CE with the sending CE. In several embodiments, the transform identifier is related to security aspects associated with the packet. For example, in one embodiment of the invention, the transform identifier is a unique Security Association (SA) for the given CE. In another embodiment of the invention, the transform identifier is a Security Parameter Index (SPI) associated with the CE. In either embodiment, when the CE registers with the GCKS 30, after it is authenticated, the transform identifier is forwarded to the CE and also pushed to all other member CEs associated with the VPN. Thus, each CE in the group includes certain logic enabling operation of the present invention.
For example, referring now to
The anti-replay mechanism 44 compares the extracted sequence number against an expected sequence number 52 for the sender. In general, anti-replay mechanisms work by discarding packets having matching sequence numbers within a predetermined time window. In one embodiment, no prior contact is assumed with a member so the first sequence number received is always accepted and used to set an expected sequence number. In one embodiment, all sequence numbers are set to zero or another well known number after each received packet stream at the receiver. In an alternative embodiment, when there are multiple receivers in a group, a sender may associate different sequence number streams for each of the different users. Thus each gateway device maintains O(n) SEQ numbers for sending, and O(n) SEQ numbers for receiving.
At the receiver, there are many different manners for determining whether the retrieved sequence number indicates a potential rogue packet, and the present invention is not limited to any particular sequence number determination process. Rather, any method of determining whether the extracted sequence number correlates to the expected sequence number may be substituted herein without affecting the spirit or scope of the invention.
If the anti-replay mechanism 44 determines that the sequence numbers do not correlate, a discard signal is forwarded to the filter 45. The filter effectively controls the forwarding of the received packet to the packet processor 46. Thus the anti-replay mechanism ensures that packets having undesirable sequence numbers will be dropped from further processing.
Although the above describes the ‘transform’ occurring at the CE device, it is to be understood that the present invention can be applied at any point in a network where IPSec processing is performed, provided that the resources can be provided at the destination for storing the transform identifiers for each expected source. Within the context of GSAs, an SPI can be associated with each sender of a group. Such an arrangement allows us to only increase the number of SPIs without actually having to generate and distribute different keys to the sending group members Furthermore, due to the scalable nature of PPVPNs, n SPIs may be used to connect a group of n senders, rather than n*n SPIs that would be required in prior art VPN networks.
Thus the present invention is not limited to being performed at any particular device or hierarchical level in the network.
Referring now to
In one embodiment of the invention, at step 104 when the CE registers with the GCKS, the GCKS selects an SPI for the CE to avoid collisions, and forwards the SPI to the CE. In one embodiment, the CE may previously forward a bit field to the GCKS to be used as part of the SPI. The CE stores the SPI as the transform identifier for that member in the registration table 34. In such an embodiment, each member of the group uses a common Group Security Association (GSA) for securing inter-group communications, and receiving devices can distinguish between sending devices of the group by applying the protocol indicated by the SPI to the received communication.
In an alternative embodiment, when the CE registers with the GCKS, it forwards a desired security association (SA) with its registration request. The SA is stored as the transform identifier in the registration table 34 at step 104.
After the transform identifier has been stored for the CE, the GCKS forwards the transform identifier back to the CE to verify it's acceptance at step 105. In addition at step 105 the GCKS also forwards the identities and transform identifiers of all of the other members of the group to the CE. At step 106, the GCKS pushes the transform identifier of the new CE to other members that are registered as members of the group.
At step 108, the CE updates the table 40 with the member identifiers and transform identifiers for each member in the recently joined group, and proceeds to step 110, where periodic updates from the GCKS, indicating the addition and deletion of members, and updating of transform identifiers cause the table 40 of the CE to be updated.
Upon completion of the processes of
Accordingly a method and apparatus has been shown and described which enables anti-replay mechanisms to be used in systems which utilize group key security associations for securing data between members of a group. The above description and Figures have included various process steps and components that are illustrative of operations that are performed by the present invention. However, although certain components and steps have been described, it is understood that the descriptions are representative only, other functional delineations or additional steps and components can be added by one of skill in the art, and thus the present invention should not be limited to the specific embodiments disclosed. In addition it is understood that the various representational elements may be implemented in hardware, software or a combination thereof. For example the tables of
Those skilled in the art should readily appreciate that programs defining the functions of the present invention can be delivered to a computer in many forms; including, but not limited to: (a) information permanently stored on non-writable storage media (e.g. read only memory devices within a computer such as ROM or CD-ROM disks readable by a computer I/O attachment); (b) information alterably stored on writable storage media (e.g. floppy disks and hard drives); or (c) information conveyed to a computer through communication media for example using baseband signaling or broadband signaling techniques, including carrier wave signaling techniques, such as over computer or telephone networks via a modem.
While the invention is described through the above exemplary embodiments, it will be understood by those of ordinary skill in the art that modification to and variation of the illustrated embodiments may be made without departing from the inventive concepts herein disclosed. Moreover, while the preferred embodiments are described in connection with various illustrative program command structures, one skilled in the art will recognize that the system may be embodied using a variety of specific command structures. Accordingly, the invention should not be viewed as limited except by the scope and spirit of the appended claims.
This application is a continuation of U.S. patent application Ser. No. 10/864,146, titled Method and Apparatus for Providing Replay Protection in Systems Using Group Security Associations, filed Jun. 9, 2004, which claims priority to provisionally filed U.S. application Ser. No. 60/502,537 filed Sep. 12, 2003.
| Number | Date | Country | |
|---|---|---|---|
| 60502537 | Sep 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10864146 | Jun 2004 | US |
| Child | 14194933 | US |
