Patent Application
20080148384
The underlying concepts, but not necessarily the language, of the following application are incorporated herein by reference:
U.S. patent application Ser. No. 11/157,880, filed Jun. 21, 2005. If there are any contradictions or inconsistencies in language between the present application and the application that has been incorporated by reference that might affect the interpretation of the claims in the present application, the claims in the present application should be interpreted to be consistent with the language in the present application.
The present invention relates to telecommunications in general, and, more particularly, to providing an embedded firewall at a telecommunications endpoint.
Backbone packet network 101 is used to transport one or more types of media, such as Voice over Internet Protocol (or “VoIP”), for the subscribers of a particular service provider. Network 101 itself comprises one or more transmission-related nodes such as routers that are used to direct data packets (e.g., voice packets, etc.) from one or more sources to the correct destinations of those packets. Network 101 is capable of handling Internet Protocol-based messages that are transmitted among the network elements that have access to network 101, such as the various telecommunications endpoints and gateways throughout system 100. Although network 101 as depicted is a Voice-over-IP service provider's network, network 101 could alternatively be the Internet or some other type of Internet Protocol-based network.
Local area network (or “LAN”) 102-q provides for the local distribution of signals, such as in an enterprise system, and comprises networking equipment such as hubs, bridges, and switches between backbone packet network 101 and telecommunications endpoints 104-1 through 104-S. LAN 102 operates in accordance with a networking protocol such as Ethernet or IEEE 802.3.
Other-provider network 103-r is used to transport one or more types of media, such as Voice over Internet Protocol (or “VoIP”), for the subscribers of a different service provider than that of backbone network 101, where each network 103-r can belong to a different service provider from one other. Network 103-r comprises one or more transmission-related nodes such as routers or switches that are used to direct signals from one or more sources to the correct destinations of those signals. For example, network 103-1 can be the Public Switched Telephone Network (PSTN), which is capable of handling either analog or digital bearer information in circuit-switched calls among devices; meanwhile, network 103-2 can be another type of circuit-based or packet-based network, such as an Internet Protocol-based network or network based on an entirely different protocol; and so on.
Backbone 101 is connected with the various other networks via different types of networking devices, such as routers and gateways. Router 105-q is a networking device that connects backbone 101 with corresponding LAN 102-q by forwarding data packets between the two networks. Router 105-q routes packets at the network layer (i.e., layer 3) of the Open System Interconnection (OSI) reference model. Meanwhile, gateway 106-r is a networking device that connects backbone 101 with the gateway's corresponding network 103-r by forwarding data packets between the two networks. Gateway 106-r differs from router 105-q in that the gateway acts as a translator between two different types of networks. For example, gateway 106-1 interconnects and acts as a translator between backbone network 101, which is a packet-switched network, and other-provider network 103-1, which is the circuit-switched PSTN described earlier. Because gateway 106-r connects two different types of networks together, one of its main functions is to convert between the different transmission and coding techniques used across the two networks.
Telecommunications endpoint 104-s, for s=1 through S, is a communication appliance such as a deskset, a conferencing unit, a wireless terminal, a desktop or portable computer (i.e., “softphone”), an Internet phone, and so forth. As depicted, endpoint 104-s operates in a local area network. Endpoint 104-s is capable of digitizing voice signals from its user and formatting the digitized signals into transmittable data packets through an audio compressor/decompressor (or “CODEC”) circuit. Similarly, the CODEC circuit of endpoint 104-s is also capable of receiving data packets and converting the information contained within those packets into voice signals that are understandable by the endpoint's user.
Telecommunications endpoint 104-s is a packet-based device that is capable of exchanging information with any other device in telecommunications system 100, in a manner similar to how a personal computer is able to exchange information with other computers throughout the Internet. Consequently, endpoint 104-s is vulnerable to many of the same or similar packet attacks as a personal computer, such as “Denial-of-Service” (DoS) attacks. As is apparent in
Firewalls are able to filter out some malicious packets and can be used in VoIP networks, similar to how they are used in computer data networks. The firewalls, either software or hardware in nature, are mainly deployed at the periphery of the network (i.e., the “network-edge”) to attempt to limit the amount of malicious packets from reaching the endpoints; for example, firewalls can be deployed at routers 105-1 through 105-Q and at gateways 106-1 through 106-R. However, implementing a firewall at a network-edge device is disadvantageous for various reasons. First, a network-edge firewall is only able to protect against malicious traffic that originates beyond the network's edge, not within the network itself. Second, as it often takes little added network traffic to disrupt a Voice-over-IP endpoint, a network-edge firewall might be inadequate to monitor traffic for each and every endpoint in a particular zone. And third, a network-edge firewall lacks specific knowledge that only an endpoint might have, thereby making the network-edge firewall an imperfect monitor of packets. As a result, firewalls that are “embedded” at the endpoints themselves are becoming increasingly necessarily to effectively thwart malicious packet attacks.
It is important to integrate the software firewall process that executes at an endpoint with the pre-existing telephony applications at the endpoint in such as way as to avoid or minimize any adverse effects on the endpoint's performance.
The present invention enables the implementation of an embedded firewall at a telecommunications endpoint. In particular, the illustrative embodiment of the present invention addresses the relationship between the application, firewall engine, and packet-classification rules database that are all resident at the endpoint. In the variations of the illustrative embodiment that are described herein, the application: (i) directly communicates with the co-resident firewall engine such as through local message passing, (ii) shares memory with the firewall engine, and (iii) makes socket calls to the operating system that are intercepted by a middleware layer that subsequently modifies the rules database, depending on the socket call. The common thread to these techniques is that the application, firewall engine, and rules database are co-resident at the endpoint, which is advantageous in the implementation of the embedded firewall, as described below.
The application being protected by the firewall embedded at the endpoint often has the best knowledge about what kind of traffic is legitimate, and hence it can directly control the firewall based on this knowledge. Since the application and firewall engine software components are co-resident, communication between them is more efficient than if the two software components were resident at separate network elements. For example, suppose that the application software is the only component at the endpoint that is permitted to receive, from an external source, information such as an authentication code that is designed to unlock encrypted packets. In accordance with the illustrative embodiment, the application could easily make available the authentication code to the firewall engine through shared memory that is internal to the endpoint. In contrast, a network-edge firewall in the prior art would be unable to access the local memory at the endpoint; consequently, the edge firewall would be unaware of the shared key and authentication codes and, therefore, would be unable to filter out malicious packets that appear to be encrypted.
To avoid or minimize changes to the application software, a middleware layer is inserted between the application and the operating system at the endpoint, where the middleware layer intercepts socket calls and makes changes dynamically to the rules database, based on the socket calls being intercepted. In contrast, while a network-edge firewall in the prior art is also able to establish changeable rules, it does so by tracking the connection state based on packet streams, rather than by capturing socket calls, since the edge firewall is not co-resident with the application. The implication is that the network-edge firewall in the prior art is only able to establish changeable rules for outbound connections that are initiated by the application, not for connections that are initiated by devices that are external to the application.
The illustrative embodiment of the present invention comprises: executing a firewall engine and an application at an endpoint at which ingress packets are received and handled; when a state change in the operational state of the application occurs during the execution of the application, notifying the firewall engine of the state change; and filtering at least one of the ingress packets, based on a first set of packet-classification rules that comprises a first rule, wherein the selection of the first set of packet-classification rules is based on the state change.
In addition to the functionality exhibited in prior-art endpoint 104-s, telecommunications endpoint 204-s is further capable of performing the tasks described below and with respect to
Network interface 201 is capable of receiving packet signals from its associated network, such as incoming packets from other Internet Protocol-capable devices, and of forwarding the information encoded in the signals to processor 202, in well-known fashion. Network interface 201 is also capable of receiving information from processor 302 and of transmitting signals that encode this information to other Internet Protocol-capable devices via the network, in well-known fashion. It will be clear to those skilled in the art, after reading this specification, how to make and use network interface 201.
Processor 202 is a general-purpose processor that is capable of receiving information from interface 201, executing instructions stored in memory 203, reading data from and writing data into memory 203, executing the tasks described below and with respect to
Memory 203 stores the instructions and data used by processor 202. More specifically, memory stores the software applications, firewall engine, rules database, middleware layer, and operating system that are described below and with respect to
Each of
In this first variation, application 301 has distinct operational states, and different sets of firewall rules apply in each state. Application 301 is able to signal a change of state to firewall engine 302. Engine 302 restricts the rules from rules database 303 that are applied to each incoming packet to only that subset which applies in the current state; engine 302 also discards packets that are not explicitly allowed by the applicable rule set. The reduced set of rules that firewall engine 302 must process increases the firewall's efficiency.
For example, a phone application running at endpoint 204-s can exhibit at least the following operational states:
In this second variation, application 301 has its own rules for determining which packets are legitimate and, consequently, is the only entity that can specify them. In this variation, application 301 can directly populate rules database 303 to enforce these rules. As an example, consider the Secure Real-time Transport Protocol (SRTP), which is a mechanism to guarantee the authenticity, integrity, and secrecy of voice packets. Application 303 expects to receive a four-byte authentication code, which is based on a shared key that is negotiated during call setup, for every voice packet. If the authentication code received in the packet is not the expected one, the packet is considered illegitimate and discarded. This can be directly implemented as a firewall rule, in which the incoming voice packet is allowed only if its authentication code matches one of those specified in the rule. In accordance with the illustrative embodiment, application 301 writes the authentication code rule to rules database 303, in memory that is accessible by firewall engine 302. The engine matches the authentication codes of various packets against the list.
In this third variation, application 301 and firewall 302 are co-resident, thereby enabling the presence of middleware layer 504 at endpoint 204-s. Middleware layer 504 dynamically populates rules database 303 by intercepting socket library calls, as are known in the art, made by application 301 to operating system layer 505.
As an example, when application 301 issues a “connect(socket, ip, port)” call to connect to a remote device, middleware 504 intercepts this call and temporarily establishes a rule in database 303 to allow packets from the remote (ip, port) address. If the connection handshake succeeds, middleware layer 504 allows the rule to remain; otherwise, middleware layer 504 deletes the rule from the database. Similarly, when application 301 later issues a call to close the socket, middleware layer 504 deletes the rule.
As a second example, when application 301 makes a “bind(socket, port=1234)” call, to be able to receive packets on port 1234, middleware layer 504 intercepts the call and populates rules database 303 with a rule to allow packets destined to the device at port 1234. When application 301 later issues a call to close the socket, middleware layer 504 deletes the rule from the database. Thus, middleware layer 504 is able to add rules to or remove rules from database 303 without placing a burden on the application programmer.
At task 602, endpoint 204-s checks if engine 302 or database 303 needs to be updated. The points in time when endpoint 204-s checks if an update has to occur can be based, for example, on the rate-based rule update technique described in U.S. patent application Ser. No. 11/157,880, filed Jun. 21, 2005, incorporated herein by reference. If engine 302 or database 303 needs to be updated, task execution proceeds to task 603. Otherwise, task execution proceeds to task 604.
At task 603, endpoint 204-s updates engine 302 or database 303. Task 603 is described in detail below and with respect to
At task 604, firewall engine 302 of endpoint 204-s takes action on one or more packets. Task 604 is described in detail below and with respect to
At task 702, application 301 notifies firewall engine 302 of the state change, as described above and with respect to
At task 703, if application 301 anticipates that future ingress packets being received from the network are to exhibit a predetermined characteristic, then task execution proceeds to task 704. In other words, application 301 can be, at times, aware of a characteristic of the packet traffic of which firewall engine 302 is unaware. In some embodiments, the predetermined characteristic is encryption, in which the ingress packets are formatted in accordance with an encryption-based protocol (e.g., Secure Real-time Transport Protocol, etc.). If application 301 is not anticipating packets with a predetermined characteristic, task execution proceeds instead to task 705.
At task 704, application 301, uniquely being in a position to know about the packet traffic, makes a rule available to engine 302 (e.g., “allow packets that exhibit a particular authentication code”, etc.) by storing the rule in database 303, as described above and with respect to
At task 705, if middleware layer 504 detects a socket call being made, task execution proceeds to task 706. Otherwise, task execution proceeds to task 604.
At task 706, middleware layer 504 intercepts the socket call being made by application 301. In other words, layer 504 will take action related to rules database 303, in addition to completing the socket call to operating system layer 505.
At task 707, middleware layer 504 takes the action of establishing, in database 303, a rule that is based on the socket call, as described above and with respect to
In some embodiments, the selection of the particular set of packet-classification rules to be used is based on the state change that engine 302 is notified about at task 702. In some other embodiments, the particular set of rules used is also based on the transitioned-to state (e.g., from an on-hook state to an off-hook state at endpoint 204-s, etc.). The filtered packets can be either allowed through or discarded, depending on the packet-classification rules.
At task 802, in some embodiments, engine 302 notifies a device that is external to endpoint 204-s, such as an external intrusion detection system or intrusion prevention system. The external system can then take appropriate actions, such as alerting a network administrator or routing critical network traffic to bypass the network region under attack.
At task 803, in some embodiments, engine 302 detects that a packet attack is occurring at endpoint 204-s and, as a result, disables network interface 201, thereby taking advantage of the fact that it is co-resident with the network interface at endpoint 204-s. This disabling prevents endpoint 204-s from being overwhelmed by the sheer intensity of the attack traffic load. Engine 302 can periodically open the network interface to determine if the attack traffic has mitigated in intensity, at which point normal operations can be resumed.
In some embodiments, engine 302 disables network interface 201 for a particular time interval. For example, the time interval can be based on a characteristic of the detected packet attack, such as the intensity of the packet attack.
At task 804, in some embodiments, engine 302 accepts new rules that block attack packets, as a temporary measure when application 301 has been determined to have a new vulnerability and before application 301 is patched to fix the vulnerability. Once the application is patched, the rule is no longer necessary, and engine 302 can remove the rule.
At task 805, engine 302 reports, to an external system, on the current state of the software being executed at endpoint 204-s. The state would describe things such as the version number of the software running at endpoint 204-s. The external system can match this information against a database of known vulnerabilities to determine if the software running at endpoint 204-s is susceptible to any attacks. This information can be used to quarantine vulnerable devices. For example, vulnerable endpoints would not be allowed to register with a gatekeeper and would have to refrain from doing so.
It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc.
Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.
