Patent Grant
7882247
Not applicable.
Wireless networks have become very popular. Students are accessing course information from the college's computer network while sitting in lecture hall or enjoying the outdoors in the middle of the college campus. Doctors are maintaining computing connectivity with the hospital computer network while making their rounds. Office workers can continue to work on documents and access their email as they move from their office to a conference room. Laptop or PDA users in conference centers, hotels, airports and coffee houses can surf the web and access email and other applications over the Internet. Home users are using wireless networks to eliminate the need to run cables.
Wireless connectivity provides great flexibility but also presents security risks. Information transmitted through a cable or other wired network is generally secure because one must tap into the cable in order to access the transmission. However, information transmitted wirelessly can be received by anyone with a wireless receiver who is in range. Security risks may not present much of a problem to students reading course material or to cafe customers surfing the World Wide Web, but they present major concerns to businesses and professionals as well as their clients, customers and patients.
Generally, wired and wireless computing worlds operate under very different paradigms. The wired world assumes a fixed address and a constant connection with high bandwidth. A wireless environment, in contrast, exhibits intermittent connections and has higher error rates over what is usually a narrower bandwidth. As a result, applications and messaging protocols designed for the wired world don't always work in a wireless environment. However, the wireless expectations of end users are set by the performance and behaviors of their wired networks. Meeting these expectations creates a significant challenge to those who design and develop wireless networking architectures, software and devices.
Authenticating users and keeping communications confidential are more problematic in a wireless network than they are in a wired network. Wireless networks generally are subject to much greater varieties of attacks (e.g., man-in-the-middle, eavesdropping, “free rides” and wide area imposed threats) and assumptions that often do not apply to wired networks. For example, in modern network topologies such as wireless networks and Internet-based virtual private networks (VPNs), physical boundaries between public and private networks do not exist. In such networks, whether a user has the necessary permissions to access the system can no longer be assumed based on physical location as with a wired network in a secure facility. Additionally, wireless data is often broadcasted on radio frequencies, which can travel beyond the control of an organization, through walls and ceilings and even out into the parking lot or onto the street. The information the network is carrying is therefore susceptible to eavesdropping. Imagine if vital hospital patient information could be intercepted or even altered by an unauthorized person using a laptop computer in the hospital lobby, or if a corporate spy could learn his competitor's secrets by intercepting wireless transmissions from an office on the floor above or from a car in the parking lot. While tapping into a wired network cable in a secure facility is possible, the chances of this actually happening are less likely than interception of radio transmissions from a wireless network. Further security threats and problems must be faced when users wish to use any of the ever-increasing variety of public wireless networks to access sensitive data and applications.
Many of the open standards that make it possible for wireless network hardware vendors to create interoperable systems provide some form of security protection. For example, the IEEE 802.11b “Wi-Fi” standard has been widely implemented to provide wireless connectivity for all sorts of computing devices. It provides an optional Wired Equivalent Privacy (“WEP”) functionality that has been widely implemented. Various additional wireless related standards attempt to address security problems in wireless networks, including for example:
However, as explained below and as recognized throughout the industry, so far these standards have not provided a complete, easy-to-implement transparent security solution for mobile computing devices that roam between different networks or subnetworks.
WAP generally is designed to transmit data over low-bandwidth wireless networks to devices like mobile telephones, pagers, PDA's, and the like. The Wired Transport Layer Security (WTLS) protocol in WAP provides privacy, data integrity and authentication between WAP-based applications. A WAP gateway converts between the WAP protocol and standard web and/or Internet protocols such as HTTP and TCP/IP, and WTLS is used to create a secure, encrypted pipe. One issue with this model is that once the intermediate WAP gateway decrypts the data, it is available in clear text form—presenting an opportunity for the end-to-end security of the system to be compromised. Additionally, WAP has typically not been implemented for high-bandwidth scenarios such as wireless local area network personal computer connectivity.
WEP (Wired Equivalent Privacy) has the goal of providing a level of privacy that is equivalent to that of an unsecured wired local area network. WEP is an optional part of the IEEE 802.11 standard, but many hardware vendors have implemented WEP. WEP provides some degree of authentication and confidentiality, but also has some drawbacks and limitations.
To provide authentication and confidentiality, WEP generally relies on a default set of encryption keys that are shared between wireless devices (e.g., laptop computers with wireless LAN adapters) and wireless access points. Using WEP, a client with the correct encryption key can “unlock” the network and communicate with any access point on the wireless network; without the right key, however, the network rejects the link-level connection request. If they are configured to do so, WEP-enabled wireless devices and access points will also encrypt data before transmitting it, and an integrity check ensures that packets are not modified in transit. Without the correct key, the transmitted data cannot be decrypted—preventing other wireless devices from eavesdropping.
WEP is generally effective to protect the wireless link itself although some industry analysts have questioned the strength of the encryption that WEP currently uses. However, a major limitation of WEP is that the protection it offers does not extend beyond the wireless link itself. WEP generally offers no end-to-end protection once the data has been received by a wireless access point and needs to be forwarded to some other network destination. When data reaches the network access point or gateway, it is unencrypted and unprotected. Some additional security solution must generally be used to provide end-to-end authentication and privacy.
Mobile IP is another standard that attempts to solve some of the problems of wireless and other intermittently-connected networks. Generally, Mobile IP is a standards based algorithm that enables a mobile device to migrate its network point of attachment across homogeneous and heterogeneous network environments. Briefly, this Internet Standard specifies protocol enhancements that allow routing of Internet Protocol (IP) datagrams (e.g., messages) to mobile nodes in the Internet. See for example Perkins, C., “IP Mobility Support”, RFC 2002, October 1996.
Mobile IP contemplates that each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet. While situated away from its home, a mobile node is also associated with a “care-of” address, which provides information about its current point of attachment to the Internet. The protocol provides for registering the “care-of” address with a home agent. The home agent sends datagrams destined for the mobile node through a “tunnel” to the “care-of” address. After arriving at the end of the “tunnel,” each datagram is then delivered to the mobile node.
While Mobile IP provides useful techniques for remote connectivity, it is not yet widely deployed/implemented. This seems to be due to a variety of factors—at least one of which is that there continues to be some unsolved problems or areas where the Mobile IP standard is lacking and further enhancement or improvement would be desirable. For example, even though security is now fairly widely recognized as being a very important aspect of mobile networking, the security components of Mobile IP are still mostly directed to a limited array of security problems such as redirection attacks.
Redirection attacks are a very real threat in any mobility system. For example, a redirection attack can occur when a malicious node gives false information to a home agent in a Mobile IP network (e.g., sometimes by simply replaying a previous message). This is similar to someone filing a false “change of address” form with the Post Office so that all your mail goes to someone else's mailbox. The home agent is informed that the mobile node has a new “care-of” address. However, in reality, this new “care-of” address is controlled by the malicious node. After this false registration occurs, all IP datagrams addressed to the mobile node are redirected to the malicious node.
While Mobile IP provides a mechanism to prevent redirection attacks, there are other significant security threats that need to be addressed before an enterprise can feel comfortable with the security of their wireless network solution. For example, Mobile IP generally does not provide a comprehensive security solution including mobile computing capabilities such as:
While much security work has been done by the Internet community to date in the Mobile IP and other contexts, better solutions are still possible and desirable. In particular, there continues to be a need to provide an easy-to-use, comprehensive mobility solution for enterprises and other organizations who wish to add end-to-end security to existing and new infrastructures that make extensive use of existing conventional technology and standards and which support mobility including roaming transparently to applications that may not be “mobile-aware.” Some solutions exist, but many of them require changes to existing infrastructure that can be difficult to implement and maintain.
For example, in terms of the current implementations that do exist, Mobile IP is sometimes implemented as a “bump” in the TCP/IP protocol stack to replace components of the existing operating system environment. An example of such an architecture is shown in prior art
Another common security solution that enterprises have gravitated toward is something called a Virtual Private Network (VPN). VPNs are common on both wired and wireless networks. Generally, they connect network components and resources through a secure protocol tunnel so that devices connected to separate networks appear to share a common, private backbone. VPN's accomplish this by allowing the user to “tunnel” through the wireless network or other public network in such a way that the “tunnel” participants enjoy at least the same level of confidentiality and features as when they are attached to a private wired network. Before a “tunnel” can be established, cryptographic methods are used to establish and authenticate the identity of the tunnel participants. For the duration of the VPN connection, information traversing the tunnel can be encrypted to provide privacy.
VPN's provide an end-to-end security overlay for two nodes communicating over an insecure network or networks. VPN functionality at each node supplies additional authentication and privacy in case other network security is breached or does not exist. VPN's have been widely adopted in a variety of network contexts such as for example allowing a user to connect to his or her office local area network via an insecure home Internet connection. Such solutions can offer strong encryption such as the AES (Advanced Encryption Standard), compression, and link optimizations to reduce protocol chattiness. However, many or most VPNs do not let users roam between subnets or networks without “breaking” the secure tunnel. Also, many or most VPNs do not permit transport, security and application sessions to remain established during roaming. Another potential stumbling block is conventional operating systems—not all of which are compatible with the protection of existing wireless VPNs.
To address some of the roaming issue, as previously mentioned, standards efforts have defined Mobile IP. However, Mobile IP, for example, operates at the network layer and therefore does not generally provide for session persistence/resilience. If the mobile node is out of range or suspended for a reasonably short period of time, it is likely that established network sessions will be dropped. This can present severe problems in terms of usability and productivity. Session persistence is desirable since it lets the user keep the established session and VPN tunnel connected—even if a coverage hole is entered during an application transaction. Industry analysts and the Wireless Ethernet Compatibility Alliance recommend that enterprises deploy VPN technology, which directly addresses the security problem, and also provides advanced features like network and subnet roaming, session persistence for intermittent connections, and battery life management for mobile devices. However, VPN solutions should desirably support standard security encryption algorithms and wireless optimizations suitable for today's smaller wireless devices, and should desirably also require no or minimal modification to existing infrastructure.
One standards-based security architecture and protocol approach that has been adopted for providing end-to-end secure communications is called “Internet Security Protocol” (“IPSec”). IPSec is a collection of open standards developed by the Internet Engineering Task Force (IETF) to secure communications over public and private networks. See for example:
Briefly, IPSec is a framework for ensuring private, secure communications over Internet Protocol (IP) networks, through the use of cryptographic security services. The IPSec suite of cryptography-based protection services and security protocols provides computer-level user and message authentication, as well as data encryption, data integrity checks, and message confidentiality. IPSec capabilities include cryptographic key exchange and management, message header authentication, hash message authentication, an encapsulating security payload protocol, Triple Data Encryption, the Advanced Encryption Standard, and other features. In more detail, IPSec provides a transport mode that encrypts message payload, and also provides a tunnel mode that encrypts the payload, the header and the routing information for each message. To reduce overhead, IPSec uses policy-based administration. IPSec policies, rather than application programming interfaces (APIs), are used to configure IPSec security services. The policies provide variable levels of protection for most traffic types in most existing networks. One can configure IPSec policies to meet the security requirements of a computer, application, organizational unit, domain, site, or global enterprise based on IP address and/or port number.
IPSec is commonly used in firewalls, authentication products and VPNs. Additionally, Microsoft has implemented IPSec as part of its Windows 2000 and Windows XP operating system. IPSec's tunnel mode is especially useful in creating secure end-to-end VPNs. IPSec VPNs based on public key cryptography provide secure end-to-end message authentication and privacy. IPSec endpoints act as databases that manage and distribute cryptographic keys and security associations. Properly implemented, IPSec can provide private channels for exchanging vulnerable data such as email, file downloads, news feeds, medical records, multimedia, or any other type of information.
One might initially expect that it should be relatively straightforward to add a security algorithm such as the standards-based IPSec security algorithm to Mobile IP or other mobility protocol. For example, layering each of the entities in the fashion such as that shown in prior art
For example, when the mobile node has roamed to a foreign network and is communicating with its ultimate peer, it is possible that packets generated by the mobile node may be discarded by a policy enforcement entity such as a firewall. This can be due to common practice known as ingress filtering rules. Many firewalls discard packets generated by mobile nodes using their home addresses (internal network identity) and received on an externally facing network interface in defense of the network. This discarding process is intended to protect the network secured by the firewall from being attacked. Ingress filtering has the effect of forcing the tunneling of Mobile IP frames in both directions. See for example RFC 2356 Sun's SKIP Firewall Traversal for Mobile IP. G. Montenegro, V. Gupta. (June 1998).
Additionally, it is becoming general practice in the industry to require that an IPSec security session be established between the foreign agent and the externally facing policy enforcement equipment (e.g. firewall) before allowing packets to traverse between the external and internal network interconnection (a.k.a. VPN). If the foreign agent is co-located with the mobile node, this can become a cumbersome operation. As exemplary
What is needed is a solution to these problems providing security, network roaming, and session persistence over conventional information communications networks including but not limited to standard IP based networks without requiring modification to existing network applications. Additionally, it would be useful if such a solution did not require the deployment of Mobile IP or any additional infrastructure such as a foreign agent when visiting a remote network, and the functionality can be transparent to networked applications so they do not need to be modified either.
This invention solves this problem by transparently providing secure, persistent, roamable IP-based communications using conventional technologies such as IPSec, Microsoft or other operating system security functionality while avoiding the commonly experienced ingress filtering problems. And unlike at least some implementations of Mobile IP, few if any changes are necessary to the underlying network infrastructure.
Generally, one preferred exemplary non-limiting embodiment provides Mobility Client (MC) functionality that virtualizes the underlying network. Applications running on the mobility client see at least one consistent virtual network identity (e.g. IP address). When an application on the mobility client makes a network request, the mobility client intercepts the request and marshals the request to a Mobility Server (MS) that supports security such as IPSEC. The mobility server unwraps the request and places it on the network as though the server were the client—thus acting as a proxy for the client.
The reverse also occurs in the exemplary embodiment. When a peer host sends a packet to the mobility client's virtual network identity, the packet is first received by the mobility server and is then transferred to the mobility client. The mobility server maintains a stable point of communication for the peer hosts while the mobility client is free to roam among networks as well as suspend or roam out of range of any network. When the mobility client is out of range, the mobility server keeps the mobility client's sessions alive and queues requests for the mobility client. When the mobility client is once again reachable, the mobility server and client transfer any queued data and communication can resume where it left off.
Preferred exemplary non-limiting implementations thus offer wireless optimizations and network and application session persistence in the context of a secure VPN or other connection. Wireless optimizations allow data to be transmitted as efficiently as possible to make maximal use of existing bandwidth. For example, the system can be used to switch automatically to the fastest bandwidth network connection when multiple connections (Wi-Fi and GPRS, for example) are active. Network session persistence means that users don't have to repeat the login process when they move from one IP subnet to another, or when they go out of range of the network and return. Exemplary implementations automatically re-authenticate the connection every time users roam, without need for user intervention. Application session persistence means that standard network applications remain connected to their peers, preventing the loss of valuable user time and data. Such optimizations and persistence is provided in the context of a security architecture providing end-to-end security for authentication and privacy.
In one illustrative embodiment, before data is transported between the network and a mobility client, the network ensures that the end user has the required permissions. A user establishes her identity by logging in to the mobility client using a conventional (e.g., Windows) domain user name and password. Using the conventional domain credentials allows for a single sign-on process and requires no additional authentication tables or other infrastructure additions. Single sign-on also gives users access to other domain resources such as file system shares. Once a user has been authenticated, a communications path is established for transporting application data. Any number of different protocols (e.g., Common Internet File System, Radius, other) can be used for user authentication. Using certain of these protocols, a mobility server can act as a Network Access Server to secure an initial access negotiation which establishes the user's user name and password using conventional protocols such as EAP-MD5, LEAP, or other protocol. Unlike some wireless protocols, such authentication in the exemplary non-limiting implementations provides user-specific passwords that can be used for policy management allowing access and resource allocation on a user basis.
Significantly, exemplary non-limiting implementations can be easily integrated with IPSEC or other security features in conventional operating systems such as for example Windows NT and Windows 2000. This allows access to conventional VPN and/or other proven-secure connection technology. IPSec policies can be assigned through the group policy feature of Active Directory, for example. This allows IPSec policy to be assigned at the domain or organizational level—reducing the administrative overhead of configuring each computer individually. An on-demand security negotiation and automatic key management service can also be provided using the conventional IETF-defined Internet Key Exchange (IKE) as specified in Internet RFC 2409. Such exemplary implementations can provide IEFT standards-based authentication methods to establish trust relationships between computers using public key cryptography based certificates and/or passwords such as preshared keys. Integration with conventional standards-based security features such as public key infrastructure gives access to a variety of security solutions including secure mail, secure web sites, secure web communications, smart card logon processes, IPSec client authentication, and others.
Illustrative exemplary embodiments can be cognizant of changes in network identity, and can selectively manage transition in network connectivity, possibly resulting in the termination and/or (re)instantiation of IPSec security sessions between communicating entities over at least one of a plurality of network interfaces. Exemplary illustrative embodiments also provide for the central management, distribution, and/or execution of policy rules for the establishment and/or termination of IP security sessions as well as other parameters governing the behavior for granting, denying and/or delaying the consumption of network resources.
Illustrative non-limiting advantageous features include:
These and other features and advantages may be better and more completely understood by referring to the following detailed description of exemplary non-limiting illustrative embodiments in conjunction with drawings, of which:
FIGS. 5 & 5A-5F show illustrative usage scenarios;
In one exemplary embodiment, mobility client MC may be coupled to a network such as the Internet, a corporate LAN or WAN, an Intranet, or any other computer network. Such coupling can be wirelessly via a radio communications link such as for example a cellular telephone network or any other wireless radio or other communications link. In some embodiments, mobility client MC may be intermittently coupled to the network. The system shown is not, however, limited to wireless connectivity—wired connectivity can also be supported for example in the context of computing devices that are intermittently connected to a wired network. The wireless or other connectivity can be in the context of a local area network, a wide area network, or other network.
In the exemplary embodiment, mobility client MC communicates with the network using Internet Protocol (IP) or other suitable protocol over at least one of a plurality of possible network interfaces. In the illustrative embodiment, mobility server (MS) is also connected to the network over at least one of a plurality of possible network interfaces. The mobility server MS may communicate with one or more peers or other computing devices. The exemplary
In more detail, the
The exemplary mobility server also manages network addresses for the mobile devices. Each device running on the mobile device has a virtual address on the network and a point of presence address. A standard protocol (e.g., DHCP) or static assignment determines the virtual address. While the point of presence address of a mobile device will change when the device moves from one subnet to another (the virtual address stays constant while the connections are active).
This illustrative arrangement works with standard transport protocols such as TCP/IP—intelligence on the mobile device and the mobility server assures that an application running on the mobile device remains in sync with its server.
The mobility server also provides centralized system management through console applications and exhaustive metrics. A system administrator can use these tools to configure and manage remote connections, troubleshoot problems, and conduct traffic studies.
The mobility server also, in the exemplary embodiment, manages the security of data that passes between it and the mobile devices on the public airways or on a wireline network. The server provides a firewall function by giving only authenticated devices access to the network. The mobility server can also certify and optionally encrypt all communications between the server and the mobile device. Tight integration with Active Directory or other directory/name service provides centralized user policy management for security.
The
The scenarios described above are only illustrative—any number of other intermittent, mobile, nomadic or other connectivity scenarios could also be provided.
Exemplary Integration With IPSec Standards-Based Security Framework
Generally, the IPSec process of protecting frames can be broadly handled by three logically distinct functions. They are:
Although these processes are logically distinct, the responsibility for implementing the functionality may be shared by one or more modules or distributed in any manner within an operating or other system. For instance, in the exemplary illustrative client operating system embodiment, the implementation is broken into 3 functional areas or logical modules:
In this illustrative example, the Policy Agent is responsible for the configuration and storage of the configured policy—however it is the IPSec module that actually acts upon the requested policy of the Policy Agent. The preferred exemplary illustrative system provides two different related but separated aspects:
We first discuss exemplary illustrative communication to and from the mobility client.
As part of the preferred embodiment's overall design, network roaming activity is normally hidden from the applications running on the mobility client—and thus, the application generally does not get informed of (or even need to know about) the details concerning mobility roaming. Briefly, as described in the various copending commonly-assigned patent applications and publications referenced above, each of the mobile devices executes a mobility management software client that supplies the mobile device with the intelligence to intercept network activity and relay it (e.g., via a mobile RPC or other protocol) to mobility management server. In the preferred embodiment, the mobility management client generally works transparently with operating system features present on the mobile device to keep client-site application sessions active when contact is lost with the network. A new, mobile interceptor/redirector component is inserted at the conventional transport protocol interface of the mobile device software architecture. While mobile interceptor/redirector could operate at a different level than the transport interface, there are advantages in having the mobile interceptor/redirector operate above the transport layer itself. This mobile interceptor or redirector transparently intercepts certain calls at this interface and routes them (e.g., via RPC and Internet Mobility Protocols and the standard transport protocols) to the mobility management server over the data communications network. The mobile interceptor/redirector thus can, for example, intercept network activity and relay it to server. The interceptor/redirector works transparently with operating system features to allow application sessions to remain active when the mobile device loses contact with the network.
This arrangement provides an advantageous degree of transparency to the application, to the network and to other network sources/destinations. However, we have found that IPSec is a special case. Between the mobility client and the mobility server or the mobility client and a firewall, IPSec is protecting the packets using the point-of-presence (POP) address. Therefore, in one exemplary embodiment, to allow the existing IPSec infrastructure to operate normally, it should preferably remain informed of the current state of the network. We have therefore modified our previous design to inform IPSec of the change of network status (e.g., so it can negotiate a IPSec session when network connectivity is reestablished) while continuing to shield the networked application and the rest of the operating system from the temporary loss of a network access. Before describing how that is done in one illustrative embodiment, we first explain—for purposes of illustration only the conventional Microsoft Windows 2000/XP operating system IPSec architecture shown in
In Windows 2000/XP, the IPSec module is responsible for filtering and protecting frames. For additional information, see for example Weber, Chris, “Using IPSec in Windows 2000 and XP” (Security Focus 12/5/01). Briefly, however, by way of non-limiting illustrative example, before allowing a frame to be processed by the protocol stack or before transmitting the frame out on the network, the network stack first allows the IPSec module a chance to process the frame. The IPSec module applies whatever polices to the frame the Policy Agent requests for the corresponding network identity. In the event that the Policy Agent requires the IPSec module to protect a frame but it does not yet have the required security association (SA) with the peer in accordance with the requested policy, it issues a request to the security negotiation/key management module—in this illustrative case the ISAKMP/IKE (Internet Security Association and Key Management Protocol/Internet Key Exchange) module—to establish one. It is the responsibility of the ISAKMP/IKE module in this illustrative system to negotiate the requested security association and alert the IPSec (privacy) module as to the progress/status of the security association. Once the security association has been successfully established, the IPSec module continues its processing of the original frame.
In the illustrative embodiment, the Policy Agent uses conventional Microsoft Winsock API's (application programming interfaces) to monitor the state of the network and adjust its policies accordingly. However this is implementation-dependent as other interfaces may also be used to alert this logical component of the network state in other environments. Accordingly, the ISAKMP/IKE module also uses conventional Microsoft Winsock API's to perform security association negotiation as well as track network state changes in one exemplary embodiment.
Briefly, the above techniques establish a secure IPSec session that is generally tied to a particular IP address and/or port and must be essentially continuous in order to be maintained, as is well known. If the secure session is temporarily interrupted (e.g., because of a lost or suspended connection or a roam) and/or if the IP address and/or port changes, IPSec will terminate it. Unless something is done, terminating the secure IPSec session will cause the mobile application to lose communication even if the network session continues to appear to remain in place. The preferred illustrative exemplary embodiment solves this problem by introducing functionality ensuring that IPSec is passed sufficient information to allow it to react to-the secure session being lost while continuing to shield this fact from the application—and by allowing IPSec to (re)negotiate a secure session once the network connectivity is reestablished using the same or different IP address or port number—all transparently to the networked application. In this way, the exemplary illustrative application is not adversely affected by termination of a previous security session and the establishment of a new one—just as the application is not adversely affected by access to the previous network being terminated and then reestablished (or in the case of roaming, to a new network with a new network identity being provisioned in its place). Meanwhile, the mobility server during such interruptions continues to proxy communications with the peer(s) the mobile device is communicating with so that network application sessions are maintained and can pick up where they left off before the interruption occurred.
Mobility client-side and server-side support each have different requirements. Therefore the architectures are different in the exemplary illustrative embodiment. The block diagram of an exemplary client architecture is show in
Briefly, in the preferred illustrative embodiment, the network-virtualizing component virtualizes the underlying client module network while selectively allowing the core operating system's IPSec infrastructure to continue to be informed about network state changes. In the illustrative embodiment, the Policy Agent Hooking component “hooks” certain Policy Agent functions and redirects such processing to the network-virtualizing component so that the normal function of IPSec can be somewhat modified.
In more detail, in the exemplary embodiment, the network-virtualizing component (nmdrv) uses the services of the existing networking stack and is the layer responsible for virtualizing the underlying client module network. It also initiates and maintains the connection with the mobility server. When a client network application asks for the list of local IP addresses, the network-virtualizing component (nmdrv) intercepts the request and returns at least one of a possible plurality of the mobility client's virtual network identities (e.g. virtual IP addresses).
However, to continue to allow the inherent IPSec components to operate in a normal fashion, the client architecture should preferably allow the associated IPSec modules to see and track the current point of presence (POP) network address(es). Therefore, in the exemplary embodiment, if a request for the list of network addresses is issued and the request originated in the IPSec process, the network-virtualizing module passes the request along to an inherent network stack without any filtering or modification. Therefore, both the Policy Agent (e.g., polagent.dll in Windows 2000, ipsecsvc.dll in Windows XP) and the ISAKMP/IKE module are kept abreast of the mobility client's current POP address(es).
In the exemplary embodiment, the network-virtualizing module also tracks address changes. Without this component, the network stack would normally inform any associated applications of address list changes through the conventional application-programming interface, possibly by terminating the application communications end point. In the Microsoft operating systems, for example, this responsibility is normally funneled through the conventional Winsock module, which in turn would then inform any interested network applications of the respective changes. In the exemplary embodiment, the Policy Agent registers interest with Winsock (e.g., using the SIO_ADDRESS_LIST_CHANGE IOCTL via the conventional WSAIoctl function) and waits for the associated completion of the request. The Policy Agent may also be event driven and receive asynchronous notification of such network state changes. Again, in the illustrative exemplary embodiment, the Policy Agent also registers with Winsock a notification event for signaling (e.g., on FD_ADDRESS_LIST_CHANGE via the WSAEventSelect function). When the Policy Agent is alerted to an address list change, it retrieves the current list of addresses, adjusts its policies accordingly and updates the associated policy administration logic. It further informs the Security Negotiation/Key Exchange module, in this case the ISAKMP/IKE module, of the associated state change. The security negotiation/key exchange module (ISAKMP/IKE) module, in turn, updates its list of open connection endpoints for subsequent secure association (SA) negotiations.
In the exemplary embodiment, Winsock and associated applications are normally not allowed to see address list changes since this may disrupt normal application behavior and is handled by the network-virtualizing component. Therefore, in the preferred exemplary embodiment, another mechanism is used to inform the Policy Agent of changes with respect to the underlying network. To fulfill this requirement in the illustrative embodiment, the services of the Policy Agent Hooking module (nmplagnt) are employed.
To achieve the redirection of services, the illustrative embodiment employs the facilities of a hooking module (nmplagnt), and inserts the code into the policy administration, security negotiation, and key management (Policy Agent/ISAKMP/IKE) process(es) that are provided as part of the core operating system. In this illustrative embodiment, hooking only certain functions of the Policy Agent module to this redirected code is accomplished via a combination of manipulating the Import Address Table (IAT) together with the use of a technique known as code injection. Injection of the redirected functions is accomplished with the help of conventional operating system APIs (e.g. OpenProcess, VirtualAllocEx, ReadProcessMemory, WriteProcessMemory, and CreateRemoteThread) in the exemplary embodiment. In the preferred exemplary embodiment, once nmplagnt.dll is injected in lsass.exe executable module, it hooks LoadLibrary and FreeLibrary entries in lsasrv.dll so it can detect when the policy agent is loaded and unloaded. Of course, other implementations are possible depending on the particular operating environment.
Furthermore, the hooking technique in the illustrative embodiment takes advantage of the way in which the Microsoft Windows itself performs dynamic run-time linking. Generally, to facilitate code reuse, Microsoft Windows supports and uses extensively, Dynamic Link Libraries (DLLs). Through the use of DLL technology, a process is able to link to code at run-time. To call a function in a dynamically linked library, the caller must know the location (address) of the specific function in the DLL. It is the operating systems responsibility to resolve the linkage between the code modules and is accomplished via an exchange of formatted tables present in both the caller and callee's run-time code modules. The dynamic library being called contains an Export Address Table (EAT). The Export Address Table contains the information necessary to find the specifically requested function(s) in the dynamic library. The module requesting the service has both an Import Lookup Table (ILT) and an Import Address Table (IAT). The Import Lookup Table contains information about which dynamic library are needed and which functions in each library are used. When the requesting module is loaded into memory for whatever reason, the core operating system scans the associated Import Lookup Table for any dynamic libraries the module depends on and loads those DLLs into memory. Once the specified modules are loaded, the requesting modules Import Address Table is updated by the operating system with the address(location) of each function that maybe accessed in each of the dynamically loaded libraries. Once again, in other environments, different implementations are possible.
In the exemplary embodiment, after the nmplagnt module is loaded by the prescribed method above, it hooks the Policy Agent's calls to the conventional Microsoft Windows Winsock functions WSASocket, WSAIoctl, WSAEventSelect, closesocket, and WSACleanup. After this process is executed, whenever the Policy Agent module attempts to register for notification of address changes, the request is redirected to the network-virtualizing component. As previously mentioned, the network-virtualizing component by design is aware of changes in network attachment. When it detects a change to the point of presence address, it sends the appropriate notifications to the Policy Agent module. In the illustrative embodiment, this causes the Policy Agent module to query for the current address list. Thus, the Policy Agent and consequently the ISAKMP/IKE module are informed of any address list changes.
In summary, the illustrative embodiment in one exemplary detailed implementation performs the following steps:
The address of the LoadLibrary function was determined in step 2. The data bytes at label targetlibraryname will vary depending on the name of the module being loaded, where the corresponding module is located, and the operating system environment.
At the end of these steps, the nmplagnt module has been injected into the policy administration, security negotiation, and key management (Policy Agent/ISAKMP/IKE) process(es) where it is able to redirect the processing of the needed function calls. It is understood that the above code procedure is operating system and processor dependent and is only shown for illustrative purposes, thus not limiting to this specific sequence or operation. Furthermore, the executable code responsible for adding these components to the operating environment can be provided to the mobile device via storage on a storage medium (e.g., optical disk) and/or by downloading over the network
A similar method is employed using the FreeLibrary function instead of LoadLibrary function to reverse the hooking process and to unload the nmplagnt module. For the sake of brevity, the description is kept minimal, as anyone schooled in the art should be able to achieve the desired results.
Using IPSec methodology for communication between the mobility server and peer hosts is a different set of problems to solve—although it uses some of the same techniques used on the mobility client.
In the exemplary mobility server, a proxy driver (nmproxy) can be used to implement the bulk of the mobility server functionality. However, in one exemplary implementation, there are three separate problems to solve for which three additional logical modules are used. They are:
The first problem is how to manage virtual addresses for the mobility clients. Although it is possible in some network stack implementations to assign multiple addresses to the inherent networking stack components of the operating system, some systems do not support such functionality. To support the more restrictive implementation, the illustrative example embodiment employs the use of an identity mapping technique. It will be appreciated that the techniques herein are both compatible with and complimentary to either implementation, and such identity mapping functionality allows the security functionality to successfully operate within the more restrictive environments. The illustrative mobility server opens a communications endpoint associated with a local address and port and then identity maps between the corresponding virtual address(es) and port(s) before packets are processed by the protocol stack during reception and before they are transmitted out on the network. That mapping is the job of the network identity mapping module (nmprtmap) in one exemplary embodiment. For example, assume an application on a mobility client opens TCP port 21 on virtual address 10.1.1.2. Through the use of previously-defined mechanisms (see for example U.S. patent application Ser. No. 09/330,310 filed Jun. 11, 1999, entitled “Method And Apparatus For Providing Mobile and Other Intermittent Connectivity In A Computing Environment), this request is transferred from the mobility client to the mobility server. In response, the MS opens the connection on its local address 10.1.1.1 on port 2042 and registers the appropriate mapping with the network identity mapping module. When the mobile client together with proxy driver (nmproxy) then wishes to send data on its newly opened connection, the packet generated by the inherent networking stack will have a source address of 10.1.1.1 port 2042. The network identity mapping module will then match the frame's protocol/address/port tuple against its mapping table and replace the source address with 10.1.1.2 port 21 before the packet is transmitted on network. The reverse operation is performed for received packets. Using this network identity mapping technique allows the mobility server to communicate to peer systems using virtualized addresses without requiring modification to the core operating system transport protocol stack
The second problem is a direct result of this mapping technique. Because the network identity mapping module logically operates below IPSec module (i.e. processes frames before during reception and after during transmission), it cannot directly manipulate IPSec protected frames without corrupting the packets or being intimately involved in the privacy or authenticating process. To address this issue, in one exemplary embodiment, the aforementioned IPSec filter module (nmipsec) inserts itself between the operating systems networking stack components and the associated IPSec modules. The filter module inspects each outgoing packet before IPSec protects the packet and each incoming packet after IPSec removes any encoding. Once in control of the frame, it consults the network identity mapping module(nmprtmap) to determine whether or not the frames source or destination identity should be mapped. In this way, the functionality of the mapping logic is moved to a level where is can perform its function without interfering with the IPSec processing.
Hooking the link between the IPSec and networking stack components is implementation and operating system dependent. In the illustrative exemplary embodiment, again the hooking process is completed by the manipulation of tables that are exchanged between the inherent IPSec and networking stack modules—but other implementations and environments could rely on other techniques. In the illustrative embodiment the IPSec filter module (nmipsec) loads before the IPSec module but after the transportprotocol module. When the IPSec module attempts to exchange its function table with the transport protocol components, the IPSec filter module (nmipsec) records and replaces the original function pointers with it's own entry points. Once the associated tables are exchanged in this manner, the IPSec filter module (nmipsec) can manipulate the contents of and control which packets the inherent IPSec module operates on.
The third issue is where the hooking techniques also used by the mobility clients is employed. As mentioned previously, due to the mapping technique employed in one exemplary implementation, the inherent networking stack has no knowledge of the mobility client's virtual address(es). Consequently, the policy administration, security negotiation, and key management (Policy Agent/ISAKMP/IKE module) process(es) are also not cognizant of these additional known network addresses. Therefore, there are no IPSec security policies to cover frames received for or transmitted from the mobility client's virtual address(es). Furthermore the security negotiation module (in this case the ISAKMP/IKE module) has no communications end point opened for which to negotiate security associations for the mobility client. To address this issue in the exemplary embodiment, the security negotiation hooking module(nmike) can employ the same hooking methodology described for the mobility client and illustrated in
All documents referenced herein are incorporated by reference as if expressly set forth herein.
While the invention has been described in connection with practical and preferred embodiments, it is not to be so limited. Specifically, for example, the invention is not limited to IPSec or Microsoft operating systems. IPSec and related technologies can be arranged in a number of manners, executing with some of the required algorithms executing either in software or hardware. To wit, certain implementations may include hardware accelerator technology for the ciphering process, etc. Many network interface and computer manufactures have commercially available products that are used for this exact purpose. It is to be appreciated that the above specifications however describes the logical placement of required functionally and may actually execute in a distributed fashion. Accordingly, the invention is intended to cover all modifications and equivalent arrangements within the scope of the claims.
This application claims the benefit of priority from the following copending commonly-assigned related U.S. patent applications: U.S. Provisional Application No. 60/347,243, filed Jan. 14, 2002; U.S. Provisional Application Ser. No. 60/274,615 filed Mar. 12, 2001, entitled “Method And Apparatus For Providing Mobile and Other Intermittent Connectivity In A Computing Environment”; U.S. patent application Ser. No. 09/330,310 filed Jun. 11, 1999, entitled “Method And Apparatus For Providing Mobile and Other Intermittent Connectivity In A Computing Environment”; U.S. patent application Ser. No. 09/660,500 filed Sep. 12, 2000, entitled “Method And Apparatus For Providing Mobile and Other Intermittent Connectivity In A Computing Environment”; and PCT International Application Number PCT/US01/28391 filed Sep. 12, 2001, entitled “Method And Apparatus For Providing Mobile And Other Intermittent Connectivity In A Computing Environment”. All of the above-identified documents are incorporated herein by
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