Method of virtual private network communication in security gateway apparatus and security gateway apparatus using the same7028337Abstract A method of the Virtual Private Network (VPN) communication employed for a security gateway apparatus and the security gateway apparatus using the same, which allow a personal computer outside a local area network (LAN) to access, via a WAN, to a terminal on the LAN, virtually regarding the outside PC as a terminal on the LAN. The communication method is employed for a security gateway apparatus to connect, through concentration and conversion process, between a LAN and a WAN including a public network. Security Architecture for the Internet Protocol (IPsec) establishes VPN with an outside PC having a dialup connection to the WAN. During an Internet Key Exchange (IKE) communication that is performed prior to the IPsec communication, the security gateway apparatus integrates a Dynamic Host Configuration Protocol (DHCP) communication option into an IKE data, and designates the IP address of the outside PC from a tunneled IP packet. Claims What is claimed is: Description FIELD OF THE INVENTION
There are two methods of sharing key information on both sides of communication partners: (1) setting the key information manually on both sides prior to communication, and (2) setting the key information automatically with the Internet Key Exchange (IKE) protocol on initiating communication. Hereinafter will be focused on the latter method, which is practically used in actual communication. The IPsec communication will be described with reference to FIG. 7. FIG. 7 is a flow diagram that illustrates the working of security gateway 103 for starting the IPsec communication. To perform the IPsec communication, it is necessary to establish Security Association (SA) that is a two-way logical connection between the both sides. For that reason, the IKE communication has two phases. Phase 1 is to establish IKE-SA for performing the IKE communication with safety (S11, S12). With the connection established successfully, phase 2 will be in active for exchanging security information including key information for the IPsec communication (S13). When IPsec—SA is successfully established (S14) in phase 2, the IKE communication is over then IPsec communication initiates.(S15). The table below shows the information to be exchanged between the both sides, in phase 2 of IKE communication (indicated by S13 in the description above.)
As for the operating mode (IPsec communication mode), security gateway 103 is in active in the tunnel mode (encapsulating whole IP packets) only. In the explanation below, the IPsec operating mode is assumed to be the tunnel mode. FIG. 8 schematically illustrates of the IPsec communication in the tunnel mode. In FIG. 8, PC 101, security gateway 103, LAN 104, client PC 106, and VPN 108 are the same as those illustrated in FIG. 5. IP packet 100 is handled in this system. In FIG. 8, suppose that IP addresses "A", "B", and "C" are assigned to PC 101, security gateway 103, and client PC 106, respectively. IP address "A" assigned to PC 101 is provided from the provider. When client PC 106 on LAN 104 transmits an IP packet to PC 101, which has established connection with PC 106 via VPN 108,
The VPN communication method in the prior-art security gateway apparatus assures safety of data exchanging on WAN 102. However, an access from outside of the LAN is treated as the access from an outside network. The fact has brought an inconvenience or some security problems described below when a terminal outside the LAN tries to establish a dialup connection to the WAN and accesses to client PC 106 on LAN 104.
Besides, if LAN 104 is a network configured with private IP addresses, the setting procedures would be extremely complicated. SUMMARY OF THE INVENTION The present invention addresses the problems above. It is therefore the object of the present invention to provide a VPN communication method in a security gateway apparatus, allowing a PC outside a LAN, virtually regarded as a PC on the LAN, to communicate with a terminal on the LAN. The present invention provides a VPN communication method in a security gateway apparatus that connects, via line connection and conversion processing, between a LAN and a WAN that is typically configured by a public network. According to the present invention, during the procedure in which the IPsec protocol establishes the VPN communication between a security gateway apparatus and an outside PC having a dialup connection with a WAN, the security gateway apparatus integrates the Dynamic Host Configuration Protocol (DHCP) communication option into the IKE data during the IKE communication prior to the IPsec communication. Through the procedure, the security gateway apparatus can designate the IP address of the outside terminal in a tunneled IP packet. In this way, the present invention allows an outside terminal to communicate with a terminal on the LAN, by virtually regarding the outside terminal as another terminal on the LAN. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates diagrammatically an IPsec communication in accordance with a first preferred embodiment of the present invention. FIG. 2 is a flow chart indicative of the procedure in which a security gateway apparatus distributes an IP address to an outside PC. FIG. 3 shows a data format for the IKE communication used for the VPN communication method in the security gateway apparatus in accordance with the first preferred embodiment. FIG. 4 is a block diagram of the security gateway apparatus of the present invention. FIG. 5 shows a prior art typical network system including a WAN. FIG. 6 shows a prior art configuration in which an outside PC and the security gateway apparatus are connected via a WAN. FIG. 7 is a flow chart indicative of the working steps of the prior art security gateway apparatus to initiate the IPsec communication. FIG. 8 illustrates diagrammatically of the prior art IPsec communication in the tunnel mode. DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention are described hereinafter with reference to the accompanying drawings, FIG. 1 through FIG. 3. First Preferred Embodiment FIG. 3 shows a data format for the IKE communication used for the VPN communication method in the security gateway apparatus in accordance with the first preferred embodiment. The IKE communication is performed with User Datagram Protocol (UDP)/Internet Protocol (IP). As shown in FIG. 3, the IKE data is formed of the Internet Security Association and Key Management Protocol (ISAKMP) header and a series of the ISAKMP payloads that follows the ISAKMP header. The IKE communication is performed between an initiator requesting key exchange, and a responder responding to the request. According to the embodiment, FIG. 1 shows PC 101 as an example of a terminal connecting the Internet via a provider. Served as an initiator, PC 101 initiates the IKE communication with security gateway 203 in order to access client PC 106 on LAN 104. On the other hand, security gateway 203 serves as a responder in the communication. The communication is performed in the form of server/client model. As for the Encryption key and the Authentication key in the items listed in Table 1, key information is exchanged between the initiator and the responder, using a public key cryptosystem. As for the rest of the items, the initiator gives suggestions to the responder, and the responder responds to the initiator with the best among the suggestions. There are some pieces of information essential to PC 101 as a Dynamic Host Configuration Protocol (DHCP) client: (i) an IP address; (ii) a subnet mask; (iii) an expiration date of the IP address; and (iv) a domain name. Security gateway 203, which serves as the responder in the IKE communication, adds these four items to a normally formed IKE data as an option. Of the four items, the expiration date of the IP address may be omitted from the option added to the IKE data, by regarding that the expiration date is equivalent to the SA life time that is established by the IKE communication. DHCP is an application protocol positioned in the higher layer than UDP belongs to, so that it runs on the IKE without problems associated with resending control or other functions. FIG. 1 illustrates diagrammatically the IPsec communication in accordance with the first preferred embodiment of the present invention. The interconnection of PC 101, security gateway 203, LAN 104, client PC 106, and VPN 208 in FIG. 1 is the same as that of PC 101, security gateway 103, LAN 104, client PC 106, and VPN 108 in FIG. 5. In FIG. 1, suppose that IP addresses "A", "B", and "C" are assigned to PC 101, security gateway 203, and client PC 106, respectively. IP address "A" assigned to PC 101 is provided from the provider. Security gateway 203 distributes IP address "D" to PC 101 during the IKE communication prior to the IPsec communication. When client PC 106 on LAN 104 transmits an IP packet to PC 101 having connection via VPN 208, the transmission is performed following the steps below:
FIG. 2 is a flow chart illustrating the procedure in which security gateway 203 establishes the IKE communication and IPsec—Security Association (SA) connections to initiate the IPsec communication, and distributes IP address "D" to PC 101. To perform the IPsec communication, it is necessary to establish SA that is a two-way logical connection between the both sides. For that reason, the IKE communication has two phases. Phase 1 is to establish IKE-SA for performing the IKE communication with safety (S1, S2). With the connection established successfully, phase 2 will be in active for exchanging security information including key information for the IPsec communication (S3). In phase 2, IPsec—SA is established and the DHCP option is added to the IKE data (S4). Following the completion of distributing IP address "D" to PC 101 (S5), the IKE communication is over. Table 1 shows required information for the IPsec communication, which is exchanged between the both sides during the IKE (phase 2) communication in step S3. According to the embodiment, as described above, in the procedure that the gateway apparatus establishes VPN 208 connection, using the IPsec protocol, with PC 101 having a dialup connection to WAN 102, the gateway apparatus integrates the DHCP communication option into the IKE data during the IKE communication prior to the IPsec communication. Through the procedure, the security gateway apparatus can designate, from a tunneled IP packet, the sender's IP address "C" to be processed in the IPsec communication. When establishing the IPsec communication with outside PC 101 having a dialup connection with the WAN, security gateway 203 thus controls IP address "A" of the outside PC as the final destination. As an advantage, the need for setting of client PC 106 on LAN 104 can be eliminated in this procedure. This fact promises a highly safeguarded communication without interception or alteration of transmitting information. Second Preferred Embodiment Here will be described the VPN communication method employed for the security gateway apparatus in accordance with the second preferred embodiment, referring to FIG. 1. During the distribution process of DHCP information to PC 101, security gateway 203 distributes to PC 101 an IP address and a subnet mask having the same segment as those of LAN 104 controlled by security gateway 203. In this procedure, security gateway 203 serves as the responder, while PC 101 serves as the initiator in the IKE communication. In the IPsec communication after VPN 208 establishment, PC 101, which accesses from the outside of LAN 104, can behave as if being a standalone terminal that has the "same" segment as a terminal on the network has, in communicating with client PC 106 controlled by security gateway 203. According to the embodiment, as described above, security gateway 203 distributes to PC 101, which accesses from outside the LAN 104 by establishing a dialup connection, an IP address and a subnet mask which have the same segment as those used on LAN 104 controlled by security gateway 203 in the IKE communication. This allows outside PC 101 to virtually work on LAN 104 in the VPN communication. The fact that outside PC 101 which has established VPN 208 works as if being in the LAN 104 environment realizes the access from an outside terminal to a terminal on LAN 104 with security. Third Preferred Embodiment Now will be described the VPN communication method employed for the security gateway apparatus in accordance with the third preferred embodiment, referring to FIG. 1. In FIG. 1, the explanation is focused on the case, in which security gateway 203 employs the Network Address Translator (NAT) technology and configures LAN 104 with private IP addresses. In this case, an access from an outside terminal to client PC 106 on LAN 104 is usually not allowed. However, the following method makes it possible. First, PC 101 having a dialup connection establishes the IKE communication with security gateway 203 for VPN 208 establishment. During the IKE communication, security gateway 203 integrates a private IP address into the IKE data as a DHCP option. The private IP address is an unused one in the segment that is allocated to LAN 104 controlled by security gateway 203. Then gateway 203 distributes the IKE data to PC 101. Through this procedure, PC 101 uses a global IP address in VPN 208 on WAN 102, while it manipulates a private IP address on LAN 104 and inside PC 101 itself. This allows PC 101 to behave as if being a standalone terminal that has the "same" segment as a terminal on the network does. According to the embodiment, as described above, gateway 203 distributes to outside PC 101, through the NAT technology, a private IP address used for the terminals on LAN 104 during the IKE communication. The distribution procedure realizes the VPN communication in which a terminal outside the LAN is allowed to be accessible into the LAN 104 environment, which is configured with private IP addresses. Thus, outside PC 101 can access to the LAN 104 environment configured with private IP addresses, ensuring security. Fourth Preferred Embodiment Now will be explained the security gateway apparatus employing the method described above of the embodiment, referring to FIG. 4. Gateway apparatus 203 includes DHCP option adding section 212, IPsec communication section 214, IP address distribution section 216, I/O section 210 for WAN, and I/O section 218 for LAN. As described in the method in the first preferred embodiment,
Thus, according to the VPN communication method and the security gateway apparatus using the method, when establishing the IPsec communication with an outside PC having a dialup connection, the gateway apparatus can control the final destination IP address of the PC, therefore eliminating need for setting of the terminal on the LAN. This fact promises safeguarded communication. Besides, with the method and the apparatus, the outside PC establishing VPN is virtually regarded as another terminal on the LAN. This allows the outside PC to access to any terminal on the LAN with safety. Furthermore, the present invention makes possible that the outside PC accesses to a LAN environment that is configured with private IP addresses, with no degradation of security.
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