JP2006005425A - Reception method of encrypted packet and reception processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide reply prevention processing for preventing IPsec packets from being abrogated even when the receiving sequence is replaced depending on the priority set to the IPsec packets in the replay prevention process of the IPsec packets. <P>SOLUTION: A reception processing section 130 obtains the priority of the packets among the received packets on the basis of information protected by the IPsec, uses replay prevention windows 141, 142 adapted to the packet priority to carry out the reply prevention process of the packets so as to be capable of carrying out the reply prevention process for preventing packets from being abrogated even when the reception sequence is replaced due to the priority. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving method when receiving an encrypted packet.

  In recent years, with the widespread use of personal computers and the Internet, it has become possible to provide information and collect information easily and inexpensively through websites published on the Internet. Also, exchange of e-mails via the Internet and intranets between companies, video / audio distribution, electronic commerce and electronic payments are becoming common. When using such a service, security that is equivalent to that of a dedicated line is required for communication including particularly important information and communication of information related to personal privacy.

  One example of a technique for ensuring security as described above is IPsec. IPsec is a security protocol that performs encryption and authentication at the network layer (OSI reference model layer 3), and is standardized by the Internet Engineering Task Force (IETF) (RFCs 2401 to 2412, 2451).

  By connecting to the Internet via a network connection device such as a computer or router equipped with the IPsec function, a virtual private network (VPN) can be constructed on a wide area network such as the Internet. That is, the user can safely use the Internet without performing special processing such as encryption.

  When performing communication using IPsec, the encryption function and authentication algorithm used, the encryption key and authentication key used, etc. are pre-installed on the sender and receiver IPsec functions. Must match between connected computers and network connected devices. This encryption, authentication algorithm, etc. are called security parameters. From the encryption algorithm, encryption key, authentication algorithm, authentication key, SPI value (Security Parameter Index), protocol (ESP or AH), mode (transport, tunnel), etc. Composed. In order to match the security parameter values, applications called IKE (Internet Key Exchange) communicate with each other. As a result of the mutual communication, the security parameter value matched between the transmission side and the reception side is held by a framework called SA (Security Association) and is notified to the IPsec processing unit. In addition, instead of performing mutual communication using IKE, the SA that has been consistently matched manually by any method, for example, the transmission side and the reception side notify the security parameters using a telephone or the like is manually used. You may set to each IPsec process part.

  A functional unit that performs IPsec processing converts an IP packet to be transmitted into an IPsec packet based on an encryption algorithm, an authentication algorithm, an encryption key, an authentication key, and the like defined in SA, or converts a received IPsec packet into an IP packet. It communicates by restoring.

  IPsec also includes a mechanism for defending against replay attacks. The replay attack is an attack in which an exchanged IP packet is taken on a communication path and a copy thereof is transmitted on the communication path. Since the exchanged IP packet is an IP packet that should be normally received, the processing load on the receiving terminal can be increased by a replay attack. To prevent this replay attack, IPsec performs the following replay prevention process. First, in an apparatus that transmits an IPsec packet, a sequence number determined for each security parameter is given in the IPsec header. The apparatus that receives the IPsec packet confirms that the sequence number included in the received IPsec packet is not duplicated with that previously received. If the sequence numbers are duplicated, it is determined that the packet is due to a replay attack, and the packet is discarded. Here, in order to check the duplication of sequence numbers, storing the sequence numbers of all IPsec packets received so far requires a very large storage capacity, which is not practical. Therefore, in IPsec, the presence / absence of reception of a packet having a sequence number within a certain number from the maximum sequence number among the received packets is stored as a replay prevention window.

  Now, an example of a reception processing apparatus that performs replay prevention processing on the received IPsec packet will be described with reference to FIGS.

  First, the network configuration will be described with reference to FIG. In FIG. 9, 600 is a conventional reception processing device, 200 is a relay device, 700 is a counter encryption communication device, and 800 is an attack terminal that performs a replay attack. The encryption communication device 700 transmits an IPsec packet to the conventional reception processing device 600, and the conventional reception processing device 600 receives the packet and performs IPsec reception processing including replay prevention processing. Here, the encryption communication device 700 transmits IPsec packets in the order of P1 and P2. The sequence numbers P1 and P2 are 101 and 103 in order. In addition, the attack terminal 800 transmits P3 (sequence number 101, which is the same as P1), which is a replay attack of P1, to the conventional reception processing device 600. As a result, the conventional reception processing apparatus 600 receives packets in the order of P1, P2, and P3.

  Next, an example of the configuration of a conventional reception processing apparatus 600 will be described with reference to FIG. In FIG. 10, 610 is a network I / F for receiving a packet, 620 is a reception queue, 630 is a reception processing unit for receiving a received packet, and 640 is a replay prevention window corresponding to the received packet. In order to simplify the above, the window size is set to 3. Reference numeral 650 denotes a SADB (Security Association Database) that stores security parameters of received packets. Here, when the conventional reception processing device 600 receives the IPsec packet, the reception processing unit 630 receives the IPsec packet via the network I / F 610 and the reception queue 620, and uses the SPI value from the AH header or ESP header included in the packet. And the SADB 650 is searched using this as a search key. As a result of the search, a replay prevention window 640 corresponding to the SPI value is obtained together with an encryption algorithm corresponding to the SPI value, and security parameters such as an encryption key, an authentication algorithm, and an authentication key. Next, decryption processing and authentication processing of the IPsec packet are performed using the security parameter, and reception processing for restoring to a normal IP packet is performed. The replay prevention process performed during the reception process will be described with reference to FIG.

  FIG. 11 shows the state of the replay prevention window 640. In FIG. 11, 1 indicates that it has been received, and 0 indicates that it has not been received. FIG. 11A shows a state before receiving packets P1 to P3, indicating that IPsec packets with sequence numbers 100 and 102 have been received, and that IPsec packets with sequence number 101 have not been received. Yes.

  When the replay prevention window 640 in FIG. 11A receives an IPsec packet with a sequence number of 99 or less, the packet is discarded because it is out of the management of the replay prevention window 640. When a packet that has already been received in the replay prevention window 640 (sequence numbers 100 and 102 in the figure) is received, the packet is determined to be a replay attack and discarded.

  Here, when the packet P1 (sequence number 101) is received first, since the sequence number is managed by the replay prevention window 640 and not received, the packet is normally received and the replay prevention window 640 is received. Is updated as shown in FIG.

  Next, when the packet P2 (sequence number 103) is received, the sequence number is larger than the maximum sequence number 100 managed in the replay prevention window 640, so the window is slid and updated as shown in FIG. And received normally.

  Finally, when the packet P3 (sequence number 101), which is a replay attack of the packet P1, is received, the sequence number is managed by the replay prevention window 640, but since the packet has already been received, the packet is discarded. When the packet is discarded, the state of the replay prevention window 640 does not change and remains as shown in FIG.

As described above, when the replacement of packets is limited, an effective replay prevention process can be performed by using the replay prevention window.
Standard specification "RFC2401", IETF, [March 8, 2004 search], Internet <URL: http://www.ietf.org/rfc/2401.txt> Standard specification “RFC2402”, IETF, [Search March 8, 2004], Internet <URL: http://www.ietf.org/rfc/2402.txt> Standard specification "RFC2406", IETF, [March 8, 2004 search], Internet <URL: http://www.ietf.org/rfc/2406.txt> Standard specification “RFC2475”, IETF, [March 8, 2004 search], Internet <URL: http://www.ietf.org/rfc/2475.txt>

  By the way, since an IPsec packet is a kind of IP packet, when priority information is set in an IP header included in the IPsec packet, the IPsec packet is a router device on a communication path like a normal IP packet. Based on the priority information, the priority control of the transfer process is performed. An example of a technique for performing such priority control is DiffServ defined in RFC2475. In DiffServ, the value set in the TOS field in the IP header is used as priority information, and the transfer order of packets to be transferred is controlled based on the TOS field value. Therefore, the relay device corresponding to DiffServ forwards a packet in which a high priority value is set in the TOS field among a plurality of packets to be transferred in preference to a packet in which a low priority value is set. . As a result, the order in which the device that transmits the IPsec packet transmits and the order in which the device that receives the IPsec packet receives change according to the priority information in the IPsec packet. However, in the conventional configuration, since there is only one replay prevention window per SA, when the reception order is changed based on the priority information in the IP header, it is not a packet due to the replay attack. In some cases, the replay prevention process discards the packet. This problem will be described below.

  In FIG. 9, it is assumed that the encryption communication device 700 transmits IPsec packets in the order of P11, P12, P13, and P14 to the conventional reception processing device 600. The sequence numbers of P11 to P14 are 100, 101, 102, and 103, respectively, and the priorities are 2, 1, 1, and 1, respectively. Priority 1 indicates that the priority is high, and priority 2 indicates that the priority is low. In this case, since the priority of the packet P1 is low, transfer is delayed in the relay device 200, and the conventional reception processing device 600 receives the packets in the order of P12, P13, P14, and P11. As a result, the replay prevention window 640 after receiving the packet P14 becomes equal to FIG. Thereafter, when P11 (sequence number 100) is received, the sequence number is not managed by the replay prevention window 640, and thus P11 is discarded even though it is not a packet due to a replay attack.

  As described above, in the conventional reception processing device, when the packet reception order is changed depending on the transfer processing priority set in the packet, the packet is discarded even though it is not a packet due to the replay attack. was there. The present invention solves the above-described conventional problems, and provides an encryption communication device provided with a replay prevention process for preventing packet discard even when the arrival order of IPsec packets is switched by priority control of transfer processing. Objective.

  In order to solve the conventional problem, a reception processing method according to claim 1 of the present invention includes an authentication step for confirming that a protection area included in a received packet has not been rewritten, and a priority of the received packet. A priority specifying step specified from the priority specifying information, a window selecting step for selecting a replay prevention window corresponding to the priority of the received packet from a plurality of replay prevention windows, and a received packet replayed using the selected replay prevention window. It includes a replay prevention processing step that determines whether or not the attack is an attack and discards the packet if it is a replay attack.

  According to the first aspect of the present invention, even if the reception order is changed depending on the priority of the transfer process included in the received packet, it is possible to perform the replay prevention process for preventing packet discard.

  In addition, the priority specifying step in the reception processing method according to claim 2 of the present invention includes a block including priority specifying information even if a part or all of the protection area in the received packet is encrypted by block cipher. The priority specifying information of the received packet is obtained by decoding only the block including information necessary for specifying the block including the priority specifying information.

  According to the second aspect of the present invention, even if the priority specifying information is encrypted by the block cipher, it is possible to perform the replay prevention process of the received packet without decrypting all the blocks.

  Also, the reception processing method according to claim 3 of the present invention uses either or both of information in the third layer header and information in the fourth layer header as priority specifying information of the received packet.

  According to claim 3 of the present invention, it is possible to perform the replay prevention process corresponding to the priority by using the information included in the third layer header and the information included in the fourth layer header.

  In the reception processing method according to claim 4 of the present invention, when a packet obtained by encapsulating the first packet composed of the first header and the first data by the second header is received, Including a step of specifying the priority of the packet from the priority information included in the header of 1.

  According to claim 4 of the present invention, it is possible to perform the replay prevention process corresponding to the priority by using the priority information included in the header of the encapsulated packet.

  In the reception processing method according to claim 5 of the present invention, a replay prevention window having a larger window size is used as the priority is higher.

  According to the fifth aspect of the present invention, it is possible to prevent a packet having a high priority from being erroneously discarded even if the packet is delayed due to a router in the middle of the route.

  The reception processing method according to claim 6 of the present invention uses a replay prevention window having a smaller window size as the priority is higher.

  According to the sixth aspect of the present invention, it is possible to reduce the processing load by discarding a packet with a high priority which is greatly delayed despite a packet requiring real-time property.

  The reception processing method according to claim 7 of the present invention includes a step of reducing the window size of the replay prevention window having a low priority when the usage amount of the resource used for the calculation exceeds a certain threshold.

  According to the seventh aspect of the present invention, when the usage amount of the computing resource increases, it becomes possible to reduce the resource usage amount by facilitating discarding the low priority packet.

  In addition, the reception processing method according to claim 8 of the present invention includes a step of returning the window size of the replay prevention window once reduced to the original size when the amount of the resource used for the calculation is equal to or less than a certain threshold value. .

  According to claim 8 of the present invention, it is possible to suppress packet discard when the amount of computing resources used decreases.

  In the reception processing method according to claim 9 of the present invention, the window size of the replay prevention window is reduced when the CPU load for reception processing is equal to or less than a certain threshold value, and the window size is reduced when it is equal to or greater than the certain threshold value. Including the step of restoring.

  According to the ninth aspect of the present invention, the CPU load is reduced by facilitating the discarding of low priority packets when the CPU load increases, and the low priority packets are not discarded when the CPU load decreases. Thus, the replay prevention process can be performed.

  The reception processing method according to claim 10 of the present invention reduces the window size of the replay prevention window when the number of packets queued in the reception queue is equal to or smaller than the first threshold, and is equal to or larger than the second threshold. The step of restoring the window size reduced to the original size is included.

  According to the tenth aspect of the present invention, when the number of packets queued in the reception queue increases, the processing load is reduced by facilitating discarding of low priority packets, and the number of packets decreases. It is possible to perform replay prevention processing so as not to discard low priority packets.

  The reception processing method according to claim 11 of the present invention reduces the window size of the replay prevention window when the amount of working memory used for the reception processing is equal to or smaller than the first threshold, and when equal to or larger than the second threshold. Including restoring the reduced window size.

  According to the eleventh aspect of the present invention, when the amount of work memory used for reception processing increases, the processing load is reduced by facilitating discarding of low priority packets, and the amount of work memory decreases. In this case, it is possible to perform replay prevention processing so as not to discard low priority packets.

  The reception processing method according to claim 12 of the present invention performs replay prevention processing when receiving a packet protected by IPsec.

  According to the twelfth aspect of the present invention, it is possible to correctly perform the replay prevention process even for the IPsec packet whose reception order is changed depending on the priority included in the received packet.

  The reception processing apparatus according to claim 13 of the present invention includes a security database that stores security parameters, a priority determination database that holds correspondence between priority information included in received packets and priority of the packets, A reception processing unit that performs packet reception processing, and the reception processing unit searches the priority determination database using authentication means for confirming that the protection area of the packet has not been rewritten, and priority specifying information as a key. Priority specifying means for specifying the priority of the packet, window selecting means for selecting a replay prevention window corresponding to the priority specified by the priority specifying means from the replay prevention windows corresponding to each priority, and window selection means Using the replay prevention window selected in step 1, the packet is Whether the determined includes replay prevention means discards the packet if the packet according to replay attacks.

  According to the thirteenth aspect of the present invention, it is possible to realize a reception processing device capable of preventing erroneous packet discard even if the reception order varies depending on the priority included in the received packet.

  Further, the priority specifying means of the reception processing device according to claim 14 of the present invention comprises a block including priority specifying information for a received packet in which a part or all of the protected area is encrypted by block cipher, The priority specifying information is obtained by decoding only the block including the information for specifying the block including the specifying information.

  According to the fourteenth aspect of the present invention, it is possible to realize a reception processing device capable of performing replay prevention processing of a received packet without decrypting all the received packets even when the priority specifying information is encrypted.

  In addition, the reception processing device according to claim 15 of the present invention specifies the priority of the received packet from one or both of the information in the third layer header and the information in the fourth layer header included in the received packet. .

  According to the fifteenth aspect of the present invention, it is possible to perform the replay prevention process corresponding to the priority using the information included in the third layer header and the information included in the fourth layer header.

  The reception processing apparatus according to claim 16 of the present invention encapsulates a first packet composed of a first header and second data by a second header that is a header belonging to the same layer as the first header. When the received packet is received, the priority of the packet is specified from the priority information included in the first header of the received packet.

  According to the sixteenth aspect of the present invention, it is possible to realize a reception processing device that specifies the priority of the received packet from the priority information included in the header of the encapsulated packet.

  A reception processing device according to claim 17 of the present invention includes a reception processing unit that performs a replay prevention process using a replay prevention window having a higher window size as the priority is higher.

  According to the seventeenth aspect of the present invention, it is possible to realize a reception processing apparatus that can prevent a packet with a high priority from being erroneously discarded even if a packet is delayed due to a router on the way.

  The reception processing apparatus according to claim 18 of the present invention further includes a reception processing unit that performs replay prevention processing using a replay prevention window having a smaller window size as the priority is higher.

  According to the eighteenth aspect of the present invention, a reception processing device capable of reducing the processing load by discarding a high-priority packet that is greatly delayed despite a packet requiring strict real-time performance is realized. it can.

  In addition, the reception processing device according to claim 19 of the present invention provides a resource monitoring unit that notifies when the amount of resources used for calculation exceeds a certain threshold, and prevents replay with low priority when receiving this notification. A reception processing unit for reducing the window size of the window is provided.

  According to the nineteenth aspect of the present invention, it is possible to realize a reception processing device that can easily discard a low-priority packet and reduce the resource usage when the usage amount of computing resources increases. .

  In addition, the reception processing device according to claim 20 of the present invention includes a resource monitoring unit that notifies when the usage amount of the resource used for the calculation is below a certain threshold, and the priority that has been reduced once receiving this notification. A reception processing unit that returns the window size of the low replay prevention window to the original size is provided.

  According to the twentieth aspect of the present invention, it is possible to realize a reception processing device capable of suppressing the discard of packets with low priority when the amount of computing resources used is reduced.

  Further, the reception processing device according to claim 21 of the present invention provides a resource monitoring unit that notifies when the value of the CPU load for receiving processing exceeds or falls below a certain threshold value, and receives this notification, and receives the priority. A reception processing unit that reduces or restores the window size of the low replay prevention window to the original size.

  According to the twenty-first aspect of the present invention, the CPU load is lowered by facilitating the discarding of the low priority packet when the CPU load is large, and the low priority packet is not easily discarded when the CPU load is small. It is possible to realize a reception processing device.

  The reception processing apparatus according to claim 22 of the present invention also includes a reception queue for queuing received packets until reception processing is started, and when the length of the reception queue exceeds or falls below a certain threshold. A resource monitoring unit for notification and a reception processing unit for reducing the window size of the replay prevention window having a low priority or returning the window size to the original size when the notification is received.

  According to the twenty-second aspect of the present invention, when the number of packets queued in the reception queue is large, the processing load is reduced by facilitating the discarding of the low priority packets, and when the number of packets decreases. It is possible to realize a reception processing device that makes it difficult to discard priority packets.

  Further, the reception processing device according to claim 23 of the present invention provides a resource monitoring unit that notifies when the amount of work memory required for the reception processing exceeds or falls below a matching threshold, and receives this notification, and receives the priority. A reception processing unit that reduces or restores the window size of the low replay prevention window to the original size.

  According to the twenty-third aspect of the present invention, when the working memory amount required for the reception process increases, the processing load is reduced by facilitating the discarding of the low priority packet, and when the working memory amount decreases, the low priority is given. It is possible to realize a reception processing device that makes it difficult to discard a certain number of packets.

  According to a twenty-fourth aspect of the present invention, the reception processing apparatus includes a reception processing unit that performs reception processing of a packet protected by IPsec.

  According to the twenty-fourth aspect of the present invention, it is possible to realize a reception processing device capable of correctly performing a replay prevention process even for an IPsec packet whose reception order is switched depending on the priority included in the reception packet.

  As described above, according to the reception processing method of the present invention, even if the reception order varies depending on the priority included in the packet, the influence due to the variation in the reception order can be removed, and the discard of the low priority packet is prevented. It becomes possible.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a network configuration including a reception processing apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 100 denotes a reception processing apparatus according to the present embodiment, which has an IP address of 132.182.1.10. Reference numeral 200 denotes a network relay device such as a router. Reference numeral 400 denotes a first server device that transmits packets such as video and audio information that require real-time processing to the reception processing device 100, and includes an IP address of 132.182.2.30. Reference numeral 500 denotes a second server device that transmits to the reception processing device 100 a packet that does not require real-time processing, such as an e-mail, and has an IP address of 132.182.3.11. Reference numeral 300 denotes a security gateway that temporarily receives a packet transmitted to the reception processing device 100 by the first server device and the second server device, encrypts the packet, and transmits the encrypted packet to the reception processing device 100. The security gateway 300 has an IP address of 132.182.3.1 for packet transmission / reception with the first server device 400 and the second server device 500, and for packet transmission / reception with the reception processing device 100. It has an IP address of 132.182.2.10.

  The first server device 400 transmits the video data to the reception processing device 100 as an IP packet in which the fourth layer protocol is UDP and the destination port number is 2000. Similarly, the second server device 500 transmits e-mail data to the reception processing device 100 as an IP packet having a fourth layer protocol of TCP and a destination port number of 3000.

  Next, packets received by the reception processing device 100 from the first server device 400 and the second server device 500 via the security gateway 300 will be described with reference to FIG. SA is set for communication between the reception processing apparatus 100 and the security gateway 300, and encrypted communication by IPsec is performed. The SA used for encryption here is: SPI is 1000, encryption algorithm is DES-CBC, encryption key is “abcdefgh”, authentication algorithm is HMAC-MD5, and authentication key is “OPQRSTUVW”. As a result, the IP packet transmitted from the first server device 400 to the reception processing device 100 is transmitted to the reception processing device 100 by the security gateway 300 as an IPsec packet shown in FIG. Hereinafter, this IPsec packet is referred to as a packet H. In FIG. 2A, the packet H is composed of a second IP header, ESP header, IV, first IP header, fourth layer protocol header, payload, ESP trailer, and ICV. The first IP header, the fourth layer protocol header, and the payload are packets transmitted by the first server device 400. The security gateway 300 adds a second IP header to encapsulate the packet, and adds an ESP header, ESP trailer, and ICV to protect the entire original IP packet with IPsec. As a result, the value from the ESP header to the ESP trailer is protected from value rewriting by the authentication algorithm (HMAC-MD5), and the range from the first IP header to the ESP trailer is encrypted by the encryption algorithm (DES-CBC). The second IP header has a source IP address of 132.182.10 and a destination IP address of 132.182.1.10. The TOS field value of the first IP header, which will be described later, depends on the IPsec specification. 1 which is the same value as the TOS field value is set. The ESP header is composed of a sequence number and an SPI. The SPI is 1000, and the sequence numbers are assigned consecutive numbers in the order of transmission. IV stores a random number used for encryption. The first IP header has a source IP address of 132.182.3.10, a destination IP address of 132.182.1.10, and a TOS field of 1. The fourth layer protocol header is a UDP header, and 2000 is stored in the destination port number. Video data is stored in the payload. The ESP trailer includes a next header indicating the protocol type of the fourth layer protocol, and stores UDP here. The ICV stores a hash value obtained by calculating data in the authentication range using an authentication key (“OPQRSTUVW” in the present embodiment) according to an authentication algorithm.

  Similarly, the IP packet transmitted from the second server device 500 to the reception processing device 100 is transmitted to the reception processing device 100 by the security gateway 300 as an IPsec packet shown in FIG. Hereinafter, this IPsec packet is referred to as a packet L. In FIG. 2B, the part corresponding to the packet transmitted by the second server device 500, the encrypted area, and the area protected by authentication are the same as the packet H, and the second IP of the packet L The source IP address of the header is 132.182.10, the destination IP address is 132.182.10, and the TOS field is 2. The first IP header has a source IP address of 132.182.3.11, a destination IP address of 132.182.1.10, and a TOS field of 2. The fourth layer protocol header is a TCP header, and the destination port number is 3000. Data that does not require real-time processing such as e-mail is stored in the payload, and TCP is stored in the next header of the ESP trailer. The contents of the ESP header, IV, and ICV other than the above are the same as those of the packet H.

  As described above, the IPsec packet transmitted from the security gateway 300 has the following differences between the packet H and the packet L. That is, in the TOS field value in the first IP header, packet H is 1 while packet L is 2. Further, the source IP address in the second IP header is that the packet H is 132.182.10 while the packet L is 132.182.3.11. Further, the TOS field value in the second IP header is 2 for the packet L while the packet H is 1. The fourth layer protocol header is a UDP header in which the packet H is the destination port number 2000 and the packet L is a TCP header in which the destination port number is 3000. The value of the next header in the ESP trailer is that the packet H is UDP while the packet L is TCP.

  Next, the configuration of the reception processing apparatus 100 is shown in FIG. In FIG. 3, 110 is a network I / F, 120 is a reception queue for queuing received IPsec packets, 130 is a reception processing unit for receiving received IPsec packets, and 140 is applied to received IPsec packets. This is a replay prevention window corresponding to SA, and is composed of 141 to 142 according to the priority of the received packet. Reference numeral 150 denotes an SADB that is a database for storing SA, and reference numeral 160 denotes a priority determination DB that is a database for determining the priority of received IPsec packets.

  Here, the configuration of SADB 150 is shown in FIG. The SADB 150 includes an SPI value, an encryption algorithm, an encryption key, an authentication algorithm, an authentication key, and a replay prevention window state as components. In FIG. 4, one SA is registered, the SPI value is 1000, the encryption algorithm is DES-CBC, the encryption key is “abcdefgh”, the authentication algorithm is HMAC-MD5, and the authentication key is “OPQRSTUVW”. The replay prevention windows corresponding to priority 1 and priority 2 are registered, and the windows of priority 1 have been received for packets having a window size of 3 and sequence numbers 94, 95, and 96. A window of 2 indicates that a packet having a window size of 3 and sequence numbers of 97, 98, and 99 has been received.

  The configuration of the priority determination DB 160 is shown in FIG. In FIG. 5, the priority determination DB 160 includes items of the protocol type of the fourth layer protocol, the transmission source port number, the destination port number, and the priority, and at least two entries are registered. In the first entry, the protocol type is UDP, the source port number is “*” (this is a symbol indicating all source port numbers), the destination port number is 2000, the priority is 1, and 2 In the first entry, the protocol type is TCP, the source port number is “*”, the destination port number is 3000, and the priority is 2.

  Next, the operation of the reception processing apparatus 100 during reception processing will be described. In FIG. 1, the security gateway 300 protects the packet received from the second server device 500 and the packet 400 received from the first server device 400 with IPsec, and tunnel mode IPsec packets P <b> 1 to P <b> 1 addressed to the reception processing device 100. Send P4. Here, the packet P4 is an IPsec packet generated from the second server device 500. The SPI value is 1000, the priority is 2, and the sequence number is 100. Packets P1 to P3 are IPsec packets generated from the first server device 400. The SPI value is 1000, the priority is 1, and the sequence numbers are 101, 102, and 103 in order. The security gateway 300 transmits packets to the reception processing apparatus 100 in the order of P4, P1, P2, and P3.

  Next, the relay device 200 that has received the packets P1 to P4 refers to the priority information included in the packet, and transfers the packet to the reception processing device 100 in the order of packet priority. That is, the relay apparatus 200 transmits packets to the reception processing apparatus 100 in the order of P1, P2, P3, and P4. As a result, the reception processing apparatus 100 receives the IPsec packets transmitted in the order of P4, P1, P2, and P3 by the security gateway 300 in the order of P1, P2, P3, and P4. Now, the reception operation when the reception processing apparatus 100 receives P1 to P4 will be described with reference to FIGS.

(initial state)
First, in the initial state, it is assumed that the reception processing apparatus 100 has received three IPsec packets H with sequence numbers 94, 95, and 96 and three IPsec packets L with 97, 98, and 99. Therefore, the replay prevention windows 141 and 142 are in the state shown in FIG. That is, the replay prevention window 141 corresponding to the priority 1 is registered with the sequence numbers 94, 95, and 96 received, and the replay prevention window 142 corresponding to the priority 2 is registered with the sequence numbers 97, 98, and 99 already received. .

(Reception of packet P1)
When the packet P1 is received, the reception process of the packet is performed according to the flowchart shown in FIG.

<Step 1>
In step 1, the received packet is authenticated. When the packet is received by the network I / F 110, the reception processing unit 130 receives the packet via the reception queue 120. Next, the reception processing unit 130 extracts the SPI value from the packet, and searches the SADB using the SPI value as a search key. As a result of the search, the state of the encryption algorithm, encryption key, authentication algorithm, authentication key, and replay prevention window corresponding to the SPI value is obtained. In this embodiment, since the SPI value of the packet P1 is 1000, as a result of searching the SADB, “DES-CBC”, “abcdefgh”, “HMAC-MD5”, “OPQRSTUVW”, “94 for priority 1” are used. -96 have been received, and priority 2 for 97-99 has been received.

<Step 2>
In step 2, the hash value of the received packet is calculated using the authentication algorithm and authentication key obtained in step 1, and it is confirmed that the hash value matches the ICV. If it matches the ICV, it can be confirmed that the area protected by the authentication algorithm in the packet has not been rewritten by a third party. If the hash value does not match the ICV, the packet is discarded because there is a possibility that the region of the packet has been rewritten by a third party.

  In the present embodiment, it is determined that the hash value and the ICV match for the packet P1, and there has been no rewriting by a third party.

<Step 3>
In step 3, the priority of the received packet is specified. First, the IHL and protocol values in the second IP header are obtained using the encryption algorithm and encryption key obtained by the SADB search in step 1. That is, the first block and the second block are decoded to obtain the IHL and protocol values. Next, the second IP header length is specified from the IHL value, and the source port number and destination port number values in the fourth layer protocol header are obtained. In this embodiment, IHL is 5 (a value indicating 20 bytes), and the third and fourth blocks are decoded to obtain both port numbers. From the above, the type of the fourth layer protocol, the source port number, and the destination port number are obtained. Further, the priority determination DB 160 is searched using these values as keys, and the priority of the packet is specified.

  In the case of the packet P1, since the encryption algorithm is DES-CBC, the size of one block is 8 bytes. Therefore, UDP, 1000, and 2000 are obtained by decoding the first, second, third, and fourth blocks. Further, as a result of searching the priority determination DB 160 using such information as a key, 1 is obtained as the priority of the packet.

  If the packet is not encrypted, the decryption process itself is skipped, and the values of the type of the fourth layer protocol, the source port number, and the destination port number included in the packet are directly referred to.

<Step 4>
In Step 4, the replay prevention process is performed using the replay prevention window corresponding to the priority obtained in Step 3 among the plurality of replay prevention windows obtained in Step 1. The replay prevention process is the same as the process in the conventional reception processing apparatus.

  In the case of the packet P1, the replay prevention process is performed using the replay prevention window 141 corresponding to the priority 1. As a result of the replay prevention process, the packet is normally accepted, and the replay prevention window 141 is updated to the state shown in FIG.

<Step 5>
If the received packet is not discarded in step 4, the reception processing unit 130 performs the remaining reception processing. That is, the first IP header, ESP header, IV, ESP trailer, and ICV are removed after decoding the remaining blocks that have not been decoded using the SA searched in step 1. In this way, the IP packet before being converted into the IPsec packet, which is composed of the second IP header, the fourth layer protocol header, and the payload, is restored. The reception processing unit 130 performs reception processing for the restored IP packet.

  If the packet is not encrypted, the remaining blocks need not be decrypted.

  The above is the reception processing operation of the reception processing unit 130 when the packet P1 is received. As a result, the packet P1 is normally received, and the replay prevention window 141 corresponding to the priority 1 is registered as having received the sequence number 101 as shown in FIG. 7B.

(After receiving IPsec packet P2)
When receiving the IPsec packet P2 (priority 1, sequence number 102), the reception processing unit 130 performs the reception process according to the flowchart shown in FIG. 6 as in the case of the packet P1. As a result, the packet P2 is also received normally, and the replay prevention window 141 corresponding to the priority 1 of the packet P2 is registered as having received the sequence numbers 102 and 101 as shown in FIG. 7C.

(After receiving IPsec packet P3)
The same applies when an IPsec packet P3 (priority 1, sequence number 103) is received. As a result, the packet P3 is normally received, and the replay prevention window 141 corresponding to the priority 1 of the packet P1 is registered with the sequence numbers 103, 102, and 101 received as shown in FIG. .

(After receiving IPsec packet P4)
Similarly, when the IPsec packet P4 (priority 2, sequence number 100) is received, the reception processing unit 130 performs reception processing according to the flowchart shown in FIG. Since the packet P4 is determined to have the priority 2 in Step 3, the reception processing unit 130 executes the replay prevention process in Step 4 using the replay prevention window 142 corresponding to the priority 2.

  In this case, the conventional technique uses a single replay prevention window regardless of the priority of the packet. Therefore, the packet P4 is discarded in order to perform the replay prevention process using the replay prevention window 141 used when receiving the packets P1 to P3. This is because the sequence number of the packet P4 is 100, which is older than the sequence numbers 101 to 103 managed by the replay prevention window 141.

  On the other hand, in the present invention, the replay prevention window 142 corresponding to the priority 2 is used in the replay prevention process of the packet P4. As a result, the packet P4 is normally accepted. This is because the sequence number 100 of the packet P4 is newer than the sequence numbers 97 to 99 managed by the replay prevention window 142. As a result of the above reception process, the packet P4 is normally received, and the replay prevention window 142 is registered with the sequence numbers 100, 99, and 98 already received as shown in FIG.

  As described above, by performing the replay prevention processing of the packet using the replay prevention window corresponding to the priority of the received packet, even when the reception order is changed depending on the priority included in the received packet, the packet is It can be received normally without being discarded.

  In this embodiment, the priority of the received packet is obtained from the protocol type and the port number of the fourth layer. However, the priority may be obtained from the source address and the destination address included in the second header. It may be obtained from the protocol type and port number of the layer and the source address and destination address included in the second IP header. Alternatively, it may be obtained from priority information included in the second IP header (corresponding to the TOS field in the case of an IPv4 header). Further, when the second IP header is an IPv6 header, the DS field may be used as priority information. Furthermore, the priority of the packet may be obtained based on any information included in the first IP header, the second IP header, and the fourth layer protocol header. For example, the priority is obtained from the source IP address and destination IP address included in the second IP header in addition to the protocol type, source port number, and destination port number of the fourth layer protocol described in this embodiment. It doesn't matter.

  In this embodiment, the packet in the IPsec tunnel mode is used as a secure packet. However, a packet in the transport mode may be used. Since the second IP header does not exist in the transport mode, the priority of the packet may be obtained from information other than the information included in the IP header.

  In this embodiment, the received packet is encrypted and authenticated by ESP, but the packet may not be encrypted. When the data is not encrypted, all the decryption processes described in this embodiment are not necessary. The packet may be protected by AH instead of ESP. Since encryption is not performed in AH, all the decryption processing described in the present embodiment is not necessary.

  Further, in the present embodiment, the packet priority has been described as two levels, but it may be three or more levels.

  In the present embodiment, the window size of the replay prevention window has been described as 3, but the present invention does not limit the window size.

  In the present embodiment, the case where the packet is protected by IPsec has been described. However, the present invention includes information for specifying the priority of the packet and a sequence number for distinguishing the packet, and both are authenticated. It can be applied to all packets protected by, and the technology for protection is not limited to IPsec.

(Embodiment 2)
Next, another embodiment of the present invention will be described below. Since the network configuration is the same as that of the first embodiment, description thereof is omitted.

  The configuration of reception processing apparatus 100 in the present embodiment is different from that of Embodiment 1 in the following points. The window size of the replay window 141 corresponding to the priority 1 in the second embodiment is 5, which is larger than the window size 3 of the replay window 142 corresponding to the priority 2.

  The reception processing of the reception processing device 100 when the security gateway 300 transmits packets P11 to P15 having the priority 1 and the sequence numbers of 111, 112, 113, 114, and 115 in order to the reception processing device 100. The operation will be described.

  In the present embodiment, it is assumed that, in the middle of the communication path, the transfer order is switched between packets P11 to P15 having the same priority, and arrives at reception processing apparatus 100 in the order of P12, P13, P14, P15, and P11. In this case, the sequence numbers are 112, 113, 114, 115, and 111 in the order of reception. In the present embodiment, since the window size of the replay window 141 corresponding to the priority 1 is 5, it is possible to correctly receive even when the sequence numbers of five are changed as described above. In this way, by setting the window size of the replay window for a packet with high priority, a reception processing device that makes it difficult to discard packets with high priority can be realized.

  In this embodiment, the window size of the replay prevention window 141 corresponding to the priority 1 is larger than the window size of the replay prevention window 142. However, the window size of the replay prevention window 142 corresponding to the priority 2 is larger. It does not matter if it is large. In many cases, packets including voice information have an acceptable delay time and a high priority. Therefore, it is possible to reduce the load on the reception processing apparatus by discarding such a packet that has been greatly delayed at the stage of the replay prevention process.

  Further, in the priority determination DB 160, in addition to the packet priority, a real-time index that is an index indicating the real-time property of the packet may be held, and the window size of each replay prevention window may be set according to the real-time index. In addition, the window size of each replay prevention window may be determined by a specific calculation formula using the packet priority, the packet real-time index, and the basic window size as inputs. As an example of this specific calculation formula, “window size = basic window size × priority / real-time index” can be cited. The specific calculation formula is not limited to the example shown here, and may be arbitrarily determined.

(Embodiment 3)
Next, another embodiment of the present invention will be described below. The network configuration is the same as in the first embodiment.

  The configuration of reception processing apparatus 100 in the present embodiment is shown in FIG. In FIG. 8, the reception processing apparatus 100 includes a reception queue length monitoring unit 170 in addition to the configuration of the first embodiment. The reception queue length monitoring unit 170 measures the number of reception packets queued in the reception queue 120. The reception queue length monitoring unit 170 includes a first threshold value and a second threshold value. In the present embodiment, the first threshold is 2, the second threshold is 3, and the reception queue length monitoring unit 170 receives the packet when the number of packets queued in the reception queue exceeds the first threshold. This is notified to the processing unit. Receiving this, the reception processing unit 130 reduces the window size of the window 142 corresponding to the priority 2 to 1. Similarly, when the number of packets falls below the second threshold, the reception queue length monitoring unit 170 notifies the reception processing unit of this. Receiving this, the reception processing unit 130 returns the window size of the window 142 corresponding to the priority 2 to 3 which is the original size. In the present embodiment, the first threshold is 3 and the second threshold is 2.

  Here, the reception processing apparatus 100 receives IPsec packets P21 to P22 having priority 1 and sequence numbers 211 and 212 in order, and IPsec packets P25, P24, and P23 having priority 2 and sequence numbers 215, 214, and 213 in order. The operation will be described for the case of receiving at once.

  When the packets P21 to P25 shown above are received at a time, the queue length of the reception queue becomes 5, which exceeds the first threshold value 3. Therefore, the reception queue length monitoring unit 170 notifies the reception processing unit 130 that the number of received packets has exceeded the first threshold, and the reception processing unit 130 reduces the window size of the window 142 to 1. The reception processing unit 130 performs reception processing of the packets P21 to P22 while the window size of the replay prevention window 142 is 1. Since all of the packets P21 to P22 have a priority of 1, the reception processing unit 130 performs the replay prevention / replay prevention process using the replay prevention window 141, and completes the reception process correctly.

  At the time when the reception process of the packet P22 is completed, the queue length of the reception queue is 3, and the second threshold value held by the queue length monitoring unit 170 is not less than 2. Therefore, the reception processing unit 130 performs the replay prevention process on the packets P23 to P25 while setting the window size of the replay prevention window 142 to 1.

  Next, reception processing of the packet P25 is performed. Since the sequence number of the packet P25 is 215, the reception processing unit 130 updates the sequence number 215 of the replay prevention window 142 to “Received” and completes the reception processing of the packet. Even at this time, since the queue length of the reception queue is not less than the second threshold, the window size of the replay prevention window 142 remains 1.

  Next, reception processing of the packet P24 is performed. Since the sequence number of the packet P24 is 214, the reception processing unit 130 determines from the window 142 that the packet is a replay attack, and discards the packet P24. At this time, the reception processing unit 130 is notified by the reception queue length monitoring unit 170 that the queue length of the reception queue has fallen below the second threshold, and returns the window size of the replay prevention window 142 to 3.

  Finally, the packet P23 is received. Since the sequence number of the packet P23 is 213, the reception processing unit 130 updates the sequence number 213 of the window 142 to “received” and completes the reception processing of the packet.

  As described above, by reducing the window size of the replay prevention window corresponding to the low priority according to the queue length of the reception queue, when a large number of packets are received at a time, the low priority packets are easily discarded. Thus, the processing load can be reduced. If the queue length is shortened, the processing load is also considered to be reduced. By returning the window size of the replay prevention window corresponding to the low priority to the original value, the low priority packet is discarded. It becomes difficult.

  In this embodiment, the window size of the replay prevention window 142 corresponding to the low priority is changed according to the queue length of the reception queue. However, the calculation of the CPU load of the reception process and the amount of work memory used for the reception process is performed. The window size may be changed depending on the resource usage. Similarly, the window size may be changed depending on the CPU load and work memory usage of the entire reception processing apparatus.

  In the present embodiment, the first threshold value and the second threshold value are different values, but they may be the same value.

  Each of the above-described embodiments is realized by interpreting and executing predetermined program data stored in a storage device (ROM, RAM, hard disk, etc.) that can execute the above-described processing procedure. In this case, the program data may be introduced into the storage device via the recording medium, or may be directly executed from the recording medium. The recording medium refers to a recording medium such as a semiconductor memory such as a ROM, a RAM, or a flash memory, a magnetic disk memory such as a flexible disk or a hard disk, an optical disk such as a CD-ROM, DVD, or BD, or a memory card. The recording medium is a concept including a communication medium such as a telephone line or a conveyance path.

  In addition, each key exchange device or each functional unit of each of the above embodiments can be realized as an LSI that is typically an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

  The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  A reception processing method according to the present invention includes a step of specifying a priority of a packet and a step of performing a replay prevention process using a replay prevention window corresponding to the priority of the identified packet, and is protected by a security protocol. It is useful as a receiving terminal that receives real-time information such as video and audio and non-real-time information such as WEB and control information.

The figure which shows the network structure in Embodiment 1 of this invention. The figure which shows the structure of the received packet in Embodiment 1 of this invention. The figure which shows the structure of the reception processing apparatus 100 in Embodiment 1 of this invention. The figure which shows the structure of SADB150 in Embodiment 1 of this invention. The figure which shows the structure of priority determination DB160 in Embodiment 1 of this invention. Flowchart of reception processing in Embodiment 1 of the present invention The figure which shows the state of the replay prevention window in Embodiment 1 of this invention The figure which shows the structure of the reception processing apparatus 100 in Embodiment 3 of this invention. Diagram showing network configuration in the prior art The figure which shows the structure of the conventional reception processing apparatus 600. The figure which shows the state of the replay prevention window

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Reception processing apparatus 110 Network interface 120 Reception queue 130 Reception processing part 140 Replay prevention window 141 Replay prevention window 142 Replay prevention window 150 SADB (security database)
160 Priority decision DB
DESCRIPTION OF SYMBOLS 200 Relay apparatus 300 Security gateway 400 1st server apparatus 500 2nd server apparatus 600 Conventional reception processing apparatus 610 Network interface 620 Reception queue 630 Reception processing part 640 Replay prevention window 650 Security association database (SADB)
700 Cryptographic Communication Device 800 Replay Attack Device

Claims (24)

A reception processing method for receiving a packet including a protected area protected from value rewriting by a security protocol,
The packet is
A sequence number determined for each set of security parameters used by the security protocol;
In the relay device on the communication path, including a priority indicating the priority when transferring the packet,
The protected area is
The sequence number;
Including priority specifying information for specifying the priority,
The reception processing method is:
An authentication step for confirming that the protected area has not been rewritten;
A priority specifying step of specifying the priority of the packet from the priority specifying information;
A window selection step of selecting a replay prevention window corresponding to the priority of the packet identified in the priority identification step from one or more replay prevention windows provided in correspondence with the priority of the packet;
Using the replay prevention window selected in the window selection step, determining whether or not the packet is a replay attack, and including a replay prevention processing step of discarding the packet if the packet is a replay attack,
A reception processing method. Part or all of the protected area is further encrypted with a block cipher,
The priority specifying step decodes only the block including the priority specifying information and the block including information for specifying the block including the priority specifying information, and obtains the priority specifying information;
The reception processing method according to claim 1. The priority specifying information is one or both of information included in a third layer header included in the protection area and information included in a fourth layer header;
The reception processing method according to claim 1 or 2. The packet is a packet in which a first packet composed of a first header and first data is encapsulated by a second header which is a header of the same layer as the first header,
The protected area includes the first packet;
The priority specifying information is priority information included in the first header;
The reception processing method according to claim 1 or 2. The reception processing method according to any one of claims 1 to 4, wherein a window size of the replay prevention window is larger as a priority is higher. The reception processing method according to claim 1, wherein a window size of the replay prevention window is smaller as the priority is higher. The reception processing method is:
A window reduction step of reducing a window size of the replay prevention window having a low priority when the usage amount of the computing resource exceeds the first threshold;
The reception processing method according to any one of claims 1 to 6, wherein: The reception processing method is:
When the usage amount of the computing resource falls below a second threshold, returning the reduced window size to the original size;
The reception processing method according to claim 7. The computing resource is a CPU load for receiving processing;
The reception processing method according to claim 7 or 8, wherein: The computing resource is the number of packets queued in a reception queue for queuing received packets until reception processing is started,
The reception processing method according to claim 7 or 8, wherein: The computing resource is a working memory amount for performing reception processing;
The reception processing method according to claim 7 or 8, wherein: The security protocol is IPsec;
The reception processing method according to any one of claims 1 to 11, wherein: A reception processing device for receiving a packet including a protected area protected from value rewriting by a security protocol,
The packet is
A sequence number determined for each set of security parameters used by the security protocol;
In the relay device on the communication path, including a priority indicating the priority when transferring the packet,
The protected area is
The sequence number;
Including priority specifying information for specifying the priority,
The reception processing device includes:
A security database for storing the security parameters;
A priority determination database for storing the correspondence between the priority specification information and the priority of the packet;
A reception processing unit for receiving the packet;
The reception processing unit
Using security parameters stored in the security database, authentication means for confirming that the protection area included in the packet has not been rewritten;
Searching the priority determination database using the priority specifying information as a key, and priority specifying means for obtaining the priority of the packet;
Window selection means for selecting the replay prevention window corresponding to the priority obtained in the priority specifying means from one or more replay prevention windows;
Using the replay window selected by the window selection means, determining whether or not the packet is due to a replay attack, and comprising replay prevention means for discarding the packet if it is due to a replay attack,
A reception processing device. Part or all of the protected area is encrypted with a block cipher,
The priority specifying means includes:
Obtaining the priority specifying information by decoding the block including the priority specifying information and the block including information for specifying the block including the priority specifying information using the security parameter;
The reception processing apparatus according to claim 13. The priority specifying information is one or both of information included in a third layer header and information included in a fourth layer header;
The reception processing apparatus according to claim 13 or 14, characterized in that: The packet is a packet in which a first packet composed of a first header and first data is encapsulated by a second header which is a header of the same layer as the first header,
The protected area includes the first packet;
The priority specifying information is priority information included in the first header;
The reception processing apparatus according to claim 13 or 14, characterized in that: The reception processing apparatus according to any one of claims 13 to 16, wherein a window size of the replay prevention window is larger as a priority is higher. The reception processing apparatus according to any one of claims 13 to 16, wherein a window size of the replay prevention window is larger as the priority is lower. The reception processing device further includes a resource monitoring unit that monitors the usage amount of the computing resource held by the reception processing device and notifies the usage amount of the computing resource when the usage amount exceeds a first threshold. ,
The reception processing unit, upon receiving a notification from the resource monitoring unit, reduces the window size of the replay prevention window having a low priority,
The reception processing apparatus according to claim 13, wherein The resource monitoring unit notifies when the usage amount of the computing resource falls below a second threshold,
Upon receiving the notification from the resource monitoring unit, the reception processing unit returns the window size of the low-priority replay prevention window to the original size,
The reception processing device according to claim 19. The computing resource is a CPU load of a CPU that performs reception processing;
21. The reception processing apparatus according to claim 19 or 20, wherein: The reception processing device includes a reception queue for queuing received packets until reception processing is started,
The computing resource is the number of packets queued in the reception queue;
21. The reception processing apparatus according to claim 19 or 20, wherein: The computing resource is an amount of working memory for receiving processing;
21. The reception processing apparatus according to claim 19 or 20, wherein: The security protocol is IPsec;
The reception processing apparatus according to any one of claims 13 to 23.

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