Abstract:
A system for secure communication, including a first security computer communicatively coupled with a client computer via an SSL connection, including a certificate creator, for receiving certificate attributes of a server computer certificate and for creating a signed certificate therefrom, and an SSL connector, for performing an SSL handshake with the client computer using the signed certificate created by said certificate creator, and a second security computer communicatively coupled with a server computer via an SSL connection, and communicatively coupled with the first security computer via a non-SSL connection, including an SSL connector, for performing an SSL handshake with the server computer using a signed certificate provided by the server computer, and a protocol appender, for appending attributes of the signed certificate provided by the server computer within a message communicated to the first security computer. A method is also described and claimed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 12/178,558, filed Jul. 23, 2008, entitled “SPLITTING AN SSL CONNECTION BETWEEN GATEWAYS,” the disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The field of the present invention is secure network communication. 
     BACKGROUND OF THE INVENTION 
     Secure Sockets Layer (SSL) is a protocol used to encrypt communication between a client computer and a server computer. In this regard, reference is now made to  FIG. 1A , which is a prior art diagram of a client-server system using one SSL connection. The SSL protocol enables a client computer  100  to authenticate a remote server computer  200 , by means of signed certificates. The SSL protocol utilizes a handshake procedure to exchange and validate a certificate, prior to establishing an encrypted connection. Generally, the handshake procedure degrades performance and causes latency. 
     Often a security gateway computer is used to inspect data being communicated between server computer  200  and client computer  100 . In this regard, reference is now made to  FIG. 1B , which is a prior art diagram of a client-server system with a security gateway computer  300 , using two SSL connections. Security gateway computer  200  may detect malicious content and confidential data. As seen in  FIG. 1B , the SSL protocol between client computer  100  and server computer  200  is split. Each side of security gateway computer  300  establishes a separate SSL connection. There is an SSL connection between client computer  100  and security gateway computer  300 , for which security gateway computer  300  acts as a server; and there is an SSL connection between security gateway  300  and server computer  200 , for which security gateway computer  300  acts as a client. The additional SSL handshake required by the additional SSL connection additionally degrades performance and causes additional latency. 
     Often security gateway computers operate in conjunction with third party gateway computers, such as content caching gateway computers. In this regard, reference is now made to  FIG. 1C , which is a prior art diagram of a client-server system with a security gateway computer  300  and a third party gateway computer  400 , using three SSL connections. Third party gateway computer  400  does not inspect the data content transmitted via the SSL connection and, as such, does not need to encrypt the data content. Nevertheless, since third party gateway computer  400  is networked within an SSL connection, it must re-establish the SSL connection on both of its sides. Although the topology of  FIG. 1C  is technically sound, it has a significant penalty in performance and latency due to the need to perform three SSL handshakes. Moreover, the penalty is magnified if third party gateway computer  400  is replaced with a plurality of third party gateway computers. 
     It would thus be of advantage to provide a more efficient way to network a security gateway computer with one or more third party gateway computers, when the one or more third party gateway computers do not need to inspect data content. 
     SUMMARY OF THE DESCRIPTION 
     Aspects of the present invention relate to a method and system for networking a security gateway computer with one or more third part gateway computers, when the third party gateway computers do not need to inspect the data content it receives and transmits. The third party gateway computers may be, for example, caching gateway computers. Embodiments of the present invention provide a network that requires only two SSL handshakes, regardless of the number of third party gateway computers in the network. In contrast, prior art networks require at least n+2 SSL handshakes, where n is the number of third party gateway computers in the network. 
     Embodiments of the present invention use two security gateway computers that surround the third party gateway computers. A permanent encrypted tunnel/pipe is established between the two security gateway computers. 
     To support SSL certificate validation of a server computer by a client computer, the security gateway computer adjacent to the client computer generates certificates with credential attributes of the server computer. Additionally, the security gateway computer adjacent to the client computer maintains an up-to-date certificate cache, so that the same certificate may be used for client requests to the same server computer. 
     There is thus provided in accordance with an embodiment of the present invention a system for secure communication, including a first security computer communicatively coupled with a client computer via an SSL connection, including a certificate creator, for receiving certificate attributes of a server computer certificate and for creating a signed certificate therefrom, and an SSL connector, for performing an SSL handshake with the client computer using the signed certificate created by said certificate creator, and a second security computer communicatively coupled with a server computer via an SSL connection, and communicatively coupled with the first security computer via a non-SSL connection, including an SSL connector, for performing an SSL handshake with the server computer using a signed certificate provided by the server computer, and a protocol appender, for appending attributes of the signed certificate provided by the server computer within a message communicated to the first security computer. 
     There is additionally provided in accordance with an embodiment of the present invention a method for secure communication, including forwarding, from a first security computer to a second security computer, a request from a client computer to connect to a server computer, establishing an SSL connection between the second security computer and the server computer, including performing, by the second security computer, an SSL handshake with the server computer using a signed certificate provided by the server computer, appending, by the second security computer, attributes of the signed certificate provided by the server computer within a message communicated to the first security computer, receiving, by the first security computer, certificate attributes of the server computer certificate, creating, by the first security computer, a signed certificate from the received certificate attributes of the server computer certificate, and establishing an SSL connection between the first security computer and the client computer, including performing an SSL handshake with the client computer using the signed certificate created by the creating. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings in which: 
         FIG. 1A  is a prior art diagram of a client server system using one SSL connection; 
         FIG. 1B  is a prior art diagram of a client-server system with a security gateway computer, using two SSL connections; 
         FIG. 1C  is a prior art diagram of a client-server system with a security gateway computer and a third party gateway computer, using three SSL connections; 
         FIG. 2  is a diagram of a client-server system with two security gateways and a third party caching gateway, using only two SSL connections, in accordance with an embodiment of the present invention; 
         FIG. 3  is a simplified flowchart of a method for establish an SSL connection between a client and server computer, when a security gateway computer and a third party gateway computer intermediate between the client and the server computers, in accordance with an embodiment of the present invention; 
         FIGS. 4A and 4B  are simplified flowcharts of an enhancement for the method of  FIG. 3 , using a certificate cache, in accordance with an embodiment of the present invention; and 
         FIG. 5  is a simplified block diagram of security gateway computers that cooperate in SSL certificate validation, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present invention relate to a communications network having an intermediary security gateway computer and one or more intermediary third part gateway computers, where the third party gateway computers do not need to inspect the data content they receive and send. Using embodiments of the present invention, the connection between a client and a server is split into two SSL connections, and two or more non-SSL connections. One of the two SSL connections is used for communication between the client and a first security gateway computer, and the other of the two SSL connections is used for communication between the server and a second security gateway computer. The two or more non-SSL connections are used for communications between a security gateway computer and a third party gateway computer, and for communications between two third party gateway computers. 
     The first and second security computers operative cooperatively to authenticate signed certificates that are provided by the server during an SSL handshake. The second security computer transmits to the first security computer the certificate attributes received from the server, and the first security computer acts as a certificate authority, and creates a certificate for the client based on the attributes of the server certificate. 
     Reference is now made to  FIG. 2 , which is a diagram of a client-server system with two security gateways and a third party caching gateway, using only two SSL connections, in accordance with an embodiment of the present invention. Shown in  FIG. 2  is a client computer  100  that communicates with a server computer  200  within a network in which a first security gateway computer  300   a , a third party gateway computer  400 , and a second security gateway computer  300   b  intermediate. Third party gateway computer  400  does not need to inspect that data content that it receives and sends. In some instances the data content passing through third party gateway computer  400  may need to be encrypted, and in other instances the data content may not need to be encrypted. 
     It will be appreciated by those skilled in the ensuing description that embodiments of the present invention apply as well to a topology wherein third party gateway computer  400  is a plurality of networked third party gateway computers. 
     Notable in  FIG. 2  is the use of two SSL connections and two non-SSL connections. As such, establishing a connection between client computer  100  and server computer  200  requires only two SSL handshakes. Specifically, security gateway computer  300   a  establishes an SSL connection with client computer  100 , and security gateway computer  300   b  establishes an SSL connection with server computer  200 . The connections between security gateway computer  300   a  and security gateway computer  300   b  are non-SSL connections, which are higher performance and lower latency connections than SSL connection. 
     Using the network topology of  FIG. 2 , client computer  100  and server computer  200  are still connected over SSL, and a certificate is exchanged and validated. If the communication between security gateway computers  300   a  and  300   b  is required to be encrypted, an encrypted tunnel/pipe is established between the security gateway computers, such as an Open-VPN tunnel. In cases where there are many connections between security gateway computers  300   a  and  300   b , a permanent encrypted tunnel/pipe is established between them. 
     For the network topology of  FIG. 2  to support SSL certificate validation, security gateway computers  300   a  and  300   b  perform special processing, as described hereinbelow regarding the methods of  FIGS. 3 and 4 . 
     Reference is now made to  FIG. 3 , which is a simplified flowchart of a method for establish an SSL connection between a client and server computer, when a security gateway computer and a third party gateway computer intermediate between the client and the server computers, in accordance with an embodiment of the present invention. The flowchart of  FIG. 3  is divided into five columns. Starting from the left, the first column includes steps performed by client computer  100  (“client”), the second column includes steps performed by security gateway computer  300   a  (“security gateway A”), the third column includes steps performed by third party gateway computer  400  (“third party gateway”), the fourth column includes steps performed by security gateway computer  300   b  (“security gateway B”), and the fifth column includes steps performed by server computer  200  (“server”). 
     At step  1105 , the client computer sends an SSL request to security gateway A, to establish a connection, using the CONNECT request method. At step  1110  security gateway A establishes a connection to the third party gateway. If an encrypted connection is desired, then security gateway A establishes an encrypted connection to the third party gateway using, for example, Open-VPN. If subsequent connection requests are anticipated, then the connection between security gateway A and the third party gateway remains as a tunnel/pipe, in order not to disconnect. 
     At step  1115  the third party gateway accepts the connection with security gateway A. At step  1120  the third party gateway establishes a connection to security gateway B. As above, if an encrypted connection is desired, then the third party gateway establishes an encrypted connection to security gateway B using, for example, Open-VPN. Also as above, if subsequent connection requests are anticipated, then the connection between the third party gateway and security gateway B remains as a tunnel/pipe, in order not to disconnect. 
     At step  1125  security gateway B sends an SSL request to the server, to establish a connection, using the CONNECT request method. At step  1130  security gateway B and the server perform an SSL handshake to authenticate a server certificate. Upon success of the handshake, an SSL connection is established between security gateway B and the server. At step  1135  security gateway B appends the server certificate attributes to a header in the protocol, such as an HTTP reply header. Certificate attributes generally include inter alia a domain name and a validity date. 
     At step  1140  security gateway B replies to the third party gateway with a CONNECT reply message. The reply includes the server certificate attributes in its header. At step  1145  the third party gateway forwards the reply received from security gateway B to security gateway A. 
     At step  1150  security gateway A creates an SSL certificate using the attributes of the server certificate. Finally, at step  1155  security gateway A and the client perform an SSL handshake to authenticate the certificate created by security gateway A. Upon success of the handshake, an SSL connection is established between security gateway A and the client. At this stage, subsequent requests from the client to the server may be communicated over the established connections. 
     In accordance with an embodiment of the present invention, the method of  FIG. 3  may be enhanced by maintaining a local certificate cache at security gateway A. Such a cache obviates the need to security gateway B to send the server certificate attributes to security gateway A. Instead, a cached server certificate is used. However, certificates often expire and are renewed. In order that the certificate cache at security gateway A be up-to-date, security gateway B sends updated server certificates to security gateway A when the server certificates change. 
     In this regard, deference is now made to  FIGS. 4A and 4B , which are a simplified flowchart of an enhancement for the method of  FIG. 3 , using a certificate cache, in accordance with an embodiment of the present invention. The flowchart of  FIGS. 4A and 4B  is divided into five columns, as described above with reference to  FIG. 3 . 
     At step  1205  the client sends an SSL request to security gateway A, to establish a connection, using the CONNECT request method. At step  1210  security gateway A checks its local certificate cache to determine if a certificate for the requested server name is already available in cache. If so, then at step  1215  security gateway A generates a fingerprint or hash of the server certificate, and at step  1220  security gateway A appends the fingerprint/hash to a connection request. Otherwise, if it is determined at step  1210  that a certificate for the requester server name if not available in cache, then processing advances directly to step  1225 , by-passing steps  1215  and  1220 . 
     At step  1225  security gateway A establishes a connection to the third party gateway. The connection request will include the fingerprint/hash of the server certificate if steps  1215  and  1220  were performed. If encryption between security gateway A and the third party gateway is desired, then an encrypted connection is established, using, for example, Open-VPN. If subsequent requests are anticipated, then the connection between security gateway A and the third party gateway remains as a tunnel/pipe, in order that it not disconnect. 
     At step  1230  the third party gateway accepts the connection with security gateway A. At step  1235  the third party gateway establishes a connection to security gateway B. The connection request received by security gateway B from the third party gateway will include the server certificate attributes if steps  1215  and  1220  were performed. As above, if encryption between the third party gateway and security gateway B is desired, then an encrypted connection is established, using, for example, Open-VPN. Also as above, if subsequent requests are anticipated, then the connection between the third party gateway and security gateway B remains as a tunnel/pipe, in order that it not disconnect. 
     At step  1240  security gateway B sends a SSL request to the server, to establish a connection, using the CONNECT request method. At step  1245  security gateway B and the server perform an SSL handshake to authenticate a server certificate. Upon success of the handshake, an SSL connection is established between security gateway B and the server. 
     At step  1250  security gateway B determines whether a fingerprint/hash of the server certificate was included in the request made at step  1235 . If so, then at step  1255  security gateway B generates a fingerprint or hash of the certificate it received from the server during the SSL handshake at step  1245 . At step  1260  security gateway B compares the fingerprint/hash received at step  1235  with the fingerprint/hash generated at step  1255 . If the two fingerprints/hashes do not match, then the server certificate was recently updated, and the server certificate cached at security gateway A is no longer valid. At step  1265  security gateway B appends the certificate attributes from the server certificate received at step  1245 , to a header in the protocol, such as an HTTP reply header. Otherwise, if the two fingerprints/hashes compared at step  1260  do match, then the server certificate cached at security gateway A is still valid. In this case, processing advances directly to step  1270 , by-passing step  1265 , and no certificate attributes are appended to the reply message. 
     If security gateway B determines at step  1250  that a fingerprint/hash was not included in the request received at step  1235 , then processing advances directly to step  1265 , by-passing steps  1255  and  1260 . 
     At step  1270  security gateway B replies to the third party gateway with a connection reply message. At step  1275  the third party gateway forwards the reply received from security gateway B to security gateway A. 
     At step  1280  security gateway A determines whether server certificate attributes are included in the reply message received from the third party gateway computer at step  1275 . If so, then at step  1285  security gateway A creates an SSL certificate using the attributes included in the reply message, and stores the created certificate in its local cache for subsequent access. Otherwise, at step  1290  security gateway A retrieves its cached certificate. 
     Finally, at step  1295  security gateway A and the client perform an SSL handshake to authenticate the certificate created at step  1285  or the cached certificate, as appropriate. Upon success of the SSL handshake, an SSL connection between gateway server A and the client is established. At this stage, subsequent requests from the client to the server are communicated over the established connections. 
     Reference is now made to  FIG. 5 , which is a simplified block diagram of security gateway computers  300   a  and  300   b  that cooperate in SSL certificate validation, in accordance with an embodiment of the present invention. Security gateway computers  300   a  and  300   b  are operative to perform the steps in  FIGS. 3, 4A and 4B  that apply to security gateways A and B, respectively. In addition to the components shown in  FIG. 5 , each of security gateway computers  300   a  and  300   b  includes standard computer hardware (not shown), including inter alia one or more processors, one or more hard disk drives, RAM, a communication bus, one or more network interfaces, and I/O drivers including inter alia drivers for a keyboard, a mouse and a graphical display. 
     As shown in  FIG. 5 , security gateway computer  300   a  includes an SSL connector  310   a , for establishing an SSL connection between security gateway computer  300   a  and a client computer. SSL connector  310   a  is used in performing step  1155  of  FIG. 3  and step  1295  of  FIG. 4B . Security gateway computer  300   a  also includes a non-SSL connector  320   a , for establishing a non-SSL encrypted or non-encrypted connection between security gateway computer  300   a  and a third party gateway computer. Non-SSL connector  320   a  is used in performing step  1110  of  FIG. 3  and step  1225  of  FIG. 4A . Security gateway computer  300   a  also includes a certificate creator  330   a , for creating a signed certificate for attributes of a server certificate. Certificate creator  330   a  is used in performing step  1150  of  FIG. 3  and step  1285  of  FIG. 4B . 
     Security gateway computer  300   b  includes an SSL connector  310   a , for establishing an SSL connection between security gateway computer  300   b  and a server computer. SSL connector  310   b  is used in performing step  1130  of  FIG. 3  and step  1245  of  FIG. 4A . Security gateway computer  300   b  also includes a non-SSL connector  320   b , for establishing a non-SSL encrypted or non-encrypted connection between security gateway computer  300   b  and a third party gateway computer. Non-SSL connector  320   b  is used in performing step  1120  of  FIG. 3  and step  1235  of  FIG. 4 . Security gateway computer  300   b  also includes a protocol appender  340   a , for appending certificate attributes within a protocol request. Protocol appender  340   a  is used in performing step  1135  of  FIG. 3  and step  1265  of  FIG. 4 . 
     For use in the enhanced method of  FIG. 4 , security gateway computer  300   a  also includes a local certificate cache  350  for storing and retrieving attributes of signed server certificates. In addition, security gateway computer  300   a  includes a certificate encoder  360   a  for deriving a hash value for cached certificate attributes, and a protocol appender  340   a  for appending the hash value to a protocol message. Certificate encoder  360   a  is used in performing step  1215  of  FIG. 4A , and protocol appender  340   a  is used in performing step  1220  of  FIG. 4A . 
     Further for use in the enhanced method of  FIGS. 4A  and B, security gateway computer  300   b  also includes a certificate encoder  360   b  for deriving a hash value for attributes of a certificate provided by the server computer, and a certificate comparator  370   b  for comparing hash values generated by certificate encoder  360   a  with a hash value generated by certificate encoder  360   b . Certificate encoder  360   a  is used in performing step  1255  of  FIG. 4B , and certificate comparator  370   b  is used in performing step  1260  of  FIG. 4B . 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific exemplary embodiments without departing from the broader spirit and scope of the invention as set forth in the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.