Abstract:
A method, system, and device for encrypted packet inspection allowing an authorized third party device to monitor cryptographic handshaking information (full- duplex) between two other devices and together with the secret private key then transparently decrypt the bulk encrypted data stream. 
     The scope of this invention encompasses many applications, three examples of which are firewalls, load balancers, and local network caches. Additionally, this invention achieves and contributes to the efficient handling of encrypted information in other ways, three examples of which are making switching, routing, and security decisions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the following U.S. Provisional Applications, all of which are hereby incorporated by reference: 
     
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                 COMMONLY OWNED AND PREVIOUSLY FILED 
               
               
                 U.S. PROVISIONAL PATENT APPLICATIONS 
               
             
          
           
               
                 Atty. Dkt. # 
                 Ser. No. 
                 Title 
                 Filing Date 
               
               
                   
               
               
                 501143.000011 
                 60/300,955 
                 Add-Drop Layer 3 Ethernet Ring Switch 
                 Jun. 26, 2001 
               
               
                 501431.000014 
                 60/326,266 
                 Application Specific Information Processing 
                 Oct. 1, 2001 
               
               
                   
                   
                 System 
               
               
                 501143.000026 
                 60/357,243 
                 Encrypted Packet Inspection 
                 Feb. 15, 2002 
               
               
                   
               
             
          
         
       
     
     The current application may share some specification and figures with the following commonly owned and previously filed application, which is hereby incorporated by reference: 
     
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                 COMMONLY OWNED AND PREVIOUSLY FILED 
               
               
                 U.S. NONPROVISIONAL PATENT APPLICATIONS 
               
             
          
           
               
                 Atty. Dkt. # 
                 Ser. No. 
                 Title 
                 Filing Date 
               
               
                   
               
               
                 501143.000019 
                 10/068,295 
                 Application-Specific Information-Processing 
                 Feb. 5, 2002 
               
               
                   
                   
                 Method, System, and Apparatus 
               
               
                   
               
             
          
         
       
     
     The benefit of 35 U.S.C. §120 is claimed to the maximum extent allowable by law for all of the above referenced commonly owned applications. The contents of the applications referenced in the tables above are not necessarily identical to the contents of this application. 
     All references cited hereafter are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes and indicative of the knowledge of one of ordinary skill in the art. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to cryptography and in particular to networking cryptography. 
     2. Description of Related Art 
     SSL/TLS is the de facto method of encrypting information over the public Internet, particularly for e-commerce applications. SSL/TLS is a protocol that operates between Layer 4 (called the Transport Layer) and Layer 5 (called the Session Layer) of the OSI protocol stack. Typically, the Layer 4 protocol used for SSL/TLS is TCP while protocol for Layer 5-7 (sometimes referred to as the Application Layer as an aggregate layer) is HTTPS (secured). 
     SSL/TLS basically encrypts the Application Layer information which commonly is HTTPS data which might contain sensitive financial records or passwords or credit card numbers for purchasing products from an e-commerce website. The benefit to consumers of using SSL/TLS is that their financial transactions are secured to a very high degree over the public Internet. Today, the most common key size of 1,024 bits is thought to be unbreakable for at least 5-10 years by some estimates. SSL/TLS is supported in almost all major web browsers such as MS Explorer and Netscape Navigator. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention includes a method, system, and device for encrypted packet inspection allowing an authorized third party device to monitor cryptographic handshaking information (full-duplex) between two other devices and together with the secret-private key then transparently decrypt the bulk encrypted data stream. 
     The scope of this invention encompasses many applications, three examples of which are firewalls, load balancers, and local network caches. Additionally, this invention achieves and contributes to the efficient handling of encrypted information in other ways, three examples of which are making switching, routing, and security decisions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The figures are not necessarily drawn to scale. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein. 
         FIG. 1  shows an encrypted packet inspection (EPI) device monitoring one cryptographic session, in accordance with an embodiment of the present invention. 
         FIG. 2  shows an EPI device terminating two cryptographic sessions, in accordance with an embodiment of the present invention. 
         FIG. 3  shows a flowchart of a cryptographic session being established with EPI device monitoring, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     E-commerce infrastructures today use switches, caches and firewalls which feature “deep packet inspection”, a term that usually means that the information at Layers 5-7 is examined for making switching, routing or security decisions. As an example, some website switches recognize URL information in order to switch users to specific servers. Another example is reading a user&#39;s “cookie” to allow that person to access the same server (sometimes called “stickiness”). 
     However, SSL/TLS traffic presents a significant obstacle to website infrastructure equipment since it encrypts all Layer 5-7 data. Thus a load balancer cannot decipher a user&#39;s cookie in an SSL/TLS-encrypted session without using decryption in order to switch that user to the best server for his application. Firewalls typically cannot implement URL blocking of SSL/TLS traffic and usually passes such data through without any filtering or intrusion detection. Caches cannot determine if an SSL/TLS encrypted HTML object or web page is a hit or not without using decryption. 
     IT managers can alleviate this problem by terminating SSL/TLS sessions at the edge of their network and then routing plaintext traffic throughout the rest of their infrastructure. However, this is not always feasible since SSL/TLS for security purposes is usually terminated close to the server farm. Most network edge architectures use a router and firewall and Layer 2/3 switch before SSL/TLS can be terminated. In some cases, SSL/TLS sessions are terminated right at each server via an add-in SSL/TLS accelerator card that maintains the end-to-end security of the session (i.e., from the client at his home to the server in the e-commerce site). Hence, there are many reasons why terminating SSL/TLS early (i.e. before most of the equipment using Layer 5-7 information) at the network edge may not feasible or desirable. 
     Referring to an embodiment illustrated in  FIG. 1 , a server  131  is connected to a server-farm network  125  for servers  130 . The server  131  terminates an SSL/TLS connection  140  using an SSL/TLS accelerator card  135 . This is only one possible implementation providing the SSL/TLS termination  136  necessary in the embodiment. An encrypted-packet-inspection-enabled architecture  100  allows multiple devices in a data center or enterprise infrastructure to passively and non-invasively monitor the encrypted traffic of an SSL/TLS session  140 . An EPI device would monitor all SSL/TLS sessions  140  as directed by the host and offer up decrypted, plaintext data  109  upon demand or as streaming data. In addition, the EPI device  112  would allow equipment such as local network caches to cache SSL/TLS-protected web pages and objects. In all of these applications the end-to-end nature of SSL/TLS session  140  is preserved including the public key negotiation, MD-5 or SHA-1 authentication, and symmetric bulk encryption. The client  105  and server  131  are unaware of the monitoring occurring by a box  112  in the middle of the connection. 
     In order for the EPI device  112  to work, it must be loaded with the same set of private certificate keys  114  that the server  131  uses. Once an EPI device  112  has the private certificate keys  114 , its traffic monitor  116  can then monitor the initial key exchange of an SSL/TLS handshake and then determine the resulting symmetric keys used for bulk encryption. Note that the EPI device  112  does not interfere with the handshaking at all; it only begins to deliver decrypted information  109  from its decryption engine  118  to the host  120  once bulk encryption is being used for data transfer. Thus, a completely separate device  112  can monitor all the SSL/TLS handshaking information (full-duplex) and together with the secret private key then transparently decrypt the bulk encrypted data stream in either direction. 
     Device  120  is shown in the detailed descriptions of these embodiments as a Customer Application Specific Integrated Circuit or Network Processing Unit (ASIC/NPU) for purpose of example. But device  120  can be any system application circuitry without departing from the scope of the claimed invention. Examples of implementations of device  120  are any processor, ASIC, FPGA, NPC, CPU, memory, RISC, any collection of other processors (even networked devices), etc. For clarity, any customer provided circuitry could be included within the meaning of system application circuitry — here discussed using the example of ASIC/NPU  120 . 
     The SSL/TLS session  140  includes data  106  sent from the server  131  to the client  105  and also data  108  sent from the client  105  to the server  131 . In  FIG. 1 , the client  105  is shown as being connected to the server  131  by a network  107 , but that is not a requirement. 
     Note that servers  130  and network  125  are not relevant to the scope of the invention, but are present for illustrative purposes only. Similarly, the specific device terminating the server end of the SSL/TLS connection does not need to be a device like SSL/TLS accelerator card  135 . Rather, the terminating device  136  can be anything capable of terminating an SSL/TLS session. Examples of  136  are hardware termination, software termination, third-party external termination, etc. 
     Other embodiments utilize encryption other than SSL/TLS without departing from the scope of this invention. An example would be an embodiment that employs the IPSec security protocol and its associated encryption methods to secure network data. 
     Referring to  FIG. 2 , the EPI device  112  intermediates. That is, it maintains an SSL/TLS session  240  with the client (not shown) and an SSL/TLS session  242  with the server  131 . The sessions  240  and  242  are maintained such that the client and the server  131  are not aware of the EPI device&#39;s participation in their communication. As in the  FIG. 1  embodiment, the server  131  terminates its SSL/TLS session with the SSL/TLS accelerator card  135 . This is only one possible implementation providing the SSL/TLS termination  136  necessary in this embodiment. Also, the server  131  is connected to a server farm network  125  having servers  130 . 
     An additional mode that the EPI device  112  supports is network caching data insertion. Basically, when the local cache  210  has a hit, as determined by Customer ASIC/NPU  120 , it can deliver the web page or object information to the EPI device  112 . Note that in this embodiment, the EPI device  112  and the Customer ASIC/NPU  120  exchange plaintext  230 ,  231 ,  232 , and  233 . The Customer ASIC/NPU  120  can merge data from content cache  210  and send that along to the EPI device  112  for encryption. If that data is outgoing to a client in a typical Internet scenario, it could reduce apparent latency and also reducing server  131  loading. The Customer ASIC/NPU  120  may also need to block the HTTP request to the server  131  and consequently may alter the cleartext traffic  231  fed to the EPI device for this purpose. But one of the caveats of SSL/TLS encryption is that the symmetric keys used for bulk encryption change dynamically based on the information in the previous SSL/TLS record. Therefore, to keep endpoints of the SSL/TLS connection  244  in sync, the EPI device would keep an encryption state table in which client and server symmetric bulk encryption keys for each direction are stored. SSL/TLS data  220  from the client would then be decrypted with one key and reencrypted with another key to send the information  221  to the server in sync with the server. Similarly SSL/TLS data  222  from the server would be decrypted with one key and reencrypted with another key to send the information  223  to the client in sync with the client. In  FIG. 2  the client (not shown) is connected to the EPI device  112  via the Internet  107 , but that is not required. 
     Referring to  FIG. 3 , an SSL/TLS session is typically initiated by a client (which might be a consumer using his PC at home  302 ) by clicking on a URL that begins with HTTPS  304 . This link might take the client to a secure web page for ordering a product or accessing confidential information such as an on-line bank account. Before the client and server can communicate with symmetric bulk encryption  308 , the SSL/TLS handshaking process  306  must be completed. An object of the handshaking is to mutually determine the secret keys that are used in the bulk encryption of data between the client and the server(s) that is providing the web page content. The secret keys are established via public key cryptography that allows the client and the server to share a secret over a non-secure channel (i.e., the World Wide Web). 
     The SSL/TLS handshaking  306  is shown in more detail in the flowchart breakout  306 . In that flowchart breakout  306 , the server sends its public key to the client  310 ; the client then encrypts a parameter called the pre_master_secret (shown in the figure as “secret key material”) with the server&#39;s public key  312  and then sends that to the server  314 . The server in turn decrypts this message with its private key  316 . In  317  the server and client each derive a shared secret symmetric key for bulk encryption from the secret key material by calculating an algorithm called the Key Derivation Function (KDF) that expands the pre_master_secret into the master_secret and ultimately into the actual symmetric bulk encryption keys used for the session. Since both the client and server use the same KDF algorithm, their symmetric bulk encryption keys are now implicitly shared between both ends of the connection  318 . Any subsequent data transfer between the client and server for this session (such as HTML web page information, credit card numbers, etc) will be encrypted with these secret keys and some negotiated bulk encryption algorithm such as ARC4, Triple DES (3DES) or AES. Today, it is common for ARC4 to be used with a 128-bit key. 
     A third party observing the SSL/TLS handshaking will not be able to discover the shared secret keys since it does not have access to the private key that the server is using. Trying to factor a private key is extremely difficult and it is estimated that current 1024 -bit RSA keys, for example, are safe from hacking for 5-10 years. 
     An EPI device acts as an authorized third party in that the same private certificate key that the server is using has been loaded into the EPI device. This assumes that the IT manager for a secure website allows private keys to be loaded into devices such as firewalls and other devices within his infrastructure or LAN. With the server&#39;s private key in hand, an EPI device can then monitor the full-duplex SSL/TLS handshaking process and finally determine what the secret keys used for the symmetric bulk encryption phase. This involves capturing all SSL/TLS handshaking messages such as “Client Hello”, “Server Hello”, “Client Key Exchange”, etc. 
     Once the SSL/TLS handshaking is complete, the EPI device provides the host with a decrypted data stream that represents the transmitted plaintext information from the client. The EPI device can also decrypt the transmitted data stream from the server as well, although for most applications the client information is of highest interest. 
     As mentioned earlier, the operation of an EPI device changes if a local networking cache is used. As cache data is transmitted out to the client (instead as from the server), the 2 ends of the connection will become unsynchronized in terms of the symmetric bulk encryption keys. The EPI device must then translate between the bulk encryption keys that the client is using and the ones that the server is using. Therefore, connection information for the session is created which tracks the 4 bulk encryption keys now needed to keep the client and server oblivious to the presence of the EPI device. Incoming data from the Client is decrypted using its bulk encryption key and then supplied to the host. The filtered data from the host is then re-encrypted using the server&#39;s assumed bulk encryption key for this direction of traffic flow and then transmitted on to the server. Data from the server goes through a similar process on its way to the client. 
     In the case of the caching application, the EPI device must also keep track of the hashing information that is used to authenticate each SSL/TLS record that is transferred. 
     An embodiment of the present invention implements a firewall. This firewall embodiment can read SSL/TLS data will permit that device to use all of its Layer 5-7 access control and intrusion detection tools. 
     Another embodiment of the present invention implements a load balancer. Such a load balancer can decrypt cookie and URL information in order to make better load balancing decisions. 
     Yet another embodiment of the present invention implements a local network cache. These caches can monitor SSL/TLS sessions for content cache hits which is presently impossible with most caching devices today without actually terminating SSL/TLS sessions. One important advantage that can be achieved by some embodiments of the present invention is allowing new content to be transmitted in the middle of the SSL/TLS connection without the client or server being aware of the EPI device&#39;s presence. 
     Some embodiments of this invention operate with SSL/TLS sessions, so SSL/TLS handshaking is described. But other embodiments of this invention operate with other cryptographic protocols. 
     Some embodiments of the present invention are adapted to operate with packet-based communications protocols. Examples include UDP, TCP, etc. But the claimed invention extends in scope beyond any specific communication protocol. 
     World Wide Web communications content has been described in detail, such as HTTP content within an SSL/TLS session. But other embodiments of the present invention handle other, possibly very different, communications content. Examples include POP, FTP, etc. 
     Glossary 
     “AES” means Advanced Encryption Standard, as described in Federal Information Processing Standard Publication 197, issued by the National Institute of Standards and Technology on Nov. 26, 2001. 
     “ARC4” means a stream cipher. ARC4 is an abbreviation of Alleged RC4. RC4 is a trademark of RSA Data Security Inc. 
     “Cryptographic handshaking” means the establishment of a cryptographic session. An example of cryptographic handshaking is SSL/TLS handshaking. 
     “Cryptographic session” means a communications link in which symmetric key encryption is used after being established with asymmetric key encryption. Examples of cryptographic sessions are an SSL/TLS session, IPSec tunnel, etc. 
     “Intermediate” means to terminate a first and second connection, transfer incoming information from the first connection as outgoing information to the second connection, and transfer incoming information from the second connection as outgoing information to the first connection. 
     “Intrusion detection tools” means tools that monitor system and network resources and activities. That information is used to identify possible intrusions. 
     “Layer 5-7 intrusion detection tools” means intrusion detection tools that are able to monitor system and network resources and activities at OSI Layers 5-7, or equivalent layer(s) in other communications standards. 
     “Noninvasive monitoring” means receiving packets of a communication transparently so the noninvasive reception and the noninvasive receiver are undetected by either the sender or the intended recipient. The intended recipient receives the monitored packet as if unmonitored. 
     “OSI” means Open Systems Interconnect, an ISO standard for worldwide communications that defines a networking framework for implementing protocols in seven layers. 
     “Packet” means any protocol data unit including a header and payload data or their equivalents. For example, TCP segments, IP datagrams, etc. 
     Any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. §112, ¶6. In particular, the use of “step of” in the claims herein is not intended to invoke the provision of 35 U.S.C. §112, ¶6. 
     It should be apparent from the foregoing that an invention having significant advantages has been provided. While the invention is shown in only a few of its forms, it is not just limited to those forms but is susceptible to various changes and modifications without departing from the spirit thereof.