# Patent

## Title
Strong SSL proxy authentication with forced SSL renegotiation against a target server

## Abstract

An encrypted session is established between a client device and a target server device when the client device initiates network connections through a proxy device. The client device initiates an encrypted session with the proxy device. Once the encrypted session is established, the client device communicates the address of the target server device to the proxy device. Then, the proxy device sends an encrypted session renegotiation message to the client device. The client device responds to the encrypted session renegotiation message by transmitting an encrypted session handshake message to the proxy device. The proxy device forwards the encrypted session handshake message to the target server device, and continues to forward handshake messages between the client device and the target server device, enabling the client device and the target server device to establish an encrypted session.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application, titled “Proxy SSL Handoff Via Mid-Stream Renegotiation” Ser. No. 61/315,857 filed on Mar. 19, 2010, the benefit of which is hereby claimed under 35 U.S.C. §119(e), and which is further incorporated herein by reference.


TECHNICAL FIELD
The present invention relates generally to establishing an encrypted connection between a client device and a target server device.
TECHNICAL BACKGROUND
An increasing number of applications within an enterprise are provided over Secure Sockets Layer (SSL), Transport Layer Security (TLS), or any number of protocols that network devices may use to communicate over an encrypted session. Maintaining security while increasing performance and reliability of such encrypted sessions is of practical benefit to end users, system administrators, infrastructure providers, and the like.
In some scenarios, encrypted sessions are created between two devices, such as a client device and a server device, when one device opens a network connection to the other device and initiates a handshake protocol. However, some devices are not able to or are not allowed to initiate a network connection directly with other devices. For example, due to corporate security policies, some computing devices may first need to initiate a network connection to a proxy device, such as a SOCKS proxy, which will then create a network connection with the target device. However, as the initiating device and the target device are not in direct communication, establishing an encrypted session between the initiating device and the target device is an ongoing challenge. Thus, it is with respect to these considerations and others that the present invention has been made.



BRIEF DESCRIPTION OF THE DRAWINGS
Non-limiting and non-exhaustive embodiments are described with reference to the following drawings. In the drawings, like reference numerals refer to like parts throughout the various figures unless otherwise specified.
For a better understanding of the described embodiments, reference will be made to the following Detailed Description, which is to be read in association with the accompanying drawings, wherein:
FIG. 1 illustrates a functional block diagram illustrating an environment for practicing various embodiments;
FIG. 2 illustrates one embodiment of a network device that may be included in a system implementing various embodiments;
FIG. 3 illustrates one embodiment of a server device that may be included in a system implementing various embodiments;
FIG. 4 illustrates a logical flow diagram generally showing one embodiment of an overview of a process for replacing an endpoint in an end-to-end encrypted connection;
FIG. 5 illustrates a logical flow diagram generally showing one embodiment of a process for generating a session key associated with an end-to-end encrypted session;
FIG. 6 illustrates a logical flow diagram generally showing one embodiment of a process for replacing an endpoint in an, end-to-end encrypted connection with a second server device;
FIG. 7 illustrates a logical flow diagram generally showing one embodiment of a process for enhancing data transmitted between a client-side traffic management device (TMD) and a server-side TMD over the encrypted connection;
FIG. 8 illustrates one embodiment of a signal flow diagram generally usable with the process of FIG. 4;
FIG. 9 illustrates a functional block diagram illustrating a client device connected to a target server device through a proxy device; and
FIG. 10 illustrates a logical flow diagram showing one embodiment of a process for creating an encrypted session between a client device and a server device through a proxy device.



DETAILED DESCRIPTION
In the following detailed description of exemplary embodiments, reference is made to the accompanied drawings, which form a part hereof, and which show by way of illustration examples by which the described embodiments may be practiced. Sufficient detail is provided to enable those skilled in the art to practice the described embodiments, and it is to be understood that other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope. Furthermore, references to “one embodiment” are not required to pertain to the same or singular embodiment, though they may. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the described embodiments is defined only by the appended claims.
Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. As used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.”
As used herein, application layer refers to layers 5 through 7 of the seven-layer protocol stack as defined by the ISO-OSI (International Standards Organization-Open Systems Interconnection) framework.
As used herein, the term “network connection” refers to a collection of links and/or software elements that enable a computing device to communicate with another computing device over a network. One such network connection may be a Transmission Control Protocol (TCP) connection. TCP connections are virtual connections between two network nodes, and are typically established through a TCP handshake protocol. The TCP protocol is described in more detail in Request for Comments (RFC) 793, available from the Internet Engineering Task Force (IETF), and is hereby incorporated by reference in its entirety. A network connection “over” a particular path or link refers to a network connection that employs the specified path or link to establish and/or maintain a communication. The term “node” refers to a network element that typically interconnects one or more devices, or even networks.
As used herein, including the claims, the term “SSL” refers to SSL, TLS, Datagram Transport. Layer Security (DTLS) and all secure communications protocols derived therefrom. The SSL protocol is described in Netscape Communications Corp, Secure Sockets Layer (SSL) version 3 (November 1996), and the TLS protocol is derived from SSL, and is described in Dierks, T., and Allen, C., “The TLS Protocol Version 1.0,” RFC 2246 (January 1999), available from the IETF. The DTLS protocol is based on the TLS protocol, and is described in Rescorla, E., and Modadugu, N., “Datagram Transport Layer Security,” RFC 4347 (April 2006), available from the IETF. Each of these documents is incorporated herein by reference in their entirety. An SSL connection is a network connection that is secured by cryptographic information derived from an SSL protocol. The SSL protocol operates between an application layer (such as one or more of OSI layers 5-7) and a transport layer (such as OSI layer 4). The SSL protocol may provide security for application layer protocols such as HyperText. Transfer Protocol (HTTP), Lightweight Directory Access Protocol (LDAP), Internet Messaging Access Protocol (IMAP), or the like. For example, HTTP over SSL (HTTPS) utilizes the SSL protocol to secure HTTP data. The SSL protocol may utilize Transport Control Protocol/Internet Protocol (TCP/IP) on behalf of the application layer protocols to transport secure data. The SSL protocol may also employ a certificate. In one embodiment, the certificate is an X.509 certificate, such as those described in RFC 2459, available from the IETF, which is also incorporated herein by reference.
As used herein, an SSL session refers to a secure session over a network between two endpoints, wherein the session is secured using the SSL protocol. Although an SSL session is generally described herein as being established between a client device and a server device over a network, it should be understood that an SSL session may be established between virtually any types of network devices enabled to employ the SSL protocol. The SSL protocol uses a series of SSL handshakes (i.e. an SSL handshake protocol) to initiate an SSL session. An SSL session is associated with a master secret (also known as a session key) that results from the SSL handshakes. An SSL session is further associated with additional secret data that enables the SSL session (e.g. pre-master secret, random data, server's public and private keys and/or client's public and private keys). The SSL protocol also includes an SSL re-handshake procedure for renegotiating an SSL session. The renegotiated SSL session may be associated with the current SSL session or with another SSL session. An SSL session may employ one or more underlying network connections.
As used herein, the term SSL connection refers to a network connection employed by an SSL session to transmit encrypted data. An SSL connection is created at the request of a client device or a server device that are endpoints of an established SSL session. Regardless of which device requests the SSL connection, one or more keys used to encrypt/decrypt data transmitted over the SSL connection are independently derived by the client device and the server device based on the master secret of the associated SSL session.
Briefly, SSL supports at least four content types: application_data, alert, handshake, and change_cipher_spec. Alert, handshake, and change_cipher_spec content types are associated with messages for managing the SSL protocol. For example, an SSL alert is of the alert content type and is used for signaling, among other things, error conditions. SSL has provisions for other content types, but these capabilities are not commonly used.
The SSL handshake protocol includes the exchange and processing of a series of messages, which may be one of an alert, handshake, and/or change_cipher_spec content type. One or more SSL handshake messages are encapsulated within one or more network records of the handshake content type. The SSL handshake message also includes an associated SSL handshake type, and one or more data fields.
The SSL handshake protocol typically begins with the client device sending to the server device, among other things, randomly generated data within a CLIENT-HELLO message (e.g. an SSL handshake message with an associated SSL handshake type of “CLIENT-HELLO”). The server device responds to the CLIENT-HELLO message with, among other things, randomly generated data within a SERVER-HELLO message. Further, the server may provide a server certificate which the client may use to authenticate the server. Moreover, in some embodiments the server may request a client certificate which the server may authenticate in order to validate the client.
The client device, using the randomly generated data exchanged in the CLIENT-HELLO and SERVER-HELLO messages, generates a pre-master secret for an SSL session. In one embodiment, the client device may also include another random number in the pre-master secret, one that has typically not been transmitted over a public network in the clear. The client device then sends the pre-master secret to the server device in an SSL handshake message. In one embodiment, the pre-master secret may be encrypted using a public key associated with the server (obtained from the server's SERVER-HELLO message). Typically, the SSL handshake message that includes the pre-master secret is a CLIENT-KEY-EXCHANGE handshake message. Then, each of the client device and the server device, separately, perform a series of steps to generate a master secret using the pre-master secret. This master secret is associated with the SSL session, and is also known as a session key. Once an SSL session has been established, either the client device or the server device may requests that an SSL connection be created. Creation of an SSL session includes independently generating a key at both the client device and the server device based on the shared master secret. Connection keys may include, but are not limited to, cipher keys used to encrypt and decrypt communicated data over the SSL session, and/or authentication keys used verify messages received over the SSL session. The client device and the server device may then use their respective instances of the connection key(s) to generate and send messages containing encrypted payloads to each other.
As used herein, including the claims, the term “encrypted session” refers to a communications session between two endpoint devices over a network, encrypted in some way so as to secure the session. Example encrypted sessions may include SSL, TLS, and DTLS sessions. An encrypted session is associated with a master secret, also known as, a session key. As used herein, the term “encrypted connection” refers to any network connection secured by cryptographic information, such as SSL, TLS, and DTLS connections, although other encrypted connections are similarly contemplated. An encrypted connection includes cipher keys used to encrypt and decrypt data communicated over the encrypted connection, as well as a reference to an underlying transport protocol interface, such as a TCP interface.
As used herein, the phrase “encrypted session/connection” refers an encrypted session and/or an encrypted connection.
As used herein, the phrase “end-to-end encrypted session/connection” refers to an encrypted session and/or connection between two endpoint devices. In some instances, each endpoint device may know the identity of the other endpoint device when establishing the encrypted session/connection.
As used herein, the phrase “terminating an encrypted session” refers to being one of the two endpoints of an encrypted session. Similarly, the phrase “terminating an encrypted connection” refers to being one of the two endpoints of an encrypted connection. The endpoints of an encrypted session or connection are devices, such as a client device and a server device, between which encrypted data may be transmitted. Examples of a client device and a server device are an SSL client device and an SSL server device.
As used herein, the phrase “establishing an encrypted session” refers to participating in an encrypted session handshake protocol. The phrase “establishing an encrypted connection” refers to generating an encrypted connection associated with an encrypted session by participating in an abridged handshake protocol. In one embodiment, two devices establish the encrypted session/connection, becoming the endpoints of the encrypted session/connection. Additional devices also may optionally participate in establishing the encrypted session/connection, either in conjunction with one or both of the endpoints, or without the knowledge of one or both endpoints. One example of an encrypted session handshake protocol is an SSL handshake protocol.
As used herein, the phrase “abridged handshake protocol” refers to a negotiation between a client device and a server device used to create a new encrypted, connection that is associated with an established encrypted session. The request may be made by either the client device or the server device. The request may occur at any time after the encrypted session has been established. In one embodiment, both devices participating in the abridged handshake protocol independently generate a connection key based on the session key of the established encrypted session.
As used herein, the phrase “out-of-band” refers to sending data outside of a current encrypted session/connection, such as sending the data over a connection distinct from an end-to-end encrypted session/connection established between a client device and a server device.
As used herein, the phrase “secret data” refers to data that enables an encrypted session handshake between two devices. Secret data includes, for example, a master secret and a pre-master secret as described in RFC 2246, referenced above. Secret data may also include the random data employed to generate the pre-master secret, nonces, PKI private keys for server and/or client, and the like.
As used herein, the term “packet” refers to a group of binary digits which is switched and transmitted as a composite whole. A “network packet” is a packet that is switched and transmitted over a network from a source toward a destination. As used herein, the terms “packet header” and “header” refer to contiguous bits at the start of a packet that carry information about the payload data of the packet. For example, a header may include information regarding a format, protocol, source, destination, type, and/or sequence of payload data in a packet, and/or any other type of control information necessary for the sending, receiving and/or processing of the payload data in a packet. As used herein, “packet payload” and “payload” refer to data included within a packet, and distinct from a packet header of the packet. The payload may include data that is to be transferred from source toward a destination, and such data may be in a particular format described in the header.
Identification of header and payload within a packet may be context relevant, and related to a relevant layer of the OSI stack. For example, a packet may be analyzed by a lower-level process operating at a lower level of the OSI stack, such as the transport layer. Such a lower-level process may identify a transport-layer header and transport-layer payload within the packet, and may strip the transport-layer header from the packet in the course of receiving and analyzing the packet. The identified payload data from the packet may then be transferred to a higher-level process operating at a higher level of the OSI stack, such as at the application layer, which may identify an application layer header and application layer payload within the transferred data. Thus, both header and payload relevant to a higher level of processing (e.g. application layer) may be included in payload data relevant to a lower level of processing (e.g. transport layer).
Throughout this disclosure, when specific message types are listed, such as “CLIENT-HELLO”, it is understood that these are examples used to illustrate a type of message. These specific messages are but one embodiment, and other similar messages used to establish and/or maintain an encrypted session/connection are similarly contemplated.
In some embodiments, server-side TMD and client-side TMD may be distinguished by their relative positions within a system topology, and/or their physical locations. For example, as shown in FIG. 1, a client-side TMD may be closer to a client device physically (e.g. co-located within branch office 107 with client device(s)) and/or topologically (e.g. requiring relatively fewer network hops for traffic to reach a client device than a server device). Similarly, a server-side TMD may be closer to a server device physically (e.g. co-located within head office 120) or topologically.
Throughout this disclosure, including the claims, an untrusted TMD refers to a TMD that is not under the physical and/or administrative control of a head office. For example, a client-side TMD residing in a branch office will often be regarded as untrusted, as branch offices typically do not provide as high a level of physical or administrative security as does a head office.
Throughout this disclosure, including the claims, a login web page refers to a document viewable in a web browser capable of receiving login information and submitting that login information to a web server.
Throughout this disclosure, including the claims, a directory hierarchy refers to a hierarchical tree of directories, also known as folders, for organizing computer data files.
The claimed invention may be practiced in an environment in which a client-side TMD and a first server-side TMD are interposed between a client device and a server device, such that one or both of the TMDs have access to the session key(s) and/or connection key(s) required to decrypt encrypted data sent between the client device and the server device. What follows is a brief, non-limiting, non-exemplary description of how the first server-side TMD and the client-side TMD may reach this state. As described, the first server-side TMD is interposed between the client device and the server device. During establishment of an end-to-end encrypted session between the client device and the server device, the interposed TMD accesses secret information about the encrypted session. Such secret information includes, for example, client device and server device random data, a pre-master secret usable to determine a session key, a server certificate, a client certificate, and the like. By accessing the secret information for the end-to-end encrypted session, the first server-side TMD is able to read, intercept, augment, delete, delay, prune, compress, enhance, accelerate, transpose, or otherwise modify data sent over encrypted connections associated with the encrypted connection.
In one embodiment, once the end-to-end encrypted session has been established and the first server-side TMD has access to the session key, the first server-side TMD may transmit the session key and other secret data (including the pre-master secret, client and server random data, server certificate, and the like) to the client-side TMD, thereby enabling the client-side TMD to also decrypt encrypted data transmitted over encrypted connections associated with the encrypted session. In one embodiment, once both the client-side TMD and the first server-side TMD have access to the session keys, the client-side TMD and the server-side TMD may be used in conjunction to enhance or otherwise modify data transmitted between the client device and the server device.
Briefly described is a mechanism for establishing an encrypted session between a client device and a target server device when the client device initiates network connections through a proxy device. In one embodiment, the client device initiates an encrypted session with the proxy device. Once the encrypted session is established, the client device communicates the address of the target server device to the proxy device. Then, the proxy device sends an encrypted session renegotiation message to the client device. The client device responds to the encrypted session renegotiation message by transmitting an encrypted session handshake message to the proxy device. The proxy device forwards the encrypted session handshake message to the target server device, and continues to forward handshake messages between the client device and the target server device, enabling the client device and the target server device to establish an encrypted session.
Illustrative Operating Environment
FIG. 1 shows components of an illustrative environment 100 in which the described embodiments may be practiced. Not all the components may be required to practice the described embodiments, and variations in the arrangement and type of the components may be made without departing from the spirit or scope of the described embodiments. Environment 100 of FIG. 1 includes client devices 102-104, client-side TMD 106, branch office 107, network 108, server-side TMD 110, end-to-end encrypted session (A) and secure tunnel (B) through network 108, private keys 111(1) through 111(n), server devices 112 through 114, authentication server device 115, secret data 116, third party content provider 118, and head office 120. Server devices 112-114 (server device 113 not shown) and authentication server device 115 are collectively referred to herein as server devices 112-115.
Generally, client devices 102-104 may include virtually any computing device capable of connecting to another computing device and receiving information. Client devices 102-104 may be located within the branch office 107, but client devices 102-104 may alternatively be located outside of branch office 107. Such devices may include personal computers, multiprocessor systems, microprocessor-based or programmable consumer electronics, network devices, and the like. Client devices 102-104 may also include portable devices such as, cellular telephones, smart phones, display pagers, radio frequency (RF) devices, infrared (IR) devices, Personal Digital Assistants (PDAs), handheld computers, wearable computers, tablet computers, integrated devices combining one or more of the preceding devices, and the like. As such, client devices 102-104 may range widely in terms of capabilities and features.
Client devices 102-104 may further include one or more client applications that are configured to manage various actions. Moreover, client devices 102-104 may also include a web browser application that is configured to enable an end-user to interact with other devices and applications over network 108.
Network 108 is configured to couple network enabled devices, such as client devices 102-104, TMDs 106 and 110, server devices 112-114, authentication server device 115, and third party content provider 118, with other network enabled devices. In one embodiment, client device 102 may communicate with server device 112 through client-side TMD 106, network 108, and server-side TMD 110. Additionally or alternatively, client device 102, client-side TMD 106, server-side TMD 110, and server device 112 may all be connected directly to network 108. In one embodiment, network 108 may enable encrypted sessions, such as end-to-end encrypted session (A), between client devices 102-104 and server devices 112-115.
Network 108 is enabled to employ any form of computer readable media for communicating information from one electronic device to another. In one embodiment, network 108 may include the Internet, and may include local area networks (LANs), wide area networks (WANs), direct connections, such as through a universal serial bus (USB) port, other forms of computer-readable media, or any combination thereof. On an interconnected set of LANs, including those based on differing architectures and protocols, a router may act as a link between LANs, to enable messages to be sent from one to another. Also, communication links within LANs typically include fiber optics, twisted wire pair, or coaxial cable, while communication links between networks may utilize analog telephone lines, full or fractional dedicated digital lines including T1, T2, T3, and T4, Integrated Services Digital Networks (ISDNs), Digital Subscriber Lines (DSLs), wireless links including satellite links, or other communications links known to those skilled in the art.
Network 108 may further employ a plurality of wireless access technologies including, but not limited to, 2nd (2G), 3rd (3G), 4th (4G) generation radio access for cellular systems, Wireless-LAN, Wireless Router (WR) mesh, and the like. Access technologies such as 2G, 3G, 4G, and future access networks may enable wide area coverage for network devices, such as client devices 102-104, or the like, with various degrees of mobility. For example, network 108 may enable a radio connection through a radio network access such as Global System for Mobil communication (GSM), General Packet Radio Services (GPRS), Enhanced Data GSM Environment (EDGE), Wideband Code Division Multiple Access (WCDMA), and the like.
Furthermore, remote computers and other related electronic devices could be remotely connected to either LANs or WANs via a modem and temporary telephone link, a DSL modem, a cable modem, a fiber optic modem, an 802.11 (Wi-Fi) receiver, and the like. In essence, network 108 includes any communication method by which information may travel between one network device and another network device.
Secure tunnel (B) through network 108 includes any tunnel for communicating information between network devices. Typically, secure tunnel (B) is encrypted. As used herein, a “tunnel” or “tunneled connection” is a network mechanism that provides for the encapsulation of network packets or frames at a same or lower layer protocol of the Open Systems Interconnection (OSI) network stack. Tunneling may be employed to take packets or frames from one network system and place (e.g. encapsulate) them inside frames from another network system. Examples of tunneling protocols include, but are not limited to IP tunneling, Layer 2 Tunneling Protocol (L2TP), Layer 2 Forwarding (L2F), VPNs, IP SECurity (IPSec), Point-to-Point Tunneling Protocol (PPTP), GRE, MBone, and SSL/TLS. As shown, secure tunnel (B) is created for secure connections between client-side TMD 106 and server-side TMD 110 through network 108.
One embodiment of a network device that could be used as client-side TMD 106 or server-side TMD 110 is described in more detail below in conjunction with FIG. 2. Briefly, however, client-side TMD 106 and server-side TMD 110 each include virtually any network device that manages network traffic. Such devices include, for example, routers, proxies, firewalls, load balancers, cache devices, application accelerators, devices that perform network address translation, any combination of the preceding devices, or the like. Such devices may be implemented solely in hardware or in hardware and software. For example, such devices may include some application specific integrated circuits (ASICs) coupled to one or more microprocessors. The ASICs may be used to provide a high-speed switch fabric while the microprocessors may perform higher layer processing of packets.
In one embodiment, server-side TMD 110 is typically located within head office 120, and as such is considered to be physically secure and under the direct management of a central administrator. Accordingly, sever-side TMD 110 may also be known as a trusted TMD. Server-side TMD 110 may control, for example, the flow of data packets delivered to, or forwarded from, an array of server device devices, such as server devices 112-115. In one embodiment, messages sent between the server-side TMD 110 and the server devices 112-115 may be part of a secure channel, such end-to-end encrypted session (A) formed between one of client devices 102-104 and one of the server devices 112-115. In another embodiment, server-side TMD 110 may terminate an encrypted connection on behalf of a server device, and employ another type of encryption, such as IPSec, to deliver packets to or forward packets from the server device. Alternatively, when the server-side TMD 110 terminates the encrypted connection on behalf of a server device, delivering packets to or forwarding packets from the server device may be performed with no encryption (or “in the clear”).
In one embodiment, client-side TMD 106 typically resides in branch office 107, physically outside the control of central administrators, and therefore may be subject to physical tampering. Accordingly, client-side TMD 106 may be known as an untrusted TMD. In one embodiment, client-side TMD 106 may forward data from a source to a destination. For example, client-side TMD 106 may forward one or more encrypted session handshake messages between one of client devices 102-104 and one of server devices 112-115. Alternatively, a client-side TMD may reside in the head office 120. Alternatively, a client-side TMD may be included with a server-side TMD in a single device, enabling a single device to provide the services of both a client-side TMD and a server-side TMD, based on the types and locations of devices transmitting data through the TMD. Alternatively or additionally, a TMD may act as both a client-side TMD and a server-side TMD for a single connection. For example, a TMD may act as a client-side TMD by routing a request to a server-side TMD in another office. However, the server-side TMD may re-route the request to a server device located in geographic proximity to the “client-side” TMD. In this case, the “client-side” TMD may connect the client device to the local server device. When connecting the client device to a local server device, the TMD that began as a “client-side” TMD may perform the role of a “server-side” TMD.
As described in more detail below, client-side TMD 106 may receive secret data 116, typically from server-side TMD 110, that enables it to perform various additional actions on encrypted connection messages sent between one of client devices 102-104 and one of server devices 112-115. For example, client-side TMD 106 may be enabled to read, intercept, augment, delete, prune, compress, delay, enhance, transpose, or otherwise modify data within an encrypted connection message.
In one embodiment, server device private keys 111 may be centralized inside of the head office 120, a Federal Information. Processing Standard (FIPS) boundary, or the like. Server-side TMD 110 may be enabled to access the private keys 111, or the like, through a variety of mechanisms.
Server devices 112-115 may include any computing device capable of communicating packets to another network device. Each packet may convey a piece of information. A packet may be sent for handshaking, e.g., to establish a connection or to acknowledge receipt of data. The packet may include information such as a request, a response, or the like. Generally, packets received by server devices 112-115 may be formatted according to TCP/IP, but they could also be formatted using another protocol, such as SCTP, X.25, NetBEUI, IPX/SPX, token ring, similar IPv4/6 protocols, and the like. Moreover, the packets may be communicated between server devices 112-115, server-side TMD 110, and one of client devices 102-104 employing HTTP, HTTPS, and the like.
In one embodiment, server devices 112-115 are configured to operate as a website server. However, server devices 112-115 are not limited to web server devices, and may also operate a messaging server, a File Transfer Protocol (FTP) server, a database server, content server, and the like. Additionally, each of server devices 112-115 may be configured to perform a different operation. Thus, for example, server device 112 may be configured as a messaging server, while server device 114 is configured as a database server. Moreover, while server devices 112-115 may operate as other than a website, they may still be enabled to receive an HTTP communication.
Devices that may operate as server devices 112-115 include personal computers, desktop computers, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, server devices, and the like.
As discussed above, secret data 116 typically includes a pre-master secret and/or a master secret. Secret data 116 may also include random numbers, e.g. notices (number used once). In one embodiment, a client device and a server device may exchange nonces in their respective. HELLO messages, for use in generating the session key (also known as the master key). Additionally or alternatively, secret data 116 may include another nonce (distinct from the nonce's contained in HELLO messages) generated by the client device and digitally encrypted by the client device using the public key of the server device. In one embodiment, secret data 116 is utilized by one or more of the client device, server-side TMD 110, and the server device to generate a session key.
Third party content provider 118 may optionally be used to provide content, for example advertisements, to be inserted by server-side TMD 110 or client-side TMD 106 into an encrypted connection. However, third party content is not so limited, and may additionally include content provided by an affiliated business partner, a corporate IT department, and the like.
It is further noted that terms such as client and server may refer to functions within a device. As such, virtually any device may be configured to operate as a client, a server, or even include both a client and a server function. Furthermore, where two or more peers are employed, any one of them may be designated as a client or as a server, and be configured to confirm to the teachings of the present invention.
Illustrative Network Device Environment
FIG. 2 shows one embodiment of a network device, according to one embodiment of the invention. Network device 200 may include many more or less components than those shown. The components shown, however, are sufficient to disclose an illustrative, embodiment for practicing the invention. Network device 200 may represent, for example, server-side TMD 110 and/or client-side TMD 106 of FIG. 1.
Network device 200 includes processing unit 212, video display adapter 214, and a mass memory, all in communication with each other via bus 222. The mass memory generally includes RAM 216, ROM 232, and one or more permanent mass storage devices, such as hard disk drive 228, tape drive, CD-ROM/DVD-ROM drive 226, and/or floppy disk drive. The mass memory stores operating system 220 for controlling the operation of network device 200. Network device 200 also includes encrypted session manager 252, other applications 258, and data store 260.
As illustrated in FIG. 2, network device 200 also can communicate with the Internet, or some other communications network via network interface unit 210, which is constructed for use with various communication protocols including the TCP/IP protocol. Network interface unit 210 is sometimes known as a transceiver, transceiving device, or network interface card (NIC).
The mass memory as described above illustrates another type of computer-readable media, namely computer storage media. Computer storage media may include volatile, nonvolatile, removable, and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computing device.
The mass memory also stores program code and data. One or more applications 258 are loaded into mass memory and run on operating system 220. Examples of application programs may include email programs, routing programs, schedulers, calendars, database programs, word processing programs, HTTP programs, traffic management programs, security programs, and so forth. The mass memory may also include data store 260 for storing data employed in the process described below in conjunction with FIG. 10. For example, data store 260 may store cached login pages, nonces, public/private key pairs, session keys, and the like.
Network device 200 may further include applications that support virtually any secure connection, including TLS, TTLS, EAP, SSL, IPSec, and the like. Such applications may include, for example, and encrypted session manager 252.
In one embodiment, encrypted session manager 252 may perform encrypted session processing, including managing an encrypted session handshake, managing keys, certificates, authentication, authorization, or the like. Moreover, encrypted session manager 252 may in one embodiment establish encrypted sessions and/or connections, terminate encrypted sessions and/or connections, establish itself as a man-in-the-middle of an encrypted session and/or connection, or the like. Moreover, encrypted session manager 252 may in one securely transfer session credentials from to another TMD.
Additionally, network device 200 may include applications that support a variety of tunneling mechanisms, such as VPN, PPP, L2TP, and so forth.
Network device 200 may also include input/output interface 224 for communicating with external devices, such as a mouse, keyboard, scanner, or other input devices not shown in FIG. 2. Likewise, network device 200 may further include additional mass storage facilities such as CD-ROM/DVD-ROM drive 226 and hard disk drive 228. Hard disk drive 228 may be utilized to store, among other things, application programs, databases, certificates, public and private keys, secret data, and the like.
In one embodiment, the network device 200 includes at least one Application Specific Integrated Circuit (ASIC) chip (not shown) coupled to bus 222. The ASIC chip can include logic that performs some of the actions of network device 200. For example, in one embodiment, the ASIC chip can perform a number of packet processing functions for incoming and/or outgoing packets. In one embodiment, the ASIC chip can perform at least a portion of the logic to enable the operation of encrypted session manager 252.
In one embodiment, network device 200 can further include one or more field-programmable gate arrays (FPGA) (not shown), instead of, or in addition to, the ASIC chip. A number of functions of the network device can be performed by the ASIC chip, the FPGA, by CPU 212 with instructions stored in memory, or by any combination of the ASIC chip, FPGA, and CPU.
Illustrative Server Device Environment
FIG. 3 shows one embodiment of a server device, according to one embodiment of the invention. Server device 300 may include many more components than those shown. The components shown, however, are sufficient to disclose an illustrative embodiment for practicing the invention. Server device 300 may represent, for example, Servers 112-114 and Authentication. Server 115 of FIG. 1.
Server device 300 includes processing unit 312, video display adapter 314, and a mass memory, all in communication with each other via bus 322. The mass memory generally includes RAM 316, ROM 332, and one or more permanent mass storage devices, such as hard disk drive 328, tape drive, CD-ROM/DVD-ROM drive 326, and/or floppy disk drive. The mass memory stores operating system 320 for controlling the operation of server device 300. Any general-purpose operating system may be employed. Basic input/output system (“BIOS”) 318 is also provided for controlling the low-level operation of server device 300. As illustrated in FIG. 3, server device 300 also can communicate with the Internet, or some other communications network, via network interface unit 310, which is constructed for use with various communication protocols including the TCP/IP protocol. Network interface unit 310 is sometimes known as a transceiver, transceiving device, or network interface card (NIC).
The mass memory as described above illustrates another type of computer-readable media, namely computer storage media. Computer-readable storage media may include volatile, nonvolatile, removable, and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer readable storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other physical medium which can be used to store the desired information and which can be accessed by a computing device.
One or more applications 350 may be loaded into mass memory and run on operating system 320. Examples of application programs may include transcoders, schedulers, calendars, database programs, word processing programs, HTTP programs, customizable user interface programs, IPSec applications, encryption programs, security programs, VPN programs, web servers, account management, and so forth. Applications 350 may include encrypted, session module 360. Encrypted session module 360 may establish encrypted sessions and/or connections with other network devices, including any of the network devices discussed above. In one embodiment, encrypted session module 360 may work cooperatively with TMD 110 or TMD 106 of FIG. 1. Additionally or alternatively, encrypted session module 360 may communicate with other network devices independent of any TMD. In one embodiment, encrypted session module 360 may send a request to create a new encrypted connection that is associated with an established encrypted session.
Applications 350 may also include a variety of web services that are configured to provide content, including messages, over a network to another computing device. These web services include for example, a web server, messaging server, a File Transfer Protocol (FTP) server, a database server, a content server, or the like. These web services may provide the content including messages over the network using any of a variety of formats, including, but not limited to WAP, HDML, WML, SMGL, HTML, XML, cHTML, xHTML, or the like.
Generalized Operation
The operation of certain aspects will now be described with respect to FIGS. 4-8. FIGS. 4-7 provide logical flow diagrams illustrating certain aspects, while FIG. 8 provides a signal flow diagram. FIG. 4 illustrates a logical flow diagram generally showing one embodiment of a process for replacing an endpoint in an end-to-end encrypted connection. In one embodiment, process 400 may be implemented by server-side TMD 110.
Process 400 begins, after a start block, at block 402, by a server-side TMD interposed between a client device and a first server device. In one embodiment, the server-side TMD determines a session key associated with an end-to-end encrypted session between the client device and the first server device. The determination of the session key is described in more detail below in conjunction with FIG. 5.
At block 404, the server-side TMD detects a criterion upon which to replace the first server device as an endpoint in an end-to-end connection associated with the end-to-end encrypted session. In one embodiment this detection criteria may include detecting a type of data requested by the client device. Additionally or alternatively the criteria may include a periodic schedule, a system upgrade of the server device, a request by an administrator, or the like.
At block 406, the server-side TMD replaces the first server device with a second server device as an endpoint in the encrypted connection. In one embodiment, the server-side TMD utilizes a renegotiation of the encrypted connection to establish the second server device as an endpoint. The replacement of the server device with the second server device is described in more detail below in conjunction with FIG. 6.
At block 408, the server-side TMD may read, intercept, delay, augment, delete, prune, compress, enhance, accelerate, transpose, or otherwise modify data sent over the encrypted connection. In one embodiment, the server-side TMD may work in conjunction with a client-side TMD to further enhance data transmitted over the encrypted connection. The enhancement of data transmitted over the encrypted connection is described in more detail below in conjunction with FIG. 7. The process then terminates at a return block.
FIG. 5 illustrates a logical flow diagram generally showing one embodiment of a process for generating a session key associated with an end-to-end encrypted session. In one embodiment, process 500 may be implemented by server-side TMD 110.
Process 500 begins, after a start block, at block 502, by receiving a private key associated with the first server device. In one embodiment, the first server device may comprise one of server devices 112-115 illustrated in FIG. 1. In one embodiment, the private key of the first server device may be provided by a system administrator. Additionally or alternatively, the private key may be provided by a local domain controller, LDAP server, or the second network device itself.
At block 504, a first set of handshake messages associated with an encrypted session are intercepted. In one embodiment, the creation of the encrypted session may be initiated by a client device, such as one of client devices 102-104. In one embodiment, the first set of handshake messages includes a “CLIENT HELLO” message sent by the client device toward a first server device. After being intercepted and stored, the “CLIENT HELLO” message may be forwarded on to the first server. In one embodiment, by storing the intercepted handshake messages such as the “CLIENT HELLO” message, the server-side TMD is enabled to perform the actions described herein at any time throughout the lifetime of the corresponding encrypted session.
In response to the “CLIENT HELLO”, the first server device may send a “SERVER HELLO” message, a “SERVER CERTIFICATE” message enabling the client device to identify the first server device, a “SERVER KEY EXCHANGE” message including the first server device's public key, a “CERTIFICATE REQUEST” message requesting that the client send its certificate enabling the server device to identify the client device, and a “SERVER HELLO DONE” message, all of which may be intercepted and stored in a first set of handshake messages, and forwarded on to the client device.
In response to the “SERVER HELLO DONE” message, the client device may in one embodiment transmit a “CLIENT KEY EXCHANGE” message, including a random number (e.g. a nonce) generated by the client device and encrypted with the first server device's public key. In one embodiment, the “CLIENT KEY EXCHANGE” message may be intercepted, stored in the first set of handshake messages, and forwarded on to the first server device. Additionally or alternatively, the first set of handshake messages may include any additional messages exchanged between the client device and the first server device while establishing the encrypted session, for example a “CERTIFICATE” message containing the client device's certificate enabling the server device to identify the client device. In one embodiment, upon completion of this exchange of handshake messages, the client device and the first server device have established an end-to-end encrypted session.
Processing next continues to block 506, where secret data is extracted from the intercepted first set of handshake messages. In one embodiment, the received private key of the first server device may be used to extract secret data by decrypt the payload of the “CLIENT KEY EXCHANGE”, including a random number generated by the client device and encrypted with the public key of the first server device. Additionally or alternatively, the server-side TMD extracts the “pre-master secret.”
Processing next continues to block 508 where, in one embodiment, the decrypted random number is used in combination with one or more other random numbers exchanged between the client device and the first server device to generate a session key. In one embodiment, the session key may be a “master secret”. In one embodiment, the session key is combined with one or more other random numbers exchanged during the encrypted session handshake to generate connection keys. The connection keys may be used to encrypt and decrypt data transmitted over the encrypted connection.
In one embodiment, the client device and the first server device also independently calculate the session key based on the exchanged handshake messages. In one embodiment, the client device and the first server device also independently calculate the connection keys. In some embodiments, the server-side TMD may calculate the session key based on information in the intercepted handshake messages. Alternatively, instead of independently calculating the session key, the server-side TMD may receive the session key and/or connection key(s) from one of the first server, the client, another network device, or a system administrator.
Regardless of how the connection keys are generated or obtained, the connection keys enable encrypted data transmitted between the client device and the first server device to be decrypted. In one embodiment, the server-side TMD may decrypt the data using the connection keys, and then may augment, delete, enhance, or otherwise modify the decrypted data. In one embodiment, the server-side TMD may re-encrypt the modified data using the connection keys, and transmit the modified data to the other of the client device and the first server device. The process then terminates at a return block.
FIG. 6 illustrates a logical flow diagram generally showing one embodiment of a process for replacing an endpoint in an end-to-end encrypted connection with a second server device. In one embodiment, process 600 may be implemented by server-side TMD 110.
Process 600 begins, after a start block, at block 602, wherein one embodiment server-side TMD transmits a renegotiation request to the client device over the end-to-end encrypted connection. In one embodiment, the server-side TMD transmits the renegotiation request message in response to extracting an HTTP header sent by either the client device or the first server device, and determining the HTTP header includes a request for content located on the second server device. Server-side TMD 110 may direct a request for a resource to a particular server device based on network traffic, network topology, capacity of a server device, content requested, and a host of other traffic distribution mechanisms. Also, sever-side TMD 110 may recognize packets that are part of the same communication, flow, and/or stream and may perform special processing on such packets, such as directing them to the same server device.
In one embodiment, the server-side TMD requests or otherwise initiates renegotiation by originating and transmitting an “SSL HELLO REQUEST” to the client device over the end-to-end encrypted connection. In one embodiment, the server-side TMD utilizes encrypted connection renegotiation to replace the first server device with one or more second server devices as an endpoint of the end-to-end encrypted connection. As discussed above, the client (or server) device may in one embodiment not know that a different server (or client) device has become the endpoint. In this way, the function of the server-side TMD may be transparent to the client (or server) device.
Processing next continues to block 604, where the server-side TMD intercepts a second set of handshake messages sent in response to the “SSL HELLO REQUEST”. In one embodiment, the second set of handshake messages are encrypted using connection key and transmitted by the client device over the end-to-end encrypted connection. In one embodiment the second set of handshake messages are addressed to the first server device.
Processing next continues to block 606, where the server-side TMD decrypts the second set of handshake message using the connection key.
Processing next continues to block 608, where the server-side TMD redirects the decrypted second set of handshake messages to the second server device, thereby enabling the second server device to become an endpoint in the end-to-end encrypted connection. In one embodiment, by directing the second set of handshake messages to the second server device, the requests made by the client device over the end-to-end encrypted connection may be re-distributed by the server-side TMD to more than one server device. In one embodiment, the existing connection that had been established between the server-side TMD and the first server device is gracefully terminated by the server-side TMD. Alternatively, the existing connection between the server-side TMD and the first server device may be cached, pooled, or otherwise maintained for future use.
Additionally or alternatively, instead of establishing the second server device as an endpoint, the server-side TMD may utilize encrypted connection renegotiation to make itself an endpoint of the encrypted connection. In this embodiment, the server-side TMD may act as an encrypted connection accelerator: receiving encrypted content from the client device, decrypting the received content, forwarding the decrypted content to a server device for processing, and encrypting the server device's response. In such instances, the TMD may communicate with the first server device in the clear or establish another connection with the first server device. In another embodiment, the server-side TMD may generate encrypted content itself, rather than forwarding content from another server, such as a cached data or generated data. In another embodiment, a client-side TMD may similarly utilize encrypted connection renegotiation to make itself an endpoint of the encrypted connection, act as an encrypted connection accelerator, generate content such as cached data, and the like. Additionally or alternatively, the server-side TMD may ignore the ensuing renegotiation between the client device and the first server device, such that the server-side TMD ceases to decrypt and modify content sent over the end-to-end encrypted connection. Instead, the server-side TMD may route data sent over the renegotiated encrypted connection to the first server device as it would any other network connection. In some embodiments, a client-side TMD may also utilize encrypted connection renegotiation to ignore an ensuing renegotiation, “stepping out” of the encrypted connection.
Additionally or alternatively, the server-side TMD may terminate an encrypted connection to a client device and another encrypted connection to a server device. The server-side TMD may convert this pair of encrypted connections into a single end-to-end encrypted connection between the client device and the server device. In one embodiment the server-side TMD may perform such a conversion by utilizing encrypted connection renegotiation and handshake message forwarding between the client device and the server device. In such an embodiment, the TMD may then perform any of the operations described herein on data transmitted over the end-to-end encrypted connection.
Processing next continues to block 610, where the private key of the second server device is received by the server-side TMD. Additionally or alternatively, the server-side TMD may receive the private key of the second server device before transmitting the renegotiation request. In one embodiment, the server-side TMD receives the private key of the second server device in any of the manners discussed above with regard to receiving the private key of the first server device.
Processing next continues to block 612, where the private key of the second server device is used to extract secret data from the second set of handshake messages. In one embodiment, the server-side TMD extracts secret data from the second set of handshake messages in a manner similar to the extraction of secret data from the first set of handshake messages, as discussed above with respect to block 506.
Processing next continues to block 614, where the server-side TMD generates a second session key based at least on the secret data extracted from the second set of handshake messages. In one embodiment, the second session key is generated in a manner similar to the generation of the first session key, as discussed above with respect to block 508. In one embodiment, the generated second session key is utilized to create a second set of connection keys, defining an end-to-end encrypted connection between the client device and the second server device.
Processing next continues to block 616, where a message sent over the end-to-end encrypted connection of the re-negotiated end-to-end encrypted session is intercepted and processed by the server-side TMD. In one embodiment, the intercepted message is transmitted by the client device and is addressed to the first server device, as the client device may be unaware that the second network device is now the other endpoint of the renegotiated end-to-end encrypted session. Additionally or alternatively, the second server device may transmit a message that is intercepted and processed by server-side. TMD. In either case, server-side TMD may perform additional processing, optionally in conjunction with a client-side TMD and/or third party content provider 118, to augment, delete, prune, enhance, delay, accelerate, or otherwise modify the intercepted message. For example, an advertisement or other content may be provided by third party content provider 118, which may then be embedded in data transmitted between the second server device and the client device.
Processing next continues to block 618, where in the embodiment in which the sever-side TMD intercepts a message transmitted by the client device and addressed to the first server device, the server-side TMD redirects the intercepted message to the second server device. The process then terminates at a return block
In one embodiment, the process illustrated in FIG. 6 enables an existing end-to-end encrypted connection to be handed off to a new server device, while from the perspective of the client device, the identity of the server is unchanged. In one embodiment, renegotiation happens within the existing encrypted session tunnel.
FIG. 7 illustrates a logical flow diagram generally showing one embodiment of a process for enhancing data transmitted between a client-side TMD and a server-side TMD over the encrypted connection. In one embodiment, process 700 may be implemented by server-side TMD 110.
Process 700 begins, after a start block, at block 702, where the server-side TMD 110 transmits the second set of connection keys to a client-side TMD 106. In one embodiment, the second set of connection keys may be transmitted over the end-to-end encrypted session. Alternatively, the second set of connection keys may be transmitted over a separate encrypted session/connection, such as secure tunnel (B).
Processing next continues to block 704, where the client-side TMD 106, in one embodiment, intercepts encrypted data sent from the client device over the end-to-end encrypted connection. In one embodiment, typically when the client device is unaware that the second server device is now the endpoint of the end-to-end encrypted connection, the encrypted data sent by the client device may be addressed to, the first server device. Additionally or alternatively, when the client device is aware that the second server device 701 is now the endpoint of the end-to-end encrypted connection, the encrypted data sent by the client device may be addressed to the second server device 701.
Processing next continues to block 706, where the client-side TMD 106, in one embodiment, decrypts the intercepted data using the received second set of connection keys.
Processing next continues to block 708, where the client-side TMD 106, in one embodiment, processes the decrypted data. In one embodiment, the decrypted data may be augmented, deleted, compressed, accelerated, or otherwise modified.
Processing next continues to block 710, where the client-side TMD 106, in one embodiment, re-encrypts the processed data using the second set of connection keys, and transmits the re-encrypted processed data towards the second server device 701. In this embodiment, processing continues at block 712.
Additionally or alternatively, the client-side TMD 106 may explicitly be working in conjunction with server-side TMD 110 to transmit data between the client device and the second server device 701. In this case, the client-side TMD 106 may transmit the processed data to the server-side TMD 110 using a separate tunnel, such as secure tunnel (B) through network 108. In this embodiment, the secure tunnel (B) may utilize an encrypted connection separate and apart from the end-to-end encrypted connection. In other words, client-side TMD 106 may communicate with server-side TMD 110 using a separate set of connection keys to encrypt the processed data, or another type of encryption entirely. Upon receiving the data transmitted through secure tunnel (B), the server-side TMD 110 typically decrypts and performs further processing on the decrypted data. For example, if the client-side TMD 106 compressed the processed data to reduce transmission time, the server-side TMD 110 typically may decompress the data, and optionally perform additional processing as discussed throughout this disclosure. Then, processing continues at block 714.
In one embodiment, the client-side TMD 106 and the server-side TMD 110 may utilize two levels of encryption—the encryption used for the end-to-end encrypted connection established between the client device and the second server device 701, and additionally the encryption used by secure tunnel (B). This embodiment provides two layers of security for data transmitted over public networks, such as the internet, enhancing security of the transmitted data.
Processing next continues to block 712, where the server-side TMD 110 intercepts the processed data sent by the client-side TMD 106. In one embodiment, the server-side TMD 110 decrypts the intercepted data using the second set of connection keys.
In one embodiment, server-side TMD 110 performs further processing on the intercepted and decrypted data. In one embodiment, server-side TMD 110 augments, deletes, decompresses, or otherwise modifies the intercepted and decrypted data.
Processing next continues to block 714, where the server-side TMD 110 encrypts the further processed data using the second set of connection keys, and transmits the re-encrypted data to the second server device 701. In one embodiment, regardless of whether data was intercepted, decrypted, modified, re-encrypted, forwarded, or the like, the end-to-end encrypted connection (e.g. a connection contained in secure session (A) as shown in FIG. 1) remains intact from the perspective of the client device and the second server device 701.
Processing next continues to block 716, where the second server device 701 receives, decrypts, and processes the data transmitted by the server-side TMD 110. The process then terminates at a return block
FIG. 8 illustrates a signal flow diagram generally showing one embodiment of the process of FIGS. 4-6.
Process 800 begins at 802 by the client device transmitting a “CLIENT HELLO” handshake message as discussed above with respect to block 504. Processing continues to 804, where the server-side TMD 110 intercepts and forwards handshake messages as also discussed above with respect to block 504. Processing continues to 806, where the first server receives the “CLIENT HELLO” handshake message, among others, as discussed above with respect to block 504.
Processing continues to 808 and 812, where other handshake messages are exchanged between the client device and the first server device, as discussed above with respect to block 504.
Processing continues to 810, where secret data, such as a random number generated by the client device and encrypted by the client device with the public key of the first server device, is extracted from the other handshake messages by the server-side TMD 110 using the private key of the first server device, as discussed above with respect to block 508.
Processing optionally continues to 813, where secret data, such as the secret data generated in 810, is received by client-side TMD 106. In one embodiment, this secret data may be used to generate a connection key. Additionally or alternatively, a connection key may be received by client-side TMD 106. In one embodiment, either the secret data or the connection key may be transmitted to client-side TMD 106 by server-side TMD 110. Once client-side TMD 106 has received or generated the connection key, client-side TMD 106 is enabled to intercept and enhance encrypted data as it is transmitted over the connection.
Processing continues to 814, where a renegotiation request is transmitted by the server-side TMD 110 to the client device, as discussed above with respect to block 602.
Processing continues to 816 and 820, where in response to receiving the renegotiation request, the client device begins to exchange a second set of handshake messages, as discussed above with respect to block 412.
Processing continues to 618, where the server-side TMD 110 intercepts, decrypts, and redirects the second set of handshake messages towards the second server, as discussed above with respect to blocks 604 and 606.
Processing continues to 822, where the server-side TMD 110 transmits the second set of connection keys to the client-side TMD 106, as discussed above with regard to FIG. 7.
Processing continues to 824 and 826, where the end-to-end connection initially established between the client device and the first server device has been altered as a result of the requested renegotiation, resulting in the encrypted connection being re-established between the client device and the second server device.
Establishing an Encrypted Session Between a Client Device and a Target Server Device
FIG. 9 illustrates a functional block diagram illustrating a client device connected to a target server device through a proxy device. Not all the components may be required to practice the described embodiments, and variations in the arrangement and type of the components may be made without departing from the spirit or scope of the described embodiments. Environment 900 of FIG. 9 includes client devices 102-104, networks 108 and 952, proxy device 950, and target server device 954.
Client devices 102-104 are described above in conjunction with FIG. 1. Network 108 is similarly described above in conjunction with FIG. 1. Network 952 is also described by network 108 of FIG. 1. Target server device 954 may be implemented by network device 300 described above in conjunction with FIG. 3.
Generally, proxy device 950 may include virtually any computing device capable of connecting to another computing device and sending and/or receiving information. Such devices may include personal computers, server computers, multiprocessor systems, microprocessor-based or programmable consumer electronics, network devices, and the like. Proxy device 950 may comprise a computing device that contains a processor and a mass memory storing instructions that when executed by the processor cause proxy device 950 to perform actions described below in conjunction with FIG. 10. In one embodiment, the mass memory includes a non-transitory processor readable storage medium, RAM, a hard disk drive, a flash drive, or the like.
In one embodiment, proxy device 950 enables one of client devices 102-104 to communicate with target server device 954, particularly when the client device is unable to or is not allowed to directly communicate with target server device 954. For example, proxy device 950 may comprise a SOCKS proxy, such as a SOCKS 4 proxy, a SOCKS 5, or the like. In one embodiment, proxy device 950 facilitates creation of an end-to-end encrypted session between one of client devices 102-104 and target server device 954, as described below in conjunction with FIG. 10.
FIG. 10 illustrates a logical flow diagram showing one embodiment of a process for establishing an encrypted session between a client device and a target server device when the client device initiates network connections through a proxy device, or for any reason is unable to initiate a network connection with the target server device directly. In some embodiments, process 1000 may be implemented as an application, program, software module or the like that executes within mass memory of proxy device 950.
Process 1000 begins after a start block at block 1002, where in one embodiment a request to create an encrypted connection is received from a client device. In one embodiment, the request includes a handshake message, such as a “CLIENT HELLO” message. In another embodiment, the request does not include a “CLIENT HELLO” message, in which case the proxy device may respond to the request with a handshake message such as a “CLIENT HELLO”. In one embodiment, the request to create an encrypted connection includes a network identifier of the target server device.
At block 1004, in one embodiment, an encrypted, session is created between the client device and the proxy device. In one embodiment, the encrypted session is established as the result of an exchange of handshake messages. As discussed above, either the client device or the proxy device may initiate the encrypted session handshake by sending a “CLIENT HELLO” or equivalent message.
At block 1006, in one embodiment, the proxy device receives a request from the client device to establish an encrypted session between the client device and the target server device. In one embodiment the request includes a network-identifier of the target server device, such as an IP address, however any other mechanism of identifying a network device is similarly contemplated, including a domain name, a MAC address, and the like. In another embodiment, the identity of the target server device is included in the request received from the client device in block 1002, before the encrypted session is established between the client device and the proxy device.
At block 1008; in one embodiment, the proxy device creates an unencrypted network connection to the target server device. In one embodiment, the unencrypted connection comprises a TCP connection, however any type of connection using any protocol is similarly contemplated. In another embodiment, the proxy device re-uses an existing unencrypted network connection to the server device.
At block 1010, in one embodiment, the proxy device initiates an encrypted session renegotiation on the existing encrypted session between the client device and the proxy device. In one embodiment, renegotiation is initiated by sending an “SSL HELLO REQUEST” message to the client device.
At block 1012, in one embodiment, the client device responds to the encrypted Session renegotiation by initiating a new encrypted session. In one embodiment, a new encrypted session is initiated by the client device transmitting a “CLIENT HELLO” message to the proxy device, although other similar messages are similarly contemplated. In one embodiment, the proxy device forwards the received “CLIENT HELLO” message to the target server device over the unencrypted network connection discussed in block 1008. In this way, a handshake is initiated between the client device and the target server device that will result in the establishment of an encrypted session between the client device and the target server device.
In another embodiment, the proxy device may not forward the received handshake message over the unencrypted network connection to the target server device, but instead re-use an existing encrypted session that terminates at the target server device. Specifically, the proxy device may transmit the handshake message received from the client device to the target server device over the target server device's existing encrypted session, such that by completing the handshake protocol, the target server device creates a new encrypted context for the existing encrypted connection rather than creating a new encrypted session. In this way, the client device may initiate a renegotiation that causes the existing encrypted connection between the client device and the proxy device and an existing encrypted connection that terminates with the target server device to become a new encrypted connection between the client device and the target server device.
Once the encrypted session between the client device and the target server device is established (or repurposed, if an existing encrypted connection is re-used), the proxy device continues forwarding packets between the client device and the target server device. In one embodiment, the proxy device is not able to decrypt the content transmitted over the encrypted session between the client device and the target server device. In another embodiment, the proxy device has access to the target server device's private key, with which the proxy device may determine the session key and connection keys used to transmit data over the encrypted connection, as discussed herein in conjunction with FIGS. 5 and 6. In this embodiment, the proxy device may inspect, modify, or otherwise affect the data transmitted between the client device and the target server device.
In one embodiment, the client device continues to address packets sent over the new encrypted session to the proxy device, in which case the proxy device forwards these packets to the target server device by over-writing the destination network addresses and ports with the network address and port of the target server device. In another embodiment, the client device addresses packets sent over the new encrypted session to the target server device.
In one embodiment, the target server device may reply to a request transmitted over the encrypted session that the requested resource is not found, along with a network identification of a second server device which may have the resource. In another embodiment, the target server device may respond to any request for any reason with an indication that one or more different server devices should instead process the request. In this embodiment, the proxy device may receive the target server device's reply, and replace the target server device as one endpoint of the encrypted session with another server device, before re-transmitting the request, as discussed herein in conjunction with FIG. 6.
In one embodiment, if the client device requests that the encrypted session end, or if the client device closes the encrypted session, the proxy device may opt to keep the encrypted session open at the target server device. In one embodiment, this encrypted session may be re-used on a subsequent request from this client device or any other client device. Process 1000 then flows to a return block.
It will be understood that figures, and combinations of steps in the flowchart-like illustrations, can be implemented by computer program instructions. These program instructions may be provided to a processor to produce a machine, such that the instructions, which execute on the processor, create means for implementing the actions specified in the flowchart block or blocks. The computer program instructions may be executed by a processor to cause a series of operational steps to be performed by the processor to produce a computer implemented process such that the instructions, which execute on the processor to provide steps for implementing the actions specified in the flowchart block or blocks. These program instructions may be stored on a computer readable medium or machine readable medium, such as a computer readable storage medium.
Accordingly, the illustrations support combinations of means for performing the specified actions, combinations of steps for performing the specified actions and program instruction means for performing the specified actions. It will also be understood that each block of the flowchart illustration, and combinations of blocks in the flowchart illustration, can be implemented by modules such as special purpose hardware-based systems which perform the specified actions or steps, or combinations of special purpose hardware and computer instructions.
The above specification, examples, and data provide a complete description of the manufacture and use of the composition of the described embodiments. Since many embodiments can be made without departing from the spirit and scope of this description, the embodiments reside in the claims hereinafter appended.

## Claims

1. A proxy device interposed between a client device and a plurality of target server devices, comprising:
a transceiver to send and receive data over a network; and
a processor that is operative to perform actions comprising:
establishing a first encrypted session with the client device;
receiving a network identifier of a first target server device;
establishing an unencrypted network connection with the first target server device, wherein the proxy device enables communication in the first encrypted session between the client device and the first target server device:
sending an encrypted session renegotiation message to the client device in response to determining header information extracted from session communication between the client device and the first target server device includes criteria for a change from the first target server device,
decrypting and redirecting a handshake message received from the client device to a second target server device, wherein the handshake message was sent by the client device in response to the encrypted session renegotiation message;
replacing the first target server device in the first encrypted session for communication with the client device with a second target server device.

2. The proxy device of claim 1, wherein the actions further comprise forwarding additional handshake messages sent by the client device to the target server device and from the target server device to the client device, to establish a second encrypted session between the client device and the second target server device.

3. The proxy device of claim 1, wherein the actions further comprise:
forwarding additional handshake messages sent by the client device to the target server device and from the target server device to the client device, to establish a second encrypted session between the client device and the target server device; and
forwarding messages sent over the second encrypted session from the client device to the second target server device and from the second target server device to the client device.

4. The proxy device of claim 1, wherein the proxy device comprises a SOCKS proxy device.

5. The proxy device of claim 1, wherein the proxy device comprises an HTTP proxy device, and wherein the first encrypted session is created in response to receiving an HTTP request from the client device.

6. The proxy device of claim 1, wherein the first encrypted session is created in response to a request received from the client device.

7. The proxy device of claim 1, wherein the encrypted session renegotiation message includes an “SSL HELLO REQUEST” message and the handshake message received from the client device includes a “CLIENT HELLO” message.

8. A system comprising: a client device: a first target server device: a second target server device: and
a proxy device interposed between the client device and the first and the second target devices, wherein the proxy device is configured to perform actions including:
establishing a first encrypted session with the client device, wherein the prow device enables communication in the first encrypted session between the client device and the first target server device: receiving a network identifier of the first target server device;
establishing an unencrypted network connection with the first target server device;
sending an encrypted session renegotiation message to the client device in response to determining header information extracted from session communication between the client device and the first target server device includes criteria for a change from the first target server device,
decrypting and redirecting a handshake message received from the client device to a second target server device, wherein the handshake message was sent by the client device in response to the encrypted session renegotiation message;
replacing the first target server device in the first encrypted session for communication with the client device with a second target server device.

9. The system of claim 8, wherein the actions further comprise:
forwarding, additional handshake messages sent by the client device to the second target server device and from the second target server device to the client device, to establish a second encrypted session between the client device and the second target server device; and
forwarding messages sent over the second encrypted session from the client device to the second target server device and from the second target server device to the client device.

10. The system of claim 8, wherein the proxy device comprises a SOCKS proxy device.

11. The system of claim 8, wherein the proxy device comprises an HTTP proxy device, and wherein the first encrypted session is created in response to receiving an HTTP request from the client device.

12. The system of claim 8, wherein the first encrypted session is created in response to a request received from the client device.

13. The system of claim 8, wherein the encrypted session renegotiation message includes an “SSL HELLO REQUEST” message and the handshake message received from the client device includes a “CLIENT HELLO” message.

14. A non-transitory processor readable storage medium storing processor readable instructions that when executed by a processor perform actions comprising: establishing a first encrypted session with a client device: receiving a network identifier of a first target server device;
establishing a first unencrypted network connection with the first target server device wherein the prow device enables communication in the first encrypted session between the client device and the first target server device:
sending an encrypted session renegotiation message to the client device
in response to determining header information extracted from session communication between the client device and the first target server device includes criteria for a change from the first target server device,
decrypting and redirecting a handshake message received from the client device to a second target server device, wherein the handshake message was sent by the client device in response to the encrypted session renegotiation message;
replacing the first target server device in the first encrypted session for communication with the client device with a second target server device.

15. The processor readable storage medium of claim 14, wherein the actions further comprise forwarding additional handshake messages sent by the client device to the second target server device and from the second target server device to the client device, to establish a second encrypted session between the client device and the second target server device.

16. The processor readable storage medium of claim 14, wherein the actions further comprise:
forwarding additional handshake messages sent by the client device to the second target server device and from the second target server device to the client device, to establish a second encrypted session between the client device and the second target server device; and
forwarding messages sent over the second encrypted session from the client device to the second target server device and from the target server device to the client device.

17. The processor readable storage medium of claim 14, wherein the proxy device comprises a SOCKS proxy device.

18. The processor readable storage medium of claim 14 wherein the proxy device comprises an HTTP proxy device, and wherein the first encrypted session is created in response to receiving an HTTP request from the client device.

19. The processor readable storage medium of claim 14, wherein the first encrypted session is created in response to a request received from the client device.

20. The system of claim 8,
wherein the proxy device is further configured to establish the first encrypted session between the client device and the first target server device such that the first target server device is an endpoint of the first encrypted session, and wherein the proxy device is configured to employ forwarding the handshake message received from the client device to the second target service device to replace the first target server device with the second target service device as the endpoint of the first encrypted session.

21. the proxy device of claim 1, wherein the a criteria for a change from the first target server device comprises type of data requested by the client device, a periodic schedule, a system upgrade of the server device, network traffic type, network topology, capacity of a server device, and/or a request by an administrator.

22. the system of claim 8, the a criteria for a change from the first target server device comprises type of data requested by the client device, a periodic schedule, a system upgrade of the server device, network traffic type, network topology, capacity of a server device, and/or a request by an administrator.

23. the non-transitory processor readable storage medium of claim 14, the a criteria for a change from the first target server device comprises type of data requested by the client device, a periodic schedule, a system upgrade of the server device, network traffic type, network topology, capacity of a server device, and/or a request by an administrator.