Patent Publication Number: US-2022231864-A1

Title: Encrypted traffic inspection in a cloud-based security system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present disclosure is a continuation of U.S. patent application Ser. No. 16/863,475, filed Apr. 30, 2020, the contents of which are incorporated by reference in their entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to networking and computing. More particularly, the present disclosure relates to systems and methods for encrypted traffic inspection in a cloud-based security system, such as Secure Sockets Layer (SSL), Transport Layer Security (TLS), Datagram TLS (DTLS), Hypertext Transfer Protocol Secure (HTTPS), and the like. 
     BACKGROUND OF THE DISCLOSURE 
     There has been significant growth in encrypted traffic on the Internet. For example, protocols such as SSL, TLS, DTLS, HTTPS, etc. are used to provide privacy and data integrity. According to some forecasts, 70% or more of all Web traffic now uses SSL, and these numbers are growing. Encrypted traffic presents a security hole, i.e., a blind spot. Enterprises conventionally have deployed appliances and other devices at the network perimeter to perform security functions. In terms of encrypted traffic, the appliances need to break the encryption in order to monitor the traffic. This is resource intense, and conventional appliances simply do not scale. As such, most enterprises simply forego the inspection of encrypted traffic. Other studies have shown that the majority of malware today is hidden in encrypted traffic. Also, encrypted traffic presents a problem in terms of Data Loss Prevention (DLP) because sensitive data is typically concealed in SSL/TLS traffic, which is difficult and expensive to inspect (in terms of cost, processing capability, and latency). Without visibility and control, organizations are at an increased risk of data loss, due either to unintentional or malicious reasons. The conventional appliance and network perimeter security approach is breaking down with the mobility of users, the processing capability of user devices, etc. As such, security is moving to the cloud, namely as a service offered through a cloud-based system. 
     There is a need for techniques for inspecting encrypted traffic in a cloud-based security system. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     The present disclosure relates to systems and methods for encrypted traffic inspection in a cloud-based security system, such as Secure Sockets Layer (SSL), Transport Layer Security (TLS), Hypertext Transfer Protocol Secure (HTTPS), and the like. The cloud-based security system is configured to monitor users in an inline manner as a proxy or Secure Web or Internet Gateway, including monitoring encrypted traffic, e.g., Secure Sockets Layer (SSL)/Transport Layer Security (TLS) traffic. Based on this proxy by the design aspect of the cloud-based security system, the cloud-based security system can provide inspection on encrypted traffic, such as SSL, TLS, DTLS, HTTPS, etc., without the inspection limitations of appliances. Various approaches are contemplated, including a snooping approach, a Man-in-the-Middle (MitM) proxy approach, and the like. The snooping approach includes snooping session keys and utilizing the snooped keys to non-intrusively monitor the encrypted traffic. Advantageously, this approach does not terminate the encrypted traffic. The MitM proxy approach has a cloud node that sits as a proxy between a user device and an endpoint where the proxy breaks the encrypted traffic in the middle. With the inspection of encrypted traffic, the cloud-based security system can perform a full suite of security functions on the traffic. 
     The systems and methods include monitoring traffic between a user device and the Internet; detecting and monitoring a handshake between the user device and an endpoint for determining keys associated with encryption between the user device and the endpoint; monitoring encrypted traffic between the user device and the endpoint subsequent to the handshake based on the keys; and performing one or more security functions on the encrypted traffic based on the monitoring. The node can be part of a cloud-based security system and configured inline between the user device and the endpoint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like system components/method steps, as appropriate, and in which: 
         FIG. 1  is a network diagram of a cloud-based system offering security as a service; 
         FIG. 2  is a network diagram of an example implementation of the cloud-based system; 
         FIG. 3  is a block diagram of a server that may be used in the cloud-based system of  FIGS. 1 and 2  or the like; 
         FIG. 4  is a block diagram of a user device that may be used with the cloud-based system of  FIGS. 1 and 2  or the like; 
         FIG. 5  is a network diagram of the cloud-based system illustrating an application on user devices with users configured to operate through the cloud-based system; 
         FIG. 6  is a flow diagram illustrating an example handshake for HTTPS to describe a secure, encrypted tunnel between a client (e.g., the user device of  FIG. 4 ) and a server (e.g., the server of  FIG. 3 ); 
         FIG. 7  is a screenshot of packet capture showing SSL packets as they are exchanged between a client and a server; 
         FIG. 8  is a flow diagram illustrating an embodiment of SSL inspection with the cloud-based system as a proxy; 
         FIG. 9  is a flow diagram of details of an SSL handshake process between an SSL client and an SSL server; 
         FIG. 10  is a flow diagram of a process performing SSL interception through an interception proxy in the handshake process; 
         FIG. 11  is a network diagram of a network with an enforcement node operating as an interception proxy to perform; 
         FIG. 12  is a network diagram of a network with the enforcement node operating as a snooping proxy to perform SSL interception without breaking the tunnel as with the interception proxy; and 
         FIG. 13  is a flowchart of a process for SSL (or other type of encrypted traffic) inspection by snooping, such as via a node operating as the snooping proxy. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Again, the present disclosure relates to systems and methods for encrypted traffic inspection in a cloud-based security system, such as Secure Sockets Layer (SSL), Transport Layer Security (TLS), Hypertext Transfer Protocol Secure (HTTPS), Datagram TLS (DTLS), and the like. The cloud-based security system is configured to monitor users in an inline manner as a proxy or Secure Web or Internet Gateway, including monitoring encrypted traffic, e.g., Secure Sockets Layer (SSL)/Transport Layer Security (TLS) traffic. Based on this proxy by the design aspect of the cloud-based security system, the cloud-based security system can provide inspection on encrypted traffic, such as SSL, TLS, DTLS, HTTPS, etc., without the inspection limitations of appliances. Various approaches are contemplated, including a snooping approach, a Man-in-the-Middle (MitM) proxy approach, and the like. The snooping approach includes snooping session keys and utilizing the snooped keys to non-intrusively monitor the encrypted traffic. Advantageously, this approach does not terminate the encrypted traffic. The MitM proxy approach has a cloud node that sits as a proxy between a user device and an endpoint where the proxy breaks the encrypted traffic in the middle. With the inspection of encrypted traffic, the cloud-based security system can perform a full suite of security functions on the traffic. 
     Example Cloud-Based System Architecture 
       FIG. 1  is a network diagram of a cloud-based system  100  offering security as a service. Specifically, the cloud-based system  100  can offer a Secure Internet and Web Gateway as a service to various users  102 , as well as other cloud services. In this manner, the cloud-based system  100  is located between the users  102  and the Internet as well as any cloud services  106  (or applications) accessed by the users  102 . As such, the cloud-based system  100  provides inline monitoring inspecting traffic between the users  102 , the Internet  104 , and the cloud services  106 , including encrypted traffic such as SSL, TLS, DTLS, HTTPS, etc. traffic. Note, various functions described herein are attributed as being performed by the cloud-based system  100 . Those skilled in the art will recognize such functions can also be viewed as being performed via a cloud service offered by the cloud-based system  100 , as well as being implemented at one or more nodes in the cloud-based system  100 . 
     The cloud-based system  100  can offer access control, threat prevention, data protection, etc. The access control can include a cloud-based firewall, cloud-based intrusion detection, Uniform Resource Locator (URL) filtering, bandwidth control, Domain Name System (DNS) filtering, etc. The threat prevention can include cloud-based intrusion prevention, protection against advanced threats (malware, spam, Cross-Site Scripting (XSS), phishing, etc.), cloud-based sandbox, antivirus, DNS security, etc. The data protection can include Data Loss Prevention (DLP), cloud application security such as via Cloud Access Security Broker (CASB), file type control, etc. 
     The cloud-based firewall can provide Deep Packet Inspection (DPI) and access controls across various ports and protocols as well as being application and user aware. The URL filtering can block, allow, or limit website access based on policy for a user, group of users, or entire organization, including specific destinations or categories of URLs (e.g., gambling, social media, etc.). The bandwidth control can enforce bandwidth policies and prioritize critical applications such as relative to recreational traffic. The DNS filtering can control and block DNS requests against known and malicious destinations. 
     The cloud-based intrusion prevention and advanced threat protection can deliver full threat protection against malicious content such as browser exploits, scripts, identified botnets and malware callbacks, etc. The cloud-based sandbox can block zero-day exploits (just identified) by analyzing unknown files for malicious behavior. Advantageously, the cloud-based system  100  is multi-tenant and can service a large volume of the users  102 . As such, newly discovered threats can be promulgated throughout the cloud-based system  100  for all tenants practically instantaneously. The antivirus protection can include antivirus, antispyware, antimalware, etc. protection for the users  102 , using signatures sourced and constantly updated. The DNS security can identify and route command-and-control connections to threat detection engines for full content inspection. 
     The DLP can use standard and/or custom dictionaries to continuously monitor the users  102 , including compressed and/or SSL-encrypted traffic. Again, being in a cloud implementation, the cloud-based system  100  can scale this monitoring with near-zero latency on the users  102 . The cloud application security can include CASB functionality to discover and control user access to known and unknown cloud services  106 . The file type controls enable true file type control by the user, location, destination, etc. to determine which files are allowed or not. 
     For illustration purposes, the users  102  of the cloud-based system  100  can include a mobile device  110 , a headquarters (HQ)  112  which can include or connect to a data center (DC)  114 , Internet of Things (loT) devices  116 , a branch office  118 , etc., and each includes one or more user devices (an example user device  300  is illustrated in  FIG. 3 ). The devices  110 ,  116 , and the locations  112 ,  114 ,  118  are shown for illustrative purposes, and those skilled in the art will recognize there are various access scenarios and other users  102  for the cloud-based system  100 , all of which are contemplated herein. The users  102  can be associated with a tenant, which may include an enterprise, a corporation, an organization, etc. That is, a tenant is a group of users who share a common access with specific privileges to the cloud-based system  100 , a cloud service, etc. In an embodiment, the headquarters  112  can include an enterprise&#39;s network with resources in the data center  114 . The mobile device  110  can be a so-called road warrior, i.e., users that are off-site, on-the-road, etc. Further, the cloud-based system  100  can be multi-tenant, with each tenant having its own users  102  and configuration, policy, rules, etc. One advantage of the multi-tenancy and a large volume of users is the zero-day/zero-hour protection in that a new vulnerability can be detected and then instantly remediated across the entire cloud-based system  100 . The same applies to policy, rule, configuration, etc. changes—they are instantly remediated across the entire cloud-based system  100 . As well, new features in the cloud-based system  100  can also be rolled up simultaneously across the user base, as opposed to selective and time-consuming upgrades on every device at the locations  112 ,  114 ,  118 , and the devices  110 ,  116 . 
     Logically, the cloud-based system  100  can be viewed as an overlay network between users (at the locations  112 ,  114 ,  118 , and the devices  110 ,  106 ) and the Internet  104  and the cloud services  106 . Previously, the IT deployment model included enterprise resources and applications stored within the data center  114  (i.e., physical devices) behind a firewall (perimeter), accessible by employees, partners, contractors, etc. on-site or remote via Virtual Private Networks (VPNs), etc. The cloud-based system  100  is replacing the conventional deployment model. The cloud-based system  100  can be used to implement these services in the cloud without requiring the physical devices and management thereof by enterprise IT administrators. As an ever-present overlay network, the cloud-based system  100  can provide the same functions as the physical devices and/or appliances regardless of geography or location of the users  102 , as well as independent of platform, operating system, network access technique, network access provider, etc. 
     There are various techniques to forward traffic between the users  102  at the locations  112 ,  114 ,  118 , and via the devices  110 ,  116 , and the cloud-based system  100 . Typically, the locations  112 ,  114 ,  118  can use tunneling where all traffic is forward through the cloud-based system  100 . For example, various tunneling protocols are contemplated, such as Generic Routing Encapsulation (GRE), Layer Two Tunneling Protocol (L2TP), Internet Protocol (IP) Security (IPsec), customized tunneling protocols, etc. The devices  110 ,  116 , when not at one of the locations  112 ,  114 ,  118  can use a local application that forwards traffic, a proxy such as via a Proxy Auto-Config (PAC) file, and the like. A key aspect of the cloud-based system  100  is all traffic between the users  102  and the Internet  104  or the cloud services  106  is via the cloud-based system  100 . As such, the cloud-based system  100  has visibility to enable various functions, all of which are performed off the user device in the cloud. 
     The cloud-based system  100  can also include a management system  120  for tenant access to provide global policy and configuration as well as real-time analytics. This enables IT administrators to have a unified view of user activity, threat intelligence, application usage, etc. For example, IT administrators can drill-down to a per-user level to understand events and correlate threats, to identify compromised devices, to have application visibility, and the like. The cloud-based system  100  can further include connectivity to an Identity Provider (IDP)  122  for authentication of the users  102  and to a Security Information and Event Management (SIEM) system  124  for event logging. The system  124  can provide alert and activity logs on a per-user  102  basis. 
       FIG. 2  is a network diagram of an example implementation of the cloud-based system  100 . In an embodiment, the cloud-based system  100  includes a plurality of enforcement nodes (EN)  150 , labeled as enforcement nodes  150 - 1 ,  150 - 2 ,  150 -N, interconnected to one another and interconnected to a central authority (CA)  152 . The nodes  150 ,  152 , while described as nodes, can include one or more servers, including physical servers, virtual machines (VM) executed on physical hardware, etc. An example of a server is illustrated in  FIG. 2 . The cloud-based system  100  further includes a log router  154  that connects to a storage cluster  156  for supporting log maintenance from the enforcement nodes  150 . The central authority  152  provide centralized policy, real-time threat updates, etc. and coordinates the distribution of this data between the enforcement nodes  150 . The enforcement nodes  150  provide an onramp to the users  102  and are configured to execute policy, based on the central authority  152 , for each user  102 . The enforcement nodes  150  can be geographically distributed, and the policy for each user  102  follows that user  102  as he or she connects to the nearest (or other criteria) enforcement node  150 . 
     The enforcement nodes  150  are full-featured secure internet gateways that provide integrated internet security. They inspect all web traffic bi-directionally for malware and enforce security, compliance, and firewall policies, as described herein. In an embodiment, each enforcement node  150  has two main modules for inspecting traffic and applying policies: a web module and a firewall module. The enforcement nodes  150  are deployed around the world and can handle hundreds of thousands of concurrent users with millions of concurrent sessions. Because of this, regardless of where the users  102  are, they can access the Internet  104  from any device, and the enforcement nodes  150  protect the traffic and apply corporate policies. The enforcement nodes  150  can implement various inspection engines therein, and optionally, send sandboxing to another system. The enforcement nodes  150  include significant fault tolerance capabilities, such as deployment in active-active mode to ensure availability and redundancy as well as continuous monitoring. 
     In an embodiment, customer traffic is not passed to any other component within the cloud-based system  100 , and the enforcement nodes  150  can be configured to never store any data to disk. Packet data is held in memory for inspection and then, based on policy, is either forwarded or dropped. Log data generated for every transaction is compressed, tokenized, and exported over secure TLS connections to the log routers  154  that direct the logs to the storage cluster  156 , hosted in the appropriate geographical region, for each organization. 
     The central authority  152  hosts all customer (tenant) policy and configuration settings. It monitors the cloud and provides a central location for software and database updates and threat intelligence. Given the multi-tenant architecture, the central authority  152  is redundant and backed up in multiple different data centers. The enforcement nodes  150  establish persistent connections to the central authority  152  in order to download all policy configurations. When a new user connects to an enforcement node  150 , a policy request is sent to the central authority  152  through this connection. The central authority  152  then calculates the policies that apply to that user  102  and sends the policy to the enforcement node  150  as a highly compressed bitmap. 
     Once downloaded, a tenant&#39;s policy is cached until a policy change is made in the management system  120 . When this happens, all of the cached policies are purged, and the enforcement nodes  150  request the new policy when the user  102  next makes a request. In an embodiment, the enforcement node  150  exchange “heartbeats” periodically, so all enforcement nodes  150  are informed when there is a policy change. Any enforcement node  150  can then pull the change in policy when it sees a new request. 
     The cloud-based system  100  can be a private cloud, a public cloud, a combination of a private cloud and a public cloud (hybrid cloud), or the like. Cloud computing systems and methods abstract away physical servers, storage, networking, etc., and instead offer these as on-demand and elastic resources. The National Institute of Standards and Technology (NIST) provides a concise and specific definition which states cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. Cloud computing differs from the classic client-server model by providing applications from a server that are executed and managed by a client&#39;s web browser or the like, with no installed client version of an application required. Centralization gives cloud service providers complete control over the versions of the browser-based and other applications provided to clients, which removes the need for version upgrades or license management on individual client computing devices. The phrase “Software as a Service” (SaaS) is sometimes used to describe application programs offered through cloud computing. A common shorthand for a provided cloud computing service (or even an aggregation of all existing cloud services) is “the cloud.” The cloud-based system  100  is illustrated herein as an example embodiment of a cloud-based system, and other implementations are also contemplated. 
     As described herein, the terms cloud services and cloud applications may be used interchangeably. The cloud service  106  is any service made available to users on-demand via the Internet, as opposed to being provided from a company&#39;s on-premises servers. A cloud application, or cloud app, is a software program where cloud-based and local components work together. The cloud-based system  100  can be utilized to provide example cloud services, including Zscaler Internet Access (ZIA), Zscaler Private Access (ZPA), and Zscaler Digital Experience (ZDX), all from Zscaler, Inc. (the assignee and applicant of the present application). The ZIA service can provide the access control, threat prevention, and data protection described above with reference to the cloud-based system  100 . ZPA can include access control, microservice segmentation, etc. The ZDX service can provide monitoring of user experience, e.g., Quality of Experience (QoE), Quality of Service (QoS), etc., in a manner that can gain insights based on continuous, inline monitoring. For example, the ZIA service can provide a user with Internet Access, and the ZPA service can provide a user with access to enterprise resources in lieu of traditional Virtual Private Networks (VPNs), namely ZPA provides Zero Trust Network Access (ZTNA). Those of ordinary skill in the art will recognize various other types of cloud services  106  are also contemplated. Also, other types of cloud architectures are also contemplated, with the cloud-based system  100  presented for illustration purposes. 
     Example Server Architecture 
       FIG. 3  is a block diagram of a server  200 , which may be used in the cloud-based system  100 , in other systems, or standalone. For example, the enforcement nodes  150  and the central authority  152  may be formed as one or more of the servers  200 . The server  200  may be a digital computer that, in terms of hardware architecture, generally includes a processor  202 , input/output (I/O) interfaces  204 , a network interface  206 , a data store  208 , and memory  210 . It should be appreciated by those of ordinary skill in the art that  FIG. 3  depicts the server  200  in an oversimplified manner, and a practical embodiment may include additional components and suitably configured processing logic to support known or conventional operating features that are not described in detail herein. The components ( 202 ,  204 ,  206 ,  208 , and  210 ) are communicatively coupled via a local interface  212 . The local interface  212  may be, for example, but not limited to, one or more buses or other wired or wireless connections, as is known in the art. The local interface  212  may have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers, among many others, to enable communications. Further, the local interface  212  may include address, control, and/or data connections to enable appropriate communications among the aforementioned components. 
     The processor  202  is a hardware device for executing software instructions. The processor  202  may be any custom made or commercially available processor, a Central Processing Unit (CPU), an auxiliary processor among several processors associated with the server  200 , a semiconductor-based microprocessor (in the form of a microchip or chipset), or generally any device for executing software instructions. When the server  200  is in operation, the processor  202  is configured to execute software stored within the memory  210 , to communicate data to and from the memory  210 , and to generally control operations of the server  200  pursuant to the software instructions. The I/O interfaces  204  may be used to receive user input from and/or for providing system output to one or more devices or components. 
     The network interface  206  may be used to enable the server  200  to communicate on a network, such as the Internet  104 . The network interface  206  may include, for example, an Ethernet card or adapter or a Wireless Local Area Network (WLAN) card or adapter. The network interface  206  may include address, control, and/or data connections to enable appropriate communications on the network. A data store  208  may be used to store data. The data store  208  may include any of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, and the like)), nonvolatile memory elements (e.g., ROM, hard drive, tape, CDROM, and the like), and combinations thereof. Moreover, the data store  208  may incorporate electronic, magnetic, optical, and/or other types of storage media. In one example, the data store  208  may be located internal to the server  200 , such as, for example, an internal hard drive connected to the local interface  212  in the server  200 . Additionally, in another embodiment, the data store  208  may be located external to the server  200  such as, for example, an external hard drive connected to the I/O interfaces  204  (e.g., SCSI or USB connection). In a further embodiment, the data store  208  may be connected to the server  200  through a network, such as, for example, a network-attached file server. 
     The memory  210  may include any of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), nonvolatile memory elements (e.g., ROM, hard drive, tape, CDROM, etc.), and combinations thereof. Moreover, the memory  210  may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory  210  may have a distributed architecture, where various components are situated remotely from one another but can be accessed by the processor  202 . The software in memory  210  may include one or more software programs, each of which includes an ordered listing of executable instructions for implementing logical functions. The software in the memory  210  includes a suitable Operating System (O/S)  214  and one or more programs  216 . The operating system  214  essentially controls the execution of other computer programs, such as the one or more programs  216 , and provides scheduling, input-output control, file and data management, memory management, and communication control and related services. The one or more programs  216  may be configured to implement the various processes, algorithms, methods, techniques, etc. described herein. 
     Example User Device Architecture 
       FIG. 4  is a block diagram of a user device  300 , which may be used with the cloud-based system  100  or the like. Specifically, the user device  300  can form a device used by one of the users  102 , and this may include common devices such as laptops, smartphones, tablets, netbooks, personal digital assistants, MP3 players, cell phones, e-book readers, IoT devices, servers, desktops, printers, televisions, streaming media devices, and the like. The user device  300  can be a digital device that, in terms of hardware architecture, generally includes a processor  302 , I/O interfaces  304 , a network interface  306 , a data store  308 , and memory  310 . It should be appreciated by those of ordinary skill in the art that  FIG. 4  depicts the user device  300  in an oversimplified manner, and a practical embodiment may include additional components and suitably configured processing logic to support known or conventional operating features that are not described in detail herein. The components ( 302 ,  304 ,  306 ,  308 , and  302 ) are communicatively coupled via a local interface  312 . The local interface  312  can be, for example, but not limited to, one or more buses or other wired or wireless connections, as is known in the art. The local interface  312  can have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers, among many others, to enable communications. Further, the local interface  312  may include address, control, and/or data connections to enable appropriate communications among the aforementioned components. 
     The processor  302  is a hardware device for executing software instructions. The processor  302  can be any custom made or commercially available processor, a CPU, an auxiliary processor among several processors associated with the user device  300 , a semiconductor-based microprocessor (in the form of a microchip or chipset), or generally any device for executing software instructions. When the user device  300  is in operation, the processor  302  is configured to execute software stored within the memory  310 , to communicate data to and from the memory  310 , and to generally control operations of the user device  300  pursuant to the software instructions. In an embodiment, the processor  302  may include a mobile optimized processor such as optimized for power consumption and mobile applications. The I/O interfaces  304  can be used to receive user input from and/or for providing system output. User input can be provided via, for example, a keypad, a touch screen, a scroll ball, a scroll bar, buttons, a barcode scanner, and the like. System output can be provided via a display device such as a Liquid Crystal Display (LCD), touch screen, and the like. 
     The network interface  306  enables wireless communication to an external access device or network. Any number of suitable wireless data communication protocols, techniques, or methodologies can be supported by the network interface  306 , including any protocols for wireless communication. The data store  308  may be used to store data. The data store  308  may include any of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, and the like)), nonvolatile memory elements (e.g., ROM, hard drive, tape, CDROM, and the like), and combinations thereof. Moreover, the data store  308  may incorporate electronic, magnetic, optical, and/or other types of storage media. 
     The memory  310  may include any of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), nonvolatile memory elements (e.g., ROM, hard drive, etc.), and combinations thereof. Moreover, the memory  310  may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory  310  may have a distributed architecture, where various components are situated remotely from one another, but can be accessed by the processor  302 . The software in memory  310  can include one or more software programs, each of which includes an ordered listing of executable instructions for implementing logical functions. In the example of  FIG. 3 , the software in the memory  310  includes a suitable operating system  314  and programs  316 . The operating system  314  essentially controls the execution of other computer programs and provides scheduling, input-output control, file and data management, memory management, and communication control and related services. The programs  316  may include various applications, add-ons, etc. configured to provide end-user functionality with the user device  300 . For example, example programs  316  may include, but not limited to, a web browser, social networking applications, streaming media applications, games, mapping and location applications, electronic mail applications, financial applications, and the like. In a typical example, the end-user typically uses one or more of the programs  316  along with a network such as the cloud-based system  100 . 
     User Device Application for Traffic Forwarding and Monitoring 
       FIG. 5  is a network diagram of the cloud-based system  100  illustrating an application  350  on user devices  300  with users  102  configured to operate through the cloud-based system  100 . Different types of user devices  300  are proliferating, including Bring Your Own Device (BYOD) as well as IT-managed devices. The conventional approach for a user device  300  to operate with the cloud-based system  100  as well as for accessing enterprise resources includes complex policies, VPNs, poor user experience, etc. The application  350  can automatically forward user traffic with the cloud-based system  100  as well as ensuring that security and access policies are enforced, regardless of device, location, operating system, or application. The application  350  automatically determines if a user  102  is looking to access the open Internet  104 , a SaaS app, or an internal app running in public, private, or the datacenter and routes mobile traffic through the cloud-based system  100 . The application  350  can support various cloud services, including ZIA, ZPA, ZDX, etc., allowing the best in class security with zero trust access to internal apps. 
     The application  350  is configured to auto-route traffic for seamless user experience. This can be protocol as well as application-specific, and the application  350  can route traffic with a nearest or best fit enforcement node  150 . Further, the application  350  can detect trusted networks, allowed applications, etc. and support secure network access. The application  350  can also support the enrollment of the user device  300  prior to accessing applications. The application  350  can uniquely detect the users  102  based on fingerprinting the user device  300 , using criteria like device model, platform, operating system, etc. The application  350  can support Mobile Device Management (MDM) functions, allowing IT personnel to seamlessly deploy and manage the user devices  300 . This can also include automatic installation of client and SSL certificates or another type of certificate during enrollment. Finally, the application  350  provides visibility into device and app usage of the user  102  of the user device  300 . 
     The application  350  supports a secure, lightweight tunnel between the user device  300  and the cloud-based system  100 . For example, the lightweight tunnel can be HTTP-based. With the application  350 , there is no requirement for PAC files, an IPSec VPN, authentication cookies, or end user  102  setup. 
     SSL Overview 
     Secure Sockets Layer (SSL) is a client-server protocol that creates a secure channel over the Internet. SSL is used to validate the identity of the destination server and (optionally) the client, and to encrypt information sent across the internet between the client and server.  FIG. 6  is a flow diagram illustrating an example handshake for HTTPS to describe a secure, encrypted tunnel between a client (e.g., the user device  300 ) and a server (e.g., the server  200 ). When a client, such as a browser, first sends an HTTPS request to a server, it starts a series of message exchanges called the SSL handshake. The client can send an HTTPS request with supported cipher suites and compression algorithms, session ID, SSL version, and a randomly generated value, i.e., a “client hello.” 
     The server sends its digital certificate to the client to authenticate itself, as well as the selected cipher suite and compression algorithm, session ID, SSL session, a randomly generated value, a certificate with a public key, and optionally a request for the client&#39;s certificate, i.e., a “server hello.” The client verifies the certificate with a Certificate Authority (CA), sends the pre-master secret computed with both random values, and encrypted with the server&#39;s public key. The client notifies the server that all subsequent messages will be encrypted with the keys and negotiated algorithms, i.e., the client and server agree on the SSL protocol version and algorithms to use, and the client and server generate the symmetric keys they will use to encrypt their messages. 
     The server uses its private key to decrypt the pre-master key, only the server with the private key that matches the public key that was sent with the certificate can decrypt the pre-master key. The server validates the browser (client) certificate and uses the public key to decrypt the messages. The server notifies the client that all subsequent messages will be encrypted using the keys and negotiated algorithms. The server computes the master key from the pre-master key and generates the session key. The server sends a message that is a hash of the exchanged messages using the master key and the session key. The client decrypts the message and validates the hash, leading to a successful handshake. 
     After the SSL handshake is successfully completed, the client and server continue with the standard HTTP communications in a secure manner. 
       FIG. 7  is a screenshot of packet capture showing SSL packets as they are exchanged between a client and a server. The client sends its HTTPS request in the Client Hello. The entire HTTPS message is encrypted, including the headers and the request/response load. The actual hostname and domain name being accessed is not visible. How the cloud-based system  100  determines the destination hostname depends on whether it is operating in transparent mode or explicit mode. The server responds with its Hello message and its certificate. (A certificate is an electronic form that verifies the identity and public key of the subject of the certificate.) SSL uses the Public Key Infrastructure (PKI) to ensure the trustworthiness of the certificates. The client and server continue with the SSL negotiation. After the SSL tunnel is established, the application data is sent securely through the tunnel. 
     SSL uses Public Key Infrastructure (PKI) to ensure the trustworthiness of the certificates. PKI uses a trusted third party, called a Certificate Authority (CA), to guarantee the identity of an entity. When a CA verifies an entity&#39;s identity, it uses an algorithm, such as RSA, to generate a public and private key. It gives the private key to the requesting entity, and the public key is made available to the public. To authenticate itself to another party, the entity uses its private key to encrypt its certificate, and the other party uses the corresponding public key to decrypt it. 
     A CA issues certificates in a tree structure, with the root certificate as the top-most certificate. The CA signs the root certificate, which is considered trustworthy in many software applications, such as web browsers. Web browsers have the root certificates of many CAs. 
     A root certificate can sign and designate a certificate as an intermediate CA certificate, which can sign and designate other certificates as intermediate certificates as well. A certificate chain refers to the list of certificates that complete the chain of trust, from the trusted root CA certificate to any intermediate certificates and the certificate of an entity. The following is an example of a certificate chain. 
     
       
         
           
               
               
             
               
                   
                   
               
             
            
               
                   
                 The certificate of mail.google.com was signed by Google Internet 
               
               
                   
                 Authority G2. 
               
               
                   
                 The certificate of Google Internet Authority G2 was signed by 
               
               
                   
                 GeoTrust Global CA. 
               
               
                   
                 The certificate of GeoTrust Global was signed by Equifax Secure 
               
               
                   
                 Certificate Authority. 
               
               
                   
                 The certificate of GeoTrust Global CA and Equifax Secure Certificate 
               
               
                   
                 Authority are in the certificate store of the browser. 
               
               
                   
                   
               
            
           
         
       
     
     Perfect Forward Secrecy (PFS) 
     Perfect Forward Secrecy (PFS) is a feature of secure communication protocols that prevent compromised session keys. In the commonly used RSA key exchange, SSL sessions between the client and web server are encrypted with the public key and decrypted with the private key. If attackers access the server&#39;s private key, they can uncover the session keys and decrypt all conversations from past and future sessions. 
     In contrast, PFS uses either the standard Diffie-Hellman ephemeral key exchange (DHE) or the Elliptic Curve Diffie-Hellman ephemeral key exchange (ECDHE). DHE uses public-key cryptography, which generates keys with modular arithmetic. In DHE, there is not a link between the server&#39;s private key and session key, so the confidentiality of session keys are not dependent on the private keys. If attackers access the server&#39;s private key, they are unable to uncover the session key and decrypt the conversation. Furthermore, the server generates different session keys for each conversation with the client. If attackers compromise the session key, they are only able to decrypt the conversation for that particular session. To decrypt all conversations, they must compromise the session keys for every session. 
     ECDHE is like DHE but uses elliptic-curve cryptography. Elliptic-curve cryptography generates keys using algebraic curves. It is significantly faster than DHE and provides better performance. Elliptic-curve cryptography achieves equivalent security as RSA with smaller keys. 
     SSL Inspection 
     HTTPS is an aggregate of HTTP and the SSL/TLS protocol, wherein the authentication and encryption capabilities of SSL/TLS protect HTTP communications. This is vital because the information that is sent on the Internet is passed along from one device to another before it reaches the destination server. Therefore, sensitive information, such as credit card numbers, usernames, and passwords, may be seen by intermediate devices if the information is sent in clear text over HTTP. When the information is encrypted and protected by the SSL protocol, only the intended recipient can read the information. 
     Unfortunately, the security provided by SSL is also being misused in a number of ways: 
     SSL encryption is used to hide dangerous content such as viruses, spyware, and other malware. 
     Attackers build their websites with SSL encryption. 
     Attackers inject their malicious content into well-known and trusted SSL-enabled sites. 
     SL can be used to hide data leakage, for example, the transmission of sensitive financial documents from an organization or the like. 
     SSL can be used to hide the browsing of websites that belong to legal-liability classes. 
     As more and more websites use HTTPS, including social media, the ability to control and inspect traffic to and from these sites has become an important piece of the security posture of an organization. 
     The cloud-based system  100  can inspect HTTPS traffic from an organization. The service can scan data transactions and apply policies to it, as described herein. An enforcement node  150  can function as a full SSL proxy, or SSL man-in-the-middle (MITM) proxy. 
     The cloud-based system  100  can provide two options to protect HTTPS traffic: SSL inspection, or if SSL inspection is not feasible, one can configure a global block of specific HTTPS content. 
       FIG. 8  is a flow diagram illustrating an embodiment of SSL inspection  380  with the cloud-based system  100  as a proxy. In this embodiment, the cloud-based system  100  establishes a separate SSL tunnel with the user&#39;s browser and with the destination server.  FIG. 8  illustrates the SSL inspection  380  process. First, a user (at the user device  300 ) opens a browser and sends an HTTPS request. Second, the cloud-based system  100  intercepts the HTTPS request. Through a separate SSL tunnel, the cloud-based system  100  sends its HTTPS request to the destination server (the server  200 ) and conducts SSL negotiations. The destination server sends the cloud-based system  100  its certificate with its public key. The cloud-based system  100  and destination server complete the SSL handshake. The application data and subsequent messages are sent through the SSL tunnel. The cloud-based system  100  conducts SSL negotiations with the user&#39;s browser. R sends the browser an intermediate certificate or an organization&#39;s custom intermediate root as well as a server certificate signed by the intermediate CA. The browser validates the certificate chain in the browser&#39;s certificate, store. The cloud-based system  100  and the browser complete the SSL handshake. The application data and subsequent messages are sent through the SSL tunnel. 
     In an embodiment, the SSL inspection can use an intermediate certificate of the cloud-based system  100 , With this option, the cloud-based system  100  dynamically generates and signs the server certificate that it presents to the client. This certificate contains the same fields as the original destination server certificate, except for the identifying information of the issuer, called the issuer distinguished name (ON). The issuer DN is set to the name of the cloud-based system  100  intermediate certificate. The browser receives this certificate signed by the cloud-based system  100  intermediate certificates along with the cloud-based system  100  intermediate certificate. To enable a browser or system to automatically trust all certificates signed by the cloud-based system  100  Certificate Authority, users must install the cloud-based system  100  Root CA certificate on their workstations. 
     In another embodiment, the SSL inspection can use a custom intermediate root certificate. One can subscribe to the Custom Certificate feature and configure a custom intermediate root certificate for SSL inspection. Here, the cloud-based system  100  does not use an organization&#39;s root certificate or private keys, Instead, it uses the custom intermediate root certificate signed by a trusted CA, so it is possible to use a CA that is already deployed on an organization&#39;s machines. To configure an intermediate root certificate, the cloud-based system  100  generates a Certificate Signing Request (CSR) with a key pair (i.e., public and private key) and encrypts the private key using AES. The private key is stored securely in the central authority  152 , while the CSR contains the public key. 
     After the CA signs the CSR, the signed certificate can be uploaded to the cloud-based system  100 . During the SSL negotiation with the user&#39;s browser, the cloud-based system  100  dynamically generates and signs the server certificate that it presents to the client with this intermediate certificate. The certificate issuer is set to the organization name, and the cloud-based system  100  generates the certificate once per site and caches these certificates on the enforcement node  150 . These cached certificates are usually valid until their expiration date. 
     In addition to the intermediate root certificate, it is possible to upload the certificate chain that includes any other intermediate certificates that complete the chain to the intermediate root certificate. When the certificate chain is uploaded, the cloud-based system  100  sends the intermediate root certificate along with this key chain and the signed server certificate to the users&#39; machines during SSL inspection. If the certificate chain is not uploaded, the cloud-based system  100  sends only the organization&#39;s intermediate root certificate and its signed server certificate to the user&#39;s machine. Uploading the certificate chain provides important benefits. The certificate chain ensures that the users&#39; machines can validate the server certificate signed by the organization&#39;s intermediate CA even if the users&#39; browsers have only the root certificate in their certificate store. If the certificate is changed due to the compromise of an intermediate root certificate, or simply as a routine security measure, the ability to send the certificate chain to users&#39; machines during SSL inspection is a key benefit. Because it enables certificate rotation efficiently without the need for a new key ceremony or certificate push to an organization&#39;s users. 
     The cloud-based system  100  provides a CRL (Certificate Revocation List) distribution point (CDP) for every certificate it generates so that client applications can locate the Certificate Revocation Lists (CRLs) as necessary. 
     SSL Handshake Process 
       FIG. 9  is a flow diagram of details of an SSL handshake process  400  between an SSL client  402  and an SSL server  404 . The SSL client  402  can be the user device  300 , etc. and the SSL server  404  can be a location on the Internet  104 , etc., i.e., the server  200 . That is, the SSL server  404  can be an endpoint for an encrypted tunnel with the user device  300 . The SSL client  402  sends a “client hello” message that lists cryptographic information such as the SSL version and, in the client&#39;s order of preference, the CipherSuites supported by the SSL client  402  (step  410 - 1 ). The message also contains a random byte string that is used in subsequent computations. The protocol allows for the “client hello” to include the data compression methods supported by the SSL client  402 . 
     The SSL server  404  responds with a “server hello” message that contains the CipherSuite chosen by the SSL server  404  from the list provided by the SSL client  402 , the session ID, and another random byte string (step  410 - 2 ). The SSL server  404  also sends its digital certificate. If the SSL server  404  requires a digital certificate for client authentication, the SSL server  404  sends a “client certificate request” that includes a list of the types of certificates supported and the Distinguished Names of acceptable CAs. The SSL client  402  verifies the SSL server&#39;s  404  digital certificate (step  410 - 3 ). 
     The SSL client  402  sends the random byte string that enables both the SSL client  402  and the SSL server  404  to compute the secret key to be used for encrypting subsequent message data (step  410 - 4 ). The random byte string itself is encrypted with the SSL server&#39;s  404  public key. If the SSL server  404  sent a “client certificate request,” the SSL client  402  sends a random byte string encrypted with the client&#39;s private key, together with the SSL client&#39;s  402  digital certificate, or a “no digital certificate alert” (step  410 - 5 ). This alert is only a warning, but with some implementations, the handshake fails if client authentication is mandatory. The SSL server  404  verifies the client&#39;s certificate if required (step  410 - 6 ). 
     The SSL client  402  sends the server a “finished” message, which is encrypted with the secret key, indicating that the SSL client  402  part of the handshake is complete (step  410 - 7 ). The SSL server  404  sends the SSL client  402  a “finished” message, which is encrypted with the secret key, indicating that the SSL server  404  part of the handshake is complete. For the duration of the SSL session, the SSL server  404  and SSL client  402  can now exchange messages that are symmetrically encrypted with the shared secret key (step  410 - 9 ). 
     SSL Interception Proxies 
       FIG. 10  is a flow diagram of a process  500  performing SSL interception through an interception proxy  510  in the handshake process  400 . The interception proxy  510  can be one of the enforcement nodes  150  in the cloud-based system  100 . Enterprises deploy or use the interception proxy  510  to secure themselves from SSL-based threats, which are increasingly common. The interception proxy  510  works by acting as a MitM and modifying the encrypted channel. Whenever the SSL client  402  initiates a connection to a remote SSL server  404 , the interception proxy  510  will intercept it and open two different channels of communication, one with the SSL client  402  and the other with the SSL server  404  that the SSL client  402  intended to talk to in the first place. This allows the interception proxy  510  to actively modify/inject the content from the SSL client  402  to the SSL server  404  or vice versa. This allows IT admins to perform malware scanning and other security functions on the otherwise encrypted content. In order to achieve this, an IT admin usually deploys proxy&#39;s ROOT CA certificate on the user devices  300  for the SSL clients  402  to trust the handshake which happens between the SSL client  402  and the interception proxy  510  which generates a certificate for every SSL server  404  that the SSL client  402  tries to communicate with. This naturally breaks with apps that employ certificate pinning for enhanced security. 
     Advantageously, the interception proxy  510  enables interception, inspection, and filtering of content on an otherwise encrypted channel. For example, the cloud-based system  100  using the interception proxy  510  can perform DLP, web content filtering, malware detection, intrusion detection/prevention, firewall and Deep Packet Inspection (DPI), etc. The interception proxy  510  acts as the SSL client  402  on the SSL server  404  side and as the SSL server  404  on the SSL client  402  sides. 
     The interception proxy  510  performs SSL inspection by breaking or terminating the encrypted tunnel in the cloud-based system  100 . Specifically, the enforcement node  150  is a proxy, and it has an encrypted tunnel with the client and another encrypted tunnel with the server. That is, this approach requires SSL/TLS/DTLS handshake/termination on the enforcement node  150  (in the cloud, on-premises, etc.). This approach, with the enforcement node  150  as a MitM proxy breaking the tunnel has limitations. Specifically, some applications use Certificate Pinning or other techniques to prevent MitM. With Certificate Pinning, the client is configured to only accept a specific certificate or a specific CA. In this case, the application will break when presented with a certificate signed by the cloud-based system  100 , even if it is trusted. 
     This is done to ensure greater control over the communicating entities and to prevent the MitM attacks. The situation is somewhat of a paradox: entities such as Domain Name Systems (DNS) and CAs are trusted and supposed to supply trusted input. However, more and more applications are trying hard with pinning to eliminate this conference of trust. By pinning the certificate or the public key of the server certificate, an application no longer needs to depend on third-party entities such as DNS, CA, etc. when making security decisions relating to a peer&#39;s identity. This makes an app immune to MitM attacks. Pinning effectively removes the “conference of trust” by eliminating the set of entities that are beyond the control of a domain owner. Apps achieve this by accepting server certificates that strictly match a defined criterion, usually subject key information. 
     With the SSL interception, proxy servers are employed in the cloud-based system  100  are aware of the SSL encrypted communication and may need to intercept it in order to provide security services. Such filtering solutions are generally achieved through interception proxies that engage in deep packet inspection to resist SSL-based threats that may range from trivial viruses to sophisticated ransomware. The problem when apps employ certificate pinning is that they reject the connection during negotiation with an interception proxy on account of peer&#39;s (in this case, SSL proxy) untrusted certificate. 
     Such apps fail to function in the enterprise environment and fail to provide desired services leading to bad user experience and frustration. The apps would be rendered dysfunctional partially or completely due to the certificate pinning employed by them. They will terminate the connection upon receiving a server certificate from the proxy that does not match the criterion. This leads to bad user experience, and the cloud security system does not have any visibility or resolution of such issues. 
     As more and more viruses use encrypted channels to infect machines, it is imperative for enterprises to employ SSL interception proxies to protect users. This poses a conundrum as app developers would like to eliminate trust on third parties like CAs, which may be vulnerable to other attacks. To solve this issue, an IT admin may be lured to turn SSL interception off, which makes their enterprise security even worse. Hence, it is desirable for IT admins to selectively turn SSL interception off only for some trusted applications and domains. Since it is very hard for IT admins to know apriori which apps users will use or what domains the app may hit, which may even change over time, there is a huge need for a better tunneling solution. 
     The cloud-based system  100  has little or no idea about the dysfunctional apps. The client apps terminate the connection with or without an alert message to the server upon receiving the mismatched certificate. Further, the IT admin has no way to find all the apps and their server domains for which the app performs pinning. As a result, this design does not allow the users to use such apps while subscribing to the security or enterprise compliance policies. To make these apps functional again, the cloud-based system  100  cannot perform the SSL interception described in  FIG. 8 , e.g., bypass SSL interception. 
     SSL Interception 
       FIG. 11  is a network diagram of a network  600  with the enforcement node  150  configured as an interception proxy  510 . As such, an interception proxy  510  in the cloud-based system  100  can selectively intercept SSL communications. In an embodiment, Internet-bound traffic of the user device  300  (the SSL client  402 ) is controlled through a tunnel  610  to the cloud-based system  100  which has a second tunnel  612  to the SSL server  404 . The tunnel  610  acts as an intermediary passive MitM proxy that relays all the network requests and responses from client applications  620  to the cloud-based system  100 . To achieve this, a process running on the host (the SSL client  402 ) installs a virtual interface on the user device  300 . The process installs a default route on the interface in the device routing table and opens listening sockets for User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) traffic at randomly available ports. 
     SSL Inspection Based on Key Snooping 
       FIG. 12  is a network diagram of a network  700  with the enforcement node  150  operating as a snooping proxy  710  to perform SSL interception without breaking the tunnel as with the interception proxy  510 . This presents a different approach for SSL interception than the interception proxy  510 , which avoids the disadvantages of certificate pinning and certificate management. In the network  700 , a tunnel  720  is between the SSL client  402  and the SSL server  404 . Again, the tunnel  720  can be SSL, TLS, DTLS, HTTPS, etc. The key difference with the snooping proxy  710  relative to the interception proxy  510  is the snooping proxy  710  does not break the tunnel  720 . Note, the snooping proxy  710  is still a MitM proxy like the interception proxy  510 . 
     The snooping proxy  710  can be one of the enforcement nodes  150  in the cloud-based system  100 . Also, the client  402  can be the user device  300  including the application  350 . As described herein, the application  350  is a traffic-forwarding application that enables the user device  300  to operate (communicate) with the cloud-based system  100 . The snooping proxy  710 , being already a MitM proxy, can snoop (monitor) on the handshake process  400 . This snooping can be at the enforcement node  150  operating as the snooping proxy  710  as well as at the application  350 . This snooping can also use key agents, such as part of the application  350 , operating system support hooks, such as at the user device  300 , etc. The key aspect here is the snooping proxy  710  can snoop the handshake process  400  for purposes of obtaining keys. 
     Once the snooping proxy  710  has keys for a given session, the snooping proxy  710  can monitor the encrypted traffic on the tunnel  720 . Note, typically, monitoring in the cloud-based system  100  is inline in a sense the enforcement node  150  sits directly between the client  402  (the user device  300 ) and the server  404  (or any other destination on the Internet  104 , the cloud services  106 , etc.). Here, the snooping proxy  710  is still inline. The snooping proxy  710  can receive encrypted traffic, view and inspect the traffic based on the snooping of the keys, and allow or block the traffic based on the inspection. 
     This approach solves the various limitations with a traditional MitM proxy as an interception proxy  510 . That is, applications with certificate pinning now can support SSL inspection to block policy violations or malware transfers. This removes the need for certificate deployments with the cloud-based system  100 . Also, it is possible to decode any other variant of SSL to inspect or detect application signature (aka DPI) inside an encapsulated layer or protocol. Further, this approach is completely transparent to primitive SSL-based applications such as FTPS, which cannot trust MitM root certificates. Finally, this allows granular policy control and transactional visibility for critical or productivity applications without breaking the SSL protocol. 
     SSL Profile Construction, Learning and Transfer of Knowledge 
     In either SSL environment, namely the interception proxy  510  and the snooping proxu  710 , for every new connection, the application  350  process on the device can create a state machine or the like for the transaction, and, based on the results of the transaction, the process constructs a profile for the SSL client  402  which initiated the connection. For every connection, the process can construct a profile for the connection as a tuple: &lt;Origin, Host-Name, Destination-Socket-Address, Handshake-Status, Key information&gt;. 
     The origin is the client application  620 , which is originating a request. The origin information is obtained through a process to port mapping on the host machine. The Host Name is the fully qualified domain name of the SSL server  404  that the SSL client  402  is trying to reach. The hostname is retrieved from the SNI (Server Name Indication) parsed as a TLS extension in the Client Hello SSL record. The Destination Socket contains information about Destination-Server-IP-Address:Destination-Port that the SSL client  402  is trying to establish a connection. This information is retrieved by parsing the IP-packet header during connection establishment. 
     The Handshake Status is a bit flag that keeps a record of SSL handshake messages exchanged with the SSL server  404 . The flag is set to 1 if the handshake succeeds, and the client starts sending Application Data to the server. The profile is learned for every transaction and reevaluated whenever the SSL client  402  tries to reach the same destination. This knowledge is periodically transferred to the cloud-based system  100  out-of-band on a persistent control channel that allows the cloud-based system  100  to learn the behavior of client apps  620  with SSL interception. 
     To construct this profile, the process passively observes the SSL Record Layer data messages and keep track of all the records that have been exchanged for any given transaction. For example, the process can parse the SSL headers to check if the SSL client  402  returns an SSL alert and/or if application data is sent over the connection. The process can parse the initial (K) server bytes and check the intermediate CA certificate from the enforcement node  150 . The process can find the processes and host corresponding to the connection. 
     The following SSL handshake messages can be recorded: 
     Client hello to determine the SSL server  404  the SSL client  402  wants to connect with. The SNI host field provides the information. 
     Server Hello to determine the server response towards the client request and client supported ciphers. 
     A certificate that contains the certificates advertised by the SSL server  404  and which is used to check if SSL interception is enabled for the transaction. 
     Alert (optional), which indicates if the SSL client  402  rejected the certificate and the reason for rejection. 
     Application data which indicates the successful handshake since the application data is exchanged now. 
     This process can be extended to generate more detailed profiles containing the ciphers supported by the SSL client  402  and the SSL server  404 , SSL version, certificate chain, etc. 
     Every SSL message is sent as part of the Record Layer Protocol which provides messages in the following format: 
                                            Content type (1 Octet)   Version (2 Octets)   Length (2 Octets)   Data                    
Security Functions on Traffic with SSL Inspection, Either with the Interception Proxy or the Snooping Proxy
 
     The cloud-based system  100  can support various security functions on encrypted traffic, including: 
     Granular URL filtering and cloud app control policies where the cloud-based system  100  can enforce granular user, group, and location policies that not only control access to sites or applications but also control what a user can do within an application. For example, it is possible to define a Web email policy that allows users to view and send mail, but not attachments, or a social media policy that allows users to view Facebook, but not post. 
     Skipping Inspection for Specific URLs/URL categories: When configuring SSL Inspection policy, it is possible to prevent the service from inspecting sessions to certain URLs or URL categories (for example, in the Banking and Healthcare URL categories). This list can apply globally through an organization as well as granular to users, groups of users, etc. 
     Skipping Inspection for Specific Cloud Applications/Cloud Application Categories: When configuring SSL Inspection policy, it is possible to prevent the cloud-based system  100  from inspecting transactions to specific cloud applications or cloud application categories. This list can apply globally through an organization as well as granular to users, groups of users, etc. 
     Content Filtering where the cloud-based system  100  is enabled to block malicious or inappropriate content in a page, such as during a Google search. 
     Block Undecryptable Transactions: wherein the cloud-based system  100  is configured to block the transactions of applications that the cloud-based system  100  cannot decrypt because of using non-standard encryption methods and algorithms, as well as where snooping fails and where the interception proxy  510  encounters certificate pinning. 
     Block Advanced Persistent Threats (APT) in encrypted traffic. Note, most targeted malware is now delivered over SSL. 
     Control access to Google consumer apps and non-corporate Google accounts. 
     Block access to sites with revoked certificates: The cloud-based system  100  supports OCSP (Online Certificate Status Protocol) to verify the validity of all server certificates. It verifies the OCSP responder URL in a server&#39;s certificate and sends an OCSP request to the responder. The cloud-based system  100  allows access if the responder indicates that the certificate is Good, and blocks access if the responder responds that the certificate is Unknown or Revoked. The cloud-based system  100  displays a notification when it blocks access to a site due to a bad certificate (if the certificate issuer is unknown, or if the certificate has expired, or if the Common Name in the certificate does not match). It also logs these transactions with “bad server cert” in the policy field. 
     Data Loss Prevention (DLP): The cloud-based system  100  can enforce the DLP policy when SSL inspection is enabled. 
     Of note, the enforcement node  150  can be configured, not as a caching proxy. Data is inspected in the enforcement node&#39;s  150  memory after decryption and sent out to the client immediately. Even when a core dump is taken on the enforcement node  150 , SSL (encrypted) session data is cleared before the dump file is created. SSL session data is never written to disk. 
     SSL Inspection Process by Snooping 
       FIG. 14  is a flowchart of a process  800  for SSL (or other type of encrypted traffic) inspection by snooping, such as via a node operating as the snooping proxy  710 . The process  800  contemplates implementation as a method, as a computer-readable code stored on a non-transitory computer-readable storage medium for programming the node operating as the snooping proxy  710 , and one the node operating as the snooping proxy  710 . 
     The process  800  includes monitoring traffic between a user device and the Internet (step  801 ); detecting and monitoring a handshake between the user device and an endpoint for determining keys associated with encryption between the user device and the endpoint (step  802 ); monitoring encrypted traffic between the user device and the endpoint subsequent to the handshake based on the keys (step  803 ); and performing one or more security functions on the encrypted traffic based on the monitoring (step  804 ). The node can be the enforcement node  150  that is part of a cloud-based security system, i.e., the cloud-based system  100 , and configured inline between the user device and the endpoint. 
     The process  800  can further include one of blocking or allowing the encrypted traffic based on the one or more security functions. The one or more security functions can include any of access control, threat prevention, and data protection, as described in detail herein. The endpoint can include an application utilizing certificate pinning. The process  800  can further include obtaining data related to the keys from a traffic-forwarding application executed on the user device. The process  800  can further include blocking the encrypted traffic responsive to being unable to decrypt the encrypted traffic with the keys. 
     It will be appreciated that some embodiments described herein may include one or more generic or specialized processors (“one or more processors”) such as microprocessors; Central Processing Units (CPUs); Digital Signal Processors (DSPs): customized processors such as Network Processors (NPs) or Network Processing Units (NPUs), Graphics Processing Units (GPUs), or the like; Field Programmable Gate Arrays (FPGAs); and the like along with unique stored program instructions (including both software and firmware) for control thereof to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the methods and/or systems described herein. Alternatively, some or all functions may be implemented by a state machine that has no stored program instructions, or in one or more Application-Specific Integrated Circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic or circuitry. Of course, a combination of the aforementioned approaches may be used. For some of the embodiments described herein, a corresponding device in hardware and optionally with software, firmware, and a combination thereof can be referred to as “circuitry configured or adapted to,” “logic configured or adapted to,” etc. perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. on digital and/or analog signals as described herein for the various embodiments. 
     Moreover, some embodiments may include a non-transitory computer-readable storage medium having computer-readable code stored thereon for programming a computer, server, appliance, device, processor, circuit, etc. each of which may include a processor to perform functions as described and claimed herein. Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, an optical storage device, a magnetic storage device, a Read-Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), Flash memory, and the like. When stored in the non-transitory computer-readable medium, software can include instructions executable by a processor or device (e.g., any type of programmable circuitry or logic) that, in response to such execution, cause a processor or the device to perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. as described herein for the various embodiments. 
     Although the present disclosure has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present disclosure, are contemplated thereby, and are intended to be covered by the following claims.