CN103312814A - Method for establishing VNC covert channel between cloud management platform and virtual machine end users - Google Patents

Abstract

The invention relates to the technical field of computer virtualization, and provides a method for establishing a VNC hidden channel between a cloud management platform and a virtual machine terminal user. The scheme mainly comprises three modules of message conversion, message sending and message feedback receiving. The message conversion module is an interface of a calling channel and is responsible for converting message contents into pixel data which can be identified by a message sending end; the message sending module is responsible for adding the pixel data of the message image into original communication frames of the VNC server and the VNC client and sending the modified communication frames to the VNC client together; the message feedback receiving module is responsible for capturing the operation response of the user to the message window during the channel display period and sending the operation response to the message conversion module. Therefore, the invention has the following advantages: only part of VNC server side function source codes in the KVM virtualization cloud platform need to be modified, the system of the virtual machine can be transparent, and real-time bidirectional interaction can be carried out between the cloud management platform and a virtual machine terminal user.

Description

Method for establishing VNC covert channel between cloud management platform and virtual machine end users

the

technical field

The invention relates to the technical field of computer virtualization, in particular to a method for establishing a VNC covert channel between a cloud management platform and a virtual machine terminal user.

Background technique

At present, various cloud management platforms have emerged in the industry. With the continuous improvement of the functions of these cloud platforms, a large number of management messages will be generated during the normal operation of the platform and need to be notified immediately to the end users of the virtual machines in the cloud platform. , such as informing virtual machine tenants of their real-time consumption information;

On the other hand, there are currently a series of virtual machine security monitoring suites deployed at the VMM layer. During the monitoring process of these security suites, when they find that there are security risks in the virtual machine system, they may need to notify the virtual machine in real time. The terminal user waits for the user's interactive selection before proceeding to the next step.

At present, there are three main methods for real-time communication between the cloud management platform and remote terminal users of the virtual machine: one is to install the communication software server and client respectively in the cloud management terminal and the virtual machine system, that is, to integrate the traditional server/ The client communication method is applied between the physical machine and the virtual machine in the cloud management platform; this method needs to install a communication software plug-in or client inside the virtual machine system, but because the end user has full control over the virtual machine system itself, If the user chooses to reinstall the system or clean up the plug-in, it is likely to invalidate the function of the communication software client, which means that the anti-interference ability of this method is low;

The second way is to directly install the communication software server and client respectively on the cloud platform management machine and the machine where the virtual machine end user is located, that is, the traditional server/client communication method is adopted between physical machines; this way There are specific requirements for the client platform, which is limited by the system where the user is located. The client needs to develop various versions of Windows, Mac, Linux/Unix series, etc., and even the current mobile terminal needs to develop corresponding The client program largely loses the convenience and ease of use of the remote control function of the cloud platform, and at the same time has low resistance to user interference;

The third method is the method proposed and adopted by the present invention: in this method, by modifying the software server end of the virtual machine remote desktop control adopted in the cloud platform, the message to be sent is integrated into the virtual machine desktop image, and then sent together to The remote desktop control software client used by end users; this method does not need to install any plug-ins or communication clients inside the virtual machine system, that is, the message channel is transparent to the virtual machine system itself; Install any plug-ins or communication clients on the user's machine or make any other changes, that is, this method is non-destructive to the scope of application of the original virtual machine remote desktop control software.

Contents of the invention

The scheme designed in the present invention is based on the open-source virtual machine remote desktop control software VNC, combined with the current rapidly developing KVM virtualization platform, by modifying the server code of the remote control software, and finally establishing a system transparent to the virtual machine's own system A message channel for two-way interaction between the cloud platform and end users.

The present invention is mainly solved by the following technical solutions:

A method for establishing a VNC covert channel between a cloud management platform and a virtual machine terminal user, the VNC covert channel includes the following three modules:

Message conversion module: The message conversion module is located on the actual physical host where the virtual machine is located, independent of the QEMU module in the KVM architecture, providing an interface for the cloud platform to call the VNC covert channel, and generating the original message that the cloud platform administrator wants to send to the end user The channel message window dialog box set by the administrator captures the pixel information of the window image and converts it into a pixel format and encoding method that can be recognized in the general VNC communication process; at the same time, it also receives the end user feedback sent by the message feedback receiving module Then pass the user's operation on the message channel to the cloud platform administrator;

Message sending module: The message sending module is located in the QEMU module code of the KVM architecture on the physical host where the virtual machine is actually located. By modifying the source code of some VNC server functions in the KVM architecture of the KVM virtualization solution, the message sending module is added. Module source code, in modifying the code, convert the message pixel data that the administrator wants to send to the end user into the format used in the current VNC connection, and then seamlessly add it into the original VNC server and client communication frame message;

Message feedback receiving module: The message feedback receiving module is located in the QEMU module code in the KVM architecture on the physical host where the virtual machine is actually located. By modifying the source code of the VNC server function in the QEMU module in the KVM architecture in the KVM virtualization solution, add a message The feedback receiving module captures the mouse operation of the terminal user during the display of the message on the terminal user's desktop in the code, and sends the mouse operation information in the display area of the channel message window sent by the terminal user to the message conversion module through a named pipe.

The present invention creatively realizes the following functions:

First, server-side message push. On the control node of the cloud management platform, the message to be displayed can be sent to the remote virtual machine terminal user through this channel. The display of this message is real-time, that is, after the server sends it, the client can see it immediately;

Second, identify client user feedback. After the server pushes the message to the client through the message channel, the end user reacts differently to the pushed message window according to their own needs. At this time, the server should be able to identify the user's specific feedback operation for the channel message window. And the user feedback is sent to the control terminal of the cloud management platform, and the cloud management platform performs corresponding processing according to its different operation events.

Third, push message layout customization. At the sending end of the message, the cloud management platform should be able to customize the content and layout of the channel message window displayed on the end user's VNC client according to its different needs.

Among them, the main architecture of the above-mentioned message conversion module can be subdivided into the following parts:

Platform message interaction interface: This interface is responsible for direct information interaction with the original message sender (cloud management platform master control node or cloud management personnel, etc.). The template type and the configuration file (generally named after the port) including the number of message content blocks, message content, user interactive operation type, user operation content and other parameters. The meaning of the parameter content is shown in Figure 1;

Image pixel data file: This file is used to store the image pixel data of the message window to be finally displayed on the end user VNC client. Including the width, height, pixel format and specific pixel data content of the message window.

Window configuration information completion unit: This part is responsible for completing the message window configuration information sent by the cloud platform, and adopts the default settings for the window configuration parameters not specifically customized by the cloud platform administrator.

Message window layout template unit: the main function is to tell the message conversion part what kind of message window should be generated, that is, which components and component contents are included in the message window.

Message conversion unit: This is the core functional part of the module, which is responsible for the format conversion of the message to be sent and the coordinate conversion of user feedback operations. When the platform message conversion interface receives the message sent by the cloud management platform or managers, the message conversion part will transfer to the window configuration information completion part according to the parameters transmitted by it. After completing the undefined window parameters of the cloud platform, follow the The window layout corresponding to these parameters generates the final message image window to be displayed, and finally the image pixel data corresponding to the window is stored in a specific file so that the message sending module can read it;

Another function of the message conversion part is to find the actual operation in the corresponding tuple according to the position of the coordinate after receiving the end user's operation coordinate from the user feedback interface, such as the coordinate is in the position of the first operation component , it means that the user chooses the first operation, and so on...Finally, the corresponding operation content is sent to the platform message interaction interface. When it is detected that the x and y coordinates of the feedback operation sent by the user are located in the operation control area of the message window and the feedback is a mouse click event, the corresponding control content (that is, the selection of the message window by the end user of the virtual machine) is sent to At the same time, the sender of the original message deletes the message image pixel data file to end the display of the current channel message.

Receiving user feedback unit: This part is mainly used to receive the coordinates of the user operation sent by the user message feedback receiving module in the VNC server, and send it to the message conversion part as its input. The implementation of this part is mainly to monitor the input of the named pipe of the corresponding virtual machine during the message display period, that is, the message feedback receiving module writes the user feedback message to the named pipe, and the sending module reads the message in the pipe, and the pipe is used here The blocking method, that is, if the pipeline write message is not received, it will continue to monitor.

The message conversion module is located on the cloud service provider node, and the cloud service provider node is the physical host where the virtual machine is actually located; the message conversion module is independent of the QEMU module program in the KVM architecture, and is a call provided by the VNC covert channel to the outside Interface, its implementation process includes the following steps:

Step 1: First read the content of the message sent by the administrator and the typesetting and layout information of the message channel according to the parameters set by the administrator calling the platform message interaction interface of the VNC covert channel;

Step 2: After the message conversion unit receives the configuration information read in step 1, it calls the window configuration information completion unit module, and queries the message window layout template unit according to the template model set by the administrator in the window configuration information completion module. Complete the unconfigured parameter information when the administrator calls the VNC covert channel;

Step 3: Generate a temporary message window according to the message window configuration information completed in step 2, the appearance of the temporary message window is the same as that of the channel message window seen by the final remote terminal user on its own VNC client;

Step 4: Then grab the image information of the message window generated in step 3, and generate the corresponding message window bmp screenshot;

Step 5: Read the bmp image information generated in step 4, and convert the image information into a 32-bit true-color image pixel data file using RAW encoding, so that the subsequent message sending module can read it;

Step 6: At the same time, the user feedback unit monitors the selection result of the end user for the channel message sent back by the message feedback receiving module, and sends the specific content of the selection result of the end user to the cloud management after the message conversion module parses and processes it The original sender of platform messages.

In the present invention, the above-mentioned message sending module is mainly divided into three parts: a message image reading unit, a message image image conversion unit, and a message image image adding unit:

Message image pixel reading unit: After the message conversion module generates the pixel data of the message window image and stores it in a specific file, the image pixel reading part in the message sending module first grabs the port number of the current VNC connection, and then according to the The port number is used to read the channel message pixel data under the corresponding specific path, including the width, height, pixel format, and pixel data content of the message window.

Message image pixel conversion unit: this part first obtains the pixel format selected by the terminal user during the current VNC communication session, and then compares it with the pixel format obtained by the image pixel reading part above. The image pixel data read above is converted. If the user selects 8 bits and the message image pixels are 32 bits, the 32-bit pixel data is converted into 8-bit data according to the image conversion principle.

Message image data adding unit: After converting the image data into the same format as the current VNC connection, before sending the VNC original desktop image frame buffer update information frame (FramebufferUpdate), combine the frame buffer update information frame data structure to add the message image Pixel data is appended after the infoframe.

The message sending module is implemented by modifying the frame buffer update information frame in the communication process, and its implementation process includes the following steps:

Step 1: Find the code generated by the raw data of the server during the communication between the VNC server and the client. In the QEMU module in the KVM architecture, this part is located in the vnc_worker_thread_loop function under qemu-kvm/ui/vnc-jobs.c, in Add code to this function to perform the following steps;

Step 2: the message image pixel reading unit reads the message image pixel data generated by the message conversion module;

Step 3: Obtain the pixel format and encoding method used in the current VNC connection process;

Step 4: Then the message image conversion unit starts to further convert the message image pixel data read in step 1 into the pixel format and encoding method used in the VNC connection process;

Step 5: In combination with the data structure of the desktop image update information frame, the message image pixel data adding unit adds the pixel data in the rectangular area of the message image converted in step 4 to the back of the normal image update information frame, so that the VNC client receives the information After the frame, when drawing on its own terminal display, it will be able to draw the message window transmitted in the message channel at the same time.

The core operation of the message feedback receiving module in the present invention is to identify the user's operation selection for the message window during the display of the message channel and to process it accordingly. The first byte in the VNC communication information frame sent by the client indicates the type of the information frame, such as a value of 05 indicates a mouse event. The user operation feedback to be captured in this solution mainly refers to the mouse operation issued by the end user. The second byte in the mouse information frame represents the key name of the mouse click (such as left click, right click, sliding the middle wheel, etc.) and the third to six bytes represent the x, y coordinates of the mouse operation. Analyze the x and y coordinates in the information frame to determine whether it is in the window area of the message channel. If so, it is considered that the object of the user's operation is the message window. At this time, the coordinates will be sent to the message conversion module, and a message area will be generated at the same time update event. The implementation process of the area update event is mainly to simulate and generate a full update frame buffer update request information frame of a specified rectangular area sent by the client, so that the VNC server can update the rectangular area where the message channel window is located.

The implementation process includes the following steps:

Step 1: Find the code for the server to receive the feedback data from the client terminal user during the communication process between the VNC server and the client. In the QEMU module in the KVM architecture, this part is located in the vnc_client_read function under qemu-kvm/ui/vnc.c , add code to the function to perform the following steps;

Step 2: Determine whether it is in the display period of the covert channel message, if so, intercept the interactive information frame sent from the client in the current session connection, otherwise it indicates the original communication between the VNC server and the client, and the message feedback module does not perform additional operations at this time ;

Step 3: According to the position of the mouse operation coordinates in the intercepted interactive information frame, judge the object targeted by the user in this operation. The object includes the channel message or the access system. If the mouse operation is within the rectangular area where the message window is located, it indicates that the user The object of the mouse operation is the message channel window;

Step 4: After receiving the interactive information frame for the channel message, send the specific content of the operation to the message conversion module program on the cloud service provider node, and the message conversion module will send the final content to the original sender of the channel message;

Step 5: Change the interaction information frame to an image update information frame that updates the rectangular area where the current message window is located, that is, generate a message area update event, update the screen area where the message window is located, and complete an interaction.

Therefore, the present invention has the following advantages: 1. High stability, transparent to the system of the virtual machine itself. The present invention integrates the message to be sent into the desktop image of the virtual machine by modifying the software server end of the remote desktop control of the virtual machine adopted in the cloud platform, and then sends it to the remote desktop control software client used by the terminal user together, which does not require Install any plug-in or communication client inside the virtual machine system, even if the user chooses to reinstall the system or perform other operations, the hidden channel function can still function, that is, the message channel is transparent to the virtual machine system itself 2. Convenient and non-destructive , the scope of application. The present invention does not need to install any plug-in or communication client on the terminal user's machine or make any other changes, and the virtual machine terminal user can use a browser or a vnc client on any system environment such as windows, linux, mac or even an intelligent mobile terminal You can experience this function, that is, this method is nondestructive to the scope of application of the original virtual machine remote desktop control software.

Description of drawings

Fig. 1 is a schematic diagram of the overall design of the VNC channel of the present invention.

Fig. 2 is a structural diagram of the channel message conversion module of the present invention.

Fig. 3 is an architecture diagram of the channel message sending module of the present invention.

Fig. 4 is a data structure diagram of the desktop image update information frame used in the message sending module of the present invention.

Fig. 5 is a flow chart of the channel message feedback receiving module of the present invention.

Fig. 6 is a data structure diagram of the interactive information frame used in the message feedback receiving module of the present invention.

specific implementation plan

The technical solutions of the present invention will be further specifically described below through the embodiments and in conjunction with the accompanying drawings.

Example:

Referring to Figure 1, in the cloud platform using KVM virtualization technology, the function of realizing the interactive message channel between the cloud management platform and the virtual machine remote terminal user mainly includes three modules: message conversion, message sending, and message feedback receiving.

Message conversion module: The message conversion module is located on the physical host where the virtual machine is actually located. It is independent of qemu-kvm and is mainly responsible for receiving the management messages of the cloud management platform master node and converting the received messages so that the message sending module can identify them. . In this module, an interface will be provided to the cloud management platform to receive messages sent by the cloud management platform or cloud administrators to be sent to end users of virtual machines, because the received messages are text strings or an organic combination of pictures and strings form, and the communication between the VNC server and the client is transmitted through the image, so the message conversion module needs to convert the text string message into an image, and then read out the image content in the bitmap pixel data format to a specific In the file, it serves as the message source of the message sending module; at the same time, after receiving the coordinates representing the end user's operation sent back by the message feedback receiving module, it is converted into the corresponding specific operation according to the coordinates, and finally the end user feedback result is sent back to Cloud management platform or cloud administrator.

Message sending module: The message sending module is located in the qemu-kvm code on the physical host where the virtual machine is actually located. By modifying the source code of some VNC server functions in qemu-kvm in the KVM virtualization solution (located in qemu-kvm/ui/vnc- jobs.c) to achieve. In the message sending module, first read the message image pixel data generated by the message conversion module, and then find out the pixel format and encoding mode attributes of the VNC connection according to the destination virtual machine of the message to be sent, convert the original message image pixel data, and then Combined with the data structure characteristics of the VNC frame buffer update information frame, the converted message image pixel data is added to the end of the VNC original communication information frame, and then wait for the message end sign, and finally restore the original VNC session communication.

Message feedback receiving module: The message feedback receiving module is located in the qemu-kvm code on the actual physical host where the virtual machine is located. By modifying the source code of the VNC server function in qemu-kvm in the KVM virtualization solution (located in qemu-kvm/ui/vnc .c) to achieve. It is mainly responsible for receiving the interactive operation information of the past message sent by the user to the message sending module. This module will intercept all operation information frames of end users during channel message display, find out the user response to the message channel window according to the event interaction information frame structure, and then send the coordinates of user operations to the message conversion module by means of a named pipe , and at the same time send a message area update event to the message sending module to end the display of this message in the channel.

The implementation process of the above message conversion module architecture is shown in Figure 2:

Step 1: First, read the content of the message sent by the administrator and the typesetting and layout information of the message channel according to the parameters set by the administrator calling the VNC covert channel interface;

Step 2: Enter the window configuration information completion module based on the configuration information read in step 1. In the window configuration information completion module, query the message window layout template according to the template model set by the administrator, and complete the VNC hidden channel called by the administrator Parameter information not configured at the time;

Step 3: Generate a temporary message window according to the completed message window configuration information in step 2 (the appearance of the message window is the same as that of the channel message window seen by the final remote terminal user on its own VNC client);

Step 4: Then grab the image information of the message window generated in step 3, and generate the corresponding message window bmp screenshot;

Step 5: Read the bmp image information generated in step 4, and convert the image information into a 32-bit true-color image pixel data file using RAW encoding, so that the subsequent message sending module can read it;

Step 6: At the same time, monitor the end user's selection result for the channel message sent back by the message feedback receiving module, and send the specific content of the end user's selection result to the cloud management platform after the message conversion module parses and processes it. end.

The implementation process of the above message sending module architecture is shown in Figure 3:

Step 1: Find the code generated by the raw data of the server during the communication between the VNC server and the client. In qemu-kvm, this part is located in the vnc_worker_thread_loop function under qemu-kvm/ui/vnc-jobs.c. In this function Add code to perform the following steps;

Step 2: read the message image pixel data generated by the message conversion module;

Step 3: Obtain the pixel format and encoding method used in the current VNC connection process;

Step 4: Further convert the message image pixel data read in step 1 into the pixel format and encoding method used in this VNC connection process;

Step 5: Combining the data structure of the desktop image update information frame (as shown in Figure 4), add the pixel data in the rectangular area of the message image converted in step 4 to the back of the normal image update information frame, so that the VNC client receives the information frame After that, when drawing on its own terminal display, it will be able to draw the message window transmitted in the message channel at the same time.

The workflow of the above message feedback receiving module is shown in Figure 5:

Step 1: Find the code for the server to receive the feedback data from the client terminal user during the communication process between the VNC server and the client. In qemu-kvm, this part is located in the vnc_client_read function under qemu-kvm/ui/vnc.c, in Add code to this function to perform the following steps;

Step 2: Determine whether it is in the display period of the covert channel message, if so, intercept the interactive information frame sent from the client in the current session connection, otherwise it indicates the original communication between the VNC server and the client, and the message feedback module does not perform additional operations at this time ;

Step 3: Referring to Figure 6, judge the object (channel message or access system) targeted by the user in this operation according to the position of the mouse operation coordinates in the intercepted interaction information frame. If the mouse operation is within the rectangular area where the message window is located, it indicates The object of the user's mouse operation is the message channel window;

Step 4: After receiving the interactive information frame for the channel message, send the specific content of the operation to the message conversion module program on the cloud service provider node, and the message conversion module will send the final content to the original sender of the channel message ( Generally, it refers to the cloud management platform control node).

Step 5: Change the interaction information frame to an image update information frame that updates the rectangular area where the current message window is located, that is, generate a message area update event, update the screen area where the message window is located, and complete an interaction;

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the present invention or go beyond the definition of the appended claims range.

Claims (4)

1. the method for building up of VNC concealed channel between a cloud management platform and virtual machine terminal use, this VNC concealed channel comprises following three modules:

Message conversion module: message conversion module is positioned on the physical host at the actual place of virtual machine, be independent of the QEMU module in the KVM framework, cloud platform invoke VNC is provided the interface of concealed channel, the origination message of cloud platform management person being desired to send to the terminal use generates the path message window dialog frame that the keeper sets, grasp this video in window Pixel Information, convert pixel format and the coded system that to identify in the general VNC communication process to; Simultaneously also after receiving terminal use's feedback that the message feedback receiver module sends over, the user is passed to cloud platform management person to the operation of message channel;

Message transmission module: message transmission module is arranged in the QEMU block code of the KVM framework on the physical host of the actual place of virtual machine, by revising the inside of the QEMU module in KVM framework part of V NC service end function source code in the KVM virtualization solution, add the message transmission module source code, the message pixel data of the keeper being desired to mail to the terminal use in revising code converts the form that uses in time VNC connects, seamless interpolation enters in original VNC service end and the client communication frame message then;

The message feedback receiver module: the message feedback receiver module is arranged in the QEMU block code of the KVM framework on the physical host of the actual place of virtual machine, by revising VNC service end function source code in the inside of the QEMU module in the KVM framework in the KVM virtualization solution, add the message feedback receiver module, grasp message terminal use's during end-user desktop shows mouse action in code, the mouse action information that is positioned at path message window viewing area that the terminal use is sent mails to message conversion module by the mode of named pipes.

2. according to the method for building up of VNC concealed channel between the cloud management platform described in the claim 1 and virtual machine terminal use, it is characterized in that, described message conversion module is positioned at cloud service to be provided on the node, and it is the physical host at the actual place of virtual machine that described cloud service provides node; This message conversion module is independent of the QEMU modular program in the KVM framework, is the calling interface that the VNC concealed channel outwards provides, and its realization flow may further comprise the steps:

Step 1: at first the parameter of calling the platform interacting message interface setting of VNC concealed channel according to the keeper reads message content and the message channel composing layout information that the keeper sends over;

Step 2: after the message conversion unit receives these configuration informations that step 1 reads, call window configuration information completion unit module, the masterplate model query messages window layout masterplate unit of in window configuration information completion module, setting according to the keeper, the parameter information that the completion keeper does not dispose when calling the VNC concealed channel;

Step 3: generate an interim message window according to the message window configuration information after step 2 completion, described interim message window outward appearance and finally remote terminal user see that in himself VNC client the path message window is identical;

Step 4: then grasp the image information of the message window of step 3 generation, generate corresponding message window bmp sectional drawing picture;

Step 5: the bmp image information that read step 4 generates converts this image information the use RAW image encoded pixel data file of 32 true color to, so that message transmission module afterwards reads;

Step 6: meanwhile receive user feedback unit monitoring information feedback receiver module and transmit the terminal use that returns at the selection result of this path message, this message conversion module to dissection process after the particular content of terminal use's selection result is transmitted toward the original transmitting terminal of cloud management platform message.

3. according to the method for building up of VNC concealed channel between the cloud management platform described in the claim 1 and virtual machine terminal use, it is characterized in that, described message transmission module is to realize that by the frame buffer update information frame of revising in the communication process its realization flow may further comprise the steps:

Step 1: find the code that the service end initial data generates in VNC service end and the client communication process, in the QEMU module in the KVM framework, this part is arranged in vnc_worker_thread_loop function under the qemu-kvm/ui/vnc-jobs.c, adds code and carry out following steps in this function;

Step 2: message image pixel reading unit reads the message image pixel data that message conversion module produces;

Step 3: obtain employed pixel format and coded system in time VNC connection procedure;

Step 4: then the message image converting unit message image pixel data that begins to read in the step 1 further is converted into employed pixel format and coded system in this VNC connection procedure;

Step 5: in conjunction with the data structure of desktop picture lastest imformation frame, pixel data adds normal image update information frame back in the message image rectangular area after message image pixel data adding device transforms step 4, after the VNC client is received this information frame like this, when drawing, himself terminal display can draw out the message window that transmits in the message channel simultaneously.

4. according to the method for building up of VNC concealed channel between the cloud management platform described in the claim 1 and virtual machine terminal use, it is characterized in that described message feedback receiver module realization flow may further comprise the steps:

Step 1: the code that finds service end reception client terminal user feedback data in VNC service end and the client communication process, in the QEMU module in the KVM framework, this part is arranged in the vnc_client_read function under the qemu-kvm/ui/vnc.c, adds code and carry out following steps in this function;

Step 2: judge whether to be in during the demonstration of concealed channel message, then the interactive information frame that time session connection sends over from client is worked as in intercepting in this way, otherwise is indicated as VNC service end and client original communication, and this moment, the message feedback module was not done operation bidirectional;

Step 3: according to the position of mouse action coordinate in the interactive information frame of intercepting and capturing judge this time operate the user at object, described object comprises path message or access system, if mouse action is in the rectangular area at message window place, then show user's mouse action to as if the message channel window;

Step 4: behind the interactive information frame of receiving at path message, the particular content of operating is sent to cloud service the program of the message conversion module on the node is provided, final content is mail to the original transmitting terminal of path message by message conversion module;

Step 5: this interactive information frame is changed to the image update information frame that upgrades rectangular area, current message window place, also namely produce the message region update event, updating message window place screen area is finished once mutual.

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