I am working on app (c++) that consist from two parts.
Control Panel working under restricted user account (with UAC enabled)
Windows Service, performing some useful tasks
I need to collect user preferences in control panel and send them to service.
What is the best method for sending/receiving data from control panel to service?
The sockets and named pipes are good, but they may cause windows firewall to show security warnings.
Shared memory also is good, but it requires a lot of synchronization between sending and receiving threads.
Is there any other method that I can use?
Thanks,
Khachatur
Shared memory requires three extra mutex objects on each side. Not so much. If you don't want to write anything, our MsgConnect (open-source) implements MMF transport and has a sample of communicating between the service and the UI application.
Related
I am writing a Desktop application for professional users using C++. My current design relies on a third-party C++ component whose API is based on TCP/IP. To integrate this component might involve modifying it to replace the networking code with a conventional C++ API.
It would be a lot easier if I could leave the component unmodified and communicate with it in the way it expects - over the network. To do so I would need to run the component as a server listening on some high port for loopback connections.
I have two concerns with this loopback approach. Can anyone allay or confirm my fears?
Reliability and performance
The loopback connection might fail, be blocked or intercepted by antivirus software. Something like this: Loopback connections working in user's context but not working from Local System account
Security
I am not too concerned about someone sniffing my loopback packets but I don't want my server to become a security risk itself. Is it risky to have a process listening on some high port?
Do many desktop applications operate like this?
I am initially developing on Windows but may move to Mac and Linux in future so this question applies to all the common desktop OSs.
Reliability: if component itself is reliable then there's no problem with listening to loopback interface. If component is not reliable then it's better to talk with it via loopback interface instead of calling it's functions directly. You can easily handle disconnects and restart component to continue working, but if you would link to the component and component will fail - your app will fail too.
Performance: There's some performance penalty. Not really big with current CPU power. It should be acceptable for most applications.
Security: component should bind to localhost address to avoid security issues. But local 3-d party software (virus) software with sufficient access level can intercept or even modify communication streams. Same for any other method of communication.
Loopback connections are widly used (java uses it for intercommunication, named used it for master service control, etc.)
I have a C++ Win32 application that was written as a Windows GUI project, and now I'm trying to figure out to make it into a Service / GUI hybrid. I understand that a Windows Service cannot / should not have a user interface. But allow me to explain what I have so far and what I'm shooting for.
WHAT I HAVE NOW is a windows application. When it is run it places an icon in the system tray that you can double-click on to open up the GUI. The purpose of this application is to process files located in a specified directory on a nightly schedule. The GUI consists of the following:
A button to start an unscheduled scan/process manually.
A button to open a dialog for modifying settings.
A List Box for displaying status messages sent from the processing thread.
A custom drawn window for displaying image data (the file processing includes the creation and saving of images).
A status bar - while a process is not running, it shows a countdown to the next scheduled scan. During a scan it also provides some status feedback, including a progress bar.
WHAT I'M SHOOTING FOR is a service that will run on boot-up and not require a user to login. This would consist of the scheduled file processing. However, when a user logs in I would still like the tray icon to be loaded and allow them to open up a GUI as I described above to monitor the current state of the service, change settings, start a scan manually, and monitor the progress of a scan.
I'm sure that I have seen applications like this - that function as a service even when I'm not logged in, but still give me a user interface to work with once I do log in.
I'm thinking that instead of having a single multi-threaded application that sends messages to the GUI thread from the processing thread, I need two applications - a Service to perform the processing and a GUI application to provide visual feedback from the Service and also send messages to the Service (for example, to start a scan manually). But I am new to Windows Services and have no idea how this is done.
It is also possible that I'm completely off base and a Service is not what I'm looking for at all.
Any help / ideas / suggestions would be greatly appreciated! Thank you.
You can't do this as a service.
You'll need to make your Windows Service as a normal service application. This will startup on system startup, and run the entire time the system is up.
You'd then make a completely separate GUI application, which "talks" to the service. This can be set to run when a user logs in, in the user's account.
In order to make them "talk" to each other, you'll need to use some form of IPC. Since these run on the same system (but in different accounts, typically), named pipes or sockets both work quite well.
There is a simple way of doing it.
You can’t have the service access any user’s session (session 1,2,3..) since services are isolated and can access session 0 only. This is a change from 2011.
You should write a win32 program to be launched by your service per each user who logs in using https://msdn.microsoft.com/en-us/library/windows/desktop/ms682429(v=vs.85).aspx
The service can continue performing any task that isn’t user specific.
What would be the simplest way for an application I'm writing to block all Internet access on a Windows machine?
More details:
Windows: XP or higher
Application: A basic Win32 app written in C/C++.
Blocking: It needs to be able to block and unblock at will, ideally in a way that the user can't easily reverse. (By, say, right clicking on a network connection icon in the system tray.) Also, ideally, I'd like the method it uses to allow access to be restored should the user restart Windows or reset the machine, though I'd also be willing to have the app auto launch with Windows and unblock access upon startup if the machine was reset while in a blocked state.
Internet access: Primarily, I'd like to block conventional browsers from hitting conventional http/https sites. Secondarily, it would be nice to block IM clients and client-side social networking apps. It would also be nice, but not required, to still allow local networking for file sharing, etc. (Note that only the first requirement is absolute.)
Final notes: This is not meant to be a security utility, nor will its relationship to the user be adversarial (as, for example, with a parental control utility) so it's not important for it to use a scheme that can't be worked around by a determined user. (Consider that I intend for a reboot or reset to clear the blocking. This means that any workaround a user might discover that would take more effort than this is okay.)
Thanks!
p.s. I suspect that the Windows Firewall API won't work for me because this needs to work for users that haven't enabled the firewall or don't have admin privileges, but I'll be thrilled if I'm corrected on this.
It sounds like you're intending to run applications that you don't want to access the internet. Perhaps you could run them inside a virtual machine such as VirtualBox with networking disabled.
You could do it with a Winsock SPI. The Windows SDK has a sample (under Samples\netds\winsock\lsp) which implements what is called a layered service provider which allows you to hook all the user mode functions provided by Winsock and reject/modify the calls to block network access or redirect traffic to different locations. All installed winsock applications will be affected, so in your code you could have policys for what applications can go out and the like and disabled/enable on the fly. Now a determined person could find ways around this but it would be a pain.
That said this isn't trivial to do but the sample should get you most of the way there.
You cannot effectively or practically write your tool with only a user mode application.
What you need to write is a network I/O stack filter driver. This done by writing a Windows Driver. This is different from a Windows Win32 application. Drivers run in kernel mode and applications run in user mode.
On Windows Vista and later, the kernel mode Network Programming Interface (NPI) is designed for this. This is the same API that Windows Firewalls use. These are sometimes called the Winsock kernel (WSK) APIs.
In effect, you are writing a network firewall (more or less)
here are some links
Introduction to Winsock Kernel (WSK)
Windows Core Networking Blog
The Network Programming Interface Docs on MSDN
Note, your will likely need at least two components
Your driver
A Graphical application that a person can use to control your tool
If you want to do any monitoring, you will likely need a user mode service that collects data from your driver. This works better than trying to do this in the driver. In general, you should do the minimal amount of work in the driver.
A few notes:
You need to be very conscious of security when writing this kind of software. This is very much non trivial. Software that is network facing has the highest security requirements.
Be cognizant of performance.
Your driver and/or service must be aware of the context of a calling application. This is also a security boundary. For example, an application not running as administrator should not be able to control your driver.
take a look at firewall sourcecodes
I have written a Windows service that allows me to remotely run and stop applications. These applications are run using CreateProcess, and this works for me because most of them only perform backend processing. Recently, I need to run applications that present GUI to the current log in user. How do I code in C++ to allow my service to locate the currently active desktop and run the GUI on it?
Roger Lipscombe's answer, to use WTSEnumerateSessions to find the right desktop, then CreateProcessAsUser to start the application on that desktop (you pass it the handle of the desktop as part of the STARTUPINFO structure) is correct.
However, I would strongly recommend against doing this. In some environments, such as Terminal Server hosts with many active users, determining which desktop is the 'active' one isn't easy, and may not even be possible.
But most importantly, if an application will suddenly appear on a user's desktop, this may very well occur at a bad time (either because the user simply isn't expecting it, or because you're trying to launch the app when the session isn't quite initialized yet, in the process of shutting down, or whatever).
A more conventional approach would be to put a shortcut to a small client app for your service in the global startup group. This app will then launch along with every user session, and can be used start other apps (if so desired) without any juggling of user credentials, sessions and/or desktops.
Also, this shortcut can be moved/disabled by administrators as desired, which will make deployment of your application much easier, since it doesn't deviate from the standards used by other Windows apps...
The short answer is "You don't", as opening a GUI program running under another user context is a security vulnerability commonly known as a Shatter Attack.
Take a look at this MSDN article: Interactive Services. It gives some options for a service to interact with a user.
In short you have these options:
Display a dialog box in the user's session using the WTSSendMessage function.
Create a separate hidden GUI application and use the CreateProcessAsUser function to run the application within the context of the interactive user. Design the GUI application to communicate with the service through some method of interprocess communication (IPC), for example, named pipes. The service communicates with the GUI application to tell it when to display the GUI. The application communicates the results of the user interaction back to the service so that the service can take the appropriate action. Note that IPC can expose your service interfaces over the network unless you use an appropriate access control list (ACL).
If this service runs on a multiuser system, add the application to the following key so that it is run in each session: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run. If the application uses named pipes for IPC, the server can distinguish between multiple user processes by giving each pipe a unique name based on the session ID.
WTSEnumerateSessions and CreateProcessAsUser.
Several people suggested WTSEnumerateSessions and CreateProcessAsUser. I wonder why no one suggested WTSGetActiveConsoleSessionId, since you said you only want to target one logged in user.
Several people sure are right to suggest CreateProcessAsUser though. If you call plain old CreateProcess the way you said, then the application's GUI will run with your service's privileges instead of the user's privileges.
That problems Session 0 , Interactive Services ,
Windows Service Allow Service To Interact With Desktop
on Windows 7 or Windows Vista
You can read this article
http://www.codeproject.com/KB/vista-security/SubvertingVistaUAC.aspx
I try explained here it's working on Windows 7
On Win2K, XP and Win2K3 the console user is logged on in Session 0, the same session the services live in. If a service is configured as interactive, it'll be able to show the UI on the user's desktop.
However, on Vista, no user can be logged on in Session 0. Showing UI from a service there is a bit trickier. You need to enumerate the active sessions using WTSEnumerateSessions API, find the console session and create the process as that user. Of course, you need also a token or user credentials to be able to do that. You can read more details about this process here.
I think as long as you have only one user logged in, it will automatically display on that user's desktop.
Anyway, be very careful when having a service start an exe.
If the write access to the folder with the exe is not restricted, any user can replace that exe with any other program, which will then be run with sytem rights. Take for example cmd.exe (available on all windows sytems). The next time the service tries to start your exe, you get a command shell with system rights...
If you launch a GUI from your service it will show up on the currently active desktop.
But only if you adjusted the service permissions: You need to allow it to interact with the desktop.
Important Services cannot directly interact with a user as of Windows Vista. Therefore, the techniques mentioned in the section titled Using an Interactive Service should not be used in new code.
This is taken from : http://msdn.microsoft.com/en-us/library/ms683502(VS.85).aspx
I want to have an application or service that is running that, on some schedule, can disable access to the internet for all applications except for specific ones.
I'm trying to create a filter that can be turned on or off under programmatic control. Not just IP addresses and ports, but I want to be able to block specific applications as well, much like Zone Alarm and other software firewalls let you block.
For example, iexplore.exe, skype.exe, firefox.exe, aim.exe. But still need to allow other applications to connect as needed.
It has to work on Vista as well as XP, but I kind of expect that the method will be different on each of those platforms.
Basically, the filter has to tie the network communication back to the executable that is making the request and then allow or deny it.
Update:
On Vista at least, it looks like I want to use filters in the ALE layers of the WFP.
On XP, I'm still looking for the best way to do it. Do I really need to be writing device drivers and dealing with kernel stuff? I'm just a lowly application developer. Kill me now.
Update 2:
Currently looking at the PfCreateInterface and related Pf* API's for pre-Vista systems.
You can change both Vista and XP's firewall policies dynamically using the INetFwAuthorizedApplications interface from the Windows Firewall API.
Also see this question.
You'll have to write a device driver that filters traffic based on the executable requesting the traffic.
by limiting its access to internet using firewall. go to firewall setting advanced tab (win 7)
and do that
I'm not sure, but I think you'd need to do it by getting the program to run as a user that has limited permissions, the question is, can you make a user account that stops such things?
You'll need to redirect all (or at least many) calls to the WinSock API functions of any running program to your own replacement functions. That means getting into the memory of each running program and hijacking those functions, which is an... interesting... exercise. :-)
That might be enough of a pointer to get you started, or at least to suggest some more specific questions to ask.
Could you move aside (ie rename) the system's winsock DLL and replace it with your own ?
Yours should provide the same API, but check the the process name of incoming requests... return an error code to blocked applications and forward the calls from allowed apps onto the real DLL.