Name: Anonymous 2014-05-24 7:27
Hi /prog/
I recently read this:
http://blog.erratasec.com/2013/12/how-to-disable-webcam-light-on-windows.html
Sinc then I've been trying to figure out how the windows webcam driver works. Specifically I'd like to be able to manually control activation of the LED on the camera.
Here's what I've established so far:
- the default windows driver is usbvideo.sys
- the driver may or may not have the ability to control the LED on webcams (havent established for sure yet)
- I'm using a Logitech webcam. I installed the software/drivers, then replaced the drivers in device manager with the windows default one. The webcam still worked, but the software popped up a message that it was using generic/MS UVC driver. The control for the light inside the logitech application still worked (however I later noticed that the webcam was using an additional logitech driver, so I haven't been able to establish for sure if the windows driver can set the LED, going to check again shortly).
- The logitech app sets a registry key (value LVUVC_LEDControl). Changing this value DOES allow you to control the LED. 0 == off, 1 == on, 4 == auto. This affects all applications (tested it with AMCap too), but it only works the first time you plug in the cam; changing it while the cam is plugged in has no effect.
I don't know much about drivers, decompiling or debugging. I did try and attach a debugger to the logitech app to see what happens when you change the LED setting inside of it, but the debugger couldn't attach to the app and I didn't have any success starting the app as new process via the debugger (the app is launched from another executable), so I'm not sure how/whether to proceed further down that route.
I also tried opening a few of the logitech drivers in PEBrowse and searching for references to 'LED', 'light', 'lamp' etc, but with limited success. Opening USBVideo.sys didn't provide me with much insight either.
What I'd like to achieve is either:
- create a modified version of the usbvideo.sys driver in which the light is always off
- create a small application that allows me to set the light (as I don't know too much about how drivers work, I'm not sure this is plausible)
- ideally create a 2nd driver so I can pick which one to use depending on which application I'm using it in.
What I need to know more about is:
1. which of the above is most plausible?
2. which route(s) should I proceed with: trying to observe the logitech app under the hood to see how it controls the light, trying to get more info on the usbvideo.sys driver (havent been able to find much in terms of documentation), or other?
3. apps/tutorials/protips for 2.
I recently read this:
http://blog.erratasec.com/2013/12/how-to-disable-webcam-light-on-windows.html
Sinc then I've been trying to figure out how the windows webcam driver works. Specifically I'd like to be able to manually control activation of the LED on the camera.
Here's what I've established so far:
- the default windows driver is usbvideo.sys
- the driver may or may not have the ability to control the LED on webcams (havent established for sure yet)
- I'm using a Logitech webcam. I installed the software/drivers, then replaced the drivers in device manager with the windows default one. The webcam still worked, but the software popped up a message that it was using generic/MS UVC driver. The control for the light inside the logitech application still worked (however I later noticed that the webcam was using an additional logitech driver, so I haven't been able to establish for sure if the windows driver can set the LED, going to check again shortly).
- The logitech app sets a registry key (value LVUVC_LEDControl). Changing this value DOES allow you to control the LED. 0 == off, 1 == on, 4 == auto. This affects all applications (tested it with AMCap too), but it only works the first time you plug in the cam; changing it while the cam is plugged in has no effect.
I don't know much about drivers, decompiling or debugging. I did try and attach a debugger to the logitech app to see what happens when you change the LED setting inside of it, but the debugger couldn't attach to the app and I didn't have any success starting the app as new process via the debugger (the app is launched from another executable), so I'm not sure how/whether to proceed further down that route.
I also tried opening a few of the logitech drivers in PEBrowse and searching for references to 'LED', 'light', 'lamp' etc, but with limited success. Opening USBVideo.sys didn't provide me with much insight either.
What I'd like to achieve is either:
- create a modified version of the usbvideo.sys driver in which the light is always off
- create a small application that allows me to set the light (as I don't know too much about how drivers work, I'm not sure this is plausible)
- ideally create a 2nd driver so I can pick which one to use depending on which application I'm using it in.
What I need to know more about is:
1. which of the above is most plausible?
2. which route(s) should I proceed with: trying to observe the logitech app under the hood to see how it controls the light, trying to get more info on the usbvideo.sys driver (havent been able to find much in terms of documentation), or other?
3. apps/tutorials/protips for 2.