I'm trying to run a bluetooth server program on Linux
In order for my client device to find the server, I need to register my service profile on sdp
My code is basically similar to code on this page
The problem is that I need to get root privilege in order to make sdp_connect succeed
When running as a normal user, sdp_connect always returns NULL
Because the other part of my code requires a normal user (not root) environment, I'm wondering if I can make sdp_connect and the following sdp_record_register succeed without root access
Update
Just found a possible solution here
I'm using Bluez5 and sdp_connect seems to be deprecated Bluez4 function, so I need to run the service in compatibility mode
Now it works, and it gives access of /var/run/sdp to all
Just not sure if it is safe to give such permanent access
As you rightly note, there have been 8 tools marked as deprecated as they are no longer maintained or have been replaced by other tools.
Running with --compat would seem like a quick fix rather than a long term solution.
The supported APIs are Bluetooth Management API which is focused towards system level functions.
The application level is accessed through D-Bus and is spread over several documents in https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc
Adapter, Device, GATT, and profile are some of the common ones depending what you are trying to do.
Looking at the bluetoothctl source code can give some examples of how to use these APIs with C.
There are more examples in the test directory but they are in Python:
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/test
Related
What I'am trying to do
I made a keylogger by reading the event file, but it needs root permission to work.I want to make a keylogger that can work without root permission.
My device
ubuntu16.04 using X11
ubuntu21.04 using Wayland
My thoughts
I understand that it is feasible on windows, and it can also be implemented through Xlib on some linux using X11.
But my project needs to run on X11 and Wayland, so it's obviously not possible to use Xlib.
Question
Is there any other way that I can get key logged without root permission?
It may be possible, but any non root solution will depend on the keyboard virtualization tool. Let us look how (modern) OS work:
the hardware is under the exclusive control of the kernel and its drivers. It is possible to implement a keylogger at that level that would only be kernel dependent but it requires admin privileges.
if you have a multiple windows capable system (X11, XWindow) the OS passes low level events to the window manager which in turn will passes them to the client program. In Windows that part is include in the kernel for historical reasons. Here again it is possible to implement a (still low level) keylogger, but if the window manager has been started as root, interacting with it as a whole still requires admin privileges. At least the X11 server can be started as a non admin user process and in that use case, the keylogger can also run under the same user.
at the end, the window manager passes events to the client application. On some (windowing) sytems, it is possible to implement hooks but they will be restricted to the same process or process group or at least the same user. Whether it is possible or not, and the way to implement it if possible will be anyway window manager dependant.
That means that it may be possible to implement a user level keylogger, but it will depend on the windowing system and not only on the kernel. Said differently, you will have to search for a Wayland specific way and a X11 specific way if you want to support both of them.
Link to the bug report on 'Feedback Hub'
An audio endpoint device, from here on referred to as 'endpoint', is a physical or virtual audio output or input device.
With the Windows 10 April Update 1803 the long overdue 'App volume and device preferences' have been introduced. These settings allow more control over audio stream management as it is now possible to set different endpoints for different applications, no matter whether that particular application comes with an endpoint selection or not.
However, there is an issue where the audio of a program, whose endpoint is non-default, is streamed through the default endpoint (or not at all) after it has been closed and launched again, although the endpoint is displayed correctly in the settings:
As far as I know the issue can be recreated on a Windows 10 machine (version 1803 or higher) with any virtual or physical endpoint and an affected program. I used 'VLC Media Player' in this example (disregarding the fact that it comes with an endpoint selection) as it is well known and widely accessible, which should make it easier to recreate the issue.
What I'm searching for...
... is a programmatically solution to switch between endpoints, which ideally can be launched in form of a script to set the correct endpoint with an application launch.
For my purpose it would be enough to have to adjust the device instance path manually, as the device would be always the same, but I'm not going to complain about a solution which retrieves the device instance path from the registry, too.
Defined endpoints and the device instance path of the device they are using can be retrieved from the subkeys of the key HKEY_USERS\# YOUR SID #\Software\Microsoft\Multimedia\Audio\DefaultEndpoint. I don't know how windows generates the name of the subkeys or where they can be found. If I had to take a wild guess, I'd say these are Application IDs (feel free to correct me if I'm wrong).
The device instance path itself can be found in the Device Manager (under 'Audio inputs and outputs' double click the desired device, navigate to the tab 'Details' and select 'Device instance path' from the 'Property' drop-down menu).
Additionally the entry about Audio Endpoint Devices and Stream Management in the Microsoft Docs might be helpful, but that is way above my head.
A possible but impractical workaround...
... would be, to manually set another endpoint for the application and switch back to desired endpoint at every launch of said application (as shown above).
But not just takes this at least 10 seconds at each and every launch, you might even forget to do this as the audio might just get streamed through the default endpoint *¹.
The alternative to the latter is, that no audio will be streamed at all *² or in some cases it actually works *³.
*¹ e.g.: VLC Media Player, Tom Clancy's Rainbow Six Siege (although the audio will be streamed correctly during the splash screens)
*² e.g.: Call of Duty 4: Modern Warfare, Call of Duty: Modern Warfare 2, Call of Duty: Modern Warfare 3
*³ e.g.: Window Media Player, Microsoft Edge, Firefox
Observations
VLC Media Player comes with an endpoint selection, but so does TeamSpeak 3 and, unlike VLC, it skips the Windows settings completely.
Call of Duty not streaming any audio most likely is connected to the engine as I didn't encounter any other application doing something similar.
Windows Media Player, Microsoft Edge and Firefox are the only programs (I tested so far) which work fine. They have no endpoint selection (I'd know of) and will use the correct endpoint after closing and launching it again. It should be noted, however, that Firefox and Microsoft Edge will show multiple instances in the "App volume and device preferences" when adjusting the endpoint.
Disclaimer
I already tried two 3rd party softwares: 'Audio Router', which didn't work at all and 'CheVolume', which doesn't solve the issue and constantly crashes while doing so.
This question is based on one I asked over at Super User (here), where I didn't get an answer I was able to work with due to my lack of knowledge regarding actual programming (I'm only somewhat familiar with Batch and PowerShell). I'm well aware that neither Stack Overflow nor Super User are script writing services, however, the issue is not being fixed with the Windows 10 October Update 1809 and I see this as a problem which is affecting not just me and with that would be helpful for multiple people after me. Feel free to write a comment or propose an edit if you see this differently.
I'm also not sure whether the tags 'audio-streaming' and 'endpoint' should be used in this context, please propose an edit if they shouldn't or you can think of any better.
Edit - 05/11/18
Using the 3rd party software 'EarTrumpet' I was able to overcome the issue with the 'Call of Duty' games (no audio at all after restarting), however, 'VLC Media Player' would not restart after I assigned a non-default endpoint with 'EarTrumpet' until I closed 'EarTrumpet' again and the issue with 'Tom Clancy's Rainbow Six Siege' remains the same.
Edit - 18/01/19
Added link to a bug report I created on the 'Feedback Hub' 2 month ago.
Edit - 20/01/19
After doing some testing again it should be noted that having 'EarTrumpet' run in the background will keep a non-default endpoint for 'VLC Media Player' across restarts, however, 'VLC Media Player' will only (reliably) restart when the non-default endpoint was set in the 'App volume and device preferences'.
I do not have any solution regarding a programming language to handle such events.
But I can recommend EarTrumpet app to handle this change more quickly https://www.theverge.com/2018/6/13/17457778/eartrumpet-windows-10-audio-app
(Windows store: https://www.microsoft.com/en-us/p/eartrumpet/9nblggh516xp?ranMID=24542&ranEAID=nOD%2FrLJHOac&ranSiteID=nOD_rLJHOac-hUn6PgKuMKwQLdrzRqnPTA&epi=nOD_rLJHOac-hUn6PgKuMKwQLdrzRqnPTA&irgwc=1&OCID=AID681541_aff_7593_1243925&tduid=%28ir__qwqlg6jd0jba3y9hpnbvikaite2xk6kuyv9udtr100%29%287593%29%281243925%29%28nOD_rLJHOac-hUn6PgKuMKwQLdrzRqnPTA%29%28%29&irclickid=_qwqlg6jd0jba3y9hpnbvikaite2xk6kuyv9udtr100&activetab=pivot:overviewtab )
I will update the answer if I find a easy way to script/program a change of output on each app.
So I need to simulate Isis2 in ns-3. (I am also to modify Isis2 slightly, wrapping it with some C/C++ code since I need at least a quasi real-time mission-critical behavior)
Since I am far from having any of that implemented it would interesting to know if this is a suitable way of conduct. I need to specifically monitor the performance of the consensus during sporadic wifi (ad hoc) behavior.
Would it make sense to virtualize a machine for each instance of Isis2 and then use the tap bridge( model and analyze the traffic in the ns-3 channel?
(I also am to log the events on each instance; composing the various data into a unified presentation)
You need to start by building an Isis2 application program, and this would have to be done using C/CLI or C++/CLI. C++/CLI will be easier because the match with the Isis2 type system is closer. But as I type these words, I'm trying to remember whether Mono actually supports C++/CLI. If there isn't a Mono compiler for C++/CLI, you might be forced to use C# or IronPython. Basically, you have to work with what the compiler will support.
You'll build this and the library on your mono platform and should test it out, which you can do on any Linux system. Once you have it working, that's the thing you'll experiment with on NS/3. Notice that if you work on Windows, you would be able to use C++/CLI (for sure) and then can just make a Windows VM for NS3. So this would mean working on Windows, but not needing to learn C#.
This is because Isis2 is a library for group communication, multicast, file replication and sharing, DHTs and so forth and to access any particular functionality you need an application program to "drive" it. I wouldn't expect performance issues if you follow the recommendations in the video tutorials and the user manual; even for real-time uses the system is probably both fast enough and steady enough in its behavior.
Then yes, I would take a virtual machine with the needed binaries for Mono (Mono is loaded from DLLs so they need to be available at the right virtual file system locations) and your Isis2 test program and run that within NS3. I haven't tried this but don't see any reason it wouldn't work.
Keep in mind that the default timer settings for timeout and retransmission are very slow and tuned for running on Amazon AWS, inside a data center. So once you have this working, but before simulating your wifi setup, you may want to experiment with tuning the system to be more responsive in that setting. I'm thinking that ISIS_DEFAULTTIMEOUT will probably be way too long for you, and the RTDELAY setting may also be too long for you. Amazon AWS is a peculiar environment and what makes Isis2 stable in AWS might not be ideal in a Wifi setting with very different goals... but all of those parameters can be tuned by just setting the desired values in the Environment, which can be done in bash on the line that launches your test program, or using the bash "Export" command.
I want to implement WiFi manager program which should handle the following.
notification on wi-fi access point has come or gone
provide information of available wifi access point
connect/disconnect with a given wi-fi access point
Which is the recommended C/C++ WiFi library for Linux to achieve this?
On Fedora (at least), the preferred way to interact with NetworkManager is via DBus.
While wireless-tools and the like will work — even direct kernel calls, if you must — there are a couple of problems:
You'll probably need superuser privileges
NetworkManager will probably have a panic attack and get into fights with you, unless you stop its service
The user's normal networking controls (e.g. desktop tray icons) are almost certainly configured to use NetworkManager.
You can send and receive DBus messages for all the tasks you mentioned, for WiFi as well as arbitrary other types of network interfaces. The API is published here, for version 0.8.
For newer operating systems, there are apparently changes in the API, with a migration guide.
Their wiki should be really helpful.
I know both Fedora and Ubuntu use NetworkManager by default; I believe many other systems do, as well, but don't have an exhaustive list.
Of course, if you're using an embedded system, custom distribution, or something, then your mileage may vary.
That would be wireless-tools
I would recommend using directly the NetworkManager Library.
You can use low-level D-Bus library or libnm-glib library, that makes communication easier: example add connection glib
For more info, you can take a look into the code of the command line client nmcli.
I would like to restrict people using my application to one Computer, so I was thinking about IP's.. but people in some countries get new IP's after they reboot their Internet.. so I need something better to identify the users, like some value that doesn't change until the user performs a format.
Thanks
The MAC address of e.g. an ethernet interface typically doesn't change even across formats (only if the user changes ethernet interface card). Don't worry, nothing to do with Apple Macs, MAC stands for Media Access Control;-).
You will probably need some registration process, so you could tell the user that you will connect to get some update, and in that process send the serial number of the application and the mac address. If the serial number has already been registered then return an error to the user.
Ideally you should perhaps download some needed dll that is tied to a specific serial number and perhaps mac address, so that if the user copies the dll to a different program it will require more work to get it to work.
It depends on how much you want to inconvenience the user as to the best approach, I believe.
Where I specified dll could be any assembly, jar file, etc, that the language in question uses for running the application.