Calling a C++ function with root privileges, without executing the whole program as root

Question

At the moment I am playing around with bluetooth LE and iBeacon devices. I wrote an Server that keeps looking for nearby beacons.

My server follows this example (Link)

Unfortunately calling the function:

hci_le_set_scan_parameters()

requires root privileges.

As I don't want to run the whole server with root privileges I wanted to ask if there is any possibility for calling only this function with root privileges?

I am aware that asking for sudo when executing a program is always at least questionable I could not find any other possibility to scan for iBeacons. If there is another possibility I am happy to hear about it as well.

Thanks for your help and kind regards

nPLus

Answer 1

According to POSIX, UID/GID are process attributes. All code inside your process is executed with UID/GID currently set for the whole process.

You could start server as root and immediately drop root privileges. Then, you can temporary gain root privileges using seteuid(2) when executing your function.

See also this answer.

You can also gain only selected capabilities(7) instead (temporary or permanently).

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Thread-safety note

AFAIK, on Linux UID/GID are per-thread attributes and it's possible to set them for single thread, see NOTES section in seteuid() man-page and this post.