David Given David Given - 5 months ago 36
C Question

Dropping root privileges

I have a daemon which gets started as root (so it can bind to low ports). After initialisation I'd very much like to have it drop root privileges for safety reasons.

Can anyone point me at a known correct piece of code in C which will do this?

I've read the man pages, I've looked at various implementations of this in different applications, and they're all different, and some of them are really complex. This is security-related code, and I really don't want to reinvent the same mistakes that other people are making. What I'm looking for is a best practice, known good, portable library function that I can use in the knowledge that it's going to get it right. Does such a thing exist?

For reference: I'm starting as root; I need to change to run under a different uid and gid; I need to have the supplementary groups set up correctly; I don't need to change back to root privileges afterwards.

Ben Ben
Answer Source

You're looking for this article:

POS36-C. Observe correct revocation order while relinquishing privileges

Not sure how to best put some information there without duplicating the content of that page ...