@villares@ciberlandia.pt
ciberlandia.pt
 (12w ago)

Me: I had a 7-day working sprint I should relax today before I teach a class in the evening…

My brain: Good, as you don’t feel any obligation to work on your PhD today, you should just open the PhD working file and start working on it, no pressure. it will feel nice, I promise!

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movq
www.uninformativ.de
 (12w ago)

OpenBSD has the wonderful pledge() and unveil() syscalls:

https://www.youtube.com/watch?v=bXO6nelFt-E

Not only are they super useful (the program itself can drop privileges – like, it can initialize itself, read some files, whatever, and then tell the kernel that it will never do anything like that again; if it does, e.g. by being exploited through a bug, it gets killed by the kernel), but they are also extremely easy to use.

Imagine a server program with a connected socket in file descriptor 0. Before reading any data from the client, the program can do this:

unveil("/var/www/whatever", "r");
unveil(NULL, NULL);
pledge("stdio rpath", NULL);

Done. It’s now limited to reading files from that directory, communicating with the existing socket, stuff like that. But it cannot ever read any other files or exec() into something else.

I can’t wait for the day when we have something like this on Linux. There have been some attempts, but it’s not that easy. And it’s certainly not mainstream, yet.

I need to have a closer look at Linux’s Landlock soon (“soon”), but this is considerably more complicated than pledge()/unveil():

https://landlock.io/

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