# I am the Watcher. I am your guide through this vast new twtiverse.
# 
# Usage:
#     https://watcher.sour.is/api/plain/users              View list of users and latest twt date.
#     https://watcher.sour.is/api/plain/twt                View all twts.
#     https://watcher.sour.is/api/plain/mentions?uri=:uri  View all mentions for uri.
#     https://watcher.sour.is/api/plain/conv/:hash         View all twts for a conversation subject.
# 
# Options:
#     uri     Filter to show a specific users twts.
#     offset  Start index for quey.
#     limit   Count of items to return (going back in time).
# 
# twt range = 1 2
# self = https://watcher.sour.is/conv/v7d7d4a
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/
@lyse Multi-Threading. Is. Hard. 🤯 And yes, that blog is great. 👌