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Unix file access rwx permissions are simple but tricky

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Re: Unix file access rwx permissions are simple but tricky

#21

Post by 0cf8612b2e1e »

jesprenj wrote: post #19
0cf8612b2e1e wrote: post #10

Earlier quoted context omitted.

It took me a shockingly long amount of time before I realized it was silly to have a username on my machines. I am the only person using this, why am I typing unnecessary cruft? Username switched to “a”, which ends up saving space in my home path and terminals.

It took me a shockingly long amount of time before I realized it was silly to have a username on my machines. I am the only person using this, why am I typing unnecessary cruft? Username switched to “root” on all my machines and I remove the username from PS1. /root is shorter than /home/a (:

That requires faith in software not making hard coded assumptions about filesystem structure. Something which I am not prepared to do. How much software still cannot respect XDG?

Re: Unix file access rwx permissions are simple but tricky

#22

Post by IcyWindows »

saulpw wrote: post #7
eadmund wrote: post #3

Earlier quoted context omitted.

Those multiple users could be used to implement sandboxing. And of course if one has a family then one might want accounts for Mom, Dad, Alice and Bob.

The days of multiple family members using the same computer are long gone. Do you ever log into anyone else's desktop/laptop, or does anyone else ever log into yours? That's what I'm getting at.

Yes, my children log into their own accounts to play games and/or do homework on the desktop computer with large monitors and good GPU.

Re: Unix file access rwx permissions are simple but tricky

#23

Post by wruza »

saulpw wrote: post #2

I've been wondering about this for awhile. Do we really need multiple users for desktop unix? I get that you want some division between system and user, to protect the user against themselves. And read-only files are similarly useful, if only because some devices are read-only. But do we really need user/group/other permissions for desktop unix? and all the complexity of groups, and euid, etc. Edit: not sure why I'm…

Yes, we really need users for desktops on all operating systems. Fundamentally limiting a computer to a single user is immeasurably idiotic and I wonder how one comes to that question even.

Somehow it slipped in for phones and that’s a big part of why they suck. E.g. you can’t have work, life, private/second life and tmp/trash accounts on your phone and have to either carry multiple devices or mix lives together.

Re: Unix file access rwx permissions are simple but tricky

#24

Post by ryandrake »

eadmund wrote: post #3
saulpw wrote: post #2

I've been wondering about this for awhile. Do we really need multiple users for desktop unix? I get that you want some division between system and user, to protect the user against themselves. And read-only files are similarly useful, if only because some devices are read-only. But do we really need user/group/other permissions for desktop unix? and all the complexity of groups, and euid, etc. Edit: not sure why I'm…

Those multiple users could be used to implement sandboxing. And of course if one has a family then one might want accounts for Mom, Dad, Alice and Bob.

Yea, I'd like to see a system where each application runs as its own user, especially third party applications not vetted by the OS vendor, the package manager and so on. Maybe this already exists--I think it would be a good step forward for security and privacy.

You can no longer trust 3rd party applications to stay in their lanes. Running an application with full access to everything that I as a user have access to seems insane in 2024. Ideally, I don't want a third party application to read or write anything outside of its "home directory" without my explicitly giving it permission. That includes files on my filesystem, network shares, hardware devices, everything.

Re: Unix file access rwx permissions are simple but tricky

#25

Post by wruza »

saulpw wrote: post #7
eadmund wrote: post #3

Earlier quoted context omitted.

Those multiple users could be used to implement sandboxing. And of course if one has a family then one might want accounts for Mom, Dad, Alice and Bob.

The days of multiple family members using the same computer are long gone. Do you ever log into anyone else's desktop/laptop, or does anyone else ever log into yours? That's what I'm getting at.

I have to clean my grandmas tablet every time my nieces come and screw it up by installing games, moving icons around and setting who knows what.

Re: Unix file access rwx permissions are simple but tricky

#27

Post by candiddevmike »

ratorx wrote: post #16
stefan_ wrote: post #15

Earlier quoted context omitted.

Except they all already use the insanity that is SELinux because they found users and groups too limiting for their "guaranteed to break production at runtime" security scheme. People suggesting we need user accounts for isolation are a generation behind the engineers tasked with papering over security issues.

SELinux is definitely over-engineered, but it’s not for the same problem as file permissions. File permissions are purely for files, whereas increasingly Linux does not nicely follow the philosophy of everything being a file. Once you have non-file resources and capabilities, it is very tempting to attempt to generalise permissions beyond them and if you attempt to bolt it on, you’ll get something like SELinux. I wou…

AppArmor tends to break less because it doesn't resolve around esoteric file metadata for labeling, IME. Keep the policy definitions separate.

Re: Unix file access rwx permissions are simple but tricky

#28

Post by inetknght »

teo_zero wrote: post #18

It's counterintuitive that the owner can have less rights than the others. Honestly, I've never seen it put in practice in any real-world file system. Incidentally, this is also not very efficient: UNIX permissions as they are today require 9 bits, namely rwx for owner, rwx for group, and rwx for others. But in an alternative universe where owner's rights win over group's rights which win over others' rights, permiss…

Alas, you're missing some bits. Sticky bit in particular can be associated to each of those too. There's probably others that I don't remember off the top of my head.

> It's counterintuitive that the owner can have less rights than the others

I completely concur. I've also never seen it used in the wild, but I know about it because I stumbled upon it more than once building scripts and not being careful about what flags are set.

Re: Unix file access rwx permissions are simple but tricky

#29

Post by c-hendricks »

wruza wrote: post #25
saulpw wrote: post #7

Earlier quoted context omitted.

The days of multiple family members using the same computer are long gone. Do you ever log into anyone else's desktop/laptop, or does anyone else ever log into yours? That's what I'm getting at.

I have to clean my grandmas tablet every time my nieces come and screw it up by installing games, moving icons around and setting who knows what.

Right, but you're not logging in to a separate account for that.

Re: Unix file access rwx permissions are simple but tricky

#30

Post by cwillu »

stefan_ wrote: post #15
ratorx wrote: post #6

Earlier quoted context omitted.

User is useful for isolation, not just between system and user, but also between different bits of the system. This is more useful on a server running multiple different services, but desktop software often has multiple services as well (although I can’t think of an example right now). Groups are a bit more niche IMO, but without groups there is no real other way to express the constraint of thing X uses file A,B, th…

Except they all already use the insanity that is SELinux because they found users and groups too limiting for their "guaranteed to break production at runtime" security scheme. People suggesting we need user accounts for isolation are a generation behind the engineers tasked with papering over security issues.

Who is “they?” SELinux is not universal.
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