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nixos/etc: sanitize /etc setup script #41276

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nixos/etc: sanitize /etc setup script #41276

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tkerber
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@tkerber tkerber commented May 30, 2018

Fixes #41241

Motivation for this change

Variables passed to the /etc setup script were not shell escaped. This has been changed.
I am not entirely comfortable with the use of eval to construct arrays from the sanitised input, but I haven't found a better approach to convert a string of shell-escaped arguments into an array of strings in bash.

I have tested it myself, however I am not familiar enough with nixos tests to know which ones need to be run for something as low-level as this, and I'm well aware that any change in the /etc setup could break a lot. Any advice on this?

Things done
  • Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
  • Built on platform(s)
    • NixOS
    • macOS
    • other Linux distributions
  • Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
  • Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • Fits CONTRIBUTING.md.

Mic92
Mic92 reviewed May 31, 2018
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nixos/modules/system/etc/make-etc.sh Outdated
modes_=($modes)
users_=($users)
groups_=($groups)
eval "sources_=($sources)"
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What does the value of $sources looks like in that case?

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So this brought to my attention that $sources actually shouldn't be escaped, because it's a list of paths, that when escaped don't get properly imported into the store. It also means the script is passed a list of nix store paths, which are sanitized anyway.

For the others, specifically $target, assuming we have the files foo and bar baz, it would like 'foo' 'bar baz', whereas previously it was foo bar baz.

The eval is safe, as it expands to an array literal of string literals.

@tkerber
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tkerber commented May 31, 2018

While fixing the sanitization of $sources, I realised that I'd missed the globbing section of the script. On looking into it, the globbing section is a) inherently unsanitised, and b) impossible to reach, as it requires a nix store path to have a * in it. I've gone through the history, and it seems to come from a time when the source property was not typed (i.e. could be a string). I therefore think it is safe to remove.

@tkerber
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tkerber commented May 31, 2018 •
edited

Wait, sorry, it still seems to be in use! E.g. In fail2ban.

@mmahut
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mmahut commented Aug 3, 2019

What is the status of this pull request?

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stale bot commented Jun 1, 2020

Thank you for your contributions.
This has been automatically marked as stale because it has had no activity for 180 days.
If this is still important to you, we ask that you leave a comment below. Your comment can be as simple as "still important to me". This lets people see that at least one person still cares about this. Someone will have to do this at most twice a year if there is no other activity.
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@stale stale bot added the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jun 1, 2020
@stammon
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stammon commented Jul 18, 2020

I think the underlying issue has never been fixed, so somebody who is more familiar with this low level of the nixos module system should revisit it and hopefully merge it

@stale stale bot removed the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jul 18, 2020
samuela
samuela approved these changes Sep 23, 2020
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Looks like some of these changes have already made it into make-etc.sh but otherwise LGTM.

@xaverdh
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xaverdh commented Jan 8, 2021 •
edited

Can't we just set __structuredAttrs here and then obtain the values from json with jq?

edit: ah no jq needed, I just discovered .attrs.sh. Sadly, I also just discovered that structured attributes require support in stdenv..

@xaverdh xaverdh mentioned this pull request Jan 8, 2021
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@FRidh
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FRidh commented Jan 8, 2021 •
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you can use toJSON and pass the path to the derivation. In that case its probably clearer to rewrite this script in Python.

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xaverdh commented Jan 8, 2021

you can use toJSON and pass the path to the derivation. In that case its probably clearer to rewrite this script in Python.

I went ahead with the jq appoach: #108779
doesn't look too ugly, but python would be better still ;-)

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I marked this as stale due to inactivity. → More info

@stale stale bot added the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jul 8, 2021
This was referenced Jul 22, 2021
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2.status: merge conflict 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md 6.topic: nixos 8.has: module (update) 10.rebuild-darwin: 0 10.rebuild-linux: 0
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Whitespace in environment.etc target crashes nixos
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@tkerber @mmahut @stammon @xaverdh @FRidh @Mic92 @samuela @ryantm @GrahamcOfBorg