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pam -> use NixOS suid unix_chkpwd wrapper #106285

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pam -> use NixOS suid unix_chkpwd wrapper #106285

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jcumming
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@jcumming jcumming commented Dec 7, 2020

Motivation for this change

Non-root applications that use PAM to check auth credentials need a suid helper application to access /etc/shadow.

NixOS creates this wrapper at /run/wrappers/chkpwd, this patch the pam_unix security module to use the suid wrapper. It provides a function argument to allow overriding the chkpwd to use.

Things done
  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
  • 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 nixpkgs-review --run "nixpkgs-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • Determined the impact on package closure size (by running nix path-info -S before and after)
  • Ensured that relevant documentation is up to date
  • Fits CONTRIBUTING.md.

@jcumming jcumming mentioned this pull request Dec 7, 2020
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@povik
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povik commented Feb 5, 2021

It seems PAM already uses the suid wrapper, there's a symbolic link.

@jcumming
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jcumming commented Feb 6, 2021

Ooops. I forgot about this....

After a bit more research into what unix_chkpwd actually does, it is only suitable for:

  • a user checking their own passwd
  • root checking a password

This doesn't do what I want; I'll have to figure something else out. Closing.

@jcumming jcumming closed this Feb 6, 2021
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2.status: merge conflict 10.rebuild-darwin: 0 10.rebuild-linux: 501+ 10.rebuild-linux: 5001+
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