nixos/wrappers: require argc to be at least one

[sugar700]

setuid applications were exploited in the past with an empty argc, such as pkexec using CVE-2021-4034. In order to avoid the risk of such vulnerabilities in the future, wrapper was updated to prevent calling setuid like this.

See #156750.

Motivation for this change

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[sugar700]

@ofborg test sudo

[xbreak]

@xfix: Does the assertion work in release builds? It very well might, but it seems to me that undefining NDEBUG after <assert.h> has been included, as is done in wrapper.c, won't affect the assert() macro, which is the explicit purpose.

If NDEBUG is defined as a macro name at the point in the source file where <assert.h> is included, the assert macro is defined simply as

    #define assert(ignore) ((void)0)

- http://port70.net/~nsz/c/c89/c89-draft.html#4.2

https://github.com/NixOS/nixpkgs/blob/2b214f0a824bacd87bac1cfe09007a632959a0d4/nixos/modules/security/wrappers/wrapper.c#L1-L22

[sugar700]

Well, the program was using assert like this already, and there is #undef NDEBUG to make sure asserts get compiled. I think it's a weird use of assert, but I don't want to do heavy refactors of this code.

EDIT: Oh, I see what you mean. I will be checking assert.h header and probably do some refactors.

[sugar700]

Created new assert macro that doesn't look at NDEBUG.

[sugar700]

@ofborg test sudo

[github-actions]

Successfully created backport PR #173287 for release-21.11.