nixpkgs/pkgs/stdenv/generic
Maximilian Bosch aaeeef5b6c
stdenv: fix custom hardening settings when using __structuredAttrs = true;
Replaces / Closes #353131

A while ago `postgresql` switched to using structured attrs[1]. In the
PR it was reported that this made postgresql notably slower when
importing SQL dumps[2].

After a bit of debugging it turned out that the hardening was entirely
missing and the following combination of settings was the culprit:

    hardeningEnable = [ "pie" ];
    __structuredAttrs = true;

I.e. the combination of custom hardening settings and structured attrs.

What happened here is that internally the default and enabled hardening
flags get written into `NIX_HARDENING_ENABLE`. However, the value is a list
and the setting is not in the `env` section. This means that in the
structured-attrs case we get something like

    declare -ax NIX_HARDENING_ENABLE=([0]="bindnow" [1]="format" [2]="fortify" [3]="fortify3" [4]="pic" [5]="relro" [6]="stackprotector" [7]="strictoverflow" [8]="zerocallusedregs" [9]="pie")

i.e. an actual array rather than a string with all hardening flags being
space-separated which is what the hardening code of the cc-wrapper
expects[3].

This only happens if `hardeningEnable` or `hardeningDisable` are
explicitly set by a derivation: if none of those are set,
`NIX_HARDENING_ENABLE` won't be set by `stdenv.mkDerivation` and the
default hardening flags are configured by the setup hook of the
cc-wrapper[4].

In other words, this _only_ applies to derivations that have both custom
hardening settings _and_ `__structuredAttrs = true;`.

All values of `NIX_HARDENING_ENABLE` are well-known, so we don't have to
worry about escaping issues. Just forcing it to a string by
concatenating the list everytime solves the issue without additional
issues like eval errors when inheriting `env` from a structuredAttrs
derivation[5]. The price we're paying is a full rebuild.

[1] https://github.com/NixOS/nixpkgs/pull/294504
[2] https://github.com/NixOS/nixpkgs/pull/294504#issuecomment-2451482522
[3] cf3e5d3744/pkgs/build-support/cc-wrapper/add-hardening.sh (L9)
[4] cf3e5d3744/pkgs/build-support/cc-wrapper/setup-hook.sh (L114)
[5] 1e84a7fb95
2024-11-02 22:30:01 +01:00
..
builder.sh
check-meta.nix Revert "pkgs/top-level/config.nix: nixfmt, declare options" 2024-08-05 16:44:45 +00:00
common-path.nix stdenv/common-path.nix: move to stdenv/generic/ 2022-07-29 18:24:00 -04:00
default-builder.sh treewide: refactor .attrs.sh detection 2023-10-04 18:36:57 +02:00
default.nix stdenv: set NIX_DONT_SET_RPATH_FOR_TARGET on Darwin 2024-07-13 17:54:35 -04:00
make-derivation.nix stdenv: fix custom hardening settings when using __structuredAttrs = true; 2024-11-02 22:30:01 +01:00
meta-types.nix stdenv/check-meta: Use bespoke type checking 2023-12-26 15:14:42 +13:00
setup.sh pkgs/stdenv/generic/setup.sh: lint with ShellCheck (#351849) 2024-11-01 08:52:44 -07:00