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stdenv: fix custom hardening settings when using __structuredAttrs = true;

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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
This commit is contained in:
Maximilian Bosch 2024-11-02 15:49:04 +01:00
parent d32fe41821
commit aaeeef5b6c
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2 changed files with 8 additions and 1 deletions
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2
pkgs/stdenv/generic/make-derivation.nix
View File

@ -413,7 +413,7 @@ else let
enableParallelChecking = attrs.enableParallelChecking or true;
enableParallelInstalling = attrs.enableParallelInstalling or true;
} // optionalAttrs (hardeningDisable != [] || hardeningEnable != [] || stdenv.hostPlatform.isMusl) {
NIX_HARDENING_ENABLE = enabledHardeningOptions;
NIX_HARDENING_ENABLE = builtins.concatStringsSep " " enabledHardeningOptions;
} // optionalAttrs (stdenv.hostPlatform.isx86_64 && stdenv.hostPlatform ? gcc.arch) {
requiredSystemFeatures = attrs.requiredSystemFeatures or [] ++ [ "gccarch-${stdenv.hostPlatform.gcc.arch}" ];
} // optionalAttrs (stdenv.buildPlatform.isDarwin) (

7
pkgs/test/cc-wrapper/hardening.nix
View File

@ -178,6 +178,13 @@ in nameDrvAfterAttrName ({
ignorePie = false;
});
pieExplicitEnabledStructuredAttrs = brokenIf stdenv.hostPlatform.isStatic (checkTestBin (f2exampleWithStdEnv stdenv {
hardeningEnable = [ "pie" ];
__structuredAttrs = true;
}) {
ignorePie = false;
});
relROExplicitEnabled = checkTestBin (f2exampleWithStdEnv stdenv {
hardeningEnable = [ "relro" ];
}) {