Mask `hostname`, `whoami` and `date` in builds

[danbst]

Issue description

I've tried to package a tcptrace tool. It was very easy, but during building it injects current hostname, build user and current datetime into executable, thus rendering it non-deterministic.

What is the correct way to handle this? Should I patch inplace or hostname, whoami and date should be replaced with smth immutable in default stdenv?

Steps to reproduce

{ stdenv, fetchurl, libpcap }:

stdenv.mkDerivation rec {
  name = "tcptrace-${version}";
  version = "6.6.7";
  src = fetchurl {
    url = "http://www.tcptrace.org/download/${name}.tar.gz";
    sha256 = null; #nevermind :)
  };
  buildInputs = [ libpcap ];
  patchPhase = ''
    sed -i \
      -e 's/BUILT_USER/"nix"/' \
      -e 's/BUILT_DATE/"start of time"/' \
      -e 's/BUILT_HOST/"everywhere"/' \
     version.c
  '';
  installPhase = ''
    mkdir -p $out/bin $out/man/man1
    install tcptrace $out/bin/tcptrace
    install tcptrace.man $out/man/man1/tcptrace.1
  '';
}

Relevant part of makefile:

    192 # special rule for version.c
    193 # needs to be recompiled EVERY time
    194 #
    195 # If you have problems getting "whoami", "hostname", or "date" to run on
    196 # your machine, just hack in a quick string below in place of the command.
    197 version.o: ${CFILES} Makefile
    198         ${CC} ${CFLAGS} -o version.o -c $(srcdir)/version.c \
    199         -DBUILT_USER="\"`whoami`\"" -DBUILT_HOST="\"`hostname`\"" -DBUILT_DATE="\"`date`\""

[grahamc]

You might check out Debian to see if they have patches fixing this indeterminate issue

[grahamc]

https://sources.debian.net/src/tcptrace/6.6.7-5/debian/patches/bug829714-reproducible_builds/

[abbradar]

We might want to use CLONE_NEWUTS in Nix instead and set some bogus hostname. whoami is already handled (not sure though but I think the user is always root or nixbld1 now). That leaves only date.

[abbradar]

Looking through Nix's source code we already use CLONE_NEWUTS -- nice!

[bjornfor]

Perhaps use faketime (from libfaketime package)?

[tilpner]

Could we have a setup hook that sets LD_PRELOAD or DYLD_INSERT_LIBRARIES (depending on platform) to use libfaketime (with SOURCE_DATE_EPOCH) everywhere? It seems more robust than hunting and patching every last place that sets dates.

[stale[bot]]

Thank you for your contributions.

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[davidak]

The best solution would be that upstream stops doing that. It's not that useful, especially when we add arbitrary values in our build.

[stale[bot]]

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

[rnhmjoj]

The best solution IMHO is to remove the nondeterminism at the source with something like hermit, so no matter what upstream does, the result is going to be reproducible.