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By default, Perl versions since 5.8.1 use randomization to make hashes resistant to complexity attacks. That randomization makes building VM images such as ubuntu1804x86_64 non-deterministic because the (imported) derivations built by deb/deb-closure.pl are not stable. This can easily be observed by repeating the following sequence of commands and noting the path of the image's .drv: nix-instantiate -E '(import <nixpkgs> {}).vmTools.diskImageFuns.ubuntu1804x86_64 {}' nix-store --delete /nix/store/*ubuntu-18.04-bionic-amd64.nix One source of non-determinism is the handling of Provides/Replaces, which depends on the order of iteration over %packages. Here is a diff showing the corresponding change in output: >>> awk -virtual awk: using original-awk - original-awk: libc6 (>= 2.14) +virtual awk: using mawk + mawk: libc6 (>= 2.14) - mawk: libc6 (>= 2.14) ->>> libc6 This patch sorts packages by name for Provides/Replaces processing, which seems to result in stable output. (If the above turns out not to be sufficient, one could also set the PERL_HASH_SEED and PERL_PERTURB_KEYS environment variables, documented in 'perlrun', to disable Perl's built-in randomization. Complexity attacks are not an issue as we control and trust all inputs.)
181 lines
4.8 KiB
Perl
181 lines
4.8 KiB
Perl
use strict;
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use Dpkg::Control;
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use Dpkg::Deps;
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use File::Basename;
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my $packagesFile = shift @ARGV;
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my $urlPrefix = shift @ARGV;
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my @toplevelPkgs = @ARGV;
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my %packages;
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# Parse the Packages file.
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open PACKAGES, "<$packagesFile" or die;
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while (1) {
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my $cdata = Dpkg::Control->new(type => CTRL_INFO_PKG);
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last if not $cdata->parse(\*PACKAGES, $packagesFile);
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die unless defined $cdata->{Package};
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#print STDERR $cdata->{Package}, "\n";
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$packages{$cdata->{Package}} = $cdata;
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}
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close PACKAGES;
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# Flatten a Dpkg::Deps dependency value into a list of package names.
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sub getDeps {
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my $deps = shift;
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#print "$deps\n";
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if ($deps->isa('Dpkg::Deps::AND')) {
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my @res = ();
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foreach my $dep ($deps->get_deps()) {
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push @res, getDeps($dep);
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}
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return @res;
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} elsif ($deps->isa('Dpkg::Deps::OR')) {
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# Arbitrarily pick the first alternative.
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return getDeps(($deps->get_deps())[0]);
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} elsif ($deps->isa('Dpkg::Deps::Simple')) {
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return ($deps->{package});
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} else {
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die "unknown dep type";
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}
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}
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# Process the "Provides" and "Replaces" fields to be able to resolve
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# virtual dependencies.
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my %provides;
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foreach my $cdata (sort {$a->{Package} cmp $b->{Package}} (values %packages)) {
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if (defined $cdata->{Provides}) {
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my @provides = getDeps(Dpkg::Deps::deps_parse($cdata->{Provides}));
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foreach my $name (@provides) {
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#die "conflicting provide: $name\n" if defined $provides{$name};
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#warn "provide by $cdata->{Package} conflicts with package with the same name: $name\n";
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next if defined $packages{$name};
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$provides{$name} = $cdata->{Package};
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}
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}
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# Treat "Replaces" like "Provides".
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if (defined $cdata->{Replaces}) {
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my @replaces = getDeps(Dpkg::Deps::deps_parse($cdata->{Replaces}));
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foreach my $name (@replaces) {
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next if defined $packages{$name};
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$provides{$name} = $cdata->{Package};
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}
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}
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}
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# Determine the closure of a package.
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my %donePkgs;
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my %depsUsed;
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my @order = ();
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sub closePackage {
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my $pkgName = shift;
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print STDERR ">>> $pkgName\n";
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my $cdata = $packages{$pkgName};
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if (!defined $cdata) {
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die "unknown (virtual) package $pkgName"
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unless defined $provides{$pkgName};
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print STDERR "virtual $pkgName: using $provides{$pkgName}\n";
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$pkgName = $provides{$pkgName};
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$cdata = $packages{$pkgName};
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}
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die "unknown package $pkgName" unless defined $cdata;
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return if defined $donePkgs{$pkgName};
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$donePkgs{$pkgName} = 1;
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if (defined $cdata->{Provides}) {
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foreach my $name (getDeps(Dpkg::Deps::deps_parse($cdata->{Provides}))) {
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$provides{$name} = $cdata->{Package};
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}
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}
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my @depNames = ();
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if (defined $cdata->{Depends}) {
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print STDERR " $pkgName: $cdata->{Depends}\n";
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my $deps = Dpkg::Deps::deps_parse($cdata->{Depends});
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die unless defined $deps;
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push @depNames, getDeps($deps);
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}
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if (defined $cdata->{'Pre-Depends'}) {
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print STDERR " $pkgName: $cdata->{'Pre-Depends'}\n";
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my $deps = Dpkg::Deps::deps_parse($cdata->{'Pre-Depends'});
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die unless defined $deps;
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push @depNames, getDeps($deps);
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}
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foreach my $depName (@depNames) {
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closePackage($depName);
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}
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push @order, $pkgName;
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$depsUsed{$pkgName} = \@depNames;
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}
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foreach my $pkgName (@toplevelPkgs) {
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closePackage $pkgName;
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}
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# Generate the output Nix expression.
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print "# This is a generated file. Do not modify!\n";
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print "# Following are the Debian packages constituting the closure of: @toplevelPkgs\n\n";
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print "{fetchurl}:\n\n";
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print "[\n\n";
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# Output the packages in strongly connected components.
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my %done;
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my %forward;
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my $newComponent = 1;
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foreach my $pkgName (@order) {
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$done{$pkgName} = 1;
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my $cdata = $packages{$pkgName};
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my @deps = @{$depsUsed{$pkgName}};
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foreach my $dep (@deps) {
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$dep = $provides{$dep} if defined $provides{$dep};
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$forward{$dep} = 1 unless defined $done{$dep};
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}
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delete $forward{$pkgName};
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print " [\n\n" if $newComponent;
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$newComponent = 0;
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my $origName = basename $cdata->{Filename};
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my $cleanedName = $origName;
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$cleanedName =~ s/~//g;
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print " (fetchurl {\n";
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print " url = $urlPrefix/$cdata->{Filename};\n";
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print " sha256 = \"$cdata->{SHA256}\";\n";
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print " name = \"$cleanedName\";\n" if $cleanedName ne $origName;
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print " })\n";
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print "\n";
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if (keys %forward == 0) {
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print " ]\n\n";
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$newComponent = 1;
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}
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}
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foreach my $pkgName (@order) {
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my $cdata = $packages{$pkgName};
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}
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print "]\n";
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if ($newComponent != 1) {
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print STDERR "argh: ", keys %forward, "\n";
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exit 1;
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}
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