generate_sbom: add license mapping to rewrite licenses spdx conform

Added functionalities to configure license mapping files
(json-formatted) to do a rewrite of the licenses to write spdx conform
ones into the generated document.

This is to handle non spdx conform license naming in packages taken from
upstream without forking/fixing each package.

The mapping has to be part of the image sources/created rootfs (e.g. livebuild).

Example of a mapping file:
```
{
  "GPL-1+": "GPL-1.0-or-later",
  "LGPL-1+": "LGPL-1.0-or-later",
  "LGPL-1.0+": "LGPL-1.0-or-later",
  "GPL-2+": "GPL-2.0-or-later",
  "GPL-2.0+": "GPL-2.0-or-later",
  "GPL-2": "GPL-2.0-only",
  "GPL-2.0": "GPL-2.0-only",
  "GPL-3+": "GPL-3.0-or-later"
}

```

The mapping is activated by specifying the files in the project
configuration:
```
BuildFlags: spdx-license-mapping:/license_mapping.json spdx-license-mapping:/spdx_licenses.json
```

The flag can be defined multiple times for different files if needed,
the content of the files gets merged.
The files are defined in the BuildFlag with its path in the created rootfs.

generate_sbom

@@ -283,9 +283,63 @@ sub read_pkgs_rpmdb {
   return \@rpms;
 }
 
+sub spdx_license_mapping {
+  my ($mapping_file) = @_;
+  local *F;
+  my $json_t = do {
+    unless (open(F, '<', $mapping_file)) {
+      warn("Could not read license mapping file $mapping_file, $!");
+      return {};
+    }
+    local $/;
+    <F>
+  };
+  my $license_mapping = eval { JSON::XS::decode_json($json_t) };
+  if ($@) {
+    warn("Failed to parse $mapping_file: $@");
+    return {};
+  }
+  return $license_mapping;
+}
+
+sub map_license {
+  my ($license, $license_mapping, $pkg) = @_;
+  if ( $license =~ /\sor\s/i ) {
+    my @licenses_or;
+    foreach my $l (split(/\sor\s/i, $license)) {
+      push(@licenses_or, map_license($l, $license_mapping, $pkg));
+    }
+    $license = join(' OR ', @licenses_or);
+  } elsif ( $license =~ /\swith\s/i ) {
+    my @licenses_with;
+    foreach my $l (split(/\swith\s/i, $license)) {
+      push(@licenses_with, map_license($l, $license_mapping, $pkg));
+    }
+    $license = join(' WITH ', @licenses_with);
+  } elsif ( $license =~ /\sand\s/i ) {
+    my @licenses_and;
+    foreach my $l (split(/\sand\s/i, $license)) {
+      push(@licenses_and, map_license($l, $license_mapping, $pkg));
+    }
+    $license = join(' AND ', @licenses_and);
+  } elsif (defined $license_mapping->{$license}) {
+    $license = $license_mapping->{$license};
+  } else {
+    warn("SPDX-License-Mapping: License for package \"$pkg\" not found in mapping: $license\n");
+    $license = "NOASSERTION";
+  }
+  if ( $license =~ /NOASSERTION/) {
+      $license = "NOASSERTION";
+  }
+  return $license;
+}
+
 sub parse_debian_copyright_file {
   my ($root, $pkg) = @_;
   my $file = "$root/usr/share/doc/$pkg/copyright";
+  if ( -l $file ) {
+      $file = $root . readlink $file;
+  }
   local *F;
   return {} unless open(F, '<', $file);
   my $firstline = <F>;
@@ -302,7 +356,6 @@ sub parse_debian_copyright_file {
       push @copyright, $1 if $1 ne '';
     } elsif (/^License:\s*(.*)$/) {
       $crfound = 0;
-      # TODO licenses has to match https://spdx.org/licenses/?
       push @license, $1 if $1 ne '';
     } elsif (/^(Files|Comment|Disclaimer|Source|Upstream-Name|Upstream-Contact):/) {
       $crfound = 0;
@@ -607,7 +660,7 @@ my $spdx_json_template = {
 };
 
 sub spdx_encode_pkg {
-  my ($p, $distro, $pkgtype) = @_;
+  my ($p, $distro, $pkgtype, $license_mapping) = @_;
   my $vr = $p->{'VERSION'};
   $vr = "$vr-$p->{'RELEASE'}" if defined $p->{'RELEASE'};
   my $evr = $vr;
@@ -631,7 +684,11 @@ sub spdx_encode_pkg {
   my $license = $p->{'LICENSE'};
   if ($license) {
     $license =~ s/ and / AND /g;
-    $spdx->{'licenseConcluded'} = $license;
+    if (%$license_mapping) {
+      $spdx->{'licenseConcluded'} = map_license($license, $license_mapping, $p->{'NAME'});
+    } else {
+      $spdx->{'licenseConcluded'} = $license;
+    }
     $spdx->{'licenseDeclared'} = $license unless ($config->{'buildflags:spdx-declared-license'} || '') eq 'NOASSERTION';
   }
   $spdx->{'copyrightText'} = 'NOASSERTION';
@@ -778,6 +835,26 @@ my $pkgtype = 'rpm';
 $config = Build::read_config_dist($dist_opt, $arch || 'noarch', $configdir) if $dist_opt;
 my $no_files_generation = ($config->{'buildflags:spdx-files-generation'} || '') eq 'no';
 
+my @license_mapping_files = map { /^spdx-license-mapping:(.*)/ ? $1 : () } @{$config->{'buildflags'}};
+my $license_mapping = {};
+my $jsonxs_available=0;
+eval
+{
+  require JSON::XS;
+  $jsonxs_available=1;
+};
+if (@license_mapping_files > 0) {
+  if ($jsonxs_available) {
+    foreach my $mapping_file ( @license_mapping_files ) {
+      my $href = spdx_license_mapping($toprocess . $mapping_file);
+      %$license_mapping = (%$license_mapping, %$href);
+    }
+  } else {
+    warn("No license mapping as JSON::XS is not available!");
+  }
+}
+
+
 if ($isproduct) {
   # product case
   #$files = gen_filelist($toprocess);
@@ -839,7 +916,7 @@ if ($format eq 'spdx') {
   $intoto_type = 'https://spdx.dev/Document';
   $doc = spdx_encode_header($subjectname);
   for my $p (@$pkgs) {
-    push @{$doc->{'packages'}}, spdx_encode_pkg($p, $distro, $pkgtype);
+    push @{$doc->{'packages'}}, spdx_encode_pkg($p, $distro, $pkgtype, $license_mapping);
   }
   for my $f (@$files) {
     next if $f->{'SKIP'};