search: do not index base-85 binary patches

Base-85 binary patches generated by git lead to many false
positives, so skip over gibberish words which may occur in them.
To avoid regressions in search results, continue to allow
searching for exact size matches (via "literal $SIZE") and the
phrase "GIT binary patch" for the mere presence of a binary
patch.

1 files changed, 36 insertions, 16 deletions

diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index 53ec23a5..cbfe7816 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -36,9 +36,8 @@ our $BATCH_BYTES = $ENV{XAPIAN_FLUSH_THRESHOLD} ? 0x7fffffff :
         # assume a typical 64-bit system has 8x more RAM than a
         # typical 32-bit system:
         (($Config{ptrsize} >= 8 ? 8192 : 1024) * 1024);
-
 use constant DEBUG => !!$ENV{DEBUG};
-
+my $BASE85 = qr/\A[a-zA-Z0-9\!\#\$\%\&\(\)\*\+\-;<=>\?\@\^_`\{\|\}\~]+\z/;
 my $xapianlevels = qr/\A(?:full|medium)\z/;
 my $hex = '[a-f0-9]';
 my $OID = $hex .'{40,}';
@@ -258,21 +257,42 @@ sub index_diff ($$$) {
         my ($self, $txt, $doc) = @_;
         my %seen;
         my $in_diff;
-        my @xnq;
-        my $xnq = \@xnq;
-        foreach (split(/\n/, $txt)) {
-                if ($in_diff && s/^ //) { # diff context
+        my $xnq = [];
+        my @l = split(/\n/, $$txt);
+        undef $$txt;
+        while (defined($_ = shift @l)) {
+                if ($in_diff && /^GIT binary patch/) {
+                        push @$xnq, $_;
+                        while (@l && $l[0] =~ /^literal /) {
+                                # TODO allow searching by size range?
+                                # allows searching by exact size via:
+                                # "literal $SIZE"
+                                push @$xnq, shift(@l);
+
+                                # skip base85 and empty lines
+                                while (@l && ($l[0] =~ /$BASE85/o ||
+                                                $l[0] !~ /\S/)) {
+                                        shift @l;
+                                }
+                                # loop hits trailing "literal 0\nHcmV?d00001\n"
+                        }
+                } elsif ($in_diff && s/^ //) { # diff context
                         index_diff_inc($self, $_, 'XDFCTX', $xnq);
                 } elsif (/^-- $/) { # email signature begins
                         $in_diff = undef;
-                } elsif (m!^diff --git "?[^/]+/.+ "?[^/]+/.+\z!) {
-                        # wait until "---" and "+++" to capture filenames
+                } elsif (m!^diff --git ("?[^/]+/.+) ("?[^/]+/.+)\z!) {
+                        # capture filenames here for binary diffs:
+                        my ($fa, $fb) = ($1, $2);
+                        push @$xnq, $_;
                         $in_diff = 1;
-                        push @xnq, $_;
+                        $fa = (split(m'/', git_unquote($fa), 2))[1];
+                        $fb = (split(m'/', git_unquote($fb), 2))[1];
+                        $seen{$fa}++ or index_diff_inc($self, $fa, 'XDFN', $xnq);
+                        $seen{$fb}++ or index_diff_inc($self, $fb, 'XDFN', $xnq);
                 # traditional diff:
                 } elsif (m/^diff -(.+) (\S+) (\S+)$/) {
                         my ($opt, $fa, $fb) = ($1, $2, $3);
-                        push @xnq, $_;
+                        push @$xnq, $_;
                         # only support unified:
                         next unless $opt =~ /[uU]/;
                         $in_diff = index_old_diff_fn($self, \%seen, $fa, $fb,
@@ -288,8 +308,8 @@ sub index_diff ($$$) {
                         $seen{$fn}++ or index_diff_inc($self, $fn, 'XDFN', $xnq);
                         $in_diff = 1;
                 } elsif (/^--- (\S+)/) {
-                        $in_diff = $1;
-                        push @xnq, $_;
+                        $in_diff = $1; # old diff filename
+                        push @$xnq, $_;
                 } elsif (defined $in_diff && /^\+\+\+ (\S+)/) {
                         $in_diff = index_old_diff_fn($self, \%seen, $in_diff,
                                                         $1, $xnq);
@@ -315,19 +335,19 @@ sub index_diff ($$$) {
                                 /^(?:dis)?similarity index / ||
                                 /^\\ No newline at end of file/ ||
                                 /^Binary files .* differ/) {
-                        push @xnq, $_;
+                        push @$xnq, $_;
                 } elsif ($_ eq '') {
                         # possible to be in diff context, some mail may be
                         # stripped by MUA or even GNU diff(1).  "git apply"
                         # treats a bare "\n" as diff context, too
                 } else {
-                        push @xnq, $_;
+                        push @$xnq, $_;
                         warn "non-diff line: $_\n" if DEBUG && $_ ne '';
                         $in_diff = undef;
                 }
         }
 
-        index_text($self, join("\n", @xnq), 1, 'XNQ');
+        index_text($self, join("\n", @$xnq), 1, 'XNQ');
 }
 
 sub index_xapian { # msg_iter callback
@@ -373,7 +393,7 @@ sub index_xapian { # msg_iter callback
                 } else {
                         # does it look like a diff?
                         if ($txt =~ /^(?:diff|---|\+\+\+) /ms) {
-                                index_diff($self, $txt, $doc);
+                                index_diff($self, \$txt, $doc);
                         } else {
                                 index_text($self, $txt, 1, 'XNQ');
                         }