www: more restrictive query string parsing

Only allow single-character query keys to prevent clients from
wasting memory in Perl's hash tables.  We'll also perform the
utf8::decode and tr/+/ / calls once on the whole query string at
once to reduce op calls.

This also avoids creating an empty hash in the common case
when the QUERY_STRING is empty and instead relies on
auto-vivification of Perl.

1 files changed, 4 insertions, 9 deletions

diff --git a/lib/PublicInbox/Feed.pm b/lib/PublicInbox/Feed.pm
index de1e7dfe..69a92f8b 100644
--- a/lib/PublicInbox/Feed.pm
+++ b/lib/PublicInbox/Feed.pm
@@ -33,15 +33,11 @@ sub generate_html_index {
         my ($ctx) = @_;
         # if the 'r' query parameter is given, it is a legacy permalink
         # which we must continue supporting:
-        my $qp = $ctx->{qp};
-        my $ibx = $ctx->{ibx};
-        if ($qp && !$qp->{r} && $ibx->over) {
+        !$ctx->{qp}->{r} && $ctx->{ibx}->over and
                 return PublicInbox::View::index_topics($ctx);
-        }
 
-        my $env = $ctx->{env};
-        my $url = $ibx->base_url($env) . 'new.html';
-        my $qs = $env->{QUERY_STRING};
+        my $url = $ctx->{ibx}->base_url($ctx->{env}) . 'new.html';
+        my $qs = $ctx->{env}->{QUERY_STRING};
         $url .= "?$qs" if $qs ne '';
         [302, [ 'Location', $url, 'Content-Type', 'text/plain'],
                 [ "Redirecting to $url\n" ] ];
@@ -88,7 +84,6 @@ sub recent_msgs {
         return PublicInbox::View::paginate_recent($ctx, $max) if $ibx->over;
 
         # only for rare v1 inboxes which aren't indexed at all
-        my $qp = $ctx->{qp};
         my $hex = '[a-f0-9]';
         my $addmsg = qr!^:000000 100644 \S+ (\S+) A\t${hex}{2}/${hex}{38}$!;
         my $delmsg = qr!^:100644 000000 (\S+) \S+ D\t(${hex}{2}/${hex}{38})$!;
@@ -96,7 +91,7 @@ sub recent_msgs {
 
         # revision ranges may be specified
         my $range = 'HEAD';
-        my $r = $qp->{r} if $qp;
+        my $r = $ctx->{qp}->{r};
         if ($r && ($r =~ /\A(?:$refhex\.\.)?$refhex\z/o)) {
                 $range = $r;
         }