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.

3 files changed, 20 insertions, 19 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 = $r;
         }
diff --git a/lib/PublicInbox/ViewVCS.pm b/lib/PublicInbox/ViewVCS.pm
index eb757089..5529ed5b 100644
--- a/lib/PublicInbox/ViewVCS.pm
+++ b/lib/PublicInbox/ViewVCS.pm
@@ -596,10 +596,9 @@ sub show_blob { # git->cat_async callback
 # GET /$INBOX/$GIT_OBJECT_ID/s/$FILENAME
 sub show ($$;$) {
         my ($ctx, $oid_b, $fn) = @_;
-        my $qp = $ctx->{qp};
         my $hints = $ctx->{hints} = {};
         while (my ($from, $to) = each %QP_MAP) {
-                defined(my $v = $qp->{$from}) or next;
+                my $v = $ctx->{qp}->{$from} // next;
                 $hints->{$to} = $v if $v ne '';
         }
         $ctx->{fn} = $fn;
diff --git a/lib/PublicInbox/WWW.pm b/lib/PublicInbox/WWW.pm
index a8f1ad17..9919f975 100644
--- a/lib/PublicInbox/WWW.pm
+++ b/lib/PublicInbox/WWW.pm
@@ -45,14 +45,21 @@ sub call {
         my $ctx = { env => $env, www => $self };
 
         # we don't care about multi-value
-        %{$ctx->{qp}} = map {
-                utf8::decode($_);
-                tr/+/ /;
-                my ($k, $v) = split(/=/, $_, 2);
-                # none of the keys we care about will need escaping
-                ($k // '', uri_unescape($v // ''))
-        } split(/[&;]+/, $env->{QUERY_STRING});
-
+        # '0' isn't a QUERY_STRING we care about
+        if (my $qs = $env->{QUERY_STRING}) {
+                utf8::decode($qs);
+                $qs =~ tr/+/ /;
+                %{$ctx->{qp}} = map {
+                        # we only use single-char query param keys
+                        if (s/\A([A-Za-z])=//) {
+                                $1 => uri_unescape($_)
+                        } elsif (/\A[a-z]\z/) { # some boolean options
+                                $_ => ''
+                        } else {
+                                () # ignored
+                        }
+                } split(/[&;]+/, $qs);
+        }
         my $path_info = path_info_raw($env);
         my $method = $env->{REQUEST_METHOD};