--- loncom/interface/loncommon.pm	2019/07/30 11:10:55	1.1075.2.134
+++ loncom/interface/loncommon.pm	2019/07/30 21:13:54	1.1075.2.135
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common routines
 #
-# $Id: loncommon.pm,v 1.1075.2.134 2019/07/30 11:10:55 raeburn Exp $
+# $Id: loncommon.pm,v 1.1075.2.135 2019/07/30 21:13:54 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -71,6 +71,7 @@ use Apache::lonuserutils();
 use Apache::lonuserstate();
 use Apache::courseclassifier();
 use LONCAPA qw(:DEFAULT :match);
+use HTTP::Request;
 use DateTime::TimeZone;
 use DateTime::Locale;
 use Encode();
@@ -16951,6 +16952,157 @@ sub des_decrypt {
     return $plaintext;
 }
 
+sub is_nonframeable {
+    my ($url,$absolute,$hostname,$ip,$nocache) = @_;
+    my ($remprotocol,$remhost) = ($url =~ m{^(https?)\://(([a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,})}i);
+    return if (($remprotocol eq '') || ($remhost eq ''));
+
+    $remprotocol = lc($remprotocol);
+    $remhost = lc($remhost);
+    my $remport = 80;
+    if ($remprotocol eq 'https') {
+        $remport = 443;
+    }
+    my ($result,$cached) = &Apache::lonnet::is_cached_new('noiframe',$remhost.':'.$remport);
+    if ($cached) {
+        unless ($nocache) {
+            if ($result) {
+                return 1;
+            } else {
+                return 0;
+            }
+        }
+    }
+    my $uselink;
+    my $request = new HTTP::Request('HEAD',$url);
+    my $response = &LONCAPA::LWPReq::makerequest('',$request,'','',5);
+    if ($response->is_success()) {
+        my $secpolicy = lc($response->header('content-security-policy'));
+        my $xframeop = lc($response->header('x-frame-options'));
+        $secpolicy =~ s/^\s+|\s+$//g;
+        $xframeop =~ s/^\s+|\s+$//g;
+        if (($secpolicy ne '') || ($xframeop ne '')) {
+            my $remotehost = $remprotocol.'://'.$remhost;
+            my ($origin,$protocol,$port);
+            if ($ENV{'SERVER_PORT'} =~/^\d+$/) {
+                $port = $ENV{'SERVER_PORT'};
+            } else {
+                $port = 80;
+            }
+            if ($absolute eq '') {
+                $protocol = 'http:';
+                if ($port == 443) {
+                    $protocol = 'https:';
+                }
+                $origin = $protocol.'//'.lc($hostname);
+            } else {
+                $origin = lc($absolute);
+                ($protocol,$hostname) = ($absolute =~ m{^(https?:)//([^/]+)$});
+            }
+            if (($secpolicy) && ($secpolicy =~ /\Qframe-ancestors\E([^;]*)(;|$)/)) {
+                my $framepolicy = $1;
+                $framepolicy =~ s/^\s+|\s+$//g;
+                my @policies = split(/\s+/,$framepolicy);
+                if (@policies) {
+                    if (grep(/^\Q'none'\E$/,@policies)) {
+                        $uselink = 1;
+                    } else {
+                        $uselink = 1;
+                        if ((grep(/^\Q*\E$/,@policies)) || (grep(/^\Q$protocol\E$/,@policies)) ||
+                                (($origin ne '') && (grep(/^\Q$origin\E$/,@policies))) ||
+                                (($ip ne '') && (grep(/^\Q$ip\E$/,@policies)))) {
+                            undef($uselink);
+                        }
+                        if ($uselink) {
+                            if (grep(/^\Q'self'\E$/,@policies)) {
+                                if (($origin ne '') && ($remotehost eq $origin)) {
+                                    undef($uselink);
+                                }
+                            }
+                        }
+                        if ($uselink) {
+                            my @possok;
+                            if ($ip ne '') {
+                                push(@possok,$ip);
+                            }
+                            my $hoststr = '';
+                            foreach my $part (reverse(split(/\./,$hostname))) {
+                                if ($hoststr eq '') {
+                                    $hoststr = $part;
+                                } else {
+                                    $hoststr = "$part.$hoststr";
+                                }
+                                if ($hoststr eq $hostname) {
+                                    push(@possok,$hostname);
+                                } else {
+                                    push(@possok,"*.$hoststr");
+                                }
+                            }
+                            if (@possok) {
+                                foreach my $poss (@possok) {
+                                    last if (!$uselink);
+                                    foreach my $policy (@policies) {
+                                        if ($policy =~ m{^(\Q$protocol\E//|)\Q$poss\E(\Q:$port\E|)$}) {
+                                            undef($uselink);
+                                            last;
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            } elsif ($xframeop ne '') {
+                $uselink = 1;
+                my @policies = split(/\s*,\s*/,$xframeop);
+                if (@policies) {
+                    unless (grep(/^deny$/,@policies)) {
+                        if ($origin ne '') {
+                            if (grep(/^sameorigin$/,@policies)) {
+                                if ($remotehost eq $origin) {
+                                    undef($uselink);
+                                }
+                            }
+                            if ($uselink) {
+                                foreach my $policy (@policies) {
+                                    if ($policy =~ /^allow-from\s*(.+)$/) {
+                                        my $allowfrom = $1;
+                                        if (($allowfrom ne '') && ($allowfrom eq $origin)) {
+                                            undef($uselink);
+                                            last;
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+    if ($nocache) {
+        if ($cached) {
+            my $devalidate;
+            if ($uselink && !$result) {
+                $devalidate = 1;
+            } elsif (!$uselink && $result) {
+                $devalidate = 1;
+            }
+            if ($devalidate) {
+                &Apache::lonnet::devalidate_cache_new('noiframe',$remhost.':'.$remport);
+            }
+        }
+    } else {
+        if ($uselink) {
+            $result = 1;
+        } else {
+            $result = 0;
+        }
+        &Apache::lonnet::do_cache_new('noiframe',$remhost.':'.$remport,$result,3600);
+    }
+    return $uselink;
+}
+
 1;
 __END__;