wwwattach: prevent deep-linking via Referer match

[public-inbox.git] / lib / PublicInbox / WwwAttach.pm

diff --git a/lib/PublicInbox/WwwAttach.pm b/lib/PublicInbox/WwwAttach.pm
index 20417295efd960194d97eb24d73c40bb736cacda..09c66d0239cb40a5a3942f957154b4ec54fc1097 100644 (file)
--- a/lib/PublicInbox/WwwAttach.pm
+++ b/lib/PublicInbox/WwwAttach.pm
@@ -9,6 +9,22 @@ use bytes (); # only for bytes::length
 use PublicInbox::EmlContentFoo qw(parse_content_type);
 use PublicInbox::Eml;
 
+sub referer_match ($) {
+       my ($ctx) = @_;
+       my $env = $ctx->{env};
+       my $referer = $env->{HTTP_REFERER} // '';
+       return 1 if $referer eq ''; # no referer is always OK for wget/curl
+
+       # prevent deep-linking from other domains on some browsers (Firefox)
+       # n.b.: $ctx->{-inbox}->base_url($env) with INBOX_URL won't work
+       # with dillo, we can only match "$url_scheme://$HTTP_HOST/" without
+       # path components
+       my $base_url = $env->{'psgi.url_scheme'} . '://' .
+                       ($env->{HTTP_HOST} //
+                        "$env->{SERVER_NAME}:$env->{SERVER_PORT}") . '/';
+       index($referer, $base_url) == 0;
+}
+
 sub get_attach_i { # ->each_part callback
        my ($part, $depth, $idx) = @{$_[0]};
        my $ctx = $_[1];
@@ -28,14 +44,20 @@ sub get_attach_i { # ->each_part callback
                                                                $ctx->{env});
                $part = $ctx->zflush($part->body);
        } else { # TODO: allow user to configure safe types
-               $res->[1]->[1] = 'application/octet-stream';
-               $part = $part->body;
+               if (referer_match($ctx)) {
+                       $res->[1]->[1] = 'application/octet-stream';
+                       $part = $part->body;
+               } else {
+                       $res->[0] = 403;
+                       $res->[1]->[1] = 'text/plain';
+                       $part = "Deep-linking prevented\n";
+               }
        }
        push @{$res->[1]}, 'Content-Length', bytes::length($part);
        $res->[2]->[0] = $part;
 }
 
-sub async_eml { # ->{async_eml} for async_blob_cb
+sub async_eml { # for async_blob_cb
        my ($ctx, $eml) = @_;
        eval { $eml->each_part(\&get_attach_i, $ctx, 1) };
        if ($@) {
@@ -55,8 +77,6 @@ sub async_next {
 sub scan_attach ($) { # public-inbox-httpd only
        my ($ctx) = @_;
        $ctx->{env}->{'psgix.io'}->{forward} = $ctx;
-       $ctx->{async_eml} = \&async_eml;
-       $ctx->{async_next} = \&async_next;
        $ctx->smsg_blob($ctx->{smsg});
 }