www: only emit ASCII chars in attachment filenames

We don't want to emit funky URLs which can be lost in
translation or cause problems with non-Unicode-aware
clients.

Then, don't accept non-ASCII filenames in URLs, since
a manually-generated URL/filename in attachment downloads
could be used for Unicode homographs to confuse folks who
down the attachment.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/PublicInbox/View.pm b/lib/PublicInbox/View.pm
index 09afdaf1..83ae99bc 100644
--- a/lib/PublicInbox/View.pm
+++ b/lib/PublicInbox/View.pm
@@ -528,7 +528,7 @@ sub attach_link ($$$$;$) {
         $desc = $fn unless defined $desc;
         $desc = '' unless defined $desc;
         my $sfn;
-        if (defined $fn && $fn =~ /\A[[:alnum:]][\w\.-]+[[:alnum:]]\z/) {
+        if (defined $fn && $fn =~ /\A$PublicInbox::Hval::FN\z/o) {
                 $sfn = $fn;
         } elsif ($ct eq 'text/plain') {
                 $sfn = 'a.txt';