Drupal

The Drupal default htaccess includes a rule which blocks access to directories beginning with a period:

# Block access to "hidden" directories whose names begin with a period. This
# includes directories used by version control systems such as Subversion or
# Git to store control files. Files whose names begin with a period, as well
# as the control files used by CVS, are protected by the FilesMatch directive
# above.
#
# NOTE: This only works when mod_rewrite is loaded. Without mod_rewrite, it is
# not possible to block access to entire directories from .htaccess, because
# <DirectoryMatch> is not allowed here.
#
# If you do not have mod_rewrite installed, you should remove these
# directories from your webroot or otherwise protect them from being
# downloaded.
RewriteRule "(^|/)\." - [F]

Replace the RewriteRule line with:

RewriteRule "(^|/)\.(?!well-known)" - [F]

This modification will become part of Drupal core in https://www.drupal.org/node/2408321