To save on bandwith and avoid OOMs with large files.
Ofc, this relies on the remote server
(a) sending a content-length header and
(b) being honest about the size.
Common fedi servers seem to provide the header and (b) at least raises
the required privilege of an malicious actor to a server infrastructure
admin of an explicitly allowed host.
A more complete defense which still works when faced with
a malicious server requires changes in upstream Finch;
see https://github.com/sneako/finch/issues/224
E.g. *key’s emoji URLs typically don’t have file extensions, but
until now we just slapped ".png" at its end hoping for the best.
Furthermore, this gives us a chance to actually reject non-images,
which before was not feasible exatly due to those extension-less URLs
* rejected_shortcodes is defined as a list of strings in the
configuration description. As such, database-based configuration was
led to handle those settings as strings, and not as the actually
expected type, Regex.
* This caused each message passing through this MRF, if a rejected
shortcode was set and the emoji did not exist already on the instance,
to fail federating, as an exception was raised, swiftly caught and
mostly silenced.
* This commit fixes the issue by introducing new behavior: strings are
now handled as perfect matches for an emoji shortcode (meaning that if
the emoji-to-be-pulled's shortcode is in the blacklist, it will be
rejected), while still supporting Regex types as before.
Oneric
Hélène
