auth: only use X- headers instead of wsgi.url_scheme if explicitly told so in url_scheme_header - drop https_fixup setting Before, several X- headers would be trusted to overrule the actual connection protocol (http or https) seen by the Kallithea WSGI server. That was mainly when https_fixup were set, but it incorrectly also kicked in if https_fixup or use_htsts were configured. The ambiguity of which headers were used also made it less reliable. The proxy server not only had to be configured to set one of the headers correctly, it also had to make sure other headers were not passed on from the client. It would thus in some cases be possible for clients to fake the connection scheme, and thus potentially be possible to bypass restrictions configured in Kallithea. Fixed by making it configurable which WSGI environment variable to use for the protocol. Users can configure url_scheme_header to for example HTTP_X_FORWARDED_PROTO instead of using the default wsgi.url_scheme . This change is a bit similar to what is going on in the https_fixup middleware, but is doing a bit more of what for example is happening in similar code in werkzeug/middleware/proxy_fix.py . The semantics of the old https_fixup were unsafe, so it has been dropped. Admins that are upgrading must change their configuration to use the new url_scheme_header option.

--- a/docs/setup.rst	Sun May 09 22:34:02 2021 +0200
+++ b/docs/setup.rst	Sun May 09 22:40:56 2021 +0200
@@ -432,11 +432,10 @@
 
 Kallithea will by default rely on finding the protocol (``http`` or ``https``)
 in the WSGI environment as ``wsgi.url_scheme``. If the proxy server puts
-the protocol of the client request in the ``X-Url-Scheme``,
-``X-Forwarded-Scheme``, or ``X-Forwarded-Proto`` HTTP header,
-Kallithea can be configured to trust these headers by setting::
+the protocol of the client request in the ``X-Forwarded-Proto`` HTTP header,
+Kallithea can be configured to trust that header by setting::
 
-    https_fixup = true
+    url_scheme_variable = HTTP_X_FORWARDED_PROTO
 
 
 HTTPS support
@@ -447,9 +446,8 @@
 Alternatively, you can use some special configuration settings to control
 directly which scheme/protocol Kallithea will use when generating URLs:
 
-- With ``https_fixup = true``, the scheme will be taken from the
-  ``X-Url-Scheme``, ``X-Forwarded-Scheme`` or ``X-Forwarded-Proto`` HTTP header
-  (default ``http``).
+- With ``url_scheme_variable`` set, the scheme will be taken from that HTTP
+  header.
 - With ``force_https = true``, the scheme will be seen as ``https``.
 - With ``use_htsts = true``, Kallithea will set ``Strict-Transport-Security`` when using https.