caddyhttp: Fix edgecase with auto HTTP->HTTPS logic (#4243)

modules/caddyhttp/server.go

@@ -379,7 +379,9 @@ func (s *Server) hasTLSClientAuth() bool {
 // that it is after any other host matcher but before any "catch-all"
 // route without a host matcher.
 func (s *Server) findLastRouteWithHostMatcher() int {
+	foundHostMatcher := false
 	lastIndex := len(s.Routes)
+
 	for i, route := range s.Routes {
 		// since we want to break out of an inner loop, use a closure
 		// to allow us to use 'return' when we found a host matcher
@@ -388,6 +390,7 @@ func (s *Server) findLastRouteWithHostMatcher() int {
 				for _, matcher := range sets {
 					switch matcher.(type) {
 					case *MatchHost:
+						foundHostMatcher = true
 						return true
 					}
 				}
@@ -401,6 +404,14 @@ func (s *Server) findLastRouteWithHostMatcher() int {
 			lastIndex = i + 1
 		}
 	}
+
+	// If we didn't actually find a host matcher, return 0
+	// because that means every defined route was a "catch-all".
+	// See https://caddy.community/t/how-to-set-priority-in-caddyfile/13002/8
+	if !foundHostMatcher {
+		return 0
+	}
+
 	return lastIndex
 }