Add CrowdSec AppSec request inspection to the reverse proxy

proxy/internal/netutil/upgrade.go

@@ -0,0 +1,23 @@
+package netutil
+
+import (
+	"net/http"
+
+	"golang.org/x/net/http/httpguts"
+)
+
+// IsUpgradeRequest reports whether r is a protocol-upgrade request, using the
+// same predicate httputil.ReverseProxy applies when it decides to hand the
+// connection over instead of proxying normally.
+//
+// Matching the forwarder exactly matters for anything that inspects a request
+// before it is proxied: a looser test (an Upgrade header on its own, say) marks
+// a request as an upgrade and skips inspection, while the forwarder still
+// delivers it to the backend as an ordinary request with its body intact. That
+// gap is a body-inspection bypass reachable by adding one header.
+func IsUpgradeRequest(h http.Header) bool {
+	if !httpguts.HeaderValuesContainsToken(h["Connection"], "Upgrade") {
+		return false
+	}
+	return h.Get("Upgrade") != ""
+}