chore(dashboard): Make CSWSH protection explicit

web/srv/api_handlers.go

@@ -45,6 +45,11 @@ var (
 	websocketUpgrader   = websocket.Upgrader{
 		ReadBufferSize:  maxMessageSize,
 		WriteBufferSize: maxMessageSize,
+		// Only allows requests from the same host, to prevent CSRF attacks.
+		// This is the default behavior in gorilla/websocket even if the
+		// CheckOrigin field is not set, but we make it explicit here as a good
+		// practice, avoiding relying on default behavior.
+		CheckOrigin: checkSameOrigin,
 	}
 
 	// Checks whose description matches the following regexp won't be included

web/srv/check_same_origin.go

@@ -0,0 +1,46 @@
+package srv
+
+import (
+	"net/http"
+	"net/url"
+	"unicode/utf8"
+)
+
+// checkSameOrigin returns true if the origin is not set or is equal to the request host.
+// Copied from gorilla/websocket.
+func checkSameOrigin(r *http.Request) bool {
+	origin := r.Header["Origin"]
+	if len(origin) == 0 {
+		return true
+	}
+	u, err := url.Parse(origin[0])
+	if err != nil {
+		return false
+	}
+	return equalASCIIFold(u.Host, r.Host)
+}
+
+// equalASCIIFold returns true if s is equal to t with ASCII case folding as
+// defined in RFC 4790.
+// Copied from gorilla/websocket.
+func equalASCIIFold(s, t string) bool {
+	for s != "" && t != "" {
+		sr, size := utf8.DecodeRuneInString(s)
+		s = s[size:]
+		tr, size := utf8.DecodeRuneInString(t)
+		t = t[size:]
+		if sr == tr {
+			continue
+		}
+		if 'A' <= sr && sr <= 'Z' {
+			sr = sr + 'a' - 'A'
+		}
+		if 'A' <= tr && tr <= 'Z' {
+			tr = tr + 'a' - 'A'
+		}
+		if sr != tr {
+			return false
+		}
+	}
+	return s == t
+}