Allow logging key when the rate limit is exceeded.

README.md

@@ -82,10 +82,11 @@ This is an HTTP handler module, so it can be used wherever `http.handlers` modul
 			"window": "",
 			"max_events": 0
 		},
-		"storage": {},
 		"jitter": 0.0,
 		"sweep_interval": ""
-	}
+	},
+	"log_key": false,
+	"storage": {},
 	"distributed": {
 		"write_interval": "",
 		"read_interval": "",
@@ -99,6 +100,8 @@ All fields are optional, but to be useful, you'll need to define at least one zo
 
 To enable distributed RL, set `distributed` to a non-null object. The default read and write intervals are 5s, but you should tune these for your individual deployments.
 
+To log the key when a rate limit is hit, set `log_key` to `true`.
+
 Storage customizes the storage module that is used. Like normal Caddy convention, all instances with the same storage configuration are considered to be part of a cluster.
 
 Jitter is an optional percentage that adds random variance to the Retry-After time to avoid stampeding herds.
@@ -133,6 +136,7 @@ rate_limit {
 		write_interval <duration>
 		purge_age <duration>
 	}
+	log_key <bool>
 	storage <module...>
 	jitter  <percent>
 	sweep_interval <duration>

distributed.go

@@ -206,7 +206,7 @@ func (h Handler) distributedRateLimiting(w http.ResponseWriter, r *http.Request,
 
 			// no point in counting more if we're already over
 			if totalCount >= maxAllowed {
-				return h.rateLimitExceeded(w, r, repl, zoneName, oldestEvent.Add(window).Sub(now()))
+				return h.rateLimitExceeded(w, r, repl, zoneName, rlKey, oldestEvent.Add(window).Sub(now()))
 			}
 		}
 	}
@@ -228,7 +228,7 @@ func (h Handler) distributedRateLimiting(w http.ResponseWriter, r *http.Request,
 	limiter.mu.Unlock()
 
 	// otherwise, it appears limit has been exceeded
-	return h.rateLimitExceeded(w, r, repl, zoneName, oldestEvent.Add(window).Sub(now()))
+	return h.rateLimitExceeded(w, r, repl, zoneName, rlKey, oldestEvent.Add(window).Sub(now()))
 }
 
 type rlStateValue struct {

handler.go

@@ -65,6 +65,10 @@ type Handler struct {
 	// the global or default storage configuration will be used.
 	StorageRaw json.RawMessage `json:"storage,omitempty" caddy:"namespace=caddy.storage inline_key=module"`
 
+	// LogKey, if true, will log the key used for rate limiting.
+	// Defaults to `false` because keys can contain sensitive information.
+	LogKey bool `json:"log_key,omitempty"`
+
 	rateLimits []*RateLimit
 	storage    certmagic.Storage
 	random     *weakrand.Rand
@@ -170,7 +174,7 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhtt
 		if h.Distributed == nil {
 			// internal rate limiter only
 			if dur := limiter.When(); dur > 0 {
-				return h.rateLimitExceeded(w, r, repl, rl.zoneName, dur)
+				return h.rateLimitExceeded(w, r, repl, rl.zoneName, key, dur)
 			}
 		} else {
 			// distributed rate limiting; add last known state of other instances
@@ -183,7 +187,7 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhtt
 	return next.ServeHTTP(w, r)
 }
 
-func (h *Handler) rateLimitExceeded(w http.ResponseWriter, r *http.Request, repl *caddy.Replacer, zoneName string, wait time.Duration) error {
+func (h *Handler) rateLimitExceeded(w http.ResponseWriter, r *http.Request, repl *caddy.Replacer, zoneName string, key string, wait time.Duration) error {
 	// add jitter, if configured
 	if h.random != nil {
 		jitter := h.randomFloatInRange(0, float64(wait)*h.Jitter)
@@ -198,11 +202,21 @@ func (h *Handler) rateLimitExceeded(w http.ResponseWriter, r *http.Request, repl
 	if err != nil {
 		remoteIP = r.RemoteAddr // assume there was no port, I guess
 	}
-	h.logger.Info("rate limit exceeded",
-		zap.String("zone", zoneName),
-		zap.Duration("wait", wait),
-		zap.String("remote_ip", remoteIP),
-	)
+
+	if h.LogKey {
+		h.logger.Info("rate limit exceeded",
+			zap.String("zone", zoneName),
+			zap.String("key", key),
+			zap.Duration("wait", wait),
+			zap.String("remote_ip", remoteIP),
+		)
+	} else {
+		h.logger.Info("rate limit exceeded",
+			zap.String("zone", zoneName),
+			zap.Duration("wait", wait),
+			zap.String("remote_ip", remoteIP),
+		)
+	}
 
 	// make some information about this rate limit available
 	repl.Set("http.rate_limit.exceeded.name", zoneName)