implement FAIL METADATA RATE_LIMITED

default.yaml

@@ -1111,6 +1111,11 @@ metadata:
     max-subs: 100
     # how many keys can be stored per entity?
     max-keys: 100
+    # rate limiting for client metadata updates, which are expensive to process
+    client-throttle:
+        enabled: true
+        duration: 2m
+        max-attempts: 10
 
 # experimental support for mobile push notifications
 # see the manual for potential security, privacy, and performance implications.

irc/client.go

@@ -130,6 +130,7 @@ type Client struct {
 	pushSubscriptionsExist  atomic.Uint32 // this is a cache on len(pushSubscriptions) != 0
 	pushQueue               pushQueue
 	metadata                map[string]string
+	metadataThrottle        connection_limits.ThrottleDetails
 }
 
 type saslStatus struct {

irc/config.go

@@ -734,10 +734,11 @@ type Config struct {
 	}
 
 	Metadata struct {
-		Enabled       bool
-		MaxSubs       int `yaml:"max-subs"`
-		MaxKeys       int `yaml:"max-keys"`
-		MaxValueBytes int `yaml:"max-value-length"`
+		Enabled        bool
+		MaxSubs        int            `yaml:"max-subs"`
+		MaxKeys        int            `yaml:"max-keys"`
+		MaxValueBytes  int            `yaml:"max-value-length"`
+		ClientThrottle ThrottleConfig `yaml:"client-throttle"`
 	}
 
 	WebPush struct {

irc/getters.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/ergochat/ergo/irc/caps"
+	"github.com/ergochat/ergo/irc/connection_limits"
 	"github.com/ergochat/ergo/irc/languages"
 	"github.com/ergochat/ergo/irc/modes"
 	"github.com/ergochat/ergo/irc/utils"
@@ -1039,3 +1040,22 @@ func (client *Client) CountMetadata() int {
 
 	return len(client.metadata)
 }
+
+func (client *Client) checkMetadataThrottle() (throttled bool, remainingTime time.Duration) {
+	config := client.server.Config()
+	if !config.Metadata.ClientThrottle.Enabled {
+		return false, 0
+	}
+
+	client.stateMutex.Lock()
+	defer client.stateMutex.Unlock()
+
+	// copy client.metadataThrottle locally and then back for processing
+	var throttle connection_limits.GenericThrottle
+	throttle.ThrottleDetails = client.metadataThrottle
+	throttle.Duration = config.Metadata.ClientThrottle.Duration
+	throttle.Limit = config.Metadata.ClientThrottle.MaxAttempts
+	throttled, remainingTime = throttle.Touch()
+	client.metadataThrottle = throttle.ThrottleDetails
+	return
+}

irc/handlers.go

@@ -3197,6 +3197,18 @@ func metadataRegisteredHandler(client *Client, config *Config, subcommand string
 			return
 		}
 
+		// only rate limit clients changing their own metadata:
+		// channel metadata updates are not any more costly than a PRIVMSG
+		if client == targetClient {
+			if throttled, remainingTime := client.checkMetadataThrottle(); throttled {
+				retryAfter := strconv.Itoa(int(remainingTime.Seconds()) + 1)
+				rb.Add(nil, server.name, "FAIL", "METADATA", "RATE_LIMITED",
+					target, utils.SafeErrorParam(key), retryAfter,
+					fmt.Sprintf(client.t("Please wait at least %v and try again"), remainingTime.Round(time.Millisecond)))
+				return
+			}
+		}
+
 		if len(params) > 3 {
 			value := params[3]
 

irc/metadata.go

@@ -21,7 +21,7 @@ var (
 	errMetadataNotFound    = errors.New("key not found")
 )
 
-type MetadataHaver = interface {
+type MetadataHaver interface {
 	SetMetadata(key string, value string, limit int) (updated bool, err error)
 	GetMetadata(key string) (string, bool)
 	DeleteMetadata(key string) (updated bool)

irc/numerics.go

@@ -183,12 +183,13 @@ const (
 	RPL_MONLIST            = "732"
 	RPL_ENDOFMONLIST       = "733"
 	ERR_MONLISTFULL        = "734"
-	RPL_KEYVALUE           = "761" // metadata numerics
+	RPL_WHOISKEYVALUE      = "760" // metadata numerics
+	RPL_KEYVALUE           = "761"
 	RPL_KEYNOTSET          = "766"
 	RPL_METADATASUBOK      = "770"
 	RPL_METADATAUNSUBOK    = "771"
 	RPL_METADATASUBS       = "772"
-	RPL_METADATASYNCLATER  = "774"
+	RPL_METADATASYNCLATER  = "774" // end metadata numerics
 	RPL_LOGGEDIN           = "900"
 	RPL_LOGGEDOUT          = "901"
 	ERR_NICKLOCKED         = "902"

traditional.yaml

@@ -1082,6 +1082,11 @@ metadata:
     max-subs: 100
     # how many keys can be stored per entity?
     max-keys: 100
+    # rate limiting for client metadata updates, which are expensive to process
+    client-throttle:
+        enabled: true
+        duration: 2m
+        max-attempts: 10
 
 # experimental support for mobile push notifications
 # see the manual for potential security, privacy, and performance implications.