[feature] Ratelimit + serve emoji images on separate router group (#2548)

* [feature] Serve + rate limit emoji files separately from attachments

* add a wee little warning about uploading loads of emojis

cmd/gotosocial/action/server/server.go

@@ -104,6 +104,13 @@
 		return fmt.Errorf("error creating instance instance: %s", err)
 	}
 
+	// Get the instance account
+	// (we'll need this later).
+	instanceAccount, err := dbService.GetInstanceAccount(ctx, "")
+	if err != nil {
+		return fmt.Errorf("error retrieving instance account: %w", err)
+	}
+
 	// Open the storage backend
 	storage, err := gtsstorage.AutoConfig()
 	if err != nil {
@@ -313,14 +320,15 @@ func(context.Context, time.Time) {
 	rlExceptions := config.GetAdvancedRateLimitExceptions()
 	clLimit := middleware.RateLimit(rlLimit, rlExceptions)        // client api
 	s2sLimit := middleware.RateLimit(rlLimit, rlExceptions)       // server-to-server (AP)
-	fsLimit := middleware.RateLimit(rlLimit, rlExceptions)  // fileserver / web templates
+	fsMainLimit := middleware.RateLimit(rlLimit, rlExceptions)    // fileserver / web templates
+	fsEmojiLimit := middleware.RateLimit(rlLimit*2, rlExceptions) // fileserver (emojis only, use high limit)
 
 	// throttling
 	cpuMultiplier := config.GetAdvancedThrottlingMultiplier()
 	retryAfter := config.GetAdvancedThrottlingRetryAfter()
 	clThrottle := middleware.Throttle(cpuMultiplier, retryAfter)  // client api
 	s2sThrottle := middleware.Throttle(cpuMultiplier, retryAfter) // server-to-server (AP)
-	fsThrottle := middleware.Throttle(cpuMultiplier, retryAfter)  // fileserver / web templates
+	fsThrottle := middleware.Throttle(cpuMultiplier, retryAfter)  // fileserver / web templates / emojis
 	pkThrottle := middleware.Throttle(cpuMultiplier, retryAfter)  // throttle public key endpoint separately
 
 	gzip := middleware.Gzip() // applied to all except fileserver
@@ -330,12 +338,13 @@ func(context.Context, time.Time) {
 	authModule.Route(router, clLimit, clThrottle, gzip)
 	clientModule.Route(router, clLimit, clThrottle, gzip)
 	metricsModule.Route(router, clLimit, clThrottle, gzip)
-	fileserverModule.Route(router, fsLimit, fsThrottle)
+	fileserverModule.Route(router, fsMainLimit, fsThrottle)
+	fileserverModule.RouteEmojis(router, instanceAccount.ID, fsEmojiLimit, fsThrottle)
 	wellKnownModule.Route(router, gzip, s2sLimit, s2sThrottle)
 	nodeInfoModule.Route(router, s2sLimit, s2sThrottle, gzip)
 	activityPubModule.Route(router, s2sLimit, s2sThrottle, gzip)
 	activityPubModule.RoutePublicKey(router, s2sLimit, pkThrottle, gzip)
-	webModule.Route(router, fsLimit, fsThrottle, gzip)
+	webModule.Route(router, fsMainLimit, fsThrottle, gzip)
 
 	// Start the GoToSocial server.
 	server := gotosocial.NewServer(dbService, router, cleaner)

cmd/gotosocial/action/testrig/testrig.go

@@ -83,6 +83,13 @@
 
 	testrig.StandardDBSetup(state.DB, nil)
 
+	// Get the instance account
+	// (we'll need this later).
+	instanceAccount, err := state.DB.GetInstanceAccount(ctx, "")
+	if err != nil {
+		return fmt.Errorf("error retrieving instance account: %w", err)
+	}
+
 	if os.Getenv("GTS_STORAGE_BACKEND") == "s3" {
 		var err error
 		state.Storage, err = storage.NewS3Storage()
@@ -225,6 +232,7 @@
 	clientModule.Route(router)
 	metricsModule.Route(router)
 	fileserverModule.Route(router)
+	fileserverModule.RouteEmojis(router, instanceAccount.ID)
 	wellKnownModule.Route(router)
 	nodeInfoModule.Route(router)
 	activityPubModule.Route(router)

internal/api/fileserver.go

@@ -21,6 +21,7 @@
 	"github.com/gin-gonic/gin"
 	"github.com/superseriousbusiness/gotosocial/internal/api/fileserver"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/media"
 	"github.com/superseriousbusiness/gotosocial/internal/middleware"
 	"github.com/superseriousbusiness/gotosocial/internal/processing"
 	"github.com/superseriousbusiness/gotosocial/internal/router"
@@ -30,36 +31,98 @@ type Fileserver struct {
 	fileserver *fileserver.Module
 }
 
-func (f *Fileserver) Route(r *router.Router, m ...gin.HandlerFunc) {
-	fileserverGroup := r.AttachGroup("fileserver")
-
-	// Attach middlewares appropriate for this group.
-	fileserverGroup.Use(m...)
-	// If we're using local storage or proxying s3, we can set a
-	// long max-age + immutable on all file requests to reflect
-	// that we never host different files at the same URL (since
-	// ULIDs are generated per piece of media), so we can
-	// easily prevent clients having to fetch files repeatedly.
+// Attach cache middleware appropriate for file serving.
+func useFSCacheMiddleware(grp *gin.RouterGroup) {
+	// If we're using local storage or proxying s3 (ie., serving
+	// from here) we can set a long max-age + immutable on file
+	// requests to reflect that we never host different files at
+	// the same URL (since ULIDs are generated per piece of media),
+	// so we can prevent clients having to fetch files repeatedly.
 	//
-	// If we *are* using non-proxying s3, however, the max age
-	// must be set dynamically within the request handler,
-	// based on how long the signed URL has left to live before
-	// it expires. This ensures that clients won't cache expired
-	// links. This is done within fileserver/servefile.go, so we
-	// should not set the middleware here in that case.
+	// If we *are* using non-proxying s3, however (ie., not serving
+	// from here) the max age must be set dynamically within the
+	// request handler, based on how long the signed URL has left
+	// to live before it expires. This ensures that clients won't
+	// cache expired links. This is done within fileserver/servefile.go
+	// so we should not set the middleware here in that case.
 	//
 	// See:
 	//
 	// - https://developer.mozilla.org/en-US/docs/Web/HTTP/Caching#avoiding_revalidation
 	// - https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control#immutable
-	if config.GetStorageBackend() == "local" || config.GetStorageS3Proxy() {
-		fileserverGroup.Use(middleware.CacheControl(middleware.CacheControlConfig{
+	servingFromHere := config.GetStorageBackend() == "local" || config.GetStorageS3Proxy()
+	if !servingFromHere {
+		return
+	}
+
+	grp.Use(middleware.CacheControl(middleware.CacheControlConfig{
 		Directives: []string{"private", "max-age=604800", "immutable"},
 		Vary:       []string{"Range"}, // Cache partial ranges separately.
 	}))
 }
 
-	f.fileserver.Route(fileserverGroup.Handle)
+// Route the "main" fileserver group
+// that handles everything except emojis.
+func (f *Fileserver) Route(
+	r *router.Router,
+	m ...gin.HandlerFunc,
+) {
+	const fsGroupPath = "fileserver" +
+		"/:" + fileserver.AccountIDKey +
+		"/:" + fileserver.MediaTypeKey
+	fsGroup := r.AttachGroup(fsGroupPath)
+
+	// Attach provided +
+	// cache middlewares.
+	fsGroup.Use(m...)
+	useFSCacheMiddleware(fsGroup)
+
+	f.fileserver.Route(fsGroup.Handle)
+}
+
+// Route the "emojis" fileserver
+// group to handle emojis specifically.
+//
+// instanceAccount ID is required because
+// that is the ID under which all emoji
+// files are stored, and from which all
+// emoji file requests are therefore served.
+func (f *Fileserver) RouteEmojis(
+	r *router.Router,
+	instanceAcctID string,
+	m ...gin.HandlerFunc,
+) {
+	var fsEmojiGroupPath = "fileserver" +
+		"/" + instanceAcctID +
+		"/" + string(media.TypeEmoji)
+	fsEmojiGroup := r.AttachGroup(fsEmojiGroupPath)
+
+	// Inject the instance account and emoji media
+	// type params into the gin context manually,
+	// since we know we're only going to be serving
+	// emojis (stored under the instance account ID)
+	// from this group. This allows us to use the
+	// same handler functions for both the "main"
+	// fileserver handler and the emojis handler.
+	fsEmojiGroup.Use(func(c *gin.Context) {
+		c.Params = append(c.Params, []gin.Param{
+			{
+				Key:   fileserver.AccountIDKey,
+				Value: instanceAcctID,
+			},
+			{
+				Key:   fileserver.MediaTypeKey,
+				Value: string(media.TypeEmoji),
+			},
+		}...)
+	})
+
+	// Attach provided +
+	// cache middlewares.
+	fsEmojiGroup.Use(m...)
+	useFSCacheMiddleware(fsEmojiGroup)
+
+	f.fileserver.Route(fsEmojiGroup.Handle)
 }
 
 func NewFileserver(p *processing.Processor) *Fileserver {

internal/api/fileserver/fileserver.go

@@ -33,8 +33,8 @@
 	MediaSizeKey = "media_size"
 	// FileNameKey is the actual filename being sought. Will usually be a UUID then something like .jpeg
 	FileNameKey = "file_name"
-	// FileServePath is the fileserve path minus the 'fileserver' prefix.
-	FileServePath = "/:" + AccountIDKey + "/:" + MediaTypeKey + "/:" + MediaSizeKey + "/:" + FileNameKey
+	// FileServePath is the fileserve path minus the 'fileserver/:account_id/:media_type' prefix.
+	FileServePath = "/:" + MediaSizeKey + "/:" + FileNameKey
 )
 
 type Module struct {

web/source/settings/admin/emoji/local/overview.js

@@ -64,6 +64,11 @@ module.exports = function EmojiOverview({ }) {
 				You can either upload them here directly, or copy from those already
 				present on other (known) instances through the <Link to={`./remote`}>Remote Emoji</Link> page.
 			</p>
+			<p>
+				<strong>Be warned!</strong> If you upload more than about 300-400 custom emojis in
+				total on your instance, this may lead to rate-limiting issues for users and clients
+				if they try to load all the emoji images at once (which is what many clients do).
+			</p>
 			{content}
 		</>
 	);