kwild,jsonrpc: add app.rpc-req-limit / cfg.AppCfg.RPCMaxReqSize (#936)

This adds a configurable request size limit to kwild.

In toml: app.rpc_req_limit
With cli flag: --app.rpc-req-limit

The default is somewhat arbitrarily 4,200,000 bytes.

If the network's genesis config sets max transaction size larger
than this limit, kwild warns on startup.

cmd/kwil-admin/nodecfg/toml.go

@@ -116,6 +116,9 @@ rpc_timeout = "{{ .AppCfg.RPCTimeout }}"
 # Timeout on database reads initiated by the user RPC service
 db_read_timeout = "{{ .AppCfg.ReadTxTimeout }}"
 
+# RPC request size limit in bytes
+rpc_req_limit = {{ .AppCfg.RPCMaxReqSize }}
+
 # List of Extension endpoints to be enabled ex: ["localhost:50052", "169.198.102.34:50053"]
 extension_endpoints = {{arrayFormatter .AppCfg.ExtensionEndpoints}}
 

cmd/kwild/config/config.go

@@ -76,6 +76,7 @@ type AppConfig struct {
 	DBName string `mapstructure:"pg_db_name"`
 
 	RPCTimeout         Duration                     `mapstructure:"rpc_timeout"`
+	RPCMaxReqSize      int                          `mapstructure:"rpc_req_limit"`
 	ReadTxTimeout      Duration                     `mapstructure:"db_read_timeout"`
 	ExtensionEndpoints []string                     `mapstructure:"extension_endpoints"`
 	AdminRPCPass       string                       `mapstructure:"admin_pass"`
@@ -580,6 +581,7 @@ func DefaultConfig() *KwildConfig {
 			DBUser:               "kwild",
 			DBName:               "kwild",
 			RPCTimeout:           Duration(45 * time.Second),
+			RPCMaxReqSize:        4_200_000,
 			ReadTxTimeout:        Duration(5 * time.Second),
 			Extensions:           make(map[string]map[string]string),
 			Snapshots: SnapshotConfig{

cmd/kwild/config/default_config.toml

@@ -40,6 +40,9 @@ rpc_timeout = "45s"
 # Timeout on database reads initiated by the user RPC service
 db_read_timeout = "5s"
 
+# RPC request size limit in bytes
+rpc_req_limit = 4200000
+
 # List of Extension endpoints to be enabled ex: ["localhost:50052", "169.198.102.34:50053"]
 extension_endpoints = []
 

cmd/kwild/config/flags.go

@@ -35,6 +35,7 @@ func AddConfigFlags(flagSet *pflag.FlagSet, cfg *KwildConfig) {
 	flagSet.StringVar(&cfg.AppCfg.ProfileFile, "app.profile-file", cfg.AppCfg.ProfileFile, "kwild profile output file path (e.g. cpu.pprof)")
 
 	flagSet.Var(&cfg.AppCfg.RPCTimeout, "app.rpc-timeout", "timeout for RPC requests (through reading the request, handling the request, and sending the response)")
+	flagSet.IntVar(&cfg.AppCfg.RPCMaxReqSize, "app.rpc-req-limit", cfg.AppCfg.RPCMaxReqSize, "RPC request size limit")
 	flagSet.Var(&cfg.AppCfg.ReadTxTimeout, "app.db-read-timeout", "timeout for database reads initiated by RPC requests")
 
 	// Extension endpoints flags

cmd/kwild/config/test_data/config.toml

@@ -43,6 +43,9 @@ rpc_timeout = "45s"
 # Timeout on database reads initiated by the user RPC service
 db_read_timeout = "5s"
 
+# RPC request size limit in bytes
+rpc_req_limit = 4200000
+
 # List of Extension endpoints to be enabled ex: ["localhost:50052", "169.198.102.34:50053"]
 extension_endpoints = ["localhost:50052", "localhost:50053", "localhost:50054"]
 

cmd/kwild/server/build.go

@@ -212,10 +212,16 @@ func buildServer(d *coreDependencies, closers *closeFuncs) *Server {
 	rpcSvcLogger := increaseLogLevel("user-json-svc", &d.log, d.cfg.Logging.RPCLevel)
 	rpcServerLogger := increaseLogLevel("user-jsonrpc-server", &d.log, d.cfg.Logging.RPCLevel)
 
+	if d.cfg.AppCfg.RPCMaxReqSize < d.cfg.ChainCfg.Mempool.MaxTxBytes {
+		d.log.Warnf("RPC request size limit (%d) is less than maximium transaction size (%d)",
+			d.cfg.AppCfg.RPCMaxReqSize, d.cfg.ChainCfg.Mempool.MaxTxBytes)
+	}
+
 	jsonRPCTxSvc := usersvc.NewService(db, e, wrappedCmtClient, txApp, abciApp, migrator,
 		*rpcSvcLogger, usersvc.WithReadTxTimeout(time.Duration(d.cfg.AppCfg.ReadTxTimeout)))
 	jsonRPCServer, err := rpcserver.NewServer(d.cfg.AppCfg.JSONRPCListenAddress,
 		*rpcServerLogger, rpcserver.WithTimeout(time.Duration(d.cfg.AppCfg.RPCTimeout)),
+		rpcserver.WithReqSizeLimit(d.cfg.AppCfg.RPCMaxReqSize),
 		rpcserver.WithCORS(), rpcserver.WithServerInfo(&usersvc.SpecInfo))
 	if err != nil {
 		failBuild(err, "unable to create json-rpc server")

internal/services/jsonrpc/server.go

@@ -53,6 +53,7 @@ type serverConfig struct {
 	timeout    time.Duration
 	enableCORS bool
 	specInfo   *openrpc.Info
+	reqSzLimit int
 }
 
 type Opt func(*serverConfig)
@@ -83,6 +84,13 @@ func WithServerInfo(specInfo *openrpc.Info) Opt {
 	}
 }
 
+// WithReqSizeLimit sets the request size limit in bytes.
+func WithReqSizeLimit(sz int) Opt {
+	return func(c *serverConfig) {
+		c.reqSzLimit = sz
+	}
+}
+
 // WithTimeout specifies a timeout on all RPC requests that when exceeded will
 // cancel the request.
 func WithTimeout(timeout time.Duration) Opt {
@@ -124,8 +132,12 @@ func checkAddr(addr string) (string, bool, error) {
 	return net.JoinHostPort(host, port), false, nil
 }
 
-// defaultWriteTimeout is the default WriteTimeout for the http.Server.
-const defaultWriteTimeout = 45 * time.Second
+const (
+	// defaultWriteTimeout is the default WriteTimeout for the http.Server.
+	defaultWriteTimeout = 45 * time.Second
+	// 4 MiB + overhead request size limit
+	defaultSzLimit = 1<<22 + 1<<14
+)
 
 var (
 	defaultSpecInfo = &openrpc.Info{
@@ -160,8 +172,9 @@ func NewServer(addr string, log log.Logger, opts ...Opt) (*Server, error) {
 	}
 
 	cfg := &serverConfig{
-		timeout:  defaultWriteTimeout,
-		specInfo: defaultSpecInfo,
+		timeout:    defaultWriteTimeout,
+		specInfo:   defaultSpecInfo,
+		reqSzLimit: defaultSzLimit,
 	}
 	for _, opt := range opts {
 		opt(cfg)
@@ -202,7 +215,7 @@ func NewServer(addr string, log log.Logger, opts ...Opt) (*Server, error) {
 
 	var h http.Handler
 	h = http.HandlerFunc(s.handlerV1)
-	h = http.MaxBytesHandler(h, 1<<22)
+	h = http.MaxBytesHandler(h, int64(cfg.reqSzLimit))
 	// amazingly, exceeding the server's write timeout does not cancel request
 	// contexts: https://github.com/golang/go/issues/59602
 	// So, we add a timeout to the Request's context.
@@ -385,9 +398,6 @@ func (s *Server) ServeOn(ctx context.Context, ln net.Listener) error {
 	return err
 }
 
-// 4 MiB request size limit
-const szLimit = 1 << 22
-
 // handlerV1 handles all https json requests. It is the http.Handler for the
 // JSON-RPC service mounted on the "/rpc/v1" endpoint. The endpoint is the same
 // for all methods since this is JSON-RPC with a "method" field of the JSON
@@ -413,8 +423,7 @@ func (s *Server) handlerV1(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	bodyReader := http.MaxBytesReader(w, r.Body, szLimit)
-	body, err := io.ReadAll(bodyReader)
+	body, err := io.ReadAll(r.Body)
 	r.Body.Close()
 	if err != nil {
 		http.Error(w, "error reading request body", http.StatusBadRequest)