rpc: enforce the 128KB request limits on websockets too

rpc/http.go

@@ -27,16 +27,16 @@ import (
 	"mime"
 	"net"
 	"net/http"
+	"strings"
 	"sync"
 	"time"
 
 	"github.com/rs/cors"
-	"strings"
 )
 
 const (
 	contentType             = "application/json"
-	maxHTTPRequestContentLength = 1024 * 128
+	maxRequestContentLength = 1024 * 128
 )
 
 var nullAddr, _ = net.ResolveTCPAddr("tcp", "127.0.0.1:0")
@@ -182,8 +182,8 @@ func validateRequest(r *http.Request) (int, error) {
 	if r.Method == http.MethodPut || r.Method == http.MethodDelete {
 		return http.StatusMethodNotAllowed, errors.New("method not allowed")
 	}
-	if r.ContentLength > maxHTTPRequestContentLength {
-		err := fmt.Errorf("content length too large (%d>%d)", r.ContentLength, maxHTTPRequestContentLength)
+	if r.ContentLength > maxRequestContentLength {
+		err := fmt.Errorf("content length too large (%d>%d)", r.ContentLength, maxRequestContentLength)
 		return http.StatusRequestEntityTooLarge, err
 	}
 	mt, _, err := mime.ParseMediaType(r.Header.Get("content-type"))

rpc/http_test.go

@@ -32,7 +32,7 @@ func TestHTTPErrorResponseWithPut(t *testing.T) {
 }
 
 func TestHTTPErrorResponseWithMaxContentLength(t *testing.T) {
-	body := make([]rune, maxHTTPRequestContentLength+1)
+	body := make([]rune, maxRequestContentLength+1)
 	testHTTPErrorResponse(t,
 		http.MethodPost, contentType, string(body), http.StatusRequestEntityTooLarge)
 }

rpc/json.go

@@ -78,10 +78,10 @@ type jsonNotification struct {
 type jsonCodec struct {
 	closer sync.Once                 // close closed channel once
 	closed chan interface{}          // closed on Close
-	decMu  sync.Mutex         // guards d
-	d      *json.Decoder      // decodes incoming requests
-	encMu  sync.Mutex         // guards e
-	e      *json.Encoder      // encodes responses
+	decMu  sync.Mutex                // guards the decoder
+	decode func(v interface{}) error // decoder to allow multiple transports
+	encMu  sync.Mutex                // guards the encoder
+	encode func(v interface{}) error // encoder to allow multiple transports
 	rw     io.ReadWriteCloser        // connection
 }
 
@@ -96,11 +96,29 @@ func (err *jsonError) ErrorCode() int {
 	return err.Code
 }
 
-// NewJSONCodec creates a new RPC server codec with support for JSON-RPC 2.0
+// NewCodec creates a new RPC server codec with support for JSON-RPC 2.0 based
+// on explicitly given encoding and decoding methods.
+func NewCodec(rwc io.ReadWriteCloser, encode, decode func(v interface{}) error) ServerCodec {
+	return &jsonCodec{
+		closed: make(chan interface{}),
+		encode: encode,
+		decode: decode,
+		rw:     rwc,
+	}
+}
+
+// NewJSONCodec creates a new RPC server codec with support for JSON-RPC 2.0.
 func NewJSONCodec(rwc io.ReadWriteCloser) ServerCodec {
-	d := json.NewDecoder(rwc)
-	d.UseNumber()
-	return &jsonCodec{closed: make(chan interface{}), d: d, e: json.NewEncoder(rwc), rw: rwc}
+	enc := json.NewEncoder(rwc)
+	dec := json.NewDecoder(rwc)
+	dec.UseNumber()
+
+	return &jsonCodec{
+		closed: make(chan interface{}),
+		encode: enc.Encode,
+		decode: dec.Decode,
+		rw:     rwc,
+	}
 }
 
 // isBatch returns true when the first non-whitespace characters is '['
@@ -123,14 +141,12 @@ func (c *jsonCodec) ReadRequestHeaders() ([]rpcRequest, bool, Error) {
 	defer c.decMu.Unlock()
 
 	var incomingMsg json.RawMessage
-	if err := c.d.Decode(&incomingMsg); err != nil {
+	if err := c.decode(&incomingMsg); err != nil {
 		return nil, false, &invalidRequestError{err.Error()}
 	}
-
 	if isBatch(incomingMsg) {
 		return parseBatchRequest(incomingMsg)
 	}
-
 	return parseRequest(incomingMsg)
 }
 
@@ -338,7 +354,7 @@ func (c *jsonCodec) Write(res interface{}) error {
 	c.encMu.Lock()
 	defer c.encMu.Unlock()
 
-	return c.e.Encode(res)
+	return c.encode(res)
 }
 
 // Close the underlying connection

rpc/websocket.go

@@ -17,8 +17,10 @@
 package rpc
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
+	"encoding/json"
 	"fmt"
 	"net"
 	"net/http"
@@ -32,6 +34,23 @@ import (
 	"gopkg.in/fatih/set.v0"
 )
 
+// websocketJSONCodec is a custom JSON codec with payload size enforcement and
+// special number parsing.
+var websocketJSONCodec = websocket.Codec{
+	// Marshal is the stock JSON marshaller used by the websocket library too.
+	Marshal: func(v interface{}) ([]byte, byte, error) {
+		msg, err := json.Marshal(v)
+		return msg, websocket.TextFrame, err
+	},
+	// Unmarshal is a specialized unmarshaller to properly convert numbers.
+	Unmarshal: func(msg []byte, payloadType byte, v interface{}) error {
+		dec := json.NewDecoder(bytes.NewReader(msg))
+		dec.UseNumber()
+
+		return dec.Decode(v)
+	},
+}
+
 // WebsocketHandler returns a handler that serves JSON-RPC to WebSocket connections.
 //
 // allowedOrigins should be a comma-separated list of allowed origin URLs.
@@ -40,7 +59,16 @@ func (srv *Server) WebsocketHandler(allowedOrigins []string) http.Handler {
 	return websocket.Server{
 		Handshake: wsHandshakeValidator(allowedOrigins),
 		Handler: func(conn *websocket.Conn) {
-			srv.ServeCodec(NewJSONCodec(conn), OptionMethodInvocation|OptionSubscriptions)
+			// Create a custom encode/decode pair to enforce payload size and number encoding
+			conn.MaxPayloadBytes = maxRequestContentLength
+
+			encoder := func(v interface{}) error {
+				return websocketJSONCodec.Send(conn, v)
+			}
+			decoder := func(v interface{}) error {
+				return websocketJSONCodec.Receive(conn, v)
+			}
+			srv.ServeCodec(NewCodec(conn, encoder, decoder), OptionMethodInvocation|OptionSubscriptions)
 		},
 	}
 }