path: root/rpc/websocket.go

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package rpc

import (
    "bytes"
    "context"
    "crypto/tls"
    "encoding/base64"
    "encoding/json"
    "errors"
    "fmt"
    "net"
    "net/http"
    "net/url"
    "os"
    "strings"
    "time"

    mapset "github.com/deckarep/golang-set"
    "github.com/ethereum/go-ethereum/log"
    "golang.org/x/net/websocket"
)

// 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.
// To allow connections with any origin, pass "*".
func (s *Server) WebsocketHandler(allowedOrigins []string) http.Handler {
    return websocket.Server{
        Handshake: wsHandshakeValidator(allowedOrigins),
        Handler: func(conn *websocket.Conn) {
            codec := newWebsocketCodec(conn)
            s.ServeCodec(codec, OptionMethodInvocation|OptionSubscriptions)
        },
    }
}

func newWebsocketCodec(conn *websocket.Conn) ServerCodec {
    // 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)
    }
    rpcconn := Conn(conn)
    if conn.IsServerConn() {
        // Override remote address with the actual socket address because
        // package websocket crashes if there is no request origin.
        addr := conn.Request().RemoteAddr
        if wsaddr := conn.RemoteAddr().(*websocket.Addr); wsaddr.URL != nil {
            // Add origin if present.
            addr += "(" + wsaddr.URL.String() + ")"
        }
        rpcconn = connWithRemoteAddr{conn, addr}
    }
    return NewCodec(rpcconn, encoder, decoder)
}

// NewWSServer creates a new websocket RPC server around an API provider.
//
// Deprecated: use Server.WebsocketHandler
func NewWSServer(allowedOrigins []string, srv *Server) *http.Server {
    return &http.Server{Handler: srv.WebsocketHandler(allowedOrigins)}
}

// wsHandshakeValidator returns a handler that verifies the origin during the
// websocket upgrade process. When a '*' is specified as an allowed origins all
// connections are accepted.
func wsHandshakeValidator(allowedOrigins []string) func(*websocket.Config, *http.Request) error {
    origins := mapset.NewSet()
    allowAllOrigins := false

    for _, origin := range allowedOrigins {
        if origin == "*" {
            allowAllOrigins = true
        }
        if origin != "" {
            origins.Add(strings.ToLower(origin))
        }
    }

    // allow localhost if no allowedOrigins are specified.
    if len(origins.ToSlice()) == 0 {
        origins.Add("http://localhost")
        if hostname, err := os.Hostname(); err == nil {
            origins.Add("http://" + strings.ToLower(hostname))
        }
    }

    log.Debug(fmt.Sprintf("Allowed origin(s) for WS RPC interface %v", origins.ToSlice()))

    f := func(cfg *websocket.Config, req *http.Request) error {
        // Skip origin verification if no Origin header is present. The origin check
        // is supposed to protect against browser based attacks. Browsers always set
        // Origin. Non-browser software can put anything in origin and checking it doesn't
        // provide additional security.
        if _, ok := req.Header["Origin"]; !ok {
            return nil
        }
        // Verify origin against whitelist.
        origin := strings.ToLower(req.Header.Get("Origin"))
        if allowAllOrigins || origins.Contains(origin) {
            return nil
        }
        log.Warn("Rejected WebSocket connection", "origin", origin)
        return errors.New("origin not allowed")
    }

    return f
}

func wsGetConfig(endpoint, origin string) (*websocket.Config, error) {
    if origin == "" {
        var err error
        if origin, err = os.Hostname(); err != nil {
            return nil, err
        }
        if strings.HasPrefix(endpoint, "wss") {
            origin = "https://" + strings.ToLower(origin)
        } else {
            origin = "http://" + strings.ToLower(origin)
        }
    }
    config, err := websocket.NewConfig(endpoint, origin)
    if err != nil {
        return nil, err
    }

    if config.Location.User != nil {
        b64auth := base64.StdEncoding.EncodeToString([]byte(config.Location.User.String()))
        config.Header.Add("Authorization", "Basic "+b64auth)
        config.Location.User = nil
    }
    return config, nil
}

// DialWebsocket creates a new RPC client that communicates with a JSON-RPC server
// that is listening on the given endpoint.
//
// The context is used for the initial connection establishment. It does not
// affect subsequent interactions with the client.
func DialWebsocket(ctx context.Context, endpoint, origin string) (*Client, error) {
    config, err := wsGetConfig(endpoint, origin)
    if err != nil {
        return nil, err
    }

    return newClient(ctx, func(ctx context.Context) (ServerCodec, error) {
        conn, err := wsDialContext(ctx, config)
        if err != nil {
            return nil, err
        }
        return newWebsocketCodec(conn), nil
    })
}

func wsDialContext(ctx context.Context, config *websocket.Config) (*websocket.Conn, error) {
    var conn net.Conn
    var err error
    switch config.Location.Scheme {
    case "ws":
        conn, err = dialContext(ctx, "tcp", wsDialAddress(config.Location))
    case "wss":
        dialer := contextDialer(ctx)
        conn, err = tls.DialWithDialer(dialer, "tcp", wsDialAddress(config.Location), config.TlsConfig)
    default:
        err = websocket.ErrBadScheme
    }
    if err != nil {
        return nil, err
    }
    ws, err := websocket.NewClient(config, conn)
    if err != nil {
        conn.Close()
        return nil, err
    }
    return ws, err
}

var wsPortMap = map[string]string{"ws": "80", "wss": "443"}

func wsDialAddress(location *url.URL) string {
    if _, ok := wsPortMap[location.Scheme]; ok {
        if _, _, err := net.SplitHostPort(location.Host); err != nil {
            return net.JoinHostPort(location.Host, wsPortMap[location.Scheme])
        }
    }
    return location.Host
}

func dialContext(ctx context.Context, network, addr string) (net.Conn, error) {
    d := &net.Dialer{KeepAlive: tcpKeepAliveInterval}
    return d.DialContext(ctx, network, addr)
}

func contextDialer(ctx context.Context) *net.Dialer {
    dialer := &net.Dialer{Cancel: ctx.Done(), KeepAlive: tcpKeepAliveInterval}
    if deadline, ok := ctx.Deadline(); ok {
        dialer.Deadline = deadline
    } else {
        dialer.Deadline = time.Now().Add(defaultDialTimeout)
    }
    return dialer
}