path: root/rpc/http.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"
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "io/ioutil"
    "mime"
    "net"
    "net/http"
    "sync"
    "time"

    "github.com/rs/cors"
    "strings"
)

const (
    contentType                 = "application/json"
    maxHTTPRequestContentLength = 1024 * 128
)

var nullAddr, _ = net.ResolveTCPAddr("tcp", "127.0.0.1:0")

type httpConn struct {
    client    *http.Client
    req       *http.Request
    closeOnce sync.Once
    closed    chan struct{}
}

// httpConn is treated specially by Client.
func (hc *httpConn) LocalAddr() net.Addr              { return nullAddr }
func (hc *httpConn) RemoteAddr() net.Addr             { return nullAddr }
func (hc *httpConn) SetReadDeadline(time.Time) error  { return nil }
func (hc *httpConn) SetWriteDeadline(time.Time) error { return nil }
func (hc *httpConn) SetDeadline(time.Time) error      { return nil }
func (hc *httpConn) Write([]byte) (int, error)        { panic("Write called") }

func (hc *httpConn) Read(b []byte) (int, error) {
    <-hc.closed
    return 0, io.EOF
}

func (hc *httpConn) Close() error {
    hc.closeOnce.Do(func() { close(hc.closed) })
    return nil
}

// DialHTTPWithClient creates a new RPC client that connects to an RPC server over HTTP
// using the provided HTTP Client.
func DialHTTPWithClient(endpoint string, client *http.Client) (*Client, error) {
    req, err := http.NewRequest(http.MethodPost, endpoint, nil)
    if err != nil {
        return nil, err
    }
    req.Header.Set("Content-Type", contentType)
    req.Header.Set("Accept", contentType)

    initctx := context.Background()
    return newClient(initctx, func(context.Context) (net.Conn, error) {
        return &httpConn{client: client, req: req, closed: make(chan struct{})}, nil
    })
}

// DialHTTP creates a new RPC client that connects to an RPC server over HTTP.
func DialHTTP(endpoint string) (*Client, error) {
    return DialHTTPWithClient(endpoint, new(http.Client))
}

func (c *Client) sendHTTP(ctx context.Context, op *requestOp, msg interface{}) error {
    hc := c.writeConn.(*httpConn)
    respBody, err := hc.doRequest(ctx, msg)
    if err != nil {
        return err
    }
    defer respBody.Close()
    var respmsg jsonrpcMessage
    if err := json.NewDecoder(respBody).Decode(&respmsg); err != nil {
        return err
    }
    op.resp <- &respmsg
    return nil
}

func (c *Client) sendBatchHTTP(ctx context.Context, op *requestOp, msgs []*jsonrpcMessage) error {
    hc := c.writeConn.(*httpConn)
    respBody, err := hc.doRequest(ctx, msgs)
    if err != nil {
        return err
    }
    defer respBody.Close()
    var respmsgs []jsonrpcMessage
    if err := json.NewDecoder(respBody).Decode(&respmsgs); err != nil {
        return err
    }
    for i := 0; i < len(respmsgs); i++ {
        op.resp <- &respmsgs[i]
    }
    return nil
}

func (hc *httpConn) doRequest(ctx context.Context, msg interface{}) (io.ReadCloser, error) {
    body, err := json.Marshal(msg)
    if err != nil {
        return nil, err
    }
    req := hc.req.WithContext(ctx)
    req.Body = ioutil.NopCloser(bytes.NewReader(body))
    req.ContentLength = int64(len(body))

    resp, err := hc.client.Do(req)
    if err != nil {
        return nil, err
    }
    return resp.Body, nil
}

// httpReadWriteNopCloser wraps a io.Reader and io.Writer with a NOP Close method.
type httpReadWriteNopCloser struct {
    io.Reader
    io.Writer
}

// Close does nothing and returns always nil
func (t *httpReadWriteNopCloser) Close() error {
    return nil
}

// NewHTTPServer creates a new HTTP RPC server around an API provider.
//
// Deprecated: Server implements http.Handler
func NewHTTPServer(cors []string, vhosts []string, srv *Server) *http.Server {
    // Wrap the CORS-handler within a host-handler
    handler := newCorsHandler(srv, cors)
    handler = newVHostHandler(vhosts, handler)
    return &http.Server{Handler: handler}
}

// ServeHTTP serves JSON-RPC requests over HTTP.
func (srv *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    // Permit dumb empty requests for remote health-checks (AWS)
    if r.Method == http.MethodGet && r.ContentLength == 0 && r.URL.RawQuery == "" {
        return
    }
    if code, err := validateRequest(r); err != nil {
        http.Error(w, err.Error(), code)
        return
    }
    // All checks passed, create a codec that reads direct from the request body
    // untilEOF and writes the response to w and order the server to process a
    // single request.
    codec := NewJSONCodec(&httpReadWriteNopCloser{r.Body, w})
    defer codec.Close()

    w.Header().Set("content-type", contentType)
    srv.ServeSingleRequest(codec, OptionMethodInvocation)
}

// validateRequest returns a non-zero response code and error message if the
// request is invalid.
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)
        return http.StatusRequestEntityTooLarge, err
    }
    mt, _, err := mime.ParseMediaType(r.Header.Get("content-type"))
    if r.Method != http.MethodOptions && (err != nil || mt != contentType) {
        err := fmt.Errorf("invalid content type, only %s is supported", contentType)
        return http.StatusUnsupportedMediaType, err
    }
    return 0, nil
}

func newCorsHandler(srv *Server, allowedOrigins []string) http.Handler {
    // disable CORS support if user has not specified a custom CORS configuration
    if len(allowedOrigins) == 0 {
        return srv
    }
    c := cors.New(cors.Options{
        AllowedOrigins: allowedOrigins,
        AllowedMethods: []string{http.MethodPost, http.MethodGet},
        MaxAge:         600,
        AllowedHeaders: []string{"*"},
    })
    return c.Handler(srv)
}

// virtualHostHandler is a handler which validates the Host-header of incoming requests.
// The virtualHostHandler can prevent DNS rebinding attacks, which do not utilize CORS-headers,
// since they do in-domain requests against the RPC api. Instead, we can see on the Host-header
// which domain was used, and validate that against a whitelist.
type virtualHostHandler struct {
    vhosts map[string]struct{}
    next   http.Handler
}

// ServeHTTP serves JSON-RPC requests over HTTP, implements http.Handler
func (h *virtualHostHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    // if r.Host is not set, we can continue serving since a browser would set the Host header
    if r.Host == "" {
        h.next.ServeHTTP(w, r)
        return
    }
    host, _, err := net.SplitHostPort(r.Host)
    if err != nil {
        // Either invalid (too many colons) or no port specified
        host = r.Host
    }
    if ipAddr := net.ParseIP(host); ipAddr != nil {
        // It's an IP address, we can serve that
        h.next.ServeHTTP(w, r)
        return

    }
    // Not an ip address, but a hostname. Need to validate
    if _, exist := h.vhosts["*"]; exist {
        h.next.ServeHTTP(w, r)
        return
    }
    if _, exist := h.vhosts[host]; exist {
        h.next.ServeHTTP(w, r)
        return
    }
    http.Error(w, "invalid host specified", http.StatusForbidden)
}

func newVHostHandler(vhosts []string, next http.Handler) http.Handler {
    vhostMap := make(map[string]struct{})
    for _, allowedHost := range vhosts {
        vhostMap[strings.ToLower(allowedHost)] = struct{}{}
    }
    return &virtualHostHandler{vhostMap, next}
}