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handler.go
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handler.go
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package http
import (
"bufio"
"errors"
"fmt"
"io"
"net/http"
"net/url"
"strconv"
"strings"
cors "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/rs/cors"
context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
cmds "github.com/ipfs/go-ipfs/commands"
u "github.com/ipfs/go-ipfs/util"
)
var log = u.Logger("commands/http")
// the internal handler for the API
type internalHandler struct {
ctx cmds.Context
root *cmds.Command
cfg *ServerConfig
}
// The Handler struct is funny because we want to wrap our internal handler
// with CORS while keeping our fields.
type Handler struct {
internalHandler
corsHandler http.Handler
}
var ErrNotFound = errors.New("404 page not found")
const (
StreamErrHeader = "X-Stream-Error"
streamHeader = "X-Stream-Output"
channelHeader = "X-Chunked-Output"
uaHeader = "User-Agent"
contentTypeHeader = "Content-Type"
contentLengthHeader = "Content-Length"
contentDispHeader = "Content-Disposition"
transferEncodingHeader = "Transfer-Encoding"
applicationJson = "application/json"
applicationOctetStream = "application/octet-stream"
plainText = "text/plain"
originHeader = "origin"
)
const (
ACAOrigin = "Access-Control-Allow-Origin"
ACAMethods = "Access-Control-Allow-Methods"
ACACredentials = "Access-Control-Allow-Credentials"
)
var mimeTypes = map[string]string{
cmds.JSON: "application/json",
cmds.XML: "application/xml",
cmds.Text: "text/plain",
}
type ServerConfig struct {
// Headers is an optional map of headers that is written out.
Headers map[string][]string
// CORSOpts is a set of options for CORS headers.
CORSOpts *cors.Options
}
func skipAPIHeader(h string) bool {
switch h {
case "Access-Control-Allow-Origin":
return true
case "Access-Control-Allow-Methods":
return true
case "Access-Control-Allow-Credentials":
return true
default:
return false
}
}
func NewHandler(ctx cmds.Context, root *cmds.Command, cfg *ServerConfig) *Handler {
if cfg == nil {
panic("must provide a valid ServerConfig")
}
// Wrap the internal handler with CORS handling-middleware.
// Create a handler for the API.
internal := internalHandler{ctx, root, cfg}
c := cors.New(*cfg.CORSOpts)
return &Handler{internal, c.Handler(internal)}
}
func (i Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// Call the CORS handler which wraps the internal handler.
i.corsHandler.ServeHTTP(w, r)
}
func (i internalHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
log.Debug("Incoming API request: ", r.URL)
if !allowOrigin(r, i.cfg) || !allowReferer(r, i.cfg) {
w.WriteHeader(http.StatusForbidden)
w.Write([]byte("403 - Forbidden"))
log.Warningf("API blocked request to %s. (possible CSRF)", r.URL)
return
}
req, err := Parse(r, i.root)
if err != nil {
if err == ErrNotFound {
w.WriteHeader(http.StatusNotFound)
} else {
w.WriteHeader(http.StatusBadRequest)
}
w.Write([]byte(err.Error()))
return
}
// get the node's context to pass into the commands.
node, err := i.ctx.GetNode()
if err != nil {
s := fmt.Sprintf("cmds/http: couldn't GetNode(): %s", err)
http.Error(w, s, http.StatusInternalServerError)
return
}
//ps: take note of the name clash - commands.Context != context.Context
req.SetInvocContext(i.ctx)
ctx, cancel := context.WithCancel(node.Context())
defer cancel()
err = req.SetRootContext(ctx)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
// call the command
res := i.root.Call(req)
// set user's headers first.
for k, v := range i.cfg.Headers {
if !skipAPIHeader(k) {
w.Header()[k] = v
}
}
// now handle responding to the client properly
sendResponse(w, r, res, req)
}
func guessMimeType(res cmds.Response) (string, error) {
// Try to guess mimeType from the encoding option
enc, found, err := res.Request().Option(cmds.EncShort).String()
if err != nil {
return "", err
}
if !found {
return "", errors.New("no encoding option set")
}
return mimeTypes[enc], nil
}
func sendResponse(w http.ResponseWriter, r *http.Request, res cmds.Response, req cmds.Request) {
mime, err := guessMimeType(res)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
status := http.StatusOK
// if response contains an error, write an HTTP error status code
if e := res.Error(); e != nil {
if e.Code == cmds.ErrClient {
status = http.StatusBadRequest
} else {
status = http.StatusInternalServerError
}
// NOTE: The error will actually be written out by the reader below
}
out, err := res.Reader()
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
h := w.Header()
if res.Length() > 0 {
h.Set(contentLengthHeader, strconv.FormatUint(res.Length(), 10))
}
if _, ok := res.Output().(io.Reader); ok {
// we don't set the Content-Type for streams, so that browsers can MIME-sniff the type themselves
// we set this header so clients have a way to know this is an output stream
// (not marshalled command output)
mime = ""
h.Set(streamHeader, "1")
}
// if output is a channel and user requested streaming channels,
// use chunk copier for the output
_, isChan := res.Output().(chan interface{})
if !isChan {
_, isChan = res.Output().(<-chan interface{})
}
streamChans, _, _ := req.Option("stream-channels").Bool()
if isChan {
h.Set(channelHeader, "1")
if streamChans {
// streaming output from a channel will always be json objects
mime = applicationJson
}
}
if mime != "" {
h.Set(contentTypeHeader, mime)
}
h.Set(transferEncodingHeader, "chunked")
if r.Method == "HEAD" { // after all the headers.
return
}
if err := writeResponse(status, w, out); err != nil {
if strings.Contains(err.Error(), "broken pipe") {
log.Info("client disconnect while writing stream ", err)
return
}
log.Error("error while writing stream ", err)
}
}
// Copies from an io.Reader to a http.ResponseWriter.
// Flushes chunks over HTTP stream as they are read (if supported by transport).
func writeResponse(status int, w http.ResponseWriter, out io.Reader) error {
// hijack the connection so we can write our own chunked output and trailers
hijacker, ok := w.(http.Hijacker)
if !ok {
log.Error("Failed to create hijacker! cannot continue!")
return errors.New("Could not create hijacker")
}
conn, writer, err := hijacker.Hijack()
if err != nil {
return err
}
defer conn.Close()
// write status
writer.WriteString(fmt.Sprintf("HTTP/1.1 %d %s\r\n", status, http.StatusText(status)))
// Write out headers
w.Header().Write(writer)
// end of headers
writer.WriteString("\r\n")
// write body
streamErr := writeChunks(out, writer)
// close body
writer.WriteString("0\r\n")
// if there was a stream error, write out an error trailer. hopefully
// the client will pick it up!
if streamErr != nil {
writer.WriteString(StreamErrHeader + ": " + sanitizedErrStr(streamErr) + "\r\n")
}
writer.WriteString("\r\n") // close response
writer.Flush()
return streamErr
}
func writeChunks(r io.Reader, w *bufio.ReadWriter) error {
buf := make([]byte, 32*1024)
for {
n, err := r.Read(buf)
if n > 0 {
length := fmt.Sprintf("%x\r\n", n)
w.WriteString(length)
_, err := w.Write(buf[0:n])
if err != nil {
return err
}
w.WriteString("\r\n")
w.Flush()
}
if err != nil && err != io.EOF {
return err
}
if err == io.EOF {
break
}
}
return nil
}
func sanitizedErrStr(err error) string {
s := err.Error()
s = strings.Split(s, "\n")[0]
s = strings.Split(s, "\r")[0]
return s
}
// allowOrigin just stops the request if the origin is not allowed.
// the CORS middleware apparently does not do this for us...
func allowOrigin(r *http.Request, cfg *ServerConfig) bool {
origin := r.Header.Get("Origin")
// curl, or ipfs shell, typing it in manually, or clicking link
// NOT in a browser. this opens up a hole. we should close it,
// but right now it would break things. TODO
if origin == "" {
return true
}
for _, o := range cfg.CORSOpts.AllowedOrigins {
if o == "*" { // ok! you asked for it!
return true
}
if o == origin { // allowed explicitly
return true
}
}
return false
}
// allowReferer this is here to prevent some CSRF attacks that
// the API would be vulnerable to. We check that the Referer
// is allowed by CORS Origin (origins and referrers here will
// work similarly in the normla uses of the API).
// See discussion at https://github.com/ipfs/go-ipfs/issues/1532
func allowReferer(r *http.Request, cfg *ServerConfig) bool {
referer := r.Referer()
// curl, or ipfs shell, typing it in manually, or clicking link
// NOT in a browser. this opens up a hole. we should close it,
// but right now it would break things. TODO
if referer == "" {
return true
}
u, err := url.Parse(referer)
if err != nil {
// bad referer. but there _is_ something, so bail.
log.Debug("failed to parse referer: ", referer)
// debug because referer comes straight from the client. dont want to
// let people DOS by putting a huge referer that gets stored in log files.
return false
}
origin := u.Scheme + "://" + u.Host
// check CORS ACAOs and pretend Referer works like an origin.
// this is valid for many (most?) sane uses of the API in
// other applications, and will have the desired effect.
for _, o := range cfg.CORSOpts.AllowedOrigins {
if o == "*" { // ok! you asked for it!
return true
}
// referer is allowed explicitly
if o == origin {
return true
}
}
return false
}