// serveBlobRef sends 'blobref' to 'conn' as directed by the Range header in 'req'
func serveBlobRef(conn http.ResponseWriter, req *http.Request,
blobRef *blobref.BlobRef, fetcher blobref.StreamingFetcher) {
if w, ok := fetcher.(blobserver.ContextWrapper); ok {
fetcher = w.WrapContext(req)
}
file, size, err := fetcher.FetchStreaming(blobRef)
switch err {
case nil:
break
case os.ENOENT:
conn.WriteHeader(http.StatusNotFound)
fmt.Fprintf(conn, "Object not found.")
return
default:
httputil.ServerError(conn, err)
return
}
defer file.Close()
seeker, isSeeker := file.(io.Seeker)
reqRange := httprange.FromRequest(req)
if reqRange.SkipBytes() != 0 && isSeeker {
// TODO: set the Range-specific response headers too,
// acknowledging that we honored the content range
// request.
_, err = seeker.Seek(reqRange.SkipBytes(), 0)
if err != nil {
httputil.ServerError(conn, err)
return
}
}
var input io.Reader = file
if reqRange.LimitBytes() != -1 {
input = io.LimitReader(file, reqRange.LimitBytes())
}
remainBytes := size - reqRange.SkipBytes()
if reqRange.LimitBytes() != -1 &&
reqRange.LimitBytes() < remainBytes {
remainBytes = reqRange.LimitBytes()
}
// Assume this generic content type by default. For better
// demos we'll try to sniff and guess the "right" MIME type in
// certain cases (no Range requests, etc) but this isn't part
// of the Camli spec at all. We just do it to ease demos.
contentType := "application/octet-stream"
if reqRange.IsWholeFile() {
const peekSize = 1024
bufReader, _ := bufio.NewReaderSize(input, peekSize)
header, _ := bufReader.Peek(peekSize)
if len(header) >= 8 {
switch {
case isValidUtf8(string(header)):
contentType = "text/plain; charset=utf-8"
case bytes.HasPrefix(header, []byte{0xff, 0xd8, 0xff, 0xe2}):
contentType = "image/jpeg"
case bytes.HasPrefix(header, []byte{0x89, 0x50, 0x4e, 0x47, 0xd, 0xa, 0x1a, 0xa}):
contentType = "image/png"
}
}
input = bufReader
conn.Header().Set("Content-Length", strconv.Itoa64(size))
}
conn.Header().Set("Content-Type", contentType)
if !reqRange.IsWholeFile() {
conn.Header().Set("Content-Range",
fmt.Sprintf("bytes %d-%d/%d", reqRange.SkipBytes(),
reqRange.SkipBytes()+remainBytes,
size))
conn.WriteHeader(http.StatusPartialContent)
}
bytesCopied, err := io.Copy(conn, input)
// If there's an error at this point, it's too late to tell the client,
// as they've already been receiving bytes. But they should be smart enough
// to verify the digest doesn't match. But we close the (chunked) response anyway,
// to further signal errors.
killConnection := func() {
if hj, ok := conn.(http.Hijacker); ok {
if closer, _, err := hj.Hijack(); err != nil {
closer.Close()
}
}
}
if err != nil {
fmt.Fprintf(os.Stderr, "Error sending file: %v, err=%v\n", blobRef, err)
killConnection()
return
}
if bytesCopied != remainBytes {
fmt.Fprintf(os.Stderr, "Error sending file: %v, copied=%d, not %d\n", blobRef,
bytesCopied, remainBytes)
killConnection()
return
}
}
// Unauthenticated user. Be paranoid.
func handleGetViaSharing(conn http.ResponseWriter, req *http.Request,
blobRef *blobref.BlobRef, fetcher blobref.StreamingFetcher) {
if w, ok := fetcher.(blobserver.ContextWrapper); ok {
fetcher = w.WrapContext(req)
}
viaPathOkay := false
startTime := time.Nanoseconds()
defer func() {
if !viaPathOkay {
// Insert a delay, to hide timing attacks probing
// for the existence of blobs.
sleep := fetchFailureDelayNs - (time.Nanoseconds() - startTime)
if sleep > 0 {
time.Sleep(sleep)
}
}
}()
viaBlobs := make([]*blobref.BlobRef, 0)
if via := req.FormValue("via"); via != "" {
for _, vs := range strings.Split(via, ",") {
if br := blobref.Parse(vs); br == nil {
httputil.BadRequestError(conn, "Malformed blobref in via param")
return
} else {
viaBlobs = append(viaBlobs, br)
}
}
}
fetchChain := make([]*blobref.BlobRef, 0)
fetchChain = append(fetchChain, viaBlobs...)
fetchChain = append(fetchChain, blobRef)
for i, br := range fetchChain {
switch i {
case 0:
file, size, err := fetcher.FetchStreaming(br)
if err != nil {
log.Printf("Fetch chain 0 of %s failed: %v", br.String(), err)
auth.SendUnauthorized(conn)
return
}
defer file.Close()
if size > maxJsonSize {
log.Printf("Fetch chain 0 of %s too large", br.String())
auth.SendUnauthorized(conn)
return
}
jd := json.NewDecoder(file)
m := make(map[string]interface{})
if err := jd.Decode(&m); err != nil {
log.Printf("Fetch chain 0 of %s wasn't JSON: %v", br.String(), err)
auth.SendUnauthorized(conn)
return
}
if m["camliType"].(string) != "share" {
log.Printf("Fetch chain 0 of %s wasn't a share", br.String())
auth.SendUnauthorized(conn)
return
}
if len(fetchChain) > 1 && fetchChain[1].String() != m["target"].(string) {
log.Printf("Fetch chain 0->1 (%s -> %q) unauthorized, expected hop to %q",
br.String(), fetchChain[1].String(), m["target"])
auth.SendUnauthorized(conn)
return
}
case len(fetchChain) - 1:
// Last one is fine (as long as its path up to here has been proven, and it's
// not the first thing in the chain)
continue
default:
file, _, err := fetcher.FetchStreaming(br)
if err != nil {
log.Printf("Fetch chain %d of %s failed: %v", i, br.String(), err)
auth.SendUnauthorized(conn)
return
}
defer file.Close()
lr := io.LimitReader(file, maxJsonSize)
slurpBytes, err := ioutil.ReadAll(lr)
if err != nil {
log.Printf("Fetch chain %d of %s failed in slurp: %v", i, br.String(), err)
auth.SendUnauthorized(conn)
return
}
saught := fetchChain[i+1].String()
if bytes.IndexAny(slurpBytes, saught) == -1 {
log.Printf("Fetch chain %d of %s failed; no reference to %s",
i, br.String(), saught)
auth.SendUnauthorized(conn)
return
}
}
}
viaPathOkay = true
serveBlobRef(conn, req, blobRef, fetcher)
}