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minio/cmd/object-api-utils.go

828 lines
24 KiB

/*
* MinIO Cloud Storage, (C) 2015-2019 MinIO, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cmd
import (
"bytes"
"context"
"encoding/hex"
"fmt"
"io"
"math/rand"
"net"
"net/http"
"path"
"runtime"
"strconv"
"strings"
"sync"
"time"
"unicode/utf8"
snappy "github.com/golang/snappy"
"github.com/minio/minio-go/v6/pkg/s3utils"
"github.com/minio/minio/cmd/crypto"
xhttp "github.com/minio/minio/cmd/http"
"github.com/minio/minio/cmd/logger"
"github.com/minio/minio/pkg/dns"
"github.com/minio/minio/pkg/hash"
"github.com/minio/minio/pkg/ioutil"
"github.com/minio/minio/pkg/wildcard"
"github.com/skyrings/skyring-common/tools/uuid"
)
const (
// MinIO meta bucket.
minioMetaBucket = ".minio.sys"
// Multipart meta prefix.
mpartMetaPrefix = "multipart"
// MinIO Multipart meta prefix.
minioMetaMultipartBucket = minioMetaBucket + SlashSeparator + mpartMetaPrefix
// MinIO Tmp meta prefix.
minioMetaTmpBucket = minioMetaBucket + "/tmp"
// DNS separator (period), used for bucket name validation.
dnsDelimiter = "."
)
// isMinioBucket returns true if given bucket is a MinIO internal
// bucket and false otherwise.
func isMinioMetaBucketName(bucket string) bool {
return bucket == minioMetaBucket ||
bucket == minioMetaMultipartBucket ||
bucket == minioMetaTmpBucket
}
// IsValidBucketName verifies that a bucket name is in accordance with
// Amazon's requirements (i.e. DNS naming conventions). It must be 3-63
// characters long, and it must be a sequence of one or more labels
// separated by periods. Each label can contain lowercase ascii
// letters, decimal digits and hyphens, but must not begin or end with
// a hyphen. See:
// http://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html
func IsValidBucketName(bucket string) bool {
// Special case when bucket is equal to one of the meta buckets.
if isMinioMetaBucketName(bucket) {
return true
}
if len(bucket) < 3 || len(bucket) > 63 {
return false
}
// Split on dot and check each piece conforms to rules.
allNumbers := true
pieces := strings.Split(bucket, dnsDelimiter)
for _, piece := range pieces {
if len(piece) == 0 || piece[0] == '-' ||
piece[len(piece)-1] == '-' {
// Current piece has 0-length or starts or
// ends with a hyphen.
return false
}
// Now only need to check if each piece is a valid
// 'label' in AWS terminology and if the bucket looks
// like an IP address.
isNotNumber := false
for i := 0; i < len(piece); i++ {
switch {
case (piece[i] >= 'a' && piece[i] <= 'z' ||
piece[i] == '-'):
// Found a non-digit character, so
// this piece is not a number.
isNotNumber = true
case piece[i] >= '0' && piece[i] <= '9':
// Nothing to do.
default:
// Found invalid character.
return false
}
}
allNumbers = allNumbers && !isNotNumber
}
// Does the bucket name look like an IP address?
return !(len(pieces) == 4 && allNumbers)
}
// IsValidObjectName verifies an object name in accordance with Amazon's
// requirements. It cannot exceed 1024 characters and must be a valid UTF8
// string.
//
// See:
// http://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html
//
// You should avoid the following characters in a key name because of
// significant special handling for consistency across all
// applications.
//
// Rejects strings with following characters.
//
// - Backslash ("\")
//
// additionally minio does not support object names with trailing SlashSeparator.
func IsValidObjectName(object string) bool {
if len(object) == 0 {
return false
}
if hasSuffix(object, SlashSeparator) {
return false
}
return IsValidObjectPrefix(object)
}
// IsValidObjectPrefix verifies whether the prefix is a valid object name.
// Its valid to have a empty prefix.
func IsValidObjectPrefix(object string) bool {
if hasBadPathComponent(object) {
return false
}
if !utf8.ValidString(object) {
return false
}
// Reject unsupported characters in object name.
if strings.ContainsAny(object, "\\") {
return false
}
return true
}
// checkObjectNameForLengthAndSlash -check for the validity of object name length and prefis as slash
func checkObjectNameForLengthAndSlash(bucket, object string) error {
// Check for the length of object name
if len(object) > 1024 {
return ObjectNameTooLong{
Bucket: bucket,
Object: object,
}
}
// Check for slash as prefix in object name
if hasPrefix(object, SlashSeparator) {
return ObjectNamePrefixAsSlash{
Bucket: bucket,
Object: object,
}
}
return nil
}
// SlashSeparator - slash separator.
const SlashSeparator = "/"
// retainSlash - retains slash from a path.
func retainSlash(s string) string {
return strings.TrimSuffix(s, SlashSeparator) + SlashSeparator
}
// pathJoin - like path.Join() but retains trailing SlashSeparator of the last element
func pathJoin(elem ...string) string {
trailingSlash := ""
if len(elem) > 0 {
if hasSuffix(elem[len(elem)-1], SlashSeparator) {
trailingSlash = SlashSeparator
}
}
return path.Join(elem...) + trailingSlash
}
// mustGetUUID - get a random UUID.
func mustGetUUID() string {
uuid, err := uuid.New()
if err != nil {
logger.CriticalIf(context.Background(), err)
}
return uuid.String()
}
// Create an s3 compatible MD5sum for complete multipart transaction.
func getCompleteMultipartMD5(parts []CompletePart) string {
var finalMD5Bytes []byte
for _, part := range parts {
md5Bytes, err := hex.DecodeString(canonicalizeETag(part.ETag))
if err != nil {
finalMD5Bytes = append(finalMD5Bytes, []byte(part.ETag)...)
} else {
finalMD5Bytes = append(finalMD5Bytes, md5Bytes...)
}
}
s3MD5 := fmt.Sprintf("%s-%d", getMD5Hash(finalMD5Bytes), len(parts))
return s3MD5
}
// Clean unwanted fields from metadata
func cleanMetadata(metadata map[string]string) map[string]string {
// Remove STANDARD StorageClass
metadata = removeStandardStorageClass(metadata)
// Clean meta etag keys 'md5Sum', 'etag', "expires".
return cleanMetadataKeys(metadata, "md5Sum", "etag", "expires")
}
// Filter X-Amz-Storage-Class field only if it is set to STANDARD.
// This is done since AWS S3 doesn't return STANDARD Storage class as response header.
func removeStandardStorageClass(metadata map[string]string) map[string]string {
if metadata[amzStorageClass] == standardStorageClass {
delete(metadata, amzStorageClass)
}
return metadata
}
// cleanMetadataKeys takes keyNames to be filtered
// and returns a new map with all the entries with keyNames removed.
func cleanMetadataKeys(metadata map[string]string, keyNames ...string) map[string]string {
var newMeta = make(map[string]string)
for k, v := range metadata {
if contains(keyNames, k) {
continue
}
newMeta[k] = v
}
return newMeta
}
// Extracts etag value from the metadata.
func extractETag(metadata map[string]string) string {
// md5Sum tag is kept for backward compatibility.
etag, ok := metadata["md5Sum"]
if !ok {
etag = metadata["etag"]
}
// Success.
return etag
}
// Prefix matcher string matches prefix in a platform specific way.
// For example on windows since its case insensitive we are supposed
// to do case insensitive checks.
func hasPrefix(s string, prefix string) bool {
if runtime.GOOS == globalWindowsOSName {
return strings.HasPrefix(strings.ToLower(s), strings.ToLower(prefix))
}
return strings.HasPrefix(s, prefix)
}
// Suffix matcher string matches suffix in a platform specific way.
// For example on windows since its case insensitive we are supposed
// to do case insensitive checks.
func hasSuffix(s string, suffix string) bool {
if runtime.GOOS == globalWindowsOSName {
return strings.HasSuffix(strings.ToLower(s), strings.ToLower(suffix))
}
return strings.HasSuffix(s, suffix)
}
// Validates if two strings are equal.
func isStringEqual(s1 string, s2 string) bool {
if runtime.GOOS == globalWindowsOSName {
return strings.EqualFold(s1, s2)
}
return s1 == s2
}
// Ignores all reserved bucket names or invalid bucket names.
func isReservedOrInvalidBucket(bucketEntry string, strict bool) bool {
bucketEntry = strings.TrimSuffix(bucketEntry, SlashSeparator)
if strict {
if err := s3utils.CheckValidBucketNameStrict(bucketEntry); err != nil {
return true
}
} else {
if err := s3utils.CheckValidBucketName(bucketEntry); err != nil {
return true
}
}
return isMinioMetaBucket(bucketEntry) || isMinioReservedBucket(bucketEntry)
}
// Returns true if input bucket is a reserved minio meta bucket '.minio.sys'.
func isMinioMetaBucket(bucketName string) bool {
return bucketName == minioMetaBucket
}
// Returns true if input bucket is a reserved minio bucket 'minio'.
func isMinioReservedBucket(bucketName string) bool {
return bucketName == minioReservedBucket
}
// returns a slice of hosts by reading a slice of DNS records
func getHostsSlice(records []dns.SrvRecord) []string {
var hosts []string
for _, r := range records {
hosts = append(hosts, net.JoinHostPort(r.Host, fmt.Sprintf("%d", r.Port)))
}
return hosts
}
// returns a host (and corresponding port) from a slice of DNS records
func getHostFromSrv(records []dns.SrvRecord) string {
rand.Seed(time.Now().Unix())
srvRecord := records[rand.Intn(len(records))]
return net.JoinHostPort(srvRecord.Host, fmt.Sprintf("%d", srvRecord.Port))
}
// IsCompressed returns true if the object is marked as compressed.
func (o ObjectInfo) IsCompressed() bool {
_, ok := o.UserDefined[ReservedMetadataPrefix+"compression"]
return ok
}
// GetActualSize - read the decompressed size from the meta json.
func (o ObjectInfo) GetActualSize() int64 {
metadata := o.UserDefined
sizeStr, ok := metadata[ReservedMetadataPrefix+"actual-size"]
if ok {
size, err := strconv.ParseInt(sizeStr, 10, 64)
if err == nil {
return size
}
}
return -1
}
// Disabling compression for encrypted enabled requests.
// Using compression and encryption together enables room for side channel attacks.
// Eliminate non-compressible objects by extensions/content-types.
func isCompressible(header http.Header, object string) bool {
if hasServerSideEncryptionHeader(header) || excludeForCompression(header, object) {
return false
}
return true
}
// Eliminate the non-compressible objects.
func excludeForCompression(header http.Header, object string) bool {
objStr := object
contentType := header.Get(xhttp.ContentType)
if globalIsCompressionEnabled {
// We strictly disable compression for standard extensions/content-types (`compressed`).
if hasStringSuffixInSlice(objStr, standardExcludeCompressExtensions) || hasPattern(standardExcludeCompressContentTypes, contentType) {
return true
}
// Filter compression includes.
if len(globalCompressExtensions) > 0 || len(globalCompressMimeTypes) > 0 {
extensions := globalCompressExtensions
mimeTypes := globalCompressMimeTypes
if hasStringSuffixInSlice(objStr, extensions) || hasPattern(mimeTypes, contentType) {
return false
}
return true
}
return false
}
return true
}
// Utility which returns if a string is present in the list.
func hasStringSuffixInSlice(str string, list []string) bool {
for _, v := range list {
if strings.HasSuffix(str, v) {
return true
}
}
return false
}
// Returns true if any of the given wildcard patterns match the matchStr.
func hasPattern(patterns []string, matchStr string) bool {
for _, pattern := range patterns {
if ok := wildcard.MatchSimple(pattern, matchStr); ok {
return true
}
}
return false
}
// Returns the part file name which matches the partNumber and etag.
func getPartFile(entries []string, partNumber int, etag string) string {
for _, entry := range entries {
if strings.HasPrefix(entry, fmt.Sprintf("%.5d.%s.", partNumber, etag)) {
return entry
}
}
return ""
}
// Returs the compressed offset which should be skipped.
func getCompressedOffsets(objectInfo ObjectInfo, offset int64) (int64, int64) {
var compressedOffset int64
var skipLength int64
var cumulativeActualSize int64
if len(objectInfo.Parts) > 0 {
for _, part := range objectInfo.Parts {
cumulativeActualSize += part.ActualSize
if cumulativeActualSize <= offset {
compressedOffset += part.Size
} else {
skipLength = cumulativeActualSize - part.ActualSize
break
}
}
}
return compressedOffset, offset - skipLength
}
// byBucketName is a collection satisfying sort.Interface.
type byBucketName []BucketInfo
func (d byBucketName) Len() int { return len(d) }
func (d byBucketName) Swap(i, j int) { d[i], d[j] = d[j], d[i] }
func (d byBucketName) Less(i, j int) bool { return d[i].Name < d[j].Name }
// GetObjectReader is a type that wraps a reader with a lock to
// provide a ReadCloser interface that unlocks on Close()
type GetObjectReader struct {
ObjInfo ObjectInfo
pReader io.Reader
cleanUpFns []func()
precondFn func(ObjectInfo, string) bool
once sync.Once
}
// NewGetObjectReaderFromReader sets up a GetObjectReader with a given
// reader. This ignores any object properties.
func NewGetObjectReaderFromReader(r io.Reader, oi ObjectInfo, pcfn CheckCopyPreconditionFn, cleanupFns ...func()) (*GetObjectReader, error) {
if pcfn != nil {
if ok := pcfn(oi, ""); ok {
// Call the cleanup funcs
for i := len(cleanupFns) - 1; i >= 0; i-- {
cleanupFns[i]()
}
return nil, PreConditionFailed{}
}
}
return &GetObjectReader{
ObjInfo: oi,
pReader: r,
cleanUpFns: cleanupFns,
precondFn: pcfn,
}, nil
}
// ObjReaderFn is a function type that takes a reader and returns
// GetObjectReader and an error. Request headers are passed to provide
// encryption parameters. cleanupFns allow cleanup funcs to be
// registered for calling after usage of the reader.
type ObjReaderFn func(inputReader io.Reader, h http.Header, pcfn CheckCopyPreconditionFn, cleanupFns ...func()) (r *GetObjectReader, err error)
// NewGetObjectReader creates a new GetObjectReader. The cleanUpFns
// are called on Close() in reverse order as passed here. NOTE: It is
// assumed that clean up functions do not panic (otherwise, they may
// not all run!).
func NewGetObjectReader(rs *HTTPRangeSpec, oi ObjectInfo, pcfn CheckCopyPreconditionFn, cleanUpFns ...func()) (
fn ObjReaderFn, off, length int64, err error) {
// Call the clean-up functions immediately in case of exit
// with error
defer func() {
if err != nil {
for i := len(cleanUpFns) - 1; i >= 0; i-- {
cleanUpFns[i]()
}
}
}()
isEncrypted := crypto.IsEncrypted(oi.UserDefined)
isCompressed := oi.IsCompressed()
var skipLen int64
// Calculate range to read (different for
// e.g. encrypted/compressed objects)
switch {
case isEncrypted:
var seqNumber uint32
var partStart int
off, length, skipLen, seqNumber, partStart, err = oi.GetDecryptedRange(rs)
if err != nil {
return nil, 0, 0, err
}
var decSize int64
decSize, err = oi.DecryptedSize()
if err != nil {
return nil, 0, 0, err
}
var decRangeLength int64
decRangeLength, err = rs.GetLength(decSize)
if err != nil {
return nil, 0, 0, err
}
// We define a closure that performs decryption given
// a reader that returns the desired range of
// encrypted bytes. The header parameter is used to
// provide encryption parameters.
fn = func(inputReader io.Reader, h http.Header, pcfn CheckCopyPreconditionFn, cFns ...func()) (r *GetObjectReader, err error) {
copySource := h.Get(crypto.SSECopyAlgorithm) != ""
cFns = append(cleanUpFns, cFns...)
// Attach decrypter on inputReader
var decReader io.Reader
decReader, err = DecryptBlocksRequestR(inputReader, h,
off, length, seqNumber, partStart, oi, copySource)
if err != nil {
// Call the cleanup funcs
for i := len(cFns) - 1; i >= 0; i-- {
cFns[i]()
}
return nil, err
}
encETag := oi.ETag
oi.ETag = getDecryptedETag(h, oi, copySource) // Decrypt the ETag before top layer consumes this value.
if pcfn != nil {
if ok := pcfn(oi, encETag); ok {
// Call the cleanup funcs
for i := len(cFns) - 1; i >= 0; i-- {
cFns[i]()
}
return nil, PreConditionFailed{}
}
}
// Apply the skipLen and limit on the
// decrypted stream
decReader = io.LimitReader(ioutil.NewSkipReader(decReader, skipLen), decRangeLength)
// Assemble the GetObjectReader
r = &GetObjectReader{
ObjInfo: oi,
pReader: decReader,
cleanUpFns: cFns,
precondFn: pcfn,
}
return r, nil
}
case isCompressed:
// Read the decompressed size from the meta.json.
actualSize := oi.GetActualSize()
if actualSize < 0 {
return nil, 0, 0, errInvalidDecompressedSize
}
off, length = int64(0), oi.Size
decOff, decLength := int64(0), actualSize
if rs != nil {
off, length, err = rs.GetOffsetLength(actualSize)
if err != nil {
return nil, 0, 0, err
}
// Incase of range based queries on multiparts, the offset and length are reduced.
off, decOff = getCompressedOffsets(oi, off)
decLength = length
length = oi.Size - off
// For negative length we read everything.
if decLength < 0 {
decLength = actualSize - decOff
}
// Reply back invalid range if the input offset and length fall out of range.
if decOff > actualSize || decOff+decLength > actualSize {
return nil, 0, 0, errInvalidRange
}
}
fn = func(inputReader io.Reader, _ http.Header, pcfn CheckCopyPreconditionFn, cFns ...func()) (r *GetObjectReader, err error) {
cFns = append(cleanUpFns, cFns...)
if pcfn != nil {
if ok := pcfn(oi, ""); ok {
// Call the cleanup funcs
for i := len(cFns) - 1; i >= 0; i-- {
cFns[i]()
}
return nil, PreConditionFailed{}
}
}
// Decompression reader.
snappyReader := snappy.NewReader(inputReader)
// Apply the skipLen and limit on the
// decompressed stream
decReader := io.LimitReader(ioutil.NewSkipReader(snappyReader, decOff), decLength)
oi.Size = decLength
// Assemble the GetObjectReader
r = &GetObjectReader{
ObjInfo: oi,
pReader: decReader,
cleanUpFns: cFns,
precondFn: pcfn,
}
return r, nil
}
default:
off, length, err = rs.GetOffsetLength(oi.Size)
if err != nil {
return nil, 0, 0, err
}
fn = func(inputReader io.Reader, _ http.Header, pcfn CheckCopyPreconditionFn, cFns ...func()) (r *GetObjectReader, err error) {
cFns = append(cleanUpFns, cFns...)
if pcfn != nil {
if ok := pcfn(oi, ""); ok {
// Call the cleanup funcs
for i := len(cFns) - 1; i >= 0; i-- {
cFns[i]()
}
return nil, PreConditionFailed{}
}
}
r = &GetObjectReader{
ObjInfo: oi,
pReader: inputReader,
cleanUpFns: cFns,
precondFn: pcfn,
}
return r, nil
}
}
return fn, off, length, nil
}
// Close - calls the cleanup actions in reverse order
func (g *GetObjectReader) Close() error {
// sync.Once is used here to ensure that Close() is
// idempotent.
g.once.Do(func() {
for i := len(g.cleanUpFns) - 1; i >= 0; i-- {
g.cleanUpFns[i]()
}
})
return nil
}
// Read - to implement Reader interface.
func (g *GetObjectReader) Read(p []byte) (n int, err error) {
n, err = g.pReader.Read(p)
if err != nil {
// Calling code may not Close() in case of error, so
// we ensure it.
g.Close()
}
return
}
//SealMD5CurrFn seals md5sum with object encryption key and returns sealed
// md5sum
type SealMD5CurrFn func([]byte) []byte
// PutObjReader is a type that wraps sio.EncryptReader and
// underlying hash.Reader in a struct
type PutObjReader struct {
*hash.Reader // actual data stream
rawReader *hash.Reader // original data stream
sealMD5Fn SealMD5CurrFn
}
// Size returns the absolute number of bytes the Reader
// will return during reading. It returns -1 for unlimited
// data.
func (p *PutObjReader) Size() int64 {
return p.Reader.Size()
}
// MD5CurrentHexString returns the current MD5Sum or encrypted MD5Sum
// as a hex encoded string
func (p *PutObjReader) MD5CurrentHexString() string {
md5sumCurr := p.rawReader.MD5Current()
var appendHyphen bool
// md5sumcurr is not empty in two scenarios
// - server is running in strict compatibility mode
// - client set Content-Md5 during PUT operation
if len(md5sumCurr) == 0 {
// md5sumCurr is only empty when we are running
// in non-compatibility mode.
md5sumCurr = make([]byte, 16)
rand.Read(md5sumCurr)
appendHyphen = true
}
if p.sealMD5Fn != nil {
md5sumCurr = p.sealMD5Fn(md5sumCurr)
}
if appendHyphen {
// Make sure to return etag string upto 32 length, for SSE
// requests ETag might be longer and the code decrypting the
// ETag ignores ETag in multipart ETag form i.e <hex>-N
return hex.EncodeToString(md5sumCurr)[:32] + "-1"
}
return hex.EncodeToString(md5sumCurr)
}
// NewPutObjReader returns a new PutObjReader and holds
// reference to underlying data stream from client and the encrypted
// data reader
func NewPutObjReader(rawReader *hash.Reader, encReader *hash.Reader, encKey []byte) *PutObjReader {
p := PutObjReader{Reader: rawReader, rawReader: rawReader}
if len(encKey) != 0 && encReader != nil {
var objKey crypto.ObjectKey
copy(objKey[:], encKey)
p.sealMD5Fn = sealETagFn(objKey)
p.Reader = encReader
}
return &p
}
func sealETag(encKey crypto.ObjectKey, md5CurrSum []byte) []byte {
var emptyKey [32]byte
if bytes.Equal(encKey[:], emptyKey[:]) {
return md5CurrSum
}
return encKey.SealETag(md5CurrSum)
}
func sealETagFn(key crypto.ObjectKey) SealMD5CurrFn {
fn := func(md5sumcurr []byte) []byte {
return sealETag(key, md5sumcurr)
}
return fn
}
// CleanMinioInternalMetadataKeys removes X-Amz-Meta- prefix from minio internal
// encryption metadata that was sent by minio gateway
func CleanMinioInternalMetadataKeys(metadata map[string]string) map[string]string {
var newMeta = make(map[string]string, len(metadata))
for k, v := range metadata {
if strings.HasPrefix(k, "X-Amz-Meta-X-Minio-Internal-") {
newMeta[strings.TrimPrefix(k, "X-Amz-Meta-")] = v
} else {
newMeta[k] = v
}
}
return newMeta
}
// snappyCompressReader compresses data as it reads
// from the underlying io.Reader.
type snappyCompressReader struct {
r io.Reader
w *snappy.Writer
closed bool
buf bytes.Buffer
}
func newSnappyCompressReader(r io.Reader) *snappyCompressReader {
cr := &snappyCompressReader{r: r}
cr.w = snappy.NewBufferedWriter(&cr.buf)
return cr
}
func (cr *snappyCompressReader) Read(p []byte) (int, error) {
if cr.closed {
// if snappy writer is closed r has been completely read,
// return any remaining data in buf.
return cr.buf.Read(p)
}
// read from original using p as buffer
nr, readErr := cr.r.Read(p)
// write read bytes to snappy writer
nw, err := cr.w.Write(p[:nr])
if err != nil {
return 0, err
}
if nw != nr {
return 0, io.ErrShortWrite
}
// if last of data from reader, close snappy writer to flush
if readErr == io.EOF {
err := cr.w.Close()
cr.closed = true
if err != nil {
return 0, err
}
}
// read compressed bytes out of buf
n, err := cr.buf.Read(p)
if readErr != io.EOF && (err == nil || err == io.EOF) {
err = readErr
}
return n, err
}
// Returns error if the cancelCh has been closed (indicating that S3 client has disconnected)
type detectDisconnect struct {
io.ReadCloser
cancelCh <-chan struct{}
}
func (d *detectDisconnect) Read(p []byte) (int, error) {
select {
case <-d.cancelCh:
return 0, io.ErrUnexpectedEOF
default:
return d.ReadCloser.Read(p)
}
}