// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package zip
import (
"bufio"
"encoding/binary"
"errors"
"fmt"
"hash"
"hash/crc32"
"io"
"os"
)
var (
ErrFormat = errors.New("zip: not a valid zip file")
ErrAlgorithm = errors.New("zip: unsupported compression algorithm")
ErrChecksum = errors.New("zip: checksum error")
)
type Reader struct {
r io.ReaderAt
File []*File
Comment string
decompressors map[uint16]Decompressor
}
type ReadCloser struct {
f *os.File
Reader
}
type File struct {
FileHeader
zip *Reader
zipr io.ReaderAt
zipsize int64
headerOffset int64
}
func (f *File) hasDataDescriptor() bool {
return f.Flags&0x8 != 0
}
// OpenReader will open the Zip file specified by name and return a ReadCloser.
func OpenReader(name string) (*ReadCloser, error) {
f, err := os.Open(name)
if err != nil {
return nil, err
}
fi, err := f.Stat()
if err != nil {
f.Close()
return nil, err
}
r := new(ReadCloser)
if err := r.init(f, fi.Size()); err != nil {
f.Close()
return nil, err
}
r.f = f
return r, nil
}
// NewReader returns a new Reader reading from r, which is assumed to
// have the given size in bytes.
func NewReader(r io.ReaderAt, size int64) (*Reader, error) {
zr := new(Reader)
if err := zr.init(r, size); err != nil {
return nil, err
}
return zr, nil
}
func (z *Reader) init(r io.ReaderAt, size int64) error {
end, err := readDirectoryEnd(r, size)
if err != nil {
return err
}
if end.directoryRecords > uint64(size)/fileHeaderLen {
return fmt.Errorf("archive/zip: TOC declares impossible %d files in %d byte zip", end.directoryRecords, size)
}
z.r = r
z.File = make([]*File, 0, end.directoryRecords)
z.Comment = end.comment
rs := io.NewSectionReader(r, 0, size)
if _, err = rs.Seek(int64(end.directoryOffset), io.SeekStart); err != nil {
return err
}
buf := bufio.NewReader(rs)
// The count of files inside a zip is truncated to fit in a uint16.
// Gloss over this by reading headers until we encounter
// a bad one, and then only report a ErrFormat or UnexpectedEOF if
// the file count modulo 65536 is incorrect.
for {
f := &File{zip: z, zipr: r, zipsize: size}
err = readDirectoryHeader(f, buf)
if err == ErrFormat || err == io.ErrUnexpectedEOF {
break
}
if err != nil {
return err
}
z.File = append(z.File, f)
}
if uint16(len(z.File)) != uint16(end.directoryRecords) { // only compare 16 bits here
// Return the readDirectoryHeader error if we read
// the wrong number of directory entries.
return err
}
return nil
}
// RegisterDecompressor registers or overrides a custom decompressor for a
// specific method ID. If a decompressor for a given method is not found,
// Reader will default to looking up the decompressor at the package level.
func (z *Reader) RegisterDecompressor(method uint16, dcomp Decompressor) {
if z.decompressors == nil {
z.decompressors = make(map[uint16]Decompressor)
}
z.decompressors[method] = dcomp
}
func (z *Reader) decompressor(method uint16) Decompressor {
dcomp := z.decompressors[method]
if dcomp == nil {
dcomp = decompressor(method)
}
return dcomp
}
// Close closes the Zip file, rendering it unusable for I/O.
func (rc *ReadCloser) Close() error {
return rc.f.Close()
}
// DataOffset returns the offset of the file's possibly-compressed
// data, relative to the beginning of the zip file.
//
// Most callers should instead use Open, which transparently
// decompresses data and verifies checksums.
func (f *File) DataOffset() (offset int64, err error) {
bodyOffset, err := f.findBodyOffset()
if err != nil {
return
}
return f.headerOffset + bodyOffset, nil
}
// Open returns a ReadCloser that provides access to the File's contents.
// Multiple files may be read concurrently.
func (f *File) Open() (io.ReadCloser, error) {
bodyOffset, err := f.findBodyOffset()
if err != nil {
return nil, err
}
size := int64(f.CompressedSize64)
r := io.NewSectionReader(f.zipr, f.headerOffset+bodyOffset, size)
dcomp := f.zip.decompressor(f.Method)
if dcomp == nil {
return nil, ErrAlgorithm
}
var rc io.ReadCloser = dcomp(r)
var desr io.Reader
if f.hasDataDescriptor() {
desr = io.NewSectionReader(f.zipr, f.headerOffset+bodyOffset+size, dataDescriptorLen)
}
rc = &checksumReader{
rc: rc,
hash: crc32.NewIEEE(),
f: f,
desr: desr,
}
return rc, nil
}
type checksumReader struct {
rc io.ReadCloser
hash hash.Hash32
nread uint64 // number of bytes read so far
f *File
desr io.Reader // if non-nil, where to read the data descriptor
err error // sticky error
}
func (r *checksumReader) Read(b []byte) (n int, err error) {
if r.err != nil {
return 0, r.err
}
n, err = r.rc.Read(b)
r.hash.Write(b[:n])
r.nread += uint64(n)
if err == nil {
return
}
if err == io.EOF {
if r.nread != r.f.UncompressedSize64 {
return 0, io.ErrUnexpectedEOF
}
if r.desr != nil {
if err1 := readDataDescriptor(r.desr, r.f); err1 != nil {
if err1 == io.EOF {
err = io.ErrUnexpectedEOF
} else {
err = err1
}
} else if r.hash.Sum32() != r.f.CRC32 {
err = ErrChecksum
}
} else {
// If there's not a data descriptor, we still compare
// the CRC32 of what we've read against the file header
// or TOC's CRC32, if it seems like it was set.
if r.f.CRC32 != 0 && r.hash.Sum32() != r.f.CRC32 {
err = ErrChecksum
}
}
}
r.err = err
return
}
func (r *checksumReader) Close() error { return r.rc.Close() }
// findBodyOffset does the minimum work to verify the file has a header
// and returns the file body offset.
func (f *File) findBodyOffset() (int64, error) {
var buf [fileHeaderLen]byte
if _, err := f.zipr.ReadAt(buf[:], f.headerOffset); err != nil {
return 0, err
}
b := readBuf(buf[:])
if sig := b.uint32(); sig != fileHeaderSignature {
return 0, ErrFormat
}
b = b[22:] // skip over most of the header
filenameLen := int(b.uint16())
extraLen := int(b.uint16())
return int64(fileHeaderLen + filenameLen + extraLen), nil
}
// readDirectoryHeader attempts to read a directory header from r.
// It returns io.ErrUnexpectedEOF if it cannot read a complete header,
// and ErrFormat if it doesn't find a valid header signature.
func readDirectoryHeader(f *File, r io.Reader) error {
var buf [directoryHeaderLen]byte
if _, err := io.ReadFull(r, buf[:]); err != nil {
return err
}
b := readBuf(buf[:])
if sig := b.uint32(); sig != directoryHeaderSignature {
return ErrFormat
}
f.CreatorVersion = b.uint16()
f.ReaderVersion = b.uint16()
f.Flags = b.uint16()
f.Method = b.uint16()
f.ModifiedTime = b.uint16()
f.ModifiedDate = b.uint16()
f.CRC32 = b.uint32()
f.CompressedSize = b.uint32()
f.UncompressedSize = b.uint32()
f.CompressedSize64 = uint64(f.CompressedSize)
f.UncompressedSize64 = uint64(f.UncompressedSize)
filenameLen := int(b.uint16())
extraLen := int(b.uint16())
commentLen := int(b.uint16())
b = b[4:] // skipped start disk number and internal attributes (2x uint16)
f.ExternalAttrs = b.uint32()
f.headerOffset = int64(b.uint32())
d := make([]byte, filenameLen+extraLen+commentLen)
if _, err := io.ReadFull(r, d); err != nil {
return err
}
f.Name = string(d[:filenameLen])
f.Extra = d[filenameLen : filenameLen+extraLen]
f.Comment = string(d[filenameLen+extraLen:])
needUSize := f.UncompressedSize == ^uint32(0)
needCSize := f.CompressedSize == ^uint32(0)
needHeaderOffset := f.headerOffset == int64(^uint32(0))
if len(f.Extra) > 0 {
// Best effort to find what we need.
// Other zip authors might not even follow the basic format,
// and we'll just ignore the Extra content in that case.
b := readBuf(f.Extra)
for len(b) >= 4 { // need at least tag and size
tag := b.uint16()
size := b.uint16()
if int(size) > len(b) {
break
}
if tag == zip64ExtraId {
// update directory values from the zip64 extra block.
// They should only be consulted if the sizes read earlier
// are maxed out.
// See golang.org/issue/13367.
eb := readBuf(b[:size])
if needUSize {
needUSize = false
if len(eb) < 8 {
return ErrFormat
}
f.UncompressedSize64 = eb.uint64()
}
if needCSize {
needCSize = false
if len(eb) < 8 {
return ErrFormat
}
f.CompressedSize64 = eb.uint64()
}
if needHeaderOffset {
needHeaderOffset = false
if len(eb) < 8 {
return ErrFormat
}
f.headerOffset = int64(eb.uint64())
}
break
}
b = b[size:]
}
}
// Assume that uncompressed size 2³²-1 could plausibly happen in
// an old zip32 file that was sharding inputs into the largest chunks
// possible (or is just malicious; search the web for 42.zip).
// If needUSize is true still, it means we didn't see a zip64 extension.
// As long as the compressed size is not also 2³²-1 (implausible)
// and the header is not also 2³²-1 (equally implausible),
// accept the uncompressed size 2³²-1 as valid.
// If nothing else, this keeps archive/zip working with 42.zip.
_ = needUSize
if needCSize || needHeaderOffset {
return ErrFormat
}
return nil
}
func readDataDescriptor(r io.Reader, f *File) error {
var buf [dataDescriptorLen]byte
// The spec says: "Although not originally assigned a
// signature, the value 0x08074b50 has commonly been adopted
// as a signature value for the data descriptor record.
// Implementers should be aware that ZIP files may be
// encountered with or without this signature marking data
// descriptors and should account for either case when reading
// ZIP files to ensure compatibility."
//
// dataDescriptorLen includes the size of the signature but
// first read just those 4 bytes to see if it exists.
if _, err := io.ReadFull(r, buf[:4]); err != nil {
return err
}
off := 0
maybeSig := readBuf(buf[:4])
if maybeSig.uint32() != dataDescriptorSignature {
// No data descriptor signature. Keep these four
// bytes.
off += 4
}
if _, err := io.ReadFull(r, buf[off:12]); err != nil {
return err
}
b := readBuf(buf[:12])
if b.uint32() != f.CRC32 {
return ErrChecksum
}
// The two sizes that follow here can be either 32 bits or 64 bits
// but the spec is not very clear on this and different
// interpretations has been made causing incompatibilities. We
// already have the sizes from the central directory so we can
// just ignore these.
return nil
}
func readDirectoryEnd(r io.ReaderAt, size int64) (dir *directoryEnd, err error) {
// look for directoryEndSignature in the last 1k, then in the last 65k
var buf []byte
var directoryEndOffset int64
for i, bLen := range []int64{1024, 65 * 1024} {
if bLen > size {
bLen = size
}
buf = make([]byte, int(bLen))
if _, err := r.ReadAt(buf, size-bLen); err != nil && err != io.EOF {
return nil, err
}
if p := findSignatureInBlock(buf); p >= 0 {
buf = buf[p:]
directoryEndOffset = size - bLen + int64(p)
break
}
if i == 1 || bLen == size {
return nil, ErrFormat
}
}
// read header into struct
b := readBuf(buf[4:]) // skip signature
d := &directoryEnd{
diskNbr: uint32(b.uint16()),
dirDiskNbr: uint32(b.uint16()),
dirRecordsThisDisk: uint64(b.uint16()),
directoryRecords: uint64(b.uint16()),
directorySize: uint64(b.uint32()),
directoryOffset: uint64(b.uint32()),
commentLen: b.uint16(),
}
l := int(d.commentLen)
if l > len(b) {
return nil, errors.New("zip: invalid comment length")
}
d.comment = string(b[:l])
// These values mean that the file can be a zip64 file
if d.directoryRecords == 0xffff || d.directorySize == 0xffff || d.directoryOffset == 0xffffffff {
p, err := findDirectory64End(r, directoryEndOffset)
if err == nil && p >= 0 {
err = readDirectory64End(r, p, d)
}
if err != nil {
return nil, err
}
}
// Make sure directoryOffset points to somewhere in our file.
if o := int64(d.directoryOffset); o < 0 || o >= size {
return nil, ErrFormat
}
return d, nil
}
// findDirectory64End tries to read the zip64 locator just before the
// directory end and returns the offset of the zip64 directory end if
// found.
func findDirectory64End(r io.ReaderAt, directoryEndOffset int64) (int64, error) {
locOffset := directoryEndOffset - directory64LocLen
if locOffset < 0 {
return -1, nil // no need to look for a header outside the file
}
buf := make([]byte, directory64LocLen)
if _, err := r.ReadAt(buf, locOffset); err != nil {
return -1, err
}
b := readBuf(buf)
if sig := b.uint32(); sig != directory64LocSignature {
return -1, nil
}
if b.uint32() != 0 { // number of the disk with the start of the zip64 end of central directory
return -1, nil // the file is not a valid zip64-file
}
p := b.uint64() // relative offset of the zip64 end of central directory record
if b.uint32() != 1 { // total number of disks
return -1, nil // the file is not a valid zip64-file
}
return int64(p), nil
}
// readDirectory64End reads the zip64 directory end and updates the
// directory end with the zip64 directory end values.
func readDirectory64End(r io.ReaderAt, offset int64, d *directoryEnd) (err error) {
buf := make([]byte, directory64EndLen)
if _, err := r.ReadAt(buf, offset); err != nil {
return err
}
b := readBuf(buf)
if sig := b.uint32(); sig != directory64EndSignature {
return ErrFormat
}
b = b[12:] // skip dir size, version and version needed (uint64 + 2x uint16)
d.diskNbr = b.uint32() // number of this disk
d.dirDiskNbr = b.uint32() // number of the disk with the start of the central directory
d.dirRecordsThisDisk = b.uint64() // total number of entries in the central directory on this disk
d.directoryRecords = b.uint64() // total number of entries in the central directory
d.directorySize = b.uint64() // size of the central directory
d.directoryOffset = b.uint64() // offset of start of central directory with respect to the starting disk number
return nil
}
func findSignatureInBlock(b []byte) int {
for i := len(b) - directoryEndLen; i >= 0; i-- {
// defined from directoryEndSignature in struct.go
if b[i] == 'P' && b[i+1] == 'K' && b[i+2] == 0x05 && b[i+3] == 0x06 {
// n is length of comment
n := int(b[i+directoryEndLen-2]) | int(b[i+directoryEndLen-1])<<8
if n+directoryEndLen+i <= len(b) {
return i
}
}
}
return -1
}
type readBuf []byte
func (b *readBuf) uint16() uint16 {
v := binary.LittleEndian.Uint16(*b)
*b = (*b)[2:]
return v
}
func (b *readBuf) uint32() uint32 {
v := binary.LittleEndian.Uint32(*b)
*b = (*b)[4:]
return v
}
func (b *readBuf) uint64() uint64 {
v := binary.LittleEndian.Uint64(*b)
*b = (*b)[8:]
return v
}