/// <summary>
/// Read the next entry from the zip file.
/// </summary>
///
/// <remarks>
/// <para>
/// Call this method just before calling <see cref="Read(byte[], int, int)"/>,
/// to position the pointer in the zip file to the next entry that can be
/// read. Subsequent calls to <c>Read()</c>, will decrypt and decompress the
/// data in the zip file, until <c>Read()</c> returns 0.
/// </para>
///
/// <para>
/// Each time you call <c>GetNextEntry()</c>, the pointer in the wrapped
/// stream is moved to the next entry in the zip file. If you call <see
/// cref="Seek(long, SeekOrigin)"/>, and thus re-position the pointer within
/// the file, you will need to call <c>GetNextEntry()</c> again, to insure
/// that the file pointer is positioned at the beginning of a zip entry.
/// </para>
///
/// <para>
/// This method returns the <c>ZipEntry</c>. Using a stream approach, you will
/// read the raw bytes for an entry in a zip file via calls to <c>Read()</c>.
/// Alternatively, you can extract an entry into a file, or a stream, by
/// calling <see cref="ZipEntry.Extract()"/>, or one of its siblings.
/// </para>
///
/// </remarks>
///
/// <returns>
/// The <c>ZipEntry</c> read. Returns null (or Nothing in VB) if there are no more
/// entries in the zip file.
/// </returns>
///
public ZipEntry GetNextEntry()
{
if (_findRequired)
{
// find the next signature
long d = SharedUtilities.FindSignature(_inputStream, ZipConstants.ZipEntrySignature);
if (d == -1)
{
return(null);
}
// back up 4 bytes: ReadEntry assumes the file pointer is positioned before the entry signature
_inputStream.Seek(-4, SeekOrigin.Current);
// workitem 10178
SharedUtilities.Workaround_Ladybug318918(_inputStream);
}
// workitem 10923
else if (_firstEntry)
{
// we've already read one entry.
// Seek to the end of it.
_inputStream.Seek(_endOfEntry, SeekOrigin.Begin);
SharedUtilities.Workaround_Ladybug318918(_inputStream);
}
_currentEntry = ZipEntry.ReadEntry(_container, !_firstEntry);
// ReadEntry leaves the file position after all the entry
// data and the optional bit-3 data descriptpr. This is
// where the next entry would normally start.
_endOfEntry = _inputStream.Position;
_firstEntry = true;
_needSetup = true;
_findRequired = false;
return(_currentEntry);
}
private static bool ReadHeader(ZipEntry ze, System.Text.Encoding defaultEncoding)
{
int bytesRead = 0;
// change for workitem 8098
ze._RelativeOffsetOfLocalHeader = ze.ArchiveStream.Position;
int signature = SharedUtilities.ReadEntrySignature(ze.ArchiveStream);
bytesRead += 4;
// Return false if this is not a local file header signature.
if (ZipEntry.IsNotValidSig(signature))
{
// Getting "not a ZipEntry signature" is not always wrong or an error.
// This will happen after the last entry in a zipfile. In that case, we
// expect to read :
// a ZipDirEntry signature (if a non-empty zip file) or
// a ZipConstants.EndOfCentralDirectorySignature.
//
// Anything else is a surprise.
ze.ArchiveStream.Seek(-4, SeekOrigin.Current); // unread the signature
// workitem 10178
SharedUtilities.Workaround_Ladybug318918(ze.ArchiveStream);
if (ZipEntry.IsNotValidZipDirEntrySig(signature) && (signature != ZipConstants.EndOfCentralDirectorySignature))
{
throw new BadReadException(String.Format(" Bad signature (0x{0:X8}) at position 0x{1:X8}", signature, ze.ArchiveStream.Position));
}
return(false);
}
byte[] block = new byte[26];
int n = ze.ArchiveStream.Read(block, 0, block.Length);
if (n != block.Length)
{
return(false);
}
bytesRead += n;
int i = 0;
ze._VersionNeeded = (Int16)(block[i++] + block[i++] * 256);
ze._BitField = (Int16)(block[i++] + block[i++] * 256);
ze._CompressionMethod_FromZipFile = ze._CompressionMethod = (Int16)(block[i++] + block[i++] * 256);
ze._TimeBlob = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;
// transform the time data into something usable (a DateTime)
ze._LastModified = SharedUtilities.PackedToDateTime(ze._TimeBlob);
ze._timestamp |= ZipEntryTimestamp.DOS;
if ((ze._BitField & 0x01) == 0x01)
{
ze._Encryption_FromZipFile = ze._Encryption = EncryptionAlgorithm.PkzipWeak; // this *may* change after processing the Extra field
ze._sourceIsEncrypted = true;
}
// NB: if ((ze._BitField & 0x0008) != 0x0008), then the Compressed, uncompressed and
// CRC values are not true values; the true values will follow the entry data.
// But, regardless of the status of bit 3 in the bitfield, the slots for
// the three amigos may contain marker values for ZIP64. So we must read them.
{
ze._Crc32 = (Int32)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
ze._CompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
ze._UncompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
if ((uint)ze._CompressedSize == 0xFFFFFFFF ||
(uint)ze._UncompressedSize == 0xFFFFFFFF)
{
ze._InputUsesZip64 = true;
}
}
Int16 filenameLength = (short)(block[i++] + block[i++] * 256);
Int16 extraFieldLength = (short)(block[i++] + block[i++] * 256);
block = new byte[filenameLength];
n = ze.ArchiveStream.Read(block, 0, block.Length);
bytesRead += n;
// if the UTF8 bit is set for this entry, override the
// encoding the application requested.
if ((ze._BitField & 0x0800) == 0x0800)
{
// workitem 12744
ze.AlternateEncoding = System.Text.Encoding.UTF8;
ze.AlternateEncodingUsage = ZipOption.Always;
}
// need to use this form of GetString() for .NET CF
ze._FileNameInArchive = ze.AlternateEncoding.GetString(block, 0, block.Length);
// workitem 6898
if (ze._FileNameInArchive.EndsWith("/"))
{
ze.MarkAsDirectory();
}
bytesRead += ze.ProcessExtraField(ze.ArchiveStream, extraFieldLength);
ze._LengthOfTrailer = 0;
// workitem 6607 - don't read for directories
// actually get the compressed size and CRC if necessary
if (!ze._FileNameInArchive.EndsWith("/") && (ze._BitField & 0x0008) == 0x0008)
{
// This descriptor exists only if bit 3 of the general
// purpose bit flag is set (see below). It is byte aligned
// and immediately follows the last byte of compressed data,
// as well as any encryption trailer, as with AES.
// This descriptor is used only when it was not possible to
// seek in the output .ZIP file, e.g., when the output .ZIP file
// was standard output or a non-seekable device. For ZIP64(tm) format
// archives, the compressed and uncompressed sizes are 8 bytes each.
// workitem 8098: ok (restore)
long posn = ze.ArchiveStream.Position;
// Here, we're going to loop until we find a ZipEntryDataDescriptorSignature and
// a consistent data record after that. To be consistent, the data record must
// indicate the length of the entry data.
bool wantMore = true;
long SizeOfDataRead = 0;
int tries = 0;
while (wantMore)
{
tries++;
// We call the FindSignature shared routine to find the specified signature
// in the already-opened zip archive, starting from the current cursor
// position in that filestream. If we cannot find the signature, then the
// routine returns -1, and the ReadHeader() method returns false,
// indicating we cannot read a legal entry header. If we have found it,
// then the FindSignature() method returns the number of bytes in the
// stream we had to seek forward, to find the sig. We need this to
// determine if the zip entry is valid, later.
if (ze._container.ZipFile != null)
{
ze._container.ZipFile.OnReadBytes(ze);
}
long d = SharedUtilities.FindSignature(ze.ArchiveStream, ZipConstants.ZipEntryDataDescriptorSignature);
if (d == -1)
{
return(false);
}
// total size of data read (through all loops of this).
SizeOfDataRead += d;
if (ze._InputUsesZip64)
{
// read 1x 4-byte (CRC) and 2x 8-bytes (Compressed Size, Uncompressed Size)
block = new byte[20];
n = ze.ArchiveStream.Read(block, 0, block.Length);
if (n != 20)
{
return(false);
}
// do not increment bytesRead - it is for entry header only.
// the data we have just read is a footer (falls after the file data)
//bytesRead += n;
i = 0;
ze._Crc32 = (Int32)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
ze._CompressedSize = BitConverter.ToInt64(block, i);
i += 8;
ze._UncompressedSize = BitConverter.ToInt64(block, i);
i += 8;
ze._LengthOfTrailer += 24; // bytes including sig, CRC, Comp and Uncomp sizes
}
else
{
// read 3x 4-byte fields (CRC, Compressed Size, Uncompressed Size)
block = new byte[12];
n = ze.ArchiveStream.Read(block, 0, block.Length);
if (n != 12)
{
return(false);
}
// do not increment bytesRead - it is for entry header only.
// the data we have just read is a footer (falls after the file data)
//bytesRead += n;
i = 0;
ze._Crc32 = (Int32)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
ze._CompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
ze._UncompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
ze._LengthOfTrailer += 16; // bytes including sig, CRC, Comp and Uncomp sizes
}
wantMore = (SizeOfDataRead != ze._CompressedSize);
if (wantMore)
{
// Seek back to un-read the last 12 bytes - maybe THEY contain
// the ZipEntryDataDescriptorSignature.
// (12 bytes for the CRC, Comp and Uncomp size.)
ze.ArchiveStream.Seek(-12, SeekOrigin.Current);
// workitem 10178
SharedUtilities.Workaround_Ladybug318918(ze.ArchiveStream);
// Adjust the size to account for the false signature read in
// FindSignature().
SizeOfDataRead += 4;
}
}
// seek back to previous position, to prepare to read file data
// workitem 8098: ok (restore)
ze.ArchiveStream.Seek(posn, SeekOrigin.Begin);
// workitem 10178
SharedUtilities.Workaround_Ladybug318918(ze.ArchiveStream);
}
ze._CompressedFileDataSize = ze._CompressedSize;
// bit 0 set indicates that some kind of encryption is in use
if ((ze._BitField & 0x01) == 0x01)
{
#if AESCRYPTO
if (ze.Encryption == EncryptionAlgorithm.WinZipAes128 ||
ze.Encryption == EncryptionAlgorithm.WinZipAes256)
{
int bits = ZipEntry.GetKeyStrengthInBits(ze._Encryption_FromZipFile);
// read in the WinZip AES metadata: salt + PV. 18 bytes for AES256. 10 bytes for AES128.
ze._aesCrypto_forExtract = WinZipAesCrypto.ReadFromStream(null, bits, ze.ArchiveStream);
bytesRead += ze._aesCrypto_forExtract.SizeOfEncryptionMetadata - 10; // MAC (follows crypto bytes)
// according to WinZip, the CompressedSize includes the AES Crypto framing data.
ze._CompressedFileDataSize -= ze._aesCrypto_forExtract.SizeOfEncryptionMetadata;
ze._LengthOfTrailer += 10; // MAC
}
else
#endif
{
// read in the header data for "weak" encryption
ze._WeakEncryptionHeader = new byte[12];
bytesRead += ZipEntry.ReadWeakEncryptionHeader(ze._archiveStream, ze._WeakEncryptionHeader);
// decrease the filedata size by 12 bytes
ze._CompressedFileDataSize -= 12;
}
}
// Remember the size of the blob for this entry.
// We also have the starting position in the stream for this entry.
ze._LengthOfHeader = bytesRead;
ze._TotalEntrySize = ze._LengthOfHeader + ze._CompressedFileDataSize + ze._LengthOfTrailer;
// We've read in the regular entry header, the extra field, and any
// encryption header. The pointer in the file is now at the start of the
// filedata, which is potentially compressed and encrypted. Just ahead in
// the file, there are _CompressedFileDataSize bytes of data, followed by
// potentially a non-zero length trailer, consisting of optionally, some
// encryption stuff (10 byte MAC for AES), and the bit-3 trailer (16 or 24
// bytes).
return(true);
}
private static void ReadIntoInstance(ZipFile zf)
{
Stream s = zf.ReadStream;
try
{
zf._readName = zf._name; // workitem 13915
if (!s.CanSeek)
{
ReadIntoInstance_Orig(zf);
return;
}
zf.OnReadStarted();
// change for workitem 8098
//zf._originPosition = s.Position;
// Try reading the central directory, rather than scanning the file.
uint datum = ReadFirstFourBytes(s);
if (datum == ZipConstants.EndOfCentralDirectorySignature)
{
return;
}
// start at the end of the file...
// seek backwards a bit, then look for the EoCD signature.
int nTries = 0;
bool success = false;
// The size of the end-of-central-directory-footer plus 2 bytes is 18.
// This implies an archive comment length of 0. We'll add a margin of
// safety and start "in front" of that, when looking for the
// EndOfCentralDirectorySignature
long posn = s.Length - 64;
long maxSeekback = Math.Max(s.Length - 0x4000, 10);
do
{
if (posn < 0)
{
posn = 0; // BOF
}
s.Seek(posn, SeekOrigin.Begin);
long bytesRead = SharedUtilities.FindSignature(s, (int)ZipConstants.EndOfCentralDirectorySignature);
if (bytesRead != -1)
{
success = true;
}
else
{
if (posn == 0)
{
break; // started at the BOF and found nothing
}
nTries++;
// Weird: with NETCF, negative offsets from SeekOrigin.End DO
// NOT WORK. So rather than seek a negative offset, we seek
// from SeekOrigin.Begin using a smaller number.
posn -= (32 * (nTries + 1) * nTries);
}
}while (!success && posn > maxSeekback);
if (success)
{
// workitem 8299
zf._locEndOfCDS = s.Position - 4;
byte[] block = new byte[16];
s.Read(block, 0, block.Length);
zf._diskNumberWithCd = BitConverter.ToUInt16(block, 2);
if (zf._diskNumberWithCd == 0xFFFF)
{
throw new ZipException("Spanned archives with more than 65534 segments are not supported at this time.");
}
zf._diskNumberWithCd++; // I think the number in the file differs from reality by 1
int i = 12;
uint offset32 = (uint)BitConverter.ToUInt32(block, i);
if (offset32 == 0xFFFFFFFF)
{
Zip64SeekToCentralDirectory(zf);
}
else
{
zf._OffsetOfCentralDirectory = offset32;
// change for workitem 8098
s.Seek(offset32, SeekOrigin.Begin);
}
ReadCentralDirectory(zf);
}
else
{
// Could not find the central directory.
// Fallback to the old method.
// workitem 8098: ok
//s.Seek(zf._originPosition, SeekOrigin.Begin);
s.Seek(0L, SeekOrigin.Begin);
ReadIntoInstance_Orig(zf);
}
}
catch (Exception ex1)
{
if (zf._ReadStreamIsOurs && zf._readstream != null)
{
try
{
#if NETCF
zf._readstream.Close();
#else
zf._readstream.Dispose();
#endif
zf._readstream = null;
}
finally { }
}
throw new ZipException("Cannot read that as a ZipFile", ex1);
}
// the instance has been read in
zf._contentsChanged = false;
}
