/// <summary>
/// Reads one entry from the zip directory structure in the zip file.
/// </summary>
///
/// <param name="zf">
/// The zipfile for which a directory entry will be read. From this param, the
/// method gets the ReadStream and the expected text encoding
/// (ProvisionalAlternateEncoding) which is used if the entry is not marked
/// UTF-8.
/// </param>
///
/// <param name="previouslySeen">
/// a list of previously seen entry names; used to prevent duplicates.
/// </param>
///
/// <returns>the entry read from the archive.</returns>
internal static ZipEntry ReadDirEntry(ZipFile zf,
Dictionary<String,Object> previouslySeen)
{
System.IO.Stream s = zf.ReadStream;
System.Text.Encoding expectedEncoding = (zf.AlternateEncodingUsage == ZipOption.Always)
? zf.AlternateEncoding
: ZipFile.DefaultEncoding;
int signature = Alienlab.Zip.SharedUtilities.ReadSignature(s);
// return null if this is not a local file header signature
if (IsNotValidZipDirEntrySig(signature))
{
s.Seek(-4, System.IO.SeekOrigin.Current);
// workitem 10178
Alienlab.Zip.SharedUtilities.Workaround_Ladybug318918(s);
// Getting "not a ZipDirEntry signature" here is not always wrong or an
// error. This can happen when walking through a zipfile. After the
// last ZipDirEntry, we expect to read an
// EndOfCentralDirectorySignature. When we get this is how we know
// we've reached the end of the central directory.
if (signature != ZipConstants.EndOfCentralDirectorySignature &&
signature != ZipConstants.Zip64EndOfCentralDirectoryRecordSignature &&
signature != ZipConstants.ZipEntrySignature // workitem 8299
)
{
throw new BadReadException(String.Format(" Bad signature (0x{0:X8}) at position 0x{1:X8}", signature, s.Position));
}
return null;
}
int bytesRead = 42 + 4;
byte[] block = new byte[42];
int n = s.Read(block, 0, block.Length);
if (n != block.Length) return null;
int i = 0;
ZipEntry zde = new ZipEntry();
zde.AlternateEncoding = expectedEncoding;
zde._Source = ZipEntrySource.ZipFile;
zde._container = new ZipContainer(zf);
unchecked
{
zde._VersionMadeBy = (short)(block[i++] + block[i++] * 256);
zde._VersionNeeded = (short)(block[i++] + block[i++] * 256);
zde._BitField = (short)(block[i++] + block[i++] * 256);
zde._CompressionMethod = (Int16)(block[i++] + block[i++] * 256);
zde._TimeBlob = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;
zde._LastModified = Alienlab.Zip.SharedUtilities.PackedToDateTime(zde._TimeBlob);
zde._timestamp |= ZipEntryTimestamp.DOS;
zde._Crc32 = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;
zde._CompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
zde._UncompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
}
// preserve
zde._CompressionMethod_FromZipFile = zde._CompressionMethod;
zde._filenameLength = (short)(block[i++] + block[i++] * 256);
zde._extraFieldLength = (short)(block[i++] + block[i++] * 256);
zde._commentLength = (short)(block[i++] + block[i++] * 256);
zde._diskNumber = (UInt32)(block[i++] + block[i++] * 256);
zde._InternalFileAttrs = (short)(block[i++] + block[i++] * 256);
zde._ExternalFileAttrs = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;
zde._RelativeOffsetOfLocalHeader = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
// workitem 7801
zde.IsText = ((zde._InternalFileAttrs & 0x01) == 0x01);
block = new byte[zde._filenameLength];
n = s.Read(block, 0, block.Length);
bytesRead += n;
if ((zde._BitField & 0x0800) == 0x0800)
{
// UTF-8 is in use
zde._FileNameInArchive = Alienlab.Zip.SharedUtilities.Utf8StringFromBuffer(block);
}
else
{
zde._FileNameInArchive = Alienlab.Zip.SharedUtilities.StringFromBuffer(block, expectedEncoding);
}
// workitem 10330
// insure unique entry names
while (previouslySeen.ContainsKey(zde._FileNameInArchive))
{
zde._FileNameInArchive = CopyHelper.AppendCopyToFileName(zde._FileNameInArchive);
zde._metadataChanged = true;
}
if (zde.AttributesIndicateDirectory)
zde.MarkAsDirectory(); // may append a slash to filename if nec.
// workitem 6898
else if (zde._FileNameInArchive.EndsWith("/")) zde.MarkAsDirectory();
zde._CompressedFileDataSize = zde._CompressedSize;
if ((zde._BitField & 0x01) == 0x01)
{
// this may change after processing the Extra field
zde._Encryption_FromZipFile = zde._Encryption =
EncryptionAlgorithm.PkzipWeak;
zde._sourceIsEncrypted = true;
}
if (zde._extraFieldLength > 0)
{
zde._InputUsesZip64 = (zde._CompressedSize == 0xFFFFFFFF ||
zde._UncompressedSize == 0xFFFFFFFF ||
zde._RelativeOffsetOfLocalHeader == 0xFFFFFFFF);
// Console.WriteLine(" Input uses Z64?: {0}", zde._InputUsesZip64);
bytesRead += zde.ProcessExtraField(s, zde._extraFieldLength);
zde._CompressedFileDataSize = zde._CompressedSize;
}
// we've processed the extra field, so we know the encryption method is set now.
if (zde._Encryption == EncryptionAlgorithm.PkzipWeak)
{
// the "encryption header" of 12 bytes precedes the file data
zde._CompressedFileDataSize -= 12;
}
#if AESCRYPTO
else if (zde.Encryption == EncryptionAlgorithm.WinZipAes128 ||
zde.Encryption == EncryptionAlgorithm.WinZipAes256)
{
zde._CompressedFileDataSize = zde.CompressedSize -
(ZipEntry.GetLengthOfCryptoHeaderBytes(zde.Encryption) + 10);
zde._LengthOfTrailer = 10;
}
#endif
// tally the trailing descriptor
if ((zde._BitField & 0x0008) == 0x0008)
{
// sig, CRC, Comp and Uncomp sizes
if (zde._InputUsesZip64)
zde._LengthOfTrailer += 24;
else
zde._LengthOfTrailer += 16;
}
// workitem 12744
zde.AlternateEncoding = ((zde._BitField & 0x0800) == 0x0800)
? System.Text.Encoding.UTF8
:expectedEncoding;
zde.AlternateEncodingUsage = ZipOption.Always;
if (zde._commentLength > 0)
{
block = new byte[zde._commentLength];
n = s.Read(block, 0, block.Length);
bytesRead += n;
if ((zde._BitField & 0x0800) == 0x0800)
{
// UTF-8 is in use
zde._Comment = Alienlab.Zip.SharedUtilities.Utf8StringFromBuffer(block);
}
else
{
zde._Comment = Alienlab.Zip.SharedUtilities.StringFromBuffer(block, expectedEncoding);
}
}
//zde._LengthOfDirEntry = bytesRead;
return zde;
}
private static bool ReadHeader(ZipEntry ze, System.Text.Encoding defaultEncoding)
{
int bytesRead = 0;
// change for workitem 8098
ze._RelativeOffsetOfLocalHeader = ze.ArchiveStream.Position;
int signature = Alienlab.Zip.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
Alienlab.Zip.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 = Alienlab.Zip.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 = Alienlab.Zip.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
Alienlab.Zip.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
Alienlab.Zip.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;
}