ProcessExtraField() private méthode

At current cursor position in the stream, read the extra field, and set the properties on the ZipEntry instance appropriately. This can be called when processing the Extra field in the Central Directory, or in the local header.
private ProcessExtraField ( Stream s, Int16 extraFieldLength ) : int
s Stream
extraFieldLength System.Int16
Résultat int
        /// <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 = Crisis.Ionic.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
                Crisis.Ionic.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      = Crisis.Ionic.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 = Crisis.Ionic.Zip.SharedUtilities.Utf8StringFromBuffer(block);
            }
            else
            {
                zde._FileNameInArchive = Crisis.Ionic.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 = Crisis.Ionic.Zip.SharedUtilities.Utf8StringFromBuffer(block);
                }
                else
                {
                    zde._Comment = Crisis.Ionic.Zip.SharedUtilities.StringFromBuffer(block, expectedEncoding);
                }
            }
            //zde._LengthOfDirEntry = bytesRead;
            return(zde);
        }
        /// <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 = Crisis.Ionic.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
                Crisis.Ionic.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 = Crisis.Ionic.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 = Crisis.Ionic.Zip.SharedUtilities.Utf8StringFromBuffer(block);
            }
            else
            {
                zde._FileNameInArchive = Crisis.Ionic.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 = Crisis.Ionic.Zip.SharedUtilities.Utf8StringFromBuffer(block);
                }
                else
                {
                    zde._Comment = Crisis.Ionic.Zip.SharedUtilities.StringFromBuffer(block, expectedEncoding);
                }
            }
            //zde._LengthOfDirEntry = bytesRead;
            return zde;
        }
Exemple #3
0
        private static bool ReadHeader(ZipEntry ze, System.Text.Encoding defaultEncoding)
        {
            int bytesRead = 0;

            // change for workitem 8098
            ze._RelativeOffsetOfLocalHeader = ze.ArchiveStream.Position;

            int signature = Crisis.Ionic.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
                Crisis.Ionic.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 = Crisis.Ionic.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 = Crisis.Ionic.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
                        Crisis.Ionic.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
                Crisis.Ionic.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);
        }
        private static bool ReadHeader(ZipEntry ze, System.Text.Encoding defaultEncoding)
        {
            int bytesRead = 0;

            // change for workitem 8098
            ze._RelativeOffsetOfLocalHeader = ze.ArchiveStream.Position;

            int signature = Crisis.Ionic.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
                Crisis.Ionic.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 = Crisis.Ionic.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 = Crisis.Ionic.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
                        Crisis.Ionic.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
                Crisis.Ionic.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;
        }