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

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

            int signature = SharedUtilities.ReadSignature(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
                if (ZipEntry.IsNotValidZipDirEntrySig(signature) && (signature != ZipConstants.EndOfCentralDirectorySignature))
                {
                    throw new BadReadException(String.Format("  ZipEntry::ReadHeader(): 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     = (short)(block[i++] + block[i++] * 256);
            ze._BitField          = (short)(block[i++] + block[i++] * 256);
            ze._CompressionMethod = (short)(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;

            // 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.
            ze._actualEncoding = ((ze._BitField & 0x0800) == 0x0800)
                ? System.Text.Encoding.UTF8
                : defaultEncoding;

            // need to use this form of GetString() for .NET CF
            ze._FileNameInArchive = ze._actualEncoding.GetString(block, 0, block.Length);

            // when creating an entry by reading, the LocalFileName is the same as the FileNameInArchive
            ze._LocalFileName = ze._FileNameInArchive;

            // workitem 6898
            if (ze._LocalFileName.EndsWith("/"))
            {
                ze.MarkAsDirectory();
            }

            bytesRead += ze.ProcessExtraField(extraFieldLength);

            ze._LengthOfTrailer = 0;

            // workitem 6607 - don't read for directories
            // actually get the compressed size and CRC if necessary
            if (!ze._LocalFileName.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.

                    ze._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);

                        // 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);
            }

            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)
                {
                    // read in the WinZip AES metadata: salt + PV. 18 bytes for AES256. 10 bytes for AES128.
                    ze._aesCrypto = WinZipAesCrypto.ReadFromStream(null, ze._KeyStrengthInBits, ze.ArchiveStream);
                    bytesRead    += ze._aesCrypto.SizeOfEncryptionMetadata - 10; // MAC (follows crypto bytes)
                    // according to WinZip, the CompressedSize includes the AES Crypto framing data.
                    ze._CompressedFileDataSize -= ze._aesCrypto.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);
        }
Example #2
0
        /// <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>
        /// <returns>the entry read from the archive.</returns>
        internal static ZipEntry ReadDirEntry(ZipFile zf)
        {
            System.IO.Stream     s = zf.ReadStream;
            System.Text.Encoding expectedEncoding = zf.ProvisionalAlternateEncoding;

            int signature = SharedUtilities.ReadSignature(s);

            // return null if this is not a local file header signature
            if (IsNotValidZipDirEntrySig(signature))
            {
                s.Seek(-4, System.IO.SeekOrigin.Current);

                // 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("  ZipEntry::ReadDirEntry(): 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._Source        = ZipEntrySource.ZipFile;
            zde._archiveStream = s;
            zde._zipfile       = zf;
            //zde._cdrPosition = cdrPosition;

            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 = (short)(block[i++] + block[i++] * 256);
                zde._TimeBlob          = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;
                zde._LastModified      = 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);
            }


            zde._filenameLength   = (short)(block[i++] + block[i++] * 256);
            zde._extraFieldLength = (short)(block[i++] + block[i++] * 256);
            zde._commentLength    = (short)(block[i++] + block[i++] * 256);
            //Int16 diskNumber = (short)(block[i++] + block[i++] * 256);
            i += 2;

            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._LocalFileName = SharedUtilities.Utf8StringFromBuffer(block);
            }
            else
            {
                zde._LocalFileName = SharedUtilities.StringFromBuffer(block, expectedEncoding);
            }


            // Console.WriteLine("\nEntry : {0}", zde._LocalFileName);
            // Console.WriteLine("  V Madeby/Needed:      0x{0:X4} / 0x{1:X4}", zde._VersionMadeBy, zde._VersionNeeded);
            // Console.WriteLine("  BitField/Compression: 0x{0:X4} / 0x{1:X4}", zde._BitField, zde._CompressionMethod);
            // Console.WriteLine("  Lastmod:              {0}", zde._LastModified.ToString("u"));
            // Console.WriteLine("  CRC:                  0x{0:X8}", zde._Crc32);
            // Console.WriteLine("  Comp / Uncomp:        0x{0:X8} ({0})   0x{1:X8} ({1})", zde._CompressedSize, zde._UncompressedSize);

            zde._FileNameInArchive = zde._LocalFileName;

            if (zde.AttributesIndicateDirectory)
            {
                zde.MarkAsDirectory();                                   // may append a slash to filename if nec.
            }
            // workitem 6898
            if (zde._LocalFileName.EndsWith("/"))
            {
                zde.MarkAsDirectory();
            }


            zde._CompressedFileDataSize = zde._CompressedSize;
            if ((zde._BitField & 0x01) == 0x01)
            {
                zde._Encryption        = EncryptionAlgorithm.PkzipWeak; // this may change after processing the Extra field
                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(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 -
                                              (zde.LengthOfCryptoHeaderBytes + 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;
                }
            }

            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 = SharedUtilities.Utf8StringFromBuffer(block);
                }
                else
                {
                    zde._Comment = SharedUtilities.StringFromBuffer(block, expectedEncoding);
                }
            }
            //zde._LengthOfDirEntry = bytesRead;
            return(zde);
        }