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); }
/// <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); }