/* There is a small chance that something very weird could happen here. The code calling into this function
* will ask for a value from the extra field if the field was masked with FF's. It's theoretically possible
* that a field was FF's legitimately, and the writer didn't decide to write the corresponding extra field.
* Also, at the same time, other fields were masked with FF's to indicate looking in the zip64 record.
* Then, the search for the zip64 record will fail because the expected size is wrong,
* and a nulled out Zip64ExtraField will be returned. Thus, even though there was Zip64 data,
* it will not be used. It is questionable whether this situation is possible to detect
*/
/* unlike the other functions that have try-pattern semantics, these functions always return a
* Zip64ExtraField. If a Zip64 extra field actually doesn't exist, all of the fields in the
* returned struct will be null
*
* If there are more than one Zip64 extra fields, we take the first one that has the expected size
*/
public static Zip64ExtraField GetJustZip64Block(Stream extraFieldStream,
Boolean readUncompressedSize, Boolean readCompressedSize,
Boolean readLocalHeaderOffset, Boolean readStartDiskNumber)
{
Zip64ExtraField zip64Field;
using (BinaryReader reader = new BinaryReader(extraFieldStream))
{
ZipGenericExtraField currentExtraField;
while (ZipGenericExtraField.TryReadBlock(reader, extraFieldStream.Length, out currentExtraField))
{
if (TryGetZip64BlockFromGenericExtraField(currentExtraField, readUncompressedSize,
readCompressedSize, readLocalHeaderOffset, readStartDiskNumber, out zip64Field))
{
return(zip64Field);
}
}
}
zip64Field = new Zip64ExtraField();
zip64Field._compressedSize = null;
zip64Field._uncompressedSize = null;
zip64Field._localHeaderOffset = null;
zip64Field._startDiskNumber = null;
return(zip64Field);
}
//shouldn't ever read the byte at position endExtraField
//assumes we are positioned at the beginning of an extra field subfield
public static Boolean TryReadBlock(BinaryReader reader, Int64 endExtraField, out ZipGenericExtraField field)
{
field = new ZipGenericExtraField();
//not enough bytes to read tag + size
if (endExtraField - reader.BaseStream.Position < 4)
{
return(false);
}
field._tag = reader.ReadUInt16();
field._size = reader.ReadUInt16();
//not enough bytes to read the data
if (endExtraField - reader.BaseStream.Position < field._size)
{
return(false);
}
field._data = reader.ReadBytes(field._size);
return(true);
}
static public List <ZipGenericExtraField> GetExtraFields(BinaryReader reader)
{
//assumes that TrySkipBlock has already been called, so we don't have to validate twice
List <ZipGenericExtraField> result;
const Int32 OffsetToFilenameLength = 26; //from the point before the signature
reader.BaseStream.Seek(OffsetToFilenameLength, SeekOrigin.Current);
UInt16 filenameLength = reader.ReadUInt16();
UInt16 extraFieldLength = reader.ReadUInt16();
reader.BaseStream.Seek(filenameLength, SeekOrigin.Current);
using (Stream str = new SubReadStream(reader.BaseStream, reader.BaseStream.Position, extraFieldLength))
{
result = ZipGenericExtraField.ParseExtraField(str);
}
Zip64ExtraField.RemoveZip64Blocks(result);
return(result);
}
//if saveExtraFieldsAndComments is false, FileComment and ExtraFields will be null
//in either case, the zip64 extra field info will be incorporated into other fields
static public Boolean TryReadBlock(BinaryReader reader, Boolean saveExtraFieldsAndComments, out ZipCentralDirectoryFileHeader header)
{
header = new ZipCentralDirectoryFileHeader();
if (reader.ReadUInt32() != SignatureConstant)
{
return(false);
}
header.VersionMadeBy = reader.ReadUInt16();
header.VersionNeededToExtract = reader.ReadUInt16();
header.GeneralPurposeBitFlag = reader.ReadUInt16();
header.CompressionMethod = reader.ReadUInt16();
header.LastModified = reader.ReadUInt32();
header.Crc32 = reader.ReadUInt32();
UInt32 compressedSizeSmall = reader.ReadUInt32();
UInt32 uncompressedSizeSmall = reader.ReadUInt32();
header.FilenameLength = reader.ReadUInt16();
header.ExtraFieldLength = reader.ReadUInt16();
header.FileCommentLength = reader.ReadUInt16();
UInt16 diskNumberStartSmall = reader.ReadUInt16();
header.InternalFileAttributes = reader.ReadUInt16();
header.ExternalFileAttributes = reader.ReadUInt32();
UInt32 relativeOffsetOfLocalHeaderSmall = reader.ReadUInt32();
header.Filename = reader.ReadBytes(header.FilenameLength);
Boolean uncompressedSizeInZip64 = uncompressedSizeSmall == ZipHelper.Mask32Bit;
Boolean compressedSizeInZip64 = compressedSizeSmall == ZipHelper.Mask32Bit;
Boolean relativeOffsetInZip64 = relativeOffsetOfLocalHeaderSmall == ZipHelper.Mask32Bit;
Boolean diskNumberStartInZip64 = diskNumberStartSmall == ZipHelper.Mask16Bit;
Zip64ExtraField zip64;
long endExtraFields = reader.BaseStream.Position + header.ExtraFieldLength;
using (Stream str = new SubReadStream(reader.BaseStream, reader.BaseStream.Position, header.ExtraFieldLength))
{
if (saveExtraFieldsAndComments)
{
header.ExtraFields = ZipGenericExtraField.ParseExtraField(str);
zip64 = Zip64ExtraField.GetAndRemoveZip64Block(header.ExtraFields,
uncompressedSizeInZip64, compressedSizeInZip64,
relativeOffsetInZip64, diskNumberStartInZip64);
}
else
{
header.ExtraFields = null;
zip64 = Zip64ExtraField.GetJustZip64Block(str,
uncompressedSizeInZip64, compressedSizeInZip64,
relativeOffsetInZip64, diskNumberStartInZip64);
}
}
// There are zip files that have malformed ExtraField blocks in which GetJustZip64Block() silently bails out without reading all the way to the end
// of the ExtraField block. Thus we must force the stream's position to the proper place.
reader.BaseStream.AdvanceToPosition(endExtraFields);
if (saveExtraFieldsAndComments)
{
header.FileComment = reader.ReadBytes(header.FileCommentLength);
}
else
{
reader.BaseStream.Position += header.FileCommentLength;
header.FileComment = null;
}
header.UncompressedSize = zip64.UncompressedSize == null
? uncompressedSizeSmall
: zip64.UncompressedSize.Value;
header.CompressedSize = zip64.CompressedSize == null
? compressedSizeSmall
: zip64.CompressedSize.Value;
header.RelativeOffsetOfLocalHeader = zip64.LocalHeaderOffset == null
? relativeOffsetOfLocalHeaderSmall
: zip64.LocalHeaderOffset.Value;
header.DiskNumberStart = zip64.StartDiskNumber == null
? diskNumberStartSmall
: zip64.StartDiskNumber.Value;
return(true);
}
private static Boolean TryGetZip64BlockFromGenericExtraField(ZipGenericExtraField extraField,
Boolean readUncompressedSize, Boolean readCompressedSize,
Boolean readLocalHeaderOffset, Boolean readStartDiskNumber,
out Zip64ExtraField zip64Block)
{
zip64Block = new Zip64ExtraField();
zip64Block._compressedSize = null;
zip64Block._uncompressedSize = null;
zip64Block._localHeaderOffset = null;
zip64Block._startDiskNumber = null;
if (extraField.Tag != TagConstant)
{
return(false);
}
//this pattern needed because nested using blocks trigger CA2202
MemoryStream ms = null;
try
{
ms = new MemoryStream(extraField.Data);
using (BinaryReader reader = new BinaryReader(ms))
{
ms = null;
zip64Block._size = extraField.Size;
UInt16 expectedSize = 0;
if (readUncompressedSize)
{
expectedSize += 8;
}
if (readCompressedSize)
{
expectedSize += 8;
}
if (readLocalHeaderOffset)
{
expectedSize += 8;
}
if (readStartDiskNumber)
{
expectedSize += 4;
}
//if it is not the expected size, perhaps there is another extra field that matches
if (expectedSize != zip64Block._size)
{
return(false);
}
if (readUncompressedSize)
{
zip64Block._uncompressedSize = reader.ReadInt64();
}
if (readCompressedSize)
{
zip64Block._compressedSize = reader.ReadInt64();
}
if (readLocalHeaderOffset)
{
zip64Block._localHeaderOffset = reader.ReadInt64();
}
if (readStartDiskNumber)
{
zip64Block._startDiskNumber = reader.ReadInt32();
}
//original values are unsigned, so implies value is too big to fit in signed integer
if (zip64Block._uncompressedSize < 0)
{
throw new InvalidDataException(SR.FieldTooBigUncompressedSize);
}
if (zip64Block._compressedSize < 0)
{
throw new InvalidDataException(SR.FieldTooBigCompressedSize);
}
if (zip64Block._localHeaderOffset < 0)
{
throw new InvalidDataException(SR.FieldTooBigLocalHeaderOffset);
}
if (zip64Block._startDiskNumber < 0)
{
throw new InvalidDataException(SR.FieldTooBigStartDiskNumber);
}
return(true);
}
}
finally
{
if (ms != null)
{
ms.Dispose();
}
}
}
