// For AES the method in the entry is 99, and the real compression method is in the extradata
//
private void ProcessAESExtraData(ZipExtraData extraData)
{
#if !NET_1_1 && !NETCF_2_0
if (extraData.Find(0x9901))
{
// Set version and flag for Zipfile.CreateAndInitDecryptionStream
versionToExtract = ZipConstants.VERSION_AES; // Ver 5.1 = AES see "Version" getter
// Set StrongEncryption flag for ZipFile.CreateAndInitDecryptionStream
Flags = Flags | (int)GeneralBitFlags.StrongEncryption;
//
// Unpack AES extra data field see http://www.winzip.com/aes_info.htm
int length = extraData.ValueLength; // Data size currently 7
if (length < 7)
{
throw new ZipException("AES Extra Data Length " + length + " invalid.");
}
int ver = extraData.ReadShort(); // Version number (1=AE-1 2=AE-2)
int vendorId = extraData.ReadShort(); // 2-character vendor ID 0x4541 = "AE"
int encrStrength = extraData.ReadByte(); // encryption strength 1 = 128 2 = 192 3 = 256
int actualCompress = extraData.ReadShort(); // The actual compression method used to compress the file
_aesVer = ver;
_aesEncryptionStrength = encrStrength;
method = (CompressionMethod)actualCompress;
}
else
{
throw new ZipException("AES Extra Data missing");
}
#else
throw new ZipException("AES unsupported");
#endif
}
/// <summary>
/// Process extra data fields updating the entry based on the contents.
/// </summary>
/// <param name="localHeader">True if the extra data fields should be handled
/// for a local header, rather than for a central header.
/// </param>
internal void ProcessExtraData(bool localHeader)
{
ZipExtraData extraData = new ZipExtraData(this.extra);
if (extraData.Find(0x0001))
{
// Version required to extract is ignored here as some archivers dont set it correctly
// in theory it should be version 45 or higher
// The recorded size will change but remember that this is zip64.
forceZip64_ = true;
if (extraData.ValueLength < 4)
{
throw new ZipException("Extra data extended Zip64 information length is invalid");
}
if (localHeader || (size == uint.MaxValue))
{
size = (ulong)extraData.ReadLong();
}
if (localHeader || (compressedSize == uint.MaxValue))
{
compressedSize = (ulong)extraData.ReadLong();
}
if (!localHeader && (offset == uint.MaxValue))
{
offset = extraData.ReadLong();
}
// Disk number on which file starts is ignored
}
else
{
if (
((versionToExtract & 0xff) >= ZipConstants.VersionZip64) &&
((size == uint.MaxValue) || (compressedSize == uint.MaxValue))
)
{
throw new ZipException("Zip64 Extended information required but is missing.");
}
}
if (extraData.Find(10))
{
// No room for any tags.
if (extraData.ValueLength < 4)
{
throw new ZipException("NTFS Extra data invalid");
}
extraData.ReadInt(); // Reserved
while (extraData.UnreadCount >= 4)
{
int ntfsTag = extraData.ReadShort();
int ntfsLength = extraData.ReadShort();
if (ntfsTag == 1)
{
if (ntfsLength >= 24)
{
long lastModification = extraData.ReadLong();
long lastAccess = extraData.ReadLong();
long createTime = extraData.ReadLong();
DateTime = System.DateTime.FromFileTime(lastModification);
}
break;
}
else
{
// An unknown NTFS tag so simply skip it.
extraData.Skip(ntfsLength);
}
}
}
else if (extraData.Find(0x5455))
{
int length = extraData.ValueLength;
int flags = extraData.ReadByte();
// Can include other times but these are ignored. Length of data should
// actually be 1 + 4 * no of bits in flags.
if (((flags & 1) != 0) && (length >= 5))
{
int iTime = extraData.ReadInt();
DateTime = (new System.DateTime(1970, 1, 1, 0, 0, 0).ToUniversalTime() +
new TimeSpan(0, 0, 0, iTime, 0)).ToLocalTime();
}
}
if (method == CompressionMethod.WinZipAES)
{
ProcessAESExtraData(extraData);
}
}