108 lines
3.8 KiB
C#
108 lines
3.8 KiB
C#
using System;
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using System.Text;
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using SharpCompress.Common.Zip.Headers;
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using SharpCompress.Compressor.Deflate;
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namespace SharpCompress.Common.Zip
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{
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internal class PkwareTraditionalEncryptionData
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{
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private static readonly CRC32 crc32 = new CRC32();
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private readonly UInt32[] _Keys = {0x12345678, 0x23456789, 0x34567890};
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private PkwareTraditionalEncryptionData(string password)
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{
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Initialize(password);
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}
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private byte MagicByte
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{
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get
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{
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ushort t = (ushort) ((ushort) (_Keys[2] & 0xFFFF) | 2);
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return (byte) ((t*(t ^ 1)) >> 8);
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}
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}
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public static PkwareTraditionalEncryptionData ForRead(string password, ZipFileEntry header,
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byte[] encryptionHeader)
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{
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var encryptor = new PkwareTraditionalEncryptionData(password);
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byte[] plainTextHeader = encryptor.Decrypt(encryptionHeader, encryptionHeader.Length);
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if (plainTextHeader[11] != (byte) ((header.Crc >> 24) & 0xff))
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{
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if (!FlagUtility.HasFlag(header.Flags, HeaderFlags.UsePostDataDescriptor))
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{
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throw new CryptographicException("The password did not match.");
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}
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if (plainTextHeader[11] != (byte) ((header.LastModifiedTime >> 8) & 0xff))
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{
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throw new CryptographicException("The password did not match.");
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}
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}
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return encryptor;
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}
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public byte[] Decrypt(byte[] cipherText, int length)
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{
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if (length > cipherText.Length)
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throw new ArgumentOutOfRangeException("length",
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"Bad length during Decryption: the length parameter must be smaller than or equal to the size of the destination array.");
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var plainText = new byte[length];
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for (int i = 0; i < length; i++)
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{
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var C = (byte) (cipherText[i] ^ MagicByte);
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UpdateKeys(C);
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plainText[i] = C;
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}
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return plainText;
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}
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public byte[] Encrypt(byte[] plainText, int length)
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{
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if (plainText == null)
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throw new ArgumentNullException("plaintext");
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if (length > plainText.Length)
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throw new ArgumentOutOfRangeException("length",
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"Bad length during Encryption: The length parameter must be smaller than or equal to the size of the destination array.");
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var cipherText = new byte[length];
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for (int i = 0; i < length; i++)
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{
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byte C = plainText[i];
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cipherText[i] = (byte) (plainText[i] ^ MagicByte);
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UpdateKeys(C);
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}
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return cipherText;
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}
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private void Initialize(string password)
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{
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byte[] p = StringToByteArray(password);
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for (int i = 0; i < password.Length; i++)
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UpdateKeys(p[i]);
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}
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internal static byte[] StringToByteArray(string value, Encoding encoding)
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{
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byte[] a = encoding.GetBytes(value);
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return a;
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}
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internal static byte[] StringToByteArray(string value)
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{
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return StringToByteArray(value, ArchiveEncoding.Password);
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}
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private void UpdateKeys(byte byteValue)
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{
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_Keys[0] = (UInt32) crc32.ComputeCrc32((int) _Keys[0], byteValue);
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_Keys[1] = _Keys[1] + (byte) _Keys[0];
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_Keys[1] = _Keys[1]*0x08088405 + 1;
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_Keys[2] = (UInt32) crc32.ComputeCrc32((int) _Keys[2], (byte) (_Keys[1] >> 24));
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}
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}
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} |