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(EncryptedViewStream): moved common functionality to abstract base class.

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This commit is contained in:
morkt 2016-07-30 22:27:13 +04:00
parent eeed66e6c8
commit a48bf2599a
1 changed files with 74 additions and 64 deletions
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138
ArcFormats/NScripter/EncryptedStream.cs
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@ -31,25 +31,20 @@ using GameRes.Utility;
namespace GameRes.Formats.NScripter
{
internal class EncryptedViewStream : Stream
internal abstract class ViewStreamBase : Stream
{
ArcView.Frame m_view;
byte[] m_key;
long m_max_offset;
long m_position = 0;
byte[] m_current_block = new byte[BlockLength];
int m_current_block_length = 0;
long m_current_block_position = 0;
static readonly HashAlgorithm MD5 = System.Security.Cryptography.MD5.Create();
static readonly HashAlgorithm SHA1 = System.Security.Cryptography.SHA1.Create();
private ArcView.Frame m_view;
private long m_max_offset;
private long m_position = 0;
protected byte[] m_current_block = new byte[BlockLength];
protected int m_current_block_length = 0;
protected long m_current_block_position = 0;
public const int BlockLength = 1024;
public EncryptedViewStream (ArcView mmap, byte[] key)
public ViewStreamBase (ArcView mmap)
{
m_view = mmap.CreateFrame();
m_key = key;
m_max_offset = mmap.MaxOffset;
}
@ -61,10 +56,9 @@ namespace GameRes.Formats.NScripter
{
if (refill_buffer)
{
int block_num = (int)(m_position / BlockLength);
m_current_block_position = m_position & ~((long)BlockLength-1);
m_current_block_length = m_view.Read (m_current_block_position, m_current_block, 0, (uint)BlockLength);
DecryptBlock (block_num);
DecryptBlock();
}
int src_offset = (int)m_position & (BlockLength-1);
int available = Math.Min (count, m_current_block_length - src_offset);
@ -78,55 +72,7 @@ namespace GameRes.Formats.NScripter
return total_read;
}
private void DecryptBlock (int block_num)
{
byte[] bn = new byte[8];
LittleEndian.Pack (block_num, bn, 0);
var md5_hash = MD5.ComputeHash (bn);
var sha1_hash = SHA1.ComputeHash (bn);
var hmac_key = new byte[16];
for (int i = 0; i < 16; i++)
hmac_key[i] = (byte)(md5_hash[i] ^ sha1_hash[i]);
byte[] hmac_hash;
using (var HMAC = new HMACSHA512 (hmac_key))
hmac_hash = HMAC.ComputeHash (m_key);
int[] map = Enumerable.Range (0, 256).ToArray();
byte index = 0;
int h = 0;
for (int i = 0; i < 256; i++)
{
if (hmac_hash.Length == h)
h = 0;
int tmp = map[i];
index = (byte)(tmp + hmac_hash[h++] + index);
map[i] = map[index];
map[index] = tmp;
}
int i0 = 0, i1 = 0;
for (int i = 0; i < 300; i++)
{
i0 = (i0 + 1) & 0xFF;
int tmp = map[i0];
i1 = (i1 + tmp) & 0xFF;
map[i0] = map[i1];
map[i1] = tmp;
}
for (int i = 0; i < m_current_block_length; i++)
{
i0 = (i0 + 1) & 0xFF;
int tmp = map[i0];
i1 = (i1 + tmp) & 0xFF;
map[i0] = map[i1];
map[i1] = tmp;
m_current_block[i] ^= (byte)map[(map[i0] + tmp) & 0xFF];
}
}
protected abstract void DecryptBlock ();
#region IO.Stream methods
public override bool CanRead { get { return !m_disposed; } }
@ -180,4 +126,68 @@ namespace GameRes.Formats.NScripter
}
#endregion
}
internal class EncryptedViewStream : ViewStreamBase
{
byte[] m_key;
static readonly HashAlgorithm MD5 = System.Security.Cryptography.MD5.Create();
static readonly HashAlgorithm SHA1 = System.Security.Cryptography.SHA1.Create();
public EncryptedViewStream (ArcView mmap, byte[] key) : base (mmap)
{
m_key = key;
}
protected override void DecryptBlock ()
{
int block_num = (int)(m_current_block_position / BlockLength);
byte[] bn = new byte[8];
LittleEndian.Pack (block_num, bn, 0);
var md5_hash = MD5.ComputeHash (bn);
var sha1_hash = SHA1.ComputeHash (bn);
var hmac_key = new byte[16];
for (int i = 0; i < 16; i++)
hmac_key[i] = (byte)(md5_hash[i] ^ sha1_hash[i]);
byte[] hmac_hash;
using (var HMAC = new HMACSHA512 (hmac_key))
hmac_hash = HMAC.ComputeHash (m_key);
int[] map = Enumerable.Range (0, 256).ToArray();
byte index = 0;
int h = 0;
for (int i = 0; i < 256; i++)
{
if (hmac_hash.Length == h)
h = 0;
int tmp = map[i];
index = (byte)(tmp + hmac_hash[h++] + index);
map[i] = map[index];
map[index] = tmp;
}
int i0 = 0, i1 = 0;
for (int i = 0; i < 300; i++)
{
i0 = (i0 + 1) & 0xFF;
int tmp = map[i0];
i1 = (i1 + tmp) & 0xFF;
map[i0] = map[i1];
map[i1] = tmp;
}
for (int i = 0; i < m_current_block_length; i++)
{
i0 = (i0 + 1) & 0xFF;
int tmp = map[i0];
i1 = (i1 + tmp) & 0xFF;
map[i0] = map[i1];
map[i1] = tmp;
m_current_block[i] ^= (byte)map[(map[i0] + tmp) & 0xFF];
}
}
}
}