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using System;
using Org.BouncyCastle.Math;
namespace Org.BouncyCastle.Utilities.SSH
{
public class SSHBuffer
{
private readonly byte[] buffer;
private int pos = 0;
public SSHBuffer(byte[] magic, byte[] buffer)
{
this.buffer = buffer;
for (int i = 0; i != magic.Length; i++)
{
if (magic[i] != buffer[i])
{
throw new ArgumentException("magic-number incorrect");
}
}
pos += magic.Length;
}
public SSHBuffer(byte[] buffer)
{
this.buffer = buffer;
}
public int ReadU32()
{
if (pos > (buffer.Length - 4))
{
throw new ArgumentOutOfRangeException("4 bytes for U32 exceeds buffer.");
}
int i = (buffer[pos++] & 0xFF) << 24;
i |= (buffer[pos++] & 0xFF) << 16;
i |= (buffer[pos++] & 0xFF) << 8;
i |= (buffer[pos++] & 0xFF);
return i;
}
public String ReadString()
{
return Strings.FromByteArray(ReadBlock());
}
public byte[] ReadBlock()
{
int len = ReadU32();
if (len == 0)
{
return new byte[0];
}
if (pos > (buffer.Length - len))
{
throw new ArgumentException("not enough data for block");
}
int start = pos; pos += len;
return Arrays.CopyOfRange(buffer, start, pos);
}
public void SkipBlock()
{
int len = ReadU32();
if (pos > (buffer.Length - len))
{
throw new ArgumentException("not enough data for block");
}
pos += len;
}
public byte[] ReadPaddedBlock()
{
return ReadPaddedBlock(8);
}
public byte[] ReadPaddedBlock(int blockSize)
{
int len = ReadU32();
if (len == 0)
{
return new byte[0];
}
if (pos > (buffer.Length - len))
{
throw new ArgumentException("not enough data for block");
}
int align = len % blockSize;
if (0 != align)
{
throw new ArgumentException("missing padding");
}
int start = pos; pos += len;
int end = pos;
if (len > 0)
{
// TODO If encryption is supported, should be constant-time
int lastByte = buffer[pos - 1] & 0xFF;
if (0 < lastByte && lastByte < blockSize)
{
int padCount = lastByte;
end -= padCount;
for (int i = 1, padPos = end; i <= padCount; ++i, ++padPos)
{
if (i != (buffer[padPos] & 0xFF))
{
throw new ArgumentException("incorrect padding");
}
}
}
}
return Arrays.CopyOfRange(buffer, start, end);
}
public BigInteger ReadBigNumPositive()
{
int len = ReadU32();
if (pos + len > buffer.Length)
{
throw new ArgumentException("not enough data for big num");
}
int start = pos; pos += len;
byte[] d = Arrays.CopyOfRange(buffer, start, pos);
return new BigInteger(1, d);
}
public byte[] GetBuffer()
{
return Arrays.Clone(buffer);
}
public Boolean HasRemaining()
{
return pos < buffer.Length;
}
}
}
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