// Free implementation of the MD2 hash algorithm

// Based on:
// md2.cpp - modified by Wei Dai from Andrew M. Kuchling's md2.c

// The original code and all modifications are in the public domain.

#include <stdlib.h>
#include <stdio.h>
#include <memory.h>
#include <string.h>

#include "md2.h"

// S-Box based on PI
static unsigned char MD2_S[256] = {
	41, 46, 67, 201, 162, 216, 124, 1, 61, 54, 84, 161, 236, 240, 6,
	19, 98, 167, 5, 243, 192, 199, 115, 140, 152, 147, 43, 217, 188,
	76, 130, 202, 30, 155, 87, 60, 253, 212, 224, 22, 103, 66, 111, 24,
	138, 23, 229, 18, 190, 78, 196, 214, 218, 158, 222, 73, 160, 251,
	245, 142, 187, 47, 238, 122, 169, 104, 121, 145, 21, 178, 7, 63,
	148, 194, 16, 137, 11, 34, 95, 33, 128, 127, 93, 154, 90, 144, 50,
	39, 53, 62, 204, 231, 191, 247, 151, 3, 255, 25, 48, 179, 72, 165,
	181, 209, 215, 94, 146, 42, 172, 86, 170, 198, 79, 184, 56, 210,
	150, 164, 125, 182, 118, 252, 107, 226, 156, 116, 4, 241, 69, 157,
	112, 89, 100, 113, 135, 32, 134, 91, 207, 101, 230, 45, 168, 2, 27,
	96, 37, 173, 174, 176, 185, 246, 28, 70, 97, 105, 52, 64, 126, 15,
	85, 71, 163, 35, 221, 81, 175, 58, 195, 92, 249, 206, 186, 197,
	234, 38, 44, 83, 13, 110, 133, 40, 132, 9, 211, 223, 205, 244, 65,
	129, 77, 82, 106, 220, 55, 200, 108, 193, 171, 250, 36, 225, 123,
	8, 12, 189, 177, 74, 120, 136, 149, 139, 227, 99, 232, 109, 233,
	203, 213, 254, 59, 0, 29, 57, 242, 239, 183, 14, 102, 88, 208, 228,
	166, 119, 114, 248, 235, 117, 75, 10, 49, 68, 80, 180, 143, 237,
	31, 26, 219, 153, 141, 51, 159, 17, 131, 20
};

CMD2::CMD2()
{
	Init();
}

CMD2::~CMD2()
{
	Init();
}

void CMD2::Init()
{
	memset(m_X, 0, 48);
	memset(m_C, 0, 16);
	memset(m_buf, 0, 16);
	m_count = 0;
}

void CMD2::Update(const unsigned char *buf, unsigned int len)
{
	unsigned long L = 0;
	unsigned char t = 0;
	int i = 0, j = 0;

	while(len)
    {
		L = (16 - m_count) < len ? (16 - m_count) : len;
		memcpy(m_buf + m_count, buf, L);
		m_count += L;
		buf += L;
		len -= L;

		if(m_count == 16)
		{
			m_count = 0;
			memcpy(m_X + 16, m_buf, 16);
			t = m_C[15];

			for(i = 0; i < 16; i++)
			{
				m_X[32 + i] = m_X[16 + i] ^ m_X[i];
				t = m_C[i] ^= MD2_S[m_buf[i] ^ t];
			}

			t = 0;
			for(i = 0; i < 18; i++)
			{
				for(j = 0; j < 48; j++)
					t = m_X[j] ^= MD2_S[t];

				t = (t + i) & 0xFF;
			}
		}
    }
}

void CMD2::TruncatedFinal(unsigned char *hash, unsigned int size)
{
	unsigned char padding[16];
	unsigned long padlen = 0;
	unsigned int i = 0;

	padlen = 16 - m_count;

	for(i = 0; i < padlen; i++) padding[i] = (unsigned char)padlen;

	Update(padding, padlen);
	Update(m_C, 16);
	memcpy(hash, m_X, size);

	Init(); // Quickly erase the temporary buffers (security reasons)
}