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*
* \brief MD2 Message-Digest algorithm.
*
* The MD2 algorithm work with a constant array of 256 permutationt
* defined in RFC1319. If you don't want to use a standard array of
* permutatione you can use a md2_perm() function that generate an
* array of 256 "casual" permutation. To swich from a standard array
* to md2_perm function you must chanche CONFIG_MD2_STD_PERM defined in
* appconfig.h.
* If you need to store array in program memory you must define
* a macro _PROGMEM (for more info see cpu/pgm.h).
*
*
* \author Daniele Basile <asterix@develer.com>
*/
#include "md2.h"
#include <string.h> //memset(), memcpy();
#include <cfg/compiler.h>
#include <cfg/debug.h> //ASSERT()
#include <cfg/macros.h> //MIN(), countof(), ROTR();
#include <cpu/pgm.h>
#if CONFIG_MD2_STD_PERM
/*
* Official array of 256 byte pemutation contructed from digits of pi, defined
* in the RFC 1319.
*/
static const uint8_t PROGMEM md2_perm[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
};
#define MD2_PERM(x) pgm_read8(&md2_perm[x])
#else
/**
* Md2_perm() function generate an array of 256 "casual" permutation.
*/
/**
* Costant define for computing an array of 256 "casual" permutation.
* \{
*/
#define K1 5
#define K2 3
#define R 2
#define X 172
/*\}*/
static uint8_t md2_perm(uint8_t i)
{
i = i * K1;
i = ROTR(i, R);
i ^= X;
i = i * K2;
return i;
}
#define MD2_PERM(x) md2_perm(x)
#endif
/**
* Pad function. Put len_pad unsigned char in
* input block.
*/
static void md2_pad(void *_block, size_t len_pad)
{
uint8_t *block;
block = (uint8_t *)_block;
ASSERT(len_pad <= CONFIG_MD2_BLOCK_LEN);
/*
* Fill input block with len_pad char.
*/
memset(block, len_pad, len_pad);
}
static void md2_compute(void *_state, void *_checksum, void *_block)
{
int i = 0;
uint16_t t = 0;
uint8_t compute_array[COMPUTE_ARRAY_LEN];
uint8_t *state;
uint8_t *checksum;
uint8_t *block;
state = (uint8_t *)_state;
checksum = (uint8_t *)_checksum;
block = (uint8_t *)_block;
/*
* Copy state and checksum context in compute array.
*/
memcpy(compute_array, state, CONFIG_MD2_BLOCK_LEN);
memcpy(compute_array + CONFIG_MD2_BLOCK_LEN, block, CONFIG_MD2_BLOCK_LEN);
/*
* Fill compute array with state XOR block
*/
for(i = 0; i < CONFIG_MD2_BLOCK_LEN; i++)
compute_array[i + (CONFIG_MD2_BLOCK_LEN * 2)] = state[i] ^ block[i];
/*
* Encryt block.
*/
for(i = 0; i < NUM_COMPUTE_ROUNDS; i++)
{
for(int j = 0; j < COMPUTE_ARRAY_LEN; j++)
{
compute_array[j] ^= MD2_PERM(t);
t = compute_array[j];
}
t = (t + i) & 0xff; //modulo 256.
}
/*
* Update checksum.
*/
t = checksum[CONFIG_MD2_BLOCK_LEN - 1];
for(i = 0; i < CONFIG_MD2_BLOCK_LEN; i++)
{
checksum[i] ^= MD2_PERM(block[i] ^ t);
t = checksum[i];
}
/*
* Update state and clean compute array.
*/
memcpy(state, compute_array, CONFIG_MD2_BLOCK_LEN);
memset(compute_array, 0, sizeof(compute_array));
}
/**
* Algorithm initialization.
*
* \param context empty context.
*/
void md2_init(Md2Context *context)
{
memset(context, 0, sizeof(Md2Context));
}
/**
* Update block.
*/
void md2_update(Md2Context *context, const void *_block_in, size_t block_len)
{
const uint8_t *block_in;
size_t cpy_len;
block_in = (const uint8_t *)_block_in;
while(block_len > 0)
{
/*
* Choose a number of block that fill input context buffer.
*/
cpy_len = MIN(block_len, CONFIG_MD2_BLOCK_LEN - context->counter);
/*
* Copy in the buffer input block.
*/
memcpy(&context->buffer[context->counter], block_in, cpy_len);
/*
* Update a context counter, input block length and remaning
* context buffer block lenght.
*/
context->counter += cpy_len;
block_len -= cpy_len;
block_in += cpy_len;
/*
* If buffer is full, compute it.
*/
if (context->counter >= CONFIG_MD2_BLOCK_LEN)
{
md2_compute(context->state, context->checksum, context->buffer);
context->counter = 0;
}
}
}
/**
* Ends an MD2 message digest operation.
* This fuction take an context and return a pointer
* to context state.
*
* \param context in input.
* \return a pointer to context state (message digest).
*/
uint8_t *md2_end(Md2Context *context)
{
uint8_t buf[CONFIG_MD2_BLOCK_LEN];
/*
* Fill remaning empty context buffer.
*/
md2_pad(buf, CONFIG_MD2_BLOCK_LEN - context->counter);
/*
* Update context buffer and compute it.
*/
md2_update(context, buf, CONFIG_MD2_BLOCK_LEN - context->counter);
/*
* Add context checksum to message input.
*/
md2_update(context, context->checksum, CONFIG_MD2_BLOCK_LEN);
return context->state; //return a pointer to message digest.
}
/**
* MD2 test fuction.
* This function test MD2 algorithm with a standard string specified
* in RFC 1319.
*
* \note This test work with official array of 256 byte pemutation
* contructed from digits of pi, defined in the RFC 1319.
*
*/
bool md2_test(void)
{
Md2Context context;
const char *test[] =
{
"",
"message digest",
"abcdefghijklmnopqrstuvwxyz",
"12345678901234567890123456789012345678901234567890123456789012345678901234567890"
};
const char *result[] = {
"\x83\x50\xe5\xa3\xe2\x4c\x15\x3d\xf2\x27\x5c\x9f\x80\x69\x27\x73",
"\xab\x4f\x49\x6b\xfb\x2a\x53\x0b\x21\x9f\xf3\x30\x31\xfe\x06\xb0",
"\x4e\x8d\xdf\xf3\x65\x02\x92\xab\x5a\x41\x08\xc3\xaa\x47\x94\x0b",
"\xd5\x97\x6f\x79\xd8\x3d\x3a\x0d\xc9\x80\x6c\x3c\x66\xf3\xef\xd8",
};
for (size_t i = 0; i < countof(test); i++)
{
md2_init(&context);
md2_update(&context, test[i], strlen(test[i]));
if(memcmp(result[i], md2_end(&context), MD2_DIGEST_LEN))
return false;
}
return true;
}
#if 0
#include <stdio.h>
int main(int argc, char * argv[])
{
if(md2_test())
printf("MD2 algorithm work well!\n");
else
printf("MD2 algorithm doesn't work well.\n");
}
#endif