md2.c

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#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

    #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


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));
}

void md2_init(Md2Context *context)
{

    memset(context, 0, sizeof(Md2Context));

}

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;
        }
    }


}
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.
}
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