/*
 *  Copyright (C) 2021 - This file is part of libecc project
 *
 *  Authors:
 *      Ryad BENADJILA <ryadbenadjila@gmail.com>
 *      Arnaud EBALARD <arnaud.ebalard@ssi.gouv.fr>
 *
 *  This software is licensed under a dual BSD and GPL v2 license.
 *  See LICENSE file at the root folder of the project.
 */
#include "md2.h"

/* All the inner MD-2 operations */
static const u8 PI_SUBST[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
};

/* MD-2 core processing. Returns 0 on success, -1 on error. */
ATTRIBUTE_WARN_UNUSED_RET static inline int md2_process(md2_context *ctx,
                           const u8 data[MD2_BLOCK_SIZE])
{
        int ret;
        unsigned int i, j, t;
        u8 x[3 * MD2_BLOCK_SIZE];

        MUST_HAVE((data != NULL), ret, err);
        MD2_HASH_CHECK_INITIALIZED(ctx, ret, err);

        /* Form state, block, state ^ block */
        ret = local_memcpy(&x[0], ctx->md2_state, MD2_BLOCK_SIZE); EG(ret, err);
        ret = local_memcpy(&x[MD2_BLOCK_SIZE], data, MD2_BLOCK_SIZE); EG(ret, err);
        for(i = 0; i < MD2_BLOCK_SIZE; i++){
                x[(2 * MD2_BLOCK_SIZE) + i] = (ctx->md2_state[i] ^ data[i]);
        }
        /* Encrypt the block during 18 rounds */
        t = 0;
        for(i = 0; i < 18; i++){
                for (j = 0; j < (3 * MD2_BLOCK_SIZE); j++){
                        x[j] ^= PI_SUBST[t];
                        t = x[j];
                }
                t = (t + i) & 0xff;
        }
        /* Save the new state */
        ret = local_memcpy(ctx->md2_state, &x[0], MD2_BLOCK_SIZE); EG(ret, err);
        /* Update the checksum */
        t = ctx->md2_checksum[MD2_BLOCK_SIZE - 1];
        for(i = 0; i < MD2_BLOCK_SIZE; i++){
                ctx->md2_checksum[i] ^= PI_SUBST[data[i] ^ t];
                t = ctx->md2_checksum[i];
        }

        /* Zeroize x as not needed anymore */
        ret = local_memset(x, 0, sizeof(x)); EG(ret, err);

        ret = 0;

err:
        return ret;
}

/* Init hash function. Returns 0 on success, -1 on error. */
ATTRIBUTE_WARN_UNUSED_RET int md2_init(md2_context *ctx)
{
        int ret;

        MUST_HAVE((ctx != NULL), ret, err);

        /* Sanity check on size */
        MUST_HAVE((MD2_DIGEST_SIZE <= MAX_DIGEST_SIZE), ret, err);

        ctx->md2_total = 0;
        /* Zeroize the state */
        ret = local_memset(ctx->md2_state, 0, sizeof(ctx->md2_state)); EG(ret, err);
        /* Zeroize the checksum */
        ret = local_memset(ctx->md2_checksum, 0, sizeof(ctx->md2_checksum)); EG(ret, err);

        /* Tell that we are initialized */
        ctx->magic = MD2_HASH_MAGIC;

        ret = 0;

err:
        return ret;
}

ATTRIBUTE_WARN_UNUSED_RET int md2_update(md2_context *ctx, const u8 *input, u32 ilen)
{
        const u8 *data_ptr = input;
        u32 remain_ilen = ilen;
        u16 fill;
        u8 left;
        int ret;

        MUST_HAVE((input != NULL) || (ilen == 0), ret, err);
        MD2_HASH_CHECK_INITIALIZED(ctx, ret, err);

        /* Nothing to process, return */
        if (ilen == 0) {
                ret = 0;
                goto err;
        }

        /* Get what's left in our local buffer */
        left = (ctx->md2_total & 0xF);
        fill = (u16)(MD2_BLOCK_SIZE - left);

        ctx->md2_total += ilen;

        if ((left > 0) && (remain_ilen >= fill)) {
                /* Copy data at the end of the buffer */
                ret = local_memcpy(ctx->md2_buffer + left, data_ptr, fill); EG(ret, err);
                ret = md2_process(ctx, ctx->md2_buffer); EG(ret, err);
                data_ptr += fill;
                remain_ilen -= fill;
                left = 0;
        }

        while (remain_ilen >= MD2_BLOCK_SIZE) {
                ret = md2_process(ctx, data_ptr); EG(ret, err);
                data_ptr += MD2_BLOCK_SIZE;
                remain_ilen -= MD2_BLOCK_SIZE;
        }

        if (remain_ilen > 0) {
                ret = local_memcpy(ctx->md2_buffer + left, data_ptr, remain_ilen); EG(ret, err);
        }

        ret = 0;

err:
        return ret;
}

/* Finalize. Returns 0 on success, -1 on error.*/
ATTRIBUTE_WARN_UNUSED_RET int md2_final(md2_context *ctx, u8 output[MD2_DIGEST_SIZE])
{
        int ret;
        unsigned int i;
        u8 pad_byte;

        MUST_HAVE((output != NULL), ret, err);
        MD2_HASH_CHECK_INITIALIZED(ctx, ret, err);

        /* This is our final step, so we proceed with the padding */
        pad_byte = (u8)(MD2_BLOCK_SIZE - (ctx->md2_total % MD2_BLOCK_SIZE));
        for(i = (ctx->md2_total % MD2_BLOCK_SIZE); i < MD2_BLOCK_SIZE; i++){
                ctx->md2_buffer[i] = pad_byte;
        }
        /* And process the block */
        ret = md2_process(ctx, ctx->md2_buffer); EG(ret, err);

        /* Also process the checksum */
        ret = md2_process(ctx, ctx->md2_checksum); EG(ret, err);

        /* Output the hash result */
        ret = local_memcpy(output, ctx->md2_state, MD2_DIGEST_SIZE); EG(ret, err);

        /* Tell that we are uninitialized */
        ctx->magic = WORD(0);

        ret = 0;

err:
        return ret;
}


/*
 * Scattered version performing init/update/finalize on a vector of buffers
 * 'inputs' with the length of each buffer passed via 'ilens'. The function
 * loops on pointers in 'inputs' until it finds a NULL pointer. The function
 * returns 0 on success, -1 on error.
 */
ATTRIBUTE_WARN_UNUSED_RET int md2_scattered(const u8 **inputs, const u32 *ilens,
                      u8 output[MD2_DIGEST_SIZE])
{
        md2_context ctx;
        int ret, pos = 0;

        MUST_HAVE((inputs != NULL) && (ilens != NULL) && (output != NULL), ret, err);

        ret = md2_init(&ctx); EG(ret, err);

        while (inputs[pos] != NULL) {
                ret = md2_update(&ctx, inputs[pos], ilens[pos]); EG(ret, err);
                pos += 1;
        }

        ret = md2_final(&ctx, output);

err:
        return ret;
}

/*
 * Single call version performing init/update/final on given input.
 * Returns 0 on success, -1 on error.
 */
ATTRIBUTE_WARN_UNUSED_RET int md2(const u8 *input, u32 ilen, u8 output[MD2_DIGEST_SIZE])
{
        md2_context ctx;
        int ret;

        ret = md2_init(&ctx); EG(ret, err);
        ret = md2_update(&ctx, input, ilen); EG(ret, err);
        ret = md2_final(&ctx, output);

err:
        return ret;
}