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#include <stdlib.h>
#include <stdint.h>

#include "des.h"
#include "des_utils.h"
#include "os.h"

/**
 * @brief Rotates 28-bit word
 *
 * Roll right of 28-bit word - used in 28-bit subkey operations
 *
 * @param val 28-bit word to be rotated
 * @param nshift number of bits to rotate by
 *
 * @return val rotated by nshift bits
 */
__forceinline
uint32_t rotate28(const uint32_t val, const unsigned nshift)
{
        const uint32_t mask = (UINT32_C(1) << 28) - UINT32_C(1);

        IMB_ASSERT(nshift <= 28);
        return ((val >> nshift) & mask) |
                ((val << (28 - nshift)) & mask);
}

/**
 * @brief Expands 8 groups of 6bits into 8 groups of 8bits
 *
 * @param in a 48-bit word including 8 groups of 6bits
 *
 * @return 64-bit word with 8 groups of 8bits
 */
__forceinline
uint64_t expand_8x6_to_8x8(const uint64_t in)
{
        return (((in >> (6 * 0)) & UINT64_C(63)) << (8 * 0)) |
                (((in >> (6 * 1)) & UINT64_C(63)) << (8 * 1)) |
                (((in >> (6 * 2)) & UINT64_C(63)) << (8 * 2)) |
                (((in >> (6 * 3)) & UINT64_C(63)) << (8 * 3)) |
                (((in >> (6 * 4)) & UINT64_C(63)) << (8 * 4)) |
                (((in >> (6 * 5)) & UINT64_C(63)) << (8 * 5)) |
                (((in >> (6 * 6)) & UINT64_C(63)) << (8 * 6)) |
                (((in >> (6 * 7)) & UINT64_C(63)) << (8 * 7));
}

static const uint8_t pc1c_table_fips46_3[28] = {
        57, 49, 41, 33, 25, 17,  9,
        1,  58, 50, 42, 34, 26, 18,
        10,  2, 59, 51, 43, 35, 27,
        19, 11,  3, 60, 52, 44, 36
};

static const uint8_t pc1d_table_fips46_3[28] = {
        63, 55, 47, 39, 31, 23, 15,
         7, 62, 54, 46, 38, 30, 22,
        14,  6, 61, 53, 45, 37, 29,
        21, 13,  5, 28, 20, 12, 4
};

static const uint8_t pc2_table_fips46_3[48] = {
        14, 17, 11, 24,  1,  5,
         3, 28, 15,  6, 21, 10,
        23, 19, 12,  4, 26,  8,
        16,  7, 27, 20, 13,  2,
        41, 52, 31, 37, 47, 55,
        30, 40, 51, 45, 33, 48,
        44, 49, 39, 56, 34, 53,
        46, 42, 50, 36, 29, 32
};

static const uint8_t shift_tab_fips46_3[16] = {
        1, 1, 2, 2, 2, 2, 2, 2,
        1, 2, 2, 2, 2, 2, 2, 1
};

int des_key_schedule(uint64_t *ks, const void *key)
{
        uint64_t c, d;
        uint64_t t = 0;
        int n;

        if (key == NULL || ks == NULL)
                return -1;

        /* KEY: 56 bits but spread across 64 bits
         * - MSB per byte used for parity
         * - load_and_convert loads the key and swaps bits in bytes
         *   so that bit numbers are more suitable for LE machine and
         *   FIPS46-3 DES tables
         */
        t = load64_reflect(key);

        /* PC1
         * - built from the KEY, PC1 permute tables skip KEY parity bits
         * - c & d are both 28 bits
         */
        c = permute_64b(t, pc1c_table_fips46_3, IMB_DIM(pc1c_table_fips46_3));
        d = permute_64b(t, pc1d_table_fips46_3, IMB_DIM(pc1d_table_fips46_3));

        /* KS rounds */
        for (n = 0; n < 16; n++) {
                c = rotate28((uint32_t)c, (unsigned) shift_tab_fips46_3[n]);
                d = rotate28((uint32_t)d, (unsigned) shift_tab_fips46_3[n]);

                /* PC2 */
                t = permute_64b(c | (d << 28), pc2_table_fips46_3,
                                IMB_DIM(pc2_table_fips46_3));

                /* store KS as 6 bits per byte and keep LE */
                ks[n] = expand_8x6_to_8x8(t);
        }

        return 0;
}
