/*
 * Copyright (C) 2020 Southern Storm Software, Pty Ltd.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#include "gimli24.h"
#include "internal-gimli24.h"
#include <string.h>

aead_cipher_t const gimli24_cipher = {
    "GIMLI-24",
    GIMLI24_KEY_SIZE,
    GIMLI24_NONCE_SIZE,
    GIMLI24_TAG_SIZE,
    AEAD_FLAG_LITTLE_ENDIAN,
    gimli24_aead_encrypt,
    gimli24_aead_decrypt
};

aead_hash_algorithm_t const gimli24_hash_algorithm = {
    "GIMLI-24-HASH",
    sizeof(gimli24_hash_state_t),
    GIMLI24_HASH_SIZE,
    AEAD_FLAG_LITTLE_ENDIAN,
    gimli24_hash,
    (aead_hash_init_t)gimli24_hash_init,
    (aead_hash_update_t)gimli24_hash_absorb,
    (aead_hash_finalize_t)gimli24_hash_finalize,
    (aead_xof_absorb_t)gimli24_hash_absorb,
    (aead_xof_squeeze_t)gimli24_hash_squeeze
};

/**
 * \brief Number of bytes of input or output data to process per block.
 */
#define GIMLI24_BLOCK_SIZE 16

/**
 * \brief Structure of the GIMLI-24 state as both an array of words
 * and an array of bytes.
 */
typedef union
{
    uint32_t words[12];     /**< Words in the state */
    uint8_t bytes[48];      /**< Bytes in the state */

} gimli24_state_t;

/**
 * \brief Absorbs data into a GIMLI-24 state.
 *
 * \param state The state to absorb the data into.
 * \param data Points to the data to be absorbed.
 * \param len Length of the data to be absorbed.
 */
static void gimli24_absorb
    (gimli24_state_t *state, const unsigned char *data, unsigned long long len)
{
    unsigned temp;
    while (len >= GIMLI24_BLOCK_SIZE) {
        lw_xor_block(state->bytes, data, GIMLI24_BLOCK_SIZE);
        gimli24_permute(state->words);
        data += GIMLI24_BLOCK_SIZE;
        len -= GIMLI24_BLOCK_SIZE;
    }
    temp = (unsigned)len;
    lw_xor_block(state->bytes, data, temp);
    state->bytes[temp] ^= 0x01; /* Padding */
    state->bytes[47] ^= 0x01;
    gimli24_permute(state->words);
}

/**
 * \brief Encrypts a block of data with a GIMLI-24 state.
 *
 * \param state The state to encrypt with.
 * \param dest Points to the destination buffer.
 * \param src Points to the source buffer.
 * \param len Length of the data to encrypt from \a src into \a dest.
 */
static void gimli24_encrypt
    (gimli24_state_t *state, unsigned char *dest,
     const unsigned char *src, unsigned long long len)
{
    unsigned temp;
    while (len >= GIMLI24_BLOCK_SIZE) {
        lw_xor_block_2_dest(dest, state->bytes, src, GIMLI24_BLOCK_SIZE);
        gimli24_permute(state->words);
        dest += GIMLI24_BLOCK_SIZE;
        src += GIMLI24_BLOCK_SIZE;
        len -= GIMLI24_BLOCK_SIZE;
    }
    temp = (unsigned)len;
    lw_xor_block_2_dest(dest, state->bytes, src, temp);
    state->bytes[temp] ^= 0x01; /* Padding */
    state->bytes[47] ^= 0x01;
    gimli24_permute(state->words);
}

/**
 * \brief Decrypts a block of data with a GIMLI-24 state.
 *
 * \param state The state to decrypt with.
 * \param dest Points to the destination buffer.
 * \param src Points to the source buffer.
 * \param len Length of the data to decrypt from \a src into \a dest.
 */
static void gimli24_decrypt
    (gimli24_state_t *state, unsigned char *dest,
     const unsigned char *src, unsigned long long len)
{
    unsigned temp;
    while (len >= GIMLI24_BLOCK_SIZE) {
        lw_xor_block_swap(dest, state->bytes, src, GIMLI24_BLOCK_SIZE);
        gimli24_permute(state->words);
        dest += GIMLI24_BLOCK_SIZE;
        src += GIMLI24_BLOCK_SIZE;
        len -= GIMLI24_BLOCK_SIZE;
    }
    temp = (unsigned)len;
    lw_xor_block_swap(dest, state->bytes, src, temp);
    state->bytes[temp] ^= 0x01; /* Padding */
    state->bytes[47] ^= 0x01;
    gimli24_permute(state->words);
}

int gimli24_aead_encrypt
    (unsigned char *c, unsigned long long *clen,
     const unsigned char *m, unsigned long long mlen,
     const unsigned char *ad, unsigned long long adlen,
     const unsigned char *nsec,
     const unsigned char *npub,
     const unsigned char *k)
{
    gimli24_state_t state;
    (void)nsec;

    /* Set the length of the returned ciphertext */
    *clen = mlen + GIMLI24_TAG_SIZE;

    /* Format the initial GIMLI state from the nonce and the key */
    memcpy(state.words, npub, GIMLI24_NONCE_SIZE);
    memcpy(state.words + 4, k, GIMLI24_KEY_SIZE);

    /* Permute the initial state */
    gimli24_permute(state.words);

    /* Absorb the associated data */
    gimli24_absorb(&state, ad, adlen);

    /* Encrypt the plaintext to produce the ciphertext */
    gimli24_encrypt(&state, c, m, mlen);

    /* Generate the authentication tag at the end of the ciphertext */
    memcpy(c + mlen, state.bytes, GIMLI24_TAG_SIZE);
    return 0;
}

int gimli24_aead_decrypt
    (unsigned char *m, unsigned long long *mlen,
     unsigned char *nsec,
     const unsigned char *c, unsigned long long clen,
     const unsigned char *ad, unsigned long long adlen,
     const unsigned char *npub,
     const unsigned char *k)
{
    gimli24_state_t state;
    (void)nsec;

    /* Validate the ciphertext length and set the return "mlen" value */
    if (clen < GIMLI24_TAG_SIZE)
        return -1;
    *mlen = clen - GIMLI24_TAG_SIZE;

    /* Format the initial GIMLI state from the nonce and the key */
    memcpy(state.words, npub, GIMLI24_NONCE_SIZE);
    memcpy(state.words + 4, k, GIMLI24_KEY_SIZE);

    /* Permute the initial state */
    gimli24_permute(state.words);

    /* Absorb the associated data */
    gimli24_absorb(&state, ad, adlen);

    /* Decrypt the ciphertext to produce the plaintext */
    gimli24_decrypt(&state, m, c, *mlen);

    /* Check the authentication tag at the end of the packet */
    return aead_check_tag
        (m, *mlen, state.bytes, c + *mlen, GIMLI24_TAG_SIZE);
}

int gimli24_hash
    (unsigned char *out, const unsigned char *in, unsigned long long inlen)
{
    gimli24_state_t state;

    /* Initialize the hash state to all zeroes */
    memset(&state, 0, sizeof(state));

    /* Absorb the input */
    gimli24_absorb(&state, in, inlen);

    /* Generate the output hash */
    memcpy(out, state.bytes, GIMLI24_HASH_SIZE / 2);
    gimli24_permute(state.words);
    memcpy(out + GIMLI24_HASH_SIZE / 2, state.bytes, GIMLI24_HASH_SIZE / 2);
    return 0;
}

void gimli24_hash_init(gimli24_hash_state_t *state)
{
    memset(state, 0, sizeof(gimli24_hash_state_t));
}

#define GIMLI24_XOF_RATE 16
#define gimli24_xof_permute() \
    gimli24_permute((uint32_t *)(state->s.state))

void gimli24_hash_absorb
    (gimli24_hash_state_t *state, const unsigned char *in,
     unsigned long long inlen)
{
    unsigned temp;

    if (state->s.mode) {
        /* We were squeezing output - go back to the absorb phase */
        state->s.mode = 0;
        state->s.count = 0;
        gimli24_xof_permute();
    }

    /* Handle the partial left-over block from last time */
    if (state->s.count) {
        temp = GIMLI24_XOF_RATE - state->s.count;
        if (temp > inlen) {
            temp = (unsigned)inlen;
            lw_xor_block(state->s.state + state->s.count, in, temp);
            state->s.count += temp;
            return;
        }
        lw_xor_block(state->s.state + state->s.count, in, temp);
        state->s.count = 0;
        in += temp;
        inlen -= temp;
        gimli24_xof_permute();
    }

    /* Process full blocks that are aligned at state->s.count == 0 */
    while (inlen >= GIMLI24_XOF_RATE) {
        lw_xor_block(state->s.state, in, GIMLI24_XOF_RATE);
        in += GIMLI24_XOF_RATE;
        inlen -= GIMLI24_XOF_RATE;
        gimli24_xof_permute();
    }

    /* Process the left-over block at the end of the input */
    temp = (unsigned)inlen;
    lw_xor_block(state->s.state, in, temp);
    state->s.count = temp;
}

void gimli24_hash_squeeze
    (gimli24_hash_state_t *state, unsigned char *out,
     unsigned long long outlen)
{
    unsigned temp;

    /* Pad the final input block if we were still in the absorb phase */
    if (!state->s.mode) {
        state->s.state[state->s.count] ^= 0x01;
        state->s.state[47] ^= 0x01;
        state->s.count = 0;
        state->s.mode = 1;
    }

    /* Handle left-over partial blocks from last time */
    if (state->s.count) {
        temp = GIMLI24_XOF_RATE - state->s.count;
        if (temp > outlen) {
            temp = (unsigned)outlen;
            memcpy(out, state->s.state + state->s.count, temp);
            state->s.count += temp;
            return;
        }
        memcpy(out, state->s.state + state->s.count, temp);
        out += temp;
        outlen -= temp;
        state->s.count = 0;
    }

    /* Handle full blocks */
    while (outlen >= GIMLI24_XOF_RATE) {
        gimli24_xof_permute();
        memcpy(out, state->s.state, GIMLI24_XOF_RATE);
        out += GIMLI24_XOF_RATE;
        outlen -= GIMLI24_XOF_RATE;
    }

    /* Handle the left-over block */
    if (outlen > 0) {
        temp = (unsigned)outlen;
        gimli24_xof_permute();
        memcpy(out, state->s.state, temp);
        state->s.count = temp;
    }
}

void gimli24_hash_finalize
    (gimli24_hash_state_t *state, unsigned char *out)
{
    gimli24_hash_squeeze(state, out, GIMLI24_HASH_SIZE);
}