/*
 * This file was originally licensed
 * under Apache 2.0 (https://www.apache.org/licenses/LICENSE-2.0.html) or
 * public domain at https://github.com/pq-crystals/dilithium/tree/master/ref
 *
 * We choose
 * CC0 1.0 Universal or the following MIT License
 *
 * MIT License
 *
 * Copyright (c) 2023: Hanno Becker, Vincent Hwang, Matthias J. Kannwischer, Bo-Yin Yang, and Shang-Yi Yang
 *
 * 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 "fips202.h"
#include "packing.h"
#include "params.h"
#include "poly.h"
#include "polyvec.h"
#include "randombytes.h"
#include "sign.h"
#include "symmetric.h"
#include <stdint.h>

/*************************************************
* Name:        crypto_sign_keypair
*
* Description: Generates public and private key.
*
* Arguments:   - uint8_t *pk: pointer to output public key (allocated
*                             array of CRYPTO_PUBLICKEYBYTES bytes)
*              - uint8_t *sk: pointer to output private key (allocated
*                             array of CRYPTO_SECRETKEYBYTES bytes)
*
* Returns 0 (success)
**************************************************/
int crypto_sign_keypair(uint8_t *pk, uint8_t *sk) {
    uint8_t seedbuf[2 * SEEDBYTES + CRHBYTES];
    uint8_t tr[TRBYTES];
    const uint8_t *rho, *rhoprime, *key;
    polyvecl mat[K];
    polyvecl s1, s1hat;
    polyveck s2, t1, t0;

    /* Get randomness for rho, rhoprime and key */
    randombytes(seedbuf, SEEDBYTES);
    shake256(seedbuf, 2 * SEEDBYTES + CRHBYTES, seedbuf, SEEDBYTES);
    rho = seedbuf;
    rhoprime = rho + SEEDBYTES;
    key = rhoprime + CRHBYTES;

    /* Expand matrix */
    polyvec_matrix_expand(mat, rho);

    /* Sample short vectors s1 and s2 */
    polyvecl_uniform_eta(&s1, rhoprime, 0);
    polyveck_uniform_eta(&s2, rhoprime, L);

    /* Matrix-vector multiplication */
    s1hat = s1;
    polyvecl_ntt(&s1hat);
    polyvec_matrix_pointwise_montgomery(&t1, mat, &s1hat);
    polyveck_reduce(&t1);
    polyveck_invntt_tomont(&t1);

    /* Add error vector s2 */
    polyveck_add(&t1, &t1, &s2);

    /* Extract t1 and write public key */
    polyveck_caddq(&t1);
    polyveck_power2round(&t1, &t0, &t1);
    pack_pk(pk, rho, &t1);

    /* Compute H(rho, t1) and write secret key */
    shake256(tr, TRBYTES, pk, CRYPTO_PUBLICKEYBYTES);
    pack_sk(sk, rho, tr, key, &t0, &s1, &s2);

    return 0;
}

/*************************************************
* Name:        crypto_sign_signature
*
* Description: Computes signature.
*
* Arguments:   - uint8_t *sig:   pointer to output signature (of length CRYPTO_BYTES)
*              - size_t *siglen: pointer to output length of signature
*              - uint8_t *m:     pointer to message to be signed
*              - size_t mlen:    length of message
*              - uint8_t *sk:    pointer to bit-packed secret key
*
* Returns 0 (success)
**************************************************/
int crypto_sign_signature(uint8_t *sig,
                          size_t *siglen,
                          const uint8_t *m,
                          size_t mlen,
                          const uint8_t *sk) {
    unsigned int n;
    uint8_t seedbuf[2 * SEEDBYTES + TRBYTES + RNDBYTES + 2 * CRHBYTES];
    uint8_t *rho, *tr, *key, *mu, *rhoprime, *rnd;
    uint16_t nonce = 0;
    polyvecl mat[K], s1, y, z;
    polyveck t0, s2, w1, w0, h;
    poly cp;
    shake256incctx state;

    rho = seedbuf;
    tr = rho + SEEDBYTES;
    key = tr + TRBYTES;
    rnd = key + SEEDBYTES;
    mu = rnd + RNDBYTES;
    rhoprime = mu + CRHBYTES;
    unpack_sk(rho, tr, key, &t0, &s1, &s2, sk);

    /* Compute mu = CRH(tr, msg) */
    shake256_inc_init(&state);
    shake256_inc_absorb(&state, tr, TRBYTES);
    shake256_inc_absorb(&state, m, mlen);
    shake256_inc_finalize(&state);
    shake256_inc_squeeze(mu, CRHBYTES, &state);
    shake256_inc_ctx_release(&state);

    for (n = 0; n < RNDBYTES; n++) {
        rnd[n] = 0;
    }
    shake256(rhoprime, CRHBYTES, key, SEEDBYTES + RNDBYTES + CRHBYTES);

    /* Expand matrix and transform vectors */
    polyvec_matrix_expand(mat, rho);
    polyvecl_ntt(&s1);
    polyveck_ntt(&s2);
    polyveck_ntt(&t0);

rej:
    /* Sample intermediate vector y */
    polyvecl_uniform_gamma1(&y, rhoprime, nonce++);

    /* Matrix-vector multiplication */
    z = y;
    polyvecl_ntt(&z);
    polyvec_matrix_pointwise_montgomery(&w1, mat, &z);
    polyveck_reduce(&w1);
    polyveck_invntt_tomont(&w1);

    /* Decompose w and call the random oracle */
    polyveck_caddq(&w1);
    polyveck_decompose(&w1, &w0, &w1);
    polyveck_pack_w1(sig, &w1);

    shake256_inc_init(&state);
    shake256_inc_absorb(&state, mu, CRHBYTES);
    shake256_inc_absorb(&state, sig, K * POLYW1_PACKEDBYTES);
    shake256_inc_finalize(&state);
    shake256_inc_squeeze(sig, CTILDEBYTES, &state);
    shake256_inc_ctx_release(&state);
    poly_challenge(&cp, sig);
    poly_ntt(&cp);

    /* Compute z, reject if it reveals secret */
    polyvecl_pointwise_poly_montgomery(&z, &cp, &s1);
    polyvecl_invntt_tomont(&z);
    polyvecl_add(&z, &z, &y);
    polyvecl_reduce(&z);
    if (polyvecl_chknorm(&z, GAMMA1 - BETA)) {
        goto rej;
    }

    /* Check that subtracting cs2 does not change high bits of w and low bits
     * do not reveal secret information */
    polyveck_pointwise_poly_montgomery(&h, &cp, &s2);
    polyveck_invntt_tomont(&h);
    polyveck_sub(&w0, &w0, &h);
    polyveck_reduce(&w0);
    if (polyveck_chknorm(&w0, GAMMA2 - BETA)) {
        goto rej;
    }

    /* Compute hints for w1 */
    polyveck_pointwise_poly_montgomery(&h, &cp, &t0);
    polyveck_invntt_tomont(&h);
    polyveck_reduce(&h);
    if (polyveck_chknorm(&h, GAMMA2)) {
        goto rej;
    }

    polyveck_add(&w0, &w0, &h);
    n = polyveck_make_hint(&h, &w0, &w1);
    if (n > OMEGA) {
        goto rej;
    }

    /* Write signature */
    pack_sig(sig, sig, &z, &h);
    *siglen = CRYPTO_BYTES;
    return 0;
}

/*************************************************
* Name:        crypto_sign
*
* Description: Compute signed message.
*
* Arguments:   - uint8_t *sm: pointer to output signed message (allocated
*                             array with CRYPTO_BYTES + mlen bytes),
*                             can be equal to m
*              - size_t *smlen: pointer to output length of signed
*                               message
*              - const uint8_t *m: pointer to message to be signed
*              - size_t mlen: length of message
*              - const uint8_t *sk: pointer to bit-packed secret key
*
* Returns 0 (success)
**************************************************/
int crypto_sign(uint8_t *sm,
                size_t *smlen,
                const uint8_t *m,
                size_t mlen,
                const uint8_t *sk) {
    size_t i;

    for (i = 0; i < mlen; ++i) {
        sm[CRYPTO_BYTES + mlen - 1 - i] = m[mlen - 1 - i];
    }
    crypto_sign_signature(sm, smlen, sm + CRYPTO_BYTES, mlen, sk);
    *smlen += mlen;
    return 0;
}

/*************************************************
* Name:        crypto_sign_verify
*
* Description: Verifies signature.
*
* Arguments:   - uint8_t *m: pointer to input signature
*              - size_t siglen: length of signature
*              - const uint8_t *m: pointer to message
*              - size_t mlen: length of message
*              - const uint8_t *pk: pointer to bit-packed public key
*
* Returns 0 if signature could be verified correctly and -1 otherwise
**************************************************/
int crypto_sign_verify(const uint8_t *sig,
                       size_t siglen,
                       const uint8_t *m,
                       size_t mlen,
                       const uint8_t *pk) {
    unsigned int i;
    uint8_t buf[K * POLYW1_PACKEDBYTES];
    uint8_t rho[SEEDBYTES];
    uint8_t mu[CRHBYTES];
    uint8_t c[CTILDEBYTES];
    uint8_t c2[CTILDEBYTES];
    poly cp;
    polyvecl mat[K], z;
    polyveck t1, w1, h;
    shake256incctx state;

    if (siglen != CRYPTO_BYTES) {
        return -1;
    }

    unpack_pk(rho, &t1, pk);
    if (unpack_sig(c, &z, &h, sig)) {
        return -1;
    }
    if (polyvecl_chknorm(&z, GAMMA1 - BETA)) {
        return -1;
    }

    /* Compute CRH(H(rho, t1), msg) */
    shake256(mu, CRHBYTES, pk, CRYPTO_PUBLICKEYBYTES);
    shake256_inc_init(&state);
    shake256_inc_absorb(&state, mu, CRHBYTES);
    shake256_inc_absorb(&state, m, mlen);
    shake256_inc_finalize(&state);
    shake256_inc_squeeze(mu, CRHBYTES, &state);
    shake256_inc_ctx_release(&state);

    /* Matrix-vector multiplication; compute Az - c2^dt1 */
    poly_challenge(&cp, c);
    polyvec_matrix_expand(mat, rho);

    polyvecl_ntt(&z);
    polyvec_matrix_pointwise_montgomery(&w1, mat, &z);

    poly_ntt(&cp);
    polyveck_shiftl(&t1);
    polyveck_ntt(&t1);
    polyveck_pointwise_poly_montgomery(&t1, &cp, &t1);

    polyveck_sub(&w1, &w1, &t1);
    polyveck_reduce(&w1);
    polyveck_invntt_tomont(&w1);

    /* Reconstruct w1 */
    polyveck_caddq(&w1);
    polyveck_use_hint(&w1, &w1, &h);
    polyveck_pack_w1(buf, &w1);

    /* Call random oracle and verify challenge */
    shake256_inc_init(&state);
    shake256_inc_absorb(&state, mu, CRHBYTES);
    shake256_inc_absorb(&state, buf, K * POLYW1_PACKEDBYTES);
    shake256_inc_finalize(&state);
    shake256_inc_squeeze(c2, CTILDEBYTES, &state);
    shake256_inc_ctx_release(&state);
    for (i = 0; i < CTILDEBYTES; ++i) {
        if (c[i] != c2[i]) {
            return -1;
        }
    }

    return 0;
}

/*************************************************
* Name:        crypto_sign_open
*
* Description: Verify signed message.
*
* Arguments:   - uint8_t *m: pointer to output message (allocated
*                            array with smlen bytes), can be equal to sm
*              - size_t *mlen: pointer to output length of message
*              - const uint8_t *sm: pointer to signed message
*              - size_t smlen: length of signed message
*              - const uint8_t *pk: pointer to bit-packed public key
*
* Returns 0 if signed message could be verified correctly and -1 otherwise
**************************************************/
int crypto_sign_open(uint8_t *m,
                     size_t *mlen,
                     const uint8_t *sm,
                     size_t smlen,
                     const uint8_t *pk) {
    size_t i;

    if (smlen < CRYPTO_BYTES) {
        goto badsig;
    }

    *mlen = smlen - CRYPTO_BYTES;
    if (crypto_sign_verify(sm, CRYPTO_BYTES, sm + CRYPTO_BYTES, *mlen, pk)) {
        goto badsig;
    } else {
        /* All good, copy msg, return 0 */
        for (i = 0; i < *mlen; ++i) {
            m[i] = sm[CRYPTO_BYTES + i];
        }
        return 0;
    }

badsig:
    /* Signature verification failed */
    *mlen = (size_t) -1;
    for (i = 0; i < smlen; ++i) {
        m[i] = 0;
    }

    return -1;
}