/*

 * Dropbear SSH

 * 

 * Copyright (c) 2002,2003 Matt Johnston

 * Copyright (c) 2020 by Vladislav Grishenko

 * All rights reserved.

 * 

 * 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 "includes.h"

#include "algo.h"

#include "dbutil.h"

#include "chachapoly.h"

#if DROPBEAR_CHACHA20POLY1305

#define CHACHA20_KEY_LEN 32

#define CHACHA20_BLOCKSIZE 8

#define POLY1305_KEY_LEN 32

#define POLY1305_TAG_LEN 16

static const struct ltc_cipher_descriptor dummy = {.name = NULL};

static const struct dropbear_hash dropbear_chachapoly_mac =

  {NULL, POLY1305_KEY_LEN, POLY1305_TAG_LEN};

const struct dropbear_cipher dropbear_chachapoly =

  {&dummy, CHACHA20_KEY_LEN*2, CHACHA20_BLOCKSIZE};

static int dropbear_chachapoly_start(int UNUSED(cipher), const unsigned char* UNUSED(IV),

      const unsigned char *key, int keylen,

      int UNUSED(num_rounds), dropbear_chachapoly_state *state) {

  int err;

  TRACE2(("enter dropbear_chachapoly_start"))

  if (keylen != CHACHA20_KEY_LEN*2) {

    return CRYPT_ERROR;

  }

  if ((err = chacha_setup(&state->chacha, key,

        CHACHA20_KEY_LEN, 20)) != CRYPT_OK) {

    return err;

  }

  if ((err = chacha_setup(&state->header, key + CHACHA20_KEY_LEN,

        CHACHA20_KEY_LEN, 20) != CRYPT_OK)) {

    return err;

  }

  TRACE2(("leave dropbear_chachapoly_start"))

  return CRYPT_OK;

}

static int dropbear_chachapoly_crypt(unsigned int seq,

      const unsigned char *in, unsigned char *out,

      unsigned long len, unsigned long taglen,

      dropbear_chachapoly_state *state, int direction) {

  poly1305_state poly;

  unsigned char seqbuf[8], key[POLY1305_KEY_LEN], tag[POLY1305_TAG_LEN];

  int err;

  TRACE2(("enter dropbear_chachapoly_crypt"))

  if (len < 4 || taglen != POLY1305_TAG_LEN) {

    return CRYPT_ERROR;

  }

  STORE64H((uint64_t)seq, seqbuf);

  chacha_ivctr64(&state->chacha, seqbuf, sizeof(seqbuf), 0);

  if ((err = chacha_keystream(&state->chacha, key, sizeof(key))) != CRYPT_OK) {

    return err;

  }

  poly1305_init(&poly, key, sizeof(key));

  if (direction == LTC_DECRYPT) {

    poly1305_process(&poly, in, len);

    poly1305_done(&poly, tag, &taglen);

    if (constant_time_memcmp(in + len, tag, taglen) != 0) {

      return CRYPT_ERROR;

    }

  }

  chacha_ivctr64(&state->header, seqbuf, sizeof(seqbuf), 0);

  if ((err = chacha_crypt(&state->header, in, 4, out)) != CRYPT_OK) {

    return err;

  }

  chacha_ivctr64(&state->chacha, seqbuf, sizeof(seqbuf), 1);

  if ((err = chacha_crypt(&state->chacha, in + 4, len - 4, out + 4)) != CRYPT_OK) {

    return err;

  }

  if (direction == LTC_ENCRYPT) {

    poly1305_process(&poly, out, len);

    poly1305_done(&poly, out + len, &taglen);

  }

  TRACE2(("leave dropbear_chachapoly_crypt"))

  return CRYPT_OK;

}

static int dropbear_chachapoly_getlength(unsigned int seq,

      const unsigned char *in, unsigned int *outlen,

      unsigned long len, dropbear_chachapoly_state *state) {

  unsigned char seqbuf[8], buf[4];

  int err;

  TRACE2(("enter dropbear_chachapoly_getlength"))

  if (len < sizeof(buf)) {

    return CRYPT_ERROR;

  }

  STORE64H((uint64_t)seq, seqbuf);

  chacha_ivctr64(&state->header, seqbuf, sizeof(seqbuf), 0);

  if ((err = chacha_crypt(&state->header, in, sizeof(buf), buf)) != CRYPT_OK) {

    return err;

  }

  LOAD32H(*outlen, buf);

  TRACE2(("leave dropbear_chachapoly_getlength"))

  return CRYPT_OK;

}

const struct dropbear_cipher_mode dropbear_mode_chachapoly =

  {(void *)dropbear_chachapoly_start, NULL, NULL,

   (void *)dropbear_chachapoly_crypt,

   (void *)dropbear_chachapoly_getlength, &dropbear_chachapoly_mac};

#endif /* DROPBEAR_CHACHA20POLY1305 */