Add Chacha20-Poly1305, AES128-GCM and AES256-GCM support (#93) * Add Chacha20-Poly1305 authenticated encryption * Add general AEAD approach. * Add [email protected] algo using LibTomCrypt chacha and poly1305 routines. Chacha20-Poly1305 is generally faster than AES256 on CPU w/o dedicated AES instructions, having the same key size. Compiling in will add ~5,5kB to binary size on x86-64. function old new delta chacha_crypt - 1397 +1397 _poly1305_block - 608 +608 poly1305_done - 595 +595 dropbear_chachapoly_crypt - 457 +457 .rodata 26976 27392 +416 poly1305_process - 290 +290 poly1305_init - 221 +221 chacha_setup - 218 +218 encrypt_packet 1068 1270 +202 dropbear_chachapoly_getlength - 147 +147 decrypt_packet 756 897 +141 chacha_ivctr64 - 137 +137 read_packet 543 637 +94 dropbear_chachapoly_start - 94 +94 read_kex_algos 792 880 +88 chacha_keystream - 69 +69 dropbear_mode_chachapoly - 48 +48 sshciphers 280 320 +40 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_chachapoly_mac - 24 +24 dropbear_chachapoly - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 5388/0) Total: 5388 bytes * Add AES128-GCM and AES256-GCM authenticated encryption * Add general AES-GCM mode. * Add [email protected] and [email protected] algo using LibTomCrypt gcm routines. AES-GCM is combination of AES CTR mode and GHASH, slower than AES-CTR on CPU w/o dedicated AES/GHASH instructions therefore disabled by default. Compiling in will add ~6kB to binary size on x86-64. function old new delta gcm_process - 1060 +1060 .rodata 26976 27808 +832 gcm_gf_mult - 820 +820 gcm_add_aad - 660 +660 gcm_shift_table - 512 +512 gcm_done - 471 +471 gcm_add_iv - 384 +384 gcm_init - 347 +347 dropbear_gcm_crypt - 309 +309 encrypt_packet 1068 1270 +202 decrypt_packet 756 897 +141 gcm_reset - 118 +118 read_packet 543 637 +94 read_kex_algos 792 880 +88 sshciphers 280 360 +80 gcm_mult_h - 80 +80 dropbear_gcm_start - 62 +62 dropbear_mode_gcm - 48 +48 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_ghash - 24 +24 dropbear_gcm_getlength - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 6434/0) Total: 6434 bytes

#include "tommath_private.h"
#ifdef BN_MP_PRIME_MILLER_RABIN_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is a library that provides multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library was designed directly after the MPI library by
 * Michael Fromberger but has been written from scratch with
 * additional optimizations in place.
 *
 * SPDX-License-Identifier: Unlicense
 */

/* Miller-Rabin test of "a" to the base of "b" as described in
 * HAC pp. 139 Algorithm 4.24
 *
 * Sets result to 0 if definitely composite or 1 if probably prime.
 * Randomly the chance of error is no more than 1/4 and often
 * very much lower.
 */
int mp_prime_miller_rabin(const mp_int *a, const mp_int *b, int *result)
{
   mp_int  n1, y, r;
   int     s, j, err;

   /* default */
   *result = MP_NO;

   /* ensure b > 1 */
   if (mp_cmp_d(b, 1uL) != MP_GT) {
      return MP_VAL;
   }

   /* get n1 = a - 1 */
   if ((err = mp_init_copy(&n1, a)) != MP_OKAY) {
      return err;
   }
   if ((err = mp_sub_d(&n1, 1uL, &n1)) != MP_OKAY) {
      goto LBL_N1;
   }

   /* set 2**s * r = n1 */
   if ((err = mp_init_copy(&r, &n1)) != MP_OKAY) {
      goto LBL_N1;
   }

   /* count the number of least significant bits
    * which are zero
    */
   s = mp_cnt_lsb(&r);

   /* now divide n - 1 by 2**s */
   if ((err = mp_div_2d(&r, s, &r, NULL)) != MP_OKAY) {
      goto LBL_R;
   }

   /* compute y = b**r mod a */
   if ((err = mp_init(&y)) != MP_OKAY) {
      goto LBL_R;
   }
   if ((err = mp_exptmod(b, &r, a, &y)) != MP_OKAY) {
      goto LBL_Y;
   }

   /* if y != 1 and y != n1 do */
   if ((mp_cmp_d(&y, 1uL) != MP_EQ) && (mp_cmp(&y, &n1) != MP_EQ)) {
      j = 1;
      /* while j <= s-1 and y != n1 */
      while ((j <= (s - 1)) && (mp_cmp(&y, &n1) != MP_EQ)) {
         if ((err = mp_sqrmod(&y, a, &y)) != MP_OKAY) {
            goto LBL_Y;
         }

         /* if y == 1 then composite */
         if (mp_cmp_d(&y, 1uL) == MP_EQ) {
            goto LBL_Y;
         }

         ++j;
      }

      /* if y != n1 then composite */
      if (mp_cmp(&y, &n1) != MP_EQ) {
         goto LBL_Y;
      }
   }

   /* probably prime now */
   *result = MP_YES;
LBL_Y:
   mp_clear(&y);
LBL_R:
   mp_clear(&r);
LBL_N1:
   mp_clear(&n1);
   return err;
}
#endif

/* ref:         HEAD -> master, tag: v1.1.0 */
/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
/* commit time: 2019-01-28 20:32:32 +0100 */