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_TC_XOR_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
 */

/* two complement xor */
int mp_tc_xor(const mp_int *a, const mp_int *b, mp_int *c)
{
   int res = MP_OKAY, bits, abits, bbits;
   int as = mp_isneg(a), bs = mp_isneg(b);
   mp_int *mx = NULL, _mx, acpy, bcpy;

   if ((as != MP_NO) || (bs != MP_NO)) {
      abits = mp_count_bits(a);
      bbits = mp_count_bits(b);
      bits = MAX(abits, bbits);
      res = mp_init_set_int(&_mx, 1uL);
      if (res != MP_OKAY) {
         goto end;
      }

      mx = &_mx;
      res = mp_mul_2d(mx, bits + 1, mx);
      if (res != MP_OKAY) {
         goto end;
      }

      if (as != MP_NO) {
         res = mp_init(&acpy);
         if (res != MP_OKAY) {
            goto end;
         }

         res = mp_add(mx, a, &acpy);
         if (res != MP_OKAY) {
            mp_clear(&acpy);
            goto end;
         }
         a = &acpy;
      }
      if (bs != MP_NO) {
         res = mp_init(&bcpy);
         if (res != MP_OKAY) {
            goto end;
         }

         res = mp_add(mx, b, &bcpy);
         if (res != MP_OKAY) {
            mp_clear(&bcpy);
            goto end;
         }
         b = &bcpy;
      }
   }

   res = mp_xor(a, b, c);

   if ((as != bs) && (res == MP_OKAY)) {
      res = mp_sub(c, mx, c);
   }

end:
   if (a == &acpy) {
      mp_clear(&acpy);
   }

   if (b == &bcpy) {
      mp_clear(&bcpy);
   }

   if (mx == &_mx) {
      mp_clear(mx);
   }

   return res;
}
#endif

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