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

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */
#include "tomcrypt.h"

#ifdef LTC_CCM_MODE

/**
  Add nonce data to the CCM state
  @param ccm       The CCM state
  @param nonce     The nonce data to add
  @param noncelen  The length of the nonce
  @return CRYPT_OK on success
 */
int ccm_add_nonce(ccm_state *ccm,
                  const unsigned char *nonce,     unsigned long noncelen)
{
   unsigned long x, y, len;
   int           err;

   LTC_ARGCHK(ccm   != NULL);
   LTC_ARGCHK(nonce != NULL);

   /* increase L to match the nonce len */
   ccm->noncelen = (noncelen > 13) ? 13 : noncelen;
   if ((15 - ccm->noncelen) > ccm->L) {
      ccm->L = 15 - ccm->noncelen;
   }

   /* decrease noncelen to match L */
   if ((ccm->noncelen + ccm->L) > 15) {
      ccm->noncelen = 15 - ccm->L;
   }

   /* form B_0 == flags | Nonce N | l(m) */
   x = 0;
   ccm->PAD[x++] = (unsigned char)(((ccm->aadlen > 0) ? (1<<6) : 0) |
                   (((ccm->taglen - 2)>>1)<<3)        |
                   (ccm->L-1));

   /* nonce */
   for (y = 0; y < (16 - (ccm->L + 1)); y++) {
      ccm->PAD[x++] = nonce[y];
   }

   /* store len */
   len = ccm->ptlen;

   /* shift len so the upper bytes of len are the contents of the length */
   for (y = ccm->L; y < 4; y++) {
      len <<= 8;
   }

   /* store l(m) (only store 32-bits) */
   for (y = 0; ccm->L > 4 && (ccm->L-y)>4; y++) {
      ccm->PAD[x++] = 0;
   }
   for (; y < ccm->L; y++) {
      ccm->PAD[x++] = (unsigned char)((len >> 24) & 255);
      len <<= 8;
   }

   /* encrypt PAD */
   if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->PAD, ccm->PAD, &ccm->K)) != CRYPT_OK) {
      return err;
   }

   /* handle header */
   ccm->x = 0;
   if (ccm->aadlen > 0) {
      /* store length */
      if (ccm->aadlen < ((1UL<<16) - (1UL<<8))) {
         ccm->PAD[ccm->x++] ^= (ccm->aadlen>>8) & 255;
         ccm->PAD[ccm->x++] ^= ccm->aadlen & 255;
      } else {
         ccm->PAD[ccm->x++] ^= 0xFF;
         ccm->PAD[ccm->x++] ^= 0xFE;
         ccm->PAD[ccm->x++] ^= (ccm->aadlen>>24) & 255;
         ccm->PAD[ccm->x++] ^= (ccm->aadlen>>16) & 255;
         ccm->PAD[ccm->x++] ^= (ccm->aadlen>>8) & 255;
         ccm->PAD[ccm->x++] ^= ccm->aadlen & 255;
      }
   }

   /* setup the ctr counter */
   x = 0;

   /* flags */
   ccm->ctr[x++] = (unsigned char)ccm->L-1;

   /* nonce */
   for (y = 0; y < (16 - (ccm->L+1)); ++y) {
      ccm->ctr[x++] = nonce[y];
   }
   /* offset */
   while (x < 16) {
      ccm->ctr[x++] = 0;
   }

   ccm->CTRlen = 16;
   return CRYPT_OK;
}

#endif

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