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_MDH

static int _dh_groupsize_to_keysize(int groupsize)
{
   /* The strength estimates from https://tools.ietf.org/html/rfc3526#section-8
    * We use "Estimate 2" to get an appropriate private key (exponent) size.
    */
   if (groupsize <= 0) {
      return 0;
   }
   else if (groupsize <= 192) {
      return 30;     /* 1536-bit => key size 240-bit */
   }
   else if (groupsize <= 256) {
      return 40;     /* 2048-bit => key size 320-bit */
   }
   else if (groupsize <= 384) {
      return 52;     /* 3072-bit => key size 416-bit */
   }
   else if (groupsize <= 512) {
      return 60;     /* 4096-bit => key size 480-bit */
   }
   else if (groupsize <= 768) {
      return 67;     /* 6144-bit => key size 536-bit */
   }
   else if (groupsize <= 1024) {
      return 77;     /* 8192-bit => key size 616-bit */
   }
   else {
      return 0;
   }
}

int dh_generate_key(prng_state *prng, int wprng, dh_key *key)
{
   unsigned char *buf;
   unsigned long keysize;
   int err, max_iterations = LTC_PK_MAX_RETRIES;

   LTC_ARGCHK(key         != NULL);
   LTC_ARGCHK(ltc_mp.name != NULL);

   /* good prng? */
   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
      return err;
   }

   keysize = _dh_groupsize_to_keysize(mp_unsigned_bin_size(key->prime));
   if (keysize == 0) {
      err = CRYPT_INVALID_KEYSIZE;
      goto freemp;
   }

   /* allocate buffer */
   buf = XMALLOC(keysize);
   if (buf == NULL) {
      err = CRYPT_MEM;
      goto freemp;
   }

   key->type = PK_PRIVATE;
   do {
      /* make up random buf */
      if (prng_descriptor[wprng].read(buf, keysize, prng) != keysize) {
         err = CRYPT_ERROR_READPRNG;
         goto freebuf;
      }
      /* load the x value - private key */
      if ((err = mp_read_unsigned_bin(key->x, buf, keysize)) != CRYPT_OK) {
         goto freebuf;
      }
      /* compute the y value - public key */
      if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) {
         goto freebuf;
      }
      err = dh_check_pubkey(key);
   } while (err != CRYPT_OK && max_iterations-- > 0);

freebuf:
   zeromem(buf, keysize);
   XFREE(buf);
freemp:
   if (err != CRYPT_OK) dh_free(key);
   return err;
}

#endif /* LTC_MDH */

/* ref:         $Format:%D$ */
/* git commit:  $Format:%H$ */
/* commit time: $Format:%ai$ */