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"

/**
   @file cbc_decrypt.c
   CBC implementation, encrypt block, Tom St Denis
*/


#ifdef LTC_CBC_MODE

/**
  CBC decrypt
  @param ct     Ciphertext
  @param pt     [out] Plaintext
  @param len    The number of bytes to process (must be multiple of block length)
  @param cbc    CBC state
  @return CRYPT_OK if successful
*/
int cbc_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CBC *cbc)
{
   int x, err;
   unsigned char tmp[16];
#ifdef LTC_FAST
   LTC_FAST_TYPE tmpy;
#else
   unsigned char tmpy;
#endif

   LTC_ARGCHK(pt  != NULL);
   LTC_ARGCHK(ct  != NULL);
   LTC_ARGCHK(cbc != NULL);

   if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
       return err;
   }

   /* is blocklen valid? */
   if (cbc->blocklen < 1 || cbc->blocklen > (int)sizeof(cbc->IV) || cbc->blocklen > (int)sizeof(tmp)) {
      return CRYPT_INVALID_ARG;
   }

   if (len % cbc->blocklen) {
      return CRYPT_INVALID_ARG;
   }
#ifdef LTC_FAST
   if (cbc->blocklen % sizeof(LTC_FAST_TYPE)) {
      return CRYPT_INVALID_ARG;
   }
#endif

   if (cipher_descriptor[cbc->cipher].accel_cbc_decrypt != NULL) {
      return cipher_descriptor[cbc->cipher].accel_cbc_decrypt(ct, pt, len / cbc->blocklen, cbc->IV, &cbc->key);
   } else {
      while (len) {
         /* decrypt */
         if ((err = cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key)) != CRYPT_OK) {
            return err;
         }

         /* xor IV against plaintext */
         #if defined(LTC_FAST)
         for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) {
            tmpy = *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) ^ *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)tmp + x));
            *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) = *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)ct + x));
            *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)pt + x)) = tmpy;
         }
    #else
         for (x = 0; x < cbc->blocklen; x++) {
            tmpy       = tmp[x] ^ cbc->IV[x];
            cbc->IV[x] = ct[x];
            pt[x]      = tmpy;
         }
    #endif

         ct  += cbc->blocklen;
         pt  += cbc->blocklen;
         len -= cbc->blocklen;
      }
   }
   return CRYPT_OK;
}

#endif

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