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

/**
  Initialize a CCM state
  @param ccm     The CCM state to initialize
  @param cipher  The index of the cipher to use
  @param key     The secret key
  @param keylen  The length of the secret key
  @param ptlen   The length of the plain/cipher text that will be processed
  @param taglen  The max length of the MAC tag
  @param aadlen  The length of the AAD

  @return CRYPT_OK on success
 */
int ccm_init(ccm_state *ccm, int cipher,
             const unsigned char *key, int keylen, int ptlen, int taglen, int aadlen)
{
   int            err;

   LTC_ARGCHK(ccm    != NULL);
   LTC_ARGCHK(key    != NULL);
   LTC_ARGCHK(taglen != 0);

   XMEMSET(ccm, 0, sizeof(ccm_state));

   /* check cipher input */
   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
      return err;
   }
   if (cipher_descriptor[cipher].block_length != 16) {
      return CRYPT_INVALID_CIPHER;
   }

   /* make sure the taglen is even and <= 16 */
   ccm->taglen = taglen;
   ccm->taglen &= ~1;
   if (ccm->taglen > 16) {
      ccm->taglen = 16;
   }

   /* can't use < 4 */
   if (ccm->taglen < 4) {
      return CRYPT_INVALID_ARG;
   }

   /* schedule key */
   if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ccm->K)) != CRYPT_OK) {
      return err;
   }
   ccm->cipher = cipher;

   /* let's get the L value */
   ccm->ptlen = ptlen;
   ccm->L   = 0;
   while (ptlen) {
      ++ccm->L;
      ptlen >>= 8;
   }
   if (ccm->L <= 1) {
      ccm->L = 2;
   }

   ccm->aadlen = aadlen;
   return CRYPT_OK;
}

#endif

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