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 omac_done.c
  OMAC1 support, terminate a stream, Tom St Denis
*/

#ifdef LTC_OMAC

/**
  Terminate an OMAC stream
  @param omac   The OMAC state
  @param out    [out] Destination for the authentication tag
  @param outlen [in/out]  The max size and resulting size of the authentication tag
  @return CRYPT_OK if successful
*/
int omac_done(omac_state *omac, unsigned char *out, unsigned long *outlen)
{
   int       err, mode;
   unsigned  x;

   LTC_ARGCHK(omac   != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(outlen != NULL);
   if ((err = cipher_is_valid(omac->cipher_idx)) != CRYPT_OK) {
      return err;
   }

   if ((omac->buflen > (int)sizeof(omac->block)) || (omac->buflen < 0) ||
       (omac->blklen > (int)sizeof(omac->block)) || (omac->buflen > omac->blklen)) {
      return CRYPT_INVALID_ARG;
   }

   /* figure out mode */
   if (omac->buflen != omac->blklen) {
      /* add the 0x80 byte */
      omac->block[omac->buflen++] = 0x80;

      /* pad with 0x00 */
      while (omac->buflen < omac->blklen) {
         omac->block[omac->buflen++] = 0x00;
      }
      mode = 1;
   } else {
      mode = 0;
   }

   /* now xor prev + Lu[mode] */
   for (x = 0; x < (unsigned)omac->blklen; x++) {
       omac->block[x] ^= omac->prev[x] ^ omac->Lu[mode][x];
   }

   /* encrypt it */
   if ((err = cipher_descriptor[omac->cipher_idx].ecb_encrypt(omac->block, omac->block, &omac->key)) != CRYPT_OK) {
      return err;
   }
   cipher_descriptor[omac->cipher_idx].done(&omac->key);

   /* output it */
   for (x = 0; x < (unsigned)omac->blklen && x < *outlen; x++) {
       out[x] = omac->block[x];
   }
   *outlen = x;

#ifdef LTC_CLEAN_STACK
   zeromem(omac, sizeof(*omac));
#endif
   return CRYPT_OK;
}

#endif


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