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.
 */

/**
   @file gcm_done.c
   GCM implementation, Terminate the stream, by Tom St Denis
*/
#include "tomcrypt.h"

#ifdef LTC_GCM_MODE

/**
  Terminate a GCM stream
  @param gcm     The GCM state
  @param tag     [out] The destination for the MAC tag
  @param taglen  [in/out]  The length of the MAC tag
  @return CRYPT_OK on success
 */
int gcm_done(gcm_state *gcm,
                     unsigned char *tag,    unsigned long *taglen)
{
   unsigned long x;
   int err;

   LTC_ARGCHK(gcm     != NULL);
   LTC_ARGCHK(tag     != NULL);
   LTC_ARGCHK(taglen  != NULL);

   if (gcm->buflen > 16 || gcm->buflen < 0) {
      return CRYPT_INVALID_ARG;
   }

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

   if (gcm->mode == LTC_GCM_MODE_IV) {
      /* let's process the IV */
      if ((err = gcm_add_aad(gcm, NULL, 0)) != CRYPT_OK) return err;
   }

   if (gcm->mode == LTC_GCM_MODE_AAD) {
      /* let's process the AAD */
      if ((err = gcm_process(gcm, NULL, 0, NULL, 0)) != CRYPT_OK) return err;
   }

   if (gcm->mode != LTC_GCM_MODE_TEXT) {
      return CRYPT_INVALID_ARG;
   }

   /* handle remaining ciphertext */
   if (gcm->buflen) {
      gcm->pttotlen += gcm->buflen * CONST64(8);
      gcm_mult_h(gcm, gcm->X);
   }

   /* length */
   STORE64H(gcm->totlen, gcm->buf);
   STORE64H(gcm->pttotlen, gcm->buf+8);
   for (x = 0; x < 16; x++) {
       gcm->X[x] ^= gcm->buf[x];
   }
   gcm_mult_h(gcm, gcm->X);

   /* encrypt original counter */
   if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y_0, gcm->buf, &gcm->K)) != CRYPT_OK) {
      return err;
   }
   for (x = 0; x < 16 && x < *taglen; x++) {
       tag[x] = gcm->buf[x] ^ gcm->X[x];
   }
   *taglen = x;

   cipher_descriptor[gcm->cipher].done(&gcm->K);

   return CRYPT_OK;
}

#endif


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