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_CHACHA20POLY1305_MODE

/**
  Process an entire GCM packet in one call.
  @param key               The secret key
  @param keylen            The length of the secret key
  @param iv                The initialization vector
  @param ivlen             The length of the initialization vector
  @param aad               The additional authentication data (header)
  @param aadlen            The length of the aad
  @param in                The plaintext
  @param inlen             The length of the plaintext (ciphertext length is the same)
  @param out               The ciphertext
  @param tag               [out] The MAC tag
  @param taglen            [in/out] The MAC tag length
  @param direction         Encrypt or Decrypt mode (CHACHA20POLY1305_ENCRYPT or CHACHA20POLY1305_DECRYPT)
  @return CRYPT_OK on success
 */
int chacha20poly1305_memory(const unsigned char *key, unsigned long keylen,
                            const unsigned char *iv,  unsigned long ivlen,
                            const unsigned char *aad, unsigned long aadlen,
                            const unsigned char *in,  unsigned long inlen,
                                  unsigned char *out,
                                  unsigned char *tag, unsigned long *taglen,
                            int direction)
{
   chacha20poly1305_state st;
   int err;

   LTC_ARGCHK(key != NULL);
   LTC_ARGCHK(iv  != NULL);
   LTC_ARGCHK(in  != NULL);
   LTC_ARGCHK(out != NULL);
   LTC_ARGCHK(tag != NULL);

   if ((err = chacha20poly1305_init(&st, key, keylen)) != CRYPT_OK)          { goto LBL_ERR; }
   if ((err = chacha20poly1305_setiv(&st, iv, ivlen)) != CRYPT_OK)           { goto LBL_ERR; }
   if (aad && aadlen > 0) {
      if ((err = chacha20poly1305_add_aad(&st, aad, aadlen)) != CRYPT_OK)    { goto LBL_ERR; }
   }
   if (direction == CHACHA20POLY1305_ENCRYPT) {
      if ((err = chacha20poly1305_encrypt(&st, in, inlen, out)) != CRYPT_OK) { goto LBL_ERR; }
   }
   else if (direction == CHACHA20POLY1305_DECRYPT) {
      if ((err = chacha20poly1305_decrypt(&st, in, inlen, out)) != CRYPT_OK) { goto LBL_ERR; }
   }
   else {
      err = CRYPT_INVALID_ARG;
      goto LBL_ERR;
   }
   err = chacha20poly1305_done(&st, tag, taglen);
LBL_ERR:
#ifdef LTC_CLEAN_STACK
   zeromem(&st, sizeof(chacha20poly1305_state));
#endif
   return err;
}

#endif

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