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 der_decode_integer.c
  ASN.1 DER, decode an integer, Tom St Denis
*/


#ifdef LTC_DER

/**
  Read a mp_int integer
  @param in       The DER encoded data
  @param inlen    Size of DER encoded data
  @param num      The first mp_int to decode
  @return CRYPT_OK if successful
*/
int der_decode_integer(const unsigned char *in, unsigned long inlen, void *num)
{
   unsigned long x, y, z;
   int           err;

   LTC_ARGCHK(num    != NULL);
   LTC_ARGCHK(in     != NULL);

   /* min DER INTEGER is 0x02 01 00 == 0 */
   if (inlen < (1 + 1 + 1)) {
      return CRYPT_INVALID_PACKET;
   }

   /* ok expect 0x02 when we AND with 0001 1111 [1F] */
   x = 0;
   if ((in[x++] & 0x1F) != 0x02) {
      return CRYPT_INVALID_PACKET;
   }

   /* now decode the len stuff */
   z = in[x++];

   if ((z & 0x80) == 0x00) {
      /* short form */

      /* will it overflow? */
      if (x + z > inlen) {
         return CRYPT_INVALID_PACKET;
      }

      /* no so read it */
      if ((err = mp_read_unsigned_bin(num, (unsigned char *)in + x, z)) != CRYPT_OK) {
         return err;
      }
   } else {
      /* long form */
      z &= 0x7F;

      /* will number of length bytes overflow? (or > 4) */
      if (((x + z) > inlen) || (z > 4) || (z == 0)) {
         return CRYPT_INVALID_PACKET;
      }

      /* now read it in */
      y = 0;
      while (z--) {
         y = ((unsigned long)(in[x++])) | (y << 8);
      }

      /* now will reading y bytes overrun? */
      if ((x + y) > inlen) {
         return CRYPT_INVALID_PACKET;
      }

      /* no so read it */
      if ((err = mp_read_unsigned_bin(num, (unsigned char *)in + x, y)) != CRYPT_OK) {
         return err;
      }
   }

   /* see if it's negative */
   if (in[x] & 0x80) {
      void *tmp;
      if (mp_init(&tmp) != CRYPT_OK) {
         return CRYPT_MEM;
      }

      if (mp_2expt(tmp, mp_count_bits(num)) != CRYPT_OK || mp_sub(num, tmp, num) != CRYPT_OK) {
         mp_clear(tmp);
         return CRYPT_MEM;
      }
      mp_clear(tmp);
   }

   return CRYPT_OK;

}

#endif

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