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_bit_string.c
  ASN.1 DER, encode a BIT STRING, Tom St Denis
*/


#ifdef LTC_DER

/**
  Store a BIT STRING
  @param in      The DER encoded BIT STRING
  @param inlen   The size of the DER BIT STRING
  @param out     [out] The array of bits stored (one per char)
  @param outlen  [in/out] The number of bits stored
  @return CRYPT_OK if successful
*/
int der_decode_bit_string(const unsigned char *in,  unsigned long inlen,
                                unsigned char *out, unsigned long *outlen)
{
   unsigned long dlen, blen, x, y;

   LTC_ARGCHK(in     != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(outlen != NULL);

   /* packet must be at least 4 bytes */
   if (inlen < 4) {
       return CRYPT_INVALID_ARG;
   }

   /* check for 0x03 */
   if ((in[0]&0x1F) != 0x03) {
      return CRYPT_INVALID_PACKET;
   }

   /* offset in the data */
   x = 1;

   /* get the length of the data */
   if (in[x] & 0x80) {
      /* long format get number of length bytes */
      y = in[x++] & 0x7F;

      /* invalid if 0 or > 2 */
      if (y == 0 || y > 2) {
         return CRYPT_INVALID_PACKET;
      }

      /* read the data len */
      dlen = 0;
      while (y--) {
         dlen = (dlen << 8) | (unsigned long)in[x++];
      }
   } else {
      /* short format */
      dlen = in[x++] & 0x7F;
   }

   /* is the data len too long or too short? */
   if ((dlen == 0) || (dlen + x > inlen)) {
       return CRYPT_INVALID_PACKET;
   }

   /* get padding count */
   blen = ((dlen - 1) << 3) - (in[x++] & 7);

   /* too many bits? */
   if (blen > *outlen) {
      *outlen = blen;
      return CRYPT_BUFFER_OVERFLOW;
   }

   /* decode/store the bits */
   for (y = 0; y < blen; y++) {
       out[y] = (in[x] & (1 << (7 - (y & 7)))) ? 1 : 0;
       if ((y & 7) == 7) {
          ++x;
       }
   }

   /* we done */
   *outlen = blen;
   return CRYPT_OK;
}

#endif

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