view libtomcrypt/src/mac/f9/f9_process.c @ 1790:42745af83b7d

Introduce extra delay before closing unauthenticated sessions To make it harder for attackers, introduce a delay to keep an unauthenticated session open a bit longer, thus blocking a connection slot until after the delay. Without this, while there is a limit on the amount of attempts an attacker can make at the same time (MAX_UNAUTH_PER_IP), the time taken by dropbear to handle one attempt is still short and thus for each of the allowed parallel attempts many attempts can be chained one after the other. The attempt rate is then: "MAX_UNAUTH_PER_IP / <process time of one attempt>". With the delay, this rate becomes: "MAX_UNAUTH_PER_IP / UNAUTH_CLOSE_DELAY".
author Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
date Wed, 15 Feb 2017 13:53:04 +0100
parents 6dba84798cd5
children
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/* 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 f9_process.c
  f9 Support, process blocks with f9
*/

#ifdef LTC_F9_MODE

/** Process data through f9-MAC
  @param f9       The f9-MAC state
  @param in       Input data to process
  @param inlen    Length of input in octets
  Return CRYPT_OK on success
*/
int f9_process(f9_state *f9, const unsigned char *in, unsigned long inlen)
{
   int err, x;

   LTC_ARGCHK(f9 != NULL);
   LTC_ARGCHK(in   != NULL);

   /* check structure */
   if ((err = cipher_is_valid(f9->cipher)) != CRYPT_OK) {
      return err;
   }

   if ((f9->blocksize > cipher_descriptor[f9->cipher].block_length) || (f9->blocksize < 0) ||
       (f9->buflen > f9->blocksize) || (f9->buflen < 0)) {
      return CRYPT_INVALID_ARG;
   }

#ifdef LTC_FAST
   if (f9->buflen == 0) {
       while (inlen >= (unsigned long)f9->blocksize) {
           for (x = 0; x < f9->blocksize; x += sizeof(LTC_FAST_TYPE)) {
              *(LTC_FAST_TYPE_PTR_CAST(&(f9->IV[x]))) ^= *(LTC_FAST_TYPE_PTR_CAST(&(in[x])));
           }
           cipher_descriptor[f9->cipher].ecb_encrypt(f9->IV, f9->IV, &f9->key);
           for (x = 0; x < f9->blocksize; x += sizeof(LTC_FAST_TYPE)) {
              *(LTC_FAST_TYPE_PTR_CAST(&(f9->ACC[x]))) ^= *(LTC_FAST_TYPE_PTR_CAST(&(f9->IV[x])));
           }
           in    += f9->blocksize;
           inlen -= f9->blocksize;
       }
   }
#endif

   while (inlen) {
      if (f9->buflen == f9->blocksize) {
         cipher_descriptor[f9->cipher].ecb_encrypt(f9->IV, f9->IV, &f9->key);
         for (x = 0; x < f9->blocksize; x++) {
            f9->ACC[x] ^= f9->IV[x];
         }
         f9->buflen = 0;
      }
      f9->IV[f9->buflen++] ^= *in++;
      --inlen;
   }
   return CRYPT_OK;
}

#endif

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