view libtomcrypt/src/modes/lrw/lrw_decrypt.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 lrw_decrypt.c
   LRW_MODE implementation, Decrypt blocks, Tom St Denis
*/

#ifdef LTC_LRW_MODE

/**
  LRW decrypt blocks
  @param ct     The ciphertext
  @param pt     [out] The plaintext
  @param len    The length in octets, must be a multiple of 16
  @param lrw    The LRW state
*/
int lrw_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_LRW *lrw)
{
   int err;

   LTC_ARGCHK(pt  != NULL);
   LTC_ARGCHK(ct  != NULL);
   LTC_ARGCHK(lrw != NULL);

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

   if (cipher_descriptor[lrw->cipher].accel_lrw_decrypt != NULL) {
      return cipher_descriptor[lrw->cipher].accel_lrw_decrypt(ct, pt, len, lrw->IV, lrw->tweak, &lrw->key);
   }

   return lrw_process(ct, pt, len, LRW_DECRYPT, lrw);
}


#endif

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