view libtomcrypt/src/pk/rsa/rsa_sign_saltlen_get.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 rsa_sign_saltlen_get.c
  Retrieve the maximum size of the salt, Steffen Jaeckel.
*/

#ifdef LTC_MRSA

/**
  Retrieve the maximum possible size of the salt when creating a PKCS#1 PSS signature.
  @param padding    Type of padding (LTC_PKCS_1_PSS only)
  @param hash_idx   The index of the desired hash
  @param key        The RSA key
  @return The maximum salt length in bytes or INT_MAX on error.
*/
int rsa_sign_saltlen_get_max_ex(int padding, int hash_idx, rsa_key *key)
{
  int ret = INT_MAX;
  LTC_ARGCHK(key != NULL);

  if ((hash_is_valid(hash_idx) == CRYPT_OK) &&
      (padding == LTC_PKCS_1_PSS))
  {
    ret = rsa_get_size(key);
    if (ret < INT_MAX)
    {
      ret -= (hash_descriptor[hash_idx].hashsize + 2);
    } /* if */
  } /* if */

  return ret;
}

#endif

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