view libtomcrypt/src/math/radix_to_bin.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 radix_to_bin.c
   Convert data from a specific radix to binary.
   Steffen Jaeckel
*/

/**
   Convert data from a specific radix to binary

      The default MPI descriptors #ltm_desc, #tfm_desc and #gmp_desc
      have the following restrictions on parameters:

        \p in    - NUL-terminated char buffer

        \p radix - 2..64

   @param in    The input
   @param radix The radix of the input
   @param out   The output buffer
   @param len   [in/out] The length of the output buffer

   @return CRYPT_OK on success.
*/
int radix_to_bin(const void *in, int radix, void *out, unsigned long *len)
{
   unsigned long l;
   void* mpi;
   int err;

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

   if ((err = mp_init(&mpi)) != CRYPT_OK) return err;
   if ((err = mp_read_radix(mpi, in, radix)) != CRYPT_OK) goto LBL_ERR;

   if ((l = mp_unsigned_bin_size(mpi)) > *len) {
      *len = l;
      err = CRYPT_BUFFER_OVERFLOW;
      goto LBL_ERR;
   }
   *len = l;

   if ((err = mp_to_unsigned_bin(mpi, out)) != CRYPT_OK) goto LBL_ERR;

LBL_ERR:
   mp_clear(mpi);
   return err;
}

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