view libtommath/bn_s_mp_prime_is_divisible.c @ 1715:3974f087d9c0

Disallow leading lines before the ident for server (#102) Per RFC4253 4.2 clients must be able to process other lines of data before the version string, server behavior is not defined neither with MUST/SHOULD nor with MAY. If server process up to 50 lines too - it may cause too long hanging session with invalid/evil client that consume host resources and potentially may lead to DDoS on poor embedded boxes. Let's require first line from client to be version string and fail early if it's not - matches both RFC and real OpenSSH behavior.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 15 Jun 2020 18:22:18 +0500
parents 1051e4eea25a
children
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#include "tommath_private.h"
#ifdef BN_S_MP_PRIME_IS_DIVISIBLE_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */

/* determines if an integers is divisible by one
 * of the first PRIME_SIZE primes or not
 *
 * sets result to 0 if not, 1 if yes
 */
mp_err s_mp_prime_is_divisible(const mp_int *a, mp_bool *result)
{
   int      ix;
   mp_err   err;
   mp_digit res;

   /* default to not */
   *result = MP_NO;

   for (ix = 0; ix < PRIVATE_MP_PRIME_TAB_SIZE; ix++) {
      /* what is a mod LBL_prime_tab[ix] */
      if ((err = mp_mod_d(a, s_mp_prime_tab[ix], &res)) != MP_OKAY) {
         return err;
      }

      /* is the residue zero? */
      if (res == 0u) {
         *result = MP_YES;
         return MP_OKAY;
      }
   }

   return MP_OKAY;
}
#endif