Mercurial > dropbear
view libtommath/bn_s_mp_prime_is_divisible.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 | 1051e4eea25a |
children |
line wrap: on
line source
#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