Mercurial > dropbear
view libtommath/bn_s_mp_balance_mul.c @ 1861:2b3a8026a6ce
Add re-exec for server
This allows ASLR to re-randomize the address
space for every connection, preventing some
vulnerabilities from being exploitable by
repeated probing.
Overhead (memory and time) is yet to be confirmed.
At present this is only enabled on Linux. Other BSD platforms
with fexecve() would probably also work though have not been tested.
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Sun, 30 Jan 2022 10:14:56 +0800 |
parents | 1051e4eea25a |
children |
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#include "tommath_private.h" #ifdef BN_S_MP_BALANCE_MUL_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* single-digit multiplication with the smaller number as the single-digit */ mp_err s_mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c) { int count, len_a, len_b, nblocks, i, j, bsize; mp_int a0, tmp, A, B, r; mp_err err; len_a = a->used; len_b = b->used; nblocks = MP_MAX(a->used, b->used) / MP_MIN(a->used, b->used); bsize = MP_MIN(a->used, b->used) ; if ((err = mp_init_size(&a0, bsize + 2)) != MP_OKAY) { return err; } if ((err = mp_init_multi(&tmp, &r, NULL)) != MP_OKAY) { mp_clear(&a0); return err; } /* Make sure that A is the larger one*/ if (len_a < len_b) { B = *a; A = *b; } else { A = *a; B = *b; } for (i = 0, j=0; i < nblocks; i++) { /* Cut a slice off of a */ a0.used = 0; for (count = 0; count < bsize; count++) { a0.dp[count] = A.dp[ j++ ]; a0.used++; } mp_clamp(&a0); /* Multiply with b */ if ((err = mp_mul(&a0, &B, &tmp)) != MP_OKAY) { goto LBL_ERR; } /* Shift tmp to the correct position */ if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) { goto LBL_ERR; } /* Add to output. No carry needed */ if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) { goto LBL_ERR; } } /* The left-overs; there are always left-overs */ if (j < A.used) { a0.used = 0; for (count = 0; j < A.used; count++) { a0.dp[count] = A.dp[ j++ ]; a0.used++; } mp_clamp(&a0); if ((err = mp_mul(&a0, &B, &tmp)) != MP_OKAY) { goto LBL_ERR; } if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) { goto LBL_ERR; } if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) { goto LBL_ERR; } } mp_exch(&r,c); LBL_ERR: mp_clear_multi(&a0, &tmp, &r,NULL); return err; } #endif