Mercurial > dropbear

annotate libtommath/bn_mp_mul.c @ 1861:2b3a8026a6ce

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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
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_MUL_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
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4 /* SPDX-License-Identifier: Unlicense */
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6 /* high level multiplication (handles sign) */
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7 mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
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8 {
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9 mp_err err;
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10 int min_len = MP_MIN(a->used, b->used),
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11 max_len = MP_MAX(a->used, b->used),
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12 digs = a->used + b->used + 1;
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13 mp_sign neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
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14
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15 if (MP_HAS(S_MP_BALANCE_MUL) &&
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16 /* Check sizes. The smaller one needs to be larger than the Karatsuba cut-off.
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17 * The bigger one needs to be at least about one MP_KARATSUBA_MUL_CUTOFF bigger
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18 * to make some sense, but it depends on architecture, OS, position of the
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19 * stars... so YMMV.
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20 * Using it to cut the input into slices small enough for fast_s_mp_mul_digs
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21 * was actually slower on the author's machine, but YMMV.
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22 */
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23 (min_len >= MP_KARATSUBA_MUL_CUTOFF) &&
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24 ((max_len / 2) >= MP_KARATSUBA_MUL_CUTOFF) &&
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25 /* Not much effect was observed below a ratio of 1:2, but again: YMMV. */
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26 (max_len >= (2 * min_len))) {
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27 err = s_mp_balance_mul(a,b,c);
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28 } else if (MP_HAS(S_MP_TOOM_MUL) &&
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29 (min_len >= MP_TOOM_MUL_CUTOFF)) {
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30 err = s_mp_toom_mul(a, b, c);
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31 } else if (MP_HAS(S_MP_KARATSUBA_MUL) &&
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32 (min_len >= MP_KARATSUBA_MUL_CUTOFF)) {
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33 err = s_mp_karatsuba_mul(a, b, c);
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34 } else if (MP_HAS(S_MP_MUL_DIGS_FAST) &&
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35 /* can we use the fast multiplier?
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36 *
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37 * The fast multiplier can be used if the output will
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38 * have less than MP_WARRAY digits and the number of
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39 * digits won't affect carry propagation
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40 */
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41 (digs < MP_WARRAY) &&
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42 (min_len <= MP_MAXFAST)) {
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43 err = s_mp_mul_digs_fast(a, b, c, digs);
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44 } else if (MP_HAS(S_MP_MUL_DIGS)) {
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45 err = s_mp_mul_digs(a, b, c, digs);
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46 } else {
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47 err = MP_VAL;
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48 }
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49 c->sign = (c->used > 0) ? neg : MP_ZPOS;
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50 return err;
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51 }
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52 #endif