Mercurial > dropbear

annotate libtommath/bn_mp_mul.c @ 1715:3974f087d9c0

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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
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
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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