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annotate libtommath/bn_mp_mul.c @ 1669:3080aed32bf1

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scp.c: Port OpenSSH CVE-2018-20685 fix (#80)
author Haelwenn Monnier <contact+github.com@hacktivis.me>
date Mon, 25 May 2020 14:54:29 +0200
parents f52919ffd3b1
children 1051e4eea25a
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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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 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * SPDX-License-Identifier: Unlicense
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13 */
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14
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15 /* high level multiplication (handles sign) */
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16 int mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
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17 {
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18 int res, neg;
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19 neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
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20
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21 /* use Toom-Cook? */
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22 #ifdef BN_MP_TOOM_MUL_C
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23 if (MIN(a->used, b->used) >= TOOM_MUL_CUTOFF) {
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24 res = mp_toom_mul(a, b, c);
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25 } else
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26 #endif
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27 #ifdef BN_MP_KARATSUBA_MUL_C
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28 /* use Karatsuba? */
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29 if (MIN(a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
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30 res = mp_karatsuba_mul(a, b, c);
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31 } else
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32 #endif
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33 {
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34 /* can we use the fast multiplier?
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35 *
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36 * The fast multiplier can be used if the output will
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37 * have less than MP_WARRAY digits and the number of
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38 * digits won't affect carry propagation
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39 */
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40 int digs = a->used + b->used + 1;
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41
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42 #ifdef BN_FAST_S_MP_MUL_DIGS_C
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43 if ((digs < (int)MP_WARRAY) &&
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44 (MIN(a->used, b->used) <=
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45 (int)(1u << (((size_t)CHAR_BIT * sizeof(mp_word)) - (2u * (size_t)DIGIT_BIT))))) {
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46 res = fast_s_mp_mul_digs(a, b, c, digs);
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47 } else
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48 #endif
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49 {
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50 #ifdef BN_S_MP_MUL_DIGS_C
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51 res = s_mp_mul(a, b, c); /* uses s_mp_mul_digs */
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52 #else
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53 res = MP_VAL;
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54 #endif
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55 }
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56 }
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57 c->sign = (c->used > 0) ? neg : MP_ZPOS;
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58 return res;
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59 }
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60 #endif
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61
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62 /* ref: HEAD -> master, tag: v1.1.0 */
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63 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
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64 /* commit time: 2019-01-28 20:32:32 +0100 */