Mercurial > dropbear

annotate libtommath/bn_mp_expt_u32.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
1692
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_EXPT_U32_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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5
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6 /* calculate c = a**b using a square-multiply algorithm */
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7 mp_err mp_expt_u32(const mp_int *a, uint32_t b, mp_int *c)
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8 {
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9 mp_err err;
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10
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11 mp_int g;
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12
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13 if ((err = mp_init_copy(&g, a)) != MP_OKAY) {
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14 return err;
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15 }
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16
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17 /* set initial result */
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18 mp_set(c, 1uL);
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19
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20 while (b > 0u) {
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21 /* if the bit is set multiply */
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22 if ((b & 1u) != 0u) {
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23 if ((err = mp_mul(c, &g, c)) != MP_OKAY) {
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24 goto LBL_ERR;
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25 }
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26 }
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27
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28 /* square */
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29 if (b > 1u) {
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30 if ((err = mp_sqr(&g, &g)) != MP_OKAY) {
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31 goto LBL_ERR;
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32 }
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33 }
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34
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35 /* shift to next bit */
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36 b >>= 1;
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37 }
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38
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39 err = MP_OKAY;
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40
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41 LBL_ERR:
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42 mp_clear(&g);
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43 return err;
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44 }
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45
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46 #endif