annotate libtommath/bn_mp_and.c @ 1715:3974f087d9c0

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:
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_AND_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 /* two complement and */
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7 mp_err mp_and(const mp_int *a, const mp_int *b, mp_int *c)
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8 {
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9 int used = MP_MAX(a->used, b->used) + 1, i;
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10 mp_err err;
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11 mp_digit ac = 1, bc = 1, cc = 1;
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12 mp_sign csign = ((a->sign == MP_NEG) && (b->sign == MP_NEG)) ? MP_NEG : MP_ZPOS;
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13
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14 if (c->alloc < used) {
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15 if ((err = mp_grow(c, used)) != MP_OKAY) {
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16 return err;
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17 }
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18 }
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19
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20 for (i = 0; i < used; i++) {
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21 mp_digit x, y;
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22
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23 /* convert to two complement if negative */
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24 if (a->sign == MP_NEG) {
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25 ac += (i >= a->used) ? MP_MASK : (~a->dp[i] & MP_MASK);
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26 x = ac & MP_MASK;
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27 ac >>= MP_DIGIT_BIT;
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28 } else {
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29 x = (i >= a->used) ? 0uL : a->dp[i];
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30 }
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31
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32 /* convert to two complement if negative */
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33 if (b->sign == MP_NEG) {
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34 bc += (i >= b->used) ? MP_MASK : (~b->dp[i] & MP_MASK);
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35 y = bc & MP_MASK;
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36 bc >>= MP_DIGIT_BIT;
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37 } else {
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38 y = (i >= b->used) ? 0uL : b->dp[i];
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39 }
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40
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41 c->dp[i] = x & y;
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42
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43 /* convert to to sign-magnitude if negative */
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44 if (csign == MP_NEG) {
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45 cc += ~c->dp[i] & MP_MASK;
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46 c->dp[i] = cc & MP_MASK;
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47 cc >>= MP_DIGIT_BIT;
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48 }
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49 }
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50
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51 c->used = used;
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52 c->sign = csign;
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53 mp_clamp(c);
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54 return MP_OKAY;
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55 }
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56 #endif