Mercurial > dropbear

annotate libtommath/bn_s_mp_balance_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:
rev   line source
1692
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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1 #include "tommath_private.h"
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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2 #ifdef BN_S_MP_BALANCE_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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5
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6 /* single-digit multiplication with the smaller number as the single-digit */
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7 mp_err s_mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c)
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8 {
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9 int count, len_a, len_b, nblocks, i, j, bsize;
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10 mp_int a0, tmp, A, B, r;
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11 mp_err err;
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12
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13 len_a = a->used;
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14 len_b = b->used;
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15
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16 nblocks = MP_MAX(a->used, b->used) / MP_MIN(a->used, b->used);
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17 bsize = MP_MIN(a->used, b->used) ;
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18
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19 if ((err = mp_init_size(&a0, bsize + 2)) != MP_OKAY) {
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20 return err;
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21 }
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22 if ((err = mp_init_multi(&tmp, &r, NULL)) != MP_OKAY) {
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23 mp_clear(&a0);
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24 return err;
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25 }
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26
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27 /* Make sure that A is the larger one*/
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28 if (len_a < len_b) {
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29 B = *a;
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30 A = *b;
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31 } else {
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32 A = *a;
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33 B = *b;
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34 }
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35
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36 for (i = 0, j=0; i < nblocks; i++) {
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37 /* Cut a slice off of a */
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38 a0.used = 0;
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39 for (count = 0; count < bsize; count++) {
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40 a0.dp[count] = A.dp[ j++ ];
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41 a0.used++;
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42 }
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43 mp_clamp(&a0);
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44 /* Multiply with b */
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45 if ((err = mp_mul(&a0, &B, &tmp)) != MP_OKAY) {
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46 goto LBL_ERR;
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47 }
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48 /* Shift tmp to the correct position */
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49 if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
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50 goto LBL_ERR;
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51 }
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52 /* Add to output. No carry needed */
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53 if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) {
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54 goto LBL_ERR;
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55 }
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56 }
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57 /* The left-overs; there are always left-overs */
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58 if (j < A.used) {
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59 a0.used = 0;
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60 for (count = 0; j < A.used; count++) {
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61 a0.dp[count] = A.dp[ j++ ];
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62 a0.used++;
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63 }
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64 mp_clamp(&a0);
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65 if ((err = mp_mul(&a0, &B, &tmp)) != MP_OKAY) {
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66 goto LBL_ERR;
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67 }
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68 if ((err = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
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69 goto LBL_ERR;
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70 }
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71 if ((err = mp_add(&r, &tmp, &r)) != MP_OKAY) {
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72 goto LBL_ERR;
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73 }
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74 }
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75
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76 mp_exch(&r,c);
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77 LBL_ERR:
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78 mp_clear_multi(&a0, &tmp, &r,NULL);
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79 return err;
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80 }
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81 #endif