Mercurial > dropbear

annotate libtommath/bn_mp_gcd.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
1655
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
diff changeset
1 #include "tommath_private.h"
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diff changeset
2 #ifdef BN_MP_GCD_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 /* Greatest Common Divisor using the binary method */
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1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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7 mp_err mp_gcd(const mp_int *a, const mp_int *b, mp_int *c)
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diff changeset
8 {
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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diff changeset
9 mp_int u, v;
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10 int k, u_lsb, v_lsb;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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diff changeset
11 mp_err err;
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12
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parents: 1470
diff changeset
13 /* either zero than gcd is the largest */
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1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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14 if (MP_IS_ZERO(a)) {
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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15 return mp_abs(b, c);
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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16 }
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17 if (MP_IS_ZERO(b)) {
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18 return mp_abs(a, c);
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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19 }
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20
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21 /* get copies of a and b we can modify */
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22 if ((err = mp_init_copy(&u, a)) != MP_OKAY) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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23 return err;
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24 }
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25
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26 if ((err = mp_init_copy(&v, b)) != MP_OKAY) {
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27 goto LBL_U;
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28 }
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29
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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30 /* must be positive for the remainder of the algorithm */
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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31 u.sign = v.sign = MP_ZPOS;
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32
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diff changeset
33 /* B1. Find the common power of two for u and v */
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34 u_lsb = mp_cnt_lsb(&u);
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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35 v_lsb = mp_cnt_lsb(&v);
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36 k = MP_MIN(u_lsb, v_lsb);
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37
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38 if (k > 0) {
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39 /* divide the power of two out */
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40 if ((err = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) {
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41 goto LBL_V;
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42 }
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43
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44 if ((err = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) {
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parents: 1470
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45 goto LBL_V;
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parents: 1470
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46 }
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
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47 }
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48
1655
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diff changeset
49 /* divide any remaining factors of two out */
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parents: 1470
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50 if (u_lsb != k) {
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51 if ((err = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) {
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parents: 1470
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52 goto LBL_V;
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parents: 1470
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53 }
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
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54 }
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55
1655
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diff changeset
56 if (v_lsb != k) {
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57 if ((err = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) {
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parents: 1470
diff changeset
58 goto LBL_V;
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parents: 1470
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59 }
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
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60 }
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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61
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62 while (!MP_IS_ZERO(&v)) {
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diff changeset
63 /* make sure v is the largest */
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64 if (mp_cmp_mag(&u, &v) == MP_GT) {
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65 /* swap u and v to make sure v is >= u */
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66 mp_exch(&u, &v);
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
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67 }
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68
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69 /* subtract smallest from largest */
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70 if ((err = s_mp_sub(&v, &u, &v)) != MP_OKAY) {
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71 goto LBL_V;
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parents: 1470
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72 }
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parents: 1470
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73
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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74 /* Divide out all factors of two */
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75 if ((err = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) {
1655
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parents: 1470
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76 goto LBL_V;
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parents: 1470
diff changeset
77 }
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
diff changeset
78 }
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79
1655
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diff changeset
80 /* multiply by 2**k which we divided out at the beginning */
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parents: 1655
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81 if ((err = mp_mul_2d(&u, k, c)) != MP_OKAY) {
1655
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
diff changeset
82 goto LBL_V;
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parents: 1470
diff changeset
83 }
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
diff changeset
84 c->sign = MP_ZPOS;
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diff changeset
85 err = MP_OKAY;
1655
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
diff changeset
86 LBL_V:
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parents: 1470
diff changeset
87 mp_clear(&u);
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
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88 LBL_U:
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Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
diff changeset
89 mp_clear(&v);
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diff changeset
90 return err;
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91 }
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parents:
diff changeset
92 #endif