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annotate libtommath/bn_mp_mul.c @ 1930:299f4f19ba19

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Add /usr/sbin and /sbin to default root PATH When dropbear is used in a very restricted environment (such as in a initrd), the default user shell is often also very restricted and doesn't take care of setting the PATH so the user ends up with the PATH set by dropbear. Unfortunately, dropbear always sets "/usr/bin:/bin" as default PATH even for the root user which should have /usr/sbin and /sbin too. For a concrete instance of this problem, see the "Remote Unlocking" section in this tutorial: https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/ It speaks of a bug in the initramfs script because it's written "blkid" instead of "/sbin/blkid"... this is just because the scripts from the initramfs do not expect to have a PATH without the sbin directories and because dropbear is not setting the PATH appropriately for the root user. I'm thus suggesting to use the attached patch to fix this misbehaviour (I did not test it, but it's easy enough). It might seem anecdotic but multiple Kali users have been bitten by this. From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403
author Raphael Hertzog <hertzog@debian.org>
date Mon, 09 Jul 2018 16:27:53 +0200
parents 1051e4eea25a
children
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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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 /* SPDX-License-Identifier: Unlicense */
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6 /* high level multiplication (handles sign) */
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7 mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
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8 {
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9 mp_err err;
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10 int min_len = MP_MIN(a->used, b->used),
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11 max_len = MP_MAX(a->used, b->used),
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12 digs = a->used + b->used + 1;
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13 mp_sign neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
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14
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15 if (MP_HAS(S_MP_BALANCE_MUL) &&
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16 /* Check sizes. The smaller one needs to be larger than the Karatsuba cut-off.
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17 * The bigger one needs to be at least about one MP_KARATSUBA_MUL_CUTOFF bigger
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18 * to make some sense, but it depends on architecture, OS, position of the
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19 * stars... so YMMV.
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20 * Using it to cut the input into slices small enough for fast_s_mp_mul_digs
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21 * was actually slower on the author's machine, but YMMV.
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22 */
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23 (min_len >= MP_KARATSUBA_MUL_CUTOFF) &&
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24 ((max_len / 2) >= MP_KARATSUBA_MUL_CUTOFF) &&
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25 /* Not much effect was observed below a ratio of 1:2, but again: YMMV. */
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26 (max_len >= (2 * min_len))) {
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27 err = s_mp_balance_mul(a,b,c);
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28 } else if (MP_HAS(S_MP_TOOM_MUL) &&
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29 (min_len >= MP_TOOM_MUL_CUTOFF)) {
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30 err = s_mp_toom_mul(a, b, c);
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31 } else if (MP_HAS(S_MP_KARATSUBA_MUL) &&
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32 (min_len >= MP_KARATSUBA_MUL_CUTOFF)) {
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33 err = s_mp_karatsuba_mul(a, b, c);
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34 } else if (MP_HAS(S_MP_MUL_DIGS_FAST) &&
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35 /* can we use the fast multiplier?
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36 *
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37 * The fast multiplier can be used if the output will
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38 * have less than MP_WARRAY digits and the number of
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39 * digits won't affect carry propagation
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40 */
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41 (digs < MP_WARRAY) &&
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42 (min_len <= MP_MAXFAST)) {
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43 err = s_mp_mul_digs_fast(a, b, c, digs);
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44 } else if (MP_HAS(S_MP_MUL_DIGS)) {
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45 err = s_mp_mul_digs(a, b, c, digs);
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46 } else {
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47 err = MP_VAL;
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48 }
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49 c->sign = (c->used > 0) ? neg : MP_ZPOS;
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50 return err;
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51 }
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52 #endif