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annotate libtommath/bn_mp_lshd.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_LSHD_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 /* shift left a certain amount of digits */
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7 mp_err mp_lshd(mp_int *a, int b)
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8 {
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9 int x;
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10 mp_err err;
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11 mp_digit *top, *bottom;
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12
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13 /* if its less than zero return */
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14 if (b <= 0) {
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15 return MP_OKAY;
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16 }
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17 /* no need to shift 0 around */
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18 if (MP_IS_ZERO(a)) {
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19 return MP_OKAY;
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20 }
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21
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22 /* grow to fit the new digits */
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23 if (a->alloc < (a->used + b)) {
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24 if ((err = mp_grow(a, a->used + b)) != MP_OKAY) {
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25 return err;
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26 }
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27 }
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29 /* increment the used by the shift amount then copy upwards */
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30 a->used += b;
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31
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32 /* top */
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33 top = a->dp + a->used - 1;
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34
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35 /* base */
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36 bottom = (a->dp + a->used - 1) - b;
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37
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38 /* much like mp_rshd this is implemented using a sliding window
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39 * except the window goes the otherway around. Copying from
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40 * the bottom to the top. see bn_mp_rshd.c for more info.
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41 */
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42 for (x = a->used - 1; x >= b; x--) {
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43 *top-- = *bottom--;
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44 }
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45
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46 /* zero the lower digits */
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47 MP_ZERO_DIGITS(a->dp, b);
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48
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49 return MP_OKAY;
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50 }
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51 #endif