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

#include "tommath_private.h"
#ifdef BN_MP_REDUCE_IS_2K_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */

/* determines if mp_reduce_2k can be used */
mp_bool mp_reduce_is_2k(const mp_int *a)
{
   int ix, iy, iw;
   mp_digit iz;

   if (a->used == 0) {
      return MP_NO;
   } else if (a->used == 1) {
      return MP_YES;
   } else if (a->used > 1) {
      iy = mp_count_bits(a);
      iz = 1;
      iw = 1;

      /* Test every bit from the second digit up, must be 1 */
      for (ix = MP_DIGIT_BIT; ix < iy; ix++) {
         if ((a->dp[iw] & iz) == 0u) {
            return MP_NO;
         }
         iz <<= 1;
         if (iz > MP_DIGIT_MAX) {
            ++iw;
            iz = 1;
         }
      }
      return MP_YES;
   } else {
      return MP_YES;
   }
}

#endif