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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 d885a77b98e0
children
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */
#include "tomcrypt.h"

/**
  @file base64_decode.c
  Compliant base64 code donated by Wayne Scott ([email protected])
  base64 URL Safe variant (RFC 4648 section 5) by Karel Miko
*/


#if defined(LTC_BASE64) || defined (LTC_BASE64_URL)

#if defined(LTC_BASE64)
static const unsigned char map_base64[256] = {
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255,  62, 255, 255, 255,  63,
 52,  53,  54,  55,  56,  57,  58,  59,  60,  61, 255, 255,
255, 254, 255, 255, 255,   0,   1,   2,   3,   4,   5,   6,
  7,   8,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18,
 19,  20,  21,  22,  23,  24,  25, 255, 255, 255, 255, 255,
255,  26,  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,
 37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,  48,
 49,  50,  51, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255 };
#endif /* LTC_BASE64 */

#if defined(LTC_BASE64_URL)
static const unsigned char map_base64url[] = {
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255,  62, 255, 255,
 52,  53,  54,  55,  56,  57,  58,  59,  60,  61, 255, 255,
255, 254, 255, 255, 255,   0,   1,   2,   3,   4,   5,   6,
  7,   8,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18,
 19,  20,  21,  22,  23,  24,  25, 255, 255, 255, 255,  63,
255,  26,  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,
 37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,  48,
 49,  50,  51, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255
};
#endif /* LTC_BASE64_URL */

enum {
   relaxed = 0,
   strict = 1
};

static int _base64_decode_internal(const unsigned char *in,  unsigned long inlen,
                                 unsigned char *out, unsigned long *outlen,
                           const unsigned char *map, int is_strict)
{
   unsigned long t, x, y, z;
   unsigned char c;
   int           g;

   LTC_ARGCHK(in     != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(outlen != NULL);

   g = 0; /* '=' counter */
   for (x = y = z = t = 0; x < inlen; x++) {
       c = map[in[x]&0xFF];
       if (c == 254) {
          g++;
          continue;
       }
       else if (is_strict && g > 0) {
          /* we only allow '=' to be at the end */
          return CRYPT_INVALID_PACKET;
       }
       if (c == 255) {
          if (is_strict)
             return CRYPT_INVALID_PACKET;
          else
             continue;
       }

       t = (t<<6)|c;

       if (++y == 4) {
          if (z + 3 > *outlen) return CRYPT_BUFFER_OVERFLOW;
          out[z++] = (unsigned char)((t>>16)&255);
          out[z++] = (unsigned char)((t>>8)&255);
          out[z++] = (unsigned char)(t&255);
          y = t = 0;
       }
   }

   if (y != 0) {
      int allow_b64url = 0;
#ifdef LTC_BASE64_URL
      if (map == map_base64url) {
        allow_b64url = 1;
      }
#endif
      if (y == 1) return CRYPT_INVALID_PACKET;
      if ((y + g) != 4 && is_strict && !allow_b64url) return CRYPT_INVALID_PACKET;
      t = t << (6 * (4 - y));
      if (z + y - 1 > *outlen) return CRYPT_BUFFER_OVERFLOW;
      if (y >= 2) out[z++] = (unsigned char) ((t >> 16) & 255);
      if (y == 3) out[z++] = (unsigned char) ((t >> 8) & 255);
   }
   *outlen = z;
   return CRYPT_OK;
}

#if defined(LTC_BASE64)
/**
   Relaxed base64 decode a block of memory
   @param in       The base64 data to decode
   @param inlen    The length of the base64 data
   @param out      [out] The destination of the binary decoded data
   @param outlen   [in/out] The max size and resulting size of the decoded data
   @return CRYPT_OK if successful
*/
int base64_decode(const unsigned char *in,  unsigned long inlen,
                        unsigned char *out, unsigned long *outlen)
{
    return _base64_decode_internal(in, inlen, out, outlen, map_base64, relaxed);
}

/**
   Strict base64 decode a block of memory
   @param in       The base64 data to decode
   @param inlen    The length of the base64 data
   @param out      [out] The destination of the binary decoded data
   @param outlen   [in/out] The max size and resulting size of the decoded data
   @return CRYPT_OK if successful
*/
int base64_strict_decode(const unsigned char *in,  unsigned long inlen,
                        unsigned char *out, unsigned long *outlen)
{
   return _base64_decode_internal(in, inlen, out, outlen, map_base64, strict);
}
#endif /* LTC_BASE64 */

#if defined(LTC_BASE64_URL)
/**
   Relaxed base64 (URL Safe, RFC 4648 section 5) decode a block of memory
   @param in       The base64 data to decode
   @param inlen    The length of the base64 data
   @param out      [out] The destination of the binary decoded data
   @param outlen   [in/out] The max size and resulting size of the decoded data
   @return CRYPT_OK if successful
*/
int base64url_decode(const unsigned char *in,  unsigned long inlen,
                           unsigned char *out, unsigned long *outlen)
{
    return _base64_decode_internal(in, inlen, out, outlen, map_base64url, relaxed);
}

/**
   Strict base64 (URL Safe, RFC 4648 section 5) decode a block of memory
   @param in       The base64 data to decode
   @param inlen    The length of the base64 data
   @param out      [out] The destination of the binary decoded data
   @param outlen   [in/out] The max size and resulting size of the decoded data
   @return CRYPT_OK if successful
*/
int base64url_strict_decode(const unsigned char *in,  unsigned long inlen,
                           unsigned char *out, unsigned long *outlen)
{
    return _base64_decode_internal(in, inlen, out, outlen, map_base64url, strict);
}
#endif /* LTC_BASE64_URL */

#endif


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