view libtomcrypt/src/pk/rsa/rsa_sign_saltlen_get.c @ 1930:299f4f19ba19

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 6dba84798cd5
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 rsa_sign_saltlen_get.c
  Retrieve the maximum size of the salt, Steffen Jaeckel.
*/

#ifdef LTC_MRSA

/**
  Retrieve the maximum possible size of the salt when creating a PKCS#1 PSS signature.
  @param padding    Type of padding (LTC_PKCS_1_PSS only)
  @param hash_idx   The index of the desired hash
  @param key        The RSA key
  @return The maximum salt length in bytes or INT_MAX on error.
*/
int rsa_sign_saltlen_get_max_ex(int padding, int hash_idx, rsa_key *key)
{
  int ret = INT_MAX;
  LTC_ARGCHK(key != NULL);

  if ((hash_is_valid(hash_idx) == CRYPT_OK) &&
      (padding == LTC_PKCS_1_PSS))
  {
    ret = rsa_get_size(key);
    if (ret < INT_MAX)
    {
      ret -= (hash_descriptor[hash_idx].hashsize + 2);
    } /* if */
  } /* if */

  return ret;
}

#endif

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