view libtomcrypt/src/prngs/sprng.c @ 1861:2b3a8026a6ce

Add re-exec for server This allows ASLR to re-randomize the address space for every connection, preventing some vulnerabilities from being exploitable by repeated probing. Overhead (memory and time) is yet to be confirmed. At present this is only enabled on Linux. Other BSD platforms with fexecve() would probably also work though have not been tested.
author Matt Johnston <matt@ucc.asn.au>
date Sun, 30 Jan 2022 10:14:56 +0800
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 sprng.c
   Secure PRNG, Tom St Denis
*/

/* A secure PRNG using the RNG functions.  Basically this is a
 * wrapper that allows you to use a secure RNG as a PRNG
 * in the various other functions.
 */

#ifdef LTC_SPRNG

const struct ltc_prng_descriptor sprng_desc =
{
    "sprng", 0,
    &sprng_start,
    &sprng_add_entropy,
    &sprng_ready,
    &sprng_read,
    &sprng_done,
    &sprng_export,
    &sprng_import,
    &sprng_test
};

/**
  Start the PRNG
  @param prng     [out] The PRNG state to initialize
  @return CRYPT_OK if successful
*/
int sprng_start(prng_state *prng)
{
   LTC_UNUSED_PARAM(prng);
   return CRYPT_OK;
}

/**
  Add entropy to the PRNG state
  @param in       The data to add
  @param inlen    Length of the data to add
  @param prng     PRNG state to update
  @return CRYPT_OK if successful
*/
int sprng_add_entropy(const unsigned char *in, unsigned long inlen, prng_state *prng)
{
   LTC_UNUSED_PARAM(in);
   LTC_UNUSED_PARAM(inlen);
   LTC_UNUSED_PARAM(prng);
   return CRYPT_OK;
}

/**
  Make the PRNG ready to read from
  @param prng   The PRNG to make active
  @return CRYPT_OK if successful
*/
int sprng_ready(prng_state *prng)
{
   LTC_UNUSED_PARAM(prng);
   return CRYPT_OK;
}

/**
  Read from the PRNG
  @param out      Destination
  @param outlen   Length of output
  @param prng     The active PRNG to read from
  @return Number of octets read
*/
unsigned long sprng_read(unsigned char *out, unsigned long outlen, prng_state *prng)
{
   LTC_ARGCHK(out != NULL);
   LTC_UNUSED_PARAM(prng);
   return rng_get_bytes(out, outlen, NULL);
}

/**
  Terminate the PRNG
  @param prng   The PRNG to terminate
  @return CRYPT_OK if successful
*/
int sprng_done(prng_state *prng)
{
   LTC_UNUSED_PARAM(prng);
   return CRYPT_OK;
}

/**
  Export the PRNG state
  @param out       [out] Destination
  @param outlen    [in/out] Max size and resulting size of the state
  @param prng      The PRNG to export
  @return CRYPT_OK if successful
*/
int sprng_export(unsigned char *out, unsigned long *outlen, prng_state *prng)
{
   LTC_ARGCHK(outlen != NULL);
   LTC_UNUSED_PARAM(out);
   LTC_UNUSED_PARAM(prng);

   *outlen = 0;
   return CRYPT_OK;
}

/**
  Import a PRNG state
  @param in       The PRNG state
  @param inlen    Size of the state
  @param prng     The PRNG to import
  @return CRYPT_OK if successful
*/
int sprng_import(const unsigned char *in, unsigned long inlen, prng_state *prng)
{
  LTC_UNUSED_PARAM(in);
  LTC_UNUSED_PARAM(inlen);
  LTC_UNUSED_PARAM(prng);
   return CRYPT_OK;
}

/**
  PRNG self-test
  @return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled
*/
int sprng_test(void)
{
#ifndef LTC_TEST
   return CRYPT_NOP;
#else
   prng_state st;
   unsigned char en[] = { 0x01, 0x02, 0x03, 0x04 };
   unsigned char out[1000];
   int err;

   if ((err = sprng_start(&st)) != CRYPT_OK)                         return err;
   if ((err = sprng_add_entropy(en, sizeof(en), &st)) != CRYPT_OK)   return err;
   if ((err = sprng_ready(&st)) != CRYPT_OK)                         return err;
   if (sprng_read(out, 500, &st) != 500)                             return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
   if ((err = sprng_done(&st)) != CRYPT_OK)                          return err;

   return CRYPT_OK;
#endif
}

#endif




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