view libtomcrypt/src/prngs/fortuna.c @ 1156:a8f4dade70e5

avoid getpass when not used some systems (like android's bionic) do not provide getpass. you can disable ENABLE_CLI_PASSWORD_AUTH & ENABLE_CLI_INTERACT_AUTH to avoid its use (and rely on pubkey auth), but the link still fails because the support file calls getpass. do not define this func if both of those auth methods are not used.
author Mike Frysinger <vapier@gentoo.org>
date Wed, 21 Oct 2015 22:39:55 +0800
parents 0cbe8f6dbf9e
children f849a5ca2efc
line wrap: on
line source

/* 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.
 *
 * Tom St Denis, [email protected], http://libtomcrypt.com
 */
#include "tomcrypt.h"

/**
  @file fortuna.c
  Fortuna PRNG, Tom St Denis
*/
  
/* Implementation of Fortuna by Tom St Denis 

We deviate slightly here for reasons of simplicity [and to fit in the API].  First all "sources"
in the AddEntropy function are fixed to 0.  Second since no reliable timer is provided 
we reseed automatically when len(pool0) >= 64 or every FORTUNA_WD calls to the read function */

#ifdef FORTUNA 

/* requries SHA256 and AES  */
#if !(defined(RIJNDAEL) && defined(SHA256))
   #error FORTUNA requires SHA256 and RIJNDAEL (AES)
#endif

#ifndef FORTUNA_POOLS
   #warning FORTUNA_POOLS was not previously defined (old headers?)
   #define FORTUNA_POOLS 32
#endif

#if FORTUNA_POOLS < 4 || FORTUNA_POOLS > 32
   #error FORTUNA_POOLS must be in [4..32]
#endif

const struct ltc_prng_descriptor fortuna_desc = {
    "fortuna", 1024,
    &fortuna_start,
    &fortuna_add_entropy,
    &fortuna_ready,
    &fortuna_read,
    &fortuna_done,
    &fortuna_export,
    &fortuna_import,
    &fortuna_test
};

/* update the IV */
static void fortuna_update_iv(prng_state *prng)
{
   int            x;
   unsigned char *IV;
   /* update IV */
   IV = prng->fortuna.IV;
   for (x = 0; x < 16; x++) {
      IV[x] = (IV[x] + 1) & 255;
      if (IV[x] != 0) break;
   }
}

/* reseed the PRNG */
static int fortuna_reseed(prng_state *prng)
{
   unsigned char tmp[MAXBLOCKSIZE];
   hash_state    md;
   int           err, x;

   ++prng->fortuna.reset_cnt;

   /* new K == SHA256(K || s) where s == SHA256(P0) || SHA256(P1) ... */
   sha256_init(&md);
   if ((err = sha256_process(&md, prng->fortuna.K, 32)) != CRYPT_OK) {
      sha256_done(&md, tmp);
      return err;
   }

   for (x = 0; x < FORTUNA_POOLS; x++) {
       if (x == 0 || ((prng->fortuna.reset_cnt >> (x-1)) & 1) == 0) { 
          /* terminate this hash */
          if ((err = sha256_done(&prng->fortuna.pool[x], tmp)) != CRYPT_OK) {
             sha256_done(&md, tmp);
             return err; 
          }
          /* add it to the string */
          if ((err = sha256_process(&md, tmp, 32)) != CRYPT_OK) {
             sha256_done(&md, tmp);
             return err;
          }
          /* reset this pool */
          if ((err = sha256_init(&prng->fortuna.pool[x])) != CRYPT_OK) {
             sha256_done(&md, tmp);
             return err;
          }
       } else {
          break;
       }
   }

   /* finish key */
   if ((err = sha256_done(&md, prng->fortuna.K)) != CRYPT_OK) {
      return err; 
   }
   if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) {
      return err;
   }
   fortuna_update_iv(prng);

   /* reset pool len */
   prng->fortuna.pool0_len = 0;
   prng->fortuna.wd        = 0;


#ifdef LTC_CLEAN_STACK
   zeromem(&md, sizeof(md));
   zeromem(tmp, sizeof(tmp));
#endif

   return CRYPT_OK;
}

/**
  Start the PRNG
  @param prng     [out] The PRNG state to initialize
  @return CRYPT_OK if successful
*/  
int fortuna_start(prng_state *prng)
{
   int err, x, y;
   unsigned char tmp[MAXBLOCKSIZE];

   LTC_ARGCHK(prng != NULL);
   
   /* initialize the pools */
   for (x = 0; x < FORTUNA_POOLS; x++) {
       if ((err = sha256_init(&prng->fortuna.pool[x])) != CRYPT_OK) {
          for (y = 0; y < x; y++) {
              sha256_done(&prng->fortuna.pool[y], tmp);
          }
          return err;
       }
   }
   prng->fortuna.pool_idx = prng->fortuna.pool0_len = prng->fortuna.wd = 0;
   prng->fortuna.reset_cnt = 0;

   /* reset bufs */
   zeromem(prng->fortuna.K, 32);
   if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) {
      for (x = 0; x < FORTUNA_POOLS; x++) {
          sha256_done(&prng->fortuna.pool[x], tmp);
      }
      return err;
   }
   zeromem(prng->fortuna.IV, 16);
   
   LTC_MUTEX_INIT(&prng->fortuna.prng_lock)
   
   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 fortuna_add_entropy(const unsigned char *in, unsigned long inlen, prng_state *prng)
{
   unsigned char tmp[2];
   int           err;

   LTC_ARGCHK(in  != NULL);
   LTC_ARGCHK(prng != NULL);

   LTC_MUTEX_LOCK(&prng->fortuna.prng_lock);

   /* ensure inlen <= 32 */
   if (inlen > 32) {
      LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
      return CRYPT_INVALID_ARG;
   }

   /* add s || length(in) || in to pool[pool_idx] */
   tmp[0] = 0;
   tmp[1] = (unsigned char)inlen;
   if ((err = sha256_process(&prng->fortuna.pool[prng->fortuna.pool_idx], tmp, 2)) != CRYPT_OK) {
      LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
      return err;
   }
   if ((err = sha256_process(&prng->fortuna.pool[prng->fortuna.pool_idx], in, inlen)) != CRYPT_OK) {
      LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
      return err;
   }
   if (prng->fortuna.pool_idx == 0) {
      prng->fortuna.pool0_len += inlen;
   }
   if (++(prng->fortuna.pool_idx) == FORTUNA_POOLS) {
      prng->fortuna.pool_idx = 0;
   }

   LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
   return CRYPT_OK;
}

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

/**
  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 fortuna_read(unsigned char *out, unsigned long outlen, prng_state *prng)
{
   unsigned char tmp[16];
   int           err;
   unsigned long tlen;

   LTC_ARGCHK(out  != NULL);
   LTC_ARGCHK(prng != NULL);

   LTC_MUTEX_LOCK(&prng->fortuna.prng_lock);

   /* do we have to reseed? */
   if (++prng->fortuna.wd == FORTUNA_WD || prng->fortuna.pool0_len >= 64) {
      if ((err = fortuna_reseed(prng)) != CRYPT_OK) {
         LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
         return 0;
      }
   }

   /* now generate the blocks required */
   tlen = outlen;

   /* handle whole blocks without the extra XMEMCPY */
   while (outlen >= 16) {
      /* encrypt the IV and store it */
      rijndael_ecb_encrypt(prng->fortuna.IV, out, &prng->fortuna.skey);
      out += 16;
      outlen -= 16;
      fortuna_update_iv(prng);
   }

   /* left over bytes? */
   if (outlen > 0) {
      rijndael_ecb_encrypt(prng->fortuna.IV, tmp, &prng->fortuna.skey);
      XMEMCPY(out, tmp, outlen);
      fortuna_update_iv(prng);
   }
       
   /* generate new key */
   rijndael_ecb_encrypt(prng->fortuna.IV, prng->fortuna.K   , &prng->fortuna.skey); fortuna_update_iv(prng);
   rijndael_ecb_encrypt(prng->fortuna.IV, prng->fortuna.K+16, &prng->fortuna.skey); fortuna_update_iv(prng);
   if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) {
      LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
      return 0;
   }

#ifdef LTC_CLEAN_STACK
   zeromem(tmp, sizeof(tmp));
#endif
   LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
   return tlen;
}   

/**
  Terminate the PRNG
  @param prng   The PRNG to terminate
  @return CRYPT_OK if successful
*/  
int fortuna_done(prng_state *prng)
{
   int           err, x;
   unsigned char tmp[32];

   LTC_ARGCHK(prng != NULL);
   LTC_MUTEX_LOCK(&prng->fortuna.prng_lock);

   /* terminate all the hashes */
   for (x = 0; x < FORTUNA_POOLS; x++) {
       if ((err = sha256_done(&(prng->fortuna.pool[x]), tmp)) != CRYPT_OK) {
          LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
          return err; 
       }
   }
   /* call cipher done when we invent one ;-) */

#ifdef LTC_CLEAN_STACK
   zeromem(tmp, sizeof(tmp));
#endif

   LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
   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 fortuna_export(unsigned char *out, unsigned long *outlen, prng_state *prng)
{
   int         x, err;
   hash_state *md;

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

   LTC_MUTEX_LOCK(&prng->fortuna.prng_lock);

   /* we'll write bytes for s&g's */
   if (*outlen < 32*FORTUNA_POOLS) {
      LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
      *outlen = 32*FORTUNA_POOLS;
      return CRYPT_BUFFER_OVERFLOW;
   }

   md = XMALLOC(sizeof(hash_state));
   if (md == NULL) {
      LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
      return CRYPT_MEM;
   }

   /* to emit the state we copy each pool, terminate it then hash it again so 
    * an attacker who sees the state can't determine the current state of the PRNG 
    */   
   for (x = 0; x < FORTUNA_POOLS; x++) {
      /* copy the PRNG */
      XMEMCPY(md, &(prng->fortuna.pool[x]), sizeof(*md));

      /* terminate it */
      if ((err = sha256_done(md, out+x*32)) != CRYPT_OK) {
         goto LBL_ERR;
      }

      /* now hash it */
      if ((err = sha256_init(md)) != CRYPT_OK) {
         goto LBL_ERR;
      }
      if ((err = sha256_process(md, out+x*32, 32)) != CRYPT_OK) {
         goto LBL_ERR;
      }
      if ((err = sha256_done(md, out+x*32)) != CRYPT_OK) {
         goto LBL_ERR;
      }
   }
   *outlen = 32*FORTUNA_POOLS;
   err = CRYPT_OK;

LBL_ERR:
#ifdef LTC_CLEAN_STACK
   zeromem(md, sizeof(*md));
#endif
   XFREE(md);
   LTC_MUTEX_UNLOCK(&prng->fortuna.prng_lock);
   return err;
}
 
/**
  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 fortuna_import(const unsigned char *in, unsigned long inlen, prng_state *prng)
{
   int err, x;

   LTC_ARGCHK(in   != NULL);
   LTC_ARGCHK(prng != NULL);

   if (inlen != 32*FORTUNA_POOLS) {
      return CRYPT_INVALID_ARG;
   }

   if ((err = fortuna_start(prng)) != CRYPT_OK) {
      return err;
   }
   for (x = 0; x < FORTUNA_POOLS; x++) {
      if ((err = fortuna_add_entropy(in+x*32, 32, prng)) != CRYPT_OK) {
         return err;
      }
   }
   return err;
}

/**
  PRNG self-test
  @return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled
*/  
int fortuna_test(void)
{
#ifndef LTC_TEST
   return CRYPT_NOP;
#else
   int err;

   if ((err = sha256_test()) != CRYPT_OK) {
      return err;
   }
   return rijndael_test();
#endif
}

#endif


/* $Source: /cvs/libtom/libtomcrypt/src/prngs/fortuna.c,v $ */
/* $Revision: 1.12 $ */
/* $Date: 2006/12/04 21:34:03 $ */