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/*
* File: rng.cc
* Summary: Random number generator wrapping.
*/
#include "AppHdr.h"
#include "rng.h"
#include "mt19937ar.h"
#ifdef USE_MORE_SECURE_SEED
// for times()
#include <sys/times.h>
// for getpid()
#include <sys/types.h>
#include <unistd.h>
#endif
#ifdef MORE_HARDENED_PRNG
#include "sha256.h"
#endif
void seed_rng(unsigned long* seed_key, size_t num_keys)
{
// MT19937 -- see mt19937ar.cc for details/licence
init_by_array(seed_key, num_keys);
// Reset the sha256 generator to get predictable random numbers in case
// of a saved rng state.
#ifdef MORE_HARDENED_PRNG
reset_sha256_state();
#endif
// for std::random_shuffle()
srand(seed_key[0]);
}
void seed_rng(long seed)
{
// MT19937 -- see mt19937ar.cc for details/licence
init_genrand(seed);
// Reset the sha256 generator to get predictable random numbers in case
// of a saved rng state.
#ifdef MORE_HARDENED_PRNG
reset_sha256_state();
#endif
// for std::random_shuffle()
srand(seed);
}
void seed_rng()
{
unsigned long seed = time( NULL );
#ifdef USE_MORE_SECURE_SEED
/* (at least) 256-bit wide seed */
unsigned long seed_key[8];
struct tms buf;
seed += times( &buf ) + getpid();
seed_key[0] = seed;
/* Try opening from various system provided (hopefully) CSPRNGs */
FILE* seed_f = fopen("/dev/urandom", "rb");
if (!seed_f)
seed_f = fopen("/dev/random", "rb");
if (!seed_f)
seed_f = fopen("/dev/srandom", "rb");
if (!seed_f)
seed_f = fopen("/dev/arandom", "rb");
if (seed_f)
{
fread(&seed_key[1], sizeof(unsigned long), 7, seed_f);
fclose(seed_f);
}
seed_rng(seed_key, 8);
#else
seed_rng(seed);
#endif
}
// MT19937 -- see mt19937ar.cc for details
unsigned long random_int( void )
{
#ifndef MORE_HARDENED_PRNG
return (genrand_int32());
#else
return (sha256_genrand());
#endif
}
void push_rng_state()
{
#ifndef MORE_HARDENED_PRNG
push_mt_state();
#else
push_sha256_state();
#endif
}
void pop_rng_state()
{
#ifndef MORE_HARDENED_PRNG
pop_mt_state();
#else
pop_sha256_state();
#endif
}
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