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gnupg/cipher/random.c

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/* random.c - random number generator
* Copyright (C) 1998 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* GnuPG is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* GnuPG is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
/****************
* This random number generator is modelled after the one described
* in Peter Gutmann's Paper: "Software Generation of Practically
* Strong Random Numbers".
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#ifdef HAVE_GETHRTIME
#include <sys/times.h>
#endif
#ifdef HAVE_GETTIMEOFDAY
#include <sys/times.h>
#endif
#ifdef HAVE_GETRUSAGE
#include <sys/resource.h>
#endif
#include "util.h"
#include "rmd.h"
#include "ttyio.h"
#include "i18n.h"
#include "random.h"
#include "rand-internal.h"
#include "dynload.h"
#ifndef RAND_MAX /* for SunOS */
#define RAND_MAX 32767
#endif
#if SIZEOF_UNSIGNED_LONG == 8
#define ADD_VALUE 0xa5a5a5a5a5a5a5a5
#elif SIZEOF_UNSIGNED_LONG == 4
#define ADD_VALUE 0xa5a5a5a5
#else
#error weird size for an unsigned long
#endif
#define BLOCKLEN 64 /* hash this amount of bytes */
#define DIGESTLEN 20 /* into a digest of this length (rmd160) */
/* poolblocks is the number of digests which make up the pool
* and poolsize must be a multiple of the digest length
* to make the AND operations faster, the size should also be
* a multiple of ulong
*/
#define POOLBLOCKS 30
#define POOLSIZE (POOLBLOCKS*DIGESTLEN)
#if (POOLSIZE % SIZEOF_UNSIGNED_LONG)
#error Please make sure that poolsize is a multiple of ulong
#endif
#define POOLWORDS (POOLSIZE / SIZEOF_UNSIGNED_LONG)
static int is_initialized;
#define MASK_LEVEL(a) do {if( a > 2 ) a = 2; else if( a < 0 ) a = 0; } while(0)
static char *rndpool; /* allocated size is POOLSIZE+BLOCKLEN */
static char *keypool; /* allocated size is POOLSIZE+BLOCKLEN */
static size_t pool_readpos;
static size_t pool_writepos;
static int pool_filled;
static int pool_balance;
static int just_mixed;
static int secure_alloc;
static int quick_test;
static int faked_rng;
static void read_pool( byte *buffer, size_t length, int level );
static void add_randomness( const void *buffer, size_t length, int source );
static void random_poll(void);
static void read_random_source( int requester, size_t length, int level);
static int gather_faked( void (*add)(const void*, size_t, int), int requester,
size_t length, int level );
static void
initialize()
{
/* The data buffer is allocated somewhat larger, so that
* we can use this extra space (which is allocated in secure memory)
* as a temporary hash buffer */
rndpool = secure_alloc ? m_alloc_secure_clear(POOLSIZE+BLOCKLEN)
: m_alloc_clear(POOLSIZE+BLOCKLEN);
keypool = secure_alloc ? m_alloc_secure_clear(POOLSIZE+BLOCKLEN)
: m_alloc_clear(POOLSIZE+BLOCKLEN);
is_initialized = 1;
cipher_modules_constructor();
}
void
secure_random_alloc()
{
secure_alloc = 1;
}
int
quick_random_gen( int onoff )
{
int last;
read_random_source(0,0,0); /* init */
last = quick_test;
if( onoff != -1 )
quick_test = onoff;
return faked_rng? 1 : last;
}
/****************
* Fill the buffer with LENGTH bytes of cryptographically strong
* random bytes. level 0 is not very strong, 1 is strong enough
* for most usage, 2 is good for key generation stuff but may be very slow.
*/
void
randomize_buffer( byte *buffer, size_t length, int level )
{
char *p = get_random_bits( length*8, level, m_is_secure(buffer) );
memcpy( buffer, p, length );
m_free(p);
}
int
random_is_faked()
{
if( !is_initialized )
initialize();
return faked_rng || quick_test;
}
/****************
* Return a pointer to a randomized buffer of level 0 and LENGTH bits
* caller must free the buffer.
* Note: The returned value is rounded up to bytes.
*/
byte *
get_random_bits( size_t nbits, int level, int secure )
{
byte *buf;
size_t nbytes = (nbits+7)/8;
if( quick_test && level > 1 )
level = 1;
MASK_LEVEL(level);
buf = secure && secure_alloc ? m_alloc_secure( nbytes ) : m_alloc( nbytes );
read_pool( buf, nbytes, level );
return buf;
}
/****************
* Mix the pool
*/
static void
mix_pool(byte *pool)
{
char *hashbuf = pool + POOLSIZE;
char *p, *pend;
int i, n;
RMD160_CONTEXT md;
rmd160_init( &md );
#if DIGESTLEN != 20
#error must have a digest length of 20 for ripe-md-160
#endif
/* loop over the pool */
pend = pool + POOLSIZE;
memcpy(hashbuf, pend - DIGESTLEN, DIGESTLEN );
memcpy(hashbuf+DIGESTLEN, pool, BLOCKLEN-DIGESTLEN);
rmd160_mixblock( &md, hashbuf);
memcpy(pool, hashbuf, 20 );
p = pool;
for( n=1; n < POOLBLOCKS; n++ ) {
memcpy(hashbuf, p, DIGESTLEN );
p += DIGESTLEN;
if( p+DIGESTLEN+BLOCKLEN < pend )
memcpy(hashbuf+DIGESTLEN, p+DIGESTLEN, BLOCKLEN-DIGESTLEN);
else {
char *pp = p+DIGESTLEN;
for(i=DIGESTLEN; i < BLOCKLEN; i++ ) {
if( pp >= pend )
pp = pool;
hashbuf[i] = *pp++;
}
}
rmd160_mixblock( &md, hashbuf);
memcpy(p, hashbuf, 20 );
}
}
static void
read_pool( byte *buffer, size_t length, int level )
{
int i;
ulong *sp, *dp;
if( length >= POOLSIZE )
BUG(); /* not allowed */
/* for level 2 make sure that there is enough random in the pool */
if( level == 2 && pool_balance < length ) {
size_t needed;
if( pool_balance < 0 )
pool_balance = 0;
needed = length - pool_balance;
if( needed > POOLSIZE )
BUG();
read_random_source( 3, needed, 2 );
pool_balance += needed;
}
/* make sure the pool is filled */
while( !pool_filled )
random_poll();
/* do always a fast random poll */
fast_random_poll();
if( !level ) { /* no need for cryptographic strong random */
/* create a new pool */
for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
i < POOLWORDS; i++, dp++, sp++ )
*dp = *sp + ADD_VALUE;
/* must mix both pools */
mix_pool(rndpool);
mix_pool(keypool);
memcpy( buffer, keypool, length );
}
else {
/* mix the pool (if add_randomness() didn't it) */
if( !just_mixed )
mix_pool(rndpool);
/* create a new pool */
for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
i < POOLWORDS; i++, dp++, sp++ )
*dp = *sp + ADD_VALUE;
/* and mix both pools */
mix_pool(rndpool);
mix_pool(keypool);
/* read the required data
* we use a readpoiter to read from a different postion each
* time */
while( length-- ) {
*buffer++ = keypool[pool_readpos++];
if( pool_readpos >= POOLSIZE )
pool_readpos = 0;
pool_balance--;
}
if( pool_balance < 0 )
pool_balance = 0;
/* and clear the keypool */
memset( keypool, 0, POOLSIZE );
}
}
/****************
* Add LENGTH bytes of randomness from buffer to the pool.
* source may be used to specify the randomness source.
*/
static void
add_randomness( const void *buffer, size_t length, int source )
{
if( !is_initialized )
initialize();
while( length-- ) {
rndpool[pool_writepos++] = *((byte*)buffer)++;
if( pool_writepos >= POOLSIZE ) {
if( source > 1 )
pool_filled = 1;
pool_writepos = 0;
mix_pool(rndpool);
just_mixed = !length;
}
}
}
static void
random_poll()
{
read_random_source( 2, POOLSIZE/5, 1 );
}
void
fast_random_poll()
{
static void (*fnc)( void (*)(const void*, size_t, int), int) = NULL;
static int initialized = 0;
if( !initialized ) {
if( !is_initialized )
initialize();
initialized = 1;
fnc = dynload_getfnc_fast_random_poll();
}
if( fnc ) {
(*fnc)( add_randomness, 1 );
return;
}
/* fall back to the generic function */
#if HAVE_GETHRTIME
{ hrtime_t tv;
tv = gethrtime();
add_randomness( &tv, sizeof(tv), 1 );
}
#elif HAVE_GETTIMEOFDAY
{ struct timeval tv;
if( gettimeofday( &tv, NULL ) )
BUG();
add_randomness( &tv.tv_sec, sizeof(tv.tv_sec), 1 );
add_randomness( &tv.tv_usec, sizeof(tv.tv_usec), 1 );
}
#else /* use times */
{ struct tms buf;
times( &buf );
add_randomness( &buf, sizeof buf, 1 );
}
#endif
#ifdef HAVE_GETRUSAGE
{ struct rusage buf;
if( getrusage( RUSAGE_SELF, &buf ) )
BUG();
add_randomness( &buf, sizeof buf, 1 );
memset( &buf, 0, sizeof buf );
}
#endif
}
static void
read_random_source( int requester, size_t length, int level )
{
static int (*fnc)(void (*)(const void*, size_t, int), int,
size_t, int) = NULL;
if( !fnc ) {
if( !is_initialized )
initialize();
fnc = dynload_getfnc_gather_random();
if( !fnc ) {
faked_rng = 1;
fnc = gather_faked;
}
if( !requester && !length && !level )
return; /* init only */
}
if( (*fnc)( add_randomness, requester, length, level ) < 0 )
log_fatal("No way to gather entropy for the RNG\n");
}
static int
gather_faked( void (*add)(const void*, size_t, int), int requester,
size_t length, int level )
{
static int initialized=0;
size_t n;
char *buffer, *p;
if( !initialized ) {
log_info(_("WARNING: using insecure random number generator!!\n"));
tty_printf(_("The random number generator is only a kludge to let\n"
"it run - it is in no way a strong RNG!\n\n"
"DON'T USE ANY DATA GENERATED BY THIS PROGRAM!!\n\n"));
initialized=1;
#ifdef HAVE_RAND
srand(make_timestamp()*getpid());
#else
srandom(make_timestamp()*getpid());
#endif
}
p = buffer = m_alloc( length );
n = length;
#ifdef HAVE_RAND
while( n-- )
*p++ = ((unsigned)(1 + (int) (256.0*rand()/(RAND_MAX+1.0)))-1);
#else
while( n-- )
*p++ = ((unsigned)(1 + (int) (256.0*random()/(RAND_MAX+1.0)))-1);
#endif
add_randomness( buffer, length, requester );
m_free(buffer);
return 0; /* okay */
}
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