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gnupg/cipher/random.c

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/* random.c - random number generator
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* Copyright (C) 1998 Free Software Foundation, Inc.
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*
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* This file is part of GNUPG.
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*
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* GNUPG is free software; you can redistribute it and/or modify
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* 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.
*
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* GNUPG is distributed in the hope that it will be useful,
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* 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
*/
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/****************
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* This random number generator is modelled after the one described
* in Peter Gutmann's Paper: "Software Generation of Practically
* Strong Random Numbers".
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*/
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#include <config.h>
#include <stdio.h>
#include <stdlib.h>
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#include <assert.h>
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#include <errno.h>
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#include <string.h>
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#include "util.h"
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#include "rmd.h"
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#include "ttyio.h"
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#include "i18n.h"
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#include "rand-internal.h"
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#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
static int is_initialized;
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#define MASK_LEVEL(a) do {if( a > 2 ) a = 2; else if( a < 0 ) a = 0; } while(0)
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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;
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static int pool_balance;
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static int just_mixed;
static int secure_alloc;
static int quick_test;
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static void read_pool( byte *buffer, size_t length, int level );
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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;
}
void
secure_random_alloc()
{
secure_alloc = 1;
}
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int
quick_random_gen( int onoff )
{
int last = quick_test;
if( onoff != -1 )
quick_test = onoff;
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#ifdef USE_RAND_DUMMY
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last = 1; /* insecure RNG */
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#endif
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return last;
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}
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/****************
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* Fill the buffer with LENGTH bytes of cryptographically strong
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* 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 )
{
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char *p = get_random_bits( length*8, level, m_is_secure(buffer) );
memcpy( buffer, p, length );
m_free(p);
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}
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/****************
* Return a pointer to a randomized buffer of level 0 and LENGTH bits
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* caller must free the buffer.
* Note: The returned value is rounded up to bytes.
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*/
byte *
get_random_bits( size_t nbits, int level, int secure )
{
byte *buf;
size_t nbytes = (nbits+7)/8;
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if( quick_test && level > 1 )
level = 1;
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MASK_LEVEL(level);
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buf = secure && secure_alloc ? m_alloc_secure( nbytes ) : m_alloc( nbytes );
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read_pool( buf, nbytes, level );
return buf;
}
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/****************
* 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 */
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/* for level 2 make sure that there is enough random in the pool */
if( level == 2 && pool_balance < length ) {
size_t needed;
byte *p;
if( pool_balance < 0 )
pool_balance = 0;
needed = length - pool_balance;
if( needed > POOLSIZE )
BUG();
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p = secure_alloc ? m_alloc_secure( needed ) : m_alloc(needed);
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read_random_source( p, needed, 2 ); /* read /dev/random */
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add_randomness( p, needed, 3);
m_free(p);
pool_balance += needed;
}
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/* make sure the pool is filled */
while( !pool_filled )
random_poll();
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/* do always a fast random poll */
fast_random_poll();
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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 */
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mix_pool(rndpool);
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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 );
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}
}
/****************
* Add LENGTH bytes of randomness from buffer to the pool.
* source may be used to specify the randomeness source.
*/
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 ) {
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if( source > 1 )
pool_filled = 1;
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pool_writepos = 0;
mix_pool(rndpool);
just_mixed = !length;
}
}
}