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300 lines
7.1 KiB
C
300 lines
7.1 KiB
C
/* 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
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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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
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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/****************
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* This random number generator is modelled after the one described
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* in Peter Gutmann's Paper: "Software Generation of Practically
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* Strong Random Numbers".
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*/
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#include <config.h>
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#include <stdio.h>
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#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
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#define ADD_VALUE 0xa5a5a5a5a5a5a5a5
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#elif SIZEOF_UNSIGNED_LONG == 4
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#define ADD_VALUE 0xa5a5a5a5
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#else
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#error weird size for an unsigned long
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#endif
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struct cache {
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int len;
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int size;
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byte *buffer;
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};
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static int is_initialized;
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static struct cache cache[3];
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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 */
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static char *keypool; /* allocated size is POOLSIZE+BLOCKLEN */
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static size_t pool_readpos;
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static size_t pool_writepos;
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static int pool_filled;
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static int pool_balance;
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static int just_mixed;
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static int secure_alloc;
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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
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initialize()
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{
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/* The data buffer is allocated somewhat larger, so that
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* we can use this extra space (which is allocated in secure memory)
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* as a temporary hash buffer */
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rndpool = secure_alloc ? m_alloc_secure_clear(POOLSIZE+BLOCKLEN)
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: m_alloc_clear(POOLSIZE+BLOCKLEN);
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keypool = secure_alloc ? m_alloc_secure_clear(POOLSIZE+BLOCKLEN)
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: m_alloc_clear(POOLSIZE+BLOCKLEN);
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is_initialized = 1;
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}
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void
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secure_random_alloc()
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{
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secure_alloc = 1;
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}
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int
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quick_random_gen( int onoff )
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{
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int last = quick_test;
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if( onoff != -1 )
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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
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* for most usage, 2 is good for key generation stuff but may be very slow.
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*/
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void
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randomize_buffer( byte *buffer, size_t length, int level )
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{
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for( ; length; length-- )
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*buffer++ = get_random_byte(level);
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}
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byte
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get_random_byte( int level )
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{
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MASK_LEVEL(level);
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if( !cache[level].len ) {
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if( !is_initialized )
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initialize();
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if( !cache[level].buffer ) {
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cache[level].size = 100;
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cache[level].buffer = level && secure_alloc?
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m_alloc_secure( cache[level].size )
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: m_alloc( cache[level].size );
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}
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read_pool(cache[level].buffer, cache[level].size, level );
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cache[level].len = cache[level].size;
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}
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return cache[level].buffer[--cache[level].len];
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}
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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. This function does not use the
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* cache (will be removed in future). Note: The returned value is
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* rounded up to bytes.
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*/
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byte *
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get_random_bits( size_t nbits, int level, int secure )
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{
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byte *buf;
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size_t nbytes = (nbits+7)/8;
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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 );
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return buf;
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}
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/****************
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* Mix the pool
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*/
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static void
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mix_pool(byte *pool)
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{
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char *hashbuf = pool + POOLSIZE;
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char *p, *pend;
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int i, n;
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RMD160_CONTEXT md;
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rmd160_init( &md );
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#if DIGESTLEN != 20
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#error must have a digest length of 20 for ripe-md-160
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#endif
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/* loop over the pool */
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pend = pool + POOLSIZE;
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memcpy(hashbuf, pend - DIGESTLEN, DIGESTLEN );
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memcpy(hashbuf+DIGESTLEN, pool, BLOCKLEN-DIGESTLEN);
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rmd160_mixblock( &md, hashbuf);
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memcpy(pool, hashbuf, 20 );
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p = pool;
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for( n=1; n < POOLBLOCKS; n++ ) {
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memcpy(hashbuf, p, DIGESTLEN );
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p += DIGESTLEN;
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if( p+DIGESTLEN+BLOCKLEN < pend )
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memcpy(hashbuf+DIGESTLEN, p+DIGESTLEN, BLOCKLEN-DIGESTLEN);
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else {
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char *pp = p+DIGESTLEN;
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for(i=DIGESTLEN; i < BLOCKLEN; i++ ) {
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if( pp >= pend )
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pp = pool;
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hashbuf[i] = *pp++;
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}
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}
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rmd160_mixblock( &md, hashbuf);
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memcpy(p, hashbuf, 20 );
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}
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}
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static void
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read_pool( byte *buffer, size_t length, int level )
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{
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int i;
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ulong *sp, *dp;
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if( length >= POOLSIZE )
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BUG(); /* not allowed */
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/* for level 2 make sure that there is enough random in the pool */
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if( level == 2 && pool_balance < length ) {
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size_t needed;
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byte *p;
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if( pool_balance < 0 )
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pool_balance = 0;
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needed = length - pool_balance;
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if( needed > POOLSIZE )
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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);
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m_free(p);
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pool_balance += needed;
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}
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/* make sure the pool is filled */
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while( !pool_filled )
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random_poll();
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/* do always a fast random poll */
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fast_random_poll();
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if( !level ) { /* no need for cryptographic strong random */
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/* create a new pool */
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for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
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i < POOLWORDS; i++, dp++, sp++ )
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*dp = *sp + ADD_VALUE;
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/* must mix both pools */
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mix_pool(rndpool);
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mix_pool(keypool);
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memcpy( buffer, keypool, length );
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}
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else {
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/* mix the pool (if add_randomness() didn't it) */
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if( !just_mixed )
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mix_pool(rndpool);
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/* create a new pool */
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for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
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i < POOLWORDS; i++, dp++, sp++ )
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*dp = *sp + ADD_VALUE;
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/* and mix both pools */
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mix_pool(rndpool);
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mix_pool(keypool);
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/* read the required data
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* we use a readpoiter to read from a different postion each
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* time */
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while( length-- ) {
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*buffer++ = keypool[pool_readpos++];
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if( pool_readpos >= POOLSIZE )
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pool_readpos = 0;
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pool_balance--;
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}
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if( pool_balance < 0 )
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pool_balance = 0;
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/* and clear the keypool */
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memset( keypool, 0, POOLSIZE );
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}
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}
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/****************
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* Add LENGTH bytes of randomness from buffer to the pool.
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* source may be used to specify the randomeness source.
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*/
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void
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add_randomness( const void *buffer, size_t length, int source )
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{
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if( !is_initialized )
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initialize();
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while( length-- ) {
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rndpool[pool_writepos++] = *((byte*)buffer)++;
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if( pool_writepos >= POOLSIZE ) {
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if( source > 1 )
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pool_filled = 1;
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pool_writepos = 0;
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mix_pool(rndpool);
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just_mixed = !length;
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}
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}
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}
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